On many of our projects we are faced with a choice between Combined Heat and Power (CHP) and biomass boilers as the best way to achieve reductions in CO2. There is a widely held view that biomass is bad and CHP is good in terms of air quality. Oxides of nitrogen (NOx) and particulate matter are both pollutants of concern. Manufacturer figures for emissions of these pollutants are:
- CHP with catalyst (Ener.G 150kWth): 430 mg/kWh
- Biomass (Hoval STU 150 kW): 17.8 mg/kWh
- CHP: 0 mg/m3
- Biomass with abatement technology (i.e. Hovel CF filter): 5mg/m3
CHP is considerably more expensive than biomass and in terms of NOx emissions CHP is over 20 times more polluting than biomass. Biomass is more polluting in terms of particulate matter, although with appropriate flue design and dispersion this can be brought down to acceptable levels.