Biofuels and Climate Change: Pulpwood to the Rescue?

November 18, 2013 11:40 PM

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Biofuels and Climate Change: Pulpwood to the Rescue?

The debate has been raging for years. Can biofuels, fuels derived from recently alive plant materials (or manure), serve as the fuel of choice to power our nation's huge fleet of automobiles and trucks and power plants without adding to our climate change woes?

In principle the answer should be yes. Because the carbon in plants is produced from taking carbon dioxide (CO2) out of the atmosphere via photosynthesis, burning those plant-derived fuels simply puts the same amount of CO2 back in the atmosphere -- sort of like no harm, no foul.

Burning fossil fuels, on the other hand -- fuels derived from the remains of plants and animals that lived between a million and hundreds of millions of years ago (way before the dinosaurs, by the way) -- adds carbon to the atmosphere, carbon that was buried long, long ago, and so results in a net gain of CO2, and in the climate change game, most definitely a foul.

But being a winner in principle and being a winner in practice are two different things. In the first place, growing the biofuel feedstock and converting it to a biofuel consumes energy and emits some CO2. This arises from the energy needed to manufacture fertilizers and fossil fuels used to plant, harvest and transport. But calculations indicate that even after taking that into account, biofuels do better than fossil fuels from a climate point of view. So all is copacetic on biofuels?

Not so fast, say a host of papers. (See here, here, here, here and this paper here on which I am a co-author.) Advancing an idea based on the so-called Searchinger Hypothesis after Tim Searchinger (a former colleague who is "generally ... credited with reshaping the world debate on bioenergy"), these papers argue that, once one takes land conversion into account, the biofuels climate picture goes from a positive to a negative.

More specifically, the argument goes something like this: When we take crops normally used for food, and use them as feedstock for biofuels instead (e.g., corn ethanol or soybean biodiesel), that can create a food supply deficit. To make up for this deficit, farmers somewhere will cultivate more crops, and to cultivate more crops, the farmers must farm on land not currently under cultivation. And that conversion of land from non-agricultural to agricultural can effectively create carbon emissions.

For example, when a forest is cut down to grow those new crops, there are significant releases of carbon, carbon that would have otherwise been stored in the forest. Thus this scenario represents a heretofore unaccounted for flow of CO2 into the atmosphere (a case of indirect land use). Accounting for these emissions, the advancers of the Searchinger Hypothesis claim, tends to make biofuels no better than, or even worse than, just using fossil fuels.

Some have attempted to solve this conundrum by proposing to use only marginal lands to grow advanced biofuels -- leaving prime agricultural land for food. Sounds good, but I'm not sure this will work -- it's simple economics. If farmers can earn more income by growing fuel than crops, it's hard to believe they wouldn't convert prime croplands to grow fuels. Certainly, as these headlines indicate, U.S. farmers in recent years have been producing more corn in response to the U.S. mandate for ethanol (except in 2012 because of the drought): “2007 Corn Crop a Record Breaker, USDA Reports,” “2009 Crop Year is One for the Record Books, USDA Reports” and “U.S. CORN ACREAGE IS UP IN 2011.” And there’s more of the same in the latest corn report for 2013. (Not only has growing more corn affected food production, a recent report by The Associated Press found that "As farmers rushed to find new places to plant corn, they wiped out millions of acres of conservation land, destroyed habitat and polluted water supplies.")

It would appear that our recent biofuel journey has been problematic. Disrupted food markets, concerns about emissions from land conversion, and mandates that are in search of demands. But a new report released by the nonprofit think tank Resources for the Future foresees a stronger future for biofuels. Specifically, Roger Sedjo and his co-authors conclude that, based on two modeled scenarios,

"industrial forests and supplemental dedicated fuelwood plantations ... can economically produce large levels of biomass [to provide biofuels] without compromising crop production, thereby mitigating the land conversion and carbon emissions effects posited by the Searchinger Hypothesis."

The authors’ conclusions are predicated on their argument that there are more than enough non-agricultural and marginal lands available to produce enough biomass to meet biofuel demands, keeping the price for biomass feedstocks low enough to make it unprofitable for farmers to switch from growing food crops to growing biomass for biofuels.

A key and critical assumption underpinning the Sedjo et al. argument is that the technology for producing biofuels from cellulosic material (as opposed to sugars from crops like corn) will advance enough to make biofuels generated from cellulose economically viable. If this occurs, the models used by Sedjo et al. predict there would be copious amounts of biomass from grasses and trees grown on marginal lands, enough to meet demands for biofuels through 2060.

So it may turn out, with cellulosic ethanol in play, that biofuels are preferable to fossil fuels. But I've got something that beats out both: Cars that drive with fewer gallons per mile and drivers that drive fewer miles.


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