Enhanced Anaerobic Performances of Kitchen Wastes in a Semi-Continuous Reactor by EDTA Improving the Water-Soluble Fraction of Fe

Abstract

The addition of Fe2+ is considered an effective method for increasing methane production, but the added Fe2+ may not be absorbed by anaerobic microorganisms due to complex chemical reactions. In this study, ethylenediaminetetraacetic acid (EDTA) was used as a ligand of Fe2+ (EDTA-Fe) to promote the dissolution of Fe, and the anaerobic performances of kitchen wastes (KWs) in a semi-continuous reactor were studied. The results indicated that the biogas yields and methane contents were enhanced to 594–613 mL·g−1VSadd·d−1 and 63.6–64.4% at an organic loading rate (OLR) of 2.5 gVSadd·L−1·d−1 due to EDTA-Fe addition. Simultaneously, the EDTA-Fe was more effective than Fe2+ in preventing the acidification of KWs with a high OLR (5.0 gVSadd·L−1·d−1). In addition, the sequential extraction results showed that the water-soluble fraction of Fe in the R3 (EDTA-Fe addition) was 1.49-fold of that in the R2 with Fe2+ addition. The contents of coenzymes F420 and F430 were also improved 1.09 and 1.11 times, respectively. Mechanism analysis confirmed that the EDTA enhanced methane production and operational stability by promoting the dissolution of Fe and maintaining a high content of water-soluble Fe.

Processes for Bioenergy and Resources Recovery from Biowaste

“…The Special Issue showcases ten full-length original research articles [13][14][15][16][17][18][19][20][21][22], one short communication [23], and one review article [24] covering different aspects of various processes for bioenergy and resource recovery from biowaste. Specifically, the accepted manuscripts covered a range of essential topics in the areas of anaerobic digestion, microbial fermentation, and thermochemical conversion targeting various value-added resources, including biogas, syngas, bio-oil, and organic acids ( Figure 1).…”

“…Among the published articles, multiple articles presented different fundamental and applied aspects of anaerobic digestion for biogas production. Liu et al [22] proposed the co-supplementation of ethylenediaminetetraacetic acid (EDTA) and Fe 2+ to improve methane yield and process stability in anaerobic digestion of kitchen waste. Their results suggested that EDTA-Fe 2+ could stimulate enzymatic activity by improving Fe bioavailability.…”

Enhancing biogas production from palm oil mill effluent through the synergistic application of surfactants and iron supplements

“…In addition, focus has been placed on the addition of trace elements (i.e., Fe, Co, Ni, and Mo) as supplements to maintain the stability of the AD process and to accelerate the activity of microbial enzymes, augmenting biogas production. In this case, Fe is an essential trace element that must be utilized by methanogenic bacteria for the conversion of CO 2 to CH 4 ; Fe acts as an electron acceptor and donor and controls hydrogen sulfide in biogas [ 12 , 13 ]. Many studies have revealed that AD systems can easily become Fe deficient since Fe is a binding component involved in sulfide (S 2− ), carbonate (CO 3 2− ), and phosphate (PO 4 3− ) precipitation and the formation of inorganic and organic complexes.…”

“…Many studies have revealed that AD systems can easily become Fe deficient since Fe is a binding component involved in sulfide (S 2− ), carbonate (CO 3 2− ), and phosphate (PO 4 3− ) precipitation and the formation of inorganic and organic complexes. This binding process limits the bioavailability of Fe for microbial uptake, making the available Fe content lower than that of other trace elements and increasing the amount of Fe supplements that must be added to the system [ 12 , 14 , 15 ]. Consequently, to increase the performance of AD systems, traditional chelating agents, e.g., ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), have been applied to increase the soluble trace metal fraction by forming dissolved complexes, which are available for adsorption by anaerobic microorganisms [ 16 ].…”