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 Recent publications about the impact of land conversion on global warming pollution from crop-based biofuels are changing the science of measuring biofuel risks and rewards. The studies demonstrate that when crop-based biofuels contribute to deforestation or other damaging land conversions, their benefits can be compromised or even lead to a net increase in pollution. The science behind these calculations is new, and the numbers can be expected to change as the science matures, but we can already conclude that biofuels must use both land and energy efficiently to ensure they play a constructive role in an overall strategy to address global warming.
Some biofuels can be made without harmful changes in land use, and these have great potential to reduce global warming pollution. Examples include fuels made from biomass waste products or from native perennials on land not currently used for or well suited to food crops. On the other hand, there are types of land that should certainly not be used for biofuel production, especially forests high in stored carbon and rich in biodiversity. Converting a forest to cropland can result in global warming pollution that is much larger than the annual benefits from biofuels that could be grown on that land. A recent paper in Science by Fargione et al. estimates that if peatlands in Southeast Asia are converted to palm oil plantations to make biodiesel, it will take 423 years to pay back the “carbon debt” from the land use change.
In the United States today, biofuels are mainly produced from corn and soy. Corn and soybeans are produced domestically on existing agricultural land, so there is not necessarily a direct land use change. But even for these home grown fuels there can be an indirect land use effect. When corn and soy are used to make biofuels, the resources they supply are, at least in part, taken out of the market for food and animal feed1. This increases corn and soy prices, which stimulates land conversion elsewhere around the world. Another paper in Science, by Searchinger et al., studied this indirect effect using agricultural economics models to estimate how global markets respond to increased use of corn for biofuels . They used economic models and historical data on land conversion to estimate where new crops will be planted, where the land will come from, and what emissions will be associated with the land conversions. Based on these assumptions, they calculate that when the indirect land use effects are included, corn ethanol produces greenhouse gas emissions almost double gasoline.
The federal Energy Bill passed in 2007 includes a Renewable Fuel Standard (RFS) that significantly ramps up use of biofuels like ethanol, from about 6 billion gallons currently used to 36 billion gallons in 2022. The RFS has requirements that most renewable fuels reduce global warming pollution, including pollution from indirect land conversion. However, the RFS exempts corn ethanol plants that began construction prior to the law’s enactment from global warming pollution limits. This loophole undermines the protections in the RFS. If the indirect land use impacts are as big as Searchinger et al. estimate, the extra emissions from land use change from roughly 12 billion gallons of exempt corn ethanol can wipe out the benefits from the remaining 24 billion gallons of renewable fuel over the lifetime of the RFS2.
The UCS “Principles for Bioenergy Development” provide an overall picture of how biofuels and bioenergy can be a productive part of the overall strategy to address climate change. The following recommendations address land use issues specifically and suggest how to avoid harmful unintended consequences that can stop biofuels from achieving their potential.
Performance based policies that reward reductions in global warming pollution over the full fuel lifecycle, based on the best available information and vetted in an open and transparent process. The rulemaking currently underway for the Federal RFS and the California low carbon fuel standard will determine how global warming pollution is measured for compliance with these standards. It is critical to the success of these standards that they include all significant inputs and impacts, including indirect land use changes. The science of global warming pollution and indirect effects is developing, and new studies will improve our understanding over time. There must be a mechanism to ensure that lifecycle emissions metrics used for compliance also improve, and that this process is open, transparent, and based on the best peer reviewed science.
Biofuels lifecycle analysis should include a non-zero estimate of emissions associated with indirect land use changes based on the best available science. While there is no consensus about the exact magnitude of indirect land use effects, and details of the methodology are being debated, there is broad agreement that indirect land use is real, and is significant. The Federal RFS and the California LCFS are in rulemaking right now, and will be implemented before a firm consensus on these details can be reached. We think it is very important to have a nonzero default value while consensus develops. EPA and CARB are developing models that are fundamentally similar to Searchinger et al in that they use global economic agricultural models. They should use their best estimates and set a schedule for updating them as we learn more. Even an indirect land use value of one fourth of what Searchinger et al. predicts could have significant implications for near term policy decisions, and setting that value to zero will send the wrong signal.
Promote fuels that use land and energy efficiently. Fundamentally, the biofuels with the most potential are those that use both energy and land efficiently. Current lifecycle accounting does a good job accounting for energy inputs, but the recent literature suggests we have not accounted for land use adequately. However, even before the accounting is complete, we can make some judgments about biofuels that use land more efficiently. Biofuels made from waste streams from the agricultural, forestry products, and municipal waste appear to be a better bet from a land use perspective. And bioenergy crops that take land unsuitable for agriculture and improve it appear to be the best bet of all. While these resources appear positive from a climate perspective, broader impacts must be considered before moving forward with their use, as outlined in the UCS “Principles for Bioenergy Development.”
Fund research to improve our ability to measure land uses changes globally. Several areas of research are key to improving the measurements of land use. The developing area of satellite and aerial imagery based land use measurement is critical to accurately and objectively measure changes in land use and accurately estimate ecosystem properties of different land uses including carbon cycling, nitrogen and methane cycling and carbon sequestration. The other critical research area is economic modeling of the impact of biofuel production on land use decisions worldwide, and how this affects food prices and availability, greenhouse gas emissions, deforestation, nutrient runoff, water use and other important outcomes. There are many open questions about how to estimate and aggregate impacts from land use and land conversion, and this area of research will be import to biofuels lifecycle accounting and climate change action generally.
In the long term we need to keep an open mind about the scope of biofuels. Today’s best science suggests that biofuels from many resources can play a role in reducing global warming pollution. The Federal Renewable Fuel Standard calls for 21 billion gallons of advanced ethanol, which would require about 300 million tons of biomass. Based on current estimates, this amount of biomass can be obtained from waste products such as agricultural residues, forestry residues, and municipal and construction waste3. However, expanding far beyond this level must be based on sound scientific estimates of sustainable biomass resources. There are competing uses for biomass for other purposes including electrical power generation, biogas, and chemical feedstocks. And dedicated bioenergy crops will compete with traditional uses for agricultural products as food, feed and fiber. There are also ecosystem services that are needed including water purification, carbon sequestration, nutrient cycling, biodiversity and recreation. As biomass utilization increases in new areas, and intensifies in traditional areas, competition between these uses must be understood. Over-utilizing renewable resources can transform a potential solution into a major problem. We need to ensure that renewable resource policies comprehend this and strike the right balance.
For more information contact Jeremy Martin or Eli Hopson at 202-223-6133 |
