Hydropower as a Hidden Source of Greenhouse Gases

Abstract

Hydropower is widely considered one of the cleanest forms of renewable energy, but recent research highlights its contribution to greenhouse gas (GHG) emissions, challenging this perception. This study quantifies the indirect emissions of carbon dioxide (CO2) and methane (CH4) linked to hydropower facilities, focusing on emissions from the anaerobic decomposition of organic matter in reservoirs. The findings reveal that hydropower reservoirs emit approximately 1 billion tonnes of GHGs annually, which accounts for 1.3% of global anthropogenic emissions. Notably, methane, a greenhouse gas with a global warming potential 28 times greater than CO2 over a 100-year period, represents a substantial part of these emissions. Around 22 million tonnes of CH4 are released annually from reservoirs due to the decay of submerged vegetation and organic material from inflowing rivers. To assess these emissions, methodologies such as floating chamber measurements and remote sensing techniques were employed, providing accurate, site-specific emission data across various geographic regions. The study also explores mitigation strategies, including optimizing reservoir design and enhancing water management practices to reduce methane production. These results highlight the need to address the environmental impacts of hydropower and suggest that, without such interventions, hydropower’s role in climate change mitigation could be undermined by its contribution to GHG emissions. Therefore, achieving true sustainability in hydropower development requires integrating these findings into policy and design frameworks.