Environmental Impact Assessment of Sustainable Pig Farm via Management of Nutrient and Co-Product Flows in the Farm

This study evaluates the environmental impact assessment of sustainable pig farm via management of nutrient and co-product flows in the farm. Manure management and biogas production are among the most promising pathways towards fully utilizing organic waste within a circular bioeconomy as the most environmentally friendly solution mitigating gaseous emissions and producing bioenergy and high-quality bio-fertilizers. The concept of farm management includes rearing pig, growing all the feeds needed, and managing the nutrients and co-product flows in the farm. A consequential life cycle assessment (LCA) was performed to examine three scenarios in which all the generated manure is used as fertilizer for barley cultivation and mineral fertilizer is used where necessary (SC1); produced surplus straw is used for thermal energy generation and maize is used for sale, substituting maize biomass in the market (SC2); and all co-products are circulated in a closed system (SC3). The functional unit (FU) was defined as a "farm with 1000 fattening pigs at farm gate". The analysis showed that heat generation from wheat, barley and legumes straw has a significantly higher positive environmental impact than the use of these cereal straw for biogas production. The partial replacement of mineral fertilizers with digestate has positive environmental effects in terms of abiotic depletion, photochemical oxidation, terrestrial ecotoxicity, freshwater aquatic ecotoxicity, human toxicity, and marine aquatic ecotoxic aspects. The amount of digestate generated on a farm is not sufficient to completely eliminate the use of mineral fertilizers for plant fertilization. The generated pig manure (SC1) and digestate (SC2) is only enough for the fertilization of 8.3% of the total cultivated land of farm applying 22.9 t/ha rate.