Carbon uptake by cement in China:Estimation and contribution to carbon neutrality goals

Cement is a widely used construction material globally.Its manufacturing contributes to anthropogenic CO_(2)emissions significantly.However,its alkaline compounds can absorb CO_(2)from the surrounding environment and engage in a carbonation reaction,thereby functioning as a carbon sink.As a major cement producer and consumer,China has an important responsibility to rigorously investigate and accurately account for cement carbon uptake.This study presents a comprehensive analytical model of cement carbon uptake from China,revealing a substantial increase in carbon uptake from 1930 to 2021,peaking at 426.77 Mt CO_(2)(95% Confidence Interval:317.67-874.33 Mt CO_(2))in 2021.The uptake accounts for 8.10% to 45.40% of China’s annual land sink and 2.51% to 4.54% of the global land sink.The cumulative carbon uptake by cement is approximately 7.06 Gt CO_(2)(95%CI:5.22–9.44 Gt CO_(2))during this period,offsetting 50.7% of the total emissions(13.91 Gt CO_(2),95%CI:12.44–17.00 Gt CO_(2))from the cement industry.Notably,cement mortar contributed to most absorption(65.64%).From a life cycle perspective,the service stage of cement materials is the period where the largest CO_(2)sink is formed,accounting for 90.03% of the total.Therefore,the potential for carbon sequestration in cement materials and their waste is enormous.Additionally,the model improves the accuracy of cement carbon accounting,supporting both China and global carbon neutrality assessments.Thus,it is crucial for China to achieve its carbon neutrality goals sooner by prioritizing the environmental benefits of cement materials and wastes,and accelerating the development and commercialization of CO_(2)sequestration technologies for cement and its by-products.

Benefit analysis of multi-approach biomass energy utilization toward carbon neutrality

To reduce greenhouse gas(GHG)emissions,biomass has been increasingly developed as a renewable and clean alternative to fossil fuels because of its carbon-neutral characteristics.China has been investigating the rational development and use of bioenergy for developing its clean energy and achieving carbon neutrality.Substituting fossil fuels with multi-source and multi-approach utilized bioenergy and corresponding carbon reduction in China remain largely unexplored.Here,a comprehensive bioenergy accounting model with a multi-dimensional analysis was developed by combining spatial,life cycle,and multi-path analyses.Accordingly,the bioenergy production potential and GHG emission reduction for each distinct type of biomass feedstock through different conversion pathways were estimated.The sum of all available organic waste(21.55 EJ yr^(-1))and energy plants on marginal land(11.77 EJ yr^(-1))in China produced 23.30 EJ of bioenergy and reduced 2,535.32 Mt CO_(2)-eq emissions,accounting for 19.48%and 25.61%of China’s total energy production and carbon emissions in 2020,respectively.When focusing on the carbon emission mitigation potential of substituting bioenergy for conventional counterparts,bioelectricity was the most effective,and its potential was 4.45 and 8.58 times higher than that of gaseous and liquid fuel alternatives,respectively.In this study,life cycle emission reductions were maximized by a mix of bioenergy end uses based on biomass properties,with an optimal 78.56%bioenergy allocation from biodiesel,densified solid biofuel,biohydrogen,and biochar.The main regional bioenergy GHG mitigation focused on the Jiangsu,Sichuan,Guangxi,Henan,and Guangdong provinces,contributing to 31.32%of the total GHG mitigation potential.This study provides valuable guidance on exploiting untapped biomass resources in China to secure carbon neutrality by 2060.