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The UK is facing tremendous challenges in tackling food waste diversion from landfill. Whilst much effort has been made to prevent food waste, there is still a lack of attention and strategic approach in dealing with resource recovery and valorisation of food waste. This paper presents a systematic framework for sustainable organic waste management and valorisation in the UK through (i) review of current policy framework; (ii) analysis of resource recovery potential from food waste at national, community and organisational levels; (iii) proposition of alternative waste management strategies; and (iv) examination of challenges and opportunities with respect to economic, environment and social dimensions of sustainability of waste management strategies. The paper explores valorisation of source-segregated food waste and mixed waste from the supermarket and households into electricity and transportation fuels, through partially and completely decentralised configurations using anaerobic digestion and gasification technologies. This study demonstrates a potential for reducing the cost of electricity and greenhouse gas emissions of one supermarket store by 12% when adopting partially decentralised food waste anaerobic digestion strategy, and full substitution of fossil fuel based electricity with net surplus renewable electricity generation through complete decentralisation of mixed waste gasification. Therefore, a more integrated, circular and advanced technological approach in waste management should be undertaken as it can lead to a wider range of socio-economic and environmental advantages to the local community, highly essential in the UK. Image 1 • Valorisation of waste closer to the source promotes resource circularity. • A synergistic approach is robust in addressing challenges in waste management. • Technology and configuration determine the viability of valorisation strategies. • Decentralised waste management enhances community participation. • A supportive fiscal incentive scheme promotes uptake of waste valorisation. [ABSTRACT FROM AUTHOR]

The transition to a circular economy relies on systems that facilitate waste recovery and recirculation of resources. These systems are based on certain enabling technologies. The aim of this paper is to explain how socio-economic structures influence the diffusion of such technologies. It applies a framework built on societal embedding and varieties of capitalism to compare the diffusion of anaerobic digestion (AD) in Sweden in northern Europe and Paraná in southern Brazil. Both Sweden and Paraná have experienced accelerated diffusion of AD, but there are significant differences in the respective diffusion patterns. The comparative analysis points to a tradeoff between system complexity and speed of diffusion. It illustrates how AD can be presented as a solution to various problems, and it further shows how the specific problems that gain attention shape diffusion patterns. By showing how socio-economic structures influence the appointment of problem owners, their agency, and legitimate forms of institutional support, the analysis demonstrates how economic systems condition technology diffusion. • The paper compares the diffusion of anaerobic digestion in Sweden and Paraná. • It shows how socio-economic structures have shaped diffusion patterns. • There is to a trade-off between sociotechnical system complexity and speed of diffusion. • Economic systems condition the diffusion of key technologies for a circular economy. • Analyses of recirculation potential must consider socio-economic structures. [ABSTRACT FROM AUTHOR]

Biogas production and use can represent a win-win strategy providing multiple opportunities to mitigate the emission of greenhouse gases responsible for climate change, while offering a range of important social, environmental and economic benefits. Nevertheless, as for other bioenergy pathways, biogas sustainability needs to be carefully assessed and continuously monitored in light of the specific geographic and temporal context in which it performs. This paper aims to provide a comprehensive review on the sustainability assessment of domestic production and use of biogas in Italy, with a focus on the environmental dimension of the sustainability. Furthermore, it elaborates the results of the review to perform an ex-novo sustainability assessment of biogas pathway at national level, through the methodology developed by the Global Bioenergy Partnership. The biogas value chain in Italy can play a positive role to foster the transition towards an ecological and circular economy. This paper highlights both weaknesses and strengths of the biogas value chain in Italy and points out existing differences, in relation to the sustainability of the value chain, between various geographical areas of the country. The outcomes of this study could inform, both at national and international scale, the drawing of tailor-made policies and measures to reduce biogas-related potential risks of environmental impacts, as well as to support the replication and scaling up of successful management practices. Furthermore, they could serve as a baseline for the future monitoring of the sector. Ultimately, the paper reports the key difficulties encountered in the implementation of the GBEP methodology and the solutions adopted to overcome them. [Display omitted] • Three-quarters (75.4%) of the Italian biogas production takes place in the Po river valley, one-third comes from Lombardy. • Maize silage and livestock manure are the most common feedstocks in Italian biogas plants. • Roughly 80 k tons of nitrogen contained in livestock manure were treated by biogas plant in Italy in 2016. • The main source of GHG emissions along the biogas pathway in Italy lies in the cultivation of dedicated bioenergy crops. • Water shortage hampers the development of the biogas sector in southern Italy, restricting the cultivation of energy crops. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of food waste within urban areas can generate decentralised renewable energy and support community enterprise activities, thereby contributing to closing the waste-energy-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 L 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. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of bioplastics' wastes may represent a valuable disposal strategy for these important substitutes for plastics, in order to reduce their leakage into the environment and to produce bioenergy in the form of biomethane, contributing positively to the sustainability of the entire bioplastics' life chain. Only lab-scale data about bioplastics' anaerobic degradability and biomethane production have been produced until now, using approaches far from full-scale conditions. This paper presents a novel approach in studying the potential of bioplastics to produce biomethane because a pioneering methodology was adopted, allowing acquisition of full-scale data that can be useful to further attest environmental and economic sustainability in recovering bioplastics' wastes. A simple and replicable experimental approach was proposed to studying bioplastic degradability during anaerobic digestion, which consisted of placing the bioplastics into a full-scale digester within perforated steel boxes. Three different bioplastics items (one starch-based and two polylactic-acid based) were co-digested with organic wastes in a real anaerobic digestion plant using the real process parameters (thermophilic temperature for 30 days of hydraulic retention time followed by 30 days of mesophilic maturation). The experiments were replicated at laboratory-scale to evaluate the potential for biomethane recovery from bioplastics degradation. Laboratory-scale data did not differ from the data coming from the full-scale experiment, i.e., bioplastic degradation was not affected by the reactor volume. Bioplastics showed an average degradation of 27 ± 5% on a weight basis and a different degradation mechanism for the two types studied was found through Fourier Transform-InfraRed spectroscopy (FTIR) analysis. Starch-based bioplastics showed a quick consumption of the starch component, followed by a slow degradation of the polyester fraction. Polylactic acid bioplastics were degraded without chemical changes to their composition. In both laboratory-scale and full-scale experiments, temperature was a key parameter affecting bioplastics' degradation, i.e., thermophilic temperatures were needed to obtain a significant degradation. Biomethane potential determination of the bioplastics (135 ± 23 NLCH 4 kg Volatile Solids−1 as average at the end of the thermophilic digestion) proved that anaerobic digestion of bioplastics may be a sustainable approach, reducing bioplastic leakage and producing bioenergy (biogas), respecting Circular Economy principles. Anaerobic digestion may represent a valorisation treatment for bioplastics' wastes contributing positively to the sustainability of the entire bioplastics' life chain. [Display omitted] • First assessment of bioplastics' anaerobic degradation using a full-scale approach. • Starch-based and polylactic acid-based bioplastics degrade differently during AD. • Bioplastics' anaerobic degradation may enhance biomethane production from AD plant. • AD of bioplastics can avoid their leakage into natural environments. [ABSTRACT FROM AUTHOR]

This paper assesses the potential energy and environmental impacts of an anaerobic digester coupled with a combined heat and power plant powered with bio-wastes from the agri-food sector. The analysis is carried out through the Life Cycle Assessment methodology following a "cradle-to-grave" approach and is based mostly on primary data. The anaerobic digester - combined heat and power plant is analysed considering a twofold perspective: one more energy – oriented where the main function of the system is to generate renewable electricity and a waste – oriented one in which the main function is treating bio-wastes. In addition, the environmental indirect effects related to potential competitive uses of bio-wastes are evaluated. Biomass transport and the electricity consumed during the operation phase make the largest contribution (higher than 60%) to almost all the impact categories examined. The comparison with the electricity eco-profile from the national grid and with a composting facility highlights that the anaerobic digester - combined heat and power system may reach better energy and environmental performances for both the electricity generation and bio-waste management. Image 1 • A life cycle assessment of an anaerobic digester coupled with a combined heat and power plant is performed. • The plant is analysed through the perspectives of energy production and waste treatment. • Biomass transport and electricity consumed during the operation phase make the largest impact contribution. • The examined system can be a sustainable solution for both electricity generation and bio-waste management. • Indirect effects in competitive economic sectors can offset the environmental benefits of the examined system. [ABSTRACT FROM AUTHOR]

Biogas production is one of the most promising pathways toward fully utilizing green energy within a circular economy. The anaerobic digestion process is the industry standard technology for biogas production due to its lowered energy consumption and its reliance on microbiology. Even in such an environmental-friendly process, liquid digestate is still produced from the remains of digested bio-feedstock and will require treatment. With unsuitable treatment procedure for liquid digestate, the mass of bio-feedstock can potentially escape the circular supply chain within the economy. This paper recommends the implementation of evaporator systems to provide a sustainable liquid digestate treating mechanism within the economy. Studied evaporator systems are represented by vacuum evaporation in combination with ammonia scrubber, stripping and reverse osmosis. Nevertheless, complex multi-dimensional decisions should be made by stakeholders before implementing such systems. Our work utilizes a novel techno-economics model to study the techno-economics robustness in implementing recent state-of-art vacuum evaporation systems with exploitation of waste heat from combined heat and power (CHP) units in biogas plants (BGP). To take into the account the stochasticity of the real world and robustness of the analysis, we used the Monte-Carlo simulation technique to generate more than 20,000 of different possibilities for the implementation of the evaporation system. Favourable decision pathways are then selected using a novel methodology which utilizes the artificial neural network and a hyper-optimized decision tree classifier. Two pathways that give the highest probability of providing a fast payback period are identified. Descriptive statistics are also used to analyse the distributions of decision parameters that lead to success in implementing the evaporator system. The results highlighted that integration of evaporation system are favourable when transport costs and incentives for CHP units are large and while feed-in tariffs for electricity production and specific investment costs are low. The result of this work is expected to pave the way for BGP stakeholders and decision makers in implementing liquid digestate treating technologies within the currently existing infrastructure. Image 102 • Techno-economic assessment for integrating evaporators in biogas plants. • Rigorous Monte Carlo simulations were carried out for liquid digestate modelling. • Artificial Neural Network is used to prioritize variables in decision making. • Decision trees are used to search for favourable decision pathways for the industry. • Having CHP bonus would improve the scenario for industrial digestate thickening. [ABSTRACT FROM AUTHOR]