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Economic benefit analysis of sludge composting plants based on the use of additives
Received:February 10, 2021  
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KeyWord:sewage sludge;composting pattern;additive;cost analysis;economic benefit
Author NameAffiliationE-mail
LIU Yan Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China  
MA Ruonan Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China  
LI Guoxue Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China  
YUAN Jing Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China jingyuan@cau.edu.cn 
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Abstract:
      Exogenous additives based on the in situ control concept can effectively control the generation of pollution gases during the composting process, as well as improve the nutrient content of compost products; however, the economic benefits of its application at the factory scale are still unclear. Taking a sewage treatment plant in Tongliao City of Inner Mongolia as an example, this study systematically analyzed the economic benefits of different composting modes and the use of exogenous additives. The results showed that the strip stack natural ventilation composting process(with WT36 dumper)with a large capacity had relatively low infrastructure investment and operation and management costs. The production cost of compost products with different composting processes without adding exogenous additives ranged from 314.93 to 349.85 yuan·t-1. Using phosphogypsum reduced the production cost of composting by about 6 yuan·t-1; When phosphogypsum was mixed with dicyandiamide, only superphosphate was used, superphosphate was mixed with dicyandiamide, the production cost increased by 5.0%~16.2%. The sale of composting products compensated for the cost of sludge composting and made the sludge composting reach the level of low profit. Among them, the composting process with large-scale natural ventilation and adding phosphogypsum had the best economic benefit: the ratio of production to investment was 3.22, the investment recovery period was the shortest, and the total static investment of the project could be recovered in three years and two months. Therefore, the industrial application of sludge composting using phosphogypsum as an external additive and a large-scale heating and natural ventilation process is economically feasible.