Managing liquid digestate to support the sustainable biogas industry in China: Maximizing biogas‐linked agro‐ecosystem balance

Biogas industry in China is developing rapidly. This is particularly the case for livestock farm biogas plants, which are built to treat manure and wastewater. Managing the liquid digestate (LD) generated by anaerobic digestion of livestock wastes is becoming a bottleneck, restricting the sustainable development of the biogas industry in China. The separation of livestock breeding and arable farming, caused by rapid intensive animal husbandry development, is the main reason for the LD problem. Researchers, government representatives, and biogas plant operators in China have invested significant research efforts to maximize biogas-linked agro-ecosystem balance, which is considered as an important solution to the LD problem. This article reviewed these studies and proposed several solutions from the following four aspects: breeding mode, waste treatment mode, LD transportation mode, and LD utilization mode. One proposal is to reduce the scale of newly built livestock farms and disperse them in farmland, by promoting the "company + agent" livestock breeding mode. In this approach, farm scale would be based on the size of available farmland, and would allow for the use of LD in the near farmland. The second approach involves the intense separation of the livestock slurry and further transportation of the LD produced by the thick slurry. The third one is to expand the possible distances for transferring LD, using a pipe network or vehicle supervised by a professional third party. Finally, the development of high value-added products and bringing them to market is the ultimate solution for the future.