The increasing concentration of greenhouse gases, particularly CO₂, CH₄, and N₂O, is driving global warming, posing a significant challenge to the Paris Agreement's 1.5 °C warming target. China, a major contributor to global carbon emissions, aims to achieve carbon neutrality by 2060. Organic waste treatment is a significant source of these emissions, with UROSW accounting for over 60% of total solid waste in China. Current disposal methods, primarily incineration and landfilling, lead to substantial greenhouse gas emissions. While existing resource utilization measures such as dehydration, anaerobic digestion, and aerobic composting have been implemented, their effectiveness in reducing emissions is limited, particularly when dealing with diverse organic waste streams separately. This study aims to address this gap by investigating an optimized resource utilization scheme for minimizing the carbon footprint of UROSW management in China.

Existing research highlights individual resource utilization methods for organic waste, including dehydration and drying for increased calorific value and biomass fuel production, anaerobic digestion for biogas generation, and aerobic composting for organic fertilizer production. However, these approaches often suffer from inefficiencies and high energy consumption, hindering effective emission reduction. Studies focusing on collaborative treatment and utilization of various organic waste streams show improved efficiency and emission reduction. For example, synergistic composting of different materials has demonstrated reduced maturation time, improved fertilizer efficiency, and decreased greenhouse gas emissions. Biochar production from organic waste offers further potential for carbon sequestration and emission reduction. However, a comprehensive, regionally-scaled approach for optimal carbon emission reduction across diverse UROSW types remains unclear. This study aims to fill this knowledge gap.

This study employed a multi-faceted approach involving material flow analysis (MFA), life cycle assessment (LCA), and economic analysis. First, the researchers collected data on UROSW production from 34 provincial-level regions in China, including municipal sludge, kitchen waste, garden waste, straw, livestock manure, biogas residue, and cyanobacterial algal mud. A logistic population model was used to forecast UROSW production up to 2030. Material flow analysis was then conducted to track the flow of carbon in different UROSW management scenarios. Three scenarios were considered for each urban and rural organic waste (MOSW, UOSW). These include a baseline scenario (BS) representing current practices and two mitigation scenarios (MS1, MS2 for MOSW; CS1, CS2, CS3 for UOSW) incorporating advanced technologies. Finally, the proposed URIRP was modeled, and its environmental and economic benefits evaluated. The LCA was conducted using SimaPro with the ReCiPe 2016 methodology, assessing various environmental impacts. Economic analysis compared the costs and profits of the different scenarios, considering revenue from by-products and subsidies.

The study found that China's UROSW production is substantial, exceeding 2.5 billion tons annually. The baseline scenario (BS) resulted in significant carbon emissions (690 Mt CO₂e yr⁻¹), primarily methane from landfills. Implementing separate urban and rural treatment (MS2 and CS3) reduced emissions by 53.6%. The proposed URIRP significantly further reduced emissions to 283 Mt CO₂e yr⁻¹, representing a 58% reduction compared to the baseline. By 2030, URIRP is projected to reduce emissions by 410 Mt CO₂e yr⁻¹, offsetting 6% of the power sector's emissions or 46.1% of the agricultural sector's emissions. URIRP also led to substantial reductions in other pollutants (particulate matter by 21%, SO₂ by 27%, NOx by 2%, and solid waste by 33%). The use of biochar-based organic fertilizer improved soil quality, increasing organic matter content by 0.25% and improving crop yields. The economic analysis indicated that URIRP would generate an annual profit of $8.8 billion, contrasting sharply with the substantial costs associated with the baseline scenario.

The study's findings demonstrate the significant potential of URIRP to contribute to China's carbon neutrality goals. The synergistic integration of various organic waste streams, coupled with advanced technologies, optimizes resource utilization and drastically reduces greenhouse gas emissions. The economic benefits of URIRP further highlight its sustainability and feasibility. The findings support a shift from disposal-oriented to resource-recovery strategies for organic waste management, which should improve air and soil quality, and reduce the reliance on chemical fertilizers. The successful implementation of URIRP in China offers valuable lessons and a potential model for other countries facing similar waste management challenges.

This study highlights the effectiveness of the URIRP in achieving low-carbon and high-value utilization of UROSW in China. The substantial reduction in greenhouse gas emissions, coupled with economic benefits and improved resource recovery, strongly supports its implementation. Future research could focus on refining the URIRP model for different regional contexts, exploring technological advancements to further reduce emissions, and investigating the long-term impacts on soil health and biodiversity.

While the study provides a comprehensive analysis of UROSW management in China, certain limitations exist. The analysis primarily focuses on the Taihu Lake region and may not fully capture the diversity of waste characteristics and management practices across the entire country. Furthermore, the economic analysis does not consider all potential costs, such as infrastructure development, and the long-term economic benefits may vary across regions. Future studies should consider a more granular regional-level analysis and incorporate more comprehensive cost-benefit evaluations.