Hema Rughoonundun Research Week 2008

Outline of Presentation The MixAlco Process Introduction Sludge Materials and Methods Results Fermentation of sludge Energy Potential of sludge Conclusion

Thermochemical Common Energy Routes

Sugar

Less Common Energy Routes Carboxylate

The MixAlco Process The MixAlco process has been developed by Dr M Holtzapple and his team from the Department of Chemical Engineering, Texas A&M University. The process is a patented technology that converts any biodegradable material (e.g, sorted municipal solid waste, sewage sludge, industrial biosludge, manure, agricultural residues, energy crops into a mixed alcohol fuels containing predominantly 2- propanol, but also higher alcohols up to 7-tridecanol (Holtzapple et al., 1999).

1991 Laboratory Investigation 1998 Pilot Scale (200lb/day) 2007 Demonstra tion Plant (5 ton/day) 2009 Demonstration Plant (100 ton/day) Stages of Development

Process Hydrogenate PretreatFermentDewater Thermal Conversion Lime Kiln Lime Carboxylate Salts Calcium Carbonate Mixed Ketones Hydrogen Mixed Alcohol Fuels Biomass MixAlco … the Process

1 1 Complex organic matter Carbohydrates, proteins, fats Complex organic matter Carbohydrates, proteins, fats Soluble organic molecules Sugars, amino acids, fatty acids Soluble organic molecules Sugars, amino acids, fatty acids Methane, CH4 Carbon dioxide, CO2 Methane, CH4 Carbon dioxide, CO Volatile fatty acids Acetic acid Hydrogen, H 2 Carbon dioxide, CO 2 Hydrogen, H 2 Carbon dioxide, CO 2 Hydrolysis Acidogenesis Acetogenesis Methanogenesis Fermentation

What is Mixed Alcohols Composition of the Mixed alcohols

1. Acetic acid, unlike ethanol, is biologically produced from simple sugars without the production of carbon dioxide: C 6 H 12 O 6 → 2 CH 3 CH 2 OH + 2 CO 2 (Biological production of ethanol) C 6 H 12 O 6 → 3 CH 3 COOH (Biological production of acetic acid) Hence, on a Mass basis, the yield is higher for acetic acid compared to ethanol fermentation. Advantages of the MixAlco Process

2. C 6 H 12 O 6 2C 2 H 5 OH + CO2 G = kcal/mol glucose ethanol C 6 H 12 O 6 3 C 2 H 3 OOH G = kcal/mol glucose acetic acid The actual stoichiometry is more complex C 6 H 12 O 6 6 acetate + 2 propionate + butyrate + 5CO 2 + (67 mol%) (22 mol%) (11mol%)3 CH 4 + 6H 2 O Advantages of the MixAlco Process

Substrates Lignocellulosic Municipal solid waste Any biodegradable material!! Advantages of the MixAlco Process

Does not require sterile condition Does not require expensive enzymes Good Energy Yield Energy (MJ/L) Gasoline34.9 Mixed Alcohols29 Ethanol23.4 Advantages of the MixAlco Process

Methodology I. Substrates Mixed Sludge Physical Properties% Moisture97.92 ± 0.02 Volatile Solids64.62 ± Ash35.38 ± Fermentation of Sludge using MixAlco Process

Mixed Sludge Elements % Glucose5.267 Xylose4.180 Mannose4.214 Total Nitrogen4.405 Total Phosphorous1.298 Total Potassium0.221 Fermentation of Sludge using MixAlco Process

II. Apparatus Centrifuge bottle bioreactor (Ross, 1998) Fermentors in Roller Apparatus Fermentation of Sludge using MixAlco Process

III. Conditions of Experiments Solids concentration of 50 g/L Marine Innoculum (12.5%) Temperature 550C Gas vented and sample of liquid taken every 2 days pH adjusted using ammonium bicarbonate Iodoform used as inhibitor used (0.8µL every 2 days) Fermentation of Sludge using MixAlco Process

Parameters analysed pH Volume of gas Gas Composition Nitrogen, Methane and Carbon dioxide Apparatus: Gas Chromatograph (Agilent 6890 series, Agilent Technologies, Palo Alto, California) equipped with a thermal conductivity detector (TCD) Fermentation of Sludge using MixAlco Process

Parameters analysed Total Carboxylic Acids Apparatus: Agilent 6890 gas chromatograph (Agilent Technologies, Palo Alto, California) equipped with a flame ionization detector (FID) and a 7683 series injector. Fermentation of Sludge using MixAlco Process

Results

Yield Parameters Parameter Value Average Acid Concentration (g/L) Yield (g total acids produced/g VS fed) 0.34 Conversion (g VS digested/ g VS fed) 0.43 Total Acids Selectivity (g total acids produced/g VS digested) 0.79 Total Acid Productivity (total acids produced/ total liquid volume. Time) 0.34 Results

Significance of results for Mauritius Sludge production by 2015 = 122,260 tonnes/ year Dry sludge (25 % solids)= 30,565 tonnes/year Assuming Volatile solids % = 65% Expected yield of Acids= 0.34 g Acids/g VS fed Energy Value of Mixed Acids = 29MJ/L Conclusion

Total carboxylic acids production = 6755 tonnes/year Potential in terms of 1. Energy = 192, 424 GJ 2. Tonne of Oil equivalent= 4596 toe 3. Money (at 82 USD per barrel)= Rs 80.4 million 4. Gasoline (60% Efficiency) = 4053 tonnes Conclusion

Thank you