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Thursday, May 2, 2013

Is energy from wood really carbon neutral? And is that reason enough to use it?

The US Energy Information Administration has forecast that biomass energy production in the U.S. will grow from 8 percent in 2009 to 15 percent by 2035, driven mainly by state renewable fuel standards. Seen as a tool to combat climate change, biomass energy is generally assumed to be carbon neutral - that, for example, carbon emitted into the atmosphere when biomass is burned for energy generation will be recaptured by plant growth. 

But is burning wood from forests to generate electricity really carbon neutral?

Resources for the Future (RFF) has published a study - Comparative Life Cycle Assessments: Carbon Neutrality and Wood Biomass Energy  that seeks to answer that question.

And the answer is – it depends.

Different studies use different methodologies and different assumptions, RFF says, affecting conclusions. Further, some studies ignore the fundamental element of time:

“although net emissions may be zero over long time periods, they often will not be zero in shorter time periods...Thus, the implication is that the use of wood biomass for energy will imply no net forest emissions to the atmosphere given adequate regeneration and sufficient time.”

Think less than 100 years as “shorter time periods.” The world could be 11 degrees warmer before then.

Whether forest stands used for electricity feedstocks are sustainably managed - another big “if” - greatly impacts carbon neutrality, according to RFF.

And there are other problems to consider besides carbon neutrality when using humans’ most primitive source of external energy for 21st century purposes. Wood-fired electricity generation emits more CO2 per unit of energy generated than fossil fuel facilities, and significant levels of other air pollutants. And forests provide multiple additional ecosystem services – a term I actually dislike because it reduces valuation of forests to mostly utilitarian terms – like cleaning the air and filtering water supplies, as well as hunting, fishing, and outdoor recreation. Do the very limited benefits of energy-from-wood outweigh those losses? Plus, older forests may be better at storing carbon than younger ones, and young to middle-aged forests can best help with carbon storage if they are used for long-lived forest products like buildings and furniture - not burning them to charge your iPod.

So, burning wood to generate electricity – depending on how you look at it – may be carbon neutral. But that is not nearly enough to allow it to be more than a niche, small-scale energy source. I’m of the view, all things considered, that forests are not fuel.

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