A critical review of emission standards and regulations regarding biomass combustion in small scale units (<3 MW)

Wood and agricultural crop residues are abundant, renewable and relatively low cost biomasses. Their combustion can replace fossil fuels in several applications. A major concern with biomass combustion is the emission of particulate matter (PM) in the atmosphere. The World Health Organization (WHO) has developed ambient air quality guidelines, notably maximum average annual levels of 20 μg/m3 for PM10 (particulate matter < 10 μm). Combustion standards generally assess total PM at the chimney stack, with variable levels depending on local legislation, industrial activity, population density, etc. (e.g. 100–200 mg/m3 in Massachusetts, 150 mg/m3 in Québec, and 600 mg/m3 in New York). Some areas mandate relatively low PM levels from boilers (50 mg/m3 in Europe, 20 mg/m3 in Germany starting in 2015). The availability of conditioned and relatively dry biomass, along with PM removal technologies (e.g. cyclones, scrubbers, precipitators, and baghouse filters), will become important requirements for future biomass combustion.