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Comment 4 for To collect comments on the public health evaluation document of the Scoping Plan. (sp-pub-health-ws) - 1st Workshop.
First Name: Allen
Last Name: Dusault
Email Address: adusault@suscon.org
Affiliation: Sustainable Conservation
Subject: Methane digester air quality impacts.
Comment:
My comments relate to the passage below from the draft AB 32 Scoping Plan - Public Health Evaluation. "The anaerobic digestion of human, animal, or wet organic wastes produces a gas of 50 to 80 percent methane.This “biogas” can be combusted to produce electricity. Anaerobic digesters must also be controlled to limit emissions of NOx, particulate matter and carbon monoxide, as digester gas-based electricity generation generates 22 times the amount of NOx and 9 times the amount of PM as electrical grid natural gas power plants (per MWh). This statement is inaccurate for several reasons. First, digester that combust biogas for electricity generation provide baseload power that does not displace just central natural gas plants. They displace a mix of facilities that include biomass plants, legacy natural gas plants (with higher emissions), coal fired facilities, peaker plants, etc. A recent analysis we conducted showed the levels of emissions of NOx, PM and other pollutants from CA generated electricity mix was much higher than the central combined cycle natural gas plants. I believe CEC also has recent analysis of the "average emissions" from this mix that would be displaced. Importantly, nearly 20% of the mix of electricity we consume comes from out of state coal plants. I would presume that CARB would not ignore those emissions when assessing public health impacts. Those impacts include NOx in some cases over 1000ppm. They also include mecury, lead and dioxin that is displaced by biogas generated electricity. The public health and air quality benefits of that displacement should be recognized. There is one other major ommission that needs to be corrected. Biogas engines are powered by air pollutants. That is they consume not only methane but also H2S (a PM/SO2 precursor and occupational hazard), VOCs and even some ammonia. The amount of H2S consumed is in the hundreds of tons a year. And the amount of VOCs consumed is nearly equivalent to the amount of NOx produced. Your analysis doesn't recognize those public health and environmental benefits. It needs to.
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Date and Time Comment Was Submitted: 2008-10-10 12:24:34
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