Biofuels Sustainability: A Nonfood Feedstock Primer
It is easy to recognize that if a farmer raises corn or soybeans for the production of biofuels that those bushels will not be used to satisfy demand in the human food chain. What might not be so readily apparent is that if those same acres of land were utilized to raise industrial oil crops (e.g., jatropha or crambe) or energy crops such as switchgrass, there is an indirect impact on the human food chain. These impacts can range from complete substitution of acreage from food production to energy production, such as with switchgrass, to fractional food loss when oilseeds are used to supply industrial oils for fuel as well as oilseed meal for livestock feed.
The following is a summary of some nonfood biofuel feedstocks and considerations regarding their impact on food production.
When people think about oilseeds, crops such as soybean and canola typically come to mind. However, numerous other oilseed crops do not compete directly with soybeans.
Typically, these nonfood oilseed crops have oil or meal characteristics that make them unpalatable or, in some cases, toxic. Crambe, camelina and jatropha are examples of oilseed crops that do not have a traditional food market. However, their oils can be used for biofuel production while supplying meal for livestock feed. In the case of jatropha, some varieties are known to have a toxic meal that animals will not eat. These crops have the potential to provide biofuel feedstocks while augmenting the food supply for animal feed.
Crop residue such as corn stalks and wheat straw are nonfood feedstocks that do not impact food production. They truly are coproducts of food production that can have utility for energy via combustion, gasification or enzymatic/fermentation to alcohol. Challenges with the widespread use of crop residue for fuel production are twofold: 1) the low-density nature of the material and 2) the impact on soil health. The time and cost associated with collecting and delivering crop residue will require careful evaluation. Studies conducted by the USDA and others focused on the relationship between crop residue and soil health have indicated that not all crop residue should be removed from the field.
Crops grown exclusively for energy production include switchgrass and fast-growing species of poplar, among others. These crops directly replace acres that could otherwise be used for growing crops (except if grown on Conservation Reserve Program land). Typically, however, energy crops require fewer inputs such as water or fertilizer and can be grown on land not suitable for many food crops.
Algae and aquaculture offer many advantages in the search for sustainable, renewable bioenergy feedstocks. Algae have the potential to provide orders of magnitude more oil per acre of land than traditional oil seed crops. Further, algae can be grown in arid climates with brackish water or sea water. Lastly, algae use as nutrients those things we typically view as pollutants, such as carbon dioxide from the air and nitrogen compounds in water. Unfortunately, the cost of growing algae today is too high to support fuel production alone.
Brad Stevens is a research manager at the EERC. Reach him at firstname.lastname@example.org or (701) 777-5293.