Energy Generation with Landfill Biogas

Transcription

1 Artigo publicado e apresentado no evento RIO 6 - World Climate & Energy Event, 17a 18 de novembro de 2006, Rio de Janeiro. Energy Generation with Landfill Biogas Coelho, Suani Teixeira 1 ; [email protected] Velázquez, Sílvia Maria Stortini González 1 ; [email protected] Pecora, Vanessa 1 ; [email protected] Abreu, Fernando Castro 1. [email protected] 1 USP University of Sao Paulo IEE/CENBIO Electrotechnical and Energy Institute / Brazilian National Biomass Reference Center. Av. Prof. Luciano Gualberto, 1289 CEP São Paulo SP Brasil Fone: Fax: ABSTRACT: Purpose: The project s objective is to implement a system of electric energy generation and illumination by gas proceeding from a sanitary landfill, called landfill biogas. The purpose is to evaluate the potential of electric energy generation and illumination, which s development, is a commitment of the Electrotechnical and Energy Institute / Brazilian National Biomass Reference Center (IEE/CENBIO) and is financially supported by the Ministry of Mines and Energy (MME). Development: The landfill biogas results from organic material anaerobic fermentation and its chemical composition depends on several parameters, such as the disposal criterion employed and the kind of organic material. The most important biogas components are methane (CH 4 ), carbon dioxide (CO 2 ) and sulfuric components (H 2 S). The biogas composition is an essential parameter, because it allows identifying the appropriate purification system, which aims to remove sulfuric gases and decrease the water volume, contributing to improve the combustion fuel conditions. Conclusion: This project is currently under development and the results obtained will provide information about landfill s operational conditions, and defining appropriate areas where this project could be applicable. The most important environmental contribution associated to this project is the mitigation of greenhouse gases (GHG) emissions, especially verified trough methane conversion in carbon dioxide, which presents dangerous level around twenty five times lower than methane. Keywords: landfill, biogas, anaerobic fermentation, greenhouse gases, energy generation.

2 1. Introduction The project proposal of landfill biogas use as fuel to produce electric energy, which development is a commitment of CENBIO (Brazilian National Biomass Reference Center), as well as promote local illumination by gaslight. It allows new perspectives to renewable energy employment in Brazil. According to the National Research of Basic Sanitation PNSB (2000), in Brazil tones of solid wastes are daily collected. From these residues tones are domiciliary. Table 1 presents the Brazilian population and its regional distribution, as well as the amount of solid waste daily generated and its generation by people and by region. Table 1 Estimative of Solid Waste Generation in Brazil Solid Wastes Total Population Generation (ton/day) Value Percent Value Percent Percapita Generation (kg/hab/day) Brazil ,35 North , ,8 0,86 Northeast , ,2 0,87 Southeast , ,96 South , ,7 0,79 West-Center , ,3 1,23 Source: PNSB (IGBE, 2000) Related to the residues generation by people, an expressive difference between regions can be seen, it is caused by the non domiciliary percentage of waste. In Brazil, as in many developing countries, the biggest part of solid waste generation is deposited without any methodology. In this context, CENBIO is looking for a sanitary landfill, which has all the information needed to develop the proposed project. Also, the sanitary landfill has to have a good infrastructure that guarantees the quality of the biogas itself. 2. Biogas Generation The biogas results from organic material anaerobic fermentation and its chemical composition depends on several parameters, such as the methodology employed and the kind of organic material. Anyway, the most important biogas components are methane (CH 4 ), carbon dioxide (CO 2 ) and sulfuric components (H 2 S). The biogas production involves three steps: fermentation, which includes hydrolysis and acid genesis, acetone genesis e methane genesis.

3 In the fermentation process, during the hydrolysis the organic material is converted in smaller molecules and this material is transformed in soluble acids by acidogenesis process. After that it is initiated the acetanogenese process, transforming the products obtained in the first step in acetic acid, hydrogen and carbon dioxide. The last step is referent to metanogenese process, through anaerobic bacteria action, producing methane gas. The biogas composition is an essential parameter, because it allows identifying the appropriate purification system, which aims to remove sulfuric gases and decreasing the water volume, contributing to improve the combustion fuel conditions. Other data obtained from biogas analysis reffers to the low heat value that combined to the efficiency and biogas consumption is important to estimate the electric generation potential. 3. Energy Generation There are different kinds of technology to convert the chemical energy in the biogas into electricity. Energy conversion means a process where one type of energy is converted to another. In biogas conversion the chemical energy in the molecules is converted to mechanical energy in a controlled combustion system, then, this mechanical energy activates a generator producing electrical power. The gas turbines and the internal combustion engines are the most common technologies used to this kind of energy conversion. Figure 1 illustrates these technologies. Some characteristics of these technologies are show in Table 3. Figure 1 Engines, gas turbines and microturbines technologies, commercially available (CENBIO, 2002) Table 3 Comercial Technologies Characteristics (CENBIO, 2003) Power Efficiency Nox Emissions Natural Gas Engines (Ciclo Otto) 30 kw 20 MW 30 % - 40 % 250 ppm 3,000 ppm Natural Gas Turbines 500 kw 150 MW 20 % - 30 % Microturbines (Small Scale) 35 ppm 50 ppm (Landfill Gas) 30 kw 100 kw 24 % - 28 % < 9 ppm

4 Even so, in general, engines are more efficient turbines may be more efficient when operating in a cogeneration cycle producing heat and electricity (COSTA et al., 2001). Aiming to evaluate the technology efficiency a biogas cleaning system will be installed. The biogas analyses results before and after the generation system will be compared so the technical, economic and environmental terms can be concluded. For the illumination by direct biogas burn, the possibilities are being studied. 4. Sanitary Landfill in Brazil It can be seen in table 1 the amount of sanitary landfill in Brazil, as well as its distribution. Table 1 Implemented and Distributed Sanitary Landfill in Brazil Sanitary Landfill in: n Sanitary Landfill Garbage Amount (ton/day) Brazil ,3 North ,8 Northeast ,1 Maranhão São Luís Metropolitan Region Grande São Luís Piauí 3 90,8 Teresina 1 62,8 Ceará ,5 Fortaleza Metropolitan Region of Fortaleza Rio Grande do Norte 5 219,6 Natal - - Metropolitan Region of Natal 1 40 Paraíba 5 67,1 João Pessoa - Pernambuco ,3 Recife Metropolitan Region of Recife ,3 Alagoas Maceió - - Metropolitan Region of Maceió - - Sergipe Aracaju - Bahia ,8 Salvador ,5 Metropolitan Region of Salvador ,3 Southeast ,3 Minas Gerais ,8 Belo Horizonte ,6

5 Metropolitan Region of Belo Horizonte ,6 Metropolitan Region Vale do Aço Sanitary Landfill in: n Sanitary Landfill Garbage Amount (ton/day) Espírito Santo ,6 Vitória Metropolitan Region Grande Vitória ,5 Rio de Janeiro ,1 Rio de Janeiro Metropolitan Region of Rio de Janeiro São Paulo ,8 São Paulo ,5 Metropolitan Region of de São Paulo ,7 Metropolitan Region Baixada Santista ,5 Metropolitan Region of Campinas ,1 South West-Center ,1 Mato Grosso do Sul ,2 Campo Grande - - Mato Grosso ,3 Cuiabá Goiás ,6 Goiânia Metropolitan Region of Goiânia Distrito Federal - - Brasília - - Integrated Region of Developing of Federal District and Surround ,7 Source: IBGE, From those data CENBIO is looking for a sanitary landfill close to CENBIO s location. 5. Results Until now, the identification of the sanitary landfills has been made; the next step will be the selection of the best sanitary landfill (SL). This selection is being made through visits that the CENBIO s integrants are making on the SL possibilities. 6. Conclusions Despite the fact that this project will be developed experimentally (small scale), one of the expectations is that the results obtained provide information about the biogas utilization operational conditions. This allows defining appropriate areas where this project could be applicable.

6 Especially in metropolitans SL, the use of landfill biogas as fuel to produce electric energy is able to contribute with electrification programs already structured in Brazil. Focusing the social aspects, the implementation of this project also increases the job offering, the residues treatment. It creates important benefits to the country, as lower expending of fossil fuel importation so it is a good investment. The most important environmental contribution associated to this project is the mitigation of greenhouse gases (GHG) emissions, especially verified trough methane conversion in carbon dioxide, which presents a dangerous level around twenty one times lower than methane. 7. References CAPSTONE. Authorized Service Provider Training Manual Capstone Turbine Corporation, Los Angeles, CENBIO. Nota Técnica VII - Geração de Energia a Partir do Biogás Gerado por Resíduos Urbanos e Rurais, São Paulo, CENBIO. Relatórios de Atividades Projeto ENERG-BIOG, São Paulo, COSTA et al. Produção de Energia Elétrica a partir de Resíduos Sólidos Urbanos, Trabalho de Graduação Interdisciplinar/FAAP, São Paulo, IBGE. Instituto Brasileiro de Geografia e Estatística, Brasil, 2000.