VOCs Emissions from Multiple Wood Pellet Types and Concentrations in Indoor Air

Abstract

Wood pellet storage safety is an important aspect for implementing woody biomass as a renewable energy source. When wood pellets are stored indoors in large quantities (tons) in poorly ventilated spaces in buildings, such as in basements, off-gassing of volatile organic compounds (VOCs) can significantly affect indoor air quality. To determine the emission rates and potential impact of VOC emissions, a series of laboratory and field measurements were conducted using softwood, hardwood, and blended wood pellets manufactured in New York. Evacuated canisters were used to collect air samples from the headspace of drums containing pellets and then in basements and pellet storage areas of homes and small businesses. Multiple peaks were identified during GC/MS and GC/FID analysis, and four primary VOCs were characterized and quantified: methanol, pentane, pentanal, and hexanal. Laboratory results show that total VOCs (TVOCs) concentrations for softwood (SW) were statistically (p < 0.02) higher than blended or hardwood (HW) (SW: 412 ± 25; blended: 203 ± 4; HW: 99 ± 8, ppb). The emission rate from HW was the fastest, followed by blended and SW, respectively. Emissions rates were found to range from 10−1 to 10−5 units, depending upon environmental factors. Field measurements resulted in airborne concentrations ranging from 67 ± 8 to 5000 ± 3000 ppb of TVOCs and 12 to 1500 ppb of aldehydes, with higher concentrations found in a basement with a large fabric bag storage unit after fresh pellet delivery and lower concentrations for aged pellets. These results suggest that large fabric bag storage units resulted in a substantial release of VOCs into the building air. Occupants of the buildings tested discussed concerns about odor and sensory irritation when new pellets were delivered. The sensory response was likely due to the aldehydes.

Predictors of blood volatile organic compound levels in Gulf coast residents

“…Off-gassing of home construction materials is a known source of indoor BTEX exposure ( 14 , 60 , 61 ). The observed association between reported home construction in the six months preceding blood collection and increasing blood benzene level is supported by this.…”

Effect of Moisture on Gas Emissions from Stored Woody Biomass

“…Aldehydes are the most abundant NMVOCs from pellet storage, in which hexanal accounts for 80% of emitted aldehydes. Other lab study also showed that the main NMVOCs including methanol, pentane, pentanal and hexanal were generated by the oxidation of stored pellets [38]. Temperature was in accord with the TVOC concentrations from stored WRC chips.…”

“…In confined space, CO concentrations are several orders of magnitude higher than the occupational exposure limits. Serious accidents in Europe have been reported in the past decade, as the CO concentration was found to be high with a range of 14 ppm to 155 ppm (v/v) in the pellet storage bins [38].…”

Comparison of Gaseous Emissions from Stored Biomass Residues

“…It is reported the emission rates and the maximum concentrations of the gases reduce at lower temperatures [13]. Tumuluru et al concluded that the gas emissions from stored wood pellets increased exponentially with storage temperature.…”