|October 02, 2007|
Agro-biofuel -- is no laughing matter!
|Vancouver, Canada - "When the extra N2O emission from biofuel production is calculated in "CO2-equivalent" global warming terms, and compared with the quasi-cooling effect of "saving" emissions of fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings." |
That rather dry statement is an extract from the conclusions of a study by Nobel prize winning chemist Paul J. Crutzen published in the Atmospheric Chemistry and Physics, An Interactive Open Access Journal of the European Geosciences Union, dedicated to the publication and public discussion of high quality studies investigating the Earth's atmosphere and the underlying chemical and physical processes.
The study by Crutzen and his colleagues re-examined the "relationship", on a global basis, between the amount of nitrogen fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and total emissions of nitrous oxide (N2O) using known global atmospheric removal rates.
In simpler terms it means the authors studied the amount of nitrous oxide (otherwise known as the laughing gas, an aesthetic once used by dentists) that is produced by the use of fertilisers used to grow crops for biofuels. Nitrous oxide is 300 times more insulating than the most common man-made greenhouse gas - carbon dioxide. The study suggests the fertiliser use on farms is responsible for three to five times more such greenhouse gas emissions than previously thought.
Using biodiesel derived from rapeseed would produce between 1 and 1.7 times more greenhouse gas than using conventional diesel, the study estimated.
Biofuels derived from sugar cane, as in Brazil, fared better, producing between 0.5 and 0.9 times as much greenhouse gases as gasoline, it found.
Maize (corn) is the main biofuels feedstock used in the United States, and it produces between 0.9 and 1.5 times the global warming effect of conventional gasoline, it said.
In a news report by Reuters, report co-author Professor Keith Smith is quoted as saying "As it's used at the moment, bioethanol from maize seems to be a pretty futile exercise." "Even if somebody decides that our numbers are too big ... if you add together the undoubted amount of nitrous oxide that is formed, plus the fossil fuel usage, with most of the biofuels of today you are not going to get any benefit," Smith is quoted as saying by Reuters.
The study concludes that crops with less of a nitrogen demand, such as grasses and woody coppice species have more favourable climate impacts.
The implications of the study are enormous and of particular concern for alternative fuels derived from rapeseed as is commonly used in Europe, which the study concludes could produce up to 70 percent more planet-warming greenhouse gases than conventional diesel. It would also call into question the use of corn to produce biofuels which has become a huge industry in the United States and is growing in importance in Canada also.
Last week's main feature article in GLOBE-Net as questioned the efficacy of growing crops to produce biofuels, noting that the use of food crops, even surplus crops, for energy supply is likely to be unsustainable because of the impact on food prices.
See also this week's GLOBE-Net Business Reports detailing the conclusions of a World Bank Report on biofuels that notes the generation of biofuels derived from food crops is intensive in land, water, energy and chemical inputs and that while the environmental literature is dominated by discussions of net carbon offsets and net energy gains, indicators relating to impact on human health, soil quality, biodiversity, water depletion, etc., receive much less attention.
Consistent with the conclusions of the study by Crutzen and his colleagues, the GLOBE-Net article notes non-food crops like switchgrass and fast growing "weed trees" such as poplar are far more appropriate as biomass feedstock because they can grow in marginal areas, do not affect food supply, and do not require intensive farming methods.
The report concludes that as the release of N2O affects climate and stratospheric ozone chemistry by the production of biofuels is so potentially damaging, much more research on the sources of N2O and the nitrogen cycle is urgently needed. The implication is that low demand biomass and less intensive farming methods could lead to biofuels that have a net positive benefit.
The actual study is not an easy read, but is available here
The Reuters news report, which is much easier to read, is available here.
For More Information: Reuters