Abstract
To face the increase of waste production and meet the energy demand of urban areas, municipal waste management systems should be rethought. Innovative solutions such as decentralised small-scale anaerobic digestion could be developed. This work presents the design, operation and performances of a new micro-scale anaerobic digester (AD) developed to degrade food waste (FW) in urban areas i.e. highly compact and with low water and energy demand. To meet these objectives, the new micro-scale AD is a semi-continuous and two-stage process built vertically to take advantage of the gravity to mix and move the digested matter instead of using mechanical devices. The first stage consists in a tubular reactor fed weekly with FW and periodically watered with leachate from the second stage reactor located below the tubular reactor. Results show that AD performances were highly correlated to the efficiency of hydric transfer between the tubular reactor and the leachate tank. Indeed, pH, volatile fatty acids and microbial community analysis showed that the hydrolysis occurred in the tubular reactor, while the methanogenesis step occurred in the leachate tank. Overall, the average methane production was 143 ± 87 NL/kgvs with an average methane content of 44 ± 10% and the operation mode of the process has still to be improved.Graphic
Highlights
From year 2018 to 2050, the urban population of European countries is expected to increase from 74 to 83% of the total population [1]
Weekly average of methane production gradually increased from 151 ± 26 L/kgvs during the 3rd week to 190 ± 26 L/kgvs during the 6th week, which was due to an increase of the solid retention time in the tubular reactor
At the beginning of the 7th week, solid digestate was removed by hand at the bottom of the tubular reactor until enough volume was recovered to load the new batch of food waste (FW)
Summary
From year 2018 to 2050, the urban population of European countries is expected to increase from 74 to 83% of the total population [1]. In order to decrease the cities’ environmental impacts and to contribute to a better resilience of urban areas, waste management systems have to be rethought In this objective, biowaste proximity management with microscale system are expected to led to better involvement of waste producers in the sorting and valorization of their biowaste, with less impacts of collection. Biowaste proximity management with microscale system are expected to led to better involvement of waste producers in the sorting and valorization of their biowaste, with less impacts of collection This new management scale can complete existing treatment equipment for new quarters in growing cities. New decentralized systems based on micro-scale anaerobic digestion (micro-scale AD) technologies could be a solution to locally valorize biowaste, produce energy and provide fertilizer to urban farming
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