Fuels from Energy Crops

The term energy crop can be used both for biomass crops that simply provide high output of biomass per hectare for low inputs, and for those that provide specific products that can be converted into other biofuels such as sugar or starch for bioethanol by fermentation, or into vegetable oil for biodiesel by transesterificatiou 

Energy crops such as short-rotation woody crops, herbaceous woody crops, grasses, starch crops, sugar crops, forage crops, oilseed crops, switchgrass, and miscanthus can be converted to liquid biofuels by thermochemical and biochemical conversion processes. 

Miscanthus is a tall perennial grass that has been evaluated in Europe during the past 5 to 10 years as a new bioenergy crop. Like other energy crops, the harvested stems of miscanthus may be used as fuel for production of heat and electric power, or for conversion to other useful products such as ethanol. 

Biomass includes 60% wood and 40% non-wood materials. The conversion of wood into biofuels andbiochemicals is technically feasible. Wood valorization processes include fractionation, liquefaction, pyrolysis, hydrolysis, fermentation and gasification. 

Beteta, T. 1995. Experiences with plastic tube biodigesters in Colombia. Universidad Nacional Agraria, Managua, Nicaragua. 

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Table 5.11 Average energy yields of different fuel types produced from energy crops... 

Woody biomass is low in ash content, sulphur, chlorine and silica, and the ash itself is dominated by compounds of Ca and K. Biomass fuels from crops are higher in ash content, sulphur, chlorine and silica. The ash is dominated by oxides of Ca, K and Si. The fuels based on the growing parts of trees (bark+debries) show ash compositions between the two extremes, wood and acre crops. Therefore the largest chlorine emissions are expected from energy crops (grasses) and from agricultural by products (straw etc). 

Lipinsky, E. S., et al., Second Quarterly Report on Fuels from Sugar Crops report prepared by Battelle Memorial Institute, Columbus, Ohio for the U.S. Department of Energy, October 1977. 

In spite of significant problems, many are optimistic about the role of biomass for alternative fuels in the future. The U.S. Department of Energy believes that biofuels from nonfood crops and MSW could potentially cut U.S. oil imports by 15 to 20%. Ethanol industry members believe that the capacity for producing that fuel alone could be doubled in a few years and tripled in five years. 

Although most ethanol is now produced from corn, research has been done on producing this type of alcohol fuel from cellulosic biomass products including energy crops, forest and agricultural residues, and MSW, which would provide much cheaper feedstocks. The process of chemically converting these cellulosic biomass feedstocks is more involved and until this process can be simplified the price of ethanol will remain high. 

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