Yesterday a group of scientists sent a letter to the head the the California Air Resource Board urging the agency to basically ignore the new and uncertain modeling showing that biofuels made from some feedstocks can actually increase global warming pollution. I know and have great respect for some of the folks that signed this letter, but this is not a responsible position.
Scientific uncertainty is not an excuse for in action. CARB and EPA, which is looking at very similar issues, should proceed with the best available data and modeling and not assume these emissions are zero.
The source of pollution that is at the heart of my friends' letter is the emissions from indirect land-use change. I've written extensively about the articles that brought this dynamic into focus here, here, and here (among others), but I'll cover the basics again. In February, Tim Searchinger and a group of researchers published an article attempting to quantify the GHG emissions that are caused when arable land is diverted from the food and feed market to produce fuels. The most fundamental dynamic here is the supply and demand of arable land--if some of the supply is taken out of the food and feed markets, the market strives to achieve a new equilibrium. There are fundamentally three options and some of each happens: demand goes down, the production of food and feed intensifies on the remaining acres, and new land is drawn into production.
As Searchinger et al. showed, the emissions from new land being cleared and cultivated for annual row crops can easily overwhelm the reduction in emissions from avoided fossil fuel production. The slides below summarize the traditional lifecycle analysis and Searchinger et al.'s results. (NB: if you view this in full screen mode on slideshare, you can actually see some of the small print.)
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While there is certainly is still much to learn about how to accurately model the impacts of land-use change, my friends and their colleagues are wrong about some of the areas and levels of uncertainty, and more importantly, they are wrong what CARB and EPA should do in light of this uncertainty. For starters, the letter includes some simple mistakes. At one point in their letter, they claim that Searchinger et al. ignore the production of distiller grains, which put most of the protein value of corn back into the feed market, but this is from Searchinger et al.:
First, not all corn diverted to ethanol has to be replaced by new crops. The analysis assumed that roughly one third of all corn diverted to ethanol would “come back” as feed in the form of dry distillers grains.
I'm sure that all the authors of the letter read the full article and the supplemental online materials, so I'm a bit stymied by this error.
They also make a big point over the fact that corn exports haven't actually gone down and in fact have gone up in some recent years when ethanol production has expanded significantly. But this misses two key points that Searchinger makes, which are that a) in the face of growing world demand for food, if biofuels reduce us to just treading water in terms of exports, we're actually falling behind and b) the gains in yield, which many have criticized Searchinger for under estimating, should actually be driving up exports.
The valid point made in the letter is that the type of modeling that Searchinger is doing is new. As the slides above show, he had to bring together three different data sets. There's only one other model out there, GTAP, that covers the same territory. Furthermore, while articles such as this make a strong case that the correlation between ag and forestry commodity prices and land-clearing are more than just coincidences, there not exactly an experiment you can run and repeat to prove the causal connection between some sources of biofuels and land-clearing.
Faced with this uncertainty, the authors argue:
Given that our only options for sustainably powering transportation with a significant reduction in transportation related greenhouse gas emissions are biofuels, batteries, and hydrogen, a presumptive policy implementation based on the current understanding of indirect impacts will have a significant chance to hurt real progress on reducing carbon emissions and decreasing our reliance on fossil fuels.
But what about the risk that ignoring these impacts will launch an industry in a way that is dependent on feedstocks that actually increase global warming pollution? Doesn't the precautionary principle dictate that we assume these emissions are not zero? I find the suggestion that we should take this risk on day one especially unnecessary given that there are ample feedstocks to launch the cellulosic biofuels industry that entirely or overwhelmingly avoid the land-use impact question. C&D waste wood, sustainable portions of agricultural residues and forest residues can all provide multiple billions of gallons and side step the land-use impact by having no impact on the food and feed markets. (By the way, the same dynamic will play out in the fiber market, that's part of why we have to make sure that our natural forest residues are really "precommerical slash and brush" as they are required to be under the new RFS.)
The tremendous complexities around biofuels are often painted with too broad a bush--this approach is evil, that approach will save the world. My friends have fallen into this trap by calling, even temporarily, for taking our eye off the actual performance of each type of biofuel as best as we can possibly measure it. Others have looked at the uncertainty around measuring land-use change emissions and argued that we should simply have a moratorium on all biofuels.
CARB and EPA have the obligation to chart the middle coarse here. They should use the best models and best data available and put a value the indirect land-use emissions of different feedstocks grown on different types of land. These values will be wrong and some may even be directionally wrong--positive when they should be negative and negative when they should be positive. However, the carbon stores in forests and grasslands around the world are so large and clearing practice are so destructive that I'm convinced that for the most part these values will move the industry in the right direction. There will be plenty of feedstock for the advanced biofuels industry to launch while CARB and EPA refine their numbers, and this much needed industry wont start down the path of doing more harm than good.