Thursday, July 23, 2015

What Do We Know About the Carbon Neutrality of Wood Combustion?

CO2_Graphic

Some say that burning wood makes more carbon dioxide than burning coal. They've either got an agenda or lack the knowledge to make a more nuanced statement. It is a shock statement poorly applied to wood fuel for heating. Those who favor using wood fuel rebut that carbon dioxide output compared to coal is a largely factor of fuel moisture content. These discussions spiral into tedium quickly. In the real world many variables impact carbon calculations and the data can be manipulated for desired effect.

In the heating universe we should care little about such comparisons. Unfortunately, in our power-centric energy world, electricity policy often metastasizes to thermal policy, though power and thermal uses of wood fuel are very different. Carbon dioxide output by fuel weight is NOT the crux of the matter. The crux of the matter is how quickly wood is burned vs. how quickly it grows back.

If all of the carbon dioxide produced from burning wood is recaptured by growing trees there is a balanced, harmonious carbon cycle. That's the same old, irrefutable story.

"No!", say some. If a tree is burned, carbon dioxide is released quickly. It takes a long time for a tree to re-grow and sequester that earlier released carbon. That means that burning wood has delayed carbon benefits and our environment can't withstand delay.

We may never hear the end of these types of arguments.

What about sustainability? Huge tracts of forests are actively managed and harvested. Few tracts are untouched and left to become old growth. Austrians claim over 100 years of active and sustainable forest management and have one of the most robust wood heating industries in the world. However, I'm not convinced they've got sustainability figured out completely. If maintaining a stand of trees is sustainable, then maybe the Austrians have succeeded. Forest cover is increasing in Austria. Unfortunately, the forest is more than a stand of trees. And there is more to sustainability than carbon. What is truly sustainable involves detailed mapping of forest soils, understanding nutrient availability, and symbiotic ecologic relationships, among other factors that we don't fully understand. Consider that it has been less than a decade since we began to understand the importance of bacteria that inhabit our bodies. We often speak about sustainable forest management ensuring carbon neutrality, but we don't really know what is sustainable because we haven't been studying this topic long enough to know. Probably, forest management focused on carbon absorption through rapid growth is not actually sustainable given so many other factors that impact forest health.

It is also no small matter that well maintained forests in the developed world might need to pull more than their own weight when it comes to carbon. Huge tracts of forest in the developing world are being turned to field, or worse, desert. Do healthy forests need to add carbon at double time? How quickly will the forest health equation change as global air composition and temperatures change? Sustainability is not easy to define and carbon emission is a global topic.

There is big money in carbon neutrality- big tax credits, big rebates, big grants, and big private investment. Unfortunately, investments in the biomass heating industry hang in the balance waiting for determinations about carbon neutrality. In reality, carbon neutrality may be the least tangible and most divisive policy tool for the biomass heating industry to focus on.

Here's the rub as I see it: We place far too much emphasis on carbon neutrality. I understand the politics. Sometimes we say and do things to swing the pendulum, but we need to be honest with ourselves. There is a lot more to forest based energy than carbon.

While using best management practices, increasing the utilization of wood for heating fuel should be an important energy policy in forested northern regions where fuel is for practical purposes, just out the back door or just down the road. Most expenditures on wood fuel for heat stay in the regions where the wood is harvested. In rural areas, wealth retention is extremely important, as money easily flows out of regions that produce nothing. Of course, wood is almost always the least expensive fuel in rural areas. Profitable, properly managed forest harvests create disincentives for development, as managed forest harvests produce steady return on investment. Even a fundamental conservationist would rather see a working forest than no forest at all. Most working forests are also healthy forests.

Carbon neutrality is a handy lever for renewable energy decision makers, but for biomass thermal energy, carbon neutrality should not be a pass/fail criterion nor even a primary reason for deciding whether or not biomass thermal energy is worthy of investment. There are better reasons for feeling good about wood.

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Which would you choose?