An optimization model minimizing costs of fertilizer application in Flemish horticulture

The majority of today's fertilizers are based on mineral resources and fossil fuels. Among other factors, geopolitical sensitivities and rising fertilizer demand contribute to high and volatile prices. To reduce our dependency on non-renewable resources, valuable bio-based fertilizer components can be recovered through valorization of organic waste streams. However, from a farmer's perspective, an optimization problem arises: the farmer wants to minimize costs while safeguarding crop nutrient uptake. Optimization research in the fertilizer domain focuses on scheduling fertilizer application or minimizing manure management costs. The model developed in this paper intends to minimize fertilizer costs for an individual vegetable farmer by considering the possibility of bio-based fertilizer prosumption through composting and anaerobic digestion as well as leaving crop residues on the field. In a Linear Programming model, these options are compared to purchasing mineral fertilizer, commercial compost or pig slurry. In addition, a distinction is made between different business models. Sensitivity analysis is carried out with respect to changing cost parameters. The results confirm that it is not optimal for a Flemish vegetable farmer to fulfil nutrient needs solely with bio-based fertilizer. Nevertheless, the study shows that it can be interesting to consider value chains involving regional cooperation.