New manure-based digestate products: opportunities and implications for soil fertility and carbon sequestration

Anaerobic digestion of manures can contribute to a circular, bio-based economy, through the production of biogas and of the nutrient- and organic matter-rich digestate.

Transportation  of the rich in carbon and nutrients solid fraction of digestate, to areas with nutrient deficiencies, can promote the closure of the nutrient loop in the agricultural sector, increase its potential to subsitute mineral fertilizers and contribute to the sustain of the declining organic carbon levels in soils.

However, further treatment of the solids is needed to increase its economically feasible transportation radius and currently little is known on the derived products´ potential to act as organic amendments and fertilizers.

Therefore, the project aims to use novel manure-digestate solid products acquired within the framework of a closely connected demonstration project.

The effect of the products on soil’s carbon stability and their nutrient release dynamics in soil will be assessed in controlled incubation studies along with their effect on soil microbial activity.

Moreover, pot experiments with ryegrass will be established to compare the fertilizing efficiency of the products to the respected efficiency of mineral fertilizers therefore, the potential to substitute the latter.

The project will synthesize its outcomes in an emergy accounting model as a tool for researchers and policy makers in the circular economy concept.