Rapid Removal of Atmospheric CO2 by Urban Soils.

Carla-Leanne Washbourne,David A C Manning,Phil Renforth,Elisa Lopez-Capel,Philippa L Ascough

doi:10.1021/es505476d

Abstract

The measured calcium carbonate content of soils to a depth of 100 mm at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 t of CO2/ha (8.5 kg of CO2 m(-2)) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from the 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. 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 fewer than 12000 ha of urban land to maximize calcite precipitation has the potential to remove 1 million t of CO2 from the atmosphere annually. The maximal global potential is estimated to be approximately 700-1200 Mt of 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.

Highlights

There is a global commitment to reducing greenhouse gas emissions; the U.K
Pacala and Socolow estimated that 26 Gt of CO2 year−1 by 2050 would need to be removed from the atmosphere to compensate wholly for anthropogenic emissions. They propose that a number of individual mitigation approaches may potentially be used in unison to remove sized “stabilization wedges” of 4 Gt of CO2 year−1 each by 2050
Using stable and radiogenic isotope analysis, we unambiguously demonstrate the sequestration of modern atmospheric carbon dioxide

Summary

■ INTRODUCTION

There is a global commitment to reducing greenhouse gas emissions; the U.K. Government is currently committed to an 80% reduction by 2050 (against a 1990 baseline). Work on the in situ weathering of natural and artificial silicates[9,11−20] has shown that artificial silicates and mineral wastes (such as construction and demolition waste, iron and steel slag, and mine tailings) in soil settings rapidly weather with the associated formation of carbonate minerals This process is influenced by a number of physical and environmental factors, including small particle size and large surface area, poor crystallinity, and degree of exposure through proximity to the ground surface or position relative to the water table. Thermogravimetry-differential scanning calorimetry coupled with quadrupole mass spectrometry (TG-DSC-QMS) was conducted for 6 samples (3 for 2010, 3 for 2012) using a Netzsch Jupiter STA449C TG-DSC system connected to a Netzsch Aeolos 403C QMS instrument

■ RESULTS AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES