Comparison of Carbon Monoxide and Particulate Matter Emissions from Residential Burnings of Pelletized Biofuels and Traditional Solid Fuels Guofeng Shen* ,†,‡ and Miao Xue † † Jiangsu Provincial Key Laboratory of Environmental Engineering, Jiangsu Academy of Environmental Sciences, Nanjing 210036, People’s Republic of China ‡ College of Urban and Environmental Sciences, Peking University, Beijing 100891, People’s Republic of China * S Supporting Information ABSTRACT: Widespread use of solid fuels affects indoor/outdoor air quality, human health, and climate change significantly. Replacing traditional solid fuels with affordable cleaner fuels is a challenge for most developing countries. In this study, carbon monoxide (CO) and particulate matter (PM) emissions and financial costs of a potential cleaner fuel-pelletized biofuels were compared to those of traditional solid fuels, including coal, crop residue, and wood, and a conventional modern fuel, liquid petroleum gas (LPG), in terms of fuel-mass-based emission factor (EF), delivered-energy-based emission factor (EF E ), and delivered-energy-based cost (C E ). The combustions of pelletized fuels and LPG had not only relatively higher thermal efficiencies but also lower EFs, leading to much lower EF E of these cleaner fuels. The adoption of pelletized fuels burned in a modern pellet burner could reduce pollutant emissions significantly in comparison to traditional solid fuels. When both EF E and C E are taken into consideration, it could be found that the nearly free ordinary biomass fuels and high-cost coals had much higher pollutant emissions, while LPG was the most expensive, although it would produce the lowest emission. Pelletized fuels appear to be a good alternative in rural households because of not only lower pollutant emissions but also relatively low cost. Future studies, including but not limited to emission measurements, potential reductions in air concentrations and health outcome, systematic cost-benefit analysis, and identification of key enablers and barriers affecting the large-scale uptake, are strongly recommended. ■ INTRODUCTION In most households in developing countries and areas, solid fuels, such as coal, crop residues, and woody materials, are the predominant energy sources. It had been reported that, globally, although the proportion of households using solid fuels for cooking decreased continuously from 62% in 1980 to 41% in 2010, the absolute number of people relying on solid fuels for cooking has remained stable at about 2.8 billion because of population growth. 1 When the population using solid fuels in household heating is taken into consideration, the population exposed to smoke from household solid fuel combustion would be larger. Residential combustions of these solid fuels are usually low-efficient, emit a variety of incomplete combustion pollutants, such as carbon monoxide (CO), particulate matter (PM), and various gaseous and particle- bound toxic organics, 2-4 and subsequently, affect human health and local/regional climate change significantly. 5-7 The latest report on the Global Burden of Disease estimated that the exposure to household air pollution from inefficient solid fuel combustion was associated with about 3.5 million premature deaths in 2010, which was even higher than those of 3.2 and 0.15 million deaths caused by ambient PM and ozone pollution, respectively. 8 In China, similar to other developing counties, coal and biomass fuels are the dominant sources for primary household energy, particularly in rural families. Approximately 46% of the Chinese households relied on solid fuels for daily cooking. 1 In rural households, solid fuels comprised up to 90% of the energy consumed (79.5% biofuels and 12.8% coal), while the contribution of liquid petroleum gas (LPG) was about 1.4%. 9 Extensive use of solid fuels under relatively low-efficient burning conditions produces high amounts of incomplete pollutants, causing serious indoor and outdoor air pollution and adverse health outcomes, including lung cancer and respiratory illness in rural China. 10-12 In a field survey on indoor CO and PM pollution based on a random sample of 396 rural households, average kitchen PM 4 (PM with a diameter less than 4.0 μm) concentrations were 164 ± 110, 282 ± 286, and 142 ± 83 μg/m 3 during the summer time when woody material, crop residues, and coal were combusted, respec- tively. 13 In a rural household in northern China, the daily mean PM and PM 2.5 levels were found to be as high as 2400 ± 1200 and 1300 ± 800 μg/m 3 , respectively, when biomass fuels were used for daily cooking and heating in the cold winter. 14 For biomass fuels, in addition to be combusted in the residential sector as the primary household energy, open burning in a field is another commonly found practice in many rural areas, especially after harvest. The field burning is a great waste of resource; moreover, the intense pollution episode formed over a relatively short period during the burning often leads to multiple direct or indirect adverse effects on the air quality (poor visibility and regional haze), the traffic safety (congestion Received: March 21, 2014 Revised: April 30, 2014 Published: May 12, 2014 Article pubs.acs.org/EF © 2014 American Chemical Society 3933 dx.doi.org/10.1021/ef5006379 | Energy Fuels 2014, 28, 3933-3939