Emission Characteristics and Formation Mechanism of Carbonyl Compounds from Residential Solid Fuel Combustion Based on Real-World Measurements and Tube-Furnace Experiments.

This study updated carbonyl compound (CC) emission factors (EFs) and composition for residential solid fuel combustion based on real-world measurements of 124 fuel/stove combinations in China and explored the CC formation mechanism using tube-furnace experiments with 19 fuels and low/high temperatures to explain the impact of fuel and stove on CC emission characteristics. The average EF CC values for straw, wood, and coal were 1.94 ± 1.57, 1.50 ± 0.88, and 0.40 ± 0.54 g/kg, respectively. Formaldehyde and acetaldehyde were the most abundant species, accounting for 40-60% of CCs, followed by acetone (∼20%), aromatic aldehydes (∼10%), and unsaturated aldehydes (∼5%). Different from formaldehyde and acetaldehyde, other species showed significant variation among fuel types. All these characteristics could be explained by the difference in the volatile content and chemical structure of fuel, such as aromatic in coal versus lignin in biomass. The improvement in stove technology reduced CC emissions by 30.4-69.7% (mainly formaldehyde and acetaldehyde) among fuels but increased the proportion of aromatic aldehydes by 24.3-89.4%. Various CC species showed different formation mechanisms related to fuel property and burning temperature. The volatile matter derived from thermal pyrolysis of fuel polymers determined CC composition, while higher temperature preferentially degraded formaldehyde and acetaldehyde but promoted the formation of acetone and aromatic aldehydes. This study not only revealed emission characteristic of CCs from RSFC but also contributed to the improvement of clean combustion technology.