Biogas potential of spent, coffee husk and pulp

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

BioInnovate Project 04/2010

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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


BioInnovate Project 04/2010 8

◦ 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


11BioInnovate Project 04/2010

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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


Technology

Biogas potential of spent, coffee husk and pulp