International audienceAs compost use in agriculture increases, there is an urgent need to evaluate the specific environmental benefits and impacts as compared with other types of fertilizers and soil amendments. While the environmental impacts associated with compost production have been successfully assessed in previous studies, the assessment of the benefits of compost on plant and soil has been only partially included in few published works. In the present study, we reviewed the recent progresses made in the quantification of the positive effects associated to biowaste compost use on land by using life cycle assessment (LCA). A total of nine environmental benefits were identified in an extensive literature review and quantitative figures for each benefit were drawn and classified into short-, mid-, and long-term. The major findings are the following: (1) for nutrient supply and carbon sequestration, the review showed that both quantification and impact assessment could be performed, meaning that these two benefits should be regularly included in LCA studies. (2) For pest and disease suppression, soil workability, biodiversity, crop nutritional quality, and crop yield, although the benefits were proved, quantitative figures could not be provided, either because of lack of data or because the benefits were highly variable and dependent on specific local conditions. (3) The benefits on soil erosion and soil moisture could be quantitatively addressed, but suitable impact assessment methodologies were not available. (4) Weed suppression was not proved. Different research efforts are required for a full assessment of the benefits, apart from nutrient supply and carbon sequestration; additional impact categories—dealing with phosphorus resources, biodiversity, soil losses, and water depletion—may be needed for a comprehensive assessment of compost application. Several of the natural mechanisms identified and the LCA procedures discussed in the paper could be extensible to other organic fertilizers and compost from other feedstocks

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Vertical farming is emerging as an effective measure to grow food in buildings and can increase food production in urban areas in a more sustainable manner. This study presents a comprehensive environmental assessment of food production in an integrated rooftop greenhouse (i-RTG)-an innovative vertical farm consisting of a rooftop greenhouse connected to a building-and considers rainwater, residual heat (energy), residual air (CO 2) and food from an industrial ecology perspective. This synergistic connection preserves resources and improves conditions in the greenhouse and the building. The goal of the study is to show the feasibility of the system and to calculate the environmental impacts from its whole life cycle, from infrastructure to end of life, by comparing these impacts with those of conventional production. The results show that the system is feasible and produced 30.2 kg/m 2 of tomato over 15.5 months. The synergy with the building allows the cultivation of winter-fall crops without supplying heating and maintained an average temperature 8 °C higher than that outdoors. Moreover, rainwater was used to irrigate the crops, reducing consumption from the water supply network by 80-90%. The environmental assessment showed that the operation of the i-RTG has more impacts than the infrastructure due to the use of fertilisers, which account for 25% of the impacts in four of the six impact categories studied. Regarding the infrastructure, the greenhouse structure and rainwater harvesting system of the building have substantial environmental impacts (over 30% in four of the six impact categories). Comparison with a conventional greenhouse demonstrates that the i-RTG has a better environmental performance, showing between 50 and 75% lower impacts in five of the six impact categories (for instance, 0.58 kg of CO 2 equivalent per kg of tomato vs. 1.7 kg), mainly due to the reduced packaging and transport requirements. From this study, it was concluded that optimisation of the amount of infrastructure material and management of the operation could lead to even better environmental performance in future i-RTG projects.