Geração de energia usando biogás de aterros sanitários no Brasil: um estudo de potencial energético e viabilidade econômica em função da população / Power generation using landfill biogas in Brazil: a study of energy potential and economic viability in terms of the population

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.

ABSTRACT The search for alternative and renewable sources of energies is growing, as is the concern with the growing increase in the generation of waste by the world population. The energy use of the gas generated by the decomposition of solid waste at landfills is an attractive way to solve these two problems, at once. In order to contribute to the development of electric power generation from landfills in Brazil, the present work comprises an analysis of the energy potential and financial viability of this energy alternative in the country. For the construction of the analyses, waste and climate generation data from six Brazilian cities were used, which allowed the estimation of the gas production flow in the landfills of each city, the optimum power to be installed in each of these landfills and the economic viability of this alternative. The generation cost values obtained ranged between R$ 345 and 440·MWh, being strongly influenced by factors such as population, waste capitation and climatic factors, being, in general, higher than the typical values of energy sales tariff in the country. This implies a need to formulate public policies to encourage the generation of energy from solid urban waste in Brazil.

Biofuel production potential of indigenous isolates of Scenedesmus sp. from lake water in Pakistan

Aims@#This paper presents the report on biodiesel and biogas production at a laboratory scale from Scenedesmus strain.@*Methodology and results@#Previously isolated and identified Scenedesmus were grown in 10 Liter flask using BG-11 media at 16 h light and 8 h dark cycle. Oven-dried biomass (20 g) from 16-day-old culture of Scenedesmus was finely grounded and subjected to lipids extraction by chloroform-methanol-NaCl mixture. Microalgal lipids (6 mL) were subjected to transesterification by using NaOH leading to the production of 5 mL biodiesel and 4 mL of glycerin. Biodiesel was rich in methyl esters of linoleic acid, phosphorothioc acid and dodecanoic acid, as shown by gas chromatography-mass spectrometry (GC-MS) analysis. Oven-dried microalgae (2 g) without lipid extraction and leftover biomass (2 g) after lipid extraction were subject to biogas production through anaerobic digestion. Biogas (34, 27 and 19 mL) were recorded respectively in oven-dried whole biomass; lipid extracted biomass and control over a period of 15 days of anaerobic digestion.@*Conclusion, significance and impact of study@#It was concluded that water bodies are rich in diverse algae, especially Scenedesmus sp., and this algae can be cultured to produce biodiesel and biogas. But the lipid accumulation potential of microalgae requires special treatment and lipid extraction methods are not up to the mark, which is a major bottleneck in biofuel production from microalgae.

Design and Development of Solar-biogas Hybrid Dryer for Onion Drying

A solar-biogas hybrid dryer was designed, developed and tested for onion drying with a capacity of 8 kg/batch. Solar energy was utilized as primary energy for onion drying in a greenhouse type drying chamber (direct solar) and biogas powered air heater used as a supplementary heat source for continuous operation. The hybrid dryer consists of greenhouse type drying chamber, concentric pipe air heater and biogas burner. The greenhouse type drying chamber has floor area of 1300 mm×900 mm and collector area of 3 m2. The dryer was operated as a solar dryer during normal sunny day and hybrid mode whenever sunlight is insufficient to maintain desired 60°C inside the drying chamber. The results indicated that the moisture content of onion slices reduced from 80.06% (wb) to 9.88% (wb) in 12 hours in hybrid mode drying. A biogas powered air heater operated for 3 hours in a day with effectiveness of 0.87 and biogas burner efficiency of 47.59%. The dryer was techno-economically feasible with a benefit cost ratio of 1.12 and payback period of 2.1 years.

CFD simulation and PIV validation of the gas/liquid behavior in an UASB reactor / Simulação CFD e validação PIV do comportamento gás/líquido em um reator UASB

ABSTRACT As the world population increases, the need to develop more efficient wastewater treatment systems requires the use of new technologies. Software aided project and optimization of bioreactors and bioprocesses have become a matter of interest in recent years, especially due to the advance in the state-of-the-art of computational resources. This work aimed to perform gas/liquid numerical simulations using the Fluent 16.2 software and to validate this model through Particle Image Velocimetry (PIV) and shadow imaging techniques. Eulerian-Eulerian, laminar, tridimensional and transient simulations were carried out. The results for the mass imbalance for the gas and liquid phases, gas volumetric fraction, gas velocity, bubble size, liquid magnitude and upflow velocity and the velocity profiles for the liquid phase were successfully validated against experimental data. Concerning the dispersed phase, it was found a difference of 4.37% for the gas volumetric fraction between experiments and simulations. Simulated results showed a difference for the bubble mean velocity of 1.73% when compared with shadow imaging results. No coalescence was observed along the experiments, and the flow regime was characterized as dispersed bubble flow. Regarding the liquid phase, it was found a difference of 3.2% for the mean velocity, between simulated and PIV results. Simulated and experimental velocity profiles showed a better agreement at the center of the reactor. Some differences were observed in those profiles, due to geometry simplifications assumed in order to get a better mesh. Considering the good agreement between simulation and experiments, the model was considered validated.

RESUMO Conforme a população mundial aumenta, a necessidade de desenvolvimento de sistemas de tratamento de efluentes mais eficientes requer o uso de novas tecnologias. O projeto e otimização de biorreatores e bioprocessos auxiliados por softwares têm se tornado uma questão de interesse, em especial devido ao avanço no estado da arte quando se trata de recursos computacionais. O objetivo deste trabalho foi realizar simulações numéricas gás/liquido, utilizando o software Fluent 16.2, e validar experimentalmente o modelo computacional através de técnicas de PIV e Shadow Imaging. Foram realizadas simulações laminares, tridimensionais, transientes adotando uma abordagem Euleriana-Euleriana. Os resultados para o desequilíbrio de massa para as fases gasosa e líquida, a fração volumétrica de gás, a velocidade do gás, o tamanho da bolha, a magnitude e a velocidade ascensional do líquido e os perfis de escoamento do líquido foram validados experimentalmente com êxito. Foi verificada uma diferença de 4,37% entre resultados numéricos e experimentais para a fração volumétrica de gás no reator. Quando comparados os resultados das simulações com os resultados obtidos através de Shadow Imaging, foi encontrada uma diferença de 1,73% para a velocidade média da bolha. Não foi verificada coalescência ao longo dos experimentos realizados, e o escoamento foi caracterizado como fluxo de bolhas dispersas. Em relação à fase líquida, foi encontrada uma diferença de 3,2% para a velocidade média, entre os resultados simulados e de PIV. Os perfis de velocidade simulada e experimental mostraram uma melhor concordância no centro do reator. Algumas diferenças foram observadas nesses perfis, devido às simplificações geométricas assumidas para obter uma malha melhor. Considerando a boa concordância entre resultados numéricos e experimentais, o modelo foi considerado validado.

The effect of introduction of chicken manure on the biodiversity and performance of an anaerobic digester

Background: Ammonium stress is a prime limiting phenomenon that occurs during methane formation from poultry manure. It is caused by elevated ammonium nitrogen concentrations that result from substrate decomposition. The amounts of methane formed depend on the activity of methanogenic microbes. Results: During the research reported in this paper, the response of a mesophilic consortium inhabiting a biogas reactor to rising load of poultry manure was investigated. The taxonomic composition of bacterial population was mostly typical, however syntrophic bacteria were not detected. This absence resulted in limitation of succession of some methanogenic microorganisms, especially obligate hydrogenotrophs. The methanogenic activity of the consortium was totally dependent on the activity of Methanosaeta. Inhibition of methanoganesis was noticed at ammonium nitrogen concentration of 3.68 g/L, total cessation occurred at 5.45 g/L. Significant amounts of acetic acid in the fermentation pulp accompanied the inhibition. Conclusions: The effectiveness of the consortium was totally dependent on the metabolic activity of the acetoclastic Methanoseata genus and lack of SAOB did not allow hydrogenotrophic methanogens to propagate and lead to cessation of biogas production at an elevated ammonium concentration at which acetoclastic methanogens were inhibited.

Producción de Biogás a partir de residuos orgánicos generados en el Hospital de Clínicas: Un estudio preliminar / Biogas production from organic waste generated at the Hospital of Clinics: A preliminary study

Introducción: La producción de biogás es un proceso natural que ocurre en forma espontánea en un entorno anaerobio, realizado por microorganismos como parte del ciclo biológico de la materia orgánica. Los biodigestores son sistemas diseñados para optimizar la producción de biogás a partir de desechos agrícolas, estiércol o efluentes industriales. Objetivo: Realizar un estudio preliminar de producción de biogás a partir de residuos orgánicos generados en el Hospital de Clínicas, año 2017. Metodología: Estudio cuasi experimental tipo grupo control no equivalente consistente en dos sistemas: en el sistema 1 se ha expuesto a la sombra, con 39 kilos de residuos de cocina, 3 kilos de estiércol, 5,5 de pH, 1 a 4 de residuo/agua durante 30 días. En el sistema 2, se ha expuesto a pleno sol, con 68 kilos de residuo de cocina, 10 kilos de estiércol, 7 de pH, 1 a 1 de residuo/agua, durante 30 días. Resultados: La producción de gas al mes en el sistema 2 fue de 4,6 litros no observándose producción alguna en el sistema 1 (p= 0,000). Con un promedio de producción de residuos de cocina en el Hospital de Clínicas de 22077±780 kilos al mes, se estima una producción de 1485± 61 litros de biogas (R2= 97,98 p= 0,000) mensuales. Conclusión: Los biodigestores permiten una obtención de energía limpia y de bajo costo a partir de una fuente renovable.

Introduction: Biogas production is a natural process that occurs spontaneously in an anaerobic environment, carried out by microorganisms as part of the biological cycle of organic matter. Biodigesters are systems designed to optimize the production of biogas from agricultural wastes, manure or industrial effluents. Objective: To carry out a preliminary study on the installation of organic biodigesters in the Hospital of Clinics in order to replace the use of energy in the form of liquefied cooking gas. Methodology: Quasi-experimental study of a non-equivalent control group consisting of two systems. In system 1, it has been exposed to shade, with 39 kilos of kitchen waste, 3 kilos of manure, 5.5 pH, 1 to 4 waste / water for 30 days. In system 2, it has been exposed to full sun, with 68 kilos of kitchen waste, 10 kilos of manure, 7 pH, 1 to 1 waste / water, for 30 days. Results: Gas production per month in system 2 was 4.6 liters, with no production observed in system 1 (p = 0.000). With an average production of kitchen waste at the Hospital of Clinics of 22077 ± 780 kilos per month, an estimated production of 1485 ± 61 liters of biogas (R2 = 97.98 p = 0.000) per month. Conclusion: biodigesters allow obtaining clean and low-cost energy from a renewable source.

Análise do potencial de aproveitamento energético de biogás de aterro e simulação de emissões de gases do efeito estufa em diferentes cenários de gestão de resíduos sólidos urbanos em Varginha (MG) / Analysis of the potential use of landfill biogas energy and simulation of greenhouse gas emissions of different municipal solid waste management scenarios in Varginha, MG, Brazil

RESUMO O presente trabalho propõe avaliar a viabilidade econômica e ambiental de aproveitamento energético do biogás do aterro sanitário do município de Varginha (MG), além de analisar as emissões de gases de efeito estufa (GEE) e o uso de energia em diferentes cenários hipotéticos de gerenciamento de resíduos sólidos urbanos (RSU). Considerou-se uma projeção de geração de RSU em 20 anos de funcionamento do aterro, cuja produção de biogás foi estimada por meio do software LandGEM©. A análise de viabilidade econômica foi realizada por meio dos indicadores de valor presente líquido (VPL) e taxa interna de retorno (TIR). As emissões de GEE foram estimadas aplicando-se o modelo Waste Reduction Model (WARM©), considerando o cenário atual e três cenários alternativos de gerenciamento de RSU. Os cenários diversificaram em estratégias de reciclagem, digestão anaeróbia, incineração e disposição em aterro, com recuperação energética. Somente o aproveitamento energético com potência de 150 kW resultou em viabilidade econômica. Já os maiores benefícios ambientais foram obtidos pelo cenário 3, baseado na recuperação de materiais recicláveis, digestão anaeróbia e incineração dos RSU, reduzindo consideravelmente o volume de RSU destinados ao aterro. Dentre as práticas de gerenciamento dos cenários propostos, a reciclagem obteve os maiores ganhos energéticos e remoção de emissões de GEE.

ABSTRACT The present work proposes to evaluate the economic and environmental viability of energy recovery from biogas in the landfill of Varginha-MG, as well to analyze greenhouse gas emissions (GHG) and energy consumption in different scenarios of municipal solid waste (MSW) management. A 20-year projection of MSW generation and landfill operation were considered, whose biogas production was estimated through LandGEM software. The economic feasibility analysis was performed using the net present value (NPV), and the internal rate of return (IRR) as indicators. GHG emissions were estimated by applying the WARM model (Waste Reduction Model) considering the current MSW management scenario and three alternative ones. The scenarios diversified into recycling strategies, anaerobic digestion, landfill disposal and incineration with energy recovery. Only the energy recovery with a power of 150 kW resulted in economic viability. Moreover, the largest environmental benefits were obtained by scenario 3, based on the recovery of recyclable materials, anaerobic digestion and incineration of MSW, considerably reducing the volume of MSW landfilled. Among all management practices of the proposed scenarios, recycling resulted in greater energy gains and GHG emission removal.

Bacterial pretreatment of paddy straw for enhancing biogas production

Aim: Increasing the digestibility of paddy straw and biogas production by pretreating it with bacterial culture, Delftia sp. PP4_S3. Methodology: The chopped (3-5 cm) and soaked paddy straw in different sets (each with 250 g PS) were pretreated with bacterial culture i.e., Delftia sp. PP4_S3 suspension for different durations and was further utilized for biogas production. Results: Biogas yield was highest (180 l kg-1 PS) in paddy straw treated with Delftia sp. PP4_S3 for 3 days showing an increase of 66.1% from untreated paddy straw. Chemical analysis approximately showed that maximum reduction of lignin (45.7%) and silica (17.7%) occurred in 5 days of pretreatment. Interpretation: Treatment of paddy straw with Delftia sp. PP4_S3 enhance the digestibility of paddy straw by lowering the lignin and silica content. These observations showed that Delftia sp. PP4_S3 is a good lignocellulosic degrader and can be efficiently used for enhancing biogas production

Estado da arte dos aterros de resíduos sólidos urbanos que aproveitam o biogás para geração de energia elétrica e biometano no Brasil / State of art of landfills that use biogas for the generation of electrical energy and biomethane in Brazil

RESUMO O aproveitamento do biogás gerado a partir da decomposição da matéria orgânica dos resíduos sólidos urbanos (RSU), além de ser uma fonte renovável de energia, também contribui com a redução do lançamento de metano e do dióxido de carbono (CO2) na atmosfera, que são importantes gases de efeito estufa (GEE). No entanto, o biogás é pouco explorado no país e seu potencial continua sendo controverso, principalmente devido às diferentes metodologias de avaliação adotadas. A pesquisa realizada mostra que, entre 2004 e 2015, foram implantadas nos aterros de resíduos do País somente 9 usinas termelétricas, que juntas geram 86,3 MW de energia elétrica, e duas usinas que produzem biometano. Considerando as estimativas existentes, o Brasil explora somente de 7 a 20% do biogás produzido nos aterros de resíduos para fins energéticos.

ABSTRACT The use of biogas generated by the decomposition of organic matter from urban solid waste, besides being a renewable source of energy, also contributes to the reduction of the methane and carbon dioxide's release into the atmosphere, which are significant greenhouse effect gases (GHG). However, biogas is little explored in the country and its potential remains controversial, mainly due to the different adopted methodologies of evaluation. This research shows that, between 2004 and 2015, only nine thermoelectric plants were implanted in waste landfills in the country, which together generated 86.3MW of electricity and two plants that produced biomethane. Considering the existing estimates, Brazil exploits only 7 to 20% of the biogas produced in landfills for energy purposes.

Biogas and Biomass Implementation in Rural Areas

Abstract Advances in energy demand in rural areas cannot be dissociated from agricultural modernization, large estates, mechanization of labor and reduced investment in small production. The use of biogas together with biomass are the most cost-effective ways for the small producer, as it has a high calorific value. In the case of biogas the procedure is performed by combining a compressor and a chiller, allowing the gas enter the reactor and burn together with the air stream. The use of these techniques is an auxiliary way to reduce the cost of the producer to produce a certain crop, besides allowing a participation in the final energy supply, so that the utilities have an alternative to distribute the surplus energy to another region, serving thus a wider range in the rural area.

Energy Potential of Animal Waste in the State of Paraná (Brazil)

Abstract Animal biomass is a source of energy commonly discarded without or with low utilization, but its availability draws attention to its reuse [1]. The utilization can be carried out in different ways, varying in terms of generation time and efficiency. The use of biodigestion requires a relatively small area compared to landfills or natural composting, and it provides other materials besides biogas, that can be recycled as fertilizer and has a short residence time of residues [2]. The energy supplied as biogas can be harnessed as heat or electricity in case of conversion. Considering the energy needs of animal husbandry and the ease of reinsertion of energy in the production cycle, the possibility of distributed generation of biogas was studied as a way to complement the rural energy consumption matrix. Poultry farms require heat for chicks [3], dairy production centers require sterilization of used equipment [4] and pig farms require good heating systems to ensure animal weight gain [5]. In this way, the production can take advantage of the heat of the gas without the conversion into electricity, minimizing losses. Creation centers themselves can also generate electricity, eliminating the need for large transmission lines.

Evaluation of biogas and syngas as energy vectors for heat and power generation using lignocellulosic biomass as raw material

The use of nonrenewable energy sources to provide the worldwide energy needs has caused different problems such as global warming, water pollution, and smog production. In this sense, lignocellulosic biomass has been postulated as a renewable energy source able to produce energy carriers that can cover this energy demand. Biogas and syngas are two energy vectors that have been suggested to generate heat and power through their use in cogeneration systems. Therefore, the aim of this review is to develop a comparison between these energy vectors considering their main features based on literature reports. In addition, a techno-economic and energy assessment of the heat and power generation using these vectors as energy sources is performed. If lignocellulosic biomass is used as raw material, biogas is more commonly used for cogeneration purposes than syngas. However, syngas from biomass gasification has a great potential to be employed as a chemical platform in the production of value-added products. Moreover, the investment costs to generate heat and power from lignocellulosic materials using the anaerobic digestion technology are higher than those using the gasification technology. As a conclusion, it was evidenced that upgraded biogas has a higher potential to produce heat and power than syngas. Nevertheless, the implementation of both energy vectors into the energy market is important to cover the increasing worldwide energy demand.

Tratabilidade do lodo biológico têxtil e produção de biogás em reator UASB em diferentes temperaturas / Textile biological sludge treatability and biogas production in UASB reactor under different temperatures

RESUMO Neste trabalho avaliou-se o comportamento de um reator UASB em escala laboratorial (16 L) no tratamento de lodo biológico têxtil com produção de biogás, operando em diferentes temperaturas, 35 (mesofílica), 45 e 55ºC (termofílica), com tempo de detenção hidráulica (TDH) constante de 24 h. O reator UASB apresentou-se apto a tratar o lodo têxtil, sendo influenciado positivamente pelo incremento da temperatura, mostrando maiores remoções nas temperaturas termofílicas e com altas taxas de remoção de todos os parâmetros físico-químicos monitorados: demanda química de oxigênio (DQO) (97% em 45 e 55ºC), demanda bioquímica de oxigênio (DBO) (95% em 45ºC e 94% em 55ºC), fósforo total (P-total) (95% a 45 e 55ºC) e nitrogênio total (N-total) (94% a 45 e 55ºC). Quanto à produção de biogás e à concentração de metano, os maiores valores foram observados a 45ºC. Com base nos resultados alcançados, confirmam-se a tratabilidade do lodo têxtil e a produção de biogás em UASB, com melhor performance a 45ºC.

ABSTRACT The aim of this work was to evaluate the behavior of a laboratory-scale UASB reactor (16 L) in the treatment of textile biological sludge with biogas production, operating at different temperatures - 35 (mesophilic), 45 and 55ºC (thermophilic) -, with constant hydraulic retention time of 24 h. The UASB reactor was able to treat the textile sludge, being positively influenced by increasing temperature, with greater removals in thermophilic temperatures and high removal rates of all monitored physical and chemical parameters: chemical oxygen demand (COD) (97% at 45 and 55ºC), biochemical oxygen demand (BOD) (95% at 45ºC and 94% at 55ºC), total phosphorus (P-total) (95% at 45 and 55ºC) and total nitrogen (N-total) (94% at 45 and 55ºC). As for biogas production and methane concentration, the highest values were observed at 45ºC. Based on the results, textile sludge treatability and biogas production in UASB are confirmed, with best performance at 45ºC.

Storage of purified biogas (biomethane) at low pressure

ABSTRACT The global use of fossil energy sources has led to the need to develop technologies capable of mitigating its consequences. One such option is anaerobic biodigestion, which is already scientifically well-established, although the use of its main products (biogas and biomethane) still requires further development before they can be employed in automotive vehicles, largely due to technical issues concerning their storage. The storage of methane using adsorption (Adsorbed Natural Gas - ANG) is a technology that requires less energy and moderate pressures and temperatures. However, the main storage techniques continue to be those that involve high pressures and/or cryogenic temperatures. The present work evaluates the performance of an unprecedented prototype developed by UFPR for the storage of methane by adsorption, employing commercial activated carbon. The factorial design (2²) indicated that the storage capacity of the system was 39.41 V /V using activated carbon, and the desorption process was effective at 60ºC. Thus, the use of adsorbents of low cost and easy access can provide very interesting results (>100 V / V), which contributes to make the technology viable.

Sanitation and Drying of Sewage Sludge on Radiant Floors Using Solar Energy and Biogas: Comparison between Different Thicknesses of Deposited Mass

ABSTRACT Sewage sludge is a solid waste composed of water, rich in organic matter and nutrients, but concentrator of pathogenic microorganisms. Its use as agricultural fertilizer in the state of Paraná, Brazil is common. However, it is necessary to eliminate or significantly reduce microorganisms by means of a hygiene process. This can be obtained thermally, requiring a source of energy for heat generation. In this sense, a pilot system was constructed consisting of a stainless steel radiant floor, capable of transferring heat to the sewage sludge from coils coupled in base, through which the heated water circulates. The energy comes from solar radiation and is complemented by biogas from the anaerobic sewage treatment. Aiming to investigate the system's ability to transfer heat and, consequently, to sanitize and dry the sludge, a layer of 0.10 m was deposited on the radiant floor, the temperature being monitored at two different heights, obtaining averages of 328.95 K (55.8 ° C) and 336.95 K (63.8 ° C), respectively. The sludge was still submitted to a drying process, where a 68.68% increase in the total solids content was verified. Finally, the energy consumption was measured where a demand of 29.22 Nm³ of methane per m³ of treated sludge had been estimated.

Anaerobic co-digestion of animal manure at different waste cooking oil concentrations / Co-digestão anaeróbica de estrume animal em diferentes concentrações de óleo de descarte de cozinha

ABSTRACT: This study aimed to obtain the best dose of waste cooking oil inclusion for the co-digestion of substrates prepared with dairy cattle and swine manure in order to maximize solids reductions and biogas yield. Analyses of total solids (TS), volatile solids (VS), and neutral detergent fiber (NDF) were performed during the loading and unloading of digesters, while biogas yield was measured twice a week. The maximum reduction in VS (51.4%) was reached with the inclusion of up to 54.6g waste cooking oil.kg manure-1. Maximum NDF degradation occurred with inclusions of up to 69.4g waste cooking oil.kg manure-1. Inclusions of up to 64g of waste cooking oil.kg manure-1 provided specific biogas yield of 291.4 and 251.0L biogas.kg VS-1 added to substrates with swine and cattle manure, respectively. Adding oil at doses between 45.1 and 69.4g waste cooking oil kg manure-1 to substrates composed of cattle or swine manure maximizes reductions of solids and fibrous constituents and enhances specific biogas yield. Furthermore, swine manure supports higher doses of waste cooking oil.

RESUMO: Objetivou-se encontrar a melhor dose de inclusão de óleo residual durante a co-digestão de substratos preparados com dejetos de bovinos leiteiros e suínos, com o intuito de maximizar as reduções de sólidos e as produções de biogás. Foram realizadas no abastecimento e desabastecimento dos biodigestores as análises de sólidos totais (ST), sólidos voláteis (SV) e fibra em detergente neutro (FDN), enquanto as mensurações de biogás duas vezes por semana. A máxima redução de SV (51,4%) foi possibilitada pela inclusão de até 54,6g de óleo de descarte kg dejetos-1, já as máximas degradações de FDN ocorreram com adições de até 69,4g de óleo de descarte kg dejetos-1. As inclusões de até 64g de óleo de descarte kg dejetos-1 possibilitaram produções específicas de biogás de 291,4 e 251,0 L de biogás.kg SV-1 adicionado, para substratos contendo dejetos de suínos e bovinos respectivamente. A adição de óleo em doses entre 45,1 e 69,4g.kg-1 a substratos contendo dejetos de bovinos ou suínos maximiza as reduções dos constituintes sólidos e fibrosos bem como potencializa as produções específicas de biogás, sendo que o dejeto de suíno ainda suporta maiores doses de inclusão de óleo residual.

Análise da eficiência de modelos de decaimento de primeira ordem na previsão da emissão de gás de efeito estufa em aterros sanitários brasileiros / Analysis of the efficiency of first-order decay models in forecasting greenhouse gas emission in Brazilian sanitary landfills

RESUMO O objetivo deste artigo foi avaliar a eficiência de modelos de primeira ordem para previsão da geração de biogás em aterros sanitários, comparando resultados previstos com aqueles disponíveis em relatórios de monitoramento de captação ao longo de anos de operação. Os aterros sanitários estudados neste trabalho operam no âmbito de projetos de Mecanismo de Desenvolvimento Limpo (MDL), que podem receber incentivos financeiros - certificados de redução de emissões ou créditos de carbono. Foram selecionados quatro aterros sanitários brasileiros (Nova Iguaçu, Paulínia, Caieiras e Bandeirantes) que dispunham das quantidades anuais de resíduos sólidos efetivamente depositadas durante o primeiro período de crédito de sete anos, eliminando assim uma importante fonte de incertezas do modelo de previsão. Limitações dos modelos recomendados pelas diretrizes do Intergovernmental Panel on Climate Change (IPCC) são discutidas, incluindo erros intrínsecos na formulação matemática e de má interpretação no tempo para início da geração do biogás. É também proposta uma modificação na ferramenta de projeto CDM Tool atualmente utilizada em projetos MDL de emissão de biogás em depósitos de resíduos sólidos.

ABSTRACT The objective of this study was to evaluate the efficiency of first-order models for prediction of biogas emission in landfills, comparing forecasts with observations registered along the years of landfill operation. The landfills analyzed in this research operate within Clean Development Mechanism (CDM) that may receive financial incentives - certified emission reductions or carbon credits. Four Brazilian landfills (Nova Iguaçu, Paulinia, Caieiras and Bandeirantes) have been selected, for which the annual quantities of waste actually deposited during the first seven-year period of carbon credits were available, thus eliminating a major source of uncertainty in the forecasting models. Limitations of the models of the first order recommended by the guidelines of the Intergovernmental Panel on Climate Change (IPCC) are discussed, including intrinsic errors in the mathematical formulation and misinterpretation of the starting time for prediction of biogas emission. It is also proposed a modification in the CDM Tool model, currently used for biogas emission in solid waste deposits operating as CDM projects.

Desempenho ambiental da destinação e do tratamento de resíduos sólidos urbanos com reaproveitamento energético por meio da avaliação do ciclo de vida na Central de Tratamento de Resíduos - Caieiras / Environmental performance of the allocation and urban solid waste treatment with energetic reuse through life cycle assessment at CTR - Caieiras

RESUMO A principal destinação de resíduos sólidos urbanos (RSU) coletados no Brasil tem sido aterros controlados e sanitários. Em raros casos, são aplicadas outras soluções, que poderiam trazer benefícios adicionais para as localidades. O aproveitamento do RSU é uma alternativa promissora. De imediato, apresenta-se a alternativa de geração de energia elétrica. Nesse caso, embora não se trate de potencial com dimensão suficiente para sustentar uma estratégia de expansão da oferta de energia elétrica do país em longo prazo, a geração de eletricidade mediante RSU é elemento importante de uma estratégia regional ou local e, portanto, não deve ser desconsiderada. Nesse cenário, este trabalho procurou estudar a viabilidade de implementação de tecnologias alternativas e complementares de destinação de RSU com geração de energia elétrica, levando em consideração seus impactos ambientais e utilizando como ferramenta a Avaliação de Ciclo de Vida (AVC). Os resultados mostraram que, entre as alternativas levadas em conta neste estudo, a geração de energia elétrica por intermédio dos processos combinados de tratamento mecânico biológico e incineração é a mais atraente em termos de impactos ambientais. A geração de energia elétrica por meio do processo de incineração mass burning mostrou-se também atraente no tocante a impactos ambientais. Como conclusão geral deste estudo, identificou-se a existência de alternativas e oportunidades para a implementação de projetos relacionados à geração de energia elétrica no Brasil por RSU, especialmente pelo processo de incineração, embora ainda existam barreiras econômicas, políticas e sociais que precisam ser vencidas.

ABSTRACT The main destination of municipal solid waste (MSW) collected in Brazil has been landfills and sanitary landfills. In rare cases, other solutions are applied, which may bring additional benefits to localities. The use of MSW is a promising alternative. At once, it is an alternative of generating electricity. In this case, although it is not sufficient to support a strategy to expand the Brazilian electricity supply, in the long term, the generation of electricity through MSW is an important element of a regional or local strategy and therefore should not be disregarded. In that context, this study sought to study the feasibility of implementing alternative and complementary technologies for the disposal of MSW with generation of electricity, taking into account its environmental impacts and using the Life Cycle Assessment (LCA). The results showed that, among the alternatives taken into account in this study, the generation of electric energy by combined biological and mechanical Treatment and Incineration is the most attractive in terms of environmental impacts. The generation of electricity by means of the mass burning incineration process showed to be also attractive in terms of environmental impacts. As a general conclusion of this study it was identified the existence of alternatives and opportunities for implementation of projects related to the generation of electric energy in Brazil especially by the incineration process, although there are still economic, political and social needs that must be overcome.

Balanço de massa no tratamento de resíduos sólidos orgânicos provenientes de restaurantes em biorreator / Mass balance in the treatment of organic wastes from restaurants in bioreactor

RESUMO O tratamento de resíduos sólidos orgânicos por digestão anaeróbia é realizado por um consórcio de micro-organismos, no qual as archaea metanogênicas são as limitantes do processo, por serem mais sensíveis às mudanças nas condições do meio e possuírem crescimento lento. Para acompanhar a evolução do tratamento, algumas variáveis do processo de digestão anaeróbia são monitoradas, dentre elas, a demanda química de oxigênio (DQO), geralmente utilizada para estimar a matéria degradável e passível de ser convertida em biogás. Com o objetivo de avaliar a eficiência do processo de conversão de biomassa em metano, este artigo se baseou no balanço de massa adaptado da literatura, utilizando valores de DQO e volume de biogás gerado no reator anaeróbio, aqui chamado de biorreator. A produção de biogás foi monitorada diariamente utilizando o método de deslocamento de água, com o auxílio de um contador eletrônico. Com base no balanço de massa, o tratamento mostrou-se viável, visto que 50% da concentração de DQO que entrou no sistema foi convertida em gás metano. Comparando-se aos valores descritos na literatura, que se encontram na faixa de 50 a 70%, a eficiência do tratamento poderá ser elevada com ajustes nos parâmetros de controle que influenciam o processo de digestão anaeróbia, tais como manter a temperatura constante em 37°C e o pH e a alcalinidade equilibrados, o que poderá melhorar as condições do meio em todas as etapas de degradação da matéria orgânica e aumentar a conversão em gás metano.

ABSTRACT The treatment of organic solid waste by anaerobic digestion is carried out by a consortium of microorganisms, in which the methanogenic archaea bacteria are the limiting of the process because they are more sensitive to changes in environmental conditions and have slow growth. To monitor the treatment, some variables of anaerobic digester process are monitored, among them, the chemical oxygen demand (COD), usually used to estimate the degradable material and that can be converted into biogas. In order to evaluate the efficiency of biomass conversion process into methane, this article is based on adapted mass balance of the literature using COD values ​​and volume of biogas generated in anaerobic reactor, here called the bioreactor. Biogas production was monitored daily using the water displacement method, with the aid of an electronic counter.The treatment was satisfactory, based on mass balance, which showed that 50% of the amount of COD entered into the system was completely converted into methane gas. Comparing to the values described in the literature that are in the range of 50 to 70%, the treatment efficiency can be elevated with adjustments to control parameters which influence the process of anaerobic digestion, such as keep the temperature constant at 37°C and balanced pH and alkalinity, which can improve the environmental conditions at all stages of degradation of organic matter and increase conversion into methane gas.

Green conversion of municipal solid wastes into fuels and chemicals

Presently, the society is facing a serious challenge for the effective management of the increasing amount of produced municipal solid wastes. The accumulated waste has caused a series of environmental problems such as uncontrolled release of greenhouse gases. Moreover, the increasing amount of wastes has resulted in a shortage of areas available for waste disposal, resulting in a nonsustainable waste management. These problems led to serious public concerns, which in turn resulted in political actions aiming to reduce the amount of wastes reaching the environment. These actions aim to promote sustainable waste management solutions. The main objective of these policies is to promote the recycling of municipal solid waste and the conversion of waste to energy and valuable chemicals. These conversions can be performed using either biological (e.g., anaerobic digestion) or thermochemical processes (e.g., pyrolysis). Research efforts during the last years have been fruitful, and many publications demonstrated the effective conversation of municipal solid waste to energy and chemicals. These processes are discussed in the current review article together with the change of the waste policy that was implemented in the EU during the last years.