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The Metric

Jan 14, 2014

Alternatives to biomass burning to address air quality

Biomass Burning in Rural Dali, Yunnan Province, PRC; Image Credit: Angel Hsu

The conversion of biomass into usable energy is as old as the human use of fire. Worldwide, it is still the primary source of household energy for hundreds of millions of families, particularly those in the developing world. However, urban and rural burning of biomass—whether to clear land, dispose of agricultural or municipal waste, or for household use—is among the leading contributors to dangerous air pollution. Clean and equitable ways of converting biomass into energy have begun to demonstrate success at alleviating these harms.

Power plants that burn biomass, particularly wood pellets, are widespread in Europe. With its wealth of forest resources, for instance, Finland produces 20 percent of its total electricity from wood burning, usually in the form of pellets made from the leftovers of milling.1 Fuel in this form can be considered carbon neutral, as replanted trees recapture the carbon released from burning. In some cases, biomass is used as a direct substitute, or cleaner accompaniment, to coal in power plants, a process known as co-firing. Through gasification and anaerobic digestion, biomass is used to produce combustible fuels— most notably methane, which can be used instead of fossil fuels. Because gas production through anaerobic digesters is relatively simple, some countries, including the United Kingdom, have instituted feed-in tariffs for “biogas”, repaying small-scale producers for energy they return to the market.

Examples from Europe and North America have instigated a wave of biomass-based energy schemes in the developing world, most notably in India and China. China’s capacity to convert biomass to energy has grown tremendously in the last decade, and it is slated to provide 4 percent of the country’s primary energy by 2020. That may not sound like a lot, but it represents a fourfold increase since 2010, in a country whose energy sector is booming. Currently, the direct combustion of straw dominates the sector, although gasification and the production of liquid fuels like ethanol are receiving huge boosts from the national government.2

A national effort to scale up biomass to energy solutions has been ongoing in India since the 1970s.  To date biomass and waste-to-energy make up about 12 percent of the country’s entire renewables sector, itself only about five percent of total energy supply. However, the widespread availability of refuse biomass in rural India, the lack of access to clean energy faced by many rural Indians, and the ecological degradation created by demand for wood make the country a perfect laboratory for small-scale biomass to energy generation.3

A number of experimental initiatives trialing household anaerobic digesters, utilizing livestock dung in particular, have shown that distributed, local production of biogas is effective at alleviating the human health and ecological impacts of energy demand4 In the case of the Kolar district of the province Karnataka, more than 10,000 digesters have been installed on the properties of local people. Fed by animal dung and household wastewater, the digesters produce gas for cooking and heating. The leftover slurry can then be used as fertilizer. The projects at Kolar were funded in large part by the UN Framework Convention on Climate Change’s Clean Development Mechanism, which allows developed countries to achieve their emissions reduction commitments by promoting emissions-reducing projects in developing countries like India.

Ericsson, K., Nilsson, L. (2006). Assessment of the potential biomass supply in Europe using a resource-focused approach. Biomass Bioenergy, 30, 1-15.

Zhou, Z., Yan, H. (2012). Assessment of the biomass power generation industry in China. Renewable Energy, 37:1, 53-60.

Rao, P. (2010). Biogas generation potential by anaerobic digestion for sustainable energy development in India. Renewable and Sustainable Energy Reviews, 14:7, 2086-2094.

Aoramoorthy, G., Hsu, M.J. (2008). Biogas Plants Ease Ecological Stress in India’s Remote Villages. Human Ecology, 36(2008), 435-441.