When compared to fossil fuels, manufactured liquid biofuels do not necessarily produce fewer greenhouse gas emissions.
The two key factors that determine whether biofuels lead to lower or higher greenhouse gas emissions than fossil fuels are:
- How the biomass (the basis of the biofuel) is produced and harvested. This process could emit carbon through, for example, fertilizers and machinery.
- Where the biomass is produced. Biofuel production that leads directly or indirectly to land use change emits high levels of carbon.
- The ethanol produced from a hectare of maize reduces greenhouse gas emissions by 1.8 tonnes of carbon dioxide equivalent (tCO2e) per hectare per year compared to the oil equivalent. But each hectare of forest, grasslands or savannahs converted to cropland emits greenhouse gases when the carbon-storing biomass that makes up these biomes is cut down. For forests, these “up-front” emissions are 604 to 1,146 tCO2e per hectare depending on forest type and maturity; for grasslands or savannahs, these emissions are 75 to 305 tCO2e (Searchinger et al. 2008).
- Some liquid biofuel policy alternatives could significantly increase global fertilizer use to satisfy additional production needs. Additional greenhouse gas emissions due to increased fertilizer use (primarily nitrous oxide, N2O) could be greater than those arising from land use change (Mosnier et al. 2012: i).
- Using good cropland to expand [liquid] biofuel production will likely exacerbate global warming the same way as directly converting forest and grasslands (Searchinger et al. 2008: 1240). For example, increasing ethanol production by 56 billion litres, which uses the equivalent of 12.8 million hectares of maize in the United States, would require bringing an additional 10.8 million hectares of land into cultivation to meet demand for maize for other uses. (Searchinger et al. 2008: 1239).
- The Organisation for Economic Co-operation and Development (OECD) and the United Nations Food and Agriculture Organization (FAO) (2012) project that from 2012 to 2021, global ethanol and biodiesel production will expand from 113 billion to 180 billion litres annually. The largest markets—the United States, Brazil and the European Union—will grow at a slower pace than in recent years (USDA 2011).
- From 2012 to 2021, ethanol prices are expected to increase from USD 0.85 to 0.95 per litre, while biodiesel prices are expected to increase from USD 1.53 to 1.81 per litre.
- Continued expansion is largely due to biofuel policies, primary among them use mandates and tax incentives, (USDA 2011) and high crude oil prices.
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- [EEA] European Environment Agency Scientific Committee. 2011. Opinion of the EEA scientific committee on greenhouse gas accounting in relation to bioenergy. Brussels: European Environment Agency Scientific Committee. (Available from http://www.eea.europa.eu/about-us/governance/scientific-committee/sc-opinions/opinions-on-scientific-issues/sc-opinion-on-greenhouse-gas/view)
- Havlík P, Schneider UA, Schmid E, Böttcher H, Fritz S et al. 2011. Global land-use implications of first and second generation biofuel targets. Energy Policy 39: 5690–5702.
- Mosnier A, Havlík P, Valin H, Baker JS, Murray BC et al. 2012. The net global effects of alternative U.S. biofuel mandates: fossil fuel displacement, indirect land use change, and the role of agricultural productivity growth. Nicholas Institute Report January 2012. Durham, North Carolina: Nicholas Institute for Environmental Policy Solutions at Duke University.
- [OECD/FAO]. The Organisation for Economic Co-operation and Development and United Nations Food and Agriculture Organization. 2012. OECD-FAO Agricultural Outlook 2012-2021. Paris: OECD; Rome: FAO. (Available from http://dx.doi.org/ 10.1787/agr_outlook-2012-en)
- Searchinger T, Heimlich R, Houghton RA, Dong F, Elobeid, A et al. 2008. Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change. Science 319:1238-1240.
- Searchinger T. 2008. The impacts of biofuels on greenhouse gases: how land use change alters the equation. Economic Policy Program Policy Brief. Washington, D.C.: The German Marshall Fund of the United States.
- [USDA] U.S. Department of Agriculture. 2011. USDA Agricultural Projections to 2020. Washington, D.C.: United States Department of Agriculture (USDA). (Available from http://www.usda.gov/oce/ commodity/archive_projections/USDAAgriculturalProjections 2020.pdf