Comparison of on-site and upstream greenhouse gas emissions from Canadian municipal wastewater treatment facilities

Abstract

Canada's ratification of the Kyoto Protocol has focused attention on the importance of accurately estimating emissions of greenhouse gases (GHG) from all sectors. An inventory of emissions of greenhouse gases from Canadian municipal wastewater treatment plants was prepared using a life-cycle approach. Both on-site emissions at the treatment facility due to the biological processes used and fossil fuels consumed for energy and heat and upstream emissions related to off-site production and transmission of fuels and the off-site production of electricity for the plant were included. For the year 2000, the on-site methane (CH4) emission rate from Canadian municipal wastewater treatment facilities was estimated at 1600 Mg/year. The total on-site emission rate of carbon dioxide (CO2) was estimated at 669 100 Mg/year, but the estimated total CO2 equivalent emissions rose to 1 048 500 Mg/year once upstream emissions were included. Clear abatement strategies related to more efficient energy use and energy recovery can be identified once accurate GHG emissions inventories are in place.Key words: municipal wastewater treatment, life-cycle approach, greenhouse gas emissions, anaerobic processes.