Why Renewable Energy Is Not as Clean as You Think

Why Renewable Energy Is Not as Clean as You Think

Why you should care

Because we shouldn’t kid ourselves when the future of the planet is at stake. 

OK, so the fight against climate change isn’t going flawlessly. But there is some cause for optimism, right? Money is plowing into cheap solar energy, China is leading the world in green investment and Tesla has released a nice new electric car. Already, over a fifth of the world’s electricity comes from renewables, set to rise to 29 percent by 2040, according to current trends. We’re starting to head in a good direction, one that maybe might hopefully possibly save all the world just in time? RIGHT?!

Well, hate to break it to you, but those stats of rising renewable energy production aren’t all that they seem. In fact:

Solar and wind combined account for barely a fifth of electricity generation defined as renewable. More than 70 percent of it comes from hydropower.

That’s according to International Energy Agency numbers for 2015, the latest figures available. Hydro isn’t the only surprising energy source dominating renewable energy stats: In the U.S., Canada, the EU and China, as well as the global average, more power is generated from biofuels (such as the combustion of wood pellets in power plants or burning off landfill gas) than from solar panels.

So when talking about renewable power, the media might need to change their stock images from turbines and panels to hydroelectric dams and burning logs. So what? Renewable is renewable, right?

These trade-offs may be improvements relative to burning coal, but investment in hydro or biomass might be happening at the expense of solar and wind.

Well, maybe not. Both in the case of hydropower and bioelectricity, the scientific community is far from settled that these power sources are always completely clean. Thanks to the anaerobic decomposition of algae and other plant materials in reservoirs, hydroelectric dams can be major emitters of methane, a greenhouse gas several times more potent than CO2, says Amy Townsend-Small, director of the Environmental Studies Program at McMicken College of Arts and Sciences, who studies methane emissions from lakes. There’s a surprising lack of knowledge about just how much greenhouse gases reservoirs might emit: “We don’t have any long-term monitoring,” Townsend-Small says, and scientists instead rely on global models extrapolated from a small number of reservoirs. Still, hydroelectric dams “are better on a greenhouse-gas level than using fossil fuels,” she says, though environmental campaigner Gary Wockner, who describes hydro as “dirty energy,” asserts that some dams, including the Hoover Dam, emit more greenhouse gases than coal-fired plants.

And in the case of burning biomass, with the huge variability between types of fuels and how they are sourced, it’s impossible to make blanket statements about its efficacy, says Kevin Fingerman, a professor in energy and climate at Humboldt State University who studies the impact of biofuels. Burning gas from agricultural waste could generate power while also transforming methane into less-potent CO2, creating a net negative carbon footprint (even better than wind or solar); however, chopping down a forest without regrowing it to fuel a power plant could be even more polluting than burning coal.

Crucially, these trade-offs depend on what we’re actually trading off — they may be improvements relative to burning coal, but in locations with strict renewables quotas, investment in hydro or biomass might happen at the expense of sources such as solar and wind, which are more assuredly as close to carbon-neutral as possible. That said, unlike other renewable sources, we can control when hydro and biomass plants generate power, so perhaps the better comparison is against a baseload source such as natural gas or nuclear. These different comparisons mean that “anybody who has a bone to pick on either side of this [debate] can tell whatever story they want to tell” while still using valid scientific analysis, Fingerman says.

The key takeaway: “Renewable” is not necessarily synonymous with “carbon-neutral.” (Carrie Annand, executive director of the trade body Biomass Power Association, asserts that biomass is both — so long as forests are consistently growing, as they are in the U.S. The National Hydropower Association did not respond to OZY’s requests for comment.) So let’s get our facts straight before celebrating the impending renewables revolution.

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