Modular systems to foster circular economy in agriculture

It is generally understood that a production process based on circularity aims at creating a closed-loop system that makes the most efficient use of resources while reducing/eliminating waste and negative environmental impacts. For this purpose, it is pivotal to properly define the specific context in which these principles can be effectively applied. We found it useful to introduce the concept of modular system (i.e. a system consisting of separate parts that, when combined, form a complete whole) to facilitate the implementation of circularity principles in agriculture. For example, shifting from diesel-based to biomass-based systems for greenhouse heating has been proven to substantially reduce the heating costs. The combination of greenhouse soilless cultivation, biomass crops grown on marginal lands/degraded soils and efficient energy conversion technology (3 components of the proposed circular system) would allow farmers to substantially reduce the production costs for running the greenhouse (heating/cooling) while restoring the soil fertility. It has also been estimated that CO2 fertilization can shorten plants' growth cycle up to 20 days and improve yield up to 40%. The CO2 generated through the biomass-energy conversion process can be used for greenhouse fertilization, representing another important component of the circular system. Modular sizing of the greenhouse production+biomass for bioenergy combination for a specific environment is critical to efficiently utilize all the CO2 produced for supporting the greenhouse energy requirements, while minimizing the environmental impact and producing additional benefits for the environment.