Effect of Stove Technology and Combustion Conditions on Gas and Particulate Emissions from Residential Biomass Combustion

We have systematically examined the gas and particle phase emissions from seven wood combustion devices. Among total carbon mass emitted (excluding CO2), CO emissions were dominant, together with nonmethane volatile organic compounds (NMVOCs) (10–40%). Automated devices emitted 1–3 orders of magnitude lower CH4 (0.002–0.60 g kg–1 of wood) and NMVOCs (0.01–1 g kg–1 of wood) compared to batch-operated devices (CH4: 0.25–2.80 g kg–1 of wood; NMVOCs: 2.5–19 g kg–1 of wood). 60–90% of the total NMVOCs were emitted in the starting phase of batch-operated devices, except for the first load cycles. Partial-load conditions or deviations from the normal recommended operating conditions, such as use of wet wood/wheat pellets, oxygen rich or deficit conditions, significantly enhanced the emissions. NMVOCs were largely dominated by small carboxylic acids and alcohols, and furans. Despite the large variability in NMVOCs emission strengths, the relative contribution of different classes showed large similarities among different devices and combustion phases. We show that specific improper operating conditions may even for advanced technology not result in the emission reduction of secondary organic aerosol (SOA) forming compounds and thus not reduce the impact of wood combustion on climate and health.本研究系统测定了7台木材燃烧装置的气相与颗粒相排放特征。在排放的总碳质量（不含二氧化碳）中，一氧化碳（carbon monoxide, CO）与非甲烷挥发性有机化合物（nonmethane volatile organic compounds, NMVOCs，占比10%~40%）为主要排放组分。相较于间歇运行装置，自动化装置的甲烷（methane, CH4）与非甲烷挥发性有机化合物排放水平低1~3个数量级：自动化装置的CH4排放为0.002~0.60 g·kg⁻¹木材，NMVOCs排放为0.01~1 g·kg⁻¹木材；而间歇运行装置的CH4排放为0.25~2.80 g·kg⁻¹木材，NMVOCs排放为2.5~19 g·kg⁻¹木材。除首次加载循环外，间歇运行装置的非甲烷挥发性有机化合物总排放量中有60%~90%产生于启动阶段。部分负荷工况或偏离标准推荐运行条件的操作（如使用湿木材/小麦颗粒燃料、富氧或缺氧工况）会显著提升排放水平。非甲烷挥发性有机化合物的主要成分为小分子羧酸、醇类及呋喃类化合物。尽管非甲烷挥发性有机化合物的排放强度存在较大差异，但不同装置及燃烧阶段的各类组分相对占比均表现出高度相似性。本研究表明，即便采用先进技术的装置，若处于特定不当运行工况，也无法降低二次有机气溶胶（secondary organic aerosol, SOA）前体物的排放，因此无法减轻木材燃烧对气候与健康的负面影响。