Substituição gradativa de sacarose pela fração líquida de resíduos de frutas e verduras em reator anaeróbio de leito fluidificado

Abstract

Proper management of fruit and vegetable waste (FVW) generated in Food Supply Centers (Ceasa) is an environmental and economic challenge. Dark fermentation (DF) emerges as a promising alternative for the valorization of these wastes, converting them into bio-hydrogen and organic acids (FAs). Among the reactors used, the anaerobic fluidized bed reactor (AFBR) stands out for its high biomass retention rate and capacity to support high organic loads. However, the literature lacks systematic studies on the adaptation and stability of AFBRs operating with complex substrates such as the liquid fraction of fruit and vegetable waste (LFVW). Given this, this dissertation evaluated the performance of a hydrocarbon-based reactor (RALF) in hydrogen production, subjected to a progressive increase in the concentration of volatile fatty acids (VFA) (0 to 100%) in the substrate, replacing sucrose, under mesophilic conditions (30 °C), with a hydraulic retention time (HRT) of 2 h, and a constant volumetric organic loading rate (LOR) of 60 kg COD m reactor -3 d -1 , without pH control. Under the 100% sucrose condition, the volumetric hydrogen production (HVP) and yield (YH) were 4361 mL H2 L reactor -1 d -1

and 2.6 mmol H2 g

-1 COD applied, respectively. With complete replacement by VFA (100%), a sharp decline was observed, with HVP and YH reaching only 261 mL H2 L reactor -1 d -1 and 0.2 mmol H2 g

-1 COD applied. This decrease was associated with a change in the metabolic profile of the microbial community, with an accumulation of propionic acid (APr) coupled with a consistently acidic pH (range of 4.0 and 4.3), which suppressed H2 producing bacteria and diverted carbon flow to acidogenic H2-consuming pathways such as propionogenesis and homoacetogenesis. However, integrated analysis with literature data demonstrated that the complex nature of FLRFV is not an absolute limiting factor. Operating the RALF with shorter HRTs (1 h) and higher VOCs (240 kg COD m reactor -3 d -

1 ) proved to be an effective strategy to reverse this scenario, establishing a butyric metabolic pathway and increasing PVH by up to 35 times. Therefore, the viability of FLRFV for bio-hydrogen production is intrinsically linked to an optimal operating window of HRT/VOC, which exerts selective pressure favorable to hydrogenogenic bacteria, overcoming the initial complexity of the residue.