Life cycle assessment and life cycle cost analysis of compound microbial fertilizer production in China

Abstract

Compound microbial fertilizer (CMF) uses organic waste as a raw material and is an environmentally friendly alternative to conventional chemical fertilizers. However, further analyses of the environmental performance of CMF production are necessary. This study first evaluated the environmental impacts of CMF made from chemical fertilizers, organic wastes, and microorganisms, as well as economic costs. A case study, whose scope encompassed raw materials, transportation, and manufacturing stages was conducted on a fertilizer company in the Hubei Province of China through a combined “cradle-to-gate” life cycle assessment and life cycle cost methodology. Normalization of midpoint results indicated that impacts on fossil resource scarcity, water consumption, and terrestrial acidification are key contributors to the total impacts. The key stage analysis highlighted that the raw materials stage played a critical role (more than 48%) in the environmental performance of the CMF life cycle, followed by the transportation and manufacturing stages (less than 15%). Key substance analysis showed that monoammonium phosphate use is a hotspot and significantly increases the environmental burden of CMF production. Moreover, bentonite and pig manure were also identified as the key substances. Future improvements in the supply chain should focus on monoammonium phosphate, bentonite production, and pig manure extraction. Results of the sensitivity analysis confirmed that controlling pollution from monoammonium phosphate and bentonite should be a priority in realizing clean production. Additionally, an economic analysis indicated that the life cycle cost of CMF was 675.75 CNY/t and that raw material costs contributed the most to the total life cycle cost (over 70%). On the basis of these results, possible recommendations were proposed, such as promoting green procurement of main raw materials, improving the collection technology of pig manure, and extending the scale of CMF enterprises. This study can be significant in assisting relevant stakeholders with decision-making to ensure a balanced tradeoff between an environmentally friendly option and an economically feasible option.