Posted by: James Maloy | December 23, 2009

Biomass Incineration – A case study in Massachussets

By Mary S. Booth, PhD

I thought you might be interested to see the “Dear Congressman” factsheet I prepared back in April when I was in DC. Linking RECs from biomass to REAL carbon emissions is the last point on the sheet, but as it points out, this can only be done after true carbon accounting determines what the emissions are. It concludes “Renewable energy credits should be scaled accordingly”.

Burning woody biomass derived from native forests to generate energy will drive forest cutting to unsustainable levels and increase net greenhouse gas emissions. It will also increase dangerous air pollution. We encourage you to withdraw support from granting biomass unconditional renewable energy credits in the Clean Energy Act.

Some real numbers on biomass plants from Massachusetts: a case study

  • Number of biomass plants proposed: 4 – 5; Megawatts generated by proposed plants: 165[1]
  • Wood required: 2,145,000 tons per year; Minimum acres cut per year: ~ 45,000[2]
  • Equivalent number of trees cut per year: more than 9,000,000[3]
  • Amount of CO2 emitted: over 2,000,000 tons per year
  • Percent of Massachusetts energy to be generated: ~1%
  • Increase in CO2 emissions from the energy sector: ~10%

Air emissions from three Massachusetts plants currently in the permitting process:

  • 492 tons of NOx per year, which forms ground-level ozone
  • 98 tons of hazardous air pollutants
  • 165 tons of fine particulates

Biomass is not carbon neutral

When a 75-year-old tree is cut and burned, then it will take 75 years to re-sequester that carbon. The Intergovernmental Panel on Climate Change recognizes that forest cutting and burning increases carbon emissions, and that carbon released takes decades to re-sequester.

Biomass over-exploits forests and degrades their vital carbon sequestration capacity

A single 50-megawatt biomass plant requires about 650,000 tons of fuel a year. Brush from logging and other waste wood will not be enough to support large biomass plants – new trees will have to be cut. Research shows that forests sequester carbon best when undisturbed, and that recently cut forests are major sources of CO2.

Support these reasonable fixes in the Waxman Markey Clean Energy Act:

  1. Require biomass combustion for energy to undergo the same lifecycle analysis required for transportation biofuels, accounting for all CO2 emissions from harvest, transport, and forest disturbance
  2. Require that the assumption of carbon neutrality for biomass be qualified by consideration of the time required to re-sequester carbon released by burning. Renewable energy credits should be scaled accordingly.

[1] The state is planning for 165 MW, but in fact, plants representing 200 MW of generation are being considered.

[2] Using numbers from State of Massachusetts reports: it requires 13,000 tons of green woody biomass to fuel 1 MW of generation. Existing forestry residues in MA: 110,000 tons per year. Assume moisture content of green wood is 45% (so dry weight is 55% of green weight). Maximum amount of wood that can be extracted per acres (heavy thinning, leaving only large lumber-quality trees): 25 dry tons. Summary: [(13,000 tons  x 165 MW) – 110,000 tons] x 0.55 = 1,119,250 dry tons; divide by 25 dry tons/acre = 44,770 acres. At lighter harvest levels, more acres of cutting would be required. Use green wood weight and divide by 434 lbs, the average weight of trees too small for sawlogs: 9,377,880 trees.

[3] Massachusetts’ biomass availability study includes “forest residues” from 14 counties of surrounding states to make up supply for biomass plants. Our analysis does not assume that wood in other states is available to Massachusetts, or that it is economically viable to collect it. We calculate fuel use based on whole tree equivalents, since existing plants are already burning whole trees and planned facilities have whole-tree burning written into their permits.

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