Water, energy, and food are essential elements for human life, but face constant pressure resulting from economic development, climate change, and other global processes. Predictions of rapid economic growth, increasing population, and urbanization in the coming decades point to rapidly increasing demand for all three. In this context, improved management of the interactions among water, energy, and food requires an integrated “nexus” approach. This paper focuses on a specific nexus case: biogas generated from organic waste, a renewable source of energy created in livestock production, which can have water-quality impacts if waste enters water bodies. An innovative model is presented to make biogas and biomethane systems feasible, termed “biogas condominiums” (based on collective action given that small- and medium-scale farms on their own cannot afford the necessary investments). Based on the “farm to fuel” concept, animal waste and manure are converted into electrical and thermal energy, biofuel for transportation, and high-quality biofertilizer. This nexus approach provides multiple economic, environmental, and social benefits in both rural and urban areas, including reduction of ground and surface water pollution, decrease of fossil fuels dependence, and mitigation of greenhouse gases emissions, among others. The research finds that biogas condominiums create benefits for the whole biogas supply chain, which includes farmers, agroindustry, input providers, and local communities. The study estimated that biomethane potential in Brazil could substitute the country’s entire diesel and gasoline imports as well as 44% of the total diesel demand. In the United States, biomethane potential can meet 16% of diesel demand and significantly diversify the energy matrix.

O conceito de ‘smart city’ tem atraído o interesse da ciência, indústria e da sociedade nos últimos anos. As cidades inteligentes são caracterizadas pela implementação de tecnologias diversificadas para atender aos padrões de sustentabilidade e têm principalmente 6 critérios a serem considerados: pessoas, governo, economia, mobilidade, meio ambiente e vida. Este trabalho terá como foco a mobilidade, uma vez que é notável a crescente demanda por tecnologias avançadas e mais sustentáveis no transporte urbano, especialmente no que diz respeito à redução significativa nas emissões de gases de efeito estufa (GEE). Para um desenvolvimento sustentável adequado em uma cidade, é necessário planejar. A melhoria da qualidade de vida da população é consequência de práticas sustentáveis implementadas em ‘smart cities’. A cidade de Curitiba está localizada no sul do Brasil, desde os anos 70 é considerada como uma ‘smart city’, devido ao projeto pioneiro do sistema BRT (Bus Rapid Transit). Curitiba é referência mundial por seu planejamento urbano e iniciativas sustentáveis e inovadoras relacionadas à mobilidade urbana. Curitiba e comprometeu a introduzir ônibus de baixa emissão em sua frota para substituir o sistema BRT por híbrido-elétrico, com foco na redução de emissões de GEE e de sua energia sustentável. Como forma de contribuir para minimizar as consequências das mudanças climáticas, Curitiba tem enfrentado desafios para se tornar uma cidade cada vez mais sustentável e menos vulnerável aos efeitos climáticos. Portanto, para ser caracterizada como uma ‘smart city’, não se trata apenas de mudanças, mas de necessidades de planejamento. Este trabalho tem como foco a mobilidade, considerando fontes renováveis de energia para alimentar o transporte público urbano. Para um desenvolvimento sustentável adequado em uma cidade, é necessário planejar. A melhoria da qualidade de vida da população é consequência de práticas sustentáveis implementadas nas ‘smart cities’. Curitiba é uma das cidades que tem enfrentado os grandes desafios para se tornar uma cidade cada vez mais sustentável e menos vulnerável aos efeitos climáticos. Nesse cenário, o presente estudo visa analisar características do transporte público de Curitiba relacionado-o ao uso de fontes renováveis de energia. Considerando os padrões estabelecidos para ser caracterizada como ‘smart city’, Curitiba atende aos pré-requisitos necessários.

One of the challenges in the agribusiness sector in Brazil, the 4th largest food producer in the world, is to assess the effectiveness of participatory methods to convert animal manure into economic assets. In this scenario, biogas and biomethane stand out as renewable sources of energy available in all countries and their uses can significantly induce local and regional economic development. This study will present an arrangement known as agroenergy condominium for its multi-services, such as energy generation trough biogas and biomethane, biofertilizer, and mitigation of GHG emissions. The farmer’s key motivations to join the project were identified through individual interviews and analyzed using MICMAC and SWOT analysis methods. The most significant drives were environmental and economic aspects, which demonstrated their environmental citizenship, and the less influent variable was social motivation. Despite the challenges to be overcome, the results validate that this arrangement can bring benefits for the local community, enhance the energy security in the region and contribute to a more clean energy matrix. Furthermore, it can be replicated at lower cost and with technologies already known and consolidated. The results demonstrate the implications of the interdisciplinarity between technology, environment, and society.

Biogas is an important renewable source of energy, which converts organic material into energy. Lignocellulosic biomass emerges as a strategy to increase biogas production through pre-treatments that provide organic matter to the anaerobic environment. Among the chemical pre-treatments available, the alkaline is the most used one because it presents the highest yield in biogas production. However, the effluent (black liquor) it generates is an alkaline byproduct that, if disposed irregularly, can cause environmental problems. In this context, the objective of the present study is to present the methodology employed to evaluate the effect of alkaline pre-treatment with potassium hydroxide solution (KOH) applied to garden waste in the production of biogas and the reuse of black liquor as a new alkaline medium. The pre-treatment was divided into seven subsequent batches, with the first batch consisting of a 5% KOH solution and dry and crushed substrate (garden pruning waste). For the other batch the black liquor from the liquid fraction of the separation process was reused. The Biochemical Methane Potential (BMP) tests were carried out with the fraction sifted in mesophilic conditions (35 degrees C) for 25 days, following the German standard VDI 4630. The results showed that the second batch had the highest biogas production (620 LN biogas/VS-1 kg) and an efficiency of 30% when compared to the non-pretreated substrate. A positive effect was also observed in the biogas yield after reusing the black liquor twice, presenting an average efficiency of 20%. In this sense, this study demonstrates that the reuse of the remaining black liquor from pre-treatment with KOH is a viable and sustainable technique for pre-treatment of garden waste and contributes to the reduction of costs in real scale.

Greenhouse gas (GHG) emissions from livestock farms have steadily increased over the past two decades, yet waste-to-energy systems that can partly capture and reduce these emissions remain underutilized, particularly among small and medium farms. This study presents a novel optimization-based framework to evaluate regional biogas network designs that aggregate livestock manure for energy production. A non-linear bi-objective optimization model is developed, using validated field data from Southern Brazil, to maximize economic (profit) and environmental (GHG savings) objectives. The model identifies optimal infrastructure configurations and energy product pathways (biomethane vs. electricity) across multiple regions. Results demonstrate that biomethane production, under current market conditions in Brazil, is significantly more profitable and environmentally advantageous than electricity generation. Biomethane systems benefit from decentralized, municipality-level infrastructure, achieving profitability with minimal manure transport. In contrast, electricity production requires centralized facilities and regional coordination, resulting in higher transportation costs and emissions. Sensitivity analysis reveals that the relative pricing of electricity and biomethane is a critical determinant of the preferred system architecture. The most significant contribution of this research lies in the simultaneous optimization of technical design and spatial cooperation strategies for waste-to-energy systems—an area underexplored in prior work. The findings underscore the feasibility of economically and environmentally sustainable manure management systems in rural areas, offering a transferable framework to support strategic planning and policy development in other regions.