Long considered a “clean” energy source, hydropower can actually be bad for the climate

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A new EDF study published this week in Environmental sciences and technologies shows that hydropower – the main renewable energy technology that is expected to grow rapidly – is not always as good for the climate as is commonly believed. Moreover, continue to assume that he is could mean that projects aimed at reducing greenhouse gas emissions will unintentionally increase them instead.

Motivated by pervasive misconceptions about the climate impacts of hydropower, we assessed the warming impacts over time of sustained greenhouse gas emissions estimated from nearly 1,500 existing hydropower plants around the world. . We also looked at the implications of the future development of hydropower.

If minimizing climate impacts is not a priority in the design, construction and geographic location of new hydroelectric facilities, we could end up producing electricity that produces more warming, especially in the short term, than fossil fuels.

How hydropower can be worse for the climate than fossil fuels

Hydropower is produced when water stored behind a dam is released, using the power of gravity to spin turbines that generate electricity. There is no burning of fossil fuels or chimneys involved. This is why, on average, electricity from a hydroelectric facility has a lower carbon footprint per unit of energy than electricity produced from fossil fuels.

Long considered a “clean” energy source, hydropower can actually be bad for the climate Click to Tweet

But the reservoirs where water is stored also produce both carbon dioxide and methane (an even more potent greenhouse gas, with more than 80 times the warming power of CO2 for the first 20 years after its release. release). Carbon dioxide and methane are released when vegetation decomposes underwater. And here there are huge differences from facility to facility due to a range of varying tank characteristics and weather characteristics.

Some hydroelectric reservoirs are actually carbon sinks, absorbing more carbon through photosynthesis from living organisms in the water than they emit by decomposition, while others have a carbon footprint equal to or greater than that of fossil fuels. In fact, of the nearly 1,500 plants around the world that we examined, which account for half of the world’s hydropower production, more than 100 facilities have greenhouse gas emissions that cause more warming than fossil fuels. .

In addition, some regions, such as Africa and India, have proportionately more power plants with high greenhouse gas emissions from hydropower compared to the rest of the world. Unfortunately, these are also hot spots for future hydropower growth. For example, electricity generation from hydropower in India is expected to increase by 230% between 2015 and 2040.

Deadlines matter

It is also important to note that if we build new hydropower facilities with the expectation of climate benefits, those benefits will be considerably smaller in the short term than in the long term. This is due to the powerful short-term impacts of methane emissions, as well as the large amount of carbon dioxide released from the newly flooded reservoirs.

For example, after 50 years of operation, a hydroelectric plant could cause less than 40% of the warming that would be caused by a coal-fired plant. But in the first decade after the hydropower plant was built, it could cause more warming than a coal-fired power plant. Our study reveals that over 200 existing hydropower plants around the world potentially cause more short-term warming than fossil fuel power plants.

Why this is important and what to do

Despite the rapid growth of wind and solar power, hydropower accounts for two-thirds of the world’s renewable energy production. Thousands of new hydroelectric facilities are planned or under construction around the world. The International Energy Agency predicts hydropower could grow nearly 80% by 2040 as the company strives to replace fossil fuels.

Our research shows why it is important to ensure that future hydropower projects do not harm, but help, the climate. For example, if new hydropower plants in India have greenhouse gas emission properties similar to existing Indian hydropower plants, they could be worse for the climate than emissions from average natural gas fired power plants over the years. First 50 years of operation, due to methane emissions as well as carbon dioxide emissions from the creation of the reservoir.

There are things that can be done when planning a new hydroelectric project that can help reduce emissions.
For example, if a facility draws from a large reservoir, but generates a relatively small amount of electricity, it is likely to produce disproportionate greenhouse gas emissions. Keeping this ratio in mind is a valuable part of the planning process, as this “power density” has proven to be the best indicator of overall greenhouse gas emissions from hydropower installations.

Reservoir water temperature may also play a role in producing methane emissions, and therefore avoiding development in extremely hot locations could also reduce emissions.

Overall, we need to dispel the myth that hydropower is universally low carbon and be aware of the potential for high emissions when developing new facilities. This document gives us a more efficient way to evaluate these projects so that we can ensure that new developments offer climatic advantages, not disadvantages.

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