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Anaerobic digestion of brewing “waste”. PowerPoint Presentation
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Anaerobic digestion of brewing “waste”.

Anaerobic digestion of brewing “waste”.

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Anaerobic digestion of brewing “waste”.

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  1. Anaerobic digestion of brewing “waste”. L.S. Nkadimeng, S.T.L. Harrison Energy Postgraduate Conference 2013

  2. < EPC 2013 > • Effluents • Beer • Spent grain • Spent yeast • Wastewater Background AD (wastewater treatment) Picture from : http://www.sabmiller.in/know-beer_brewing.html Is it viable to use spent grain and/or spent yeast as AD feed in order to intensify the energy output of the WTP?

  3. Anaerobic digestion (AD) Steam to brewery CO2 Boiler Water Carbohydrates sugars Organic acids, alcohols Acetate, H2, CO2 Biogas (CH4, CO2) Proteins Amino acids H2, CO2, NH4 Lipids Fatty acids Hydrolysis Acidogenesis Acetogenesis Methanogenesis td : 30 minutes 1,4 to 5 days 2 to 3 days (Mosey 1983; Lawrence & McCarty 1989; Gerber & Span 2008) < EPC 2013 > - 3 - University of Cape Town >> 12 October 2014 >>

  4. (Aliyu & Bala, 2011, Mussatto & Teixeira, 2010) Spent grain • Mechanical pre-treatment to promote hydrolysis: grinding Digestibility: Only 15% reduction in COD over 19 days of digestion < EPC 2013 > - 4 - University of Cape Town >> 12 October 2014 >>

  5. Spent yeast: Effect of non-acclimated system on pH < EPC 2013 > - 5 - University of Cape Town >> 12 October 2014 >>

  6. Spent yeast: Slow incremental feeding • Highest removal rate: 962 mg-COD/L.day • Removal efficiency: • 69% in 1 day • 97% in 3 days • 99% in 9 days < EPC 2013 > - 6 - University of Cape Town >> 12 October 2014 >>

  7. 25 day HRT, SCOD/TCOD of feed ~ 60% Spent yeast: Continuous feed and draw < EPC 2013 > - 7 - University of Cape Town >> 12 October 2014 >>

  8. Spent yeast: Comparisons to SAB reactor • Aim to reduce the HRT on lab reactors. • Suggested strategies: recycling and continuous flow. < EPC 2013 > - 8 - University of Cape Town >> 12 October 2014 >>

  9. Conclusions • Degradation efficiency on spent grain was poor and not enhanced by mechanical pre-treatment. Spent grain is not viable as substrate in in the WTP. • Acclimation of the system to yeast feed is important for auto-regulation of pH. • Yeast is promising as substrate in the WTP. Future work • Optimisation of yeast digestion on lab reactors. • Anaerobic digestion experiment to mimic large scale digester (including biogas production measurements) • Possibly, implementation of results on the WTP. < EPC 2013 > - 9 - University of Cape Town >> 12 October 2014 >>

  10. Acknowledgements Prof. S T L Harrison < EPC 2013 > - 10 - University of Cape Town >> 12 October 2014 >>