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| 08/31/16

Negative emissions tech may have negative social fall-out


Corruption, land-grabs, competition for freshwater, and trade-offs for food production are just a handful of the social and economic challenges facing the upscaling of negative emissions technologies, according to social scientists.

Negative emissions technology—which draws down atmospheric greenhouse gases (GHGs) via mechanisms such as direct air capture of carbon—is increasingly being viewed by experts as an essential add-on to mitigation efforts to order to achieve a net reduction in emissions and stay below 2°C degrees of warming, as agreed upon at the Paris UN talks.

Up to now, much of the academic conversation regarding negative emissions has focussed on the technological feasibility.

But a new paper by Cornell sociologist Holly Jean Buck appearing in the journal Climatic Change offers a survey of the considerable social and economic hurdles that will have to be overcome if such technology is to be rolled out at scale.

Enhanced weathering for example involves boosting the natural creation of limestone, whereby over geological time periods, carbonate or silicate minerals dissolve in rainwater and carbon dioxide (CO2) is sequestered via chemical reactions that form bicarbonate ions. The simple spreading of crushed minerals out over a plot of land artificially speeds up the process. While this is a relatively low-tech option, according to the paper, to draw down 50 parts per million (ppm) of atmospheric CO2, enhanced weathering could cost as much as $600 trillion for the mining, grinding and transportation of the rock. (To stay in the safe ‘Goldilocks’ temperature, we need to get down to 350 ppm, compared to our current concentration around 400 ppm). Moreover, some of the tropical lands recommended as geologically suitable for enhanced weathering happen to be in places with poor governance practices, such as the Democratic Republic of the Congo.

Direct air capture (DAC), in essence sucking CO2 out of the air, has a very high energy cost, potentially using clean energy resources that are already needed elsewhere to decarbonise electricity, transportation, heating and industrial processes. For example, capturing 13 gigatonnes of CO2 in this way, would require some 40 million hectares of land to produce sufficient solar-derived electricity.

BECCS envisages the use of biomass to produce fuel and thereby drawing down CO2 as plants grow. But instead of letting the CO2 escape back into the air when the fuel is combusted, CCS sequesters it, thus resulting in a net reduction in GHGs. However, to achieve 3.3 gigatonnes of negative emissions via BECCS using high-energy crops such as willow and poplar would require the use of as much a quarter of the world’s agricultural land, and up to three quarters of global annual nitrogen fertilizer production.

Large-scale afforestation, perhaps the simplest of negative emissions tech, is easiest in less developed areas, particularly in sub-Saharan Africa. But existing forestry plantations in such regions already can result in restrictions of use of common land for crop cultivation, grazing, and collection of firewood, and even jail time for ‘trespassing’.

However, the researchers do not suggest negative emissions practices should be avoided. Instead more robust governance structures in the developing world for example can help resolve some concerns, and agricultural breakthroughs to reduce the land footprint can reduce the pressure on farming for food.


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Negative emissions tech faces not just feasibility challenges but social and economic hurdles too

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