Mitigating environmental impacts and reducing nitrogen footprint by novel tripartite pig husbandry with maximized waste recycling

Abstract

Pig husbandry requires high resource input and is a known heavy greenhouse gas (GHG) emitter. This study proposed a novel tripartite pig husbandry system (high-yielding rice-dry AD-MP production) with maximized waste recycling technologies. It assessed the system's nitrogen footprint (NF), and environmental impacts categorized into global warming, acidification, eutrophication, and biological toxicity, using life cycle assessment (LCA). Conventional pig husbandry with pig manure treated by wastewater treatment and solid waste composting serves as the base scenario.

Substituting corn in pig's feed with locally grown, high-yielding rice can reduce the impacts of global warming, acidification, eutrophication, and biological toxicity by 29.1 %, 56.4%, 40.3%, and 63.9%, respectively, and NF by 54.7%. On the other hand, the MP incorporates the carbon of biogas and nitrogen of digestate into biomass, which is a significant carbon and nitrogen sink for the novel tripartite system. MP production could markedly mitigate the evaluated categorized environmental impacts of pig husbandry by up to 80∼90%, owing to the increased output of overall proteins. Also, the biogas upgrade products can be versatile, using carbon and nitrogen from dry AD as feed. The tripartite pig husbandry system is carbon-lean, which could lessen the burdens associated with conventional pig husbandry by maximizing waste recycling and closing the loops as a circular bioeconomy model, presenting a promising configuration for next-generation pig-raising industries.