Viabilidade econômica da compostagem do lodo de esgoto para fins agrícolas
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Data
2019-06-13
Autores
Visentin, Roseli
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Universidade Estadual Paulista (Unesp)
Resumo
O uso do lodo de esgoto, um dos resíduos de efluentes do tratamento de esgoto, tem sido tema amplamente abordado sob os aspectos ambiental, legal e econômico. Isto se deve à sua crescente produção, consequência do aumento do serviço de saneamento básico e complexidade da composição do lodo de esgoto, rico em nitrogênio, porém com carga patogênica que deve ser eliminada por processo economicamente viável, permitindo seu uso à luz da legislação vigente. Um dos usos deste resíduo é o agrícola, que pelo processo de compostagem, quando associado com material estruturante, rico em carbono, propicia a eliminação de patógenos e homogeneização da mistura que recebe a denominação de fertilizante orgânico composto classe D, podendo, então, ser aplicado no solo e em culturas predeterminadas pelo Ministério da Agricultura, Pecuária e Abastecimento. O objetivo deste trabalho foi avaliar a viabilidade econômica da compostagem do lodo de esgoto produzido na Estação de Tratamento de Esgoto (ETE), localizada na Fazenda Experimental Lageado, no município de Botucatu, misturado com duas fontes de carbono: bagaço de cana-de-açúcar ou casca de eucalipto. A mistura permaneceu em estufa por dois meses, período em que foi revolvida por máquina compostadora, de acordo com parâmetros avaliados periodicamente, tais como a temperatura e umidade. A análise econômica deste projeto foi realizada com acompanhamento do processo, coleta de dados e elaboração de fluxos de caixa representados pela diferença entre o investimento em instalações e equipamentos, custos da operação de compostagem e as receitas de comercialização do fertilizante orgânico e da economia de custos com transporte e disposição do lodo de esgoto em aterro sanitário. Os indicadores Valor presente líquido (VPL), Taxa interna de retorno (TIR), Payback descontado (PBD) e Relação benefício custo (B/C) foram calculados para seis cenários: combinação de dois tipos de material estruturante e três fontes de receita. A alternativa mais viável foi a que utilizou bagaço de cana-de-açúcar, tomando-se como receita a comercialização do fertilizante orgânico e a economia de custos com o transporte e a disposição do lodo de esgoto em aterro sanitário. Os resultados desta combinação foram VPL de R$ 3.669.997, TIR igual a 84%, PBD de 1,3 anos e B/C de 2,83, demonstrando a viabilidade econômica do projeto.
The use of sewage sludge, a waste of the sewage treatment effluents, has been the subject widely discussed under environmental, legal and economic aspects. This is due to increasing to its production, as a result of the increase of the basic sanitation service, complexity of the composition of sewage sludge, rich in nitrogen, but with pathogenic load which must be eliminated by an economically viable process, allowing its use in light of the legislation in force. One of the uses of this residue is agriculture, which by the process of composting, when associated with structural material, rich in carbon, promotes the elimination of pathogens and homogenization of the mixture that receives the title of organic compound fertilizer class D, which may then be applied in the soil and in predetermined cultures by the Ministry of Agriculture, Livestock and Supply. The objective of this work was to evaluate the economic viability of composting of sewage sludge produced at Sewage Treatment Station (STS) located at the Experimental Farm Lageado, in the city of Botucatu, mixed with two carbon sources: sugarcane bagasse and eucalyptus bark. The mixture remained in the greenhouse for two months, during which time it was stirred by composter machine, according to periodically evaluated parameters, such as temperature, humidity. The economic analysis of this project was accomplished with the process monitoring, data collection and preparation of cash flows represented by the difference between the investment in plant and equipment, composting operation costs and revenues from marketing of organic fertilizer and the cost savings with transport and disposal of sewage sludge in landfill. The indicators Net present value (NPV), Internal rate of return (IRR), Discounted payback period (DPP) and Benefit- cost ratio (BCR) were calculated for six scenarios: a combination of two types of structural material and three sources of revenue. The most viable alternative was the used sugarcane bagasse, taking as revenue of the commercialization of the organic fertilizer and the cost savings with the transport and disposal of sewage sludge in sanitary landfill. The results of this combination were NPV R$ 3.669.997, IRR equal to 84%, DPP of 1.3 years and BCR of 2.83, demonstrating the economic viability of the project.
The use of sewage sludge, a waste of the sewage treatment effluents, has been the subject widely discussed under environmental, legal and economic aspects. This is due to increasing to its production, as a result of the increase of the basic sanitation service, complexity of the composition of sewage sludge, rich in nitrogen, but with pathogenic load which must be eliminated by an economically viable process, allowing its use in light of the legislation in force. One of the uses of this residue is agriculture, which by the process of composting, when associated with structural material, rich in carbon, promotes the elimination of pathogens and homogenization of the mixture that receives the title of organic compound fertilizer class D, which may then be applied in the soil and in predetermined cultures by the Ministry of Agriculture, Livestock and Supply. The objective of this work was to evaluate the economic viability of composting of sewage sludge produced at Sewage Treatment Station (STS) located at the Experimental Farm Lageado, in the city of Botucatu, mixed with two carbon sources: sugarcane bagasse and eucalyptus bark. The mixture remained in the greenhouse for two months, during which time it was stirred by composter machine, according to periodically evaluated parameters, such as temperature, humidity. The economic analysis of this project was accomplished with the process monitoring, data collection and preparation of cash flows represented by the difference between the investment in plant and equipment, composting operation costs and revenues from marketing of organic fertilizer and the cost savings with transport and disposal of sewage sludge in landfill. The indicators Net present value (NPV), Internal rate of return (IRR), Discounted payback period (DPP) and Benefit- cost ratio (BCR) were calculated for six scenarios: a combination of two types of structural material and three sources of revenue. The most viable alternative was the used sugarcane bagasse, taking as revenue of the commercialization of the organic fertilizer and the cost savings with the transport and disposal of sewage sludge in sanitary landfill. The results of this combination were NPV R$ 3.669.997, IRR equal to 84%, DPP of 1.3 years and BCR of 2.83, demonstrating the economic viability of the project.
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Palavras-chave
Adubação orgânica, Benefício econômico, Saneamento básico, Organic fertilizing, Economic benefit, Basic sanitation