Net primary production of annual crops and cumulative CO2 emissions by nation. Graphic: Beerling, et al., 2018 / Nature Plants

21 February 2018 (Nature) – Decarbonization of the world’s economy would bring colossal disruption of the status quo. It’s a desire to avoid that change — political, financial and otherwise — that drives many of the climate sceptics. Still, as this journal has noted numerous times, it’s clear that many policymakers who argue that emissions must be curbed, and fast, don’t seem to appreciate the scale of what’s required.What would negative emissions look like? A Perspective this week in Nature Plants offers another glimpse, and it’s not pretty (D. J. Beerling et al. Nature Plants http://dx.doi.org/10.1038/s41477-018-0108-y; 2018). The review focuses on the idea of enhanced weathering, which aims to exploit how many rocks react with carbon dioxide and water to form alkaline solutions that, over time, find their way into the sea. It’s one of a number of proposed negative-emissions technologies.In theory, enhanced weathering could lock up significant amounts of atmospheric carbon in the deep ocean. But the effort required is astounding. The article estimates that grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas — of US agricultural land every year would soak up 13% of the annual global emissions from agriculture. That still leaves an awful lot of carbon up there, even after all the quarrying, grinding, transporting, and spreading. [Considering the rate at which humans are actively degrading the world’s soil resource, it’s ludicrous to think that we’ll undertake a massive “basalt-fertilization” project. –Des]It’s not hard to see why many climate scientists have dismissed the near-impossible scale of required negative emissions as “magical thinking”. [more]

Why current negative-emissions strategies remain ‘magical thinking’

ABSTRACT: The magnitude of future climate change could be moderated by immediately reducing the amount of CO2 entering the atmosphere as a result of energy generation and by adopting strategies that actively remove CO2 from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such CO2-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of CO2 capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for CO2 removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.

Farming with crops and rocks to address global climate, food and soil security