Prospects for Increased Energy Recovery from Horse Manure—A Case Study of Management Practices, Environmental Impact and Costs

How Can Biodigesters Help Drive the Circular Economy? An Analysis Based on the SWOT Matrix and Case Studies

The use of biodigesters and the circular economy (CE) has been gaining attention in recent years. Both biodigesters and CE have the potential to minimize negative impacts—not only environmental, but also economic and social. However, little attention has been paid to the relationship between biodigesters and CE. Therefore, the objective of this paper is to identify and analyze the implications of the use of biodigesters in the light of a CE concept. To do this, a SWOT matrix was developed based on the opinion of experts and two case studies were conducted in companies operating in different sectors in Brazil. The results showed that the use of biodigesters can drive CE through biogas, which is a renewable energy source, closing the cycle of organic materials, increasing the economic power of companies and small producers, improving basic sanitation in remote areas, and stimulating industrial symbiosis. However, this study identified barriers in the use of biodigesters in the context of CE, such as lack of government incentives and composting being shown to be more cost-effective than the use of biodigesters for the treatment of solid waste.

Assessment of a full-scale solid-state anaerobic co-digestion: A multi-component substrate analysis by using ORWARE

Long-term sustainable biogas production requires different raw material alternatives, especially when reducing the most desirable organic substrate, food waste, which has been set as a goal in the 2030 Agenda. In Sweden, horse manure (HM) is generated in large quantities, and due to its physical and chemical characteristics, it has the potential to be used as a raw material to produce biogas through anaerobic digestion (AD). In order to investigate the challenges that HM digestion can impose in terms of methane yield and/or digestate quality, the modified ORganic WAste REsearch (ORWARE) AD model was applied. The aim was to study the effects of different substrates and combinations of these on the AD process during a full-scale solid-state (SS)-AD. In this sense, the model allows for the analysis of the digestion process of multicomponent substrates at the element level. The simulation results suggested that the replacement of green waste (GW) by HM with wood chips as bedding material gave the best improvement in terms of energy turnover; the liquid fraction of the digestate of this mixture of substrates presented the highest concentration in all the nutrients analyzed, specifically in total carbon-biological and phosphorus. The nutrient concentrations in the digestate from the aforementioned scenario are in line with the SPCR120 certification.

Sustainable Agri-Food Processes and Circular Economy Pathways in a Life Cycle Perspective: State of the Art of Applicative Research

This study aims at providing a systematic and critical review on the state of the art of life cycle applications from the circular economy point of view. In particular, the main objective is to understand how researchers adopt life cycle approaches for the measurement of the empirical circular pathways of agri-food systems along with the overall lifespan. To perform the literature review, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was considered to conduct a review by qualitative synthesis. Specifically, an evaluation matrix has been set up to gather and synthesize research evidence, by classifying papers according to several integrated criteria. The literature search was carried out employing scientific databases. The findings highlight that 52 case studies out of 84 (62% of the total) use stand-alone life cycle assessment (LCA) to evaluate the benefits/impacts of circular economy (CE) strategies. In contrast, only eight studies (9.5%) deal with the life cycle costing (LCC) approach combined with other analyses while no paper deals with the social life cycle assessment (S-LCA) methodology. Global warming potential, eutrophication (for marine, freshwater, and terrestrial ecosystems), human toxicity, and ecotoxicity results are the most common LCA indicators applied. Only a few articles deal with the CE assessment through specific indicators. We argue that experts in life cycle methodologies must strive to adopt some key elements to ensure that the results obtained fit perfectly with the measurements of circularity and that these can even be largely based on a common basis.

A Review of Waste Management Decision Support Tools and Their Ability to Assess Circular Biowaste Management Systems

The circular economy concept offers a number of solutions to increasing amounts of biowaste and resource scarcity by valorising biowaste. However, it is necessary to consistently address the environmental benefits and impacts of circular biowaste management systems (CBWMS). Various decision support tools (DST) for environmental assessment of waste management systems (WMS) exist. This study provides a review of life cycle assessment based WMS-DSTs. Twenty-five WMS-DSTs were identified and analysed through a shortlisting procedure. Eight tools were shortlisted for the assessment of their applicability to deliver sustainability assessment of CBWMS. It was found that six tools model key properties that are necessary for assessing the environmental sustainability of CBWMSs, including waste-specific modelling of gaseous emissions, biogas generation or bioproduct composition. However, only two tools consider both waste-specific heavy metals content in bioproducts and the associated implications when applied on soil. Most of the shortlisted tools are flexible to simulate new technologies involved in CBWMS. Nevertheless, only two tools allow importing directly new background data, which is important when modelling substitution of new bioproducts developed in emerging biowaste refineries.

Global Warming and Acidification Potential Assessment of a Collective Manure Management System for Bioenergy Production and Nitrogen Removal in Northern Italy

Collective manure processing facilities to reduce nutrient loads and produce renewable energy are often proposed as feasible solutions in intensive livestock production areas. However, the transferring of effluents from farms to the treatment plant and back to farms, as well as the treatment operations themselves, must be carefully evaluated to assure the environmental sustainability of the solution. This study evaluated the global warming potential (GWP) and acidification potential (AP) of a collective treatment plant for bioenergy production and nitrogen removal as an alternative strategy to conventional on-farm manure management systems. Two manure management scenarios were compared: manure management on individual farms and management by a collective treatment plant. Data were collected at a collective processing plant and at the individual farms of the consortium to estimate emissions of CO2, CH4, N2O, NOx, NH3 and SO2. The plant receives manure from 21 livestock production units, treating 660 tonnes day−1 of manure. The GWP and AP indicators were calculated to evaluate the potential impact of the two management solutions. The collective solution reduced both GWP (−52%) and AP (−43%) compared to manure management separately by each farm. Further improvement might be obtained in both indicators by introducing mitigation techniques in farm manure storage and manure application to soil.

The Sustainability of Romanian SMEs and Their Involvement in the Circular Economy

Sustainability involves extending the relational framework of SMEs outside the sphere of economic activity by justifying and legitimizing actions with a social impact on the environment. Links with the circular economy are achieved through the economic and environmental dimensions and through corporate social responsibility as a component of sustainable development. The main purpose of the paper was to determine the level of involvement of Romanian SMEs in activities related to the circular economy. The sample survey conducted among SME managers offered the advantage of collecting a large amount of direct information on the activities undertaken, the size of the investments and the nature of the funding sources used over the last five years. In this descriptive research, the process of setting up a representative sample of 384 enterprises was carried out by random sampling. The major contributions of the research project are to outline the contribution of Romanian SMEs to the development of a sustainable economy through their involvement in specific activities, the size of the investments made, and the level of participation of representatives of the enterprises in courses in order to identify new sources of financing and positive solutions in order to implement the principles of the circular economy.