Black carbon cookstove emissions: A field assessment of 19 stove/fuel combinations
Black carbon (BC) emissions from household cookstoves consuming solid fuel produce approximately 25 percent of total anthropogenic BC emissions. The short atmospheric lifetime of BC means that reducing BC emissions would result in a faster climate response than mitigating CO2 and other long-lived greenhouse gases. This study presents the results of optical BC measurements of two new cookstove emissions ﬁeld assessments and 17 archived cookstove datasets. BC was determined from attenuation of 880 nm light, which is strongly absorbed by BC, and linearly related between 1 and 125 attenuation units. A relationship was experimentally determined correlating BC mass deposition on quartz ﬁlters deter-mined via thermal optical analysis (TOA) and on PTFE and quartz ﬁlters using transmissometry, yielding an attenuation cross-section (sATN) for both ﬁlter media types. sATN relates TOA measurements to optical measurements on PTFE and quartz (sATN(PTFE) ¼ 13.7 cm2 mg, R2 ¼ 0.87, sATN(Quartz) ¼ 15.6 cm2 mg, R2 ¼ 0.87). These ﬁlter-speciﬁc sATN, optical measurements of archived ﬁlters were used to determine BC emission factors and the fraction of particulate matter (PM) in the form of black carbon (BC/PM). The 19 stoves measured fell into ﬁve stove classes; simple wood, rocket, advanced biomass, simple charcoal, and advanced charcoal. Advanced biomass stoves include forced- and natural-draft gasiﬁers which use wood or biomass pellets as fuel. Of these classes, the simple wood and rocket stoves demonstrated the highest median BC emission factors, ranging from 0.051 to 0.14 g MJ1. The lowest BC emission factors were seen in charcoal stoves, which corresponds to the generally low PM emission factors observed during charcoal combustion, ranging from 0.0084 to 0.014 g MJ1. The advanced biomass stoves generally showed an improvement in BC emissions factors compared to simple wood and rocket stoves, ranging from 0.0031 to 0.071 g MJ1. BC/PM ratios were highest for the advanced and rocket stoves. Potential relative climate impacts were estimated by converting aerosol emissions to CO2-equivalent, and suggest that some advanced stove/fuel combinations could provide substantial climate beneﬁts.