For bioenergy to reduce greenhouse gas emissions through plant growth, it must lead to additional plant growth.
I have been seeking authoritative but accessible sources on whether the current fashion for biofuel subsidies and mandates is a good idea or a bad idea. Questions: are biofuels…
- Mitigating GHG emissions for transportation fuels?
- Raising food prices for the poor?
- Threatening global forest cover?
- Negatively impacting soil quality?
- Negatively impacting fresh water supplies?
- What if cellulosic biofuels can be made to work at scale?
To cut to the chase, I have concluded that encouraging biofuel production may be good for farmers but biofuels are bad for humanity and bad for the planet. While there are some exceptions, my main concern is the broad sweep of public policy, which I find in the rich world to be going in the wrong direction. If you are also wishing to know the scorecard for biofuels I have some sources to recommend. First is the captioned January 2013 workshop organized by the USA National Academy of Sciences. This workshop was convened specifically to investigate the current state of knowledge on biofuels. The workshop proceedings are available at The National Academies Press: The Nexus of Biofuels, Climate Change, and Human Health where you can purchase the paperback for $35, download the free PDF or read online. The Workshop video is all available on YouTube in 48 segments.
There is a heap of depth in the proceedings so you will be rewarded if you can invest a few hours digesting. For motivation here are a few excerpts from the beginning of first presentation — which is by Timothy D. Searchinger (see end note).
Many governments around the world have either goals or mandates for biofuels, Searchinger said, and if these goals and mandates are met, biofuels will account for about 10 percent of the world’s transportation fuels by 2020. This represents about 2.5 percent of the world’s total energy budget, but Searchinger said, when the energy that it takes to make biofuels is taken into account, biofuels would be providing about 1.7 percent of the world’s delivered energy by 2020.
How much of the world’s crops would that take? By 2020 biofuels would require that about 26 percent of all the energy contained in the present production of the world’s crops. By 2050 that figure would rise to 36 percent, he added. “So, that gives you some idea of the challenge, which is that it takes a large amount of biomass to get a small amount of energy.”
Of course, liquid biofuels are only one form of bioenergy that people are interested in, he noted. For example, there is also a big push in Europe as well as in some U.S. states to produce electricity from wood products.
Governments are encouraging the use of bioenergy in various ways. The European Commission has required, for instance, that 20 percent of all energy in Europe be renewable by 2020—not just the energy from utilities, but all energy. It is expected now that more than half of that will come from bioenergy, Searchinger said. A number of states have renewable energy targets, he said, although they are not quite as stringent and are just for electricity.
The Effect of Biofuels Usage on Carbon Dioxide Levels
One of the main reasons that people support the use of biofuels, Searchinger said, is the belief that “when you switch from burning a fossil fuel to burning a biofuel you get some kind of direct greenhouse gas benefit.” But, he said, a close examination indicates that this is not the case and that the belief that there is a direct benefit stems from an “accounting error.”
The belief that burning biofuels contributes less carbon dioxide to the atmosphere than burning fossil fuels stems from the fact that biofuels are derived from plants, which absorb carbon dioxide as they grow. “So, the theory is that, in effect, bioenergy is just recycling carbon, not emitting new carbon.” That is wrong, however, for the simple reason that land typically supports plant growth, whether it is used for bioenergy or not. For bioenergy to reduce greenhouse gas emissions through plant growth, it must lead to additional plant growth.
(…snip…) The key concept here, Searchinger said, is that the benefit from ethanol depends on the existence of an offset that makes up for the fact that producing and burning ethanol actually creates much more green- house gases than producing and burning gasoline. So, the question is: Is there really such an offset? It is true that growing corn leads to a certain amount of carbon dioxide being pulled from the atmosphere, but that is not all that goes into the determination of the offset. The critical requirement for an “offset” is that it be additional. No one can take credit for a carbon sink, such as a tree if that tree already exists anyway—in this case, regardless of whether the biofuels exist or not. One must take into account all of the circumstances surrounding the production of the ethanol and compare what happens when corn is being grown to produce ethanol to what happens when corn is not being grown to produce ethanol.
The first thing that must be considered is the land that is used to grow plants. “Land grows plants whether it’s growing those plants for biofuels or not,” Searchinger pointed out. “So, those plants are already up taking carbon if you’re growing it for biofuels or not.” Thus, the only way that there is a legitimate offset from growing corn for ethanol is if more plants are being grown on that same amount of land or, specifically, if more carbon dioxide is taken up by the corn crop than was taken up by whatever was growing on that land before the corn. “One way to think about it is that if you had a bare piece of land and you allowed it to grow as a forest, that forest would accumulate carbon, and it would reduce greenhouse gas emissions. On the other hand, if you simply had a forest that was growing anyway, you couldn’t count that as an offset.”
Ignoring this basic fact is a fundamental error that often appears in calculating the biofuels offset. “Biofuel analysis assumes typically that all plant growth offsets biofuels, rather than only additional plant growth,” Searchinger said.
(…snip…) The most effective approach would be producing cellulosic ethanol—ethanol produced from wood or grasses—on the land, but even in that case, Searchinger said, “you’re simply matching the opportunity cost of using that land for another purpose.” And if the cropland is created by clearing forest, there is a much greater cost in greenhouse gases because plowing up forests will release 12 to 35 tons of carbon dioxide per hectare each year for 30 years. Thus, the best-case biofuels scenario would be to take fallow land and use it for the production of cellulosic ethanol, he said, but even in that case it is only a break-even situation if the land would otherwise come from abandoned land, and it would increase emissions if the land used was previously forest. There is no offset.
In short, out of the three possible indirect effects of growing corn to produce ethanol, Searchinger said, two are bad. (…snip…)
Biofuels and Food Consumption
Interestingly, although reduced food consumption would not appear to be a desirable result, it is exactly what is assumed in the major models used to predict the greenhouse gas effects of biofuels, Searchinger said. “You have to find this deeply in the data,” he said. “It’s generally not reported. Take, for example, the Environmental Protection Agency [EPA] analysis of corn ethanol, which found relatively little land-use change compared to some other studies. One reason it didn’t find as much land-use change as other studies is that it actually estimated that a quarter of all the calories that are diverted to ethanol aren’t replaced.”
Similarly, the model used by the California Air Resources Board assumed that more than half of the calories from the corn diverted from human and animal consumption to ethanol would not be replaced. A major model used by the European Union assumes that a quarter of the calories from either corn ethanol or wheat ethanol are not replaced.
Thus, the greenhouse gases benefit from using biofuels, as calculated by these models, depends on humans and animals eating less, expending less energy, and thus breathing out less carbon dioxide (and producing less methane). “If you were to eliminate these savings,” he said, “you would not have greenhouse gas savings according to all these models.”
Of course, he noted, the decreased consumption assumed by these models is not a desirable effect because there remains a great deal of hunger in the world—roughly 900 million people are hungry according to recent estimates. Thus, it is particularly worrisome that the frequency of food crises worldwide has essentially tripled since 2005, when the amount of biofuels use began to increase sharply. And according to a recent report by the High-Level Panel on Food Security, of which Searchinger is a member, that is not a coincidence (HLPE, 2013). “We basically conclude that biofuels are the dominant source of food price increases.”
In particular, the increase in corn prices in the United States can be traced to the cost of oil combined with government tax credits for ethanol production. With crude oil at $80 per barrel and with the current U.S. tax credits for ethanol, it is economical to use corn to make ethanol and to replace gasoline until the price of corn reaches about $6.80 per bushel. “Roughly speaking,” he said, “this is a 275 percent higher price than the long-term corn price in the first part of the 2000s.” Thus, corn prices get bid up until they get close to that level—and as the price for corn intended for ethanol production increases, the price for corn intended for consumption increases along with it, for the crops are the same. Furthermore, as the price of corn increases, the price of wheat and soybeans—and, to a lesser extent, rice—track the price of corn very closely because the crops can, to a significant extent, be substituted for one another. “So, this force by itself is perfectly adequate to explain the vast majority of the price rise that we’ve had,” Searchinger said.
To produce all the crops needed by 2020 for both food and biofuels without any change in land use will require a doubling of the historical yield growth rate, Searchinger said, “and that’s not going to happen.”
What would be the impact of actually achieving EU 2050 goals for biomass and biofuels? The 80% renewables goal is 12% of Total Primary Energy would be biomass. Yikes, what a disaster that would be!
The real challenge with bioenergy, Searchinger said, is that photosynthesis is extremely inefficient. “If you’re really lucky you get half a percent of the solar energy transformed into plant biomass—that’s extraordinary achievement over the course of the year. And eventually maybe a tenth or two-tenths of the original solar energy will end up actually in delivered energy like electricity.” By contrast, a solar cell turns 10 percent of solar energy into electricity. “So, compare one-tenth of 1 percent with 10 percent, and you’ll get an idea of the inefficiency of using land. What that means is it takes a tremendous amount of land to make a small amount of bioenergy.”
The bottom line is that to provide 10 percent of the world’s transportation fuel by 2050 would require 36 percent of all of today’s crop production, and it would amount to less than 2 percent of the world’s delivered energy at that time.
Another way of looking at the inefficiency is that the EROI of biomass is so low (by a factor of two) that it makes a negative contribution to supporting a modern industrial economy. This chart is discussed in The Catch-22 of Energy Storage and EROI — A Tool To Predict The Best Energy Mix:
Timothy D. Searchinger, J.D., is a research scholar and lecturer in public and international affairs at Princeton University’s Woodrow Wilson School. He is also a Transatlantic Fellow of the German Marshall Fund of the United States. Timothy D. Searchinger is a Senior Fellow at the World Resources Institute and serves as the technical director of the next World Resources Report.