Sustainable composting and its environmental implications

The continuous improving economic conditions have resulted in urbanization and intensive breeding industry, producing huge amounts of solid organic waste such as livestock manure, food waste, green waste, and agricultural waste. The disposal and utilization of these solid organic wastes have become an urgent issue, which needs to be properly handled and treated globally, especially in the developing countries. Nowadays, technologies such as incineration, anaerobic digestion, composting, and landfilling have been put forward to treat solid organic waste. Among the different approaches, composting technology has been widely accepted as a cost-effective method to treat the organic fraction of municipal solid waste and to generate a nutrient-rich and sanitized compost that closes the loop of nutrient cycling. Nevertheless, the conventional composting technology still has its environmental and health concerns such as ammonia volatilization, greenhouse gas emissions, availability of heavy metals, pathogen contamination, and antibiotics and antibiotic resistance genes residues. During the composting process, the ammonia emission not only decreases the quality of compost but also causes environmental pollution. In addition, the emission of greenhouse gases including CH₄ and N₂O cannot be neglected because their global warming potential is significantly higher than that of CO₂. Besides, the potential bioavailability of heavy metals and the residual of antibiotics and antibiotic resistance genes in compost would also limit their acceptability for land application. For improving the composting process and reducing the adverse effects of composting, various effective approaches have been proposed in the past two decades. This chapter will introduce the basic concept of composting and its process optimization, the potential environmental problems of composting, and the applications of mature compost.