Composting: the solution to closing cycles and improving soil quality in the transition towards a bio-economy?

Europe is strongly encouraging the development of a bio-economy, which produces renewable biological resources and converts them into valuable products ranging from food to bioenergy. To maximize the efficient exploitation of the available biomass, the biomass-cascade principle is often put forward. This entails organizing the processing of biomass to first produce the application with the highest socio-economic value (food and feed) with usable by-products that can cascade down as feedstock for other applications (bio-based products and bio-energy).
With the bio-economy expected to grow exponentially, the demand for biomass will significantly increase. This, given the limited land availability, implies that higher agricultural yields will have to be pursued. Furthermore, crop residues that now remain on the field, will increasingly be removed to be used as a feedstock in the biomass-cascade, reducing organic matter and nutrients in the soil. This removal leads to reduced soil quality and fertility, which is incompatible with the need for higher yields. Remedying this decreased soil quality with more fertilizers is a suboptimal solution, as they are produced with finite resources and require a high energy input, which does not match the sustainable vision of the bio-economy. Therefore, sustainably maintaining soil quality and fertility is an important, yet underexposed, challenge in the transition towards the bio-economy.
Compost has the potential to be a sustainable soil improver in agriculture within the bio-economy. This because the composting process can be integrated into the biomass-cascade principle, as it uses biomass that has no or no further application. Also, it has a sustainable, low impact production process which requires little energy input. Furthermore, compost provides nutrients and improves organic matter content. However, despite the well-established beneficial aspects of compost on soil quality and fertility, it is currently not often used in agriculture. Therefore, the aim of this paper is to uncover what the inducing, and more importantly, the hindering mechanisms are for compost-use in agriculture. To identify these mechanism, we combined elements from the Sociotechnical Systems approach and the Technological Innovation Systems approach to analyze a combination of quantitative and qualitative data that was gathered in Flanders (Northern Belgium) using a mixed-methods approach. Furthermore, we analyzed the economic feasibility of three promising production methods for agricultural grade compost. Based on these outcomes the general feasibility of compost applied in agriculture within the bio-economy is discussed and a number of (policy) recommendations are formulated.