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[GreenYes] Reply to Curt McNamara's Inquiry

I’m currently finalizing a life cycle analysis (LCA) of wood waste management alternatives for Seattle Public Utilities.  We are waiting on the latest update of EPA’s TRACI (Tool for the Reduction and Assessment of Chemical and other environmental Impacts) model which we plan to use to aggregate toxic and carcinogenic air pollutant emissions into toluene, benzene and 2,4-D equivalents.  This aggregation is like the aggregation that is done to add together carbon dioxide, methane, nitrous oxide, CFC and other greenhouse gas emissions into carbon or carbon dioxide equivalents. 


Based on the previous version of TRACI weights, combusting wood waste to replace natural gas reduced greenhouse gases, but increased toxics and carcinogens, versus landfilling the wood waste.  The same was true for coal, although the differences were much smaller than for natural gas, so that comparison could go either way with the updated TRACI weights.  These comparisons were for the combustion of wood waste, natural gas, or coal in industrial boilers.  The latest TRACI update apparently will be based on the United Nations Environmental Program (UNEP) and Society of Environmental Toxicologists and Chemists (SETAC) harmonization model for the impacts of chemical releases to the environment.  But we have to wait for EPA’s peer review of the update before that update will be available.   


I also have done the comparison for yard debris composting versus WTE incineration.  There the comparison favors yard debris composting, due to the upstream benefits from carbon sequestration and reduced synthetic fertilizer and pesticides usage as a result of building healthier soils from adding composts.  Composting of clean wood waste (i.e., non-painted, non-treated) would yield the same result.  (Several months ago I circulated an Excel-based model to interested GreenYes subscribers that shows these results.)


For the landfilling with landfill gas collection and use to generate electricity versus WTE incineration, the result favors landfilling wood waste and yard debris due to the carbon sequestration in the landfill of materials that are slow to decompose, such as wood waste and tree and plant prunings.


We expect to have the LCA for wood waste management alternatives completed early next year.  So stay tuned for that one.



Jeffrey Morris, Ph.D.-Economics

Sound Resource Management

2217 60th Lane NW

Olympia, WA 98502-0903



360-319-2391 mobile




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