Pig Manure Management: A Methodology for Environmentally Friendly Decision-Making

SIMPLE SUMMARY: Intensification of pig farming increases the profitability of farms but also leads to greater local environmental pressure from manure nutrient loss. There are various technologies for pig manure processing. Each technological solution provides specific nutrient content in the end-products (organic fertilisers, effluents, biogas, etc.). The methodology was developed for choosing proper technological solutions for pig farms with due account for the whole variety of combinations of production and natural and climatic conditions. It includes an accurate accounting for nitrogen and phosphorus flows in the manure processing and utilisation chain and considers the limiting factors of the farm and the end-product customer requirements. The methodology was applied to a large-scale pig farm in the Leningrad Region. The best suitable processing technology was identified demonstrating the total amount of nitrogen and phosphorus in the end-products of 278.94 t per year. The developed methodology can serve as an effective tool to reduce manure nutrient loss and mitigate the adverse effect on the rural environment. ABSTRACT: The current trend towards larger pig farms increases their profitability but might harm animal welfare and the environment. More efficient pig manure management is a way to address this challenge. Available manure handling and utilisation systems may feature from 8 to 50% nutrient loss to the environment. Therefore, the proper choice of technological solutions is of high priority. In regard, the study developed a methodology including calculation, analysis and modelling techniques for the accurate accounting of manure amount, its fractions and their nitrogen and phosphorus content for different processing technologies with due regard to the limiting factors of the farm and the end-product consumer requirements. The methodology was applied to justify the best suitable processing technology for a large-scale pig farm in the Leningrad Region with 17,800 heads of pigs and 54,750 t of pig manure per year. The selected technology included manure separation into fractions, aeration and secondary sedimentation of the liquid fraction and passive composting of the solid fraction. It demonstrated the total amount of nitrogen (N) and phosphorus (P) in the end-products of 278.94 t per year, with the 26% total nutrients loss on all technological stages, and specific capital and operating costs of USD 55.5 per ton of manure produced. The methodology was tested by comparing the calculated data and the data from previous surveys of 15 pig farms in Russia. The differences between the values were found from 0.9 to 12.5% in mass; 2.8 to 13.9% in N content and 1.7 to 9.9% in P content. The developed methodology supports planning the production of the manure-based end-products in a given amount and with target nutrient content, depending on different processing technological solutions, achieving both economic and environmental goals.