Researchers analyse greenhouse gas balance of different biofuels produced in the U.S.
Researchers from Colorado State University and the U.S. Department of Agriculture, Agricultural Research Service have conducted the first of its kind, complete analysis of greenhouse gas emissions from different forms of biofuel production found in the U.S. The results revealed that a variety of bioenergy crops used for biofuels have the potential to reduce the amount of greenhouse gas emissions per unit of energy generated as compared to greenhouse gases emitted from fossil fuels. The researchers published their results in the April 2007 issue of Ecological Applications.
William Parton, researcher from Colorado State's Natural Resource Ecology Laboratory, or NREL, says "We have performed a unique analysis of the net biofuel greenhouse emissions from major biofuel cropping systems by combining ecosystem computer model data with estimates of the amount fossil fuels used to grow and produce crops for biofuels."
Study results revealed that when compared with the life cycle of gasoline and diesel, biofuels reduce the amount of greenhouse gases that enter the atmosphere:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: ethanol :: biodiesel :: cellulosic :: switchgrass :: hybrid poplar :: greenhouse gas emissions :: carbon balance ::
Bioenergy crops are able to offset carbon dioxide emissions by converting atmospheric carbon dioxide into organic carbon in biomass and soil, but the production of biofuels requires fossil fuels and impacts greenhouse gas fluxes. The primary sources of greenhouse gas emissions associated with crop production are soil nitrous oxide emissions and the CO2 emissions from farm machinery, farm inputs and agricultural processes. Colorado State and USDA scientists quantified all of these factors to determine the net effect of several bioenergy crops on greenhouse gas emissions.
Researchers found that, once the DAYCENT results were combined with estimates of the amounts of fossil fuels used to provide farm inputs and operate agricultural machinery and the amount of fossil fuel offsets from biomass yields, they were able to calculate the net greenhouse gas fluxes for each cropping system.
"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 Parton.
This study was a unique and complete analysis of bioenergy cropping for several reasons. Different crops vary with respect to length of plant life cycle, yields, biomass conversion efficiencies, required nutrients, net soil carbon balance, nitrogen losses and other characteristics which in turn impact management operations. Additionally, crops have different requirements for farm machinery inputs from planting, growing, soil tillage, applying fertilizer and pesticide and finally harvesting. The researchers were able to use life cycle analyses and the DAYCENT model to account for all of these factors as well as integrate climate, soil properties and land use to accurately evaluate the impact of bioenergy cropping systems on crop production, soil organic carbon and greenhouse gas fluxes.
Image: the carbon cycle, of which bioenergy cropping systems are a part.
More information:
The article in Ecological Applications is not yet online, but an abstract can be found here:
Adler, P.R., Del Grosso, S.J., Parton, W.J. 2007. "Cellulosic and Grain Bioenergy Crops Reduce Net Greenhouse Gas Emissions Associated with Transportation Fuels" [*abstract]. USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry. p.32
On the DAYCENT model, see: D.S. Ojima , S.J. Del Grosso, W.J. Parton, A.R. Mosier and C. Keough, Model Overview, Testing and Application to Agroecosystems [*.pdf], Global Carbon Project.
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William Parton, researcher from Colorado State's Natural Resource Ecology Laboratory, or NREL, says "We have performed a unique analysis of the net biofuel greenhouse emissions from major biofuel cropping systems by combining ecosystem computer model data with estimates of the amount fossil fuels used to grow and produce crops for biofuels."
Study results revealed that when compared with the life cycle of gasoline and diesel, biofuels reduce the amount of greenhouse gases that enter the atmosphere:
- grain based, 'first generation' ethanol and biodiesel from corn and soybean rotations reduced greenhouse gas emissions by nearly 40 percent
- cellulosic ethanol from reed canarygrass reduced greenhouse gas emissions by 85 percent
- cellulosic ethanol from switchgrass and hybrid poplar reduced greenhouse gas emissions by about 115 percent
"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." -- Stephen Del Grosso, USDA scientist and NREL researcher.Ethanol and biodiesel from corn and soybean are currently the main biofuel crops in the United States, but the perennial crops alfalfa, hybrid poplar, reed canarygrass and switchgrass have been proposed as future dedicated energy crops:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: ethanol :: biodiesel :: cellulosic :: switchgrass :: hybrid poplar :: greenhouse gas emissions :: carbon balance ::
Bioenergy crops are able to offset carbon dioxide emissions by converting atmospheric carbon dioxide into organic carbon in biomass and soil, but the production of biofuels requires fossil fuels and impacts greenhouse gas fluxes. The primary sources of greenhouse gas emissions associated with crop production are soil nitrous oxide emissions and the CO2 emissions from farm machinery, farm inputs and agricultural processes. Colorado State and USDA scientists quantified all of these factors to determine the net effect of several bioenergy crops on greenhouse gas emissions.
Researchers found that, once the DAYCENT results were combined with estimates of the amounts of fossil fuels used to provide farm inputs and operate agricultural machinery and the amount of fossil fuel offsets from biomass yields, they were able to calculate the net greenhouse gas fluxes for each cropping system.
"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 Parton.
This study was a unique and complete analysis of bioenergy cropping for several reasons. Different crops vary with respect to length of plant life cycle, yields, biomass conversion efficiencies, required nutrients, net soil carbon balance, nitrogen losses and other characteristics which in turn impact management operations. Additionally, crops have different requirements for farm machinery inputs from planting, growing, soil tillage, applying fertilizer and pesticide and finally harvesting. The researchers were able to use life cycle analyses and the DAYCENT model to account for all of these factors as well as integrate climate, soil properties and land use to accurately evaluate the impact of bioenergy cropping systems on crop production, soil organic carbon and greenhouse gas fluxes.
Image: the carbon cycle, of which bioenergy cropping systems are a part.
More information:
The article in Ecological Applications is not yet online, but an abstract can be found here:
Adler, P.R., Del Grosso, S.J., Parton, W.J. 2007. "Cellulosic and Grain Bioenergy Crops Reduce Net Greenhouse Gas Emissions Associated with Transportation Fuels" [*abstract]. USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry. p.32
On the DAYCENT model, see: D.S. Ojima , S.J. Del Grosso, W.J. Parton, A.R. Mosier and C. Keough, Model Overview, Testing and Application to Agroecosystems [*.pdf], Global Carbon Project.
Article continues
Tuesday, April 03, 2007
German dairy products group to make bioethanol from whey
The company is investing €20/US$27 million in the complex, which will be the first to make biofuel from whey. Stefan Müller, CEO of the group, says that by the end of 2007 production will come online and when maximum capacity is reached, the plant will make 10 million liters (2.64 million gallons) of ethanol per year.
Whey or milk plasma is the acidic liquid remaining after milk has been curdled and strained; it is a by-product of the manufacture of cheese or casein. Typically every 100 kg of milk will give about 10-20 kg of cheese depending on the variety, and about 80-90 kg of liquid whey. Its disposal is a major problem for the dairy industry, partly due to its composition. It has a low solids content and a very unfavorable lactose : protein ratio which makes it difficult to utilize as-is. The biological oxygen demand (BOD) is 32,000 to 60,000 ppm, which creates a very severe disposal problem.
Despite continuing efforts to find uses for the whey, either as-is or in dry form, or its major components (high quality protein and lactose), it is estimated that as much as 40-50% of the whey produced is disposed off as sewage, with the rest being used primarily for animal feed or human food. World production is estimated at 80 to 130 million tons per year:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: milk :: whey :: dairy :: cheese :: ethanol :: Germany ::
Given this waste problem, scientists been looking into ways to utilise the resource, and since the 1980s they have been hinting at the fact that there is an opportunity to use whey as an ethanol feedstock. Global interest in the biofuel and high oil prices now make commercial production viable.
Whey ethanol production is similar to that relying on starchy feedstocks. The lactose present in whey is yeast fermented and the resultant ethanol is distilled off and then purified to one of eight grades depending on its intended end use.
For the German dairy products group, whey is a biofuel feedstock that comes at a very low cost because it produces a vast quantity of it that poses a waste problem. "For this reason, we are very competitive and independent of the price developments on the biofuels market", says Müller.
There is a small body of research on the production of ethanol from whey.
More information:
Scott L. Terrell, Alain Bernard, and Richard B. Bailey, "Ethanol from Whey: Continuous Fermentation with a Catabolite Repression-Resistant Saccharomyces cerevisiae Mutant", Appl Environ Microbiol. 1984 September; 48(3): 577–580.
Ron Hamilton (AnchorProducts, Tirau): The Manufacture of Ethanol from Whey [*.pdf] - s.d. New Zealand Institute of Chemistry.
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