1 / 24

Enhancing Methane Production from Yard Waste with Food Waste Supplementation

Investigating the enhancement of methane production during anaerobic digestion of yard waste using biological pretreatment and food waste supplementation. Addressing low conversion rates and exploring a novel approach with discarded sludge pretreatment and small amounts of food waste. Research includes material and methods, results, and discussions on pH effects and optimal pretreatment periods.

mjared
Download Presentation

Enhancing Methane Production from Yard Waste with Food Waste Supplementation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Enhancing methane production during anaerobic digestion of biological pretreated yard waste through food waste supplementation Zhang Le (Ph.D. Candidate) Supervisor: A/Prof. Loh Kai-Chee Mentor: Dr. Zhang Jingxin Department of Chemical & Biomolecular Engineering National University of Singapore September, 2017

  2. Outline 1. Introduction 2. Research problems & analysis 3. Research route 4. Material and methods 5. Results and discussion 6. Conclusion

  3. 1. Introduction Yard waste issue • Source:National Environment Agency (NEA) in Singapore • Ratio of green space in Singapore: 50% • Food waste and Yard waste – Biomass resources ! • Recycling rate is very low • Potential environmental pollution Strategy: Anaerobic digestion technology, waste to energy Tree trimmings Grass Leaves

  4. 2. Research problems & analysis Anaerobic digestion (AD) technology Organic matters Methanogenesis (3) Acetogenesis (2) Yard waste • Main problems: • Low conversion rate due to degradation-resistant lignocellulosic components [1-3] Hydrolysis and Acidogenesis (1) + Inoculum Fast Volatile fatty acids Acetate and Hydrogen Slow [1] He L, et al. Current Organic Chemistry, 2015, 19(5): 437-446. [2] Kim M, et al. Water Research, 2002, 36(17): 4369-4385. [3] Yen H W, et al. Bioresource technology, 2007, 98(1): 130-134. Biogas (Methane)

  5. 2. Research problems & analysis Cellulose Main problem: 1. Low conversion rate due to degradation-resistant cellulose, hemicellulose, and lignin [1] Biogas yield with low efficiency ? Hemicellulose Lignin [1] A. Cesaro and V. Belgiorno, Chemical Engineering Journal, vol. 240, pp. 24-37, 2014.

  6. 2. Research problems & analysis Literature review: Paper numbers of common pretreatments for enhancing biogas production during 2006-2010 and 2011-2015 • Frequently used, still have limitations • Physical pretreatments: require many extra energy input • Chemical pretreatments: need high cost for chemical reagents • Biological pretreatment: long pretreatment period and high cost for bacterial strain or bio-enzymes • Proposed approach: discarded sludge pretreatment (DSP) coupled with small amount of food waste addition

  7. 2. Research problems & analysis Hypothesis: Previous literature used acids to pretreat yard waste for acid hydrolysis, and to break down the yard waste into easily digestion smaller pieces. But the problem is, adding acid will cause the pH become too low. So I want to replace acid with FW. The acidic FW sludge is less acidic than acid. That is why I propose using small amount of FW coupled with DSP to pretreat yard waste. Better!? DSP DSP Acid Coupled with small amount of food waste addition Previous study Current study

  8. 3. Research route A0 Batch fermentation No DSP Monitor: Biogas production; Methane concentration A10 B0 Monitor: pH value; Cellulose, hemicellulose B10 Batch fermentation B20 DSP Monitor: Biogas production; Methane concentration B50 Note: AX, BX: A: without DSP; B: with DSP; X: weight percentage of FW based on mixture of YW and FW B100

  9. 4. Material and methods • DSP process: • TS (FW)= 32.7 wt.% • TS (YW)= 87.0 wt.% • Inoculum: TS= 1.6 wt.% (negligible) • Inoculum volume: 400 ml • Constant TS of feedstock mixture: 64g • Mass weight  TS of FW + Mass weight  TS of YW • AD process: • Finishing DSP, • Adding another 400 ml sludge • Adding DI-water till 800 ml • Batch fermentation

  10. 4. Material and methods

  11. 4. Material and methods • Yard waste: mainly tree leaves and twigs Treatment: drying, shredded into particles (20-mesh) • Food waste: mainly includes rice, vegetables, meat, and noodles. Treatment: smashed by a FW disposer • Inoculum: TS: 1.6±0.1 wt.% • pH: pH analyzer (Agilent 3200M, USA) • Chemical oxygen demand (COD): HACH color meter (DR900, USA) • C, H, N, S: elemental analyzer (Vario MICRO cube, Hanau, Germany) • Cellulose, hemicellulose, and lignin contents: Van Soest method • Daily biogas volume: 500 ml syringe (SGE Analytical Science, Australia) • Concentration of CH4 and CO2 in biogas: GC (Clarus 580 Arnel, PerkinElmer, USA) • Microbiological analysis: real-time PCR and high throughput 16S rDNA gene pyrosequencing technology • Statistical analysis: SAS software (SAS Institute Inc., Cary, NC, USA), specified threshold p-value of 0.01

  12. 5. Results and discussion 5.1. Detailed characteristics of two substrates and inoculum

  13. 5. Results and discussion 5.2. Effect of FW addition on pH • Significance analysis • Significant difference (p= 0.0017 < 0.01) between B0 and B10 group • No significant difference (p=0.0230-0.0509 > 0.01) among B10, B20, B50, and B100 groups • Initial pH 6.8-7.0, after 1 day for hydrolysis, dramatically decreased to 4.3-4.9 • Summary: (1) 10 wt.% FW addition could significantly decrease pH value of hydrolysis mixture, and higher amount of FW addition could not significantly decrease pH; (2) 3-4 days was an optimal pretreatment period

  14. 5. Results and discussion 5.3. Effect of FW addition on cellulose content • Significance analysis indicated that there was significant difference (p= ~0.001 < 0.01) between B0 and B10 group while there was no significant difference (p=0.060 > 0.01) among B10 and B20 groups • Summary: (1) 10 wt.% FW addition could significantly decrease cellulose content of hydrolysis mixture, and higher amount of FW addition could not significantly decrease cellulose content

  15. 5. Results and discussion 5.4. Effect of FW addition on hemicellulose content • Significance analysis indicated that there was significant difference (p= 0.003 < 0.01) between B0 and B10 group while there was no significant difference (p=0.021 > 0.01) among B10 and B20 groups • Summary: (1) 10 wt.% FW addition could significantly decrease hemicellulose content of hydrolysis mixture, and higher amount of FW addition could not significantly decrease hemicellulose content

  16. 5. Results and discussion 5.5. Effect of 10 wt.% FW addition on methane production • The highest daily methane yield attributed to B10 • 10 wt.% FW addition shortened AD period Daily methane production of DSP and untreated YW with FW addition

  17. 5. Results and discussion 5.6. Effect of 10 wt.% FW addition on methane production 10000 8500 • Comparative literature: Bioresource Technology 175 (2015) 167–173 Cumulative methane production of DSP and untreated YW with FW addition • Cumulative methane yield is comparable to literature. • Deviation probably derived from different feedstock

  18. 5. Results and discussion 5.6. Effect of 10 wt.% FW addition on methane production Cumulative methane production of DSP and untreated YW with FW addition • Compared with A0, B10 enhanced total methane production by 124%. • Cumulative methane yield increased from 71 ml/g VS to 158 ml/g VS. (2.2 fold)

  19. 5. Results and discussion 5.7. Effect of FW addition on microbial community structures • Operation for about 50 days • Real-time PCR for quantification of total bacteria and archaea • Copy numbers of 16S rRNA gene for total bacteria in B10 significantly higher • Number of archaea 16S rRNA gene in B10 significantly higher • 10 wt.% FW addition enhanced bacteria number significantly

  20. 5. Results and discussion 5.7. Effect of FW addition on microbial community structures Hierarchical cluster analysis of bacteria community structure among B0, B10 and seed sludge at genus level • Bacteria community structure was dramatically changed due to addition of 10 wt.% FW

  21. 5. Results and discussion 5.7. Effect of FW addition on microbial community structures Taxonomic classification of bacteria from B0, B10 and seed sludge at genus level. Dominated bacteria genus: No. 1: Sphaerochaeta (12%); No. 2: Bacteroides (8%); No. 3: Proteiniphilum (7%); No. 4: Clostridium XIVa (6%); No. 5: Cellulosibacter (6%); No. 6: Treponema (4%) 43%

  22. 5. Results and discussion No. 1: Sphaerochaeta “Growth was strictly fermentative and anaerobic; Hexose and pentose fermentation yielded ethanol, acetate and formate as major end products” (Int J Syst Evol Microbiol. 2012 Jan;62(Pt 1):210-6) No. 5: Cellulosibacter Sphaerochaeta Cellulosibacter 10 wt.% FW Hemicellulose, cellulose fermentation Biogas or methane productivity

  23. 6. Conclusion • A coupled pretreatment method by using discarded sludge pretreatment (DSP) coupled with 10 wt.% FW addition was proposed, which was verified to be significantly more efficient than single DSP method in improving methane production in AD process of YW. • A suitable period for pretreatment was 3-4 days. • With addition of 10 wt.% FW, we found that, (1) pH, cellulose, and hemicellulose content were significantly reduced. (2) total methane production enhanced by 124% (3) greatly enhanced beneficial bacteria genus in microbial community

  24. Acknowledgements • Supervisor: A/Prof. Loh Kai-Chee • Mentor: Dr. Zhang Jingxin • PI of E2S2-CSA, A/Prof. Tong Yen Wah • Office & Lab mates • Parents & Friends • CREATE-CSC

More Related