Biomass and Biomergy Vol. 2, No.s l-6, pp. 3944.1992 0961-9534M $5.00 + 0.00 Printed in Great Britain. All rights resend 0 1992Pcrg-Rwaud

DEDICATED AGRICULTURAL, AND HERBACEOUS CROPS

J. L. BUTLER

2823 Rainwater Road, Tifton. GA 31794-2530. U.S.A.

ABSTRACT

Agricultural and herbaceous crops can be used to produce renewable energy in a short time following establishment. Some perennial crops also offer protection against soil erosion, allowing them to be grown on land which would be unsuited to row-crop agriculture. When compared with woody biomass crops, harvesting the crop and putting it into a transportable form may be more expensive and the energy density is low, allowing shatter distances to the site of conversion to a more useful form of energy. Those crops which can be more easily converted to a liquid fuel appeared to be receiving the most attention. The current cost of producing renewable energy from these crops is greater than the cost of conventional fossil energy.

KEYWORDS

Herbaceous crops; annual crops; perennial crops; biomass energy; renewable energy; liquid fuels.

INTRODUCTION

Biomass crops used as energy feedstocks have several environmental advantages over conventional fossil fuel sources. Biomass crops recycle carbon dioxide on a short-term basis and do not result in a buildup of this gas. They are readily biodegradable and generally do not have much sulphur to be emitted as sulphur dioxide to contribute to acid rain. They also have some very real disadvantages. Biomass crops have a very low energy density compared with fossil fuels, most require conversion which may range from very simple to very complicated. Their biodegradability requhes that they be stored in such a manner as to keep them from degrading until processed. The agricultural/herbaceous crops share the advantages and disadvantages with the woody biomass crops. However, the energy density is even lower for most herbaceous crops than for the woody crops. This is compensated for, however, by the fact that some herbaceous crops may be more easily converted to liquid fuels than the woody crops. The herbaceous crops have a relatively short time between planting and the first harvest. Many of the perennial crops offer excellent erosion control, allowing the producer to realize a crop on land which is marginal or even unacceptable to conventional row-crop agriculture. For purposes of this report, the herbaceous crops will be divided into two groups: crops for biomass , i.e., those which can best be used as a solid fuel or for which the conversion to a liquid fuel is either very complicated or being developed; and liquid fuel crops, i.e., those which can be converted to liquid fuel relatively easily with existing technology.

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40 J. L. BUTLER

CROPS FOR BIOMASS

The crops listed in this category generally cannot be converted to liquid fuels very easily or the technology for the conversion is still being developed. Because of the low energy density of these crops, the conversion to a more useful form of energy must take place very near the point of production or the crop must be processed (by baling, for example) to increase the energy density in order to reduce the transportation costs to move the crop to a centralized processing point. Even with this compaction, the energy density is still well below that of woody biomass. Consequently, the conversion factory would either have a shorter radius for delivery of herbaceous biomass, or the cost per unit would have to be enough lower to compensate for the increased transportation costs. A further disadvantage of the herbaceous biomass crops is that they require significantly more fertilizer, especially on marginal lands, than do the woody crops. Leguminous crops do require significantly less nitrogen fertilizer than do the non-legumes. This advantage may be offset, however, by a generally reduced yield from the legumes. As with other crops, the yields from biomass crops will vary with species, region and year. Studies in New York (Pfeifer et al., 1990) show that timothy-redtop-red clover (Phleam prutense, Agrostis gigantea L., Trifolium pratense) and alfalfa-bromegrass (Medicago sativa, Bromus inermis) mixtures yield approximately the same (10 Mg/ha) on well drained soil. These mixtures have the advantage that they do not require nitrogen fertilizer. On poorly drained soil, Reed canarygrass (Phalaris arundinacea L.) had the best yield of about 7 Mg/ha. No pest control was necessary to achieve these yields and the high hemicellulose and cellulose content (52% total) makes it a promising species for conversion to energy.

Studies conducted in Indiana (Chemey et a1.,1990) show that switchgrass (Pan&urn virgatum L.) produced up to 16Mg/ha with one cutting. Alfalfa produced up to 17 Mg/ha, but this required three cuttings and additional pest control which tended to offset the reduction in nitrogen fertilizer required. Economic analyses conducted in the same state (Dobbins et al., 1990) showed that switchgrass had the lowest production cost for any of the perennial crops on marginal land ($24.38/Mg). The next lowest cost was for an annual, sweet sorghum (Sorghum bicolor) at $28.2O/Mg. This was followed by althlfa at $3 1.6OlMg and Reed canarygrass at S34.57lMg. Based on estimates of the rate of conversion and an ethanol price of $0.34/litre, the gross margin per Mg produced was estimated. For marginal land, the average gross margin was $16.06 for sweet sorghum, $19.21 for alfalfa, $49.84 for Reed canary grass and $62.62 for switchgrass. Based on these returns, switchgrass and Reed canarygrass appear to be the most promising.

In tests conducted in Alabama, (Bmnsby et a1.,1991) reported switchgrass yields of up to 17.5 Mg/ha. Bransby further reported that elephantgrasses (Pennisetum purpureum) and energycane (Saccharum spp.) had yields in the range of 24-32 Mg/ha. (Prine et al., 1991) reported yields of elephantgrass of 21.5-47.7 Mg/ha at various locations in Florida and Alabama but cautioned that winterkill was a likely possibility in the more northern locations of these tests. The yields of energycane was also good, exceeding the yield of elephantgrass in two locations in one of the three years of the test.

Based on studies conducted with eight herbaceous species in Virginia, (Parrish et al., 1990) concluded that two warm season grasses switchgrass and lovegrass (Eragrostis cirvia cv ‘Common’), appeared to be the most promising. At nine different sites and across three soil types, the switchgrass yields were in the range of 10.5-I 1.8 Mg/ha and the lovegrass yields were in the range of 8.4-12.6 Mg/ha. Both species were readily established using no-till methods and have persisted for five years. The switchgrass has remained essentially weed-free with no cultural weed control. Due to persistence of ground cover/crop residue in the non-growing season, the soil is well protected against erosion. Yields of switchgrass and lovegrass were less sensitive to drought than the other crops, and the yields were obtained with relatively low levels of inputs. The researchers believe that herbaceous energy crops may represent a viable cropping alternative for owners of many thousands of hectares of agricultumlly marginal land in the Piedmont region which stretches from Pennsylvania to Alabama.

English et al., (1991) developed a farm-firm modelling system for evaluating herbaceous energy crops. Since determining the potential effects of growing biomass as a crop instead of a more traditional crop requires careful analysis at both the farm and federal level, the model was developed to address both the

Agriculhml and herbaceous crops 41

economic and environmental issues. The example used in the study focused on the e&ct of biomass production on highly erodible cropland in terms of profitability, erosion control and farm program costs. The modelling system was applied to model the production of switchgrass on three lbrms in the Southeast. The model showed equivalent reductions in erosion rates flom entering highly erodible land in the Conservation Reserve Program (CRP) and the production of switchgmss as a biomass energy crop. Both switchgrass and the CRP plans resulted in lower net returns than the base plan. The biomass farm plans were, in general, more profitable than the CRP plans. The model shows that less government involvement would be required to maintain the acceptable erosion rate if the producers were permitted to produce a perennial biomass crop for sale on land which is now enrolled in the CRP.

In Italy, A. Biotec Research Center at Cervia (RA) is conducting studies on sweet sorghum, fiber sorghum, kenaf (Hibiscus cannabinus), cardoon (Cynara cardunculus), coffee-chicocy (C’rium intybus) and miscanthus (Mscanthus sinensis). They are also conducting breeding research on both sweet sorghum and fiber sorghum. In 1990, they reared 526 inbred lines and had 106 crosses. The general criteria of selection are: high potential yield, limited height, large diameter stalk, disease resistance, lodging resistance, high refiactometric degree, high early vigour, high monostelicness percentage in the case of selection of monoculm lines.

The general opinion of most of the researchers is that by a concerted breeding program the yields of the biomass crops can be significantly increased.

LIQUID FUEL CROPS

Although most of the me1 ethanol in the United States is produced from corn, we will limit the discussion here is limited to the high sugar crops as the feedstock for ethanol production and oil crops, specifically mpeseed (Brassica naps L.) as the feedstock for the diesel fuel substitutes.

One method for reducing air pollution in the United States Environmental Protection Agency (EPA) non-attainment areas is mandating the use of oxygenated fuel for vehicles operating in those areas. For gasoline, this can be achieved by blending ethanol with the gasoline. Currently about 10% of the U.S. gasoline supply is an ethanol blend. Corn grain currently is the feedstock for more than 90% of the fuel ethanol produced in the U.S. There is considerable interest in producing ethanol from crops other than corn, and the sugar crops, such as sugar cane and sweet sorghum, are prime candidates because they produce large quantities of fermentable carbohydrate per hectare. Unlike corn, which concentrates its carbohydrates in the grain, these species store the structural carbohydrate in the stalk and the nonstructural carbohydrates as soluble sugar in both the sugar in the stalk and the starch in the seed. The starch (after cooking to convert it to sugar) and the sugar can be fermented by conventional yeast fermentation. Much research is underway to convert the structural carbohydrates into sugars which can be fermented. If this can be achieved, the potential ethanol yield from sweet sorghum can be tripled.

The production, harvesting and handling of corn is highly mechanized, whereas the production of sweet sorghum has been primarily for the syrup by small farmers with only small areas of the crop being grown per farm. Little effort has gone into the mechanization and handling of sweet sorghum. There are two other disadvantages which must be overcome if sweet sorghum is to become competitive as a feedstock for ethanol production: it is harvested at high moisture content, and cannot be stored in conventional storage for long periods of time as can corn; the energy density is low resulting in about 15% as much ethanol to be produced per unit of weight of sweet sorghum compared to corn.

Presently, juice is expressed from the sweet sorghum plant by either passing the stalk between rollers or through a screw press. Cundiff (1990) reported that a conventional forage harvester with a two row header harvested erect sweet sorghum without difficulty. The chopped whole stalk was passed through a screw press which achieved a juice expression of 35% of the whole stalk mass. Sugar collected in the juice was 44% of the whole stalk sugar as determined by a nonstructural carbohydrate analysis. When juice is expressed from whole stalks, the fibrous parts of the plant absorb juice and reduce yield. Elimination of the rind and leaf would thus increase the juice yield. Cundiff (1992) reported that a

42 J. L. Bunm

device to separate the rind and leaf from the pith and the subsequent passing of the pith through a screw press resulted in a juice expression ratio of 60% compared with 35% for the whole stalk

Worley et al. (1991) analyzed three different systems for harvesting sweet sorghum for ethanol. System A used a light-weight whole stalk harvester to cut stalks and place them in windrows in the field. The stalks were subsequently transported to a storage pile. The stalks were then processed (within the next 30 days) through trailer mounted equipment which separated the pith and rind-leaf fractions, expressed juice from the pith with a screw press, and conveyed the pith presscake and rind-leaf into a bunker silo for storage. System B used a machine to separate the pith and rind-leaf fractions as it moved through the field. The rind-leaf portion was dropped back onto the field and the pith collected in a towed wagon for subsequent juice extraction. System C used the whole stalk harvester as in system A but the processor moved along the windrows picking up the bundles of stalks and processing them in the field. Economic analysis showed that the feedstock cost per litre of ethanol was $0.56, 0.63, and 0.87 for systems A, B, and C, respectively. An energy analysis was done on two options for converting the harvested material into ethanol: 1) concentrate the juice into syrup for storage and use as a fermentation feedstock year-round, 2) ferment the juice directly during the harvest season and use the e&led by- products as additional feedstocks for the plant,which would operate on a cellulose conversion mode for the remainder of the year. These options were compared with current technology for producing fuel ethanol from corn. Energy ratios (output/input) were 0.9, 1.1, and 0.8 for Option 1, Option 2, and corn respectively. Liquid fuel ratios (liquid fuel output/liquid fuel input) were 3.5,7.9 and 4.5 respectively.

In the U.S.A. ethanol production from corn is heavily subsidized, and, from the research thus far on the use of sweet sorghum for ethanol, it appears that either significant breakthroughs in technology must occur or the price of fossil fuel, either due to cost or taxes, must be significantly increased in order for this crop to become competitive in ethanol production.

In Europe, the methyl ester of rapeseed oil (biodiesel) is becoming an accepted diesel fuel substitute. The warranty of all diesel engines sold in Europe accepts biodiesel as a fuel. Biodiesel performance is almost identical to diesel and has a better emission profile than diesel fuel. Further, it is biodegradable and spills pose no long-term environmental hazards.

In November of 1991, a University of Missouri team including the author visited Europe to gather state- of-the-art information on the production and utilization of mpeseed oil. Visits made to representatives of the EEC in Brussels, Belgium indicated that biodiesel is rapidly becoming accepted. Other uses of rapeseed oil were lubricants, hydraulic oils and chainsaw oils.

Austria is perhaps the leader in the utilization of biodiesel, and visits were made to the Federal Institute of Agricultural Engineering in Wieselburg, Austria. This institute has produced over 500,000 litres of biodiesel and have over 100,000 hours of testing on diesel engines. The biodiesel produced here fulfills the following minimum requirements: flash point of not less than 55 ‘C; Conmdson-coking residue less than 0.1%; ash content of less than 0.1%; water content less than 500mg/kg. The flash point must be above 55 ‘C because of the requirements of the filling stations (safety). Their experience shows that biodiesel is suitable for use without additives down to 0 degrees,but that minor starting problems may exist below 5 OC.

The Austrian Parliament has exempted farm use of biodiesel from the heavy highway tax, making it competitive with diesel fUe1. To meet this demand, and in preparation for the anticipated demand when the EEC clean air act takes place in 1993, a BIODIESEL processing plant has been placed in operation in Aschach, Austria. This plant, directed by Dr. Peter W&man, is designed to produce vegetable grade oil prior to transestrification. The plant is operated by 25 employees and is operated 7 days per week, 24 hours per day. It currently processes about 30,000 Mg of rapeseed per year. This yields about 10 million liters of biodiesel, 20,OOOMg of mpeseed meal and 1OOOMg of glycerol per year. Since they use only the double zero mpeseed, commonly referred to as Canola, the meal is used for animal feed. Once fbll experience is gained it may be possible to produce the same amount with about one-half the labor force.

Agricultural and herbaceous crops 43

A much smaller cooperative, operated by Dr. Franz Parrer, in Neulengbach was also visited. This co-op comprises 290 farmers who currently have a total of about 500 ha of oilseed. This is about equally divided between sunflower and Canola type rapesced These 500 ha produce about 1SOOMg of seed , yielding about 500,000 litres of biodiesel (Okodiesel) and 1OOOMg of mpeseed meal. The farmer delivers the seed and gets back the tmnsesterized oil, glycerol and meal. The typical farmer gets back approximately 40% of his biodiesel needs, and about 20% of his meal needs. After two years of operating, the farmers voted last fall to double their production. This will take place in 1992.

Currently the seed is processed through six expellers (2 screws each). The extruded meal is conveyed into storage and the oil goes through a filter to remove the solids. The oil then goes, without additional processing, to the transestrification tank. Through an automatic meterhtg device, potassium hydroxide and methanol are mixed. This mixture is metered into the tank containing the oil and the three components are mixed and then proceed to a settling tank. After the process is partially completed, the glycerol is removed and the partially transesterized oil is again mixed with the potassium hydroxide mixture and the transestriflcation is completed. Following this, the remaining glycerol is removed and the ester is washed and goes into storage. The water and remaining methanol goes into a tank where the methanol is removed by bubbling compressed air through the mixture. This process which is totally automated requires only 3-4 man hours per day. The process operates 24 hours per day and processes about 10 Mg seed per day. The productive capacity is thus between 20 and 30 Mg per man day. According to Dr. Parrer, 40% of the value of the meal pays for the entire operating cost.

The members like the operation because they do not have to absorb the margins normally involved in selling a crop and buying supplies.

Charles Peterson of Idaho, who has been involved in research on biodiesel from vegetable oil for several years also participated in the visit and was impressed with the loweost and the apparent success of this co-op. He was especially impressed with the automated system and the biodiesel yields obtained.

Dr. Paul Ramer, of the University of Georgia at Griffin, is currently conducting national variety trials on rapeseed. Although some varieties at some locations have yields comparable to those in Europe, the yields are generally lower. This indicates the need for both breeding and research on production and harvesting systems.

The law which allows farmers to grow minor oilseeds (which includes rapeseed) on land which has been “set aside” and still collect the payment for not producing a program crop, should allow the development of a biodiesel industry in the United States. The infrastructure must, of course, be developed.

CONCLUSIONS

Considerable experience has been gained in the production of biomass crops for energy. With the current price of petroleum products, none of the crops is economically viable in the United States. In Austria, the high degree of development of processing and the tax structure have apparently combined to make the production of biodiesel profitable. It appears that environmental concerns may become sufficient to make the widespread use of renewable energy from biomass crops possible.

REFERENCES

Bransby, D.I., S.E. Sladden and D.D. Kee (1991). Yield and cost of biomass from eight switchgrass varieties in Alabama. In: Proceedings, Sourhem Biomass Conference, Louisiana State University, Baton Rouge, LA. p. 1I.B. 1.

Chemey, J.H., K.D. Johnson, J.J. Volenec, E.J. Kladivko and D.K. Greene (1990). Evaluation of potential herbaceous biomass crops on marginal crop lands: 1)agronomic potential. In: Report ORNL/Sub/85-27412/.5&PI. Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6285.

44 J. L. BUTLER

Cundiff, J.S. (1990). Potential of sugar cane/sweet sorghum as a feedstockfor energy systems. Unpublished report. VP1 & SU, Blacksburg, VA 24061-0303.

Cundiff, J.S. (1992). Harvesting and storing sweet sorghum for ethanol production. Unpublished book chapter prepared for Elsevier Energy in Agriculture vol VII.

Dobbins, C.L., P. Preckel, A. Mdatii, J. Lowenberg-DeBoer and D. Stuckey (1990). Evaluation of potential herbaceous biomass crops on marginal crop lands: 2) Economic Potential. In: Report ORAWSub/85-27412/J&, Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6285.

English, B.C., R.R. Alexander, K.H. Loewen, S.A. Coady,G.V. Cole, and W.R. Goodman (1991). Development of a farm-firm modelling system for evaluation of herbaceous crops. Report ORNL/Sub/88SC6 16/2. Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6285.

Parrish, D.J., D.D. Wolf, W.L. Daniels, D.H. Vaughn and J.S. Cundiff (1990). Perennial species for optimum production of herbaceous biomass in the Piedmont. Report ORNLlSubf85i274 1315. Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6285.

Pfeifer, R.A., G.W. Flick, D.J. Lathwell and C. Maybee (1990). Screening andselection of herbaceous species for biomass production in the midwest/lake states. Report ORNL/Sub/85-2741015. Oak Ridge National Laboratory, Oak Ridge, TN 3783 l-6285.

Prine, G.M., P. Mislevy, R.L. Stanley, L.S. Dunivan and D.I. Bransby (1991). Biomass production of tallgrasses in the southeast USA. In: Proceedings, Southern Biomass Conference, Louisiana State University, Baton Rouge, LA. p, II.B.2.

Worley, J.W., D.H. Vaughn, and J.S. Cundiff (1991). Energy analysis of three sweet sorghum harvest systems for ethanol production. In: Proceedings, Southern Biomass Conference Louisiana State University, Baton Rouge, LA. p. V.B.2.