Managing anaerobic digestate from food waste in the urban environment: Evaluating the feasibility from an interdisciplinary perspective

Abstract

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.

Process Waters from Hydrothermal Carbonization of Sludge: Characteristics and Possible Valorization Pathways

“…Furthermore, its organic residual content makes it suitable as organic amendment, improving the physical, chemical and biological properties of the soil [ 3 ]. According to the current European legislation, when AD is applied to pre-selected biowastes, digestate can be sent for direct soil application, reducing the needs of chemically produced fertilizers [ 4 ]. Often, various treatment options can be applied both to optimize transport and application conditions, such as solid/liquid separation, composting, drying, thermal concentration, physical–chemical treatment [ 5 ] and pelleting [ 6 ], as well as to treat it in order to reduce the nitrogen content [ 7 ].…”

“…Often, various treatment options can be applied both to optimize transport and application conditions, such as solid/liquid separation, composting, drying, thermal concentration, physical–chemical treatment [ 5 ] and pelleting [ 6 ], as well as to treat it in order to reduce the nitrogen content [ 7 ]. However, the amount of digestate that can be applied to the field is limited according to its nutrient content, its quality and, in some countries, according to the lack of fertile lands [ 4 ]. All these variables represent limiting factors of the application of digestate as organic fertilizer to soils.…”

Pathogen Reduction Potential in Anaerobic Digestion of Organic Fraction of Municipal Solid Waste and Food Waste

“…Nearly 95% of the digestate produced in Europe can be used as an organic fertilizer to replace chemically produced fertilizers [19]. However, fertilization using this type of fertilizer is currently limited due to its quality, nutrient content, possible land contamination, sanitary safety, or even lack of fertile land [19].…”

Valorisation of digestate from biowaste through solid-state fermentation to obtain value added bioproducts: A first approach

“…Digestate is a heterogeneous material produced in large amounts during the anaerobic digestion process (Dahlin et al, 2017;Monlau et al, 2015). Nearly 95% of the digestate produced in Europe can be used as organic fertiliser reducing the needs of for chemically produced fertilizers (Fuldauer et al, 2018;Saveyn & Eder, 2013). Digestate obtained from source selected biowaste is conventionally sent to composting or to direct soil application, however its use is currently limited due to nutrient content, quality of the digestate (Paavola & Rintala, 2008), possible land contamination and, in some countries, the lack of fertile land (Fuldauer et al, 2018).…”

“…Nearly 95% of the digestate produced in Europe can be used as organic fertiliser reducing the needs of for chemically produced fertilizers (Fuldauer et al, 2018;Saveyn & Eder, 2013). Digestate obtained from source selected biowaste is conventionally sent to composting or to direct soil application, however its use is currently limited due to nutrient content, quality of the digestate (Paavola & Rintala, 2008), possible land contamination and, in some countries, the lack of fertile land (Fuldauer et al, 2018). In this sense, a more sustainable approach is proposed by the DECISIVE project (www.decisive2020.eu) in terms of digestate management, considering this waste as a feedstock for further biotransformation through solid-state fermentation in a circular economy context.…”