Biotechnological valorisation of biowaste using biochar

• Autor(a) principal: Costa, Ana Lúcia Oliveira
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/40169
• topic: Biochar; Anaerobic digestion; Biogas; Bio-waste; Food waste

Historically, anaerobic digestion (AD) is a process with great relevance in the management and treatment of biodegradable waste, simultaneously allowing the generation of fuels from renewable sources (biomethane and bio-hydrogen). Currently, efforts have been made to optimize this process in the context of the Circular Economy. One of the possibilities with great interest is the use of biochar - carbonaceous material produced from the pyrolysis of biomass in AD processes. The main objective of this work is to assess the benefits of biochar in anaerobic digestion processes of bio-waste from food origin. For this purpose, experimental tests were carried out in batch reactors, varying the following parameters: food-to-microorganisms ratio (F/M = 0.5; 1; and 2 g/g); biochar concentration (0, 2.5 and 5 g/L) and biochar particle size (<2 mm – S; and >2 mm – L). It was found that the degradation of volatile solids occurred in most of tests, with the highest removal efficiencies being observed in tests at the F/M ratio = 2 g/g, with the addition of biochar not having a significant influence on removal. Regarding the removal of soluble chemical oxygen demand (sCOD), the effect of adding biochar was quite visible, in particular under operating conditions of F/M = 2 g/g and particle biochar concentration S at 5 g/L, yielding a 62% substrate removal efficiency. The quantification of bioavailable phosphorus and Kjeldahl nitrogen in the digestate after the tests demonstrated its agronomic potential, reaching concentrations of up to = 54 mg P /L and 55 mg N /L. However, the addition of biochar was not relevant in the concentration of these elements in the digestate. Biogas production increased directly with the F/M ratio, especially at lower concentrations of biochar (2.5 g/L), with the particle size factor being of little relevance. It is recommended that tests with high F/M ratios should be extended beyond 21 days to maximize COD degradation and biogas production.