Emissions of carbon monoxide and carbon dioxide from uncompressed and pelletized biomass fuel burning in typical household stoves in China Wen Wei a , Wei Zhang b, * , Dan Hu a , Langbo Ou a , Yindong Tong a , Guofeng Shen a , Huizhong Shen a , Xuejun Wang a, ** a Ministry of Education Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China b Center for Resource and Environmental Management, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China article info Article history: Received 1 November 2011 Received in revised form 16 March 2012 Accepted 19 March 2012 Keywords: Emissions factors Pellet biomass fuels Biomass burning Carbon monoxide Carbon dioxide abstract Carbon dioxide (CO 2 ) and carbon monoxide (CO) impact climate change and human health. The uncertainties in emissions inventories of CO 2 and CO are primarily due to the large variation in measured emissions factors (EFs), especially to the lack of EFs from developing countries. China’s goals of reducing CO 2 emissions require a maximum utilization of biomass fuels. Pelletized biomass fuels are well suited for the residential biomass market, providing possibilities of more automated and optimized systems with higher modified combustion efficiency (MCE) and less products from incomplete combustion. However, EFs of CO 2 and CO from pellet biomass fuels are seldom reported, and a comparison to conventional uncompressed biomass fuels has never been conducted. Therefore, the objectives of this study were to experimentally determine the CO 2 and CO EFs from uncompressed biomass (i.e., firewood and crop residues) and biomass pellets (i.e., pine wood pellet and corn straw pellet) under real resi- dential applications and to compare the influences of fuel properties and combustion conditions on CO 2 and CO emissions from the two types of biomass fuels. For the uncompressed biomass examples, the CO 2 and CO EFs were 1649.4 Æ 35.2 g kg À1 and 47.8 Æ 8.9 g kg À1 , respectively, for firewood and 1503.2 Æ 148.5 g kg À1 and 52.0 Æ 14.2 g kg À1 , respectively, for crop residues. For the pellet biomass fuel examples, the CO 2 and CO EFs were 1708.0 Æ 3.8 g kg À1 and 4.4 Æ 2.4 g kg À1 , respectively, for pellet pine and 1552.1 Æ 16.3 g kg À1 and 17.9 Æ 10.2 g kg À1 , respectively, for pellet corn. In rural China areas during 2007, firewood and crop residue burning produced 721.7 and 23.4 million tons of CO 2 and CO, respectively. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The increase in CO 2 emissions is a major factor of global warming (IPCC, 2007; Florides and Christodoulides, 2009). China is a major energy consumer, and the amount of CO 2 released into its atmosphere in 2008 was 7.03 billion tons (Worldbank, 2011), ranking first in the world. China’s goals of contemporaneously reducing greenhouse gas emissions require a maximum utilization of clean energy to replace the traditional fossil fuels. Biofuels, a sustainable alternative to fossil fuels and a CO 2 -neutral energy source, are expected to be a major contributor to these goals. Novel and upgraded biomass fuels, such as pellets and briquettes, have become more common and provide several advantages to accom- plish efficient and environmentally acceptable combustion condi- tions (Boman et al., 2006). China is a large agricultural country and is rich in biomass resources. On average, the annual production of crop residues was approximately 700 million tons (Yuan et al., 2010). Biomass accounts for 23.5% of China’s final energy consumption, especially in the rural areas (Hu, 2008). Statistics have shown that in 2007, the total energy consumption per capita in rural areas was 960 kg equivalents of coal, among which 539 kg equivalents of coal was for living. The proportion of crop residues and firewood for the living energy consumption was 32.8% and 21.2%, respectively (Hu, 2008). However, biomass fuel burning produces air pollution in the form of CO, black carbon and particulate matter, causing harm to human health (Chen et al., 2009). Pellet biomass fuels are compressed, homogenized and dried biomass fuels that possess several advantages during handling, storage and combustion when compared to unprocessed biomass * Corresponding author. Tel./fax: þ86 10 62756122. ** Corresponding author. Tel./fax: þ86 10 62759190. E-mail addresses: wzhang@pku.edu.cn (W. Zhang), xjwang@urban.pku.edu.cn (X. Wang). Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2012.03.060 Atmospheric Environment 56 (2012) 136e142