Guangdong province faces uphill battle for carbon neutrality, biochar offers partial relief

A comprehensive assessment of Guangdong province's land carbon balance reveals that the highly industrialized region has not yet achieved carbon neutrality, registering a substantial net emission of 925.63 Tg CO₂e in 2021. This significant carbon footprint primarily stems from energy consumption, which accounts for 83.8% of total emissions. Against this backdrop, scientists at Zhejiang University, Guangdong University of Technology, Tsinghua University, and Guangdong Academy of Sciences investigated the potential of biochar technology as a carbon dioxide removal (CDR) strategy, determining its capacity to offset a portion of these emissions. The analysis offers essential guidance for formulating regional emission reduction targets and implementing effective mitigation policies as global temperatures rise.

Dissecting Regional Emissions and Resource Potential

To establish Guangdong's land carbon balance, researchers meticulously collected inventory data from five key sectors: land forestry, energy consumption, industrial processes, agricultural activities, and waste management. Methane (CH₄) and nitrous oxide (N₂O) emissions were converted to CO₂ equivalent (CO₂e) to ensure consistent comparison. This granular approach allowed for a detailed understanding of emission sources and carbon sinks within the province from 2016 to 2021, providing a robust baseline for evaluating mitigation strategies.

The investigation further assessed the province's biomass resource potential, identifying collectible agricultural residues, forestry residues, and potential bioenergy crops suitable for cultivation on marginal lands. Utilizing a high-resolution 1 km x 1 km dataset, the team explored two types of marginal lands – low productivity land and abandoned cropland – and five types of bioenergy crops, including Miscanthus, Eucalyptus, Poplar, Switchgrass, and Willow. This detailed resource mapping was critical for subsequently quantifying the carbon removal potential of biochar derived from these varied feedstocks.

Biochar’s Role in Carbon Abatement

Applying life cycle analysis (LCA), the scientists quantified the carbon dioxide removal potential of biomass-derived biochar. The LCA encompassed all stages from feedstock collection and transportation to biochar production, application, and its resulting effects on soil organic carbon (SOC) and N₂O emissions. Different scenarios of biomass utilization were modeled, ranging from a minimum scenario using only 11% of residues to a maximum scenario incorporating all available agricultural and forestry residues, alongside bioenergy crops from both marginal land types.

The findings indicate that under the most optimistic biomass utilization scenario, biochar could achieve a maximum CDR potential of 84.30 Tg CO₂e per year. This represents an offset of 9.11% of Guangdong province's net carbon emissions, showcasing biochar's meaningful yet limited role in achieving regional carbon neutrality. The primary drivers of biochar's CDR were found to be the replacement of fossil fuel combustion with renewable energy (56.9%) and increases in SOC (42.9%), with reduced fertilizer use contributing a smaller fraction. Spatially, the highest biochar CDR potential was concentrated in Northern Guangdong, highlighting the importance of regional resource distribution.

Charting a Path Beyond Biochar

While promising, the results make it evident that relying solely on biochar technology will be insufficient to achieve carbon neutrality in Guangdong province. Urgent and diverse mitigation efforts are necessary, particularly focusing on the dominant source of emissions: energy consumption. This includes a crucial shift toward clean energy alternatives and enhanced energy efficiency across industrial sectors. Technologies such as Direct Air Capture of CO₂ with Storage (DACCS) and optimized cement and concrete utilization are also identified as vital components of a future strategy.

Beyond emission reduction, increasing carbon sinks holds equal importance. The analysis of forest age suggests that younger trees possess greater carbon sequestration capacity. Consequently, prioritizing afforestation/reforestation programs, especially with fast-growing bioenergy crops on marginal lands, can significantly boost carbon absorption. The investigation further points to the substantial potential of biomass-based CDR technologies like Bioenergy with Carbon Capture and Storage (BECCS), suggesting that a combined approach of BECCS and biochar could play a pivotal role in comprehensive carbon mitigation. Furthermore, the vast marine areas of Guangdong province offer avenues for developing ocean-based carbon sinks, such as microbial pumps and ocean fertilization, which merit future exploration, alongside a careful assessment of environmental risks and economic viability.

Dr. Wenneng Zhou, a corresponding author from Guangdong University of Technology, commented on the implications of the findings: "Our research clearly illustrates the scale of the carbon challenge facing Guangdong province and the significant, though partial, role biochar can play. Achieving carbon neutrality will require a multifaceted approach that not only deploys innovative technologies like biochar and BECCS but also fundamentally transforms our energy systems and enhances natural carbon sinks, including those within our marine ecosystems. This study provides a scientific foundation for decision-makers to craft comprehensive, locally tailored climate strategies."

Corresponding Author: Wenneng Zhou

Original Source: https://doi.org/10.1007/s44246-024-00140-1

Contributions: All authors contributed to the study's conception and design. Material preparation, data collection and analysis were performed by Funing Wang, Wenneng Zhou, Xili Wang, Qing Zhao and Mengjie Han. The first draft of the manuscript was written by Funing Wang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.