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Anaerobic digestion of food waste within urban areas can generate decentralised renewable energy, support community enterprise activities and thereby contribute to closing the wasteenergy-food loop. However, widespread uptake of small-scale, urban anaerobic digestion networks is limited by economic costs and the safe disposal of surplus digestate. This paper uses an interdisciplinary approach to assess the feasibility of anaerobic digestate management through the installation of hydroponics or algae cultivation systems, based on a case study of a micro anaerobic digestion system in London, England. Results show that installing a dewatering sifter together with a hydroponics system is a technically and economically feasible option for digestate enhancement in the urban environment. Its installation is, however, not currently justified for the system under consideration due to cost, regulatory, spatial, and contextual constraints identified using actor-network analysis. Nevertheless, if regulatory and wider contextual issues are accommodated, and more than 30 litres of digestate are produced daily, a dewatering and vertical hydroponic system could result in a profit of approximately £100,000 over 10 years. While the microalgal system was also able to upgrade digestate, at present productivity is too low and the capital cost of photobioreactor technology is prohibitively expensive. This underlines the need for technical improvements and low-cost enhancement options to achieve justifiable paybacks until regulatory reforms and the wider economic situation are more favourable to anaerobic digestion treatment within cities.

Targets agreed to in Paris in 2015 aim to limit global warming to 'well below 2°C and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels'. Despite the far-reaching consequences of this multi-lateral climate change mitigation strategy, the implications for global river flows remain unclear. Here we estimate the impacts of 1.5°C versus 2.0°C mitigation scenarios on peak flows by using daily river flow data from a multi-model ensemble which follows the HAPPI Protocol (that is specifically designed to simulate these temperature targets). We find agreement between models with regard to changing risk of river flow extremes. Moreover, we find that the response at 2.0°C is not a uniform extension of the response at 1.5°, suggesting a non-linear global response of peak flows to the two mitigation levels. Yet committing to the 2.0°C warming target, rather than 1.5°C, is projected to lead to an increase in the frequency of occurrence of extreme flows in several large catchments. In the most affected areas, predominantly in South Asia, while regionspecific features such as aerosol loads may determine precipitation patterns, we estimate that under our 1.5°C scenario the historical 1-in-100 year flow occurs with a frequency of 1-in-25 years. At 2.0°C, similar increases are observed in several global regions. These shifts are also accompanied by changes in the duration of rainy seasons which influence the occurrence of high flows.