Green, Hannah, Larsen, Peter, Liu, Yang, and Nelson, Paul (2024) Carbon dioxide removal via weathering of sugarcane mill ash under different soil conditions. Applied Geochemistry, 165. 105940.

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Abstract

Sugarcane mill ash has been suggested as having high potential for carbon dioxide removal (CDR) via enhanced weathering (EW), but this had not been quantitatively assessed. The aims of this study were to 1) assess the CDR potential of various sugarcane mill ashes via EW, and 2) investigate the impact of soil conditions and mill ash properties on the CDR. This was done by characterising physical and chemical properties of five mill ashes from Australia and simulating weathering using a one-dimensional reactive transport model. The model was parameterised to simulate weathering of 100 t/ha of wet ash (47–65% water) or crushed basalt for 15 years under various combinations of soil pH and carbon dioxide partial pressure (pCO2). A sensitivity analysis was undertaken in a two-level factorial design to test the effect of pH, pH buffering, material surface area, infiltration rate, plant uptake of nutrients, organic matter cation exchange surfaces, and pCO2 on modelled CDR. The simulated CDR of the mill ashes was significantly less than the basalt (p < 0.001) but mostly did not differ significantly between ashes (p > 0.05). Weathering of mill ash removed 0.0–4.0 t CO2/ha (0.00–0.040 t CO2/t wet ash) cumulatively, similar to some basalts and olivine modelled in the literature. The theoretical maximum CDR of the mill ashes (based on amount of weatherable material applied) was achieved in around 5 years. The estimate of CDR varied by orders of magnitude depending on conditions. It was least when initial soil solution pH was lowest (4.5, unbuffered), pH was at 6.5 or less with constant buffering, and pCO2 was low (600 ppm). CDR was also significantly lower when calculated directly from accumulation of carbon in dissolved and solid phases rather than stoichiometrically from cation release. The effects of pH and pH buffering quantified here may explain low measured CDR from EW in field trials on acidic soils and highlight the need for more realistic modelling of pH buffering capacity. Overall, mill ash shows high potential for CDR via EW, especially if lifecycle benefits are considered, although this must be validated in the field.

Item ID:	82525
Item Type:	Article (Research - C1)
ISSN:	1872-9134
Keywords:	Basalt; Carbon sequestration; Enhanced weathering; Industrial by-product; Soil chemistry; Geochemical modelling; Negative-emission technology
Copyright Information:	© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Funders:	Sugar Research Australia (SRA)
Projects and Grants:	2021/101
Research Data:	https://doi.org/10.25903/nffy-zv25
Date Deposited:	23 May 2024 05:41
FoR Codes:	41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410604 Soil chemistry and soil carbon sequestration (excl. carbon sequestration science) @ 50% 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300206 Agricultural spatial analysis and modelling @ 50%
SEO Codes:	19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1903 Mitigation of climate change > 190301 Climate change mitigation strategies @ 100%
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