from Worldwatch Institute - Independent research for an environmentally sustainable and socially just society. by Raya Widenoja
The new U.S. Renewable Fuels Standard (RFS), signed into law last month as part of the revised Energy Bill, sets high goals for the U.S. biofuels industry. It calls for the production of 36 billion gallons of biofuels—mainly ethanol and biodiesel—annually by 2022, with 21 billion gallons coming from so-called “advanced biofuels,” which can be produced using a variety of new feedstocks and technologies. Of this, roughly 16 billion gallons is expected to be from “cellulosic biofuels,” derived from plant sources such as trees and grasses.
But are these biofuels targets realistic, and can they be met without serious impacts on the nation’s farmlands, forests, waterways, and rural communities? The answer is complicated, but fortunately the RFS bill contains a few key caveats that can be used to “stop the buildup” if things go wrong.
An Ambitious Mandate
First, for biofuels to qualify for the RFS, they have to meet certain greenhouse gas emissions requirements. Ethanol derived from corn has to achieve at least a 20 percent reduction in lifecycle emissions compared to gasoline, and biodiesel and advanced biofuels have to reduce their emissions by 50 percent compared to the petroleum fuel they would replace. Cellulosic biofuels have to achieve at least 60 percent lower emissions.
Second, the emission reductions have to be based on lifecycle studies—that is, calculations of all the emissions that result from making the fuel, from the field to the tank. Perhaps most importantly, the bill specifies that emissions from changes in land use must be considered—a factor that was not included in most early studies of the climate impact of U.S. biofuels. Land-use changes can have a profound influence on the net climate impact of a biofuel, particularly if the feedstock for the fuel was grown on newly converted land that had been storing large amounts of carbon in its vegetation and undisturbed soils.
Third, the RFS bill states that an administrator should “re-evaluate” conditions annually and adjust the fuel mandate and emissions requirements if the impacts on the land or the economy from increased production end up being higher than the benefits.
Room for Improvement
Although the sustainability requirements in the new RFS are far from perfect, these three caveats at least provide openings to demand more improvements. And there are many improvements that can be made to ensure that biofuels reach their potential for sustainable production.
For example, the latest data on cellulosic ethanol made from switchgrass grown on marginal lands shows that the fuel will achieve emissions reductions of about 94 percent compared to gasoline. So why is the RFS content with only a 60 percent reduction? Why doesn’t it provide producers with an incentive to aim for the 94 percent reductions that the technology promises? Fortunately, as concerned citizens, we do have a lever for demanding higher standards and other improvements, since the new biofuels mandate and emissions requirements must be reviewed regularly.
The next obvious question about the sustainability of the new RFS is why the law allows corn ethanol to keep qualifying up until 2022, with its measly emissions reduction of just 20 percent compared to gasoline? Considering the mounting evidence of the inefficiency of producing ethanol from corn, and of the negative impacts of producing more and more corn, the most obvious answer is that Midwestern politicians want to appease the corn lobby rather than help the United States create a clean and renewable energy supply.
Meeting Long-term Goals
Which brings us back to my original question: How realistic is it that the United States can produce 36 billion gallons of biofuel annually by 2022? The answer depends in large part on the technologies and feedstock used, among other factors. For the sake of simplicity, and because the long-term goal is to use mainly cellulosic technologies, let’s consider whether the country will be able to produce 36 billion gallons using cellulosic biofuel technologies. That gives a better idea of the long-term value of the RFS, and of whether even the proposed 16 billion gallons of cellulosic ethanol is realistic. To further simplify the response, I will use estimates that apply to cellulosic ethanol derived from switchgrass.
Although cellulosic biofuels are still under development, the first commercial projects are expected to start producing in 2009, and researchers know both the theoretical yields and the current actual yields of cellulosic ethanol from switchgrass. Using biochemical methods (hydrolysis and fermentation), each dry ton of switchgrass can in theory yield 111 gallons of ethanol. Using thermochemical processes (gasification, pyrolysis, and deploymerization), the theoretical maximum is 198 gallons. In practice, researchers today estimate getting 100 gallons per dry ton of switchgrass, roughly double the 50 gallons a ton produced in pilot projects just a few years ago.
According to a 2005 government study of the total available biomass in the United States—known as the “billion ton study”—roughly 1.3 billion tons of cellulosic biomass could be harvested sustainably nationwide each year by mid-century. If this 1.3 billion tons were converted to fuel at 50 to 100 gallons a ton, the United States would produce between 65 billion and 130 billion gallons of cellulosic ethanol.
However, the billion-ton study uses aggressive assumptions about crop productivity and the use of residues from agriculture and forestry, which makes it quite likely that its estimate of available biomass for sustainable harvest is too optimistic. Figuring out how much of this billion tons could actually be harvested economically without increasing environmental problems will likely take many more years of research.
Another way to answer the question is to estimate how many acres of switchgrass it would take to hit the 36 billion gallon goal with cellulosic ethanol. Most of the switchgrass grown intentionally in the United States today is in the Conservation Reserve Program (CRP), which encompasses about 34 million acres, a tiny fraction of the country’s total agricultural land. If the average switchgrass yield is 3 tons per acre (as one study suggests, assuming that marginal land is used and that some biomass is left on the fields), and the ethanol is converted at 100 gallons a ton, then 120 million acres will be needed to produce 36 billion gallons of fuel. This is a large amount of land, though, for comparison, it represents only 15 percent of the total U.S. land currently used for grazing livestock.
But if the average feedstock yield is 10 tons an acre, rather than just 3, which could be realistic using a different grass variety or better-managed switchgrass, then only 36 million acres would be needed to meet the RFS. This is still more area than is currently enrolled in the CRP, but it represents only about 5 percent of the land used today for grazing, or 8 percent of the current cropland.
New Battles to Fight
So where does this leave the biofuel critic, or optimist? In no man’s land, as usual. Using 120 million acres for biofuel production is probably not sustainable and would impinge on food and environmental needs. Using 36 million acres sounds better, but if the feedstock is not grown with conservation in mind (i.e., if it degrades rather than enhances the land), then 36 million is far too much as well.
Necessity is the mother of invention, so the best way to make “sustainable biofuels” a reality is to give the inventors (the biofuel producers) precise standards they have to live up to—and to let them decide how to meet the standards. Only then, after all the standards are met, will we be able to accurately calculate the true volume of sustainably produced fuel. Creating clear frameworks to guide biomass “farmers” and biofuel producers will ultimately be more useful than attempting to make global estimates of how much land will be needed to meet our bioenergy goals.
Regulations to keep biofuels from causing more harm than good could include requirements to protect intact ecosystems and restore degraded lands, as well as limitations on chemical inputs like pesticides and inorganic fertilizers. Even just rewarding biofuel producers on the basis of their fuels’ lifecycle GHG emissions would go a long way toward reaching sustainability goals, if these measurements are done well and fairly.
That said, the next sustainability battle in the United States should not be about endorsing the benefits of one fuel over another, but about giving real incentives to the transport sector as a whole to lower its carbon footprint. If automakers had real sustainability incentives, they might direct more energy to developing plug-in hybrids and to using renewable electricity (derived from biomass) to power vehicle batteries. This approach to bioenergy—rather than the production of liquid biofuels—may ultimately be more useful for the transport sector, since more energy per unit of biomass can be captured in biomass electricity systems than in even advanced biofuels used in combustion engines.
However, liquid biofuels certainly have a part to play in bioenergy as well, even if plug-in hybrids become a reality this decade. Now that we have this ambitious RFS, which acknowledges the need to produce biofuels with a small carbon footprint and without causing social or environmental injustices, the next sustainability battles over the fuels should be about getting the law to look beyond the current minimum emissions reduction requirement of 60 percent for cellulosic fuels. Another useful battle will be about phasing out corn ethanol, unless it can meet emission reductions as great as the advanced biofuels. Since corn ethanol has been proven time and again to be the least efficient and least climate-friendly biofuel available, it seems unlikely that this turnaround will occur.
Raya Widenoja, a research associate at the Worldwatch Institute, is the lead author of the joint Worldwatch/Sierra Club report Destination Iowa: Getting to a Sustainable Biofuels Future.