Life Cycle Assessment of Urban Underground Oyster Mushroom Farming

Sammanfattning: Global food production has been recognized as the single largest driver of environmental degradation and transgression of planetary boundaries. Providing healthy food sustainably to a growing, mostly urban population will require radical changes to the food system. Indoor urban agriculture has been proposed as a promising alternative that reduces the distance between farm and fork, provides fresh quality food shortly after harvest, efficiently uses space by vertical expansion, and enables year-round cultivation protected by weather variations and climate deregulation. The development of indoor urban agriculture has traditionally manifested as verti- cal hydroponic systems cultivating leafy greens, but the interest in urban mushroom farming has lately been rising, both in Sweden and internationally. However, a knowledge gap on the environmental impacts of these systems hampers the possi- bility to develop them sustainably. This study aims to fill this gap by conducting an attributional cradle-to-market life cycle assessment of a theoretical urban under- ground oyster mushroom farm in Stockholm. Per kg packaged and delivered grey oyster mushrooms (Pleurotus ostreatus), the potential environmental impacts were estimated as the following - climate change: 2.45 kg CO2-eq, freshwater eutrophication: 6.76E-04 kg P-eq, fossils: 80 MJ, dissipated water: 3.29 m3 water-eq, and land use: 149 points. For the investigated impact categories the findings suggest that the three main environmental hotspots, in descending order, in general, are the farm’s electricity requirement, especially for fossils and dissipated water, the substrate materials, which is largely contributing to the land use impact, and the PET packaging of the final product, particularly for climate change and freshwater eutrophication. The results indicate that the cooling load for fruiting represents the majority of the farm’s electricity consumption. The spawn and wheat straw are the main contributors to the substrate mixture’s impact, and regarding climate iii change, the transportation by truck of the spawn and wheat straw pellets are im- portant factors. The life cycle of the PET packaging boxes and the PE growing bags have an especially important climate change contribution due to their production, transportation, and waste incineration.  By indicating which processes, energy, and material flows most contribute to urban underground oyster mushroom farming’s environmental impact, this study gives insights on improvement priorities and help steer the sector towards ecologically sustainable development. To guide ecodesign, future studies should explore and assess the environmental implications of different options, such as substrate materials, substrate preparation methods, packaging materials, and the reuse of different urban residues.