Biochar enhanced thermophilic anaerobic digestion of food waste: Focusing on biochar particle size, microbial community analysis and pilot-scale application. (1st April 2020)

• Record Type: Journal Article
• Authors: Zhang, Le; Lim, Ee Yang; Loh, Kai-Chee; Ok, Yong Sik; Lee, Jonathan T.E.; Shen, Ye; Wang, Chi-Hwa; Dai, Yanjun; Tong, Yen Wah
• Is Part Of: Energy conversion and management. Volume 209(2020)
• Publication Date: 2020-04-01
• Subjects: AD anaerobic digestion -- FW food waste -- OLRs organic loading rates -- DIET direct interspecies electron transfer -- VFAs volatile fatty acids -- SEM scanning electron microscope -- TS total solids -- VS volatile solids -- SCOD soluble chemical oxygen demand -- PCR polymerase chain reaction -- CMYs cumulative methane yields -- RMSE root mean square error -- OTUs operational taxonomic units -- PCA principal components analysis -- CCA canonical correspondence analysis; Thermophilic anaerobic digestion -- Bioenergy conversion -- Food waste minimization -- Biochar amendment -- Methanogenic pathways -- Pilot-scale application; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2020.112654
• Languages: English
• ISSNs: 0196-8904

Abstract

Graphical abstract: Highlights: Thermophilic food waste digestion with varied particle size of biochar was examined. All examined biochars (<50 μm to 3 cm) significantly improved methane production. Bacteria Thermotogae and methanogens Methanothermobacter & Methanosarcina enriched. The synergy of hydrogenotrophic and acetoclastic methanogenic pathways was achieved. Both technical and economic feasibility of adding biochar strategy were validated. Abstract: Effectiveness of biochar addition to enhance thermophilic semi-continuous anaerobic digestion (AD) of food waste for methane production was investigated with a focus on dosage and particle size of biochar, pilot-scale application and elucidation of methanogenic pathways. Optimal dosage range of biochar was determined as 7.5 to 15 g per L working volume based on lab-scale batch AD. Effects of biochar with different particle sizes at a model dosage of 15 g/L were evaluated in a semi-continuous AD experiment, results of which showed that all the examined biochars with different particle sizes (<50 μm to 3 cm) substantially enhanced the average methane yields (0.465–0.543 L/gVS) compared to control digesters which failed due to overloading (≥3.04 gVS/L/d). No significant difference in methane yields, however, was observed among digesters with different particle sizes of biochars, except for 1–3 cm. The core reason for this phenomenon was that the biochars with different particle sizes had similar properties (e.g. density, surface area and pore size) and that the floating of large particle size (1–3 cm) of biochar with a density of 847 kg/m 3 was not conducive to microbial growth. Metagenomic analysis was performed to determine the predominant microbial species and to explain the main methanogenic pathways in biochar-amended digesters using 16S rRNA sequencing. In the biochar-amended digester, bacterial phylum Thermotogae containing a major genus of Defluviitoga was selectively enriched with gradual increase of organic loadings, while simultaneously enriched methanogen genera Methanothermobacter and Methanosarcina, which showed a synergy of hydrogenotrophic and acetoclastic methanogenic pathways, jointly enhanced the methane productivity. Both technical feasibility and economic feasibility of adding biochar with simple pretreatment (e.g. smash) were validated in the pilot-scale thermophilic semi-continuous AD operations.