Untapped Potential: Opportunities and Challengesfor Sustainable Bioenergy Production from MarginalLands in the Northeast USA

Cathelijne R. Stoof & Brian K. Richards & Peter B. Woodbury & Eric S. Fabio &

Alice R. Brumbach & Jerry Cherney & Srabani Das & Larry Geohring & Julie Hansen &

Josh Hornesky & Hilary Mayton & Cedric Mason & Gerry Ruestow & Lawrence B. Smart &Timothy A. Volk & Tammo S. Steenhuis

# Springer Science+Business Media New York 2014

Abstract Over two million hectares of marginal land in theNortheast USA no longer used for agriculture may be suitableand available for production of second-generation cellulosicbioenergy crops, offering the potential for increased regionalbioenergy production without competing with food produc-tion on prime farmland. Current yields of perennial bioenergygrasses and short-rotation woody crops range from 2.3 to 17.4and 4.5 to 15.5Mg/ha, respectively, and there is great potentialfor increased yields. Regional advantages for bioenergy de-velopment include abundant water resources, close proximitybetween production and markets, and compatibility ofbioenergy cropping systems with existing agriculture. AsNewYork and NewEngland (a subset of the Northeast region)

account for ~85 % of the nation’s heating oil consumption,production of bioheat, biopower, and combined heat andpower could substantially reduce the region’s dependence onimported petroleum. While numerous grassroots efforts areunderway in the region across supply chains, bioenergydevelopment faces several challenges and unknowns interms of environmental impact, production, yields, socio-economics, and policy. We explore the opportunities forsecond-generation bioenergy production on the unusedmarginal lands of the Northeast USA and discuss thechallenges to be addressed to promote sustainablebioenergy production on the region’s underutilized mar-ginal land base.

C. R. Stoof (*) : B. K. Richards (*) : S. Das : L. Geohring :C. Mason : T. S. SteenhuisDepartment of Biological and Environmental Engineering,Riley-Robb Hall, Cornell University, Ithaca, NY 14853, USAe-mail: cathelijne.stoof@cornell.edue-mail: bkr2@cornell.edu

P. B. Woodbury : J. CherneySoil and Crop Sciences Section, School of IntegrativePlant Science, Bradfield Hall, Cornell University,Ithaca, NY 14853, USA

E. S. Fabio : L. B. SmartHorticulture Section, School of Integrative Plant Science, CornellUniversity, New York State Agricultural Experiment Station,Geneva, NY 14456, USA

A. R. BrumbachNewYork BioenergyAssociation, 47 Van Alstyne Drive, Rensselaer,NY 12144, USA

J. Hansen :H. MaytonPlant Breeding and Genetics Section, School of Integrative PlantScience, Cornell University, Ithaca, NY 14853, USA

J. HorneskyUnited States Department of Agriculture-Natural ResourcesConservation Service, PO Box 1140, Mexico, NY, USA

H. MaytonCenter for Teaching Excellence, Cornell University, Ithaca,NY 14853, USA

G. RuestowFermata Consulting, 1556 Dunshee Rd, Unadilla, NY 13849, USA

T. A. VolkDepartment of Forest and Natural Resources Management, StateUniversity of New York, College of Environmental Science andForestry, 346 Illick Hall, Syracuse, NY 13210, USA

Present Address:C. R. StoofSoil Geography and Landscape Group, Wageningen University,P.O. box 47, 6700 AAWageningen, The Netherlandse-mail: cathelijne.stoof@wur.nl

Bioenerg. Res.DOI 10.1007/s12155-014-9515-8

Keyword Second-generation bioenergy feedstocks .

Marginal land . Perennial grass . Short-rotation woody crops .

Impacts . Production . Policy . Northeast USA

Introduction

Sustainable bioenergy systems can address a number of crucialenvironmental issues and enhance national security by provid-ing renewable domestic energy production alternatives to fossilfuels and specifically imported petroleum.While focus has longbeen given to first-generation annual energy crops such asmaize(Zea mays) and soybean (Glycine max) that require primefarmland, there is increasing interest in second-generation pe-rennial crops such as switchgrass (Panicum virgatum),miscanthus (Miscanthus×giganteus), and willow (Salix spp.)that can also be grown onmoremarginal soils and thereby avoidfood vs. fuel competition for prime farmland [1, 2].Development of a large bioenergy economy in the USA willrequire dramatically increasing sustainable biomass feedstockproduction, for which production forecasts cite the use of mil-lions of hectares of marginal lands [1, 3–8]. Specifically citedare agricultural lands that have fallen out of production be-cause they are unable to support sustainable economic returnsin conventional agriculture. Abundant land and water re-sources make the Northeast USA (Fig. 1) particularly suitedfor second-generation bioenergy feedstock production. Theregion’s high energy demand and its reliance on fuel oil forheating underline an economic and environmental potentialand necessity for local production of alternative renewableenergy. However, this potential remains largely untapped be-cause of a number of challenges related to bioenergy feed-stock production, conversion, and policy that must be ad-dressed before significant expansion can occur.

High energy demand is a distinctive feature of the NortheastUSA because of high population (18% of the USA’s population

in 5 % of its land area [9]), cold winters, and many poorlyinsulated houses. Because natural gas networks primarily servemore densely populated areas, nearly 30 % of New York Stateand New England’s homes are heated with fuel oil [10], ac-counting for ~85 % of the entire nation’s heating oil consump-tion [11]. Initiatives are underway to offset a portion of thisdemand with thermal biomass (bioheat) or combined heat andpower (CHP) applications [12], thereby directly replacingimported carbon-emitting heating oil. Bioheat initiatives in theregion were initially driven by local advocates, researchers, andinnovators but have recently received state-level interest [13,14]. Bioenergy has significant potential to contribute a fargreater percentage of the future of Northeast USA energy needsthan it does at present. For example in New York State, only12 % of energy consumed in 2010 was from in-state resources[15], roughly equating to 8 % of expenditures ($4.8 billion).Agricultural bioenergy production can therefore not only reducepetroleum demand but also do so in a way that localizes energyproduction, which benefits rural, local, and national economiesby providing a renewable income source [e.g., 12] in place ofwhat now constitutes a capital export. Although expansion iscurrently hampered by factors discussed below, the region’senergy importation indicates potential for the development oflocal bioenergy supply chains. The relatively close proximitybetween production regions and local markets (pellet mills,biofuels refineries, pellet plants, and population centers) andexport markets (deepwater ports with pellet loading capabili-ty) is an economic advantage because transportation is costlyfor bioenergy feedstocks and products [16]. Replacing heatingoil by regionally produced densified switchgrass could pro-vide benefits of $2.3 to 3.9 billion annually [17].

The environmental impact of second-generation cellulosicperennial crops is widely considered less than that of annualfirst-generation bioenergy crops (Table 1), with benefits includ-ing emissions neutrality, significant ecosystem services, andlong-term soil resource improvement [18, 19]. Underutilized

Fig. 1 Map of the United States of America (a) with the Northeasternstates shaded in gray, and a detailed map of these Northeastern States (b),including the States of New York (NY), Pennsylvania (PA), New Jersey

(NJ), Connecticut (CT), Rhode Island (RI), Massachusetts (MA), NewHampshire (NH), Vermont (VT), and Maine (ME)

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marginal lands are an increasingly important land base forbioenergy feedstock production and are the primary land baseavailable in the Northeast USA. As such, there is a need toestimate how much land is suitable and available in the regionand to assess the productivity and impacts of second-generation feedstocks on these marginal soils.

Here, we discuss the opportunities and challenges forbioenergy (Box 1) feedstock production from marginal landsin the Northeast US, with examples drawn primarily from ourexperience centered in New York State. We first review thefavorable climatic conditions in the region and analyze theorigin and availability of the marginal land resource base. Wethen explore the main challenges for further development ofthis resource in the region, focusing on farming, production,and policy issues, particularly from a near-term, low-cost, andlow-input production and utilization context.

Box 1. Definitions

Definitions of “biomass,” “bioenergy,” and “biofuel” vary betweencountries and legislative bodies [20–23]. US federal policy has focusedalmost exclusively on liquid biofuels [6] to the frequent exclusion ofother biomass energy pathways including combustion-based bioheatand combined heat and power. Since these latter forms of energy arerelevant in the Northeast context, we use the term “bioenergy” in thispaper more generally as energy that is released by the direct or post-conversion combustion of biomass or its products. Energy productsinclude, but are not limited to, bioheat, biopower, combined heat andpower, and an array of liquid biofuels, such as syngas, bio-oil, andethanol.

Applied to land resources, the term “marginal” is foremost an economiccondition with biophysical causes [24]. It refers to land at themargins ofproduction, where potential returns are at a breakeven point withproduction costs (in contrast to submarginal land where production is

Box 1. Definitionsunprofitable). That marginal is an economic termmeans that it is definedby the local economic context, which means that the specifics ofmarginality will vary regionally and temporally [25, 26]. As such, cleardefinition of the cause(s) of marginality in a particular context isimportant [26, 27].

Favorable Climate

In contrast to many other regions in the USA, water resourcesare abundant in most of the Northeast. Annual precipitation inmost of the region varies between 760 and 1,520 mm [28] andis generally well distributed over the year. Mean annual tem-peratures range from 1.7 to 15.6 °C [28], a temperature rangethat is comparable to many of the corn- and wheat-producingareas of the Midwestern USA. Summers in the Northeast arewarm and winters are cold, with precipitation typically occur-ring as snow. Because of the abundance of natural rainfall,crop and biomass yields are generally not strongly limited byavailability of water, especially in comparison to drier regionsof the USA.

Marginal Land Available

Decades of abandonment of agricultural lands in theNortheast USA (Box 2) created large areals of scrub andwoodlands (described presciently as the “New Forests” byConklin [29]), as well as fallow lands that have beenoccasionally mowed to prevent shrub and tree growth.

Table 1 Differences between first- and second-generation bioenergy feedstocks

First-generation Second-generation

Primary crops Annuals: corn, soybean Perennials: grasses, willow

Component of interest Grain (also corn stover) Cellulosic/whole plant

Marginal soil adaptation Limiteda Moderate to gooda, b

Net energy yield Lowc (just over 1:1) Highb, c

Food vs. fuel conflict High when grown on prime farmlandd Low when grown on abandoned, marginal landd

Required inputs(tillage/fertilizer/pesticide)

Higha Low to moderatea, b

Potential impacts(nutrient loss, erosion)

Moderate to higha Lowa, b

Potential emissions Moderate to higha Low to moderatea, b

Soil quality trend(including C accumulation)

Negative/flate unless aggressively managed Depends on prior land use (see Table 3)

a Blanco-Canqui [18]b Limited researchc de Vries et al. [147]d Valentine et al. [2]e Stockmann et al. [48]

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Reforested portions now contribute to the region’s substan-tial woody biomass resource base, while the remainder ispotentially usable for production of bioenergy feedstockssuch as switchgrass and short-rotation willow. These aban-doned marginal lands (Box 1) are available without com-peting for food production.

To facilitate accurate estimation of the potential for regionalfeedstock production, we quantified the amount of land that isavailable and suitable for perennial bioenergy feedstock pro-duction in the region (Box 3). This geospatial analysis sug-gests that nearly 2.5 million ha might be available and suitablefor use throughout seven Northeastern states (Table 2),representing 6 % of the total land area in this region. Thisestimate is an upper bound as actual land availability is addi-tionally constrained by wet soils, accessibility, distance tomarkets, and competing landowner goals (Box 3). Despitethese constraints, the land base potentially usable forbioenergy feedstock production without competing with cur-rent agricultural production is substantial.

Box 2. Causes of land abandonment

Underutilized land resources in the region are significant due to historicalabandonment of former agricultural lands. Causes of thisabandonment were manifold, but primary among them weredegradation of soil quality coupled with the opening of moreproductive croplands to the west. In the 1800s, New York State wasthe bread basket for the USA, with canal systems for shipping grain tothe cities of the eastern seaboard. But in the 1900s, productiondeclined due to the loss of fertile topsoil from many hillside soils,which became too shallow to hold sufficient water during the drysummers and could not produce profitable yields even with addedfertilizers. Many valley bottom lands were too wet for spring plantingand/or fall harvesting. Attractive off-farm labor opportunities andprice competition from better-adapted regions (as well as from primefarmlands in the region) made farming poorer soils a less attractiveoption. The cumulative impact has been a century-long decline in landin farms. Those lands that were not mowed to retard successionalshrub and tree growth reverted to woodlands (the “New Forests” citedby Conklin [29]) which now contribute to the region’s substantialwoody biomass resource base. Lands that were at least occasionally

Box 2. Causes of land abandonmentmowed have remained open and thereby potentially usable for pe-rennial bioenergy production.

Box 3. Quantification of the land available in the US Northeast

We quantified the amount of land available in the region from the amountof land that was cleared for agriculture in the past, but that is notcurrently producing a crop such as hay, nor being used for pasture onfarms. This land is currently in various types of herbaceous vegetationcover. This analysis differs from previous ones that often focused oncurrent agricultural land [6] because it focuses on lands that are notcurrently in agricultural production, which we consider the primaryland base for bioenergy in the region.

Which lands are suitable?

The area of land that is available for bioenergy feedstock production isfirst and foremost determined by their suitability. To determinesuitability, we made the following assumptions. First, forest land willstay forests—we do not consider conversion of any forest lands toproduction of agricultural bioenergy feedstocks. (It should be notedthat there is great potential for bioenergy feedstock production fromthese existing forests, including branches and tops of commercialspecies as well as species not suitable for wood products, but that topicis beyond the scope of this analysis). Second, row crop lands willremain in row crops and are not considered for perennial feedstockproduction to avoid competition with food production. Lands currentlyin herbaceous cover (pasture, hay, grassland, crop land, shrub, andscrub land) will remain in herbaceous cover, but these could includebioenergy crops. Not all lands in herbaceous cover are practical toaccess for harvest because of size, slope, or ownership. We thereforeremoved (1) fields <2 ha as these are not suitable for large-scalecommercial feedstock production operations; (2) areas with a slope>15 % as these are hard to access by farm machinery; and (3) lands infederal ownership and State-protected lands.

How much land is available?

After classifying land suitability, we calculated the amount of land thatcould be available in coming decades for dedicated grasses and willowbioenergy feedstocks in three steps. First, the total amount of land inherbaceous cover was determined through geospatial analysis of thesum of the crop, pasture, and grass and hay land from the NationalLand Cover Database [30]. Using geospatial modeling, we thenestimated the fraction of this land that would be biophysically suitablefor feedstock production (as outlined above). Finally, data from theCensus of Agriculture [31] were used to remove land currently inagricultural production for each county throughout the region.

Upper limit of availability

It is important to note that the areal we hereby quantified to be available andsuitable for bioenergy production in the region is an upper bound ofactual land availability for a number of reasons. Most of these lands arecurrently out of production for a good reason, as their biophysicalcharacteristics can be very challenging for farming (as discussed below).Portions of the available land base may therefore be too wet or haveother limitations making them not suitable for commercial production ofbioenergy feedstocks. Location is another potential issue: some of thisland may not be accessible by road (particularly in Maine where landsare scattered in remote regions), and some of this landmay be too remotefrom markets or be too sparse in a local region to support commercialbioenergy feedstock production. Current land usemay also be a concern,as some land may be in use for crops that are not reported in the Censusof Agriculture, such as the case for home gardens and horses (if not onfarms). Lastly, landowners have many goals for their land, andproduction of bioenergy feedstocks will not always be compatible withother uses. For example, based on surveys of landowners and on detailed

Table 2 Amount of potentially suitable and available marginal land forseven states in the Northeast USA, expressed as total area (ha) and asportion of the total land in each State (%). These estimates are based on anumber of assumptions (Box 3) and are an upper limit

US state Available land (103 ha) % of State

New York (NY) 1,015 8.3

Pennsylvania (PA) 838 7.2

Maine (ME) 356 4.5

Vermont (VT) 125 5.2

New Hampshire (NH) 38 1.6

Pennsylvania (PA) 838 7.2

Massachusetts (MA) 125 5.2

Total 2,430 6.1

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Box 3. Quantification of the land available in the US Northeastanalysis for NewYork State, only half of landowners might be interestedin harvesting biomass from their lands [32]. This fraction varies withpopulation density [32] and other factors, and further research is requiredto better understand landowner’s values and interest in producingbiomass feedstocks. Finally, attitudes may change as biomass feedstockmarketing opportunities develop throughout the region.

Land Quality

Marginal lands are available because of one or more userestrictions (slope, elevation, depth, texture, rockiness, inter-nal drainage, fertility, and/or remoteness) that preclude profit-able production of conventional agricultural crops. Many ofthese characteristics directly affect agricultural suitability viatheir effects on soil hydrology. Most marginal agriculturalsoils in the region (e.g., Fig. 2) are subject to at least seasonalsaturation or near-saturation because they are characterized byrelatively permeable surface soils atop shallow restrictivelayers (dense basal glacial till, fragipans, or shallow bedrock).When precipitation and/or snowmelt exceeds evapotranspira-tion, perched water tables develop over these impermeablelayers. In sloping soils, this produces significant lateral inter-flow that saturates downslope depressions and areas whererestrictive layers are especially shallow [33–35], complicatingmanagement and reducing trafficability [36]. These hydrolog-ic characteristics furthermore contribute to the marginality of

many soils in the region due to these adverse effects on cropgrowth. Spring wetness can cause yield losses via delayedplanting and soil-borne diseases associated with cool, wetsoils [37]. Late season wetness causes problems with fieldoperations and can lead to yield losses. Paradoxically, highseasonal perched water tables in the spring are also associatedwith summer drought susceptibility, as the dense soil layersreduce effective rooting depth and thus limit soil water avail-ability. Soils prone to saturation are also likely to generaterunoff and thus transport nutrients and pesticides off-site [35].Such soils are typically closely connected hydrologically tosurface water bodies; thus, any potential impacts frombioenergy feedstock production on water quality need to becarefully assessed and mitigated as bioenergy feedstock pro-duction expands in the region.

Wetness is not the only reason for soils to bemarginal in theNortheast. Many hillslope soils atop shallow restrictive layersas well as sandy “excessively drained” soils are marginal dueto their inadequate water-holding capacity and consequentsummer moisture deficits, and are often consigned topasture/forage production. Significant erosion from poor priormanagement (including growing poorly suited annual crops)may also relegate soils to marginal status due to loss of soildepth, organic matter, and native fertility.

These factors that render soils at best marginally suited forannual crops are of lesser consequence for perennialbioenergy feedstocks such as warm-season grasses andshort-rotation woody crops. These perennials have deeperand more extensive root systems, require far fewer field ma-chinery operations, and have longer time windows for fieldoperations such as fertilizing and harvesting.

Environmental Impact

Soil Health, Carbon Sequestration, and Water Quality

Perennial bioenergy crops are often regarded to have majorbenefits for the environment, such as increased soil health andcarbon sequestration, reduced water quality impacts associatedwith reduced erosion and lower fertilizer use, reduced (at pres-ent) pesticide and herbicide requirements, and improved biodi-versity [18, 38, 39]. Naturally, the relative environmental impactof land use conversion to perennial bioenergy feedstock produc-tion depends on the preexisting land use (Table 3). Whenconverting land in annual row crop production to perennialbioenergy grasses and short-rotation woody crops, benefits areindeed manifold [1, 4, 18, 39–45]. Perennials have longergrowing seasons and deeper rooting depth than annuals andtherefore return more aboveground and belowground residueto the soil, increasing carbon accumulation [46, 47]. However,the environmental impact of conversion from pasture, fallow, orabandoned land is not so clear. Initial land clearing and tillage

Fig. 2 A harvested switchgrass field on a wetness-prone marginal soilnear Ithaca, NY

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required for the establishment of perennial feedstocks releasescarbon from aboveground and soil C pools [48], incurring a“carbon debt” [49] that is repaid as belowground carbon accu-mulates but which can take decades or even centuries to recover[50]. Hence, conversion of fallow land for perennial bioenergycrops cannot be assumed to cause substantial increases in carbonsequestration [32, 51]. The same applies to erosion and waterquality: since plant cover is already high in fallow land, initialland clearing and tillage can only increase erosion risk (albeitbriefly), particularly on sloping land. Fertilizer and initialherbicice applications will also be higher than for fallow land,with potential impacts on denitrification (see below) and bothsurface and groundwater quality as agrichemicals find their wayto water bodies through surface runoff and leaching. Erosionimpacts are greatest at the time of conversion and decrease withthe establishment of a full cover, and may be mitigated whenperennial grasses are established with no-till methods, which arealso considered beneficial for mitigating other adverse effects ofconventional tillage, such as CO2 emissions, and decreased soilstructure and infiltration [18, 48, 52]. Current challenges of no-till establishment include the availability of both appropriateequipment and registered herbicides to manage weed competi-tion. While pesticide application is likely limited to the initialestablishment phase, any effects of regular fertilization willcontinue as long as the stand is activelymanaged. These impactsneed to be accounted for, as even low impacts on an areal basiscan still aggregate into considerable impacts on a regional basis.

N2O and CH4 Emissions

Long-term sustainability of renewable bioenergy productionsystems requires long-term GHG emissions neutrality. Similarto soil and water quality considerations, the net impact ofmarginal land bioenergy feedstock production on N2O andCH4 emissions depends strongly on prior land use.Displacement of annual crops with perennial crops would sub-stantially reduce N2O emissions, due to reduced fertilizer Napplication and hence reduced emission potential. Although itis beyond the scope of this review, it is important to recognizethat displacement of first-generation food/feed production in one

place may trigger indirect (offsite) land use changes and conse-quent offsite emission effects that should be accounted for whendetermining net emission impacts. In cases where previouslyidle/fallow lands are put into perennial bioenergy feedstockproduction, emissions of both CO2 (due to tillage [50]) andN2O (due to fertilization [53], albeit at low rates) will bothincrease. However, a wider systems view typically shows a netreduction in the emission of greenhouse gases as emissionsassociated with the production and use of fossil fuels are offset[16, 54, 55]. Yet, several factors remain poorly defined in thecases of wetness-prone marginal soils. One is the extent of N2Oemissions: do emission factors (the fraction of applied N lost asN2O [e.g., 56]) increase in wetter (and therefore denitrification-prone) soils such that any emissions reductions due to loweroverall N-fertilization rates are offset? A second factor involvestrade-offs on wetter soils with lower biomass yield potential:addingN to increase yields on otherwise low-yielding sites [e.g.,57] will increase potential N2O emissions but this may be morethan offset by the increased yields (see VanGroenigen et al. [58]for row crops) and increased displacement of fossil fuels. Whileevaluation of these questions is underway, it is pertinent toconduct comprehensive life cycle analyses of second-generation bioenergy feedstock production from wetness-prone marginal lands in the region that consider, among otherfactors, land conversion, fertilization, transport and energy con-version, as well as any associated indirect emissions.

Second-Generation Feedstock Production

The primary categories of second-generation bioenergy feed-stocks of interest to the region are perennial grasses and short-rotation woody crops (Fig. 3).

Perennial Grasses

Grasses have historically been grown in the USA for forage andpasture [59], with both cool- and warm-season grasses used inthe Northeast [60]. Cool-season grasses are usually harvested

Table 3 Environmental impactof bioenergy feedstock produc-tion depends on prior land use(row crop or fallow/abandoned)

a As reviewed byBlanco-Canqui [18]b Extent unclearc Dhondt et al. [148],Dauber et al. [149]

Environmental impact From row crops From fallow/abandoned

Soil organic matter/quality Improves with timea Initial loss, recovery unlikely toexceed initial stateb

Soil physical quality Improves with timea Initial loss, recovery with timeb

Erosion potential Decreases after 1st yeara Increases in 1st year;afterwards?b

Nutrient losses Decreasea Likely increaseb

Pesticide use/losses Decreasea Likely increaseb

Trace gas emissions (N2O, CO2) Decreasea Likely increaseb

Water quality Improvesa Likely improvesb

Wildlife benefits Increasea Unclearc

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several times during the growing season, but typically havereduced productivity during the hottest mid-summer months.In contrast, warm-season grasses start growing later in thespring and have their maximum production period in the sum-mer, and are harvested once per year [61]. Bothwarm- and cool-season perennial grasses have been the focus of intense researchfor use as dedicated energy crops [4, 40, 42, 62]. One of thecandidates, switchgrass, is a widely adapted warm-season grassnative to the USAwhich can be found in most states east of the

Rocky Mountains [62]. Plants generally grow 1 to 2.5 m inheight and develop extensive root systems with total under-ground biomass often equivalent to aboveground yields.Sustained yields of 2.3–17.4 Mg ha−1 can be obtained(Table 4) depending on soils and climate. Switchgrass cultivarsare characterized as either upland or lowland ecotypes; to date,upland cultivars tend to have better winter survival in theNortheast than lowland ecotypes [63]. However, many cultivarscurrently available to producers have not been specifically bredfor improved biomass yield and quality [64]. Cultivars originat-ing from the north-central region of the USA generally do notperform well in the Northeast [65, 66]. Active breeding pro-grams at Rutgers and Cornell universities are developing germ-plasm and cultivars with improved performance specifically forthe Northeast and for bioenergy end uses [65]. In the Midwest,breeders have demonstrated significant biomass yield increaseswith new biomass type cultivars [64, 67], particularly withupland and lowland ecotype hybrids that combine the high yieldpotential of the lowland ecotypes with the high survivorship andcold tolerance of the upland ecotypes. Sustained increases inswitchgrass biomass yields over the long term, similar to whichhas been achieved in corn, will be required to improve produc-tion and increase potential returns for growers.

Although much of the focus on warm-season perennialgrasses for bioenergy has been on switchgrass, several otherspecies have potential for use as dedicated bioenergy crops witheconomically viable yields. Native prairie grasses big bluestem(Andropogon gerdardii Vitman) and indiangrass (Sorghastrumnutans L) [68] have similar physiological and morphologicalgrowth characteristics to switchgrass. While they also growwell on marginal land, two recent studies in Ontario [Canada,one to four cultivars, 1–2 years after establishment; 69] andNew York (three locations, two to ten cultivars, fourth produc-tion year; Mayton et al., unpublished data) found that yields forboth were lower than for switchgrass. Big bluestem is also

Fig. 3 Feedstocks potentially suitable for bioenergy production on mar-ginal lands in the Northeast USA. a Switchgrass (Panicum virgatum L.);b shrub willow (Salix spp.); cmiscanthus (Miscanthus×giganteus); and dreed canarygrass (Phalaris arundinacea L.)

Table 4 Yield of perennial grasses evaluated in the Northeastern USA, with “N” indicating that N-fertilizer was applied. Values given represent yieldsfrom a range of cultivars and/or mixtures, unless otherwise indicated

Location Trial information Switchgrass Mixed warm-seasongrasses and CRPa

Source

Mg/ha (dry weight) Mg/ha (dry weight)

New York Multiple trial locations 2.3–11.92.4–17.4 (N)

8.6–11.27.7–14.2 (N)

[150]

New Jersey, Pennsylvania, New York Multiple trial locations 9.8 prime landb

7.7 marginal landb

4.5–13.9 total rangeb

8.6 prime landb

7.0 marginal landb[66]

New York, Pennsylvania, New Jersey,Maryland, and Virginia

Multiple grasslands (mostly natural)across years

– 6.6 [151]

Vermont Two locations 6.5–9.9c

8.1–13.2 (N)c– [152]

a Conservation Reserve Program (see also Box 5)b Average of various trial locations and multiple cultivarsc Cave in Rock cultivar only

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lower in seedling vigor and has seed appendages that interferewith conventional seeding equipment [70].

An emerging candidate bioenergy feedstock is giantmiscanthus (Miscanthus×giganteus), a sterile triploid hybridof Miscanthus sacchariflorus and Miscanthus sinensis that isclonally propagated and has been shown to do well in very wetsoil [71]. Although it is a warm-season grass, it has a relativelygood low temperature tolerance for photosynthesis (for a C4plant), still producing high yields when grown at 14 °C [72].Yet, while established plants are cold tolerant, winter kill offirst-year plantings has been observed. To avoid major financiallosses due to high planting costs, Lee et al. [73] suggest thatcurrent Midwest-adapted clones will be most successful only inthe southern areas of the Northeast region (i.e., Pennsylvaniaand New Jersey), whereas others include New York and south-ern New England as part of the region where miscanthus willlikely perform well [74]. The yield of miscanthus can consid-erably exceed that of switchgrass [75, 76], but findings to dateare based on studies in Europe and the US Midwest. Whilesome scale-up operations are underway (e.g., Aloterra; www.aloterraenergy.com, and the NEWBio project: www.newbio.psu.edu), those represent efforts in Ohio and states farther west,with little headway to date in the Northeast.

Even though some cool-season grasses do well on wetmarginal soils in the northeastern climate, they have receivedmuch less attention for bioenergy feedstock production thantheir warm-season counterparts. Cool-season reed canarygrass(Phalaris arundinacea L.) is well adapted to elevated soilmoisture [42, 77], can survive repeated inundation [78], andis drought-tolerant [77]. In early screening studies, its yieldsexceeded those of switchgrass on poorly drained northeasternsoils, but fell short of potential switchgrass yields on betterdrained soils [57]. Yields on marginal Iowa mollisolsapproached those of switchgrass, but at higher per ton produc-tion costs [79] due to twice yearly fertilization and harvests.Optimization of cultural practices for bioconversion efficiencyvs. optimal harvest and handling logistics is underway [42, 77].

Perennial Grass Production

A major opportunity regarding the production of perennialgrass feedstocks is easy adoption due to compatibility withcurrent farming systems (Fig. 4), with both equipment andexpertise being widely available. However, a notable draw-back of perennial warm-season grasses is a long establishmenttime: switchgrass seedlings grow slowly and stands only reachfull production in their third growing season. Weed control iscritical during the slow establishment phase [80], but onceestablished, switchgrass has little difficulty maintaining dom-inance. Current data suggests that a 10-year stand life could beadequate for profitability [32].

While good yields are clearly attainable on suitable lands(above, Table 4), there is still a limited research base to enable

matching of cultivars to a range of prevailing field conditions onmarginal soils. Fertilization responses and benefits are still am-biguous: while fertilization improves yields on some soils [81,82], this is surprisingly not the case everywhere [83]. In oneearly study, the effect of N-fertilization was related to soildrainage class: switchgrass yields were unaffected on well-drained soils, but significantly improved with N on poorlydrained soils [57]. Soil drainage is likely also factor of impor-tance determining grass establishment and yields [82], but thepotential returns from bioenergy cropping on marginal soils arenot likely to justify the considerable cost of drainageinstallations.

Relatively few pathogens and pests have been observed ongrowth trials in the region, but specialists are tracking smut,rust, anthracnose, bipolaris leaf spot, and gall midge [84–86].Researchers in the region have recently been evaluating yieldpotential, compositional quality, and environmental impactsof switchgrass and other warm-season perennial grassesgrown in monocultures as well as in grass or grass/legumemixtures. Ongoing research (particularly on marginal soils) isneeded to optimize yields and profitability while mitigatingenvironmental impacts.

Short Woody Rotation Crops

Woody Crops Yields and Research

Having begun in the northeasternUSA in the late 1980s, researchon the use of short-rotation woody crops for bioenergy is pri-marily focused on willow (Salix spp.) [87]. While hybrid poplaris used as a short-rotation woody crop elsewhere in the USA, itssusceptibility to septoria canker precludes commercial use in theNortheast [88]. Willow biomass crops are grown using coppicemanagement that utilizes willow’s natural ability to resprout, andinitial work generally involved genotypes fromEurope, Japan, orCanada [89] that were developed in the 1980s. Since then,willow breeding efforts in the USA have made sizable gains inbiomass production in the last two decades [90, 91]. Yield gainsof approximately 20 % over foundation breeding material havebeen realized [92, 93] and additional gains are likely, based onpreliminary analysis of recent genetic selection trial results [94].Through these efforts, economic viability of this crop may beattained even on marginal lands. An overview of studies in thenortheastern USA and eastern Canada indicates annual biomassyields ranging between 4.5 and 15.5 Mg ha−1 (Fig. 5). Willow isparticularly suited for the marginal soils in the region, as ittolerates wet soil well [95, 96]. Despite the fact that wet soilsare inherently linked to limited trafficability, this presents achallenge only for willow planting operations because harvestis often carried out when the soil is frozen.

Development of improved cultivars has been largely basedon the production of interspecific hybrids through controlled

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pollinations, including advanced generation crosses involvingmultiple species combinations [90]. Current willow cultivarsare not particularly vulnerable to pests and diseases, butexpansion of production is likely to increase pest and diseasepopulations. Improved pest tolerance and rust resistance havebeen significant among first-generation hybrids tested in NewYork [97]. Genomics-assisted breeding will be possible in thenear future for Salix purpurea, Salix suchowensis, Salixviminalis, and other species, and studies underway using bothassociation and QTL trait mapping approaches should identifyloci that can be selected early in the breeding process [98].Breeding efforts have also resulted in broadening the geneticdiversity of commercial cultivars that can be deployed, thushedging against widespread crop failure if pest or diseaseresistance were to be defeated and allowing for planting ofgenetically diverse genotype mixtures [99]. Future breedingefforts should consider genotypic differences in nutrient useefficiency [100], with aim of developing cultivars that are welladapted to nutrient-poor and low pH sites. This genetic im-provement of shrub willow, together with producing newcultivars with pest and disease resistance and greater yieldacross a wide range of (marginal) soils in the Northeast, willbe critical for the long-term success of this crop.

Production of Woody Crops

Production of short-rotation woody crops is more challengingto integrate into current farming systems than perennialgrasses because the specialized equipment and expertise need-ed to grow and harvest these woody crops (Fig. 4) are not (yet)widely available. Woody crops moreover require even longerthan perennial grasses to reach peak production: yields fromtrials undergoing multiple harvest cycles have demonstrated anearly 20 % increase from the first to second rotation, with

many cultivars maintaining yield increases by the fourth har-vest cycle or after 13 years of production [93]. Stands can lastat least seven rotations or >20 years [39, 87] before growersmay decide to replant, and due to substantial front-end costs, astand life of circa 22 years is currently required for adequateprofitability, since the “breakeven” point with current eco-nomics is not reached until the end of the third or fourthrotation [101]. For producers, this implies a long return-on-investment horizon, whereas for markets this means that anynear-term increases in woody crop acreage do not translateinto immediate increases in feedstock availability since thefirst crop is typically only harvested 4 years after planting.

Given the long lifespan of a stand, adequate nutrient man-agement is essential, particularly on nutrient-poor soils.Because willow can be harvested multiple times throughoutits 20+ year stand life, it is hypothesized that soil nutrient poolsmay be reduced to the point that yield is negatively impacted[102]. While field evidence for this is inconclusive [103, 104],much attention has been given to quantifying rates of nutrientremoval through harvesting, with fertilization recommenda-tions largely based on compensating for these removal rates[105, 106], usually after each harvest [87], and influenced byprior land use history [107]. Naturally, fertilizer is applied toincrease biomass yields on nutrient-poor sites. As deploymentof shrub willow crops expands in the region, clear guidelinesfor nutritional requirements will be necessary, including bothshort-term nutrient requirements for establishment as well aslong-term requirements for economically viable yields.

Despite decades of research on fertilization of shrub wil-low, fertilizer requirements are still uncertain [108], and anal-ysis of willow studies in the region (Fig. 5a, b) showed nocorrelation between N-fertilizer rate and biomass yield(Fig. 5c). Organic amendments tended to give the greatestresponse; however, they also tended to be applied at the

Fig. 4 Equipment used for sitepreparation, planting, andharvesting operations in shrubwillow production. a Zone tillageused for reduced tillage practicesin site preparation for shrubwillow planting. b The Danishfour-row Egedal Energy Planterin use in upstate NY. c The NyVraa JF 192 single-row tractormounted willow harvester in usein upstate NY. d The HenrikssonSalix AB harvesting headerattached to a John Deere forageharvester, manufactured inSweden

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highest rates (Fig. 5a). Although part of the wide range infertilizer effects may be due to variation in crop age at the timeof application and the frequency of application, it may alsoindicate that factors other than N are limiting crop growth. Forinstance, nutrient uptake could be limited by low water avail-ability during the growing season on drought-prone marginalsoils, since some studies have shown greater yields wherewillow is well watered and fertilized [100, 108]. Conversely,excessive soil moisture can negatively impact nutrient acqui-sition and growth in woody species, although for poplar morethan for willow [95, 96]. Most studies on willow production todate are based on relatively short time series and/or on alimited number of sites. A comparison of data from multiplerotations and sites across the region may help clarify drivingfactors of soil nutrient changes and fertilization effects. Suchan assessment is not only important from a production stand-point but is also relevant from the economic and environmen-tal perspectives. Since fertilization can account for ~10 % ofproduction costs [101] and 20–35 % of the total energy inputsto willow production [109], optimal rates for biomass produc-tion should be weighed against economically and energetical-ly optimal rates. Additionally, inappropriate application ratesor timing can result in nutrient losses through runoff orleaching [102]. Any potential gains in yield as a result offertilization must be weighed against these economic andenvironmental factors.

Energy Conversion

Perennial Grasses

Perennial grasses are suitable for multiple energy conversionpathways, including pyrolysis, ethanol fermentation, and po-tentially combustion-based systems. Given that liquid biofuelconversion pathways have historically been given the majorityof attention, the conversion and use pathways discussed hereare relatively near-term and low-cost combustion applications(bioheat). Major current challenges with implementing grassbioheat include maintaining consistent feedstock quality, post-harvest feedstock management, development of appropriatecombustion technologies, and air quality.

Feedstock Quality and Post-Harvest Feedstock Management

Grass bioheat appliances burn feedstocks in compressed form(pellets, pucks, or bricks) or, for large applications, as wholebales. Feedstock composition and quantity of combustionresidue (ash) are the primary factors determining whether ornot a feedstock can be burned effectively in a particularappliance. Most appliances function well when ash contentis low (<1 %, comparable to woody feedstocks), but higherash contents complicate operation because of corrosion and/or

Fig. 5 Overview of shrub willow yield from studies conducted in thenortheastern US and eastern Canada: effects of organic and syntheticfertilization (a, b), and yield response vs. fertilization rate (c) in the samestudies.Horizontal bars in a, b refer to biomass yield (bottom x-axis) fromnon-fertilized control (gray) and fertilized (black) plots, with the corre-sponding fertilization rate (top x-axis) denoted using black circles connect-ed by lines. Asterisks indicatewhere statistically significant (p<0.05) resultswere reported. Symbols in c refer to references as follows: star = Adegbidiet al. [105], mean of five clones; open/filled triangle =Adegbidi et al. [153];open/filled diamond = Cavanagh et al. [154]; filled plus sign = Kopp et al.[155], first and third annual harvest yields shown from lowest plantingdensity; ○=Labrecque et al. [156], data shown are from the poorly drainedsite only; open/filled square = Quaye et al. [157], data from newly planted“young” field; open/filled inverted triangle = Quaye, Volk [158], data aremeans of three sites and two clones. Filled symbols in c indicate a syntheticfertilizer treatment, while open symbols indicate an organic N source

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melting of ash into solid clinkers (incombustible fragments)that can hinder air or ash movement, increase maintenancecosts, and eventually force boiler shutdowns. Ash contents ofgrass feedstocks range from 1 to over 20 % [110], with ashcontents exceeding 10 % usually caused by excessive soilcontamination of the feedstock. Ash content is mainly con-trolled by themineral composition of the feedstock, in particularits Cl, K, N, S, and Si. K is by far themost abundant alkali metalin grasses and reduces the melting temperature of ash andcontributes significantly to corrosion potential. Cl is a particu-larly damaging component as it catalyzes corrosion reactionsand is a potential emissions pollutant.While little can be done tocontrol S and Si, the content of the other elements can bemanaged by avoiding overfertilization of N and particularly Kand Cl which are subject to excessive luxury uptake [111].Feedstock mineral composition varies considerably among spe-cies [112] and can also be managed by the timing of grassharvest and baling [113].While delayed baling or overwintering(spring harvest) of the crop can result in significant leaching lossof certain elements [114], these practices come with the risks ofyield loss and increased feedstock contamination with soilwhich may offset any benefits resulting from the delayed har-vest. Research is underway to modify grass biomass composi-tion to minimize potential corrosion and clinkering, and thusmake the feedstocks suitable for a wider range of appliances.

Post-harvest feedstock management (densification, trans-port, and storage) is another factor affecting the quality of thecombustion product. In contrast to woody biomass that can bechipped for easy transport and handling, grass biomass typi-cally requires some form of densification. Pellets (typically~0.6–0.7 cm in diameter, <3.8 cm in length) are currently themost common form of densified grass, produced by sizereduction, heating, and compaction. They are typically usedin small-scale combustion appliances, whereas larger productssuch as pucks, briquettes, or bricks are more appropriate forlarger scale combustion systems [115], especially for feed-stocks with pelleting problems. Consistent physical propertiesof densified products improve storage, transportation, andhandling characteristics, and can positively affect both thequality and cost of the feedstock [115]. High product qualityfurthermore facilitates safe storage of the material, as accurateobservation of limits on the percent fines can prevent dustexplosion or spontaneous combustion in silos [115].

Appliance Design

Appliance design is a major consideration for combustion ofany biomass fuel, and design and production of grass-capableappliances has lagged behind the wood pellet-based commer-cial market. The primary technical stumbling block for a bio-mass combustion industry based on feedstocks from marginallands is the lack of appliances specifically designed to burnhigh ash, low melting point pellet fuels. Although it is worth

attempting to breed feedstocks to reduce ash contents, a morerobust solution is to modify appliances to be able to burn adiversity of feedstocks. Industrial-sized ceramic-lined boilersare currently capable of burning grasses, and residential-scalehydronic boilers with ceramic-lined combustion chambers,moving grates, and automatic de-ashing are capable of burninggrass pellets up to ash contents of 10%. Avariety of indoor andoutdoor pellet boilers becoming available in the USA arecapable of burning a range of biomass pellets, although theirdurability is relatively unknown. Research and development istherefore required for appropriate combustion technologies. Forinstance, some of these issues can potentially be resolved byblending grass with lower ash content fuels such as corn grain[116] and by ensuring consistent physical and chemical qualityof grass pellets. Because grass feedstocks from heterogeneousmarginal lands are likely variable in composition and thus inphysical pellet quality, pellet quality standards (akin to those inplace for wood pellets) are essential for small-scale combustionand advisable for large-scale combustion. The European stan-dard EN 14961-6 defines fuel specifications for a few specificnon-woody fuels for non-industrial use [117]. Standards varyamong these feedstocks, however, and parameter values are notbased on their overall impact on the combustion process.Recently, a quality index was therefore developed for grasspellets that sum qualitatively different parameters into oneindex value for relative evaluation of residential combustionpotential [118]. Such a quality labeling system for grass pelletsencourages production of a more consistent fuel and helps winthe trust of industry and small combustion appliance owners.

Air Quality

Air quality is a major concern for grass bioenergy develop-ment in the region, as the utilization of bioheat at larger scalesis only possible when health-based emissions criteria are met.Inefficient combustion of grasses can cause considerableemissions of particulate matter, chlorinated compounds, andNOx. These emissions are mainly influenced by (1) the com-position of the feedstock, (2) type of appliance, and (3) modeof operation (such as start-up, partial load, and full loadsettings). A limited number of non-woody fuels have beentested in a few combustion appliances, with variable results todate for particulates and gas-phase emissions. In some cases,non-woody fuels have performed better than wood pellets[119–123]. For example, Verma et al. [121] found lowercarbon monoxide and particulate emissions for grass thanwood pellets when evaluating a multi-fuel boiler under con-ditions optimized for each fuel. They concluded that combus-tion process optimization is essential, not only for each type offuel but also at each operational load. Attempting to burn grassin a boiler optimized for wood will most likely result in veryinefficient combustion and high emissions of particulates andundesirable chemical compounds [116, 124].

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Willow

Suitability and Feedstock Management

Willow biomass, like grass, is suitable for multiple energyconversion pathways, including pyrolysis, fermentation,and combustion. Conversion of willow biomass is lesscomplex than for grass, but the main issues of feedstockmanagement, appliance design, and air quality are similar.The suitability of willow biomass for energy production isoften compared to that of other hardwoods [e.g., 125], butthere are a few misconceptions in this discussion, includ-ing that willow makes a poor choice for energy produc-tion due to lower energy content and higher ash andmoisture content than other woody biomass. Becausewillow has lower specific gravity than other hardwoods[compare 97, 126, 127], its energy content on a volumebasis is lower, but on a weight basis, willow has similarenergy content [128, 129]. A ton of willow will thereforeprovide the same energy as a ton of other hardwoods, but4 to 36 % more space is needed to store the feedstock.The misconception that willow biomass has higher ashcontent than other hardwoods likely originates from thefact that willow has a higher proportion of bark due tomultiple stems per plant. Nevertheless, the ash content ofwillow is relatively low—ranging from 1.1 to 2.7 %across multiple cultivars at three sites [89, 97, 126], andaround 2.2 % for over 150 samples collected during large-scale harvesting operations [130]. These values are similarto values reported for whole tree chips or forest residuals[129]. Due to their similarity, willow biomass can bemixed with other hardwood chips as part of an integratedfeedstock supply.

In terms of feedstock management, wood chip and pelletquality are important factors. Wood chip quality is in partdetermined by moisture content, which is affected by harvesttiming. Eisenbies et al. [130] found that subfreezing airtemperatures at harvest resulted in slightly drier wood chips,which was significant in that moisture content was determi-nant whether chips were classified as class B instead of classA under ISO standard 17225-5 [131] for graded wood chips.Willow biomass can make good quality pellets, but ashcontents typically above 1 % [132, 133] disqualify them aspremium pellets according to the Pellet Fuel Institute stan-dards [134] and these pellets may be best suited for indus-trial energy applications that can better deal with slightlyhigher ash content. Mixing of willow and other hardwoodsmay be a solution for this, as trials mixing willow withdebarked maple chips resulted in <1 % pellet ash contentwhen ≥1/3 of the biomass in the mix was debarked maple(Volk, unpublished data). Blending with miscanthus had nosuch effects, but had other benefits such as increased pelletdurability [132].

Air Quality

Using current boiler appliances, particulate matter emissions(PM-2.5) can be high [135], and higher than from oil andespecially natural gas. According to the New York StateDepartment of Health, wood smoke is the largest source ofcarbonaceous PM-2.5 in rural New York [135]. This isbecause residential wood-fueled hydronic heaters often op-erate at relatively low temperatures under oxygen-starvedconditions, resulting in high particulate emissions as wellas harmful unoxidized gaseous compounds. Several stepsare being taken to reduce these emissions and improve airquality. For example, the US Environmental ProtectionAgency (EPA) has developed programs aimed at greatlyreducing the emissions of hydronic heaters; the currentprogram makes these appliances 90 % cleaner than unqual-ified models [136]. Further improvements are being made inthese units both in North America and in Europe. In additionto improving the combustion technology, the use of feed-stocks with a consistent defined set of characteristics isimportant. The EPA is therefore developing New SourcePerformance Standards for residential wood heaters thatwould be phased in for several years and vary somewhatbetween types of heating units [137]. Heterogeneous bio-mass fuels from marginal lands will require state-of-the-artcombustion technology and practices to minimize emissionsand consequent health risks [138].

Socioeconomic Challenges

As discussed in the “Introduction” section, large-scale pro-duction of bioenergy in the Northeast USA has varioussocioeconomic benefits, but also comes with challenges.The potential land resource base is not only parcelized(Box 3) but also has competing uses. Marginal land isfrequently used for hay or pasture, and it remains to be seenwhether land owners will continue forage production orbegin active production of perennial bioenergy crops (eitherthemselves or via land rental to biomass management com-panies or cooperatives). Landowners may also elect to main-tain lands via occasional mowing or may abandon agricul-ture altogether (e.g., sell land for development or let it revertto successional growth). Considerations of NIMBY (not inmy backyard—including objections to farming operations ortransportation of truckloads of biomass) may also adverselyaffect decisions to begin production. There are similar com-peting uses for the feedstocks, as perennial grasses andwoody material suitable for bioenergy production are alsosuitable for bedding, mulch, and bioproducts. As feedstockproduction depends both on landowner willingness to pro-duce and users to consume, there is furthermore a need toovercome the current lack of knowledge by landowners and

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energy consumers about bioenergy opportunities, as well asthe lack of trained and knowledgeable designers and in-stallers of biomass systems. Addressing these issues mayovercome inertia among producers, consumers, and the en-ergy sector, and allow full utilization of the socioeconomicpotential that exists around production of bioenergy in theregion. Recent shale gas development continues to radicallyaltered energy and bioenergy economics for the region. Forexample, some power plants that were slated to co-firebiomass with coal have instead been converted to naturalgas. Increased production of bioenergy in the region willcontinue to be affected not only by these regional factors butalso by national and global geopolitical trends anduncertainty.

Policy

A growing bioenergy market requires supportive policies atlocal, State, and federal levels. Early national assessments ofbioenergy potential tended to underestimate or discount theproduction potential of the Northeast USA, for example byfocusing only on the availability of recently abandoned agri-cultural lands as opposed to the longer term abandonmentexperienced in the region. This left the initiative for thedevelopment in the region in the hands of states, localities,and individuals. In contrast to development in accord withtop-down policy directives, there have been numerous diverseand creative entrepreneurial bottom-up initiatives in the regionaddressing renewable bioenergy (Box 4). These bottom-upapproaches now can inform and catalyze more recent Federalinitiatives in the region, which include Biomass CropAssistance Program feedstock promotion programs fundedby the US Department of Agriculture (USDA) (Box 5) andthe previously mentioned NEWBio Northeast regionalbioenergy consortium.

Funding for research and development has been availablefrom many state entities, with at least seven different bodiesbeing involved in the promotion and regulation of renewableenergy in for example New York (Box 4), whether taskedofficially or voluntarily as a means to serve the public good.Bioenergy has also been supported for some time by thePublic Service Commission through the RenewablePortfolio Standard with varying degrees of success [139].Because a robust bioenergy industry can potentially createnew markets for products of farmland and forestland andthereby increase economic security for rural land owners,bioenergy has also been supported by the NY StateDepartment of Agriculture & Markets and Department ofEnvironmental Conservation. Like in New York, financialstimuli are also available in other Northeastern States, withstate funding and/or rebate programs in place to supportbioheat projects in for instance Vermont, New Hampshire,

Maine, and Massachusetts [14]. The same States as well asNew York furthermore waive States sales tax on residentialbiomass fuel and in some cases also on commercial or indus-trial biomass fuel and biomass boilers [14].

As the opportunities at the State level are increasinglybeing developed and utilized, there is a need for new support-ive policies that can facilitate and stimulate further develop-ment of sustainable bioenergy production in the region.Expansion of bioenergy production is limited on multiplepolicy fronts, including regional greenhouse gas initiatives,federal land conservation programs, research funding struc-tures, and federal biofuels policies:

& The regional greenhouse gas initiative (RGGI, www.rggi.org) is a regulatory program signed by nine NortheasternStates that aims at reducing CO2 emissions from thepower sector. Even though full life cycle analysesindicate that emissions from bioenergy are lower thanfrom burning fossil fuels, RGGI rules can be sorestrictive that they do not promote bioenergy fromexisting mixed-species forests.

& Several federal land conservation programs either direct-ly or indirectly support the production of second-generation bioenergy feedstocks (see Box 5). Yet, eventhough production is supported, harvest and use is notallowed on land in Conservation Reserve Programs[140, paragraph 626].

& The use of long-abandoned (prior to 2007, depending onmanagement) farmland for bioenergy is not allowed underRenewable Fuel Standard Program regulations [141], de-spite the fact that abandoned farmland is the main landbase available for bioenergy feedstock production in theregion.

& Understanding and development of perennial energycrop systems requires funding that allows these sys-tems to be monitored over several years. Switchgrassdoes not reach full production until its third year, whensoil conditions are clearly not near equilibrium. Willowbiomass crops are only first harvested 4 years afterplanting, and important changes occur between the firstand second rotation (7 years after planting) that impactboth economics and the greenhouse gas balance [93].Typical short (e.g., 2–3 years) project funding cyclesmake it difficult to capture and understand the dynam-ics of these perennial systems and impossible to fundlong-term breeding programs.

& Current federal policy promotes biofuels for transportationfuels but not for heat or combined heat and power, whichis the most optimal use of the cellulosic second-generationbioenergy feedstocks that can be produced on marginallands in the region.

& Finally, and perhaps most importantly, current policieslimit innovation by specifying favored biomass sources

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(species) or technologies instead of rewarding desiredoutcomes. Despite the fact that federal [142] and forexample New York State [143] definitions of “renewableenergy sources” include all-inclusive terms like “biomass”and “plant and forest products,” respectively, withoutspecifying desired energy conversion pathways or tech-nologies, programs and incentives such as those offeredby the USDA, US Department of Energy (DOE), and theNY State Energy Research and Development Authority(NYSERDA) are nearly always technology- or source-specific. Current policies thereby directly limit innovationthat involves new species and production processes,which is essential for the new bioenergy opportunities inthe Northeast.

Without new supportive policies for second-generationbioenergy feedstock production and conversion, research,development , and adopt ion wil l be very slow.Competition and innovation will result in a more robustclean energy economy in the Northeast USA if state andfederal policy makers avoided picking “winner” fuels andtechnologies, but rather set targets based on technologiesthat (for instance) achieve (1) the lowest cost per unitreplacement of fossil fuels with renewable sources ofenergy, (2) the lowest cost per ton of carbon reduction,and (3) the greatest local job creation potential. Thisapproach, along with equitable legislation and state pro-curement policies for all local sources of renewable ener-gy, will help spur expansion of renewable bioenergy pro-duction and use.

Box 4. Clarifying examples and notes

1. Bottom-up approaches addressing renewable bioenergy in the region

Examples given simply to show the range of bottom-up initiatives includethe New York Bioenergy Association (www.newyorkbiomass.org),which promotes the support, understanding, and use of biomass forenergy production; the Northeast Biomass Thermal Working Group(www.nebioheat.org), which promotes the use of biomass for heatingand combined heat and power; the Danby Land Bank, a cooperative oflocal landowners that allows energy consumers to pool idled lands andbecome bioenergy producers; EnviroEnergy LLC (www.enviroenergyny.com), which pioneered pelletization of a range offeedstocks; and switchgrass pelletization and utilization at ErnstConservation Seeds (www.ernstseed.com).

2. Example of state bodies involved in promotion and regulation ofrenewable energy in New York

• New York State Legislature,

• New York State Assembly,

• New York State Energy Research and Development Authority(NYSERDA),

• Department of Agriculture and Markets,

• Department of Environmental Conservation,

• Public Service Commission and the Governor's office,

• and others.

Box 5. Federal land conservation programs

The US Department of Agriculture (USDA) has several Farm Billconservation programs in place to support farmers and private land-owners by offering technical and financial assistance. These voluntaryprograms are administered through the Natural Resources Conserva-tion Service (NRCS), in some cases in collaboration with the FarmService Agency (FSA), and are aimed at the enhancement and pro-tection of natural resources like soil, water, air, flora, and fauna.

The 2008 FarmBill has several conservation programs in place that are ofinterest to farmers and landowners interested in producing second-generation bioenergy feedstocks.1 These programs either directly tar-get production of these feedstocks, or indirectly provide potentialopportunities for bioenergy feedstock production, particularly throughprograms promoting wildlife habitat:

• The Biomass Crop Assistance Program (BCAP) directly promotesbioenergy feedstock production. It offers financial incentives to privatelandowners to establish and produce biomass crops for heat, power,biobased products, or advanced fuels [144, 145]. In select New Yorkcounties, BCAP supports shrub willow as the target feedstock [146].Landowners enter into 11-year contracts with the USDA during whichthey are tied to a nearby biomass conversion facility. For this, theyreceive annual rental payments for lands enrolled in the program, costshare assistance for shrub willow plantings and land preparation ac-tivities, and harvest payments.

• The Environmental Quality Incentives Program (EQIP) includes awildlife component that may allow conservation practices favoringgrass- and shrubland nesting birds. Native warm-season grass estab-lishment and management is one of the practices that could be sup-ported by these programs, with occasional late-season mowingallowing for harvesting without interfering with promoted specieshabitat. Removal of dense thickets is another example of a mainte-nance practice required to maintain early successional habitat. Withmany stems per hectare this presents a secondary opportunity forwoody biomass harvest. In either case, potential biomass harvestingand utilization must not interfere with the primary overall conservationobjectives of the program, which are the protection and enhancementof soil, water, air, plant, and animal resources in general.

The Conservation Reserve Program (CRP) helps agricultural producerssafeguard environmentally-sensitive lands [140]. CRP participants canplant long term resource conserving covers to improve water quality,control soil erosion, and enhance wildlife habitat. Even though nativewarm season grass establishment is one of many eligible practicesallowed under this program, CRP explicitly prohibits harvest or com-mercial use of ‘any kind of crop’ [141, paragraph 626]. Despite therebeing interesting opportunities for second-generation bioenergy feed-stock production from CRP land, this is currently not allowed

Conclusions

There are exciting opportunities for second-generationbioenergy production in the Northeast USA (Table 5). Theregion’s favorable climate, abundant water, and the suitabilityand potential availability of a large base of idle marginal landsare resources that could support a large new bio-economywithout inducing the food vs. fuel competition that is an

1 At the time of writing, there are no details yet on the upcomingconservation programs under the 2014 Farm Bill—for up to date infor-mation please refer to www.fsa.usda.gov and www.nrcs.usda.gov.

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unfortunate characteristic of first-generation bioenergy cropproduction [2] on prime agricultural lands.

Regionally adapted perennial grass and woody feedstocksare being improved by plant breeding and agronomic re-search. Recent and current research initiatives explicitly targetthe challenges and impacts of production on marginal lands

that constitute the region’s primary available land base. Whilebioenergy production can provide both (socio)economic andenvironmental benefits (Table 5), there are significant factorsthat need to be resolved in order to accelerate bioenergyproduction in the region, including improved insight intoproducer and consumer willingness to adopt new energy

Table 5 Summary of opportunities and challenges for bioenergy production in the Northeast USA

Category Opportunities Challenges

Climate Water abundant, temperate climate

Land availability Lot of marginal land, not in forest not in row crops This is marginal land (see soil and hydrology)

Socioeconomic Replacement of imported and expensive heating oilStimulation of local economiesOpportunity for entrepreneurs to develop local bioenergysupply chains

Close proximity between production and use

Resistance to change from producers, consumers, and theenergy sector

Land parcelization and competing usesLack of knowledge by landowners and energy consumers about

bioenergy opportunitiesInconsistent markets for perennial crops

Land quality Though little of the land is suitable for annuals, most of thisland is suitable for perennials

Most available land has some or more restrictions for farmingbecause of excess wetness, shallow or acidic soil, sloped land

Poor drainage limits root growth, trafficability

Environmental impact,greenhouse gasmitigation

On most soils, appropriate bioenergy systems will reduceGHG emissions compared to fossil fuels

Positive effects of going from annuals to perennials includeincreased soil health, carbon sequestration, reducederosion and water quality impacts

On wet soils with low yield potential there may be high N2Oemissions that reduce or cancel out the benefit

Environmental impact of converting abandoned land toperennial crops is unclear; even very low impacts on an areabasis can still be considerable impacts on a regional basis

Production

Perennial grasses Good yields are attainable on suitable landsEquipment and expertise widely availableSome species tolerate wet soils

Time to establishment 2–3 years10-year stand life could be adequate for profitabilityNew species such as switchgrass require research anddevelopment

Short-rotation willow Good yields and economic viability of this crop may beattained even on marginal lands

Tolerates wet soil

Time to full production ~13 yearsBreak even at 3rd to 4th rotationEquipment and expertise not (yet) widely availableResearch and development needed regarding breeding, fertilizer

requirements and long-term production

Energy conversion

Perennial grasses Suitable for pyrolysis, conversion to cellulosic ethanol,potentially suitable for combustion in specialized units

Achieving consistent feedstock qualityResearch and development required for appropriate combustion

technologiesWith combustion, air quality challenges include particulatematter, chlorinated compounds and NOx

Densification, transport, storage

Short-rotation willow Can be readily combined with other sources of woodybiomass

Suitable for existing furnaces and boilers, mostly atcommercial scales

Competitive with other hardwoods

Research and development required for appropriate combustiontechnologies and consistent feedstock quality

Even with appropriate combustion technology, particulatematter emissions can be higher than from oil

Densification, transport, storage

Policy Funding for research and development has been availablefrom many state entities

Without new supportive policies, research, development andadoption will be very slow

RGGI rules can be so restrictive that they don’t promotebioenergy

Federal land conservation programs: harvest not allowed onCRP land, use of long-abandoned farmland for bioenergy notallowed

Current federal policy promotes biofuels for transportation fuelsbut not for heat or combined heat and power

Current federal policy limits innovation by only stimulating pre-ordained species and technologies

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sources, and improved engineering of biomass combustionapplications. The region’s existing momentum towardbioenergy production is the result of diverse and creativeinitiatives at multiple levels. Development of the regionalbio-economy to its full potential will require not only theresearch and development cited above but also a more favor-able regulatory and policy incentive framework that rewardsdesired outcomes (Table 5), which will not only benefit rurallivelihoods and environmental quality but also the regionaland national economies.

Acknowledgments This paper arose from a collaborative multidisci-plinary seminar series “Untapped Potential: Sustainable Bioenergy Pro-duction on Marginal Lands of New York and the Northeast” held atCornell University in 2012, 2013, and 2014. The seminar brought togeth-er speakers from inside and outside of academia, focusing on the region’smarginal land bioenergy potential. We thank all seminar participants fordiscussion, and Ellen Demey and Valerie Podolec for their helpful com-ments. This work was supported in part by the USDA-NIFA throughSustainable Bioenergy Grant No. 2010-03869, AFRI Competitive GrantNo. 2012-68005-19703, and Cornell University Agricultural ExperimentStation federal formula funds Project No. 125-7832; as well as by theUSDOE Energy Bioenergy Technologies Office through the North Cen-tral Regional Sun Grant Center at South Dakota State University (AwardNo. DE-FC36-05GO85041). Any opinions, findings, conclusions, orrecommendations expressed in this publication are those of the author(s)and do not necessarily reflect the view of the USDA, NIFA, USDA-NRCS, USDA-FSA, or the New York Bioenergy Association.

References

1. Gopalakrishnan G, Negri MC, Wang M, Wu M, Snyder SW,LaFreniere L (2009) Biofuels, land, and water: a systems approachto sustainability. Environ Sci & Technol 43(15):6094–6100. doi:10.1021/es900801u

2. Valentine J, Clifton-Brown J, Hastings A, Robson P, Allison G,Smith P (2012) Food vs. fuel: the use of land for lignocellulosic‘next generation’ energy crops that minimize competition withprimary food production. GCB Bioenergy 4(1):1–19. doi:10.1111/j.1757-1707.2011.01111.x

3. Campbell JE, Lobell DB, Genova RC, Field CB (2008) The globalpotential of bioenergy on abandoned agriculture lands. Environ Sci& Technol 42(15):5791–5794. doi:10.1021/es800052w

4. McLaughlin SB, Adams Kszos L (2005) Development of switch-grass (Panicum virgatum) as a bioenergy feedstock in the UnitedStates. Biomass Bioenergy 28(6):515–535

5. Varvel GE, Vogel KP, Mitchell RB, Follett R, Kimble J (2008)Comparison of corn and switchgrass on marginal soils forbioenergy. Biomass Bioenergy 32(1):18–21

6. USDOE (2011) U.S. billion-ton update: biomass supply for abioenergy and bioproducts industry, ORNL/TM-2011/224. R.D.Perlack and B.J. Stokes (Leads), U.S. Department of Energy(DOE), Oak Ridge National Laboratory, Oak Ridge, TN, USA,http://www1.eere.energy.gov/bioenergy/pdfs/billion_ton_update.pdf

7. Gelfand I, Sahajpal R, Zhang X, Izaurralde RC, Gross KL,Robertson GP (2013) Sustainable bioenergy production from mar-ginal lands in the US Midwest. Nature. doi:10.1038/nature11811

8. Nijsen M, Smeets E, Stehfest E, van Vuuren DP (2012) An evalu-ation of the global potential of bioenergy production on degraded

lands. GCB Bioenergy 4(2):130–147. doi:10.1111/j.1757-1707.2011.01121.x

9. U.S. Census Bureau (2010) 2010 Census of population and hous-ing, summary population and housing characteristics, CPH-1–1,Table 8 Land area and population density. U.S. GovernmentPrinting Office, Washington

10. USEIA (2013) Residential Energy Consumption Survey (RECS),Table HC1.7 Fuels used and end uses in U.S. homes, by CensusRegion, 2009. US Energy Information Administration, http://www.eia.gov/consumption/residential/data/2009/#undefined, accessed 11March 2014

11. USEIA (2014) Heating oil explained—use of heating oil USEnergy Information Administration, http://www.eia.gov/energyexplained/index.cfm?page=heating_oil_use, accessed 11March 2014

12. BTEC (2010) Heating the Northeast with renewable biomass: abold vision for 2025, http://www.biomassthermal.org/resource/pdfs/heatne_vision_full.pdf. Biomass Thermal Energy Council,Washington DC, USA; Alliance for Green Heat, Takoma ParkMD, USA; Maine Pellet Fuels Association, Portland ME, USA;New York Biomass Energy Alliance, Syracuse NY, USA; PelletFuels Institute, Arlington VA, USA

13. Cuomo AM (2014) Launch renewable heat NY: the low-emissionbiomass heating initiative. Building on Success, 2014 State of theState, http://www.governor.ny.gov/assets/documents/2014-SOS-Book.pdf, pp 66–69

14. BERC (2013) An overview of biomass thermal energy policyopportunities in the northern forest region. Biomass EnergyResource Center, http://www.biomasscenter.org/news/2013/11/26/an-overview-of-biomass-thermal-energy-policy-opportunities-in-the-northern-forest-region

15. NYSERDA (2012) Patterns and trends New York State EnergyProfiles: 1996–2010. New York State Energy Research andDevelopment Authority

16. NYSERDA (2010) Renewable fuels roadmap and sustainablebiomass feedstock supply for New York. . New York StateEnergy Research and Development Authority Report 10–05.April, 2010., http://www.nyserda.org/Publications/Research-and-Development-Technical-Reports/Biomass-Reports/Renewable-Fuels-Roadmap.aspx

17. Wilson TO, McNeal FM, Spatari SG, Abler D, Adler PR (2011)Densified biomass can cost-effectively mitigate greenhouse gasemissions and address energy security in thermal applications.Environ Sci & Technol 46(2):1270–1277

18. Blanco-Canqui H (2010) Energy crops and their implications on soiland environment. Agron J 102(2):403–419

19. Bonin C, Lal R (2012) Chapter One—agronomic and ecologicalimplications of biofuels. In: Donald LS (ed) Advances in agronomy,vol 117. Academic, New York, pp 1–50. doi: 10.1016/B978-0-12-394278-4.00001-5

20. James P, Howes P (2006) Regulation of energy from solid biomassplants, Report ED51518. AEA Technology, http://www.biomassenergycentre.org.uk/pls/portal/docs/PAGE/RESOURCES/REF_LIB_RES/PUBLICATIONS/REGULATION%20OF%20ENERGY%20DEFRA.PDF

21. EU (2009) Directive 2009/28/EC of the European Parliament and ofthe Council of 23 April 2009 on the promotion of the use of energyfrom renewable sources. Off J Eur Union L140:16–62

22. FAO (2007) A review of the current state of bionergy develop-ment in G8+5 countries. Global Bioenergy Partnership (GBEP),Food and Agriculture Organization of the United Nations (FAO)http://www.fao.org/newsroom/common/ecg/1000702/en/GBEPReport.pdf

23. Bracmort K (2012) Biomass: comparison of definitions in legisla-tion through the 112th Congress, Report R40529. CongressionalResearch Service, https://www.fas.org/sgp/crs/misc/R40529.pdf

Bioenerg. Res.

24. Peterson GM, Galbraith J (1932) The concept of marginal land. JFarm Econ 14(2):295–310

25. Dauber J, Brown C, Fernando AL, Finnan J, Krasuska E, PonitkaJ, Styles D, Thrän D, Van Groenigen KJ, Weih M (2012)Bioenergy from “surplus” land: environmental and socio-economic implications. BioRisk: Biodiversity & Ecosystem RiskAssessment 7

26. Richards BK, Stoof CR, Cary IJ, Woodbury PB (2014) Reportingon marginal lands for bioenergy feedstock production: a modestproposal. BioEnergy Res:1–3. doi: 10.1007/s12155-014-9408-x

27. Shortall OK (2013) “Marginal land” for energy crops: exploringdefinitions and embedded assumptions. Energy Policy 62:19–27.doi:10.1016/j.enpol.2013.07.048

28. Arguez A, Durre I, Applequist S, Vose RS, Squires MF, Yin X,Heim RR Jr, Owen TW (2012) NOAA's 1981–2010 US climatenormals: an overview. Bull Am Meteorol Soc 93(11):1687–1697

29. Conklin H (1966) The new forests of New York. Land Econ 42(2):202–203

30. Homer C, Dewitz J, Fry J, CoanM,Hossain N, Larson C, Herold N,McKerrow A, VanDriel JN, Wickham J (2007) Completion of the2001 National Land Cover Database for the Counterminous UnitedStates. Photogramm Eng Remote Sens 73(4):337

31. National Agricultural Statistics Service (2009) 2007 Census ofAgriculture. United States Department of Agriculture, NationalAgricultural Statistical Service. www.agcensus.usda.gov

32. Woodbury PB, Volk T, Germain RH, Castellano P, Buchholz T,Wightman J, Melkonian J, Mayton H, Ahmed Z, Peters C (2010)Analysis of sustainable feedstock production potential in New YorkState Appendix E. In: Wojnar Z (ed) Renewable fuels roadmap andsustainable biomass feedstock supply for New York. . New YorkState Energy Research and Development Authority Report 10–05.April, 2010, http://www.nyserda.org/Publications/Research-and-Development-Technical-Reports/Biomass-Reports/Renewable-Fuels-Roadmap.aspx, pp Ei-E103

33. Steenhuis TS, Winchell M, Rossing J, Zollweg JA, Walter MF(1995) SCS runoff equation revisited for variable-source runoffareas. J Irrig Drain Eng 121(3):234–238

34. Frankenberger JR, Brooks ES,WalterMT,WalterMF, Steenhuis TS(1999) A GIS-based variable source area hydrology model. HydrolProcess 13(6):805–822

35. Walter MT, Walter MF, Brooks ES, Steenhuis TS, Boll J, Weiler K(2000) Hydrologically sensitive areas: variable source area hydrol-ogy implications for water quality risk assessment. J Soil WaterConserv 55(3):277–284

36. Earl R (1997) Prediction of trafficability and workability from soilmoisture deficit. Soil Tillage Res 40(3):155–168

37. Bockus W, Shroyer J (1998) The impact of reduced tillage onsoilborne plant pathogens. Annu Rev Phytopathol 36(1):485–500

38. Rowe RL, Street NR, Taylor G (2009) Identifying potential envi-ronmental impacts of large-scale deployment of dedicatedbioenergy crops in the UK. Renew Sust Energ Rev 13(1):271–290

39. Volk TA, Verwijst T, Tharakan PJ, Abrahamson LP, White EH(2004) Growing fuel: a sustainability assessment of willow biomasscrops. Front Ecol Environ 2(8):411–418

40. Williams PRD, Inman D, Aden A, Heath GA (2009) Environmentaland sustainability factors associated with next-generation biofuels inthe U.S.: what do we really know? Environ Sci & Technol 43(13):4763–4775. doi:10.1021/es900250d

41. Mitchell R, Vogel KP, Sarath G (2008) Managing and enhancingswitchgrass as a bioenergy feedstock. Biofuels Bioprod Biorefin2(6):530–539. doi:10.1002/bbb.106

42. Sanderson MA, Adler PR (2008) Perennial forages as second gen-eration bioenergy crops. Int J Mol Sci 9(5):768–788

43. McLaughlin S, Walsh M (1998) Evaluating environmental conse-quences of producing herbaceous crops for bioenergy. BiomassBioenergy 14(4):317–324

44. Kort J, Collins M, Ditsch D (1998) A review of soil erosionpotential associated with biomass crops. Biomass Bioenergy14(4):351–359

45. Keshwani DR, Cheng JJ (2009) Switchgrass for bioethanol andother value-added applications: a review. Bioresour Technol100(4):1515–1523

46. Schnabel RR, Franzluebbers AJ, Stout WL, Sanderson MA,Stuedemann JA (2001) The effects of pasture management prac-tices. In: Follett RF, Kimble JM, Lal R (eds) The potential of U.S.grazing lands to sequester carbon and mitigate the greenhouseeffect. CRC, Boca Raton, pp 291–322

47. Hansen EM,Christensen BT, Jensen L, KristensenK (2004) Carbonsequestration in soil beneath long-term Miscanthus plantations asdetermined by 13C abundance. Biomass Bioenergy 26(2):97–105

48. Stockmann U, Adams MA, Crawford JW, Field DJ, HenakaarchchiN, Jenkins M, Minasny B, McBratney AB, Courcelles VDRD,Singh K, Wheeler I, Abbott L, Angers DA, Baldock J, Bird M,Brookes PC, Chenu C, Jastrow JD, Lal R, Lehmann J, O’DonnellAG, Parton WJ, Whitehead D, Zimmermann M (2013) Theknowns, known unknowns and unknowns of sequestration of soilorganic carbon. Agr, Ecosyst & Environ 164:80–99. doi:10.1016/j.agee.2012.10.001

49. Fargione J, Hill J, Tilman D, Polasky S, Hawthorne P (2008) Landclearing and the biofuel carbon debt. Science 319(5867):1235–1238. doi:10.1126/science.1152747

50. Anderson-Teixeira KJ, Davis SC, Masters MD, Delucia EH (2009)Changes in soil organic carbon under biofuel crops. Global ChangBiol Bioenergy 1(1):75–96

51. Kludze H, Deen B, Weersink A, van Acker R, Janovicek K, DeLaporte A (2013) Impact of land classification on potential warmseason grass biomass production in Ontario, Canada. Can J PlantSci 93(2):249–260

52. Stavi I, Lal R, Owens LB (2011) On-farm effects of no-till versusoccasional tillage on soil quality and crop yields in eastern Ohio.Agronomy Sust Developm 31(3):475–482. doi:10.1007/s13593-011-0006-4

53. Stehfest E, Bouwman L (2006) N2O and NO emission from agri-cultural fields and soils under natural vegetation: summarizingavailable measurement data and modeling of global annual emis-sions. Nutr Cycl Agroecosyst 74(3):207–228. doi:10.1007/s10705-006-9000-7

54. Bessou C, Ferchaud F, Gabrielle B, Mary B (2011) Biofuels, green-house gases and climate change. Sustainable Agriculture Volume 2.Springer, Dordrecht, pp 365–468

55. Djomo SN, Kasmioui OE, Ceulemans R (2011) Energy and green-house gas balance of bioenergy production from poplar and willow:a review. GCB Bioenergy 3(3):181–197. doi:10.1111/j.1757-1707.2010.01073.x

56. MolodovskayaM, Singurindy O, Richards BK,Warland J, JohnsonMS, Steenhuis TS (2012) Temporal variability of nitrous oxide fromfertilized croplands: hot moment analysis. Soil Sci Soc Am J 76(5):1728–1740

57. Fick G, Pfeifer R, Lathwell D (1994) Production patterns of peren-nial herbaceous biomass crops in the Great Lakes Region. EnergySources 16(3):333–348

58. VanGroenigen JW, Velthof GL, OenemaO, Van Groenigen KJ, VanKessel C (2010) Towards an agronomic assessment of N2O emis-sions: a case study for arable crops. Eur J Soil Sci 61(6):903–913.doi:10.1111/j.1365-2389.2009.01217.x

59. Vogel KP (1996) Energy production from forages (or Americanagriculture—back to the future). J Soil Water Conserv 51(2):137–139

60. Rothbart P, Capel S (2006) Chapter 3. Maintaining and restoringgrasslands. In: Oehler JD, Covell DR, S.Capel, Long B (eds)Managing grasslands, shrublands and young forests for wildlife, aguide for the Northeast. Northeast Upland Habitat Technical

Bioenerg. Res.

Committee, Massachusetts Division of Fisheries & Wildlife, http://www.rienvirothon.org/Managing_Shrublands__Grasslands_and_Young_Forests_for_Wildlife.pdf, pp 14–27

61. Salon P, Miller C (2012) A guide to: conservation plantings oncritical areas for the Northeast. USDA, NRCS, Big Flats PlantMaterials Center, Corning, NY, USA, http://www.nrcs.usda.gov/Internet /FSE_PLANTMATERIALS/publ ica t ions /nypmspu11417.pdf

62. Parrish DJ, Fike JH (2005) The biology and agronomy of switch-grass for biofuels. Crit Rev Plant Sci 24(5–6):423–459. doi:10.1080/07352680500316433

63. Casler M, Vogel K, Taliaferro C, Wynia R (2004) Latitudinaladaptation of switchgrass populations. Crop Sci 44(1):293–303

64. Casler MD, Vogel KP (2014) Selection for biomass yield in upland,lowland, and hybrid switchgrass. Crop Sci 54(2):626–636

65. Cortese LM, Bonos SA (2013) Bioenergy traits of ten switch-grass populations grown in the Northeastern/Mid-AtlanticUSA. BioEnergy Res 6(2):580–590. doi:10.1007/s12155-012-9271-6

66. Mayton H, Adler P, Casler M, Ernst C, Boe A, Bonos S (2013)Switchgrass and biodiversity mixture yields on prime and marginalland in the Northeast switchgrass II, Sep. 3–6, 2013, Madison, WI.

67. Vogel K, Mitchell R, Casler M, Sarath G (2014) Registration of‘Liberty’ switchgrass. Journal of Plant Registrations. doi: 10.3198/jpr2013.12.0076crc

68. Weimer PJ, Springer TL (2007) Fermentability of easterngamagrass, big bluestem and sand bluestem grown across a widevariety of environments. Bioresour Technol 98(8):1615–1621

69. Tubeileh A, Rennie TJ, Kerr A, Saita AA, Patanè C (2014) Biomassproduction by warm-season grasses as affected by nitrogen appli-cation in Ontario. Agron J 106(2):416–422. doi:10.2134/agronj2013.0379

70. Salon P, Dickerson J, Burgdorf D, Bush T, Miller C,Wark B,MaherR, Poole B (2011) Vegetating with native grasses in NortheasternNorth America. NRCS, http://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/nypmsbk10321.pdf

71. Mann JJ, Barney JN, Kyser GB, Di Tomaso JM (2013)Miscanthus×giganteus and Arundo donax shoot and rhizome tol-erance of extreme moisture stress. GCB Bioenergy 5(6):693–700.doi:10.1111/gcbb.12039

72. Naidu SL, Szarejko JM, Ramig KM, Portis AR, Long SP (2005)The exceptional low temperature tolerance of C4 photosynthesis inMiscanthus x giganteus corresponds to a lower activation energy ofRubisco. Plant Biology Annual Meeting, 16–20 Jul 2005, Seattle,WA, USA. Paper No. 262. http://abstracts.aspb.org/pb2005/public/P43/7406.html

73. Lee DK, Parrish AS, Voigt TB (2014) Switchgrass and giantmiscanthus agronomy. In: Shastri Y, Hansen A, Rodríguez L, TingKC (eds) Engineering and science of biomass feedstock productionand provision. Springer, New York, NY, USA, pp 37–59

74. Heaton EA, Boersma N, Caveny JD, Voigt TB, Dohleman FG(2012)Miscanthus (Miscanthus x giganteus) for biofuel production.Extension- America's Research-based Learning Network, http://www.extension.org/pages/26625/miscanthus-miscanthus-x-giganteus-for-biofuel-production

75. Heaton EA, Long SP, Voigt TB, Jones MB, Clifton-Brown J (2004)Miscanthus for renewable energy generation: European Union ex-perience and projections for Illinois. Mitig Adapt Strateg GlobChang 9(4):433–451

76. Miguez FE, Maughan M, Bollero GA, Long SP (2012) Modelingspatial and dynamic variation in growth, yield, and yield stability ofthe bioenergy crops Miscanthus×giganteus and Panicum virgatumacross the conterminous United States. GCB Bioenergy 4(5):509–520. doi:10.1111/j.1757-1707.2011.01150.x

77. Wrobel C, Coulman BE, Smith DL (2008) The potential use of reedcanarygrass (Phalaris arundinacea L.) as a biofuel crop. Acta

Agriculturae Scandinavica, Section B - Soil & Plant Sci 59(1):1–18. doi:10.1080/09064710801920230

78. Rice JS, Pinkerton BW (1993) Reed canarygrass survival undercyclic inundation. J Soil Water Conserv 48(2):132–135

79. Hallam A, Anderson IC, Buxton DR (2001) Comparative economicanalysis of perennial, annual, and intercrops for biomass production.Biomass Bioenergy 21(6):407–424

80. Douglas J, Lamunyon J, Wynia R, Salon P (2009) Planting andmanaging switchgrass as a biomass energy crop. USDA-NRCS,Washington, DC, USA, http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1042293.pdf

81. Jung JY, Lal R (2011) Impacts of nitrogen fertilization on biomassproduction of switchgrass (Panicum virgatum L.) and changes insoil organic carbon in Ohio. Geoderma 166(1):145–152

82. Richards BK, Stoof CR, Mason C, Crawford RV, Das S, Hansen JL,Mayton HS, Crawford JL, Steenhuis TS, Walter MT, Viands DR(2013) Carbon sequestration and gaseous emissions in perennialgrass bioenergy cropping systems in the Northeastern US,Proceedings of the AAIC Meeting USDA-NIFA session onCarbon Sequestration and Greenhouse Gas Emissions fromBioenergy Crops, Washington, DC, USA, 14 Oct 2013

83. Owens V, Viands D, Mayton H, Fike J, Farris R, Heaton E, BransbyD, Hong C (2013) Nitrogen use in switchgrass grown for bioenergyacross the USA. Biomass Bioenergy 58:286–293

84. Crouch JA, Beirn LA, Cortese LM, Bonos SA, Clarke BB(2009) Anthracnose disease of switchgrass caused by the novelfungal species Colletotrichum navitas Mycol Res 113(12):1411–1421

85. Waxman K, Bergstrom G (2011) First report of anthracnose causedby Colletotrichum navitas on switchgrass in New York. Plant Dis95(8):1032–1032

86. WaxmanK, BergstromG (2011) First report of a leaf spot caused byBipolaris oryzae on switchgrass in New York. Plant Dis 95(9):1192–1192

87. Volk TA, Abrahamson LP, Nowak CA, Smart LB, Tharakan PJ,White EH (2006) The development of short-rotation willow in thenortheastern United States for bioenergy and bioproducts, agrofor-estry and phytoremediation. Biomass and Bioenergy 30(8–9):715–727. doi:10.1016/j.biombioe.2006.03.001

88. Royle DJ, Ostry ME (1995) Disease and pest control in thebioenergy crops poplar and willow. Biomass and Bioenergy 9(1–5):69–79. doi:10.1016/0961-9534(95)00080-1

89. Tharakan PJ, Volk TA, Nowak CA, Abrahamson LP (2005)Morphological traits of 30 willow clones and their relationship tobiomass production. Can J For Res 35(2):421–431

90. Smart LB, Cameron KD (2008) Genetic improvement of willow(Salix spp.) as a dedicated bioenergy crop. In: Vermerris WE (ed)Genetic improvement of bioenergy crops. Springer Science, NewYork, NY, pp 347–376

91. Smart LB, Volk TA, Lin J, Kopp RF, Phillips IS, Cameron KD,White EH, Abrahamson LP (2005) Genetic improvement of shrubwillow (Salix spp.) crops for bioenergy and environmental applica-tions in the United States. Unasylva (English ed) 56(221):51–55

92. Smart LB, Cameron KD (2012) Shrub willow. In: Kole C, Joshi S,Shonnard D (eds) Handbook of bioenergy crop plants. Taylor andFrancis Group, Boca Raton, FL, pp 687–708

93. Volk TA, Abrahamson LP, Cameron KD, Castellano P, Corbin T,Fabio E, Johnson G, Kuzovkina-Eischen Y, Labrecque M,Miller R,Sidders D, Smart LB, Staver K, Stanosz GR, Van Rees K (2011)Yields of willow biomass crops across a range of sites in NorthAmerica. Asp Appl Biol 112:67–74

94. Serapiglia MJ, Gouker FE, Smart LB (2014) Early selection ofnovel triploid hybrids of shrub willow with improved biomass yieldrelative to diploids. BMC Plant Biol 14(1):74

95. Fillion M, Brisson J, Teodorescu TI, Sauve S, Labrecque M (2009)Performance of Salix viminalis and Populus nigra x Populus

Bioenerg. Res.

maximowiczii in short rotation intensive culture under high irriga-tion. Biomass & Bioenergy 33(9):1271–1277. doi:10.1016/j.biombioe.2009.05.011

96. Guidi W, Labrecque M (2010) Effects of high water supply ongrowth, water use, and nutrient allocation in willow and poplargrown in a 1-year pot trial. Water Air Soil Pollut 207(1–4):85–101. doi:10.1007/s11270-009-0121-x

97. Serapiglia MJ, Cameron KD, Stipanovic AJ, Abrahamson LP, VolkTA, Smart LB (2013) Yield andwoody biomass traits of novel shrubwillow hybrids at two contrasting sites. BioEnergy Res 6:533–546.doi:10.1007/s12155-012-9272-5

98. Hanley SJ, Karp A (2013) Genetic strategies for dissecting complextraits in biomass willows (Salix spp.). Tree physiology: tpt089

99. McCracken AR, Walsh L, Moore PJ, Lynch M, Cowan P, DawsonM, Watson S (2011) Yield of willow (Salix spp.) grown in shortrotation coppice mixtures in a long-term trial. Ann Appl Biol159(2):229–243. doi:10.1111/j.1744-7348.2011.00488.x

100. WeihM, Nordh N-E (2002) Characterising willows for biomass andphytoremediation: growth, nitrogen and water use of 14 willowclones under different irrigation and fertilisation regimes. BiomassBioenergy 23(6):397–413

101. Buchholz T, Volk TA (2011) Improving the profitability of willowcrops-identifying opportunities with a crop budget model.BioEnergy Res 4(2):85–95. doi:10.1007/s12155-010-9103-5

102. Heilman P, Norby RJ (1998) Nutrient cycling and fertility manage-ment in temperate short rotation forest systems. Biomass andBioenergy 14(4):361–370. doi:10.1016/S0961-9534(97)10072-1

103. Jug A, Makeschin F, Rehfuess KE, Hofmann-Schielle C (1999)Short-rotation plantations of balsam poplars, aspen and willows onformer arable land in the Federal Republic of Germany. III Soilecological effects Forest Ecology and Management 121(1–2):85–99. doi:10.1016/S0378-1127(98)00558-1

104. Ens J, Farrell RE, Belanger N (2013) Early effects of afforestationwith willow (Salix purpurea, ‘Hotel’) on soil carbon and nutrientavailability. Forests 4(1):137–154. doi:10.3390/f4010137

105. Adegbidi HG, Volk TA, White EH, Abrahamson LP, Briggs RD,Bickelhaupt DH (2001) Biomass and nutrient removal by willowclones in experimental bioenergy plantations in New York State.Biomass Bioenergy 20(6):399–411. doi:10.1016/s0961-9534(01)00009-5

106. Jug A, Hofmann-Schielle C, Makeschin F, Rehfuess KE (1999)Short-rotation plantations of balsam poplars, aspen and willows onformer arable land in the Federal Republic of Germany. IINutritional status and bioelement export by harvested shoot axes.For Ecol and Manag 121(1–2):67–83. doi:10.1016/s0378-1127(98)00557-x

107. Mitchell CP, Stevens EA, Watters MP (1999) Short-rotation forest-ry—operations, productivity and costs based on experience gainedin the UK. For Ecol and Manag 121(1–2):123–136. doi:10.1016/S0378-1127(98)00561-1

108. Hangs RD, Schoenau JJ, Van Rees KCJ, Knight JD (2012) Theeffect of irrigation on nitrogen uptake and use efficiency of twowillow (Salix spp.) biomass energy varieties. Can J Plant Sci 92(3):563–575. doi:10.4141/cjps2011-245

109. Caputo J, Balogh S, Volk T, Johnson L, Puettmann M, LippkeB, Oneil E (2014) Incorporating uncertainty into a life cycleassessment (LCA) model of short-rotation willow biomass(Salix spp.) crops. BioEnergy 7(1):48–59. doi:10.1007/s12155-013-9347-y

110. Baxter LL, Miles TR,Miles TR Jr, Jenkins BM,Milne T, Dayton D,Bryers RW, Oden LL (1998) The behavior of inorganic material inbiomass-fired power boilers: field and laboratory experiences. FuelProcess Technol 54(1):47–78

111. Cherney JH, Cherney DJR, Bruulsema TW (1998) Potassium man-agement. In: Cherney DJR, Cherney JH (eds) Grass for dairy cattle.CABI, New York, NY, pp 137–160

112. Samson R, Mani S, Boddey R, Sokhansanj S, Quesada D,Urquiaga S, Reis V, Ho Lem C (2005) The potential of C4perennial grasses for developing a global BIOHEAT industry.BPTS 24(5–6):461–495

113. Hadders G, Olsson R (1997) Harvest of grass for combustion in latesummer and in spring. Biomass Bioenergy 12(3):171–175

114. Tonn B, Thumm U, Lewandowski I, Claupein W (2012) Leachingof biomass from semi-natural grasslands—effects on chemical com-position and ash high-temperature behaviour. Biomass Bioenergy36:390–403

115. Tumuluru JS, Wright CT, Hess JR, Kenney KL (2011) A review ofbiomass densification systems to develop uniform feedstock com-modities for bioenergy application. Biofuels Bioprod Biorefin 5(6):683–707

116. Chandrasekaran SR, Hopke PK, Newtown M, Hurlbut A (2013)Residential-scale biomass boiler emissions and efficiency character-ization for several fuels. Energy Fuel 27(8):4840–4849

117. CEN (2012) EN 14961-6, Solid biofuels—fuel specifications andclasses—Part 6: Non-woody pellets for non-industrial use.European Committee for Standardization, Brussels

118. Cherney JH, Verma VK (2013) Grass pellet Quality Index: a tool toevaluate suitability of grass pellets for small scale combustionsystems. Applied Energy 103:679–684. doi:10.1016/j.apenergy.2012.10.050

119. Schmidl C, Luisser M, Padouvas E, Lasselsberger L, Rzaca M,Ramirez-Santa Cruz C, Handler M, Peng G, Bauer H, Puxbaum H(2011) Particulate and gaseous emissions from manually and auto-matically fired small scale combustion systems. Atmos Environ45(39):7443–7454

120. Verma V, Bram S, De Ruyck J (2009) Small scale biomass heatingsystems: standards, quality labelling andmarket driving factors—anEU outlook. Biomass Bioenergy 33(10):1393–1402

121. Verma V, Bram S, Delattin F, Laha P, Vandendael I, Hubin A, DeRuyck J (2012) Agro-pellets for domestic heating boilers: standardlaboratory and real life performance. Appl Energy 90(1):17–23

122. Gonzalez JF, Gonzalez-Garcia CM, Ramiro A, Gonzalez J, Sabio E,Gañan J, Rodriguez MA (2004) Combustion optimisation of bio-mass residue pellets for domestic heating with a mural boiler.Biomass Bioenergy 27(2):145–154

123. JeguirimM, Dorge S, Trouve G (2010) Thermogravimetric analysisand emission characteristics of two energy crops in air atmosphere:Arundo donax and Miscanthus giganthus. Bioresour Technol101(2):788–793

124. Chandrasekaran SR, Hopke PK, Hurlbut A, Newtown M (2013)Characterization of emissions from grass pellet combustion. EnergyFuel 27(9):5298–5306

125. Kenney W, Sennerby-Forsse L, Layton P (1990) A review ofbiomass quality research relevant to the use of poplar and willowfor energy conversion. Biomass 21(3):163–188

126. Tharakan PJ, Volk TA, Abrahamson LP, White EH (2003) Energyfeedstock characteristics of willow and hybrid poplar clones atharvest age. Biomass and Bioenergy 25(6):571–580. doi:10.1016/S0961-9534(03)00054-0

127. Woodcock D, Shier A (2003) Does canopy position affect woodspecific gravity in temperate forest trees? Ann Bot 91(5):529–537

128. White RH (1987) Effect of lignin content and extractives on thehigher heating value of wood. Wood Fiber Sci 19(4):446–452

129. Miles TR, Miles TR, Jr., Baxter LL, Bryers RW, Jenkins BM, OdenLL (1996) Alkali deposits found in biomass power plants. A pre-liminary investigation of their extent and nature, http://www.nrel.gov/docs/legosti/fy96/8142v1.pdf edn. Report NREL/TP-433-8142, National Renewable Energy Laboratory, Golden, CO, USA

130. Eisenbies M, Volk T, Abrahamson L, Shuren R, Stanton B,Posselius J, McArdle M, Karapetyan S, Patel A, Shi S, Serpa. J(in review) Development and deployment of a short rotation woodycrops harvesting system based on a Case New Holland Forage

Bioenerg. Res.

Harvester and SRC Woody Crop Header. Final report for USDOEproject DE-EE0001037

131. ISO (2013) Solid biofuels-fuel specifications and classes—Part 4:graded wood chips. ISO/FDIS 17225–4:2013(E), Geneva,Switzerland

132. Gillespie GD, Everard CD, Fagan CC, McDonnell KP (2013)Prediction of quality parameters of biomass pellets from proximateand ultimate analysis. Fuel 111:771–777. doi:10.1016/j.fuel.2013.05.002

133. Lam PK, Lam PY, Sokhansanj S, Bi X, Lim C, Sidders D, Melin S(2010) Evaluation of hybrid poplar and salix (Salix) biomass forpellet production, ASABE, 2010 Pittsburgh, Pennsylvania, June20–June 23, 2010, paper no. 1009799

134. Pellet Fuels Institute (2011) Standard specifications for residential/commercial densified fuel, http://pelletheat.org/wp-content/uploads/2011/11/PFI-Standard-Specification-November-2011.pdf

135. NYSDOH (2013) Fine particulate matter concentrations in outdoorair near outdoor wood-fired boilers (OWBs). New York StateDepartment of Health, Bureau of Toxic Substance Assessment,https://www.health.ny.gov/environmental/outdoors/air/owb/docs/owb_report.pdf

136. EPA (2014) Partners Program Participation. United StatesEnvironmental Protection Agency, http://www.epa.gov/burnwise/participation.html

137. EPA (2014) 40 CFR Part 60. Standards of performance for newresidential wood heaters, new residential hydronic heaters andforced-air furnaces, and new residential masonry heaters.Proposed Rule Fed Regist 79(22):6329–6416

138. Burkhard E, Albrecht R (2008) Biomass combustion in Europe:overview of technologies and regulations. New York State EnergyResearch and Development Authority, Albany, NY, USA,NYSERDA Final Report 08–03, April, 2008

139. NYSERDA (2013) New York State Renewable Portfolio StandardPerformance Report, http://www.nyserda.ny.gov/Publications/Program-Planning-Status-and-Evaluation-Reports/Renewable-Portfolio-Standard-Reports.aspx

140. FSA (2013) FSA Handbook Agricultural Resource ConservationProgram 2-CRP (Revision 5, Amendment 17). United StatesDepartment of Agriculture, Farm Service Agency, http://www.fsa.usda.gov/Internet/FSA_File/2-crp_r05_a17.pdf

141. EPA (2014) Questions and answers on changes to the RenewableFuel Standard Program (RFS2). US Environmental ProtectionAgency, http://www.epa.gov/otaq/fuels/renewablefuels/compliancehelp/rfs2-aq.htm

142. EPAct (2005) Energy Policy Act of 2005, Section 203. US PublicLaw 109-58-Aug. 8, 2005. http://energy.gov/sites/prod/files/2013/10/f3/epact_2005.pdf

143. NYS (1976) Energy Law, Section 1–103. New York State144. FSA (2012) FSA Handbook Biomass Crop Assistance Program (1-

BCAP) Amendment 3. United States Department of Agriculture,Farm Service Agency, http://www.fsa.usda.gov/Internet/FSA_File/1-bcap_r00_a03.pdf

145. FSA (2011) Fact Sheet Biomass Crop Assistance Program (BCAP).United States Department of Agriculture, Farm Service Agency,https://www.fsa.usda.gov/Internet/FSA_File/bcap_update_may2011.pdf

146. FSA (2012) Fact Sheet Biomass CropAssistance Program—ProjectArea Number 10. United States Department of Agriculture, FarmService Agency, https://www.fsa.usda.gov/Internet/FSA_File/bcap_proj10.pdf

147. de Vries SC, van de Ven GW, van Ittersum MK, Giller KE (2010)Resource use efficiency and environmental performance of ninemajor biofuel crops, processed by first-generation conversion tech-niques. Biomass Bioenergy 34(5):588–601

148. Dhondt AA, Wrege PH, Cerretani J, Sydenstricker KV (2007)Avian species richness and reproduction in short-rotation cop-pice habitats in central and western New York: capsule speciesrichness and density increase rapidly with coppice age, and aresimilar to estimates from early successional habitats. Bird Study54(1):12–22

149. Dauber J, Jones MB, Stout JC (2010) The impact of biomass cropcultivation on temperate biodiversity. GCB Bioenergy 2(6):289–309. doi:10.1111/j.1757-1707.2010.01058.x

150. Mayton H, Hansen J, Salon P, Ahmed Z, Woodbury P, Crawford R,Viands D (2014)Genotype by environment interactions of perennialgrass yields across locations and years in New York State (acceptedwith revisions). BioEnergy Res

151. Adler P, Sanderson M, Goslee S (2004) Management and compo-sition of conservation lands in the Northeastern United States InProceedings of the 4th Eastern Native Grass Symposium,Lexington, KY October 3–6 2004

152. Bosworth S, Kelly T, Monahan S (2013) Nitrogen fertilization, timeof harvest, and soil drainage effects on switchgrass biomass pro-duction and fuel quality. 2010–2012. University of VermontExtension, http://pss.uvm.edu/vtcrops/articles/EnergyCrops/Switchgrass_Nitrogen_And_Nutrient_Removal.pdf

153. Adegbidi HG, Briggs RD, Volk TA, White EH, Abrahamson LP(2003) Effect of organic amendments and slow-release nitrogenfertilizer on willow biomass production and soil chemical charac-teristics. Biomass and Bioenergy 25(4):389–398. doi:10.1016/S0961-9534(03)00038-2

154. Cavanagh A, Gasser MO, Labrecque M (2011) Pig slurry as fertil-izer on willow plantation. Biomass Bioenergy 35(10):4165–4173.doi:10.1016/j.biombioe.2011.06.037

155. Kopp RF, Abrahamson LP, White EH, Nowak CA, Zsuffa L, BurnsKF (1996) Woodgrass spacing and fertilization effects on woodbiomass production by a willow clone. Biomass Bioenergy 11(6):451–457. doi:10.1016/s0961-9534(96)00055-4

156. Labrecque M, Teodorescu TI, Daigle S (1998) Early perfor-mance and nutrition of two willow species in short-rotationintensive culture fertilized with wastewater sludge and impacton the soil characteristics. Can J For Res-Revue Canadienne DeRecherche Forestiere 28(11):1621–1635. doi:10.1139/cjfr-28-11-1621

157. Quaye AK, Volk TA, Hafner S, Leopold DJ, Schirmer C (2011)Impacts of paper sludge andmanure on soil and biomass productionof willow. Biomass Bioenergy 35(7):2796–2806. doi:10.1016/j.biombioe.2011.03.008

158. Quaye AK, Volk TA (2013) Biomass production and soil nutrientsin organic and inorganic fertilized willow biomass production sys-tems. Biomass and Bioenergy 57:113–125. doi:10.1016/j.biombioe.2013.08.002

Bioenerg. Res.