Optimizing and valorizing the agronomical value of processed animal manure (MANUREVALUE)

What is the agronomic value of processed animal manure? Which processing techniques are the most valuable? And how should we estimate the economic value of these different processing techniques? Crude animal manure has frequently a suboptimal nutrient composition as fertilizer in agriculture and horticulture. N/P and N/K ratios are usually less adapted to optimal fertilization of a crop, and many animal manure types contain low levels of effective organic matter per unit of N and K. Several processing techniques are available however. The objective of this research is to draw up an inventory of these techniques and to test the value of the processed products. ILVO cooperates in this project with Ghent University, Inagro, Soil Service of Belgium (BDB), Hooibeekhoeve, biogas-e and the Flemish Coordination Centre for Manure Processing (VCM).

VCM makes an assessment of (i) the available low-tech processing techniques such as blending several animal manure types, acidification techniques, extensive composting and (ii) high-tech techniques such as electrolysis, membrane filtration, and others. A few manure processing products are selected to determine their N mineralization capacity in a N incubation experiment, where 170 kg total N/ha is added. The mineral N content (N-NO3 and N-NH4+) of the soil in this incubation experiment is measured every two weeks, to determine the percentage of added N that has mineralized, to determine the N working coefficient. Based on a pot experiment in the greenhouse with annual ryegrass, the P and K working coefficients are measured by determining the dry matter crop yield and P and K uptake. In this experiment a P and K deficient soil is used, and N is added in excess to prevent N deficiency. The C mineralization of the processed products is determined in a C mineralization incubation experiment, where the CO2 emission is monitored. From this  CO2 emission, we calculate the amount of effective organic carbon in the products that contribute to the soil organic carbon content. Inagro tests these products in field trials. Ghent University characterizes the products, emissions to the environment, and the economic feasibility of the processing techniques and the processed products.

Many farmers have already invested or plan to invest in the near future in processing techniques for crude animal manure. Based on this project, we can provide objective information about the agronomical and economical potential of the processed manure. Information on nutrient composition, working coefficients and potential to contribute to the soil organic carbon will be available. The results of this project will also be useful for crop husbandry, fertilization strategies and soil quality. Our results are also of fundamental interest to policymakers, who need more references on the working coefficients and agronomical value of these products. ILVO conducts the incubation and pot experiments in conditions representative for the Flemish farmer.