Volatile fatty acids production from food wastes for biorefinery platforms: A review

Abstract

Volatile fatty acids (VFAs) are a class of largely used compounds in the chemical industry, serving as starting molecules for bioenergy production and for the synthesis of a variety of products, such as biopolymers, reduced chemicals and derivatives. Because of the huge amounts of food waste generated from household and processing industry, 47 and 17 million tons per year respectively only in the EU-28 Countries, food wastes can be the right candidate for volatile fatty acids production. This review investigates all the major topics involved in the optimization of VFAs production from food wastes. Regarding the best operative conditions for the anaerobic fermenter controlled pH in the neutral range (6.0-7.0), short HRT (lower than 10 days), thermophilic temperatures and an organic loading rate of about 10 kgVS/md, allowed for an increase in the VFAs concentration between 10 and 25%. It was also found that additions of mineral acids, from 0.5 to 3.0%, and thermal pretreatment in the range 140-170 °C increase the organic matter solubilisation. Applications of VFAs considered in this study were biofuels and bioplastics production as well as nutrients removal in biological wastewater treatment processes.

The Future Agricultural Biogas Plant in Germany: A Vision

“…Residues from industrial crop cultivation and processing can also be used as feedstocks for anaerobic digestion [199]. Another option is to separate metabolic intermediates of the anaerobic digestion process such as volatile fatty acids to produce biochemicals [200]. In a future bioeconomy, anaerobic digestion could also gain in importance for the degradation and energy recovery from bioproducts after their use [201].…”

Volatile fatty acids as novel building blocks for oil‐based chemistry via oleaginous yeast fermentation

“…These chemicals can be further used as carbon sources for oleaginous yeasts, which accumulate lipids in lipid bodies (LBs; Figure 1). Nevertheless, to enhance VFA production, attention must be directed to different aspects regarding the substrate used and the operational conditions in the AD process (Magdalena, Llamas, Tomás-Pejó, & González-Fernández, 2019;Strazzera, Battista, Garcia, Frison, & Bolzonella, 2018).…”

Inoculum Source Determines Acetate and Lactate Production during Anaerobic Digestion of Sewage Sludge and Food Waste

“…These differences in reaction speed and pH optimum allow AD to be divided into two separate production steps, where H 2 and VFA are generated in a primary acid reactor and bio-methane in a secondary reactor. This two-stage approach has been shown to optimize the overall AD process and increase methane yield [3][4][5][6][7][8]. It also allows additional applications, such as the production of bio-hydrogen or of a range of VFA that can be extracted and used as "green" chemical feedstock for further conversion [8,9].…”

“…This two-stage approach has been shown to optimize the overall AD process and increase methane yield [3][4][5][6][7][8]. It also allows additional applications, such as the production of bio-hydrogen or of a range of VFA that can be extracted and used as "green" chemical feedstock for further conversion [8,9]. The typical VFA composition in an acidic AD reactor is a mixture dominated by acetate, propionate, butyrate, and valerate [10-13], but it can also be dominated by acetate, butyrate, and H 2 [14], or mainly consist of lactate and/or acetate [15,16].…”

“…In a single-stage process, a low level of hydrogen is ensured by the activity of hydrogenotrophic methanogens. In a hydrolysis reactor with no or low methanogenic activity, hydrogen could potentially be both produced and consumed by different groups of acetogens.Knowledge on acid production per se is quite good as it has been studied in many different processes for both single compounds and complex materials and with both single and mixed cultures of microorganisms [8,17,25]. However, less is known about how to direct the process towards the production of a specific VFA from a complex substrate matrix, such as food waste or sewage sludge, owing to the complexity of AD and the wide number of different possible pathways.…”