Potential Effect of Hydropower Dam on Global Warming – A Field Study of Biomethane Formation at Aono Dam

The energy and power sectors are among the main contributors to greenhouse gas emissions (GHG) and are responsible for global warming. Anthropogenic emissions of carbon dioxide (CO2), the most important GHG, result primarily from the combustion of fossil fuels. A major portion is associated with energy consumption that is at the center of the climate change debate. Renewable energy technology (e.g. wind, solar) has been used and incorporated into the energy sector since the Clean Development Mechanism (CDM) was introduced. Hydroelectricity has an important place in generation of electricity aided by the mechanism mentioned above. The contribution of hydropower to avoid or mitigate GHG is uncertain because there is a possibility that hydroelectric dams may produce and discharge biomass-based methane (CH4), and it is known that methane is about 25 times stronger than carbon dioxide (CO2) in the greenhouse effect. As a certain amount of organic matter is accumulated in hydropower dams, biomethane and CO2 are generated from the anaerobic decomposition of the accumulated organic matter. Therefore, it seems a worthwhile subject for assessing whether hydropower really and effectively contributes to reducing GHG. A field survey was carried out in the middle of Japan’s main island (so-called Kansai area) by chromatography analysis during five months, and the obtained data show a seasonal variation of dissolved CH4 ranging from 20 ppm to 10 ppm.