Biofuels produced from switchgrass and post-harvest corn waste could significantly reduce the emissions that contribute to climate change, according to an analysis by EWG and University of California biofuels experts.
EWG’s analysis found that the life cycle carbon intensity of cellulosic ethanol from switchgrass was 47 percent lower than that of gasoline. Ethanol made from corn stover – the leaves and stalks that remain in the field after the grain is harvested – has a life-cycle carbon intensity 96 percent lower than gasoline’s.
By contrast, studies have found that the life cycle carbon intensity of corn ethanol is greater than that of gasoline (Mullins et al. 2010, EPA, 2010a). Yet current federal policies strongly favor the production of conventional biofuels such as corn ethanol at the expense of lower-carbon alternatives.
Congress should reform the federal Renewable Fuel Standard to eliminate the mandate to add corn ethanol to gasoline and should further reform the standard to accelerate development of biofuels from lower-carbon feedstocks. At the same time, Congress should adopt new protections to ensure that fuels from grasses and crop waste also meet soil and water quality goals.
If Congress fails to act, EPA should employ the “reset” provisions of the Renewable Fuel Standard to gradually reduce the mandate for corn ethanol and encourage development of lower-carbon second-generation fuels.
A bunch of biological activity happens, organism reproduce, grow, die. Some of this biomass turns into oil, natural gas, or coal. I’ve left out few details.
During certain periods in the Earth’s history, this happened at a much larger scale that usual, and in certain geographic and geological settings, leading to the eventual formation of huge underground oil reserves, coal fields, gas reservoirs, or bitumen deposits. By the way, some of these 10 million year or so long moments in geological history were probably regional extinction events.
That is how we get fossil Carbon based fuels, for the most part (again, I oversimplify).
An alternative, it seems, is to intervene early in the process. Take the organisms out of the system early, when they have just grown, and turn them into biofuels. Trees or other material can be burned, plant tissues can be converted to liquid fuel or gas, etc. This method is inherently limited compared to using fossil fuels because the fossil fuels were generated over tens or hundreds of millions of years, while this form of biofuel is being generated real time. In order to continue to use energy at the rate we currently use it, with all the energy coming from biofuels, we’d have to be scraping a huge percentage of the output of photosynthesis every day.
To put this in perspective, consider that the total amount of energy that natural systems using photosynthesis on the Earth produce is about six times of what we humans use in energy, from fossil fuels, nuclear, hydro, and various clean energy sources. In other words, if we used only biofuels for our energy, we would have to use one sixth of the energy the entire natural world currently produces, assuming efficiency matched to what nature does. It is likely that some of that use would enhance natural production, or could be used harvested more efficiently, but the differences can’t be large. Maybe we’d only need a seventh, instead of a sixth, of the Earth’s natural photosynthesized production. Or, maybe we would be using it less efficiently and thus need more.
Having said that, there is a certain amount of potential biofuel that goes from some use or another into the trash (or sewer effluence). When we capture that energy, we might be reducing a carbon sink, but we are at the same time using a non-fossil Carbon based fuel source. This includes using discarded cooking oil, or burning sawdust or trash in waste to energy plants.
Western governments have made a wrong turn in energy policy by supporting the large-scale conversion of plants into fuel and should reconsider that strategy, according to a new report from a prominent environmental think tank.
Turning plant matter into liquid fuel or electricity is so inefficient that the approach is unlikely ever to supply a substantial fraction of global energy demand, the report found. It added that continuing to pursue this strategy — which has already led to billions of dollars of investment — is likely to use up vast tracts of fertile land that could be devoted to helping feed the world’s growing population….
The report follows several years of rising concern among scientists about biofuel policies in the United States and Europe, and is the strongest call yet by the World Resources Institute, known for nonpartisan analysis of environmental issues, to urge governments to reconsider those policies.
Emily S Cassidy, Paul C West, James S Gerber and Jonathan A Foley, from the University of Minnesota Institute on the Environment, have produced a very important study for IOP Science Environmental Research Letters. (This is OpenAccess so you can access it openly!) You know Emily as one of the participants in our CONvergence panel on food last July. The research Emily and her colleagues do is some of the most important work being done right now, because it is about the food supply.
The bottom line is this: When we look at our food supply, we find that a large amount of what is grown in agricultural fields does not make it into the stomachs of people. There is a lot of waste, there are problems with delivery and distribution, and so on. But what this study looks at is the percentage of potential calories that go to non-food final products, or do get into our diets but do so in a way that significantly reduces the efficiency of the system. There has been a huge increase (percentage wise) in how much field crop is used for biofuels instead of food, but the total amount now is still only 4%. Also, one could argue that this is good use of field crops if the production of biofuels reduces carbon emissions (which is only partly the case). More importantly, a huge amount of the corn and other crops (but mainly corn) that is grown is used as animal feed, and only about 12% of that, in terms of calories, ends up in the human diet. The reduction is because as we move up trophic levels, energy is taken out of the flow.
This graphic from Cassidy et al shows the distribution of calories across food and non-food destinations:
The graphic at the top of the post is also from the paper, and has this caption: “Figure 1. Calorie delivery fraction per hectare. The proportions of produced calories that are delivered as food are shown.” The thing to note here is the unevenness across the globe in efficiency of calorie production-to-plate. There seems to be a latitude effect, and I wonder if that has anything to do with the environment and seasonality. But the largest contributor to this variation in efficiency is probably simply the amount of meat in regional diets. As Emily points out in the video that accompanies the paper, even small changes in dietary practices can result in large changes in ultimate agricultural productivity.
We, as a species, need to eat less meat. In particular, certain groups of people, like Americans, need to eat less meat. So let’s do that: Eat less meat!
As an aside, Emily is a friend and colleague and I’ve been really impressed with her work and have been very excited to see these important results coming out. Go Emily! (And co-authors, of course.)
Cassidy, Emily, West, Paul, Gerber, James, & Foley, Jonathan (2013). Redefining agricultural yields: from tonnes to people nourished per hectare IOP Science, 8 (2) DOI: 10.1088/1748-9326/8/3/034015