Key Takeaways & Executive Findings
- •• • The coupled bio-drying and aerobic composting process reduced kitchen waste moisture from 77.70% to 58.69% after 1 day of bio-drying, and further to 23.22% after 7 days of silo reactor composting, demonstrating rapid dewatering efficiency critical for high-moisture waste streams. • • Aerobic composting achieved a peak temperature of 68.1°C with >55°C sustained for over 5 days, satisfying the harmless treatment requirements of CJJ 52—2014, ensuring pathogen reduction. • • After 20 days of maturation, the product met NY/T 525—2021 standards: organic matter 51.22%, total nutrients 5.61%, EC <4.00 mS·cm−1, and heavy metals (As 0.23 mg/kg, Hg 0.05 mg/kg, Pb 13.92 mg/kg, Cr 44.28 mg/kg, Cd 0.30 mg/kg) all below regulatory limits. • • High recycle ratios of compost return caused salt accumulation, inhibiting microbial activity and delaying maturation, highlighting the need for optimized bulking agent strategies to balance salinity and structure.
Abstract
Urban and rural multi-source organic waste faces bottlenecks including high compositional heterogeneity, single resource recovery pathways, and uneven product quality. In the Taihu Lake region, active tourism and catering, high greening, and dense water networks generate large volumes of diverse waste with high moisture content, exacerbating these issues. This study evaluated a coupled bio-drying and aerobic composting process at a demonstration center in Linhu Town, Suzhou, Jiangsu Province, employing a three-stage control strategy: gradient dewatering, high-temperature stabilization, and maturation enhancement. Continuous operation showed that kitchen waste moisture content decreased from 77.70% to 58.69% after 1 day of bio-drying, to 23.22% after 7 days of silo reactor composting, and to 17.70% after at least 20 days of maturation. The aerobic composting phase maintained temperatures above 55°C for over 5 days, reaching a maximum of 68.1°C, meeting the harmless treatment requirements of CJJ 52—2014. After 20 days of maturation, the organic fertilizer product had an electrical conductivity below 4.00 mS·cm−1, organic matter content of 51.22%, total nutrient content of 5.61%, and heavy metal concentrations below the limits of NY/T 525—2021. The results provide technical support for efficient treatment and resource utilization of urban and rural organic waste.
1. Introduction
Urban and rural organic waste management faces critical bottlenecks: high moisture content, salinity, and compositional heterogeneity hinder efficient composting, leading to poor product quality and environmental risks. Existing single-material treatments fail to address the complexity of multi-source waste streams, particularly in regions like the Taihu Lake area where tourism and agriculture generate diverse waste with moisture exceeding 70%. The coupled bio-drying and aerobic composting process offers a promising solution by integrating rapid dewatering with high-temperature stabilization, but its industrial-scale application to multi-source waste remains underexplored.
This study addresses the gap by evaluating a full-scale demonstration center employing a three-stage control strategy: gradient dewatering, high-temperature stabilization, and maturation enhancement. The process leverages bio-drying to reduce moisture efficiently, followed by aerobic composting to achieve pathogen reduction and organic matter stabilization, and finally maturation to improve product quality. By systematically assessing material properties and product quality against national standards, this work provides a replicable engineering paradigm for regions facing similar waste management challenges.
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YAO Sheng, TANG Ruolan, MA Ruonan, MA Jingyuan, PAN Jiapeng, LI Ji, LI Guoxue, YUAN Jing (2026). Synergistic Composting of Urban and Rural Multi-Source Organic Waste and Product Quality Evaluation: A Case Study of a Treatment Center in the Taihu Lake Region. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202506041
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Frequently Asked Questions
What are the critical operational parameters for achieving rapid moisture reduction in high-moisture kitchen waste?
The bio-drying stage reduced moisture from 77.70% to 58.69% within 1 day, using a 40 m³ horizontal bioreactor with dual-shaft asymmetric stirring, U-type bottom heating, and forced aeration. The process operated with intermittent stirring (125 min on, 35 min off) and continuous aeration, achieving a moisture reduction of ~19 percentage points in 24 hours.
How does the process ensure pathogen inactivation and compliance with harmless treatment standards?
The aerobic composting stage in the silo reactor maintained temperatures above 55°C for over 5 days, with a peak of 68.1°C, satisfying the requirement of CJJ 52—2014 for pathogen reduction. This high-temperature phase is critical for eliminating pathogens and ensuring product safety.
What are the trade-offs of using compost return as a bulking agent, and how does it affect product quality?
High recycle ratios of compost return (up to 30% of feedstock) led to salt accumulation in the compost matrix, increasing electrical conductivity and inhibiting microbial activity, which delayed maturation and reduced organic matter degradation efficiency. This resulted in a product with EC <4.00 mS·cm−1 after 20 days of maturation, but the process required careful management to avoid salinity stress.
How does the final product quality compare with national organic fertilizer standards?
After 20 days of maturation, the product met NY/T 525—2021 standards: organic matter content was 51.22% (≥30% required), total nutrients were 5.61% (≥4.0% required), and heavy metal concentrations (As 0.23 mg/kg, Hg 0.05 mg/kg, Pb 13.92 mg/kg, Cr 44.28 mg/kg, Cd 0.30 mg/kg) were all below the maximum allowable limits (As 15, Hg 2, Pb 50, Cr 150, Cd 3 mg/kg).
What are the scalability and economic considerations for implementing this coupled process in other regions?
The process is particularly suitable for regions with high moisture waste (>70%) and abundant organic waste sources, such as the Taihu Lake area. The use of bio-drying reduces the need for external energy for drying, and the closed reactor system minimizes odor emissions. However, the cost of bulking agents like sawdust and the need for optimized aeration and stirring systems must be evaluated against local waste composition and economic conditions.
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