Is biomass carbon neutral?

8 05 2012

Global climate change is the major environmental issue of current times. Evidence for global climate change is accumulating and there is a growing consensus that the most important cause is humankind’s interference in the natural cycle of greenhouse gases. (Greenhouse gases get their name from their ability to trap the sun’s heat in the earth’s atmosphere – the so-called greenhouse effect.)

CO2 emissions are recognized as the most important contributor to this problem. Since the turn of the 20th century the atmospheric concentration of greenhouse gases has been increasing rapidly, and the two main causes have been identified as:

  1. burning of fossil fuels and
  2. land-use change, particularly deforestation.

And now the world has discovered plants.  People seem to think there is some magic in nature – that they can keep taking and things will grow back.  We can buy “carbon offsets” to mitigate our guilt – trees planted to “offset” our energy consumption for, maybe, a plane ride to Hawaii.

Because the carbon emitted when plants are burned is equal to that absorbed during growing, it seems self-evident that biomass is a zero carbon (or carbon neutral) fuel.[1]  The thinking goes like this:  Plants are busy converting CO2 to stored (“sequestered”) carbon in their branches, roots, stems and leaves – so when that plant is burned, the carbon which is released (as CO2) is replaced by another plant which is busy sequestering that carbon.

Why is burning fossil fuel – which  also releases CO2 when burned  – not considered to be carbon neutral?  As far as I can tell, it’s a matter of definition.  Today, the definition of carbon neutral means that the greenhouse gases released  by burning fuel is the same or less than the carbon that was stored in recent history (translation = plants, which grow and mature within 100 years or so, i.e., “recent history”). Releasing carbon that was stored in ancient history, such as  burning fossil fuels (which comes from plant material millions of years old)  introduces extra carbon to the environment. Because fossil fuels contain carbon that was in the environment in ancient times, by burning fossil fuels we release greenhouse gasses that wouldn’t naturally be there!

That concept took off.  Beginning with the Koyoto Protocol, which overlooked reduction targets for biomass, others embraced the concept of using biomass as a carbon neutral fuel:  the EU Emissions Trading Scheme counts biomass as “carbon neutral” as do UK Building Regulations, the World Business Council for Sustainable Development and the World Resources Institute –  despite the recognition that this definition is problematic.[2]  Biomass burning is being ramped up all around the world in the name of green energy.

The concept of biomass as being carbon neutral is so popular that the European Union’s energy objectives for 2020 include the requirement that 20% of the total be from renewable sources, made up from biomass such as wood, waste and agricultural crops and residues.[3]  And the biomass industry in the US asked for an exemption from the Environmental Protection Agency’s greenhouse gas regulations because, it claims, biomass is carbon neutral.  In January 2011, the EPA gave them a 3 year exemption.

This loophole gives oil companies, power plants and industries that face tighter pollution limits a cheap means to claim reductions in greenhouse gas emissions. According to a number of studies, applying this incentive globally could lead to the loss of most of the world’s natural forests as carbon caps tighten.  A very frightening scenario indeed, since deforestation is responsible for up to 20% of the world’s greenhouse gas emissions – more than all cars, trains, planes, boats and trains in the world combined. [4]

I found a great blog post on this subject by Jeff Gibbs on Huffington Post Green, and I’ve relied on it for much of this post.  Here are just two of the issues:

Issue 1:  “Trees not harvested will eventually die and be decomposed by insects, fungi, bacteria, and other microorganisms which will release all the carbon dioxide that burning would. This cycling process has been going on for half a billion years, long before humans had a hand in it, and will continue with or without us.”

Here’s what Jeff Gibbs has to say:

  • “Actually nature has plans for that dead tree. For one it’s food for the next generation of forest life. And it turns out trees are pretty good at transferring their CO2 to the soil rather than the atmosphere when they fall over dead. Underground roots of mushrooms called mycorrhiza digest the wood and keeps the carbon the trees had sucked from the air in the forest soil.   The proof? It’s called coal.  Millions of generations of plants and trees have taken in carbon from the air and deposited it as mountains of coal. It’s what trees and plants do. Because trees and plants took the CO2 out of the atmosphere we have the nice comfortable climate we enjoy today. It’s not their fault we’re releasing everything they worked so hard to lock away, and if we cut then down they are going to have that much more difficult of a time soaking the carbon back up.”

Issue 2:  “Carbon dioxide –  released by burning biomass – is carbon dioxide that was taken from the air as the trees grew, and the trees that replace the harvested biomass will grow by taking in carbon dioxide again.”

This is so fraught with different issues that we have to break it down into manageable segments to understand why this is not as simple as it seems:

  1.   When you cut down a fully mature, multi-ton tree, how long do you think it will be before the one-ounce sapling that replaces it will be able to replicate the carbon uptake of the multi-ton tree?  Some trees take 100 years or more to mature.  When burned for energy, a mature tree (80-100 years old) takes minutes to release its full load of carbon into the atmosphere, but its replacement, if grown, takes a full century to re-sequester that carbon. For those 100 years, the CO2 is still aloft in the atmosphere helping push the climate toward the point of dangerous change, and yet carbon accounting rules treat it as non-existent.  After the initial release of carbon sequestered in a standing forest, a well-managed forest will start re-growing and at some point in time will achieve approximately the same concentration of carbon sequestration as the original forest.  But during that time, the atmospheric concentration of heat trapping gasses has been higher than it would otherwise have been, increasing associated environmental damages, and we have foregone the sequestration that would have happened in the original forest![5]
  2.  Chopping down forests to burn for ethanol production — even if replanted as tree plantations — is like biting the hand that feeds you. “Natural forests, with their complex ecosystems, cannot be regrown like a crop of beans or lettuce,” reports the nonprofit Natural Resources Defense Council (NRDC), a leading environmental group. “And tree plantations will never provide the clean water, storm buffers, wildlife habitat and other ecosystem services that natural forests do.”[6]
  3.  Recent studies show that there is more biomass contained IN the soil than in what grows ON the soil above ground.   This soil carbon can be disturbed and released by harvesting and reforestation activities.[7]
  4.  In a study published by the Manomet Center for Conservation Sciences, it was found that burning  trees emits about 30% more carbon pollution than coal, which the report calls the “carbon debt” of biomass. [8]   According to the study,  under normal forest management   it takes over 21 years just to re-absorb the extra pollution that is released in the first year of burning the wood.    Also, the energy content of biomass is about 40% lower than that of regular fossil fuels, so you need to burn more of it to get the same power, which means more CO2. (to read more about this, click here.)
  5.  It is simply not possible to plant sufficient numbers of trees to deal with the increased carbon dioxide emissions that are expected over the next half century.  According to Harpers Index, the number of years the United States could meet its energy needs by burning all its trees is … 1.
  6.  Recent evidence suggests that global warming itself is stressing ecosystems and turning forests and forest soils into failing forests and, in the long run, into net sources of CO2. Thus, if we don’t curb our use of fossil fuels, it won’t matter how many trees we plant because these forests will be overcome and die as the climate continues to warm.[9]
  7.  Old-growth forests are often replaced by tree-farm plantations that are heavily managed (including with chemicals and fossil fuel-intensive machinery) and do not offer the same biodiversity benefits as natural forests.
  8.  Investment in forestry offsets does not contribute to reducing society’s dependence on fossil fuels, something that is ultimately needed to address climate change. Responding to climate change means fundamentally changing the way we produce and use energy.
  9.  All biomass is not created equal.  According to Jeff Gibbs, some biomass plants burn old tires; others shovel in old houses and creosote soaked railroad ties. I don’t know what’s “bio” about all this but the energy you get is considered carbon neutral and renewable.

Here are Jeff Gibb’s seven truths that the Lorax would have us remember:

  1. Saving our forests (and that doesn’t mean more tree plantations) is the best way to stop global warming and save humanity.
  2. Deforestation is just as likely to result in the end of humanity as climate change and it’s right on track to do so.
  3. Burning things is the most insane way to stop global warming since doctors drilled holes in skulls to let the demons out and gave you a bill for it.
  4. There is no extra in nature and there is not enough “bio” on the planet to be burned, turned to ethanol, biodiesel or jet fuel, or bio-charcoal.
  5. Woody biomass falsely deemed renewable energy increases the CO2 in the atmosphere, destroys forests, and prevents renewables from being fully explored.
  6. Geo-engineering the forests, atmosphere or oceans to stop global warming isn’t going to work. We can’t even figure out how to stop carp from taking over a river or bugs from eating a forest.
  7. There is a possibility that the only way to heal the planet is to get control of our own numbers and consumption while letting nature do the work she has done for three billion years: run the planet.

[2] Johnson, Eric, “Goodbye to carbon neutral:  Getting Biomass footprints right”, Atlantic Consulting, Gattikon, Switzerland, November 2008.

[3] Neslan, Arthur, Guardian Environment Network, April 2, 2012. http://www.guardian.co.uk/environment/2012/apr/02/eu-renewable-energy-target-biomass

[4] Greenpeace, “Solutions to Deforestation”;  http://www.greenpeace.org/usa/en/campaigns/forests/solutions-to-deforestation/

[5] Natural Resrouces Defense Council comments with respect to draft Policy DAR-12, June 17, 2010.

[8] “Biomass Sustainability and Carbon Policy Study”, Manomet Center for Conservation Sciences, June 2010

[9] David Suzuki Foundation, Ibid.

Advertisements