Residential wood combustion experiments were conducted in a simulated rural kitchen, which was built to replicate the layout of kitchens found in rural Northern China. The experimental site is located in a remote area outside of Beijing with no residential or traffic sources nearby. One commonly used brick cooking stove was used in this study. This type of stove is currently used by about 175 million residences in rural areas, following a campaign to disseminate fuel-saving stoves (National Improved Stove Program) during the 1980~1990s in rural China. Detailed information about the kitchen and the stove was published in a previous study 15 (link). For residential cooking and heating, residents usually burn a mixture of various wood fuels that are available for them, so it is difficult to accurately estimate the consumption of each type of woods burned in the household. This study investigated 17 types of wood, which represent the main tree species used for bio-energy in China 30 . These include Chinese white poplar (Populus tomentosa Carr.), water Chinese fir (Metasequoia glyptostroboides), Chinese pine (Pinus tabulaeformis Carr.), cypress (Cupressus funebris Endl.), elm (Ulmus pumila L.), fir (Cunninghamia lanceolata), larch (Larix gmelini (Rupr.) Rupr.), maple (Acer mono Maxim.), oak (Quercus mongolica), paulowonia tomentosa (P.tomentosa (Thunb.) Steud.), toon (Ailanthus altissima), white birch (Betula platyphylla Suk), willow (Salix babylonica), locust (Robinia pseudoacacia L.), bamboo (Phyllostachys heterocycla(Carr.)), lespedeza(Leapedeza bicolor. Turcz), holly (Buxus megistophylla Lévl) and buxus sinica shrub (Buxus sinica (Rehd. et Wils.) Cheng). The properties of these fuels, including density, moisture, elemental contents (C, H, N, O), proximate analysis results (volatile matter, fixed carbon, and ash content), and high heating values, were measured and provided in the Table 1 and Table 2 .
The combustion experiments were conducted by heating known amounts of water, similar to what has been done in indoor crop residue burning experiments 15 (link). Pre-weighed (~1.0 kg) quantities of wood fuels were cut into small pieces (about 15~20 cm2 × 20~30 cm in length), ignited at the split wood tips and inserted into the stove chamber, to mimic the pattern of residential wood combustion in rural residents’ daily lives. The shrubby biomass was broke into 20~30 cm sections. The associated flue gas entered a mixing chamber (about 4.5 m3) with a built-in fan. There was no further dilution conducted to avoid the alterations in PM mass loading and size distribution 13 (link). Measured smoke temperature and relative humidity were 20–35 °C and 40–60% (TM184, Tenmars), respectively. The sampling period covered the whole burning cycle, including the flaming (obvious fire) and smoldering phases (without obvious fire). The sampling started after the initial ignition and stopped when the measured CO and CO2 concentrations dropped to the background levels. The combustion processes lasted for about 40~60 minutes, and ash in the stove was collected and weighed after combustion. It is recognized that combustion conditions and emissions varied in various burning phases and future study using continuous on-line measurements is suggested. This combustion experiment was repeated three times for each type of fuel.
The combustion experiments were conducted by heating known amounts of water, similar to what has been done in indoor crop residue burning experiments 15 (link). Pre-weighed (~1.0 kg) quantities of wood fuels were cut into small pieces (about 15~20 cm2 × 20~30 cm in length), ignited at the split wood tips and inserted into the stove chamber, to mimic the pattern of residential wood combustion in rural residents’ daily lives. The shrubby biomass was broke into 20~30 cm sections. The associated flue gas entered a mixing chamber (about 4.5 m3) with a built-in fan. There was no further dilution conducted to avoid the alterations in PM mass loading and size distribution 13 (link). Measured smoke temperature and relative humidity were 20–35 °C and 40–60% (TM184, Tenmars), respectively. The sampling period covered the whole burning cycle, including the flaming (obvious fire) and smoldering phases (without obvious fire). The sampling started after the initial ignition and stopped when the measured CO and CO2 concentrations dropped to the background levels. The combustion processes lasted for about 40~60 minutes, and ash in the stove was collected and weighed after combustion. It is recognized that combustion conditions and emissions varied in various burning phases and future study using continuous on-line measurements is suggested. This combustion experiment was repeated three times for each type of fuel.
