Aplicação de resíduo do processamento industrial da goiaba em reatores anaeróbios para produção de bioprodutos de valor agregado
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Data
2022-03-07
Autores
Carvalho Júnior, Romário Pereira de
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Universidade Estadual Paulista (Unesp)
Resumo
A fruticultura tem grande importância para a economia brasileira, tendo em vista o consumo, industrialização e exportação. A goiaba contribui com a produção nacional anual total de 44 milhões de toneladas de frutas. Entretanto, a quantidade de resíduos gerados no seu processamento industrial é elevada. Os resíduos agroindustriais são altamente poluidores e devem ser tratados para redução de matéria orgânica previamente à sua disposição final. A digestão anaeróbia pode ocorrer em dois estágios, permitindo a produção de biohidrogênio, AGVs, álcoois e biometano a partir de tais resíduos. O presente trabalho avaliou o potencial do resíduo do processamento da goiaba em reatores anaeróbios operados em batelada, em codigestão com esgoto sanitário, visando determinar condições ótimas para produção de bioprodutos e identificar os microrganismos envolvidos no processo. Quatro ensaios foram realizados num sistema anaeróbio em dois estágios, com diferentes relações S/I (substrato/inóculo) (0,67, 1,0, 2,0 e 3,0 g DQO g-1 SV), em triplicata de reatores em batelada (1 L), headspace (0,3 L, N2 99,99%), a 37ºC e a 120 rpm. Primeiro estágio: resíduo, esgoto sanitário, inóculo pré-tratado e pH inicial de 5,5; segundo estágio: efluente do primeiro estágio, lodo granular anaeróbio de reator UASB e pH inicial de 7,0. Além disso, foi realizada a digestão anaeróbia em único estágio (relação S/I de 1,0). No sistema em dois estágios, o melhor rendimento de H2 foi obtido na relação S/I de 0,67 (5,26 mL H2 g-1 SV) e de CH4 nas relações S/I de 0,67 e de 1,0 (266,27 e 256,88 mL CH4 g-1 SV, respectivamente). Na relação S/I de 0,67, o ácido acético foi o principal metabólito gerado (0,96 g DQO L-1). Ao se aumentar a relação S/I, a rota metabólica predominante foi a do propionato e houve acúmulo de ácido valérico. Paraclostridium e Clostridium foram os gêneros dominantes no estágio acidogênico, enquanto gêneros de arqueias acetoclásticas e hidrogenotróficas foram identificados no estágio metanogênico. O sistema em dois estágios proporcionou produção acumulada de metano 21% maior do que em único estágio. Estudo de superfície de resposta foi desenvolvido para otimização da fermentação escura, para maximizar os rendimentos de H2 e de metabólitos, além da remoção de carboidratos. Para isso, 15 condições foram testadas em duplicata de reatores anaeróbios (100 mL) com resíduo da goiaba, esgoto sanitário e lodo granular pré-tratado, variando relação S/I, temperatura e pH inicial. Os três fatores analisados influenciaram a fermentação escura do resíduo. A melhor recuperação energética foi verificada para relação S/I de 0,3, em pH inicial de 6,79 e a 49,8ºC, com 78% na remoção de carboidratos, gerações de metabólitos de 715,21 mg DQO g-1 SV e rendimentos de 0,21 mmol H2 mmol-1 Carb. Ácidos acético e butírico foram os principais metabólitos gerados. Novas possibilidades foram abertas para a valorização do resíduo da goiaba, objetivando sua destinação sustentável.
Brazilian fruit farming has great importance to the economy, with its consumption, industrialization, and exportation. Guava contributes to the annual production of around 44 million tons of fruit. The waste quantity generated on industrial processing is elevated. The agro-industrial wastes are highly polluting and need to be treated before their final disposal. Anaerobic digestion can occur in two stages, allowing the biohydrogen, VFAs, alcohols, and biomethane production from these wastes. The present study evaluated the guava processing waste potential in anaerobic batch reactors, in co-digestion with sanitary sewage aiming to determine the optimal conditions for these bioproducts production and identify the microorganisms involved in the process. Four essays were carried out in a two-stage anaerobic system, with different S/I (substrate/inoculum) ratios (0.67, 1.0 2.0, 3.0 g COD g-1 VS), in triplicate of batch reactors (1L), headspace (0.3 L, N2 99.99%), under 37ºC and 120 rpm. First stage: guava processing waste, granular sludge heat-treated previously, and initial pH 5.5; second stage: first stage effluent, anaerobic sludge from UASB reactor, and initial pH 7.0. Moreover, the anaerobic digestion in one stage (S/I ratio of 1.0) was done. On the two-stage system, the best H2 yield was obtained in the S/I ratio of 0.67 (5.25 mL H2 g-1 SV) and the S/I ratios of 0.67 and 1.0 for CH4 yield (266.27 and 256.88 mL CH4 g-1 SV, respectively). In the S/I ratio of 0.67, acetic acid was the main metabolite generated (0.96 g COD L-1). With the increase of the S/I ratio, the predominant metabolic pathway was propionate and had valeric acid accumulation. Paraclostridium and Clostridium were the dominant genera on the acidogenic stage, while acetoclastic and hydrogenotrophic archaea genera were identified on the methanogenic stage. The two-stage system allowed CH4 accumulated production 21% higher than for just one stage. Response surface study was elaborate for dark fermentation optimization, to maximize the H2 and metabolites yields, besides carbohydrates removal. To do this, 15 conditions were tested in duplicate of anaerobic batch (100 mL) with the guava waste, sanitary sewage, and granular sludge heat-treated, varying S/I ratio, temperature, and initial pH. The three factors analyzed influenced the dark fermentation of the waste. The best recuperation was in the S/I ratio of 0.3, initial pH of 6.79 and 49.8 °C, with 78% of carbohydrate removal, metabolites generation of 715.21 mg COD g-1 SV and yield of 0.21 mmol H2 mmol-1 Carb. Acetic and butyric acids were the main metabolites generated. New possibilities are open for guava waste valorization, aiming at its sustainable destination.
Brazilian fruit farming has great importance to the economy, with its consumption, industrialization, and exportation. Guava contributes to the annual production of around 44 million tons of fruit. The waste quantity generated on industrial processing is elevated. The agro-industrial wastes are highly polluting and need to be treated before their final disposal. Anaerobic digestion can occur in two stages, allowing the biohydrogen, VFAs, alcohols, and biomethane production from these wastes. The present study evaluated the guava processing waste potential in anaerobic batch reactors, in co-digestion with sanitary sewage aiming to determine the optimal conditions for these bioproducts production and identify the microorganisms involved in the process. Four essays were carried out in a two-stage anaerobic system, with different S/I (substrate/inoculum) ratios (0.67, 1.0 2.0, 3.0 g COD g-1 VS), in triplicate of batch reactors (1L), headspace (0.3 L, N2 99.99%), under 37ºC and 120 rpm. First stage: guava processing waste, granular sludge heat-treated previously, and initial pH 5.5; second stage: first stage effluent, anaerobic sludge from UASB reactor, and initial pH 7.0. Moreover, the anaerobic digestion in one stage (S/I ratio of 1.0) was done. On the two-stage system, the best H2 yield was obtained in the S/I ratio of 0.67 (5.25 mL H2 g-1 SV) and the S/I ratios of 0.67 and 1.0 for CH4 yield (266.27 and 256.88 mL CH4 g-1 SV, respectively). In the S/I ratio of 0.67, acetic acid was the main metabolite generated (0.96 g COD L-1). With the increase of the S/I ratio, the predominant metabolic pathway was propionate and had valeric acid accumulation. Paraclostridium and Clostridium were the dominant genera on the acidogenic stage, while acetoclastic and hydrogenotrophic archaea genera were identified on the methanogenic stage. The two-stage system allowed CH4 accumulated production 21% higher than for just one stage. Response surface study was elaborate for dark fermentation optimization, to maximize the H2 and metabolites yields, besides carbohydrates removal. To do this, 15 conditions were tested in duplicate of anaerobic batch (100 mL) with the guava waste, sanitary sewage, and granular sludge heat-treated, varying S/I ratio, temperature, and initial pH. The three factors analyzed influenced the dark fermentation of the waste. The best recuperation was in the S/I ratio of 0.3, initial pH of 6.79 and 49.8 °C, with 78% of carbohydrate removal, metabolites generation of 715.21 mg COD g-1 SV and yield of 0.21 mmol H2 mmol-1 Carb. Acetic and butyric acids were the main metabolites generated. New possibilities are open for guava waste valorization, aiming at its sustainable destination.
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Biorreatores, Hidrogênio, Metano, Ácidos graxos, Resíduos orgânicos - Reaproveitamento