Potential and costs of carbon dioxide removal by enhanced weathering of rocks

Abstract

The chemical weathering of rocks currently absorbs about 1.1 Gt CO 2 a −1 being mainly stored as bicarbonate in the ocean. An enhancement of this slow natural process could remove substantial amounts of CO 2 from the atmosphere, aiming to offset some unavoidable anthropogenic emissions in order to comply with the Paris Agreement, while at the same time it may decrease ocean acidification. We provide the first comprehensive assessment of economic costs, energy requirements, technical parameterization, and global and regional carbon removal potential. The crucial parameters defining this potential are the grain size and weathering rates. The main uncertainties about the potential relate to weathering rates and rock mass that can be integrated into the soil. The discussed results do not specifically address the enhancement of weathering through microbial processes, feedback of geogenic nutrient release, and bioturbation. We do not only assess dunite rock, predominantly bearing olivine (in the form of forsterite) as the mineral that has been previously proposed to be best suited for carbon removal, but focus also on basaltic rock to minimize potential negative side effects. Our results show that enhanced weathering is an option for carbon dioxide removal that could be competitive already at 60 US $ t −1 CO 2 removed for dunite, but only at 200 US $ t −1 CO 2 removed for basalt. The potential carbon removal on cropland areas could be as large as 95 Gt CO 2 a −1 for dunite and 4.9 Gt CO 2 a −1 for basalt. The best suited locations are warm and humid areas, particularly in India, Brazil, South-East Asia and China, where almost 75% of the global potential can be realized. This work presents a techno-economic assessment framework, which also allows for the incorporation of further processes.

Managing for soil carbon sequestration: Let’s get realistic

“…Carbon sequestration by the application of wollastonite at Hubbard Brook costs about $10,000/ton of C over the 11-year period, based on recent commodity prices for wollastonite (e.g., https:// www.alibaba.com/showroom/wollastonite-price.html. )-far higher than most policies proposed to stimulate carbon sequestration and higher than recent similar calculations (Strefler, Amann, Bauer, Kriegler, & Hartmann, 2018). Hartmann et al (2013) calculated that the provision of enough silicate minerals to enhance significantly CO 2 uptake by soils would entail a huge increase in the annual transport of material commodities in world trade.…”

Negative emissions—Part 2: Costs, potentials and side effects

“…Uncertainty surrounding the development and implementation costs of this technology currently remains a major barrier (see section 3.3). Finally, Strefler et al (2018a) assess the techno-economic potential for land-based enhanced weathering at about 5 GtCO 2 for both basalt and fosterite. Adding it to the technology portfolio reduces the carbon price (Strefler et al 2018a).…”

“…Finally, Strefler et al (2018a) assess the techno-economic potential for land-based enhanced weathering at about 5 GtCO 2 for both basalt and fosterite. Adding it to the technology portfolio reduces the carbon price (Strefler et al 2018a). Because EW does not compete with BECCS, this technology might be particularly valuable if other NETs options are limited.…”

“…For comparison, world lime production from 2005-2014 averaged 0.34 Gt yr −1 (Corathers 2015). According to Strefler et al (2018a) the annual application of 3 Gt yr −1 basalt might sequester 1 GtCO 2 yr −1 .…”

System Models of Sulfur‐, Electricity‐, and Methane‐Powered Biological Carbon Capture for Negative Emissions

“…In contrast, Strefler et al estimated the energy needs for enhanced weathering at slightly over 0.2 GJ t −1 CO 2 (55.4 kWh t −1 ). Given this value, the energy needs to sequester 2018 emissions would be just 7 quads, mostly in the form of rock mining and grinding and comminution.…”