European scientists say that negative emissions technologies (NETs), actively reducing the concentration of greenhouse gases in the atmosphere, offer no silver bullet that can solve climate change.
A survey of the scientific and policy literature on some half dozen different options—from fertilizing the ocean with iron to machines that directly capturing CO2 from the air and then sequestering it—by the European Academies of Science Advisory Council was published this week. The report concludes that the consequences of many such options are potentially too damaging to the environment in other ways when deployed at the colossal scales required, or are still very far from being commercialized.
The document, which can serve as a useful reference for BC and Canada, highlights a real challenge to most policy pathways developed by the Intergovernmental Panel on Climate Change that allow the world to stay within the target of 2C of warming since pre-industrial times. In the IPCC’s database of scenarios, out of the 400 that have a 50 percent chance or better of limiting warming to 2C, 344 assume widespread deployment of some form of NETs.
They do so because the IPCC’s network of researchers believed that reducing emissions would not happen fast enough for the planet to keep within the two-degree guardrail, and some sectors such as aviation and agriculture are just very difficult to decarbonize. As a result, at some point after 2050, NETs were supposed to be deployed to compensate for the presumed overshoot.
The response to the report has been broad with the prevalent themes being that NETs “cannot save” us or should be abandoned. But the authors do not say that NETs can play no role, but rather that they will not contribute at the huge scales required to compensate for inadequate reduction of emissions.
The report concluded that bioenergy with carbon capture and storage (BECCS), which is the technology many of the IPCC scenarios mention, at the scales envisaged would likely threaten food security and biodiversity due to the amount of land needed. BECCS involves growing trees or other bioenergy crops, which naturally take in CO2 from the air, to produce biofuels. When wood pellets are combusted to produce electricity, their emissions would then be captured and stored underground or under the sea floor (carbon capture and storage, or CCS).
Other relatively cheap techniques such as planting billions of trees to create new forest or improving the carbon content of soils, would likely work quite well in principle. But most countries are already grappling with forest and soil loss. This would need to be solved first.
One option has the best potential is direct air capture (DAC) coupled with CCS, or DACCS, the authors say. This high-technology process involves machines that suck CO2 out of the air and then burying it. The challenge here though is that such technology remains at the level of demonstration projects.
Carbon Engineering, a firm based in Squamish, BC, is one of the first such commercial efforts to launch the direct air capture technology, but it remains uncoupled to CCS, and so remains a carbon-neutral rather than carbon-negative solution for the time being.
The report concludes that efforts to develop NETs technologies should continue, particularly the role within them played by CCS. They also recommend that governments develop the necessary CCS infrastructure around hubs of carbon sources to minimize transport costs and offer up UK and Norwegian initiatives along these lines as possible models.
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