How dirty is clean hydro power?

I have a problem with the term clean energy: most energy as we know it isn't clean. I am a proponent of alternative energy sources such as wind and solar because I think they are considerably cleaner than fossil fuels. But true clean energy basically boils down to very few things, such as using sunlight to dry your clothes. Hydro power, for example, is often thought of as clean energy, when it might make more sense to think of it is “cleaner” energy.

The obvious advantages of dams are that their fuel is free, they do not involve burning any oil, and with the help of reservoirs they can provide energy at just about any moment.

The downsides are also pretty evident. Dams displace people, damage ecosystems by diverting river runs and often take water away from folks that need it like farmers and fishermen. The problems hydro power has caused in the American west are well chronicled in the phenomenal book Cadillac Desert, while the modern-day debates over projects like the massive Belo Monte dam on the Xingu river are a testament to how disruptive such operations can be. These are the trade-offs for energy that’s cleaner than dirty coal.

But what if it’s not?

A group of researchers insist that hydropower projects like the ones being built in the Amazon may release more greenhouse gasses that coal-fired power plants. Philip Fearnside, a conservation biologist works for the INPA research center in Manaus, has been on this crusade for the better part of two decades.

The problem lies in part with the creation of reservoirs – which have huge benefits, particularly when it comes to wind power, because they function almost as if they were batteries that can store power. But they also flood a broad vegetated area. As the vegetation rots underwater, it creates methane gas – which has a greenhouse effect 21 times that of carbon dioxide. Pushing the water through turbines releases that methane.

Fearnside also points out in this article, reservoirs are like bathtubs that are drained and then filled up again. This often means vegetation grows on the land exposed when water is drained, and then the same vegetation is again flooded once the reservoir is refilled, creating a “methane factory” that considerably changes the “low-emissions” logic of hydro-power.

Fearnside in 2002 found that the Tucurui dam (which I mentioned here) released more greenhouse gasses than the city of Sao Paulo, while the Balbina dam released more carbon dioxide equivalent than would be released by a fossil-fuel based plant generating the same amount of energy.

The issue is of course hotly contested, most notably by Brazilian state-run electrical utility Eletrobras, which through a byzantine structure of subsidiaries runs most of Brazil’s hydroelectric projects. Luis Pinguelli Rosa, a former Eletrobras executive, along with other scientists, say Fearnside has exaggerated the extent of the issue by focusing on specific reservoirs with the highest levels of emissions. They say most reservoirs receive more carbon over time than they actually release, making them carbon sinks – rather than carbon emitters – at least in the short run.

The debate is a very technical one and, from what I can gather online, a personal and acerbic one, at least in the exchanges between Pinguelli and Fearnside.

In the end it’s easy to criticize any form of energy generation. Solar panels require toxic chemicals and heavy metals to create. Concentrating solar power requires transmission lines be built, often in disruption of local habitats (read this phenomenal chronicle about environmentalists in California battling solar projects). Wind turbines create a hum that rattles people living nearby while cast constant moving shadows that drive neighbors nuts. Nuclear power’s downsides are pretty obvious after the Fukushima accident.

This should remind us: the cleanest, cheapest and most efficient way to have more energy is to use less. The famous “negawatts.” Reducing fossil fuel use almost always rests on new technology and new forms of energy generation rather than the obvious possibilities for increasing efficiency and cutting consumption. Yes, this pisses people off because it forces them to change their behavior and often pay more for the energy that they use. But it really is the most accessible form of cheap energy.

There’s just no free lunch. We’ve always known that promoting hydropower as an alternative to fossil fuels requires pushing people and towns out of the way to build dams, hardly a “clean” process. Greenhouse gasses and climate change may be among other reasons to hydro power is not as clean as we’d like to think.