Biochar for Environmental Management: An Introduction · Simply put, biochar is the carbon-rich prod-uct obtained when biomass, such as wood, manure or leaves, is heated in a closed

Simply put, biochar is the carbon-rich prod-uct obtained when biomass, such as wood,manure or leaves, is heated in a closedcontainer with little or no available air. Inmore technical terms, biochar is produced byso-called thermal decomposition of organicmaterial under limited supply of oxygen (O2),and at relatively low temperatures (<700°C).This process often mirrors the production ofcharcoal, which is one of the most ancientindustrial technologies developed by mankind– if not the oldest (Harris, 1999). However, itdistinguishes itself from charcoal and similarmaterials that are discussed below by the factthat biochar is produced with the intent to beapplied to soil as a means of improving soilproductivity, carbon (C) storage, or filtrationof percolating soil water. The productionprocess, together with the intended use, typi-cally forms the basis for its classification andnaming convention, which is discussed in thenext section.

In contrast to the organic C-rich biochar,burning biomass in a fire creates ash, which

mainly contains minerals such as calcium(Ca) or magnesium (Mg) and inorganiccarbonates. Also, in most fires, a smallportion of the vegetation is only partiallyburned in areas of limited O2 supply, with aportion remaining as char (Kuhlbusch andCrutzen, 1995).

The question as to what biochar actuallyis from a chemical point of view rather thanfrom a production point of view is muchmore difficult to answer due to the wide vari-ety of biomass and charring conditions used.The defining property is that the organicportion of biochar has a high C content,which mainly comprises so-called aromaticcompounds characterized by rings of six Catoms linked together without O or hydrogen(H), the otherwise more abundant atoms inliving organic matter. If these aromatic ringswere arranged in perfectly stacked andaligned sheets, this substance would be calledgraphite. Under temperatures that are usedfor making biochar, graphite does not form toany significant extent. Instead, much more

What is biochar?

1

Biochar for Environmental Management:An Introduction

Johannes Lehmann and Stephen Joseph

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irregular arrangements of C will form,containing O and H and, in some cases,minerals depending upon the feedstock. Untilnow, biochar-type materials have largelyescaped full characterization due to theircomplexity and variability (Schmidt andNoack, 2000). One of the first attempts tocharacterize the crystal structure of graphitewas undertaken in the 1920s by John D.Bernal. Using X-ray diffraction, Bernal(1924) demonstrated the hexagonal structureand layering of graphene sheets in a puregraphite crystal (see Figure 1.1).The muchmore irregular biochar-type organic matterwas only successfully investigated much laterby Rosalind Franklin in the late 1940s(Franklin, 1950, 1951), and efforts to charac-terize the chemistry of biochar are ongoingand are discussed in detail in Chapters 2 to 4.

2 BIOCHAR FOR ENVIRONMENTAL MANAGEMENT

Figure 1.1 Structure of graphite as proven forthe first time by J. D. Bernal in 1924

Source: Bernal (1924), with permission from the publisher andthe estate

Biochar terminology

The term ‘biochar’ is a relatively recent devel-opment, emerging in conjunction with soilmanagement and C sequestration issues(Lehmann et al, 2006). This publicationestablishes and uses ‘biochar’ as the appropri-ate term where charred organic matter isapplied to soil in a deliberate manner, withthe intent to improve soil properties. Thisdistinguishes biochar from charcoal that isused as fuel for heat, as a filter, as a reductantin iron-making or as a colouring agent inindustry or art (see historical definitions inChapter 7).

The term ‘biochar’ has previously beenused in connection with charcoal production(e.g., Karaosmanoglu et al, 2000; Demirbas,2004a). The rationale for avoiding the term‘charcoal’ when discussing fuel may stemfrom the intent to distinguish it from coal.Indeed, coal is formed very differently fromcharcoal and has separate chemical and phys-ical properties, although in very specific casesthe differences in properties can become

blurred (see Chapter 17). In spite of this, theterm ‘charcoal’ is long established in popularlanguage and the scientific literature, and willalso be used in this book for charred organicmatter as a source of energy.

The establishment of the term ‘agrichar’is closely related to that of biochar, with thedesire to apply charred organic matter to soil,but is not used further in this book. ‘Biochar’is preferred here as it includes the applicationof charred organic matter in settings outsideof agriculture, such as promoting soil remedi-ation or other environmental services. Andthe term emphasizes biological origin, distin-guishing it from charred plastics or othernon-biological material.

‘Char’ is a term that is often used inter-changeably with charcoal, but is sometimesapplied to refer to a material that is charred toa lesser extent than charcoal, typically as aproduct of fire (Schmidt and Noack, 2000).The term is used in this book to refer to thecharred residue of vegetation fires. Both

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terms, char and charcoal, are extensivelyemployed in this volume because much of theavailable information on charred organicmatter has been generated in studies on char-coal production for fuel and on char as aresult of fires. In most instances, this body ofliterature provides information that is rele-vant to biochar management.

‘Activated carbon’ is a term used forbiochar-type substances, as well as for coal,that have been ‘activated’ in various waysusing, for example, steam or chemicals, oftenat high temperature (>700°C) (Boehm,1994). This process is intended to increasethe surface area (see Chapter 2) for use inindustrial processes such as filtration.

The term ‘black C’ is much wider andincludes all C-rich residues from fire or heat.Fossil fuels such as coal, gas and petrol, aswell as biomass, can produce black C. Theterm includes the solid carbonaceous residueof combustion and heat, as well as thecondensation products, known as soot. BlackC includes the entire spectrum of charredmaterials, ranging from char, charcoal andbiochar, to soot, graphitic black C andgraphite (Schmidt and Noack, 2000).

The term ‘charring’ is used either inconnection with making charcoal or inconnection with char originating from fires.

The term ‘pyrolysis’ is typically used eitherfor analytical procedures to investigate theorganic chemistry of organic substances(Leinweber and Schulten, 1999) or forbioenergy systems that capture the off-gasesemitted during charring and used to producehydrogen, syngas, bio-oils, heat or electricity(Bridgwater et al, 1999). In contrast, the term‘burning’ is typically used if no char remains,with the organic substrate being entirelytransformed to ash that does not containorganic C. Often, substances called ‘ash’ inreality contain some char or biochar, signifi-cantly influencing ash properties andbehaviour in technology and the environ-ment.

Burning is very different from charringand pyrolysis, not only with respect to thesolid ash residue versus biochar and relatedsubstances, but in terms of the gaseous prod-ucts that are generated.Therefore, these twoprocesses should be carefully distinguishedfrom each other.

The terminology surrounding biocharmay evolve. However, the definition providedhere serves as a starting point for futuredevelopment. Other terms such as gasifica-tion or liquefaction that are used inconjunction with biochar are explained else-where (Peacocke and Joseph, undated).

BIOCHAR FOR ENVIRONMENTAL MANAGEMENT 3

The origin of biochar management and research

While both research and development ofbiochar for environmental management at aglobal scale is a somewhat recent develop-ment, it is by no means new in certain regionsand has even been the subject of scientificresearch for quite some time. For example,Trimble (1851) shared observations of‘evidence upon almost every farm in thecounty in which I live, of the effect of char-coal dust in increasing and quickeningvegetation’. Early research on the effects ofbiochar on seedling growth (Retan, 1915)

and soil chemistry (Tryon, 1948) yieldeddetailed scientific information. In Japan,biochar research significantly intensifiedduring the early 1980s (Kishimoto andSugiura, 1980, 1985).

The use of biochar has, for some time,been recommended in various horticulturalcontexts – for example, as a substrate forpotting mix (Santiago and Santiago, 1989).In 1927, Morley (1927) writes in the firstissue of The National Greenkeeper that ‘char-coal acts as a sponge in the soil, absorbing

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and retaining water, gases and solutions’. Heeven remarks that ‘as a purifier of the soil andan absorber of moisture, charcoal has noequal’ (Morley, 1929), and charcoal productsare being marketed for turf applications in a1933 issue of the same magazine (see Figure1.2). Young (1804) discusses a practice of‘paring and burning’ where soil is heapedonto organic matter (often peat) after settingit on fire with reportedly significant increasesin farm revenue. Also, Justus Liebig describesa practice in China where waste biomass wasmixed and covered with soil, and set on fire toburn over several days until a black earth isproduced, which reportedly improved plantvigour (Liebig, 1878, p452). According toOgawa (undated), biochar is described byMiyazaki as ‘fire manure’ in an ancientJapanese text on agriculture dating from1697 (pp91–104). Despite these earlydescriptions and research, global interest inbiochar only began in the past few years.

The basis for the strong recent interest inbiochar is twofold. First, the discovery thatbiochar-type substances are the explanationfor high amounts of organic C (Glaser et al,2001) and sustained fertility in AmazonianDark Earths locally known as Terra Preta deIndio (Lehmann et al, 2003a). Justifiably or

not, biochar has, as a consequence, beenfrequently connected to soil managementpractised by ancient Amerindian populationsbefore the arrival of Europeans, and to thedevelopment of complex civilizations in theAmazon region (Petersen et al, 2001). Thisproposed association has found widespreadsupport through the appealing notion ofindigenous wisdom rediscovered. Irrespectiveof such assumptions, fundamental scientificresearch of Terra Preta has also yieldedimportant basic information on the function-ing of soils, in general, and on the effects ofbiochar, in particular (Lehmann, 2009).

Second, over the past five years, unequiv-ocal proof has become available showing thatbiochar is not only more stable than any otheramendment to soil (see Chapter 11), and thatit increases nutrient availability beyond afertilizer effect (see Chapter 5; Lehmann,2009), but that these basic properties ofstability and capacity to hold nutrients arefundamentally more effective than those ofother organic matter in soil.This means thatbiochar is not merely another type ofcompost or manure that improves soil prop-erties, but is much more efficient atenhancing soil quality than any other organicsoil amendment. And this ability is rooted in


Figure 1.2 Advertisement forbiochar to be used as a soil amendment in turf greens

Source: The National Greenkeeper (1933)

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specific chemical and physical properties,such as the high charge density (Liang et al,2006), that result in much greater nutrientretention (Lehmann et al, 2003b), and itsparticulate nature (Skjemstad et al, 1996;Lehmann et al, 2005) in combination with aspecific chemical structure (Baldock andSmernik, 2002) that provides much greaterresistance to microbial decay than other soilorganic matter (Shindo, 1991; Cheng et al,

2008).These and similar investigations havehelped to make a convincing case for biocharas a significant tool for environmentalmanagement.They have provided the break-through that has brought already existing –yet either specialized or regionally limited –biochar applications and isolated researchefforts to a new level.This book is a testamentto these expanding activities and their resultsto date.


The big picture

Four complementary and often synergisticobjectives may motivate biochar applicationsfor environmental management: soil im-provement (for improved productivity as wellas reduced pollution); waste management;climate change mitigation; and energyproduction (see Figure 1.3), which individu-ally or in combination must have either asocial or a financial benefit or both. As aresult, very different biochar systems emergeon different scales (see Chapter 9). Thesesystems may require different production

systems that do or do not produce energy inaddition to biochar, and range from smallhousehold units to large bioenergy powerplants (see Chapter 8). The followingsections provide a brief introduction into thebroad areas that motivate implementation ofbiochar, leading to more detailed informationpresented in the individual chapters through-out this book.

Biochar as a soil amendmentSoil improvement is not a luxury but a neces-sity in many regions of the world. Lack offood security is especially common in sub-Saharan Africa and South Asia, withmalnutrition in 32 and 22 per cent of the totalpopulation, respectively (FAO, 2006).Whilemalnutrition decreased in many countriesworldwide from 1990–1992 to 2001–2003,many nations in Asia, Africa or LatinAmerica have seen increases (FAO, 2006).The ‘Green Revolution’ initiated by NobelLaureate Norman Borlaug at theInternational Centre for Maize and WheatImprovement (CIMMYT) in Mexico duringthe 1940s had great success in increasingagricultural productivity in Latin Americaand Asia.These successes were mainly basedon better agricultural technology, such asimproved crop varieties, irrigation, and inputof fertilizers and pesticides. Sustainable soil

Figure 1.3 Motivation for applying biochartechnology

Source: Johannes Lehmann

Mitigation ofclimate change

Energyproduction

Wastemanagement

Soilimprovement

Social, financial benefits

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management has only recently beendemanded to create a ‘Doubly GreenRevolution’ that includes conservation tech-nologies (Tilman, 1998; Conway, 1999).Biochar provides great opportunities to turnthe Green Revolution into sustainable agro-ecosystem practice. Good returns on evermore expensive inputs such as fertilizers relyon appropriate levels of soil organic matter,which can be secured by biochar soilmanagement for the long term (Kimetu et al,2008; Steiner et al, 2007).

Specifically in Africa, the GreenRevolution has not had sufficient success(Evenson and Gollin, 2003), to a significantextent due to high costs of agrochemicals(Sanchez, 2002), among other reasons(Evenson and Gollin, 2003). Biocharprovides a unique opportunity to improvesoil fertility and nutrient-use efficiency usinglocally available and renewable materials in asustainable way. Adoption of biocharmanagement does not require new resources,but makes more efficient and more environ-mentally conscious use of existing resources.Farmers in resource-constrained agro-ecosystems are able to convert organicresidues and biomass fuels into biochar with-out compromising energy yield whiledelivering rapid return on investment (seeChapter 9).

In both industrialized and developingcountries, soil loss and degradation is occur-ring at unprecedented rates (Stocking, 2003;IAASTD, 2008), with profound conse-quences for soil ecosystem properties(Matson et al, 1997). In many regions, loss insoil productivity occurs despite intensive useof agrochemicals, concurrent with adverseenvironmental impact on soil and waterresources (Foley et al, 2005; Robertson andSwinton, 2005). Biochar is able to play amajor role in expanding options for sustain-able soil management by improving uponexisting best management practices, not onlyto improve soil productivity (see Chapters 5

and 12), but also to decrease environmentalimpact on soil and water resources (seeChapters 15 and 16). Biochar should there-fore not be seen as an alternative to existingsoil management, but as a valuable additionthat facilitates the development of sustainableland use: creating a truly green ‘BiocharRevolution’.

Biochar to manage wastesManaging animal and crop wastes from agri-culture poses a significant environmentalburden that leads to pollution of ground andsurface waters (Carpenter et al, 1998;Matteson and Jenkins, 2007). These wastesas well as other by-products are usableresources for pyrolysis bioenergy(Bridgwater et al, 1999; Bridgwater, 2003).Not only can energy be obtained in theprocess of charring, but the volume andespecially weight of the waste material issignificantly reduced (see Chapter 8), whichis an important aspect, for example, inmanaging livestock wastes (Cantrell et al,2007). Similar opportunities exist for greenurban wastes or certain clean industrialwastes such as those from paper mills (seeChapter 9; Demirbas, 2002). At times, manyof these waste or organic by-products offereconomic opportunities, with a significantreliable source of feedstock generated at asingle point location (Matteson and Jenkins,2007). Costs and revenues associated withaccepting wastes and by-products are,however, subject to market development andare difficult to predict. In addition, appropri-ate management of organic wastes can helpin the mitigation of climate change indirectlyby:

• decreasing methane emissions from land-fill;

• reducing industrial energy use and emis-sions due to recycling and wastereduction;

• recovering energy from waste;


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• enhancing C sequestration in forests dueto decreased demand for virgin paper;and

• decreasing energy used in long-distancetransport of waste (Ackerman, 2000).

Strict quality controls have to be applied forbiochar, particularly for those produced fromwaste, but also from other feedstocks.Pathogens that may pose challenges to directsoil application of animal manures (Bicudoand Goyal, 2003) or sewage sludge (Westrellet al, 2004) are removed by pyrolysis, whichtypically operates above 350°C and is thus avaluable alternative to direct soil application.Contents of heavy metals can be a concern insewage sludge and some specific industrialwastes, and should be avoided. However,biochar applications are, in contrast tomanure or compost applications, not prima-rily a fertilizer, which has to be appliedannually. Due to the longevity of biochar insoil, accumulation of heavy metals byrepeated and regular applications over longperiods of time that can occur for other soiladditions may not occur with biochar.

Biochar to produce energyCapturing energy during biochar productionand, conversely, using the biochar generatedduring pyrolysis bioenergy production as asoil amendment is mutually beneficial forsecuring the production base for generatingthe biomass (Lehmann, 2007a), as well as forreducing overall emissions (see Chapter 18;Gaunt and Lehmann, 2008). Adding biocharto soil instead of using it as a fuel does,indeed, reduce the energy efficiency of pyr-olysis bioenergy production; however, theemission reductions associated with biocharadditions to soil appear to be greater than thefossil fuel offset in its use as fuel (Gaunt andLehmann, 2008). A biochar vision is there-fore especially effective in offering

environmental solutions, rather than solelyproducing energy.

This appears to be an appropriateapproach for bioenergy as a whole. In fact,bioenergy, in general, and pyrolysis, in partic-ular, may contribute significantly to securinga future supply of green energy. However, itwill, most likely, not be able to solve theenergy crises and satisfy rising globaldemand for energy on its own. For example,Kim and Dale (2004) estimated the globalpotential to produce ethanol from crop wasteto offset 32 per cent of gasoline consumptionat the time of the study. This potential willmost likely never be achieved. An assessmentof the global potential of bioenergy fromforestry yielded a theoretical surplus supplyof 71EJ in addition to other wood needs for2050 (Smeets and Faaij, 2006), in compari-son to a worldwide energy consumption of489EJ in 2005 (EIA, 2007). If economicaland ecological constraints were applied, theprojection for available wood significantlydecreases (Smeets and Faaij, 2006).However, even a fraction of the global poten-tial will be an important contribution to anoverall energy solution. On its own, however,it will probably not satisfy future globalenergy demand.

In regions that rely on biomass energy, asis the case for most of rural Africa as well aslarge areas in Asia and Latin America, pyroly-sis bioenergy provides opportunities for moreefficient energy production than wood burn-ing (Demirbas, 2004b). It also widens theoptions for the types of biomass that can beused for generating energy, going beyondwood to include, for example, crop residues.A main benefit may be that pyrolysis offersclean heat, which is needed to develop cook-ing technology with lower indoor pollution bysmoke (Bhattacharya and Abdul Salam,2002) than is typically generated during theburning of biomass (Bailis et al, 2005) (seeChapter 20).


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Biochar to mitigate climate changeAdding biochar to soils has been described asa means of sequestering atmospheric carbondioxide (CO2) (Lehmann et al, 2006). Forthis to represent true sequestration, tworequirements have to be met. First, plantshave to be grown at the same rate as they arebeing charred because the actual step fromatmospheric CO2 to an organic C form isdelivered by photosynthesis in plants. Yet,plant biomass that is formed on an annualbasis typically decomposes rapidly. Thisdecomposition releases the CO2 that wasfixed by the plants back to the atmosphere. Incontrast, transforming this biomass intobiochar that decomposes much more slowlydiverts C from the rapid biological cycle intoa much slower biochar cycle (Lehmann,2007b). Second, the biochar needs to be trulymore stable than the biomass from which itwas formed.This seems to be the case and issupported by scientific evidence (seeChapter 11).

Several approaches have been taken toprovide first estimates of the large-scalepotential of biochar sequestration to reduceatmospheric CO2 (Lehmann et al, 2006;Lehmann, 2007b; Laird, 2008), which willneed to be vetted against economic (seeChapters 19 and 20) and ecologicalconstraints and extended to include a fullemission balance (see Chapter 18). Suchemission balances require a comparison to abaseline scenario, showing what emissionshave been reduced by changing to a systemthat utilizes biochar sequestration. Until moredetailed studies based on concrete locationsreach the information density required toextrapolate to the global scale, a simplecomparison between global C fluxes mayneed to suffice to demonstrate the potentialof biochar sequestration (see Figure 1.4).Almost four times more organic C is stored inthe Earth’s soils than in atmospheric CO2.And every 14 years, the entire atmosphericCO2 has cycled once through the biosphere(see Figure 1.4). Furthermore, the annual


Figure 1.4 The global carbon cycle ofnet primary productivity (total netphotosynthesis flux from atmosphere into plants) and release to the atmosphere from soil (by microorganismsdecomposing organic matter) in comparison to total amounts of carbon in soil, plant and atmosphere, and anthropogenic carbon emissions (sum offossil fuel emissions and land-use change)

Source: data from Sabine et al (2004)

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uptake of CO2 by plants is eight times greaterthan today’s anthropogenic CO2 emissions.This means that large amounts of CO2 arecycling between atmosphere and plants on anannual basis and most of the world’s organicC is already stored in soil. Diverting only asmall proportion of this large amount ofcycling C into a biochar cycle would make a

large difference to atmospheric CO2 concen-trations, but very little difference to the globalsoil C storage. Diverting merely 1 per cent ofannual net plant uptake into biochar wouldmitigate almost 10 per cent of currentanthropogenic C emissions (see Chapter 18).These are important arguments to feed into apolicy discussion (see Chapter 22).


Adoption of biochar for environmental management

Adopting biochar-based strategies for energyproduction, soil management and C seques-tration relies primarily on individualcompanies, municipalities and farmers (seeChapter 21). But national governments andinternational organizations could play a criti-cal role by facilitating the process oftechnological development, especially in theinitial phases of research and development.Although biochar has great potential tobecome a critical intervention in addressingkey future challenges, it is best seen as animportant ‘wedge’, contributing to an overallportfolio of strategies, as introduced byPacala and Socolow (2004) for climatechange. Such an approach does not applyonly to global warming, but also to large-scaleefforts to deliver food security to morepeople worldwide, to produce energy and toimprove waste management.

Adoption may occur in multiple sectorsto varying extents because biochar systemsserve to address different objectives (seeFigure 1.3) and operate on different scales,and can therefore be very different from eachother (see Chapter 9).

Concerns over using biomass resourcesthat would otherwise fulfil ecosystem servicesor human needs have to be taken into fullconsideration. Possible conflicts of producingenergy and biochar versus food as a conse-quence of massive adoption of biochartechnologies have to be considered, asdiscussed for bioenergy in general (Müller et

al, 2008). But the minimum residue coverrequired to protect soil surfaces also needs tobe established in conjunction with biocharmanagement of soil organic matter. Whilebiochar will undoubtedly improve soil qualityand productivity, some soil cover is requiredto keep water and wind erosion at a mini-mum. Therefore, plant residues cannot beentirely removed for biochar production.Other tasks that lie ahead are technologicalissues, such as refining methods for produc-tion, transportation of biochar and itsapplication to soil, while avoiding unaccept-able dust formation or health hazards (seeChapters 8 and 12).These are merely exam-ples of questions that need to be addressed inthe near future and that are discussed in moredetail in individual chapters.

Much information certainly must still begathered, and several such challenges have tobe addressed (Lehmann, 2007a; Laird,2008). But the tasks ahead are of such magni-tudes that they can be solved alongsideimplementation. In fact, biochar researchrequires working under conditions ofeconomically feasible enterprises in order toinvestigate the processes at the scale at whichthey are to be implemented. Much hasalready been achieved, and the basic informa-tion on which biochar for environmentalmanagement rests is available. This bookdocuments that information and serves as thestarting point for scaling up biochar manage-ment to become a global strategy.

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Biochar for Environmental Management: An Introduction · Simply put, biochar is the carbon-rich prod-uct obtained when biomass, such as wood, manure or leaves, is heated in a closed