Negative Emissions Technologies (NETs)

Dealing with CO2 directly is a matter of first avoiding combustion of fossil fuels and secondly of sequestering CO2 that is released. To avoid climatic tipping points, what options exist? This is the topic of a new paper released on Feb 15th out of the Smith School at Oxford.

This paper has found that the technical potential for NETs by 2050 is in the order of 120 GtCO2 cumulatively, which is approximately 2.5 years of current global greenhouse gas emissions. While this may provide some time, there are several important caveats:

  • carbon budgets and the policies applied to implement them are not in ‘sync’, so a slightly larger carbon budget is unlikely to perfectly translate into commensurately ‘softer’ policies and regulations;
  • technical potentials are often much higher than ultimately realised potentials (an issue emphasised throughout this paper);
  • policymakers might not ‘bank’ a projected and uncertain carbon budget extension in the near term, but decide to wait until NETs deployment is successful. Due to the effects of discounting, this would then have little impact on firm or investor decision-making today.

Stranded Carbon Assets and Negative Emissions Technologies
Working Paper
February 2015

Negative Emissions Technologies (NETs) have the potential to remove carbon dioxide (CO2) from the atmosphere and this could reduce the impacts of ocean acidification and anthropogenic climate change. NETs are a family of technologies that encompass diverse options, including: Afforestation, Agricultural Soil Carbon Sequestration, Biochar, Bioenergy with Carbon Capture and Storage (BECCS), Direct Air Capture (DAC), Ocean
Liming, Enhanced Weathering, and Ocean Fertilisation. NETs may help to extend carbon budgets and therefore provide more time to reduce emissions. Carbon budgets
represent our best estimates of the amount of CO2 that may be released into the atmosphere before it becomes unlikely that the 2°C target can be avoided. Based on the latest IPCC work2 the current carbon budgets are 900, 1050 and 1,200 GtCO2 under 66%, 50% and 33% probabilities, respectively. In 2010, gross annual Greenhouse Gas (GHG) emissions totalled ~50 GtCO2-equivalent. Ocean and land sinks absorb just over 50% of the emissions resulting in net atmospheric emissions increasing by around 22 GtCO2 pa and therefore an average ~3 ppm increase of atmospheric CO2 concentration per year, although the fraction absorbed by these sinks is falling.

Given these uncertainties and deployment challenges, it would be foolhardy for an owner or operator of carbon intensive assets to assume that NETs will fundamentally alter the carbon budgets that they may face due to climate policy and regulation. This is particularly the case for point source emissions from power stations, as there are already a number of viable options to deal with these emissions. It would be hard to argue that resorting to highly uncertain NETs prior to undertaking a variety of mitigation options is an economically or socially desirable course of action.

To remove CO2 on a comparable scale to the rate it is being emitted inevitably requires effort and infrastructure on a comparable scale to global energy or agricultural systems. Combined with the potentially high costs and energy requirements of several technologies, and the global effort needed to approach the technical potentials discussed previously, it is clear that very large-scale negative emissions deployment, if it were possible, is not in any sense preferable to timely decarbonisation of the energy and agricultural systems.

About arnulfo

veterano del ciberespacio
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