Hydropower's Biogenic Carbon Footprint

Global warming is accelerating and the world urgently needs a shift to clean and renewable energy. Hydropower is currently the largest renewable source of electricity, but its contribution to climate change mitigation is not yet fully understood. Hydroelectric reservoirs are a source of biogenic greenhouse gases and in individual cases can reach the same emission rates as thermal power plants. Little is known about the severity of their emissions at the global scale. Here we show that the carbon footprint of hydropower is far higher than previously assumed, with a global average of 173 kg CO2 and 2.95 kg CH4 emitted per MWh of electricity produced. This results in a combined average carbon footprint of 273 kg CO2e/MWh when using the global warming potential over a time horizon of 100 years (GWP100). Nonetheless, this is still below that of fossil energy sources without the use of carbon capture and sequestration technologies. We identified the dams most promising for capturing methane for use as alternative energy source. The spread among the ~1500 hydropower plants analysed in this study is large and highlights the importance of case-by-case examinations.

[1]  B. Wehrli,et al.  Extreme organic carbon burial fuels intense methane bubbling in a temperate reservoir , 2012 .

[2]  E. Duchemin,et al.  Greenhouse gas emissions from reservoirs of the western United States , 2004 .

[3]  L. Hess,et al.  Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2 , 2002, Nature.

[4]  N. Batjes,et al.  The Harmonized World Soil Database , 2009 .

[5]  E. Hertwich,et al.  CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming , 2011 .

[6]  H. Haberl,et al.  Quantifying and mapping the human appropriation of net primary production in earth's terrestrial ecosystems , 2007, Proceedings of the National Academy of Sciences.

[7]  E. Wagenmakers,et al.  AIC model selection using Akaike weights , 2004, Psychonomic bulletin & review.

[8]  Aranya Venkatesh,et al.  Large-scale hydrological modeling for calculating water stress indices: implications of improved spatiotemporal resolution, surface-groundwater differentiation, and uncertainty characterization. , 2015, Environmental science & technology.

[9]  S. Pfister,et al.  Modelling spatially explicit impacts from phosphorus emissions in agriculture , 2015, The International Journal of Life Cycle Assessment.

[10]  J. Edmonds,et al.  Near-term acceleration in the rate of temperature change , 2015 .

[11]  N. Wu,et al.  Methane emissions from newly created marshes in the drawdown area of the Three Gorges Reservoir , 2009 .

[12]  I. Strachan,et al.  The net carbon footprint of a newly created boreal hydroelectric reservoir , 2012 .

[13]  P. Döll,et al.  High‐resolution mapping of the world's reservoirs and dams for sustainable river‐flow management , 2011 .

[14]  J. L. Parra,et al.  Very high resolution interpolated climate surfaces for global land areas , 2005 .

[15]  Serwan M. J. Baban,et al.  Modelling Optimum Sites for Locating Reservoirs in Tropical Environments , 2003 .

[16]  D. M. Rosenberg,et al.  Reservoir Surfaces as Sources of Greenhouse Gases to the Atmosphere: A Global Estimate , 2000 .

[17]  U. S. Geological.  Magnitude and Significance of Carbon Burial in Lakes , Reservoirs , and Peatlands , 2017 .

[18]  Ibrahim Yuksel,et al.  Hydropower for sustainable water and energy development , 2010 .

[19]  S Pacala,et al.  Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies , 2004, Science.

[20]  D. Shindell,et al.  Anthropogenic and Natural Radiative Forcing , 2014 .

[21]  Reinaldo R. Rosa,et al.  Mitigation and recovery of methane emissions from tropical hydroelectric dams , 2007 .

[22]  John M. Melack,et al.  CO2 emissions from a tropical hydroelectric reservoir (Balbina, Brazil) , 2011 .

[23]  P. Fearnside,et al.  Greenhouse-gas emissions from tropical dams , 2012 .

[24]  S. Pfister,et al.  Global water footprint assessment of hydropower , 2016 .

[25]  Thomas Bruckner,et al.  Annex III - Technology-specific cost and performance parameters , 2013 .

[26]  H. Velthuizen,et al.  Harmonized World Soil Database (version 1.2) , 2008 .

[27]  N. Meinshausen,et al.  Greenhouse-gas emission targets for limiting global warming to 2 °C , 2009, Nature.

[28]  Marco Aurélio dos Santos,et al.  Gross greenhouse gas fluxes from hydro-power reservoir compared to thermo-power plants , 2006 .

[29]  Jerald B. Johnson,et al.  Model selection in ecology and evolution. , 2004, Trends in ecology & evolution.

[30]  A. Wüest,et al.  Spatial heterogeneity of methane ebullition in a large tropical reservoir. , 2011, Environmental science & technology.

[31]  Roberto Turconi,et al.  Life cycle assessment (LCA) of electricity generation technologies: Overview, comparability and limitations , 2013 .

[32]  Oliver Paish,et al.  Small hydro power: technology and current status , 2002 .

[33]  Jonathan J. Cole,et al.  Hydroelectric carbon sequestration , 2012 .

[34]  Martin Wessels,et al.  Organic carbon burial efficiency in lake sediments controlled by oxygen exposure time and sediment source , 2009 .

[35]  E. Hertwich.  Addressing biogenic greenhouse gas emissions from hydropower in LCA. , 2013, Environmental science & technology.

[36]  F. Roland,et al.  Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude , 2011 .