Date Published: June 1, 2018
Publisher: Springer Berlin Heidelberg
Author(s): Jing He, Xing Wang, Xiao-bo Yin, Qiang Li, Xia Li, Yun-fei Zhang, Yu Deng.
High content of lipids in food waste could restrict digestion rate and give rise to the accumulation of long chain fatty acids in anaerobic digester. In the present study, using waste cooking oil skimmed from food waste as the sole carbon source, the effect of organic loading rate (OLR) on the methane production and microbial community dynamics were well investigated. Results showed that stable biomethane production was obtained at an organic loading rate of 0.5–1.5 g VS L−1 days−1. The specific biogas/methane yield values at OLR of 1.0 were 1.44 ± 0.15 and 0.98 ± 0.11 L g VS−1, respectively. The amplicon pyrosequencing revealed the distinct microbial succession in waste cooking oil AD reactors. Acetoclastic methanogens belonging to the genus Methanosaeta were the most dominant archaea, while the genera Syntrophomona, Anaerovibrio and Synergistaceae were the most common bacteria during AD process. Furthermore, redundancy analysis indicated that OLR showed more significant effect on the bacterial communities than that of archaeal communities. Additionally, whether the OLR of lipids increased had slight influence on the acetate fermentation pathway.
It was estimated that annual amount of food waste (FW) come up to 36.4 and 89 million tons in USA and E.U., respectively (Agency et al. 2012; Lin et al. 2013). Approximate 60 million tons annually in China (Meng et al. 2014), including 6 million tons of waste cooking oil. Among the various proposed methods to alleviate these problems, anaerobic digestion (AD) has been considered as the waste-to-energy technology and has been performed well for treating food waste and waste cooking oil (Dasgupta and Mondal 2012; Kim et al. 2008).
FOG is neither easily treated by conventional method, nor decomposed biologically (Stoll and Gupta 1997). FOG co-digestion with other waste materials was a feasible way to alleviate LCFA suppresses, but loading threshold values still was a barrier during FOG AD. FOG, as an AD material, is widely used for co-digestion with various other organic wastes (such as sludge and livestock manure). It has earlier been observed that high FOG loading rates cause technical discrepancies in the process of fermentation and even delay process recovery, especially due to the inhibitory effect of LCFAs. Hence, previous studies about the functional role and dynamics of the various microbial species that are involved in the LCFA β-oxidation in anaerobic reactors have been done (Table 3).Table 3Characterization of microbial community of AD with LCFA or FOGReferencesSubstrateAD patternMethodMethanogenic archaea communityBacterial communityShigematsu et al. (2006)Oleic and palmitic acidsSemi-continuous, CSTR, 37 °CDGGEDominant genera Methanosaeta Methanosarcina MethanospirillumDominant phyla Bacteroidetes Spirochaetes syntrophomonadaceaeSousa et al. (2007b)MixLCFA, Palmitate 32–48%; Myristate 11–15%; oleate 23–26%Batch, 35 °CDGGEDominant genera Methanosaeta MethanosarcinaDominant phyla(80%) ClostridiaceaeBaserba et al. (2012)OleateSemi-continuous, CSTR, 55 °CDGGEDominant genera Methanosarcina MethanococcusDominant phyla Firmicutes Bacteroidetes Proteobacteria ThermotogaeYang et al. (2016)FOG and sewage sludgeSemi-continuous, CSTR, 35 °CHigh-throughput pyrosequencingDominant genera Methanosarcinales (11.7%) Methanosaeta (13.2%)Dominant phyla: Actinobacteria (28.4%) Firmicutes (22.9%) Bacteroidetes (12.5%)Ziels et al. (2016)FOG and municipal sludgeSemi-continuous, CSTR, 35 °CHigh-throughput pyrosequencing +qPCRDominant genera Methanosaeta (23 → 45%) Methanospirillum (1.3 → 34%) Methanosphaera (0 → 7%)Dominant genera Syntrophomonas (1.2 → 9.0%) GelriaPresent studyFOG solelySemi-continuous, CSTR, 35 °CHigh-throughput pyrosequencingDominant genera Methanosaeta (82 → 45 → 82%) Methanoculleus (4 → 25 → 2%) Methanospirillum (7 → 18 → 8%) Methanosarcina (4 → 40%)Dominant genera Syntrophomonas (12 → 35%) Anaerovibrio (10 → 40 → 20%)