概要

Rapid urbanization in China has substantially increased the quantity of liquid waste in municipalities, and has simultaneously engendered massive investments in wastewater conveyance and treatment. This increase in the number of wastewater treatment plants has generated a sharp rise in the volume of sludge, the byproduct of the treatment process. While the pollution is a serious local environmental problem, sludge treatment is also a valuable global opportunity to capture and reuse the considerable potential energy and reduce greenhouse gases otherwise emitted during the treatment process. All countries undergoing rapid urbanization, China included, are faced with the need for effective and sustainable solutions for sludge disposal. To ensure the sludge does not pollute the land, water, or atmosphere, cities have invested in various technologies aimed at recycling sludge into compost, energy, and biochar. Among these, the idea of “capturing” byproducts of the anaerobic digestion process is a notable option. Xiangyang City of Hubei Province, China was perhaps one of the first cities in a developing country to explore such a process by investing in a system of “high-temperature thermal hydrolysis, anaerobic digestion, and methane capture and utilization.” This paper summarizes Xiangyang’s experiences and provides insights as to how other cities in China and other developing countries facing similar challenges can address their sludge disposal problems in a sustainable manner.

关键发现

WRI评估了武项目获得“ 3E”的程度 - 环境，能源和经济 - 效果，即污泥的排毒，稳定，减少和资源回收。以下是关键发现：

  • Environmental benefits:
    • 营养恢复：通过腾腾的沉积物，可以回收96％的氮和99％的磷。
    • 温室气体排放减少：在Xiangyang项目的21年合同期间，1）估计只有13,000公吨的二氧化碳等效估计将处置230万吨的污泥和厨房废物（CO）2e) through co-digestion approach; 2) the co-digestion process will reduce 98% and 95% of greenhouse gas emissions compared to incineration and landfill; 3) the biochar produced during the treatment process will be used as a soil enhancement in planting of 4.54 million saplings in total; the mature trees that grow from these saplings will eventually accumulatively sequester an additional 15.75 million metric tons of CO2e。
  • 活力benefits:通过热水解和厌氧消化，武项目将产生4540万m3在21年运行中的天然气（NG）。可以压缩这种数量的NG以产生压缩天然气（CNG），并更换约60,000 m3汽油，导致140,000公吨的CO额外减少2E排放。
  • 经济效益：The project received both political support from the municipal government, and financial support in the form of low-interest loans from an international financial organization, KfW Bankengruppe of Germany, as well as a Chinese policy bank-the Export-Import Bank of China. This “government-bank-enterprise” partnership was key in establishing long-term contractual agreements that ensured a harmonization of interests between all parties.

其他关键发现：

  • Xiangyang项目成功实现了减少污染物，资源回收，污泥处理中接近零的碳排放以及城市可再生能源的产生。

该项目成功地恢复了污泥中的营养，并避免了对水体的污染。更重要的是，Xiangyang项目抓住了从污泥和厨房废物中恢复生物能源（沼气）的机会城市的发展目标。

  • A market-oriented perspective for the design of sludge treatment is vital to the economic success.

Xiangyang项目展示了设计一个考虑市场需求的污泥（和其他有机废物）处理的完整价值链的重要性。因此，选择了木马的特定技术，并考虑了治疗收回产品CNG和Biochar的市场潜力。这些产品的潜在市场的存在确保了可持续的资本流。

  • 通过公私伙伴关系（PPP）获得了政府，金融部门和私营部门的支持，这使得能够实现一系列复杂的发展目标所需的激励措施。

The successful implementation of a build-operate-own (BOO) contracting arrangement underscored the importance of cooperation between the local government and the private sector. The pairing of the public and private sectors of the model ensures the availability of concessional financing to bridge the viability gap that is likely to emerge during the initial investment phase. Ideally, global climate and other international financial funds will target the mitigation of global externalities, by methods such as capturing methane and other GHGs. The availability of financial incentives will induce the private sector to enter into and promote a circular economy for the stabilization of sludge and the reclamation of sludge byproducts. This, in turn, will help enhance the viability of such projects, and help drive costs down via competition and innovation, making the market even more attractive for private capital investment.