Emissions from Residential Wood Combustion: Effect of Moisture on Emissions

Emissions from Residential Wood Combustion: Effect of Moisture on Emissions (1.3 MB pdf)
Fernando Preto, Canmet Energy Technology Center (Canada), Paris, October 21, 2005

In a presentation to the IEA (International Energy Agency) Task 32 Workshop, Recent Developments in Small Scale Combustion Devices, Fernando Preto of Canmet showed the effect of moisture on emissions.

Fuels were tested at Low Moisture (15% MC) and High Moisture (30%) for carbon monoxide (CO), particulate matter (PM) and Volatile Organic Compounds (VOC).

Low Moisture (15%) produced high CO, low PM and low VOC.

High Moisture (30% MC) produced low CO, high PM and high VOC.

The purpose was to "Study hazardous emissions from residential wood combustion devices in order to provide information for reducing the amount of particulates, VOCs and dioxins and furans and update database of the current contribution of residential appliances to Canadian air sheds."

Environment Canada has initiated the process necessary for adoption of a national regulation for emissions. British Columbia has adopted US standards.

The presentation cites Canadian and US standards including:
CSA B415.1 (Cdn), EPA Part 40 (US): Test methods for determination of efficiency and particulate emissions from wood fired appliances, including conventional pellet stoves, inserts, central furnaces and boilers, small commercial systems, and "high performance" fireplaces. Maximum particulate emission levels are specified. An ASTM document is also being developed to provide testing requirements for outdoor boilers (WK 5982).

The study found cordwood stove VOC emissions ranging from 38 mg/kg for certified, hardwood, low moisture, high burn rate to 13 097 mg/kg fuel for "old" stove, softwood, high moisture, low burn rate.

Total particulate emissions ranged from 0.019 g/MJ for the pellet stove operated at a high burn rate to 3.68 g/MJ for the "old" conventional stove operated at a low burn rate. Average emissions are 1.68 g/MJ for the conventional cordwood stove and 0.44 g/MJ for certified non-catalytic stoves.

Data show the clear reduction of 3:1 for PM through design.

It concludes:

- Advanced technology devices, such as pellet and certified cordwood stoves, produce substantially less hazardous emissions than conventional cordwood stoves.

- In general lower fuel moisture and high burn rates result in lower emissions but there is no consistent effect on all hazardous emissions.

See:
Canmet Residential/Commercial Combustion, Nepean, Ontario, Canada

IEA Bioenergy Task 32 Biomass Combustion and Cofiring