Sustainable pathways for pig farming in China: Life cycle assessment of manure management systems and environmental...

Sustainable Development Goals underscore the importance of improved manure management, particularly in scaled pig farming. This study employs life cycle assessment (LCA) to evaluate five manure treatment scenarios across farms of varying sizes in Guangdong, China. The analysis covers manure collection, treatment, application, and credits from resource recovery. Results show that large-scale systems excel in emission reduction, whereas small-scale operations demonstrate higher resource recovery efficiency. Specifically, scenario S1 (large-scale, water-flushed mixing with anaerobic digestion) yielded the lowest carbon emissions (-269.8 kg CO₂-eq), while S4 (small-scale, slurry manure with anaerobic digestion) was most energy-efficient (-9274.6 MJ). Large farms should optimize fertilizer application, and small farms should enhance digestion, composting, and water reduction. Pipeline transport outperforms tankers in energy (-45.9%) and carbon efficiency (-36.5%). These findings provide scientific support for advancing low-carbon circular agriculture and promoting synergies among food, water, and climate systems.