Combining life-cycle assessment and linear programming to optimize social fertilizer costs

This paper focuses on the role of fertilizers within regional nutrient cycles. Bio-based fertilizers can contribute to regional nutrient circularity, but the question remains whether production and consumption of bio-based fertilizers is beneficial to the farmer and the environment. Therefore, both farmers’ private costs and environmental externalities should be taken into account. We formulate a farm-level multi-objective optimization model by considering a range of fertilizers, their costs and the environmental consequences associated with their production and use. The cost-minimization approach is applied to a conceptualized Flemish leek farmer aiming to safeguard nutrient uptake while being constrained by nutrient standards and the availability of on-farm residues. Our results suggest that mineral fertilizers have an important role in the fertilizer mix despite their environmental externalities. Nevertheless, there is also a role for bio-based fertilizers. These results have implications for farmers and policymakers wishing to internalize fertilizer externalities. •An optimization model minimizes social costs of a horticultural fertilizer mix.•The analysis employs life-cycle analysis, cost data and externality valuation.•Usage of mineral fertilizers, pig slurry, compost and crop residues is optimal.•Sensitivity analyses highlight the importance of ammonia emissions.