Toward the ultra-clean and highly efficient biomass-fired heaters. A review

In the last two decades the use of biomass as a carbon-neutral source of energy has almost doubled. The main challenge of using biomass heaters is the impact of particulate matter and gaseous emissions on the environment and human health. This study critically analyzes solid biomass heaters' emissions and thermal efficiency. The classification of wood-fired heaters based on different parameters and analysis of the effect of combustion conditions, fuels and stove types, and biomass characteristics on emissions have been critically analyzed. Results show that biomass type and size, user behavior, tar fouling, inlet air characteristics, and appliance structure are some of the most critical parameters which impacts biomass-fired heaters' efficiency. New techniques have been utilized to improve emissions and efficiency. It was observed that wood type and size can decrease emissions up to 24 times in some cases. The NOx and PM emissions in automatic pellet heater decreased up to 2 and 4.5 times respectively as compared to manual wood heater. Research also showed that utilizing automatic wood stove improves efficiency by 20%. Use of additive materials can reduce the CO and PM emissions up-to 60%. Several investigations have shown that fuel type can also improve efficiency up to 10%.