Evaluation of optimal fermentation conditions for volatile fatty acids production from artisanal fish waste

Abstract

In this research, operational parameters were assessed to optimise the production of volatile fatty acids (VFA) from artisanal fish waste (FW) using mixed-culture fermentation. The experiments were performed using a randomised block design with pH and Inoculum/Substrate (I/S) ratio as factors with three pH levels (5, 7 and 9) and five I/S ratios levels (0.20, 0.15, 0.10, 0.05, 0.00) with VFA production, total ammonia nitrogen (TAN), biogas and soluble chemical oxygen demand (sCOD) as response variables. The results indicated that pH and I/S ratio significantly influenced VFA production and the other variables evaluated. The highest VFA concentration (54.5 g/L) was obtained at pH 7 and with an I/S ratio of 0.05. These conditions were also optimal for TAN and sCOD. External pH control was proved as unnecessary as the highest VFA production (70.3 g VFA/L) was obtained without pH control. In these conditions, the fermentation broth was able to maintain its pH between 6.6 and 7.7. The VFA profile had acetic (35%) and butyric (32%) acids as the dominant species and propionic, iso-valeric and iso-butyric were minor species (< 10%). An economic assessment evaluating the establishment of a FW VFA biorefinery in Tumaco, Colombia was performed including capital, operational and labour cost, discounted payback period and cost curves. These results evidenced the potential of artisanal FW as a raw material for producing high concentrations of VFA and smooth the path for the establishment of a VFA and biogas biorefinery from FW.

Production of Poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate) by <em>Bacillus megaterium</em> LVN01 Using Biogas Digestate

“…In this sense, researchers have directed their attention to strengthening VFA production, as a collateral product of biogas production [17]. Colombian researchers reported an interesting work in which they take advantage of fishing waste for this purpose, with which digestate rich in VFA is also obtained [18].…”

“…In Colombia, artisanal fishing supplies around 12,000 tons of fish/year to the national market, 8% of the total capture fishery in the country. It is estimated that 45% of the total catch by artisanal fishing becomes waste [18,21], which produces serious economic losses for this sector and environmental problems associated with the inadequate disposal of waste. In Colombia, waste fishing boats are thrown directly into the ocean or taken to land [18].…”

“…It is estimated that 45% of the total catch by artisanal fishing becomes waste [18,21], which produces serious economic losses for this sector and environmental problems associated with the inadequate disposal of waste. In Colombia, waste fishing boats are thrown directly into the ocean or taken to land [18]. The results of the research showed that the digestate has great potential as a sustainable substrate for the industrial production of PHA, while there is permanent availability of the starting material, giving added value to fishing waste.…”