Biogas production from manure is of particular value in regard of lowering greenhouse gas emissions and enhancing nutrient re-circulation. However, the relatively low energy content and the ...characteristics of manure often result in low degradation efficiency, and the development of operating strategies is required to improve the biogas yield and the economic benefits. In this study, the potential to enhance the performance of two full-scale biogas plants operating with cattle manure, in mono-digestion or combined with poultry manure, was investigated. Four continuously fed laboratory-scale reactors were operated in sets of two, in which the temperature in one reactor in each set was increased from 37–42°C to 52°C. The potential to increase the capacity was thereafter assessed by increasing the organic loading rate (OLR), from ca 3 to 5 kg volatile solids (VS)/ m
3
and day. The processes were evaluated with both chemical and microbiological parameters, and in addition, the residual methane potential (RMP) was measured to evaluate the risk of increased methane emissions from the digestate. The results showed that both processes could be changed from mesophilic to themophilic temperature without major problems and with a similar shift in the microbial community profile to a typical thermophilic community, e.g., an increase in the relative abundance of the phylum Firmicutes. However, the temperature increase in the reactor co-digesting cattle and poultry manure caused a slight accumulation of fatty acids (2 g/l) and reduced the specific methane production, most likely due to ammonia inhibition (0.4–0.7 g NH
3
/l). Still, during operation at higher OLR, thermophilic as compared to mesophilic temperature slightly increased the methane yield and specific methane production, in both investigated processes. However, the higher OLR decreased the overall degree of degradation in all processes, and this showed a positive correlation with increased RMP values. Chemical analyses suggested that high RMP values (40–98 Nml gVS
−1
) were related to the degradation of cellulose, hemicellulose, and volatile fatty acid enriched in the digestate. Conclusively, increased temperature and load can increase the methane yield from manure but can result in less efficient degradation and increased risks for methane emissions during storage and handling of the digestate.
Cattle manure has a low energy content and high fibre and water content, limiting its value for biogas production. Co‐digestion with a more energy‐dense material can improve the output, but the ...co‐substrate composition that gives the best results in terms of degree of degradation, gas production and digestate quality has not yet been identified. This study examined the effects of carbohydrate, protein and fat as co‐substrates for biogas production from cattle manure. Laboratory‐scale semi‐continuous mesophilic reactors were operated with manure in mono‐digestion or in co‐digestion with egg albumin, rapeseed oil, potato starch or a mixture of these, and chemical and microbiological parameters were analysed. The results showed increased gas yield for all co‐digestion reactors, but only the reactor supplemented with rapeseed oil showed synergistic effects on methane yield. The reactor receiving potato starch indicated improved fibre degradation, suggesting a priming effect by the easily accessible carbon. Both these reactors showed increased species richness and enrichment of key microbial species, such as fat‐degrading Syntrophomonadaceae and families known to include cellulolytic bacteria. The addition of albumin promoted enrichment of known ammonia‐tolerant syntrophic acetate‐ and potential propionate‐degrading bacteria, but still caused slight process inhibition and less efficient overall degradation of organic matter in general, and of cellulose in particular.
The study investigated co‐digestion of cattle manure with different categories of co substrates, e.g. starch, albumin, rapeseed oil or a mix of these. The processes were evaluated using both chemical parameters and analysis of microbial communities. Results showed clear correlations between process efficiency and the applied co‐substrates, and enrichment key microbial taxa.
Food systems are central to global sustainability, while being complex systems where places and people are intertwined over large distances and at different scales. Transformations towards ...sustainable food systems have been called for in both research and policy, and Sweden and the European Union have declared high ambitions to act as global leaders in these transformations. While food production in Sweden and the European Union is often portrayed as largely sustainable in a global context, the region is highly dependent on food imports, with relatively large environmental footprints globally. This thesis aims to explore transformative pathways towards sustainability, with a particular focus on sustainable food systems, in a Swedish and European Union context. The thesis specifically studies the following research questions: (1) What constitutes transformations towards sustainability, and in particular sustainable food systems, from the perspectives of Swedish stakeholders, including food system practitioners, and European Union policy frameworks? (2) What roles, responsibilities, and agency do Swedish stakeholders, including food system practitioners and European Union policy frameworks, attribute to different actors? (3) How can interconnections and accountability in global food systems be understood and governed in light of societal transformations towards sustainability? (4) What are the implications for transformative pathways towards sustainability? The thesis builds on four papers that use focus group methodology (PI and PII), involving Swedish stakeholders, including food-system practitioners, analyses of European Green Deal policies (PII and PIII), and quantitative investigation of phosphorus fertiliser use in Brazilian soybean production and related biodiversity impacts (PIV). Four overarching conclusions are drawn from the findings: (I) Shared goals and consensus are emphasised as essential, while a diversity of transformative pathways and understandings of challenges and priorities needs to be recognised, with attention being paid to how specific choices might include and exclude pathways and actors. (II) Emerging shifts in how food is valued open up opportunities for transformative change in which the ‘true’ cost of food is acknowledged, alongside a recognition of non-economic values of food, which presupposes alignment at the practical, political, and personal levels. (III) The identified pathways comprise public accountability regimes, incentives for more sustainable consumption, regulations to reduce resource use and impacts of food production. (IV) The attribution of accountability to trading operators in the accountability regime proposed by the European Union highlights an extended focus from food production and consumption towards regulating flows and intermediate actors in food systems.
Global demand for food, including rising consumption of meat and dairy products, is increasing pressure on the environment and natural resources, often in locations distant from points of ...consumption. To identify and quantify consumer driven impacts and the components of the supply chain where sustainability interventions will be most effective, spatially explicit consumption-linked indicators that encompass environmental risks are required. Large amounts of phosphorus fertilizers are used in Brazilian soybean cultivation, which potentially cause eutrophication and impact freshwater species. We use a sub-national trade model to develop a spatially explicit approach for assessing commodity-driven phosphorus fertilizer use and its potential impact on biodiversity linked to four key consumers. The use of phosphorus for embedded consumption per capita of Brazilian soybean in China, the EU, the UK, and Sweden are estimated at municipal level and combined with metrics that influence losses of phosphorus to create a normalised relative risk index. The relative risk index is presented in geospatial visualisations to explore geographical patterns of risk to freshwater biodiversity and make the link between consumer and producer countries less obscure. The results indicate high phosphorus-linked species risk in municipalities within Mato Grosso, Rio Grande do Sul, Paraná, and Goiás. Sweden and the UK generate the highest relative risk and the geographical patterns of risk differ between the investigated consuming countries, showing that smaller countries can have relatively large impacts at a spatially explicit scale. In the Amazon biome, risk of nutrient losses and biodiversity are relatively high, creating concerns as soybean production is expanding into the area. The results and methodological approach can contribute to understanding of accountability, agency, and increased transparency for the governance of global supply chains, necessary for enabling transformations towards sustainable food systems.
•Phosphorus use in Brazil linked to municipal commodity-driven soybean production.•Phosphorus loss risk and risk of impact on biodiversity is assessed.•Sourcing patterns of EU, UK, Sweden, and China generate different biodiversity risk.•Supply chain transparency, accountability, and decision support for sustainability.
This paper explores the potentials and limitations of transdisciplinary research on sustainability issues characterized by extensive uncertainty and complexity. Transdisciplinary approaches that ...support the co-creation of knowledge in collaboration between science and society are advocated in research that aims to explore pathways for societal transformations towards sustainability. However, there is limited research on how co-creation research plays out in practice and what are its implications, in particular with regards to how data collection and analysis can be developed to increase the quality and reliability of the research, and to the roles that researchers themselves play in shaping the research. This paper makes two contributions: First, it offers insight into the design and implementation of co-creation endeavors based on scholarly literature as well as experiences from a research program that seeks to support foresight capacity for sustainable development under geopolitical uncertainties. Second, the paper elaborates methodological support for co-creation research by highlighting the potential of co-dissemination for transdisciplinarity and arguing for a systematic approach to reflection and self-reflexivity. Specifically, the paper reflects on experiences from the ongoing Mistra Geopolitics research program, which explores the intersections between geopolitics and sustainable development, and where co-creation has been at the core since the start of the program. We explore three stages in transdisciplinary research: (i) co-design of the research agenda, (ii) co-production of knowledge, and (iii) co-dissemination. Specifically, we examine the role of non-academic partners, the role of knowledge brokers and facilitation, and the need for flexibility, adaptability and reflexivity throughout the process.
•Co-creation can support foresight capacity and identification of new challenges.•Flexibility, adaptability and reflexivity are key to transdisciplinary projects.•Co-dissemination can make a relevant contribution in a transdisciplinary program.•Critical assessments should be an integrated part of co-creation processes.
Biogas from agricultural waste streams represents an important way to produce fossil-free energy, allow nutrient recycling and reduce greenhouse gas emissions. However, biogas production from ...agricultural substrates is currently far from reaching its full potential. In Sweden, the number of biogas plants and their output have increased in recent years, but they are still experiencing harsh economic conditions. A recent evaluation (2010–2015) of 31 farm-scale biogas production facilities in Sweden sought to identify parameters of importance for further positive development. In this paper, data on plant operation, gas yield and digestate quality for 27 of these plants are summarised and statistically analysed to investigate factors that could allow an increase in overall biogas production and in nutrient content in the digestate. The analysis showed that addition of co-substrates to manure results in higher gas production, expressed as both specific methane potential and volumetric gas production, than when manure is the sole substrate. Use of co-substrate was also found to be influential for the nutrient content of the digestate. These observed improvements caused by co-digestion should be considered when subsidy systems for manure-based biogas processes are being created, as they could also improve the economics of biogas production. However, to achieve higher efficiency in existing biogas plants and to improve the situation for future investments, a more detailed, long-term evaluation programme should also be considered.
•The type and amount of co-substrate used with manure is critical for the final methane yield.•Biogas plants fed with pig manure compared to cattle manure has a higher digestate ammonium content.•Methane yield and degree of degradation correlate positively to the hydraulic retention time.•Biogas contribution from a second non-heated digester is relevant and needs further investigations.•Forthcoming incitements for evaluation and monitoring of biogas plants are important.
This study explores features of food system transformations towards sustainability in the
Farm to Fork Strategy
in relation to perspectives of Swedish food system practitioners. Transformations ...towards sustainable food systems are essential to achieve the United Nations’ 2030 Agenda and the need for more sustainable food systems has been recognised in the
European Green Deal
and its
Farm to Fork Strategy
. The Swedish ambition to act as a global leader in achieving the 2030 Agenda and the European Commission’s aspiration for Europe to lead global food system transformations offer a critical opportunity to study transformational processes and agents of change in a high-income region with externalised environmental and sustainability impacts. Drawing on theories of complex systems transformations, this study identifies features of food system transformations, exploring places to intervene and examines the roles, responsibilities, and agency related to these changes. The results of this study provide three main conclusions highlighting (i) alignment of high-level policy and the perspectives of national practitioners at the paradigm level, especially concerning how food is valued, which is a crucial first step for transformational processes to come about (ii) a lack of clarity as well as diversity of pathways to transform food systems although common objectives are expressed, and (iii) governance mechanisms as enablers for a diversity of transformations. Moreover, these processes must acknowledge the contextual and complex nature of food systems and the level of agency and power of actors.
In farm‐scale biogas systems, different kinds of manure are the most important substrate for anaerobic digestion, but result in low biogas yields. Biogas production can be increased by complementing ...the manure with forage crops, in codigestion. The aim of this study was to evaluate grass‐clover (GCS) and whole‐crop barley silages (WCB) in codigestion with manure from organic and conventional dairy production systems on biogas production, microbial community, degree of degradation and gas quality at different organic loading rates by addition of soya bean meal and wheat grain, which are rich in protein and starch. Four continuous stirred anaerobic laboratory‐scale reactors were used, and the codigestion resulted in additive effects on biogas production, but no synergistic effects. The highest biogas yield was obtained in reactors receiving WCB independently of manure types, for both experiments (7,416 ml/day and 10,978 ml/day respectively). The degradation efficiency, measured as the reduction in volatile solids was, on average, six percentage units higher in the reactors receiving manure from conventional compared with organic dairy cows, probably because of a higher concentration of undigested fibre and proteins in conventional cow manure. Microbiological analysis by illumina sequencing illustrated low impact of both manure types on the reactor community and only small differences between the reactors receiving GCS and WCB. However, addition of soya bean meal and wheat grain changed the community in all reactors. The ratio between Firmicutes and Bacteroidetes was comparably higher in reactors having the highest gas production and methane yield.
This study explores how geopolitical aspects can affect actors’ sense of agency to achieve the UN 2030 Agenda for Sustainable Development and its ambition to transform the world sustainably by ...studying the linkages between global change and the 2030 Agenda as described by Swedish change agents. Sweden has a self-declared ambition for leadership in the 2030 Agenda. The world’s high-income countries, including Sweden, have been given a specific responsibility to achieve the Sustainable Development Goals. The results of this focus group study show that the geopolitical landscape encompasses a multitude of actors and roles whose relationships are filled with tension, creating dichotomies between them. The analysis indicates that Sweden is assessed to be dependent on functioning ecosystems, both locally and globally, as well as causing global environmental change. Two narratives have emerged: (i) the narrative of the 2030 Agenda, referring to deliberate societal transformations that can be controlled and steered, and that have a direction; and (ii) the narrative of geopolitics, indicating perceptions of emergent transformations that appear uncontrollable, drifting aimlessly towards an unknown future. These narratives might influence the understanding of societal transformations, and need to be considered in the facilitation of platforms for deliberative transformations or responses to emerging transformations.
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