Researchers See Hope for Reversing Climate Change Using Carbon Capture

By Elizabeth Harball, E&E reporter
7/13/2013 8:25:04 AM

A new study by European researchers offers a glimmer of hope that carbon capture technology coupled with plant-based fuels could halt -- and even reverse -- rising temperatures.

Published this week in the scientific journal Environmental Research Letters, the paper suggests that the widespread use of bioenergy with carbon capture and storage after the year 2050, coupled with significant growth in renewables, could potentially bring down the mercury on an overheated planet, even if the 2-degree-Celsius threshold is breached.

But this finding does not come without caveats. First, bioenergy with carbon capture and storage (BECCS) won't be enough to save the world from climate change if it fails to nearly eliminate its use of fossil fuels; the researchers used a model that assumed huge gains in the renewable energy sector.

"This isn't a get-out-of-jail-free card," said Niclas Mattsson, researcher with the Department of Energy and Environment at Chalmers University of Technology in Göteborg, Sweden, and co-author of the study.

"Reversing warming requires negative emissions on a global scale. That's only possible if we first get down to zero," he said.

Also, while experts say it's possible that carbon capture technology could become widely available by the middle of this century, other major technical hurdles stand in the way.

Plant-based fuel makes negative emissions possible

BECCS is currently considered one of the most attractive options for not only reducing emissions, but decreasing the amount of greenhouse gases in the atmosphere.

By trapping emissions before they are released and pumping them into rock formations deep underground, carbon capture and storage technology could allow fossil fuel power plants to provide carbon-neutral energy.

But by substituting bio-feedstocks such as sugar cane or switch grass for fossil fuels, this process becomes carbon-negative. Plants naturally capture atmospheric carbon as they grow, and when they are burned as biomass for energy, the same amount of carbon is released. By taking the carbon dioxide from the burned biomass and sequestering it underground, BECCS effectively removes the greenhouse gas from the atmosphere.

Photo by: Flickr user navin75

If, coupled with strong growth in renewable energy, BECCS projects were established around the globe by 2050, the new research states that the technology could remove enough emissions to reduce temperatures by 0.06 C per decade.

This would be enough to bring atmospheric carbon dioxide concentrations down to a manageable level by 2150 -- perhaps not soon enough for our generation, but sufficient to offer a brighter outlook for the future.

Could we make enough biomass?

Beyond ramping up the use of renewables, there are other challenges to overcome before BECCS can make a dent in atmospheric carbon dioxide levels.

Today, carbon capture technology, even without the bioenergy component, is moving forward at a glacial rate; there are no large-scale projects currently operating in the power sector. Also, it's hard to make sure that the biofuel used is truly carbon-neutral. For example, the math doesn't add up if the biomass has to be transported long distances by diesel trucks.

But according to climate expert Christopher Field, director of the Department of Global Ecology at Stanford University, the widespread use of BECCS isn't necessarily limited by technology.

"BECCS deserves a lot of research," he said. "I think that all the pieces look like they are conceptually sound. We have good experience deploying all the pieces at industrial scale. There is no reason that we can't connect the carbon capture and storage piece with the biomass energy piece in order to make a system that works."

But the main limitation to the large-scale deployment of BECCS as envisioned in the new study is the availability of biomass. Each year, the world uses about 500 exajoules of the total energy supply. Field estimated that biomass could potentially supply only about 30 to 45 exajoules to the total.

According to his research, biomass energy can realistically contribute to less than 10 percent of the global energy system, when leaving enough land to grow food, to provide us with fresh air and to allow other species to survive (ClimateWire, Feb. 25).

The new research assumes a much larger amount of biomass will be available, using the Intergovernmental Panel on Climate Change's more ambitious projections that the fuel could supply 100 to 300 exajoules by 2050.

"It's not impossible, but a lot of things would have to go right," Field said. "You'd have to have access to a lot of forest resources, and you'd have to have a system in place so that you could manage a lot of the world's landscape for biomass energy production."

BECCS offers hope for a way back

In their study, Mattsson and his co-authors emphasize that biomass supply is a big roadblock for a scenario where BECCS brings temperatures down from the 2-degree benchmark, estimating it would require the use of one-third of global cropland.

"There's no question if this is going to be possible, we're going to need to put bioenergy on a lot of land," Mattsson said.

However, Mattson said his study should encourage policymakers to not lose hope in the 2-degree target, despite reports that the world is on trajectory to fall short of this goal (ClimateWire, June 10).

"Even if we can't strictly stay under 2 degrees, at least let's keep it on the table. ... Don't start talking about higher targets, because that's sending the wrong message," Mattsson said.

"[BECCS] is the one method that I've seen that means that we could eventually reach ambitious targets," he added.

"The main thing is that committed warming isn't committed when there are negative emissions."

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.

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