Volatile fatty acids (VFAs) and methane from food waste and cow slurry: Comparison of biogas and VFA fermentation processes

Abstract

The potential of various biomasses for the production of green chemicals is currently one of the key topics in the field of the circular economy. Volatile fatty acids (VFAs) are intermediates in the methane formation pathway of anaerobic digestion and they can be produced in similar reactors as biogas to increase the productivity of a digestion plant, as VFAs have more varying end uses compared to biogas and methane. In this study, the aim was to assess the biogas and VFA production of food waste (FW) and cow slurry (CS) using the anaerobic biogas plant inoculum treating the corresponding substrates. The biogas and VFA production of both biomasses were studied in identical batch scale laboratory conditions while the process performance was assessed with chemical and microbial analyses. As a result, FW and CS were shown to have different chemical performances and microbial dynamics in both VFA and biogas processes. FW as a substrate showed higher yields in both processes (435 ml CH4/g VSfed and 434 mg VFA/g VSfed) due to its characteristics (pH, organic composition, microbial communities), and thus, the vast volume of CS makes it also a relevant substrate for VFA and biogas production. In this study, VFA profiles were highly dependent on the substrate and inoculum characteristics, while orders Clostridiales and Lactobacillales were connected with high VFA and butyric acid production with FW as a substrate. In conclusion, anaerobic digestion supports the implementation of the waste management hierarchy as it enables the production of renewable green chemicals from both urban and rural waste materials.

Anaerobic Digestion Performance: Separate Collected vs. Mechanical Segregated Organic Fractions of Municipal Solid Waste as Feedstock

“…The organic waste in the study of Owusu-Agyeman et al [35] consisted of alcohol and soda beverage, food, dairy, fruit, fat, and oil waste. Tampio et al [36] reported that the acetic acid fraction dominated only in the first period of the anaerobic digestion of food waste, which was then surpassed by butyric acid. Additionally, in this case, mesophilic conditions (37 • C) [36] could be considered as a plausible explanation for the obtained difference.…”

“…Tampio et al [36] reported that the acetic acid fraction dominated only in the first period of the anaerobic digestion of food waste, which was then surpassed by butyric acid. Additionally, in this case, mesophilic conditions (37 • C) [36] could be considered as a plausible explanation for the obtained difference. The butyric and valeric acid contents were at deficient levels during AD ( Figure 4c) and did not go beyond 10 mg/kg even in the inlet section.…”

Bioengineering of anaerobic digestion for volatile fatty acids, hydrogen or methane production: A critical review

“…The contact of the activated spore with certain germinant, such as L-alanine, L-asparagine, and L-valine, induces the second stage generally regarded as germination. New growing cells are then formed in the final stage of outgrowth [146,151,152].…”

Identification of new critical points for logistics model in cumulative methane yield curves after co‐digestion of apple pulp and chicken manure with sulphuric acid pretreatment and a new modelling study

“…The x ‐axis values of the PIs of the pretreated reactors varied between 6.64 and 7.04. At this stage of digestion, the accumulation of volatile fatty acids can have a negative effect on the bacteria . Therefore, ensuring proper pH control in the process between PAM and PI can increase the production efficiency and the curve length between these two points.…”