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Rapid removal of atmospheric CO₂ by urban soils

Lookup NU author(s): Carla Washbourne, Dr Elisa Lopez-Capel, Phil Renforth, Professor David ManningORCiD

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).

Abstract

The measured calcium carbonate content of soils to 100 mm depth at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 tonnes CO₂ per hectare (ha^-1) (8.5 kg CO₂ m^-2) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from demolition of concrete structures, which releases Ca that combines with CO₂ ultimately derived from the atmosphere, precipitating as calcite. Stable isotope data confirm an atmospheric origin for carbonate-carbon, and ¹⁴C dating indicates the predominance of modern carbon in the pedogenic calcite. Trial pits show that carbonation extends to depths of 1 m or more. Work at other sites shows that the occurrence of pedogenic carbonates is widespread in artificially created urban soils containing Ca and Mg silicate minerals. Appropriate management of less than 12,000 hectares of urban land to maximise calcite precipitation has the potential to remove 1 million tonnes of CO₂ from the atmosphere annually. The maximum global potential is estimated to be approximately 700-1,200 Mt CO₂ per year (representing 2.0-3.7% of total emissions from fossil fuel combustion) based on current rates of production of industry-derived Ca and Mg-bearing materials.

Publication metadata

Author(s): Washbourne C-L, Lopez-Capel E, Renforth P, Ascough PL, Manning DAC

Publication type: Article

Publication status: Published

Journal: Environmental Science and Technology

Year: 2015

Volume: 49

Issue: 9

Pages: 5434-5440

Print publication date: 05/05/2015

Online publication date: 13/04/2015

Acceptance date: 02/04/2015

Date deposited: 07/04/2015

ISSN (print): 0013-936X

ISSN (electronic): 1520-5851

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/es505476d

DOI: 10.1021/es505476d

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