Biofuels, Land Conversion and Climate Change - a podcast by American Meteorological Society ESSS

Biofuels: Threats and Opportunities

It is possible to make biofuels that reduce carbon emissions, but only if we ensure that they do not lead to additional land clearing.
When land is cleared for agriculture, carbon that is locked up in the plants and soil is released through burning and decomposition. The carbon is released as carbon dioxide, which is an important greenhouse gas, and causes further global warming.

Converting rainforests, peatlands, savannas, or grasslands to produce food crop–based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel carbon debt” by releasing 17 to 420 times more carbon dioxide than the annual greenhouse gas reductions that these biofuels would provide by displacing fossil fuels.

Present Generation of Biofuels: Reducing or Enhancing Greenhouse Gas Emissions?

Previous studies have found that substituting biofuels for gasoline will reduce greenhouse gasses because growing the crops for biofuels sequesters takes carbon out of the air that burning only puts back, while gasoline takes carbon out of the ground and puts it into the air. These analyses have typically not taken into consideration carbon emissions that result from farmers worldwide converting forest or grassland to produce biofuels, or that result from farmers worldwide responding to higher prices and converting forest and grassland into new cropland to replace the grain (or cropland) diverted to biofuels. Our revised analysis suggests that greenhouse gas emissions from the land use changes described above, for most biofuels that use productive land, are likely to substantially increase over the next 30 years. Even advanced biofuels from biomass, if produced on good cropland, could have adverse greenhouse gas effects.

Biofuels and a Low-Carbon Economy

The low-carbon fuel standard is a concept and legal requirement in California and an expanding number of states that targets the amount of greenhouse gases produced per unit of energy delivered to the vehicle, or carbon intensity. In January 2007, California Gov. Arnold Schwarzenegger signed Executive Order S-1-07 (http://gov.ca.gov/executive-order/5172/), which called for a 10-percent reduction in the carbon intensity of his state’s transportation fuels by 2020. A research team in which Dr. Kammen participated developed a technical analysis (http://www.energy.ca.gov/low_carbon_fuel_standard/UC-1000-2007-002-PT1.PDF) of low-carbon fuels that could be used to meet that mandate. That analysis employs a life-cycle, ‘cradle to grave’ analysis of different fuel types, taking into consideration the ecological footprint of all activities included in the production, transport, storage, and use of the fuel.

Under a low-carbon fuel standard, fuel providers would track the “global warming intensity” (GWI) of their products and express it as a standardized unit of measure--the amount of carbon dioxide equivalent per amount of fuel delivered to the vehicle (gCO2e/MJ). This value measures vehicle emissions as well as other trade-offs, such as land-use changes that may result from biofuel production. For example, an analysis of ethanol shows that not all biofuels are created equal. While ethanol derived from corn but distilled in a coal-powered refinery is in fact worse on average than gasoline, some cellulosic-based biofuels -- largely those with little or no impact on agricultural or pristine lands have the potential for a dramatically lower GWI.

Biofuels and Greenhouse Gas Emissions: A Better Path Forward

The recent controversy over biofuels notwithstanding, the US has the potential to meet the legislated 21 billion gallon biofuel goal with biofuels that, on average, exceed the targeted reduction in greenhouse gas release, but only if feedstocks are produced properly and biofuel facilities meet their energy demands with biomass.

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