Black carbon emissions from biomass and fossil fuels in rural India

Atmos. Chem. Phys., 11, 7289–7299, 2011 www.atmos-chem-phys.net/11/7289/2011/ doi:10.5194/acp-11-7289-2011 © Author(s) 2011. CC Attribution 3.0 License. Atmospheric Chemistry and Physics Black carbon emissions from biomass and fossil fuels in rural India I. H. Rehman1 , T. Ahmed2 , P. S. Praveen2 , A. Kar1 , and V. Ramanathan2 1 The Energy and Resources Institute, Darbari Seth Block, IHC Complex, Lodhi Road, New Delhi, 110003, India 2 Center for Clouds, Chemistry and Climate, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093-0221, USA Received: 2 March 2011 – Published in Atmos. Chem. Phys. Discuss.: 7 April 2011 Revised: 5 July 2011 – Accepted: 10 July 2011 – Published: 25 July 2011 Abstract. Black carbon (BC) emission from biofuel cooking in South Asia and its radiative forcing is a significant source of uncertainty for health and climate impact studies. Quantification of BC emissions in the published literature is either based on laboratory or remote field observations far away from the source. For the first time under Project Surya, we use field measurements taken simultaneously inside rural households, ambient air and vehicular emissions from highways in a rural area in the Indo-Gangetic-Plains region of India to establish the role of both solid biomass based cooking in traditional stoves and diesel vehicles in contributing to high BC and organic carbon (OC), and solar absorption. The major finding of this study is that BC concentrations during cooking hours, both indoors and outdoors, have anomalously large twice-daily peak concentrations reaching 60 µg m−3 (median 15-min average value) for indoor and 30 µg m−3 (median 15-min average value) for outdoor during the early morning (05:00 to 08:00) and early evening (17:00 to 19:00) hours coinciding with the morning and evening cooking hours. The BC during the non-cooking hours were also large, in the range of 2 to 30 µg m−3 . The peak indoor BC concentrations reached as high as 1000 µg m−3 . The large diurnal peaks seen in this study lead to the conclusion that satellite based aerosol studies that rely on once- daily daytime measurements may severely underestimate the BC loading of the atmosphere. The concentration of OC was a factor of 5 larger than BC and furthermore optical data show that absorbing brown carbon was a major component of the OC. The imprint of the cooking hour peaks were seen in the outdoor BC both in the village as well as in the highway. The results have significant implications for climate and epidemiological studies. Correspondence to: V. Ramanathan () 1 Introduction BC, a fine particulate matter, is a result of incomplete combustion of fossil fuels and biomass fuels. BC though short lived is also the strongest absorber of solar radiation in the atmosphere. It contributes significantly to global warming after long-lived greenhouse gases (Forster et al., 2007; Ramanathan and Carmichael, 2008; Jacobson, 2010). In addition, in South and East Asia, BC is estimated to contribute to the disruption of the monsoon in South Asia (Ramanathan et al., 2001, 2005; Lau et al., 2008) as well as East Asia (Menon et al., 2002) and heating of the elevated regions of the Himalayan-Tibetan region (Ramanathan et al., 2007; Flanner et al., 2009; Menon et al., 2010) thus potentially having a large impact on the food and water security of the region (see Lawrence and Lelieveld, 2010 for a detailed review). Due to its short life with a residential time of a maximum of two weeks as against CO2 that can stay in the atmosphere for centuries, reduction in BC emissions has been increasingly proposed as one of the mitigation measures for limiting climate warming (Ramanathan and Carmichael, 2008; Grieshop et al., 2009; Kopp and Mauzerall, 2010). About 3 billion human beings in developing countries, who subsist on a daily income of less than $2 a day (IEA, 2007) rely on solid biomass fuels for cooking and space heating, contributing to about 25 % of the global emissions of BC and about 50 % of the anthropogenic emissions of BC (Bond et al., 2007). In South Asia, BC emission from residential biofuels (wood, crop residue, dung) cooking is the largest source of atmospheric BC concentrations (Venkataraman et al., 2005). In India alone about 80 % of 160 million rural and 58 million urban households use solid biofuels (Venkataraman et al., 2010). Several studies have demonstrated the adverse impact on health from inhalation of fine particulate emissions containing BC from fossil and solid biomass fuels Published by Copernicus Publications on behalf of the European Geosciences Union. 7290 I. H. Rehman et al.: Black carbon emissions from biomass and fossil fuels in rural India (Pope et al., 1995; Ezzati and Kamen, 2002; Sauvain et al., 2003; Forastiere, 2004; Penn et al., 2005; Rom and Samet, 2006; Schwarze et al., 2006; Dockery and Stone, 2007). It is estimated that globally inhalation of smoke from indoor cooking using biomass fuels leads to 1.6 million deaths annually (WHO, 2002). In addition, the high levels of BC emissions from biomass fuels (Gustafsson et al., 2009; Venkataraman et al., 2005; Bond et al., 2007) can also significantly impact climate forcing from local to global scales (Forster et al., 2007; Ramanathan and Carmichael, 2008). Indo-Gangetic Plains (IGP) region in South Asia is one of the most densely populated regions in the world and also a major source of BC emissions from cooking with biomass fuels. Large uncertainties exist in BC emission data from this region, which in turn induce large errors in estimating its radiative forcing. To reduce these uncertainties, as well as to document the role of biomass BC on health, regional climate change and Himalayan retreat, field data sets are needed. These data sets will improve the urgently needed 1 2 and ground measurements of BC for validation of climate epidemiological models and will also help to guide the regulatory bodies to outline BC mitigation policies. Action taken to reduce or mitigate BC emissions from biomass fuels can save millions of lives, especially among women and children, and presents an opportunity to reduce warming on short-time scale (Grieshop et al., 2009). Thus, BC connects poverty and health with rural development and climate mitigation. Towards this goal, Project Surya was conceived as an international research effort and is being implemented in the IGP region in northern India (Ramanathan and Balakrishnan, 2007; Ramanathan et al., 2010). 3 Project Surya is a scientific intervention field experiment. 4 Unlike earlier studies which reported BC concentrations in Fig. 1. (above) MODIS TERRA monthly mean aerosol optical emission plume close to wood-burning cook stoves (e.g., 5 RoFigure 1 depth (AOD) over India for November 2009. Also shown is our den at al., 2006, 2009) or BC concentration from wood in sampling site Surya village (SVI 1) located in the IGP region alo (...truncated)