Two-stage separation and acidification of pig slurry – Nutrient separation efficiency and agronomical implications

Separation of slurries can facilitate the nutrient management on farms through nutrient partitioning between the liquid and the solid fraction. The distribution of nutrients in the slurry fractions depends largely on the type of separator used. The current study assessed the separation efficiency of a two-step separation treatment of pig slurry including in-series a screw press and a centrifuge followed by acidification (to pH 5.9) of the final liquid effluent. The system concentrated 73.8% of the slurry’s Phosphorus (P) content, 52.6% of Total solids (TS) and 14.4% of total Nitrogen to the solid fraction. The apparent N recovery from ryegrass fertilized with the raw slurry and non-acidified liquid fractions was not decreased by the separation treatment. The acidified liquid fraction showed 28% and 9% higher apparent N recovery compared to the raw slurry and the non-acidified liquid effluent from the centrifuge respectively. The biochemical methane production potential (Bo) of the acidified liquid fraction was reduced by 50% and 25%, compared to the non-acidified counterpart and the raw slurry, respectively. The results highlight the potential of a double separation system coupled with acidification of the liquid fraction, to extract P into a solid fraction which can be transported outside the farm, and to increase N utilization from the liquid fraction when this is used as organic fertiliser on or nearby the farm. The study further highlights the potential to reduce CH4 emissions from slurry storage after mechanical separation and acidification of the liquid slurry fraction

Farmers' perceptions on organic fertilisers towards circularity - a case study in Sweden

Adequate treatment of organic manures and digestates from livestock production should reduce environmental impacts and provide well-defined and attractive biofertlisers for a crop production market, which can promote the closure of the nutrient cycle in agriculture. In this sense, a survey was conducted during the autumn of 2021 to investigate Swedish farmers' perspectives on organic fertilisers use. The survey consisted of an online questionnaire, which was distributed broadly in the social media, homepages, different types of networks and at course events in order to reach all types of farms. There were 22 questions focused on current use, reasons for current use and preferences for future use. The analysis of the 99 fully responded surveys, demonstrated that 43% of the respondents think that they will increase their use of organic fertilisers in the coming 5-10 years and 60% think that they will use manure digestate in different forms (both solid and liquid fractions). Soil improvement was the main reason to use organic fertilisers, but there were also preferences for organic fertilisers with fast release of nutrients. The risk of soil compaction was the main reason not to use organic fertilisers and based on the responses, pellets and granulates seem to be more interesting than liquids and solids in general. Animal manures dominate the current use of organic fertilisers in Sweden however, other types of organic waste such as digestate and digestate derived fertilisers seems appealing to Swedish farmers. In conclusion, from this survey with 62% of the respondees in crop production, we found several indications of that there is a potential for increased use of organic fertilisers in Sweden on farms with limited use today. We found an openness, a broad interest and a demand for different types of products of different forms and origin. Since this demand in the end will almost always depend on the price of products in relation to the price of mineral fertilisers, which are fluctuating, we see the need of policy incentives in order to stimulate initiatives for the development towards increased circularity of nutrients

The Implications of Animal Manure Management on Ammonia and Greenhouse Gas Emissions

High livestock densities and the subsequent generation of large quantities of manure, in some areas of the world, generate hotspots of increased environmental risks through ammonia (NH3) and greenhouse gas (methane, CH4; nitrous oxide, N2O) emissions. Livestock production is therefore facing increased pressures from society to comply with environmental legislation, so that systems are managed in a sustainable and environmentally friendly manner. A key solution to minimize or avoid environmental and health concerns associated with manure is to ensure appropriate feeding strategies as well as manure management techniques through the entire manure management chain from animal housing, storage of manure, treatment operations and finally application to soil. An integrated framework is needed to allow practical, cost-effective on-farm strategies to be selected, which will reduce losses and improve resource use efficiencies. In this chapter, we first analyse the contribution of manure management to NH3 and GHG emissions with focus on bovine, pig and poultry manure. We then describe different mitigation options for reducing gaseous emissions along the manure management chain in terms of their efficiency to decrease NH3 and GHG emissions and their applicability. Finally, we present and assess two case studies of integrated manure management strategies to reduce gaseous emissions.info:eu-repo/semantics/publishedVersio