RESUMO A busca por energias alternativas que sejam renováveis está cada vez maior, assim como a preocupação com o crescente aumento da geração de resíduos pela população mundial. O aproveitamento energético do gás gerado pela decomposição dos resíduos sólidos é um caminho atrativo para a solução, de uma só vez, desses dois problemas. Com objetivo de contribuir para o desenvolvimento da geração de energia elétrica a partir de aterros sanitários no Brasil, o presente trabalho compreende uma análise de potencial energético e de viabilidade financeira dessa alternativa energética no Brasil. Para a construção das análises, utilizaram-se dados de geração de resíduos e climáticos de seis cidades brasileiras, o que permitiu a estimativa da vazão de produção de gás nos aterros de cada uma dessas localidades, a potência ótima a ser instalada em cada um desses aterros e da viabilidade econômica dessa alternativa. Os valores de custo de geração obtidos variaram entre R$ 345 e 440·MWh, sendo fortemente influenciados por fatores como população, captação de resíduos e aspectos climáticos, sendo, em geral, superiores aos valores típicos de tarifa de venda de energia no país. Isso implica uma necessidade de formulação de políticas públicas de incentivo à geração de energia a partir de resíduos sólidos urbanos no Brasil.

The agro-industrial systems comprise activities which transform raw materials of agricultural, aquacultural, livestock and forestry industries from primary production stages to consumption. Pig farming stands out in national and international markets for agro-industrial processes such as slaughtering and meat processing. Although this sector positively contributes to the economies of several countries, the high flow of waste resulting from implementing integrated production systems has led to serious environmental consequences (e.g., polluted water bodies and Greenhouse Gases - GHGs emissions). Among the treatment methods, anaerobic digestion reduces the organic load of biomass in the absence of oxygen, generating biogas and organic fertilizer. However, there are limitations associated with high CH4 variability and low yield, resulting a minimal and slow implementation in Brazil. Some research has reported the use of mineral additives to optimize the digestion process. This study comprises a bibliographic review of pig farming systems and production models, followed by an analysis on a global scale and environmental consequences. It is also discussed the use of additive minerals which have been applied in anaerobic digestion of swine manure as well as some prospects for global advances with opportunities to mitigate GHGs and bottlenecks. Despite being a promising technology, detailed evaluations of the use of these additives and their implementation in treatment plants must still be carried out in such a way to understand the optimization of such process.

This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We carried out the following steps: chemical–physical laboratory analyses of sludge samples; the building, operation, and monitoring of an experimental prototype of a batch bioreactor of 2.5 L for the AD of the sludge (with and without the addition of charcoal); qualitative measurements of biogas; the study of charcoal morphology; and the projection of useful energy generation from the AD sludge after treatment. A study on the economic viability and avoided greenhouse gas (GHG) emissions was performed based on the experimental results. The substrate showed alterations in all the physicochemical parameters evaluated after AD, such as a reduction of 35% in the biochemical oxygen demand (BOD) analysis; the experiment carried out using biochar showed positive results regarding the speed of CH₄ production and a greater potential for energy recovery. Enterprises from 2000 kW onwards would present an internal rate of return (IRR) equal to or higher than the minimum attractiveness rate (MAR) of 15%. The USD 95.28/MWh tariff presented economic feasibility for the studied scenarios. WWTPs that produce enough sludge to generate power of 2000 kW would need to process the waste of 117,200 inhabitants with charcoal addition and 136,000 without charcoal. It would be possible to avoid the emission of 2307.97 tCO₂/year (2000 kW). According to the results obtained, this study revealed that using alternative energies based on anaerobic digestion and biochar can generate positive results regarding methane production, and its application as an energy source in a WWTP proved to be economically viable at a specific level of power production.