Biochar technology cannot offset land carbon emissions in Guangdong province, China

As a highly developed region, Guangdong province has substantial industrial emissions. Its subtropical monsoon climate, characterized by abundant hydrothermal conditions, contributes to a substantial biomass potential. The adoption of potential biomass-based carbon dioxide removal (CDR) technologies, such as biochar, presents an opportunity to mitigate emissions and work towards carbon neutrality in the future. However, the current state of the land carbon balance and the CDR potential of biochar in Guangdong province remains unclear. We first calculated the land carbon balance based on inventory data. Then we estimated the CDR potential of biochar derived from agricultural residues, forestry residues, and bioenergy crops cultivated on marginal lands in Guangdong province using life cycle analysis (LCA). Results show that Guangdong province has not yet achieved carbon neutrality, with a net emission (carbon emissions remaining after offsetting by carbon sinks) of 925.63 Tg CO2e (CO2 equivalent, 1Tg = 106 t) in 2021. Emissions from energy consumption account for the highest proportion, contributing 83.8% of total emissions. In the highest biomass utilization scenario, the maximum CDR potential of biochar derived from all biomass types reaches 84.30 Tg CO2e yr-1, which could offset 9.11% of net carbon emissions in Guangdong province. Our findings provide crucial guidance for setting emission reduction targets and implementing effective mitigation strategies in Guangdong province under temperature warming. Graphical Abstract: (Figure presented.) © The Author(s) 2024.