anaerobic digestion of brewing “waste”. l.s. nkadimeng, s.t.l. harrison energy postgraduate...
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Anaerobic digestion of brewing “waste”.
L.S. Nkadimeng, S.T.L. Harrison
Energy Postgraduate Conference 2013
Background
Picture from : http://www.sabmiller.in/know-beer_brewing.html
Effluents• Beer• Spent grain• Spent yeast• Wastewater
University of Cape Town >> 21 April 2023 >> - 2 -< EPC 2013 >
AD(wastewater treatment)
Anaerobic digestion (AD)
Proteins
Carbohydrates
Lipids
sugars
Amino acids
Fatty acids
Organic acids,
alcohols
H2, CO2, NH4
Acetate,H2, CO2
Biogas (CH4, CO2)
Hydrolysis Acidogenesis Acetogenesis Methanogenesis td : 30 minutes 1,4 to 5 days 2 to 3 days
Water
Steam to brewery CO2
University of Cape Town >> 21 April 2023 >> < EPC 2013 > - 3 -
(Mosey 1983; Lawrence & McCarty 1989; Gerber & Span 2008)
Spent grain
• Mechanical pre-treatment to promote hydrolysis: grinding
Only 15% reduction in COD over 19 days of digestion
Digestibility:(Aliyu & Bala, 2011, Mussatto & Teixeira, 2010)
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Spent yeast: Effect of non-acclimated system on pH
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Spent yeast: Slow incremental feeding
< EPC 2013 >University of Cape Town >> 21 April 2023 >> - 6 -
Highest removal rate: 962 mg-COD/L.day
Removal efficiency: 69% in 1 day
97% in 3 days99% in 9 days
•
Spent yeast: Continuous feed and draw
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• 25 day HRT, SCOD/TCOD of feed ~ 60%
Spent yeast: Comparisons to SAB reactor
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HRT Average COD reduction rate
COD reduction efficiency
Substrate
days mg-COD/L.day
Lab reactors 25 3390 91% Spent yeast
WTP at current op.
1.8 1260 73 - 91% Wastewater
WTP design spec. 1(min)
4500(max)
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• Aim to reduce the HRT on lab reactors.
• Suggested strategies: recycling and continuous flow.
• 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.
Conclusions
University of Cape Town >> 21 April 2023 >> < EPC 2013 > - 9 -
Acknowledgements
Prof. S T L Harrison
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