Fueling the Biofuel Conversation

A recent study by the United State Department of Agriculture and Colorado State University, entitled “Net Greenhouse Gas Flux of Bioenergy Cropping Systems Using DAYCENT,” has conducted the first complete analysis of greenhouse gas emissions from biofuel production. After testing seven different crops used in the manufacturing of biofuels using the DAYCENT biogeochemistry model, the results show a significant variation in the amount of greenhouse gas emissions per unit of energy generated in comparison to greenhouse gases emitted from fossil fuels.

The report reveals that comparing the life cycle of gasoline and diesel to ethanol derived from corn and soybean, greenhouse gas emissions are reduced by around 40 percent. These crops are at the low end of the spectrum in comparison to crops of switchgrass and hybrid poplar with a reduction of 115 percent.

Recent controversy has arisen over the actual fuel efficiency of biofuels in comparison to fossil fuels due to the process needed to refine bioenergy crops into liquid fuel, the environmental degradation evolved with growing and transporting crops, and the possible increase in other emissions such as NOx. Some researchers have concluded that taking these facts into consideration, ethanol actually produces a net energy loss rather than a gain.

USDA and NREL researcher, Stephen Del Grosso states, "although fossil fuel inputs are required to produce and process biofuels, hybrid poplar and switchgrass converted to ethanol compensate for these emissions and actually remove greenhouse gasses from the atmosphere when the benefits of co-products are included. Greenhouse gas savings from biomass gasification for electricity generation are even greater. This research provides the basis for evaluating net biofuel greenhouse gas emissions and highlights the need to improve the technologies used for large scale conversion of biomass to energy and to more fully exploit agricultural co-products.”

"We used extensive observed greenhouse gas flux and crop yield data to verify DAYCENT model predictions of crop yields and net greenhouse gas fluxes from all of the biofuel crop rotations. DAYCENT model results were combined with life cycle analyses of crop production, conversion to biofuel, and fossil fuel displaced to estimate net greenhouse gas emissions," said William Parton, a NREL researcher.

The study was unique in that it offered a complete analysis of different crops, varying in respect to length of plant life cycle, yields, biomass conversion efficiencies, required nutrients, net soil carbon balance, nitrogen losses and other specifics which impact crop management. The net greenhouse gas flux for each crop was calculated by combining the DAYCENT results with estimates of fossil fuels used by agricultural machinery in growing of the crops and the amount of fossil fuels offset from biomass yields.

See the Source:
Colorado State University
USDA – Fact Sheet
Is Ethanol Fuel Really Better for the Environment than Sticking with Gas?