How to use residual biomass streams in circular food systems to minimise land use or GHG emissions

Summary

Context: Transitioning to future circular economies and food systems will increase demand for biomass in society. Residual streams, which include food loss, food waste and by-products (e.g., rapeseed meal) from agriculture and food production are a valuable source of biomass in more circular food systems. It is currently unclear if and whether these residual streams should be utilised optimally: as animal feed, composted as organic fertiliser or for anaerobic digestion to produce biogas (methane) and digestate (fertiliser) to minimise environmental impacts from food systems. Objective: Our aim is to understand which residual streams are to be utilised as animal feed, compost or for anaerobic digestion in circular food systems to achieve minimum agricultural land use and greenhouse gas (GHG) emissions under scenarios with different dietary preferences. Methods: Taking the Netherlands as a case study, we employed the FOODSOM model, an iterative linear optimisation model of a circular food system in the Netherlands. FOODSOM minimises agricultural land use or GHG emissions while meeting the dietary requirements of the population. Four scenarios based on two different human diets and two food system objectives (i.e., minimise land use or GHG emissions) were developed. Results & conclusions: Our results show by-products should be fed to livestock when aiming to minimise agricultural land use and GHG emissions, food loss and waste is best fed to livestock when minimising land use, but composted or digested when minimising GHG emissions. The decision to compost or digest food waste depends on whether the GHG emissions from anaerobic digestion are assigned to the food system or the biogas (methane) produced. Significance: Our results provide guidance on how residual streams, including food loss, food waste and by-products can be optimally utilised in future circular food systems to achieve minimal agricultural land use and GHG emissions when meeting dietary requirements.