1189847 - Study of Residential Wood Burning for Minnesota

Through ongoing residential wood use surveys in Minnesota, we know that citizens across Minnesota enjoy backyard or recreational fires. Statewide, the greatest volume of wood burned is for primary heat, but burning for pleasure is the most common reason a household burned wood. Preliminary results from Minnesota’s 2020 residential wood survey conducted during the COVID-19 stay-at-home emergency order show that wood use increased by 6%from the previous 2017/2018 survey. These trends indicate that wood burning continues to be an important major contributor to Minnesota’s PM2.5 emission inventory, and potentially that backyard fires were an important recreational activity during this time.
Emissions testing was to quantify fine particulate matter (PM) emissions from two commercially available outdoor firepits designed to burn wood logs with minimal smoke production (low smoke) and from a traditional outdoor firepit. PM emission rates for each firepit were based on emissions measured during burn-cycles designed to represent typical recreational use. Three rounds of testing burned firewood of different moisture content (MC) levels: low (MC < 10%), moderate (10%  MC < 20%), and high (MC ≥ 21%). Results showed higher PM emission factors were associated with higher MC. It suggested burning dry wood to lower ambient PM2.5 emissions, particularly in urban areas.
However, the studied traditional outdoor firepit does not represent the backyard or recreational fires in the real world. Further study is needed. This paper discusses residential wood burning behavior and trends in Minnesota.