Addressing environmental challenges while improving social and economic conditions calls for innovative solutions. One of those challenges is the management of organic waste, which if left untreated can lead to water pollution, greenhouse gas emissions, and soil degradation. Brazil produces substantial amounts of organic waste due to its sizeable population and extensive agricultural production. As one of the largest economies in the Global South, the development of innovative solutions to organic waste management in Brazil can potentially pave the way for their adoption in other countries within the Global South. Biogas systems are solutions for organic waste treatment that simultaneously make use of the energy content, reduce gas emissions, and facilitate nutrient recycling. Nevertheless, their multifaceted nature also entails numerous barriers to their widespread implementation. Thus, this report explores the barriers to the development of biogas systems in Brazil and possible strategies to overcome these.

Diverse data collection methods were used in the study. A literature review helped identified overall barriers to biogas systems development. This was followed by a field study in Brazil, involving visits to biogas facilities and interviews with stakeholders. The results were combined to understand the impact of the identified barriers across sectors. Finally, a workshop with Brazilian and Swedish stakeholders helped validate the findings and explore possible strategies to overcome barriers to biogas systems development.

In the report barriers across eight categories are discussed, namely technological, economic, market, regulatory, cultural, environmental, network, and biomethane barriers. Technological barriers include lack of specialized knowledge, which leads to challenges in operation and maintenance of biogas reactors. Another type of technological barrier is limited access to infrastructure such as gas pipelines and sewage networks, which leads to technical challenges regarding both substrate supply and gas handling. High initial investments and funding accessibility are the most prominent economic barriers. Market barriers include competition with cheaper waste treatment solutions, lack of structured markets for biogas, and limited access to markets. The absence of a national biogas-specific policy, spatial diversity in state-level regulations; together with few and isolated incentives for biogas production are the major regulatory barriers. Cultural barriers include limited knowledge among society and substrate holders about biogas benefits, resistance to waste segregation practices, and sectoral structures hindering collaboration across the biogas value chain. Although environmental aspects of biogas systems are usually drivers to the implementation of biogas facilities, concerns such as gas leaks, odors, and soil contamination risks associated with poor facility design and performance are environmental barriers. Network barriers stem from limited platforms for discussion and interaction among actors, ultimately delaying the establishment of a unified national agenda for biogas development. Due to its characteristics, the production, distribution, and utilization of biomethane face additional challenges across various barrier categories, with major obstacles including uncertainties in grid injection contracts and infrastructure, as well as the expectation that biomethane prices should match those of natural gas.

To overcome some of the barriers presented above, the study explored two strategies that could be pursued by actors interested in biogas systems development in Brazil. First, biogas cooperatives are proposed as one solution, allowing resource pooling for technology investment and enhanced biogas production. Second, dedicated biogas producers could play a crucial role,viparticularly in addressing financing challenges and ensuring efficient operation. Dedicated biogas producers could improve the technical efficiency and environmental performance of biogas facilities. Options for biogas utilization include electricity generation and biomethane production, with the latter offering tax benefits and reduced transportation costs when producers can use the biomethane for transportation themselves.

The report highlights barriers across various dimensions and addresses strategies to overcome these barriers, such as biogas cooperatives and dedicated biogas producers. Future research could focus on testing these strategies in the Brazilian context through case studies, pilot projects, and collaborative initiatives to refine interventions and accelerate the adoption of biogas technologies.

This document accompanies an art & science collaborative exhibit exploring how urban agriculture can contribute to sustainable resource flows to support food production, recreation, and water quality.

Denna broschyr har tagits fram i anslutning till en utställning där en forskargrupp samverkar med en konstnär. Den utforskar hur stadsodling kan bidra till hållbara resursflöden och därigenom stödja produktion av livsmedel, rekreation och god vattenkvalitet.

Digestate processing is a strategy to improve the management of digestate from biogas plants. Solid-liquid separation is usually the primary step and can be followed by advanced treatments of the fractions. The knowledge about the performance of the separators and the quality of the fractions is scattered because of many available techniques and large variability in digestate characteristics. We performed a systematic review and found 175 observations of full-scale solid-liquid separation of digestate. We identified 4 separator groups, 4 digestate classes based on substrate, and distinguished whether chemical conditioners were used. We confirmed the hypothesis that the dominant substrate can affect the efficiency of the digestate separation. Furthermore, the results showed that centrifuges separated significantly more dry matter and total P than screw presses. Use of chemical conditioners in combination with a centrifuge lowered the dry matter concentration in the liquid fraction by 30%. Screw presses consumed 4.5 times less energy than centrifuges and delivered 3.3 tonne ammonium N in the liquid fraction and 0.3 tonne total P in the solid fraction using 1 MWh. The results can provide data for systems analyses of biogas solutions and can support practitioners when choosing among full-scale separator techniques depending on the digestate type. In a broader perspective, this work contributes to the continuous improvement of biogas plants operations and to their role as nutrients recovery sites.

The main idea was to justify the natural, technological, and ecological aspects of digestate-based composite for heavy metals (HMs) binding in soil due to organic matter content and mineral additives’ biosorption properties. The study aimed to determine the potential of a composite made from digestate and phosphogypsum for remediation of HMs polluted soils and the role of dissolved organic matter (DOM) in binding HMs. Methods used included a literature review to identify the mechanisms for HM binding to digestate DOM, a laboratory setup for producing a digestate-based composite with digestate (from manure or sewage sludge) mixed with phosphogypsum, and an analysis of digestate fluorescence properties. Results show that a composite based on digestate from manure as feedstock had a higher fluorescence complexity index than a composite with sewage sludge digestate (2.2 and 1.71, respectively). However, the DOM stability in the sewage sludge digestate composite was higher than reported in the literature, probably due to the mineral composition of phosphogypsum, which resulted in a high HMs sorption capacity and its positive effect on soil microbial activity. Based on the theoretical substantiation of DOM content and its binding properties, manure was the most effective feedstock type out of the two tested if digestate was used for HM remediation. Using a digestate-based composite with phosphogypsum can potentially reduce the ecological risk levels imposed by HM-contaminated soils from considerably too low.

I denna studie undersöktes potentialen för etableringen av nya biogassystem inom ett geografiskt område som utgjordes av Region Sörmlands kommuner samt kommunerna Södertälje, Nykvarn, Norrköping och Söderköping. Anledningen till studien är det studerade områdets förhållandevis låga nuvarande biogasproduktion samt den stora potentiella efterfrågan på biogas i området, då SSAB i framtiden kommer behöva biogas till sin fossil-fria stålbearbetning. I studien studerades den tekniska och administrativa potentialen, det vill säga vad som är möjligt att producera under dagens administrativa villkor samt med dagens (och en nära framtids) teknik. Potentialen undersöktes utifrån fyra olika potentialer: rötbar biomassapotential, biogaspotential, koldioxidproduktionspotential och näringscirkulationspotential. Resultatet visar på en biogaspotential mellan 380 och 540 GWh per år vilket skulle motsvara en stor ökning från dagens produktion på mellan 50 och 60 GWh per år. Ytterligare 100 GWh per år skulle kunna produceras av koldioxiden genom biometanisering men då krävs stora mängder vätgas. Angående näringscirkulationspotentialen så kan biogödseln (som samproduceras med biogas i biogasanläggningar) uppfylla cirka tre fjärdedelar av kvävebehovet, nära hela fosforbehovet och fyra gånger kaliumbehovet i det studerade områdets jordbruk. Det studerade området delades upp i fem produktionsområden för att öka upplösningen i studien. Dessa områden valdes för att de skulle kunna utgöra delområden som är stora nog för att etablera biogasanläggning av den storlek som krävs för att förvätska biogasen och samtidigt undvika alltför långa transportsträckor för substrattransporter. Detta svarar upp mot trenden att etablera större och större biogasanläggningar samt ett ökat fokus på förvätskad biogas. Dock kan mindre anläggningar vara nödvändiga för att uppnå vissa delar av potentialen i områden med små, men betydelsefulla, substratmängder. Det produktionsområde med störst potential var Söderköping/Norrköping men det betyder nödvändigtvis inte att det är det mest lovande produktionsområdet att börja mer fokuserade implementeringsstudier i då andra faktorer så som lönsamhet inte undersökts i denna studie. Fortsatta studier bör fokusera på hur lantbruksrelaterade substrat kan användas inom biogasproduktion. Här kan studier fokusera på olika områden, exempelvis hur biogasanläggningar kan drivas stabilt på enbart grönmassa (till exempel vall och mellangrödor) och hur ökad odling för biogasproduktion påverkar mat- och foderproduktion, individuella lantbrukare samt åkermarkens långsiktiga hälsa. Dessutom behövs implementeringsstudier för att realisera potentialen, dessa bör fokusera på att undersöka specifika etableringsmöjligheter utifrån ekonomiska, tekniska, logistiska och administrativa perspektiv.

In this  study we have investigated the role of biogas solutions to support increased resource efficiency on the island Gotland,  including recovery and redistribution of nitrogen (N) and phosphorus (P) within the agricultural sector. First, we  analyzed the potential for  expanding energy and nutrient recovery from organic residues using biogas solutions. Our findings suggest that the biogas production could expand to 165 GWh, from the current 36 GWh (2020), with manure accounting for a potential  110 GWh biogas annually if all were digested. Comparing the nutrients contained in organic feedstock with the crop nutrient demand on Gotland showed that for N the  demand is 2.4 times higher than the supply. In contrast, the calculations showed a 137 tonnes P surplus, with distinct excess areas in the center and southern part of the island.

We then compared scenarios with different numbers (3 - 15) of biogas plants with respect to   efficient nutrient redistribution and transport costs. Spatial constraints for new plants, e.g. need for roads with a certain capacity  and permit issues, were accounted for by  adding local information to a national data set. We identified  104 potential locations (1 km$^2$ grid cells) and used an optimization model to identify the most suitable locations for minimized transport costs. Optimal  (meeting the crop demand with no excess) redistribution of all nutrients contained in the feedstock, as raw digestate from biogas plants, would result in an export of 127 tonnes of P from the island. The model results indicated that if all potential feedstock would be digested in three additional biogas plants and nutrients redistributed for optimal reuse, the total transport  cost would be 2.6 million SEK annually, excluding the costs for nutrient export from the island (3.7 million SEK). If instead 10 or 15 smaller plants would be built, the transport cost would drop to 1.8  million SEK, with the same amount of P being exported. Comparing the scenarios with different number of biogas plants (3 - 15), showed that some locations are more suitable than others in terms of distance to feedstock and

to fields with fertilizer demands. Finally, a preliminary analysis of the amount of crop residues indicated that this type of feedstock could add a substantial amount of biogas production, but more extensive analyses are needed to assess  the feasibility to realize part of that potential.

Urban agriculture has a high potential to contribute to local circular economies, for instance by using nitrogen, phosphorus, and potassium in city organic waste streams as fertilizer inputs. However, inefficient use of waste-derived fertilizers could contribute to local water quality impairment related to nitrogen and phosphorus losses. Organic waste derived fertilizers are particularly challenging from a nutrient stoichiometry perspective, making over- and under-application of a particular nutrient likely. Where, and under what conditions, urban agriculture acts as a net positive for a circular nutrient economy vs. a nutrient water quality risk remains unclear. Here we review empirical peer-reviewed studies (2000–2021) on soil- and ground-based urban agriculture with a stated concern for nutrient losses to water. Of the 20 publications retained and reviewed (out of 241 screened), only seven measured losses to waters. There were four experimental studies, of which three measured nutrient leachate losses under different garden management practices. Of the 16 studies done in real-world conditions, only four quantified losses to water as leachate; average losses spanned 0.005 to 6.5 kg ha−1 for phosphorus, and 0.05 to 140 kg ha−1 for nitrogen. 13 of the 16 non-experimental studies provided data on nutrient inputs and harvested crop outputs, which could be used to calculate garden nutrient balances—an indicator of nutrient use efficiency. Although the value ranges were large, most studied gardens showed nutrient surpluses (inputs > crop harvest) for nitrogen and phosphorus (but not potassium); these surpluses were identified as a risk for losses to water. Contextual factors such as different access to fertilizers and knowledge, along with regulations and environmental factors can help explain the wide range of balance values and nutrient losses observed. Although a large surplus of inputs was often linked to increased leachate losses, it was not always the case in the limited number of studies we identified. Our review suggests that more field studies that measure losses to waters, and document contextual factors, are needed to determine how urban agriculture may contribute to a sustainable circular economy for all three nutrients without nutrient-related water quality impairment.

In this paper, we performed technology assessment and systems analysis of primary digestate processing techniques to provide a comprehensive analysis of their environmental and cost performance. We compiled more than 100 observations from large-scale biogas plants and considered digestate based on manure, crops and agro-wastes, and food waste under the geographical contexts of Sweden and Belgium. Centrifuge, screw press, and rotary drum were identified as suitable primary processing techniques. We analyzed the climate impact, energy use, and operational cost of digestate management under these scenarios: no processing, partial processing (solid-liquid separation) and full processing (solid-liquid separation followed by ammonia stripping). As expected, the suitable digestate processing varied with the context, transport was often the most critical cost factor, and emissions from storage reduced the climate savings from the use of biofertilizers. However, treating liquid fraction became a main contributor to cost and climate impact under the Belgian conditions. Consequently, the possibility for local application of liquid fraction as biofertilizer could prevent costs and impacts associated with its further treatment. The main novelty of this work is in its integrative and comprehensive approach toward the choices and impacts of primary processing of digestate. We tried to bridge many individual case studies, drew from experiences of biogas plants in different geographical contexts, assessed suitable processing techniques for different digestate types, and analyzed the environmental impacts and cost of digestate management from a life cycle perspective. We believe that such integrated approaches would help decision-making for increased sustainability of the biogas sector.