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Carbonaceous particle matter emitted from a pellet-fired outdoor biomass boiler
Citation:
Hays, M., J. Kinsey, I. George, W. Preston, S. Carl, AND B. Patel. Carbonaceous particle matter emitted from a pellet-fired outdoor biomass boiler. 37th Annual AAAR Conference, Portland, OR, October 14 - 18, 2019.
Impact/Purpose:
Biomass pellets are an intriguing source of renewable energy; although, the air pollution and exposure risks posed by the emissions from burning pellets in outdoor biomass boilers are uncertain. The present study shows evidence that toxic PAH emissions from outdoor biomass boilers burning pellets differ with other forms of residential biomass burning appliances. Past toxicological evidence shows that smoke from residential biomass burning is highly mutagenic. Thus, further toxicological evaluation of biomass pellet burning emissions is required to properly understand the risks posed.
Description:
The present study examines the carbon composition of fine particle matter (PM) emissions from an outdoor biomass boiler (OBB) firing switch grass and hardwood biomass pellets at different test cycles. The organic and elemental carbon (OC and EC) content and select semivolatile organic compounds (SVOCs) in filter-collected PM were identified and quantified using thermal-optical analysis and gas chromatography-mass spectrometry (GC-MS), respectively. Fine PM emissions from the OBB ranged from 0.4 g/kg to 2.91 g/kg of pellets burned of which 40% +/- 17% w/w was carbon. The sum of GC-MS quantified SVOCs in the PM emissions varied from 0.13 g/g OC to 0.41 g/g OC. Relatively high levels of oxygenated compounds were observed in the PM emissions, and the most predominant individual SVOC constituent was levoglucosan (12.5 mg/g OC - 320 mg/g OC). The effect of boiler test cycle on emissions was generally greater than the effect due to pellet fuel type. Organic matter emissions increased at lower loads owing to less than optimal combustion performance. Compared with other types of residential wood combustion, pellet burning in the OBB lowered PM emissions by nearly an order of magnitude. The PM emitted from burning pellets in boilers also contains comparatively less carbon; however, the toxic polycyclic aromatic hydrocarbons (PAH) in the PM from pellet-burning varied substantially, and produced 2-10 times more benzo[k]fluoranthene, dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene.