Short Description of the technology

Composted animal slurries can be a valuable source of soil organic matter and nutrients. However, their low nitrogen-to-phosphorus (N:P) ratio can cause a nutrient imbalance in the soil, leading to P overfertilization and increased risk of its transfer from soil to waterbodies with consequent eutrophication. Moreover, ammonia (NH₃) and greenhouse gases (GHG) emissions occur during both composting and after soil application. UNITO evaluated the effectiveness of acidifying pig slurry with elemental sulphur (S) before mechanical separation and composting of the solid fraction. The acidified solid fraction is stabilized through composting and pelletization, facilitating precise mechanized distribution. A nutrient-corrected pellet has been also produced by adding mineral fertilizers (e.g., calcium and potassium nitrate) to the acidified solid fraction, producing an N:P balanced organic fertilizer for crops. This approach aims to reduce NH₃ and GHG emissions while enhancing nutrient recovery, increasing soil organic carbon (C) stocks, and promoting sustainable manure management.

Innovative Features

This technology integrates acidification with elemental sulfur, effectively lowering slurry pH and converting volatile ammonia into stable ammonium (NH4+), thereby reducing NH₃-N emissions. The production of nutrient-corrected pellets further enhances nutrient management by balancing the N:P ratio, which is often skewed in convectional composted solid fraction. The pelletized form ensures targeted nutrient application, improving nutrient use efficiency. Moreover, acidification reduces GHG emissions during composting, contributing to improved agricultural practices. Additionally, by enhancing soil organic C stocks, the technology improves soil structure, water retention, and long-term fertility.

Type of Contribution

This technology significantly advances sustainable livestock waste management by addressing critical environmental concerns. Acidification with sulfur (1–3 kg per ton of pig slurry) can reduce NH₃ emissions by 35% and GHG emissions by approximately 50%. Additionally, the process enhances nutrient recovery by stabilizing ammonium and optimizing the N:P ratio in the final composted product. The resulting balanced organic amendment supports precision agriculture and promotes efficient nutrient utilization, reducing dependency on synthetic fertilizers and fostering circular economy principles.

Benefits for farmers, the industry, and the environment

For farmers, this technology provides tangible benefits, including improved nutrient management, reduced fertilizer costs, and enhanced soil health, leading to better crop productivity. It also facilitates compliance with increasingly stringent environmental regulations related to emissions and nutrient application. The production of nutrient-balanced pellets presents opportunities for the agricultural industry by creating value-added products and encouraging environmentally responsible practices. On a broader scale, the environmental benefits include significant reductions in ammonia and greenhouse gas emissions, lower risks of phosphorus losses and water contamination, and more efficient use of organic resources. Additionally, adopting this technology can enhance soil carbon sequestration and overall soil health, contributing to climate change mitigation and long-term agricultural sustainability.