Post on 03-Jun-2015
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BioInnovate Project 04/2010 1
Biogas potential of spent, coffee husk and pulp
B. Assefa, D. Abate, B. Leta
First Bio-Innovate Regional Scientific Conference, Addis Ababa, Ethiopia, 25-27 February 2013
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Coffee is the world's second most valuable commodity after petroleum
Ethiopia ◦ Contributes about 3 % for global coffee market.◦ Produces about 380,000 tons ◦ About 16% coffee bean is produced by wet
process while 84 % by dry process.
Background
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The dry processing generates ◦the solid waste (coffee husk)◦piled up in field causing serious
environmental problem
The wet processing generates ◦The wastewater released untreated◦Solid waste with high moisture content
(pulp and mucilage) ◦Dispose in the water and field
Rational
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Estimated annual generation of solid wastes ◦Husk 430,920 tons/year;◦Pulp 72,960 tons/year
It is huge resources;
Continued . . .
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Characteristics of coffee husk
No Parameters Mean1 Moisture content (%) 9.63
2 Bulk Density (mg/cm3) 0.743 Volatile matter (%) 82.7
4 Fixed matter (%) 7.65
5 Ash (%) 7.656 Total Carbon (%) 53.67
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Characteristics of the Pulp
Parameters Mean
TS, % 70.13 VS/TS, % 93.0
Moisture Content, % 29.87 Fixed Solid, % 6.99
Total Carbon (%) 50.18
pH 6.8
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The waste has high organic content It can be a good feed stock for biogas
production Concern
◦ The biomass might be cellulosic materials◦ the rate of biodegradability may be low◦ Tannin, caffeine and phenols could poison
anaerobic bacteria
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◦ Decomposing the biomass using (oyster) mushroom would improve biodegradility
◦ Reduce the poisoning effect of TCP chemicals using the use of biomass for mushroom
Hypotheses
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Determination of biogas potential of coffee husk, coffee husk spent after mushroom production and pulp
Comparison of the results against the hypothesis
Experiential design Objective
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The inoculums ◦ brought from an active, food leftover based
biogas plant found in the same institution;◦ Amount of inoculums: 800 ml (volume);
Substrates: ◦ Coffee pulp, coffee husk, and spent coffee husk. ◦ The pulp are kept in a deep freezer (less than -
120C)◦ The spent is brought from a mushroom cultivation
experiment (after three cycle of harvest)
Materials and Methods
Materials
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Composition of substrate added into the flasks
Substrates TS (%) VS (%)
Husk 87.5 80.8
Spent 27.8 89.8
Pulp 12.1 79.9
Inoculums 2.3 63.3
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◦ Erlenmeyer Flask◦ Tubes◦ Water bath (Thermostat)◦ Gas bags◦ Shredder ◦ Muffle furnace◦ Drying oven
— Gas analyzer — Syringe— Balance— pH meter— Stop cock
Apparatus
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◦The samples are added in 1:2 ratio VS of substrate to inoculum in order maintain constant food to micro-organism ratio
◦the experiments were run at 37oC◦The temperature is maintained by thermostat
◦The pH is measured initially and at the end of the experimentation
◦Gas is collected regularly by gas bag
Methods
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Mass of substrate◦ Precision balance is used
Gas volume◦ the volume of the gas was measured using
syringe of known volume, 50ml and100 ml. Temperature
◦ the temperature of the room is measured regularly when the gas volume is measured using (thermometer)thermocouple
Measurement
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Experimental Set up
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Results and
Discussion
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Items
Biogas yield [l/g VS]
Methane gas [l/g VS]
[%]Pulp 0.863 0.081 0.460 56 Husk 0.486 0.071 0.266 58 Spent 0.188 0.068 0.090 49
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Pulp gave output as of comparable to ◦Organic wastes from food industry : 0.4-0.8 m3 biogas/kgVS (Gunaseela, 1997)
◦Fruit and vegetables solid waste and wastewater 0.2-0.4 m3 CH4/kgVS
Husk gave output as of comparable to ◦ Crops (straw, beet collars) 0.35-0.4 m3biogas/kgVS◦ Rice straw 0.2 m3 CH4/kgVS (Dinuccio et al., 2009)
◦ Barley straw 0.2 m3 CH4/kgVS (Dinuccio et al., 2009)
Result and discussion
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Spent substrate gave the lowest output ◦It is lower estimated potential all
biomass◦It seems that the mushroom taken up
significant easily digestible stuff
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◦Coffee waste can be as a good feed for biogas production
◦Coffee husk much higher gas potential than spent coffee husk The use of coffee husk for mushroom
production did not improve gas production and its rate
◦The pulp collected from wet processing gives much higher gas production coffee husk
◦Spent coffee husk has still significant gas potential
Conclusion
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Thank for your attention
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