Global ChangeIntersection of Nature and Culture

In this week’s Science: Fixing a major flaw with biofuels

Thursday, October 22nd, 2009

There’s an interesting article in Friday’s issue of Science by a team of ecologists and environmental scientists arguing that the way we think about biofuels is flawed and can potentially lead to bad outcomes in mitigating climate change.

Here’ s the issue:  When we think of using, say, wood from forests or grasses from grasslands for energy, we normally think of this process as being carbon neutral–i.e., the carbon released when we burn the wood/grass will be taken back up by the regenerating forest/grassland.  No net change in atmospheric CO₂.  At face value, this sounds like a great strategy for dealing with atmospheric CO₂.

However, the authors indicate that the carbon accounting system in the Kyoto protocol, EU carbon trading system, and developing U.S. cap and trade plans makes a mistake in how biofuels are handled.  Specifically, because of the carbon neutrality of biofuels, the carbon accounting system simply ignores (1) the release of carbon to the atmosphere from biofuel burning and (2) the movement of carbon from the atmosphere back into regenerating forests and grasslands (or other biofuel crop).  At first glance, this appears to make sense: If burning biofuels is carbon neutral, just ignore the release and uptake of carbon since they cancel one another out.

There are two major problems with this–one ecological and another economic:

Ecological problem:

Let’s say we have a coal-fired power plant that we convert to a wood-burning power plant.  As the authors point out, the switch from coal to biofuels does not cause any less carbon to go up the smokestack.  Thus, we are still contributing carbon to the atmosphere, whether we burn fossil fuels or biofuels.  Over the course of the next several decades, regenerating forests will remove this carbon from the atmosphere.  Therefore, it’s important to note that while we have not added any net carbon to the atmosphere with biofuels, we also have not decreased our carbon emissions.  Thus, it’s easy to get lulled into a sense that we are reducing atmospheric CO₂ by using biofuels, when, in reality, we really are just not making the atmospheric CO₂ rise any worse.

If we want to reduce atmospheric CO₂ using biofuels, we can’t simply burn existing crops or forests and let them regrow.  Remember, that’s just carbon neutral.  Rather, we need to alter land use so that we generate a net sink of carbon somehow–for instance, by converting unproductive lands to productive forests or grasslands that could be used for biofuels. Here’s how:

• Step 1:  First, we reduce atmospheric CO₂ by converting unproductive land to a productive ecosystem with plants that grow better than before (i.e., add more biomass).
• Step 2:  Then, we maintain our energy system at carbon neutrality by harvesting and regrowing the productive trees and grasses over and over.

By adding step 1, we have created a net sink that actually helps reduce emissions.

Economic problem:

Recall the flaw in the carbon accounting system:  It is assumed that because biofuels are carbon neutral, they are omitted from the carbon accounting process altogether.  This sends a strong message that burning biofuels  is a zero emission process. As the authors state,

[T]he clearing of long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing large releases of carbon….When bioenergy from any biomass is counted as carbon neutral, economics favor large-scale land conversion for bioenergy regardless of the actual net emissions

Put another way, when framed as a zero-emission process, biofuels suddenly look very attractive.  It therefore creates strong incentives to make our energy production driven by biofuels.  This, in turn, leads to strong incentives to alter land use for the production of biofuels.

Another study this year in Science showed that when carbon mitigation strategies, such as carbon taxes, are only focused on fossil and industrial emissions, this creates incentives to increase biofuel energy. Why? Because in the existing carbon accounting process, biofuel emissions are not counted and therefore can’t be taxed.

Their models revealed the striking impacts resulting from this incentive:  The economic demand for biofuel crops soars, causing the conversion of almost all natural forests and grasslands to biofuel crops.  Our terrestrial biosphere would basically consist of deserts (15%), tundra (5%), a few managed forests (5%), and biofuels crops (50%) and food crops (25%).  That’s 75% of our land mass in some kind of crop.  The world as we know it would look like Iowa or Kansas!

In contrast, if terrestrial emissions from sources like biofuels were accounted for and taxed, there is no incentive to create a massive shift to biofuels because doing so costs money.  The result is we maintain land cover types much like they are today.

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Bottom line:  We should account for biofuel energy release of carbon to the atmosphere.  Doing so will remind us that we need to (1) make sure we create net sinks of carbon if we want biofuels to actually reduce atmospheric CO₂ and (2) account for all carbon flows that should be considered in mitigation strategies, thereby preventing perverse incentives to destroy our native forests and grasslands in favor of biofuel production.