Growing vegetables in the circular economy; cultivation of tomatoes on green waste compost and food waste digestate

摘要

The growth in urban population requires solutions that improve the quality of life, especially by proper waste management, reduction of air pollution and C02 emissions, and prevention of food waste. One of the key initiatives introduced and supportedby the EU is circular economy. The main principle is 'to close the loop' by greater re-use and recycling of materials. To meet these challenges, a new solution was developed in the project Food to Waste to Food. In Norwegian climatic conditions, the cultivation of vegetables and mushrooms was performed in a low-energy semi-closed greenhouse insulated with soap bubbles. Presented here are the details in a system called "digeponics", in which biogas digester residues (solid and liquid parts) were used forgrowing medium and fertiliser for cultivation: the solid part was vermicomposted (converting nutrients into available forms) and mixed with green waste compost (to provide structure) into a growing medium for plants - rich in nutrients and beneficial microorganisms. The liquid, high in NHt+, was used in an aerated circulating solution. Through a series of experiments, we present the key measures for rapid conversion of the organic residue into a nutrient rich (e.g., NO3) and aerobic root zone. The mainchallenges were related to management of pH, EC, dissolved oxygen, chloride, nitrate and phosphate, which is discussed here. The input was nothing else than the waste itself. A control treatment based on mineral fertilisers and peat substrate was included. The yield of tomatoes was comparable to the control treatment. The results showed that a chemically balanced conventional system could be substituted by this microbial and waste based system, less chemically balanced, but more natural and sustainable.