Methane production of rare earth element‐rich Dicranopteris dichotoma and effects of La(III) on anaerobic digestion performance of lignocellulose

Abstract

BACKGROUND Phytoremediation by hyperaccumulators (such as Dicranopteris dichotoma) is widely used for the remediation of rare earth tailings in China. Accordingly, a large amount of rare earth‐rich plant residues is produced. Anaerobic digestion could convert biomass into energy. In this study, the anaerobic digestion performance of D. dichotoma, which is rich in rare earth elements (REEs), was investigated. Cellulose, xylan, and glucose served as the model substrates to explore the effects of La(III) on hydrolysis and methane production using batch anaerobic digestion. RESULTS The results indicated that the La(III) concentration of 500 mg/L inhibited methane production from cellulose with the reduciton of 20%. Inversely, no significant difference was found in the cumulative methane yield from glucose with different La(III) concentrations. The microbial community results showed that the lack of cellulose hydrolyzing bacteria, such as Clostridium III and Clostridium XlVa, may be the main reason for the inhibition of methane production. Furthermore, the methane yield of REE‐rich D. dichotoma was 181.5 ± 14.6 mL/g VS and the La(III) concentration of luquid digestate was only 2.20 mg/L. CONCLUSION The inhibition of La(III) on anaerobic digestion of lignocellulose was mainly in the hydrolysis process of cellulose, while the inhibition of xylan hydrolysis was relatively weak, and it had no significant effect on methanogenesis process of glucose. La(III) showed a small effect on the methane production of REE‐rich D. dichotoma due to a small amount of release into the liquid digestate. Anaerobic digestion may be a feasible way for treating lignocellulose plants contaminated with rare‐earth minerals. © 2022 Society of Chemical Industry (SCI).

Effect of Biochar in Modulating Anaerobic Digestion Performance and Microbial Structure Community of Different Inoculum Sources

“…In particular, the relative abundances of Clostridium_III and unclassified_Ruminococcaceae were 21.19% and 10.33% in SMI, respectively, and were richer than those in CPI. Clostridium_III, a cellulose hydrolytic acidification bacterium with butyric acid as its metabolite [46], was more prevalent in unacclimated digesters; however, its relative abundance remained below 5% in most acclimated digesters [47]. Meanwhile, Ruminococcaceae can hydrolyze polysaccharides via different mechanisms, such as producing cellulolytic enzymes, short-chain fatty acids, VFAs, and fermenting hexoses and pentoses [48].…”