Biomass — Rarely a carbon neutral energy option

The forests, not just the trees, provide ecosystem services that are valuable and irreplaceable.

The Manomet Center for Conservation Sciences recently released a report commissioned by the state of Massachusetts that investigates greenhouse gas impacts of biomass energy. Quite predictably, the report has been greeted with both howls of protest and shouts of righteous glee.

The howls come from wood energy developers who’ve long enjoyed both direct subsidies and exemption from emissions regulations, under the mistaken assumption that biomass is always a carbon-neutral energy option. Gleeful, on the other hand, are biomass opponents who latch onto the opposite conclusion that wood-based energy is worse than even the dirtiest coal in terms of greenhouse gas emissions. Of course the real story is a complex one, and Manomet and its partners have done a stellar job of explaining the key variables that determine whether wood is a climate-friendly energy option.

Important principles to consider include:

  1. Pay attention to what’s happening in the woods — the more carbon we can keep in place in trees (alive and dead) and in downed logs and soils, the better for the climate.
  2. See the forest and not just the trees — other ecosystem services provided by forests may be more valuable and irreplaceable than kilowatts.
  3. Use wood to replace the dirtiest fossil fuels, rather than to undercut even better energy solutions — such as efficiency investments or lower carbon alternatives like geothermal or solar.
  4. Focus on technologies that get the most British thermal unit energy for each cord of wood burned — generating electricity without capturing the waste heat is an insult to the tree.
  5. There is very little real “waste” in the current system (remember that grumpy old economists’ phrase, “There is no such thing as a free lunch.”) Smart mill owners who’ve survived thus far in a competitive industry already sell their bark and trim pieces to somebody or use it themselves to generate process energy. One person’s cull tree is another’s forest fertilizer or home to a woodpecker. And not every landowner is willing to mow down the back forty for $2 per ton.
  6. Keep wood energy in perspective — the only permanent solution has to address out-of-control energy use. Each year, Americans consume twice as much energy as all the green plants growing across our entire country collect from sunlight.

The bottom line is that in the short run, replacing fossil fuels with biomass does not reduce greenhouse gas emissions. In fact, the burning process itself releases more carbon dioxide than all fossil fuels except some types of coal. There is no guarantee that human demands and climate stresses, combined with natural disturbances will allow forests to repay that combustion debt over time. Subsidizing biomass energy without applying sustainability standards  — including careful carbon accounting  — is likely to cause damage to our forests and make global warming worse.

photo: Anan Bay - the forests, not just the trees, provide ecosystem services that are valuable and irreplaceable.