Laboratory experiments regarding the use of filtration and retained heat to reduce particulate matter emissions from biomass cooking

There are a number of methods to help reduce the exposure to household air pollution associated with using biomass fuel for daily cooking and heating in nearly 40% of global households. These most commonly include use of cleaner fuels and cookstoves, increasing ventilation, and use of a chimney. This paper investigates two less-commonly considered methods, 1) reducing exposure through filtration and capture of PM2.5 and 2) avoiding emissions using retained heat for cooking. If cookstoves are operated inside an enclosure from which smoke is pulled by a fan through an inexpensive HEPA-type filter before exiting to the outside, the personal exposure levels, room concentrations, and external pollution might be reduced. To test this method, an enclosure was built from which a box fan pulled the air and PM2.5 through a filter, and four different filters were tested. The rate of PM2.5 production (mg/min) exiting the filter was monitored with gravimetric measurement under an emissions hood during the high and low power phases of the Water Boiling Test 4.2.3 conducted on a biomass rocket stove with forced draft. The average of seven baseline emissions tests with no filter was 7.5 mg/min of PM2.5. The average of seven tests using the highest quality furnace filter (3 M 2200) was reduced to 1.5 mg/min and the difference was significant at 95% confidence. The use of retained heat to simmer also reduced emissions of PM2.5 to zero by burning the boil-phase-made-charcoal while 5 l of water were simmered for 35 min.