Indirect carbon emissions of enhanced weathering in Malaysia

Enhanced weathering (EW) of rocks and minerals can be used as a carbon dioxide removal (CDR) technique. EW relies on accelerated geochemical reactions between carbonic acid in rainwater and slightly alkaline minerals to permanently sequester carbon atoms as bicarbonate ions in runoff water. The material needs to be crushed into a fine powder to increase its reactive surface area and then spread on land at a rate calibrated to local weather and soil conditions. However, large-scale EW using virgin material will increase outputs and carbon footprints across various economic sectors to support the CDR system. Input-output analysis is used to model such indirect effects when basalt EW is used in all oil palm plantations in Malaysia to cut greenhouse gas emissions. Results at a fixed electricity carbon intensity show that about half of the direct CDR will be offset by incremental carbon footprints from the mining, electricity generation, and transportation sectors due to the requirements of EW operations; total greenhouse gas emissions are reduced by up to 11.0% to 213.7 Mt CO2 equivalent (CO2e)/y. Cutting the carbon intensity of electricity supply in half reduces emissions further to 126.9 Mt CO2e/y. The scenario analyses demonstrate the synergy between renewable energy deployment and EW implementation, supporting the development of carbon management policies in Malaysia.