State-of-the-art on animal manure pollution control and resource utilization

The animal farming (AM) is one of the oldest and most traditional industries in the world. However, it generates a significant amount of waste in the form of AM. This waste is a renewable resource that is low-cost, widely available, and easily accessible. Despite its potential benefits, traditional disposal methods such as landfills or lagoons can cause environmental problems such as the eutrophication of water bodies, significant greenhouse gas emissions, and the enrichment of heavy metals in the soil. AM has a low calorific value and can replace traditional non-renewable fossil energy. It is also rich in nutrients that can promote plant growth. As such, finding effective and rational ways to use AM is a hot topic of current research. This review aims to outline the forms of heavy metals, antibiotics, nitrogen, and phosphorus pollution in AM and how to control them. It also summarizes the technological progress and influencing factors of AM in feed, fertilizer (composting), and energy (direct combustion, anaerobic fermentation, anaerobic fermentation, and bio-hydrogen production) over the past decades. The risks associated with current AM treatment technologies are also discussed, along with a proposed outlook for the future. This review provides new ideas for the resource utilization of AM and new directions to reduce greenhouse gas emissions.