Optimization of food-waste based biogas digester by a ... Projects... · SAHYADRI COLLEGE OF ENGINEERING & MANAGEMENT, SAHYADRI CAMPUS, ADYAR , MANGALURU, INDIA Department of Civil

SAHYADRI COLLEGE OF ENGINEERING & MANAGEMENT, SAHYADRI CAMPUS, ADYAR , MANGALURU, INDIA

Department of Civil Engineering

Optimization of food-waste based biogas

digester by a three staged digester

STUDENTS: Mr. Charanraj C Shetty, Mr. Adithya Shetty A, Mr.

Gagan S D, Mr. Vipin P P.

GUIDES: Mr. Prasanna Kumar. C, Mrs. Geetha S D

A KSCST sanctioned project

Student Project Programme- 40S_BE_2083


Introduction

A biogas plant is an anaerobic digester that produces biogas from

animal, food waste or plant waste.

Biogas can provide a clean, renewable energy from organic waste

materials.

Food waste is the best feedstock for Biogas Production.

It is 20 times more efficient than conventional methods.

Constant stirring increases the rate of Production.

pH plays an important role in production of Biogas.

A three staged digester helps in complete digestion of food waste

meanwhile it provides stirring effect to the slurry.

The biogas production varies with type of feedstock.


Objectives achieved by project-

To study the production of biogas with normal digester and a three

staged digester and hence obtain optimization on using three stage

digester.

To optimize the production of biogas using higher temperature with heat

exchanger.

To regulate the pH of slurry in the digester and thus promoting bacterial

activity.

To study the production of biogas on various feedstock by using a simple

prototype reactor.

To analyse the Gas Composition using Gas Chromatography


• ARTI – appropriate rural technology of India, Pune (2003) , Dr. Anand Karve has developed a

compact biogas plant which uses waste food rather than any cow dung as feedstock, to supply biogas

for cooking. The conventional biogas systems, using cattle dung, sewerage, etc. use about 20 times

more cowdung (40 kg) to get same amount of methane. Just 2 kg of such feedstock produces about

500 g of methane, and the reaction is completed with 24 hours.

• Wilson, T., Potts, L., and Stallings, R. 2005 -For most wastewater solids and for all loading rates,

multi-stage anaerobic digestion has the advantage of achieving superior performance compared with

single-stage conventional digestion. The performance increase is achieved even with smaller digester

volumes because of the higher loading rates that can be achieved with multi-stage digesters. The

multi-stage process is capable of a higher volatile solids (VS) reduction with shorter residence times,

production of biogas of higher quality, and elimination of foaming.

• Andreas Lemmer *, Hans-Joachim Naegele and Jana Sondermann-In most cases, continuous stirred

tank reactors (CSTR) are used for producing biogas from energy crops or organic residues [1]. When

using this type of biogas digester, the stirring of the substrate in the digesters is vital for the biogas

formation process. The purpose of stirring is to distribute the nutrients in the biogas digester uniformly,

to form a suspension of liquid and solid parts, to avoid sedimentation of particles, to ensure uniform

heat distribution, to prevent foam formation and to enable gas lift from the fermentation substrate at high dry matter (DM) contents.

Literature review


Methodology followed

A normal biogas digester was designed and it was fed with constant

feedstock of 0.2% the size of the digester.

A new technique three-staged digester was designed and even that

was fed constantly with 0.2% the size of the digester.

The gas produced was quantified daily and the conditions like pH

and temperature were regulated.

The yield per 100L size of the digester was calculated.

From the results the optimization by using the three staged digester

were studied.

A prototype Reactor was made to study the production of biogas

from various type of feedstock like Cow dung, Starch, Rice,

Vegetable waste, Chicken waste.


Biogas reactor 1 A 24litre metal fabricated digester was designed for

quantification of biogas. This was our first prototype in which we checked for

production of gas in Normal Digesters. The digester was initially fed with cow dung in the

ratio 1:2 with water. The digester started producing flammable gas after

3days. The digester was fed with food waste (0.2% size of the

digester i.e. 48grams). Gas produced was quantified daily.


Biogas reactor 2

The same digester was modified to have three compartments. The new three staged digester was checked in the similar way of normal digester


Optimization Maintenance of temperature and pH plays a significant role in production of

biogas. The maximum production varies as a function of temperature for different kinds of feed. Literature study showed the maximum gas production in pH range of 6.5-7.5.

For food waste, the gas production is maximum at mesophilic temperature i.e. 35oC-45oC.

The pH of the prototype digesters was measured regularly and was recorded. The temperature of the slurry was monitored.


Gas Chromatography

The gas chromatography was made to analyse the gas composition of the biogas produced. This was done in MIT,

Manipal, under the guidance and assistance of Dr. Gautham Jeppu.


Results Optimization of Biogas production

Digester Size 24 L

Feedstock 48 g

Gas Produced

Normal(Single Stage) 10.200 L

Three Stage Digester 13.800 L

Increase in production 30 %

Comparison of Production with Various Feed stock

Digester Size 2 L

Feedstock 50 g

Cumulative Gas Produced

Cowdung 11485 ml Starch 13560 ml Chicken waste 11860 ml Vegetable Waste 14025 ml Rice Waste 12465 ml


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itre

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Gas Production comparison

Normal Digester

Three Staged Digester


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ThreeStaged


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Comparison of biogas production with various

feedstock

Cowdung

Starch

Vegetable

Chicken

Rice


Conclusion

Food waste is a very good feedstock for biogas as it can produce more biogas

compared to the conventional methods

The production can be increased by 15% from a three staged digester.

Biogas yield is optimum at a pH range of 6.5-7.5.

The bacterial activity is high at mesophilic temperature(35-45o C) and greater

water feed ratio.

Cow dung should be used as an Inoculum for the production of biogas from

food waste.

Vegetable wastes can yield more biogas compared to other feedstock like

starch, Rice waste, chicken waste etc.


Thanks for listening

Documents

Optimization of food-waste based biogas digester by a ... Projects... · SAHYADRI COLLEGE OF ENGINEERING & MANAGEMENT, SAHYADRI CAMPUS, ADYAR , MANGALURU, INDIA Department of Civil