“WASTE TO ENERGYBY ANAEROBIC DIGESTION OF

VEGETABLE WASTE”

WASTE TO ENERGY

Under the Guidance of:Mr. S.K.Dubey

(Asst. Profresser, Environmental Engineering)

Department of Environmental Engineering

By:Anand Kumar Pandey (1006497003)

Jayant Khera (1006497010)Sandeep Yadav (1006497016)

Introduction• Energy generation from waste is a very good

and effective alternative.• Waste-to-energy technologies convert waste

matter into various forms of fuel that can be used to supply energy.

• Waste feed stocks can include municipal solid waste (MSW); construction and demolition (C&D) debris; agricultural waste, such as crop silage and livestock manure; industrial waste from coal mining, lumber mills, or other facilities; and even the gases that are naturally produced.

Introduction• Waste-to-energy technologies can address

two sets of environmental issues at one stroke - land use and pollution from landfills, and the well-know environmental perils of fossil fuels.

• However, waste-to-energy systems can be expensive and often limited in the types of waste they can use efficiently; only some can be applied economically today.

Introduction• Waste-to-energy technologies can address

two sets of environmental issues at one stroke - land use and pollution from landfills, and the well-know environmental perils of fossil fuels.

• However, waste-to-energy systems can be expensive and often limited in the types of waste they can use efficiently; only some can be applied economically today.

Indian Context

• India produces 150 million tonnes per annum of vegetable and fruit.

• 30% of total production is waste i.e., 50 million tonnes per annum.

• At Chandigarh 20 tonnes per day of fruits and vegetable waste is generated.

• Out of which 70% to 80% is organic waste.

Indian Context

Mumbai

Kolkata

Benga

luru

Ahmedab

adSu

ratPune

Jaipur

Nagpur

IndoreAgra

Patna

Meeru

t

Coimbato

re

Vijaya

wada

Srinag

ar

Chandiga

rhRajk

ot

Jabalp

ur

Bhubanesh

war

Jamsh

edpur

Ranch

i

Guwahati

Raipur

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Production of garbage waste in Tons/day

Major cities

Tons

Indian ContextProduction of garbage waste in Tons/day

Mumbai

Kolkata

Benga

luru

Ahmedab

adSu

ratPune

Jaipur

Nagpur

IndoreAgra

Patna

Meeru

t

Coimbato

re

Vijaya

wada

Srinag

ar

Chandiga

rhRajk

ot

Jabalp

ur

Bhubanesh

war

Jamsh

edpur

Ranch

i

Guwahati

Raipur

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

per capita production in tons

major cities

was

te g

ener

ated

per

cap

ita

Our Context

• Vegetable and fruit waste are being dumped and landfilled.

• Only 50% decomposition is there.• Due to high moisture content they can be

very good substrate for bioenergy recovery through anaerobic digestation.

Properties of WasteS.No. Parameters Values

1. pH <7

2. Total Solids(mg/L) 9933

3. Volatile Solids(mg/L) 4880

4. Total Dissolved Solids(mg/L) 5590

5. B.O.D.(mg/L) 1200

6. C.O.D.(mg/L) 3000

7. Total Organic Carbon(mg/L) 1120

(source: E.Selina Kavitah and Kurian Joseph, “Biometanation Of Vegetable Waste”, 2007)

Anaerobic Digestion

• The biological degradation by a complex microbial ecosystem of organic and occasionally inorganic substrates in the absence of oxygen.

• Generally done by reactors, Batch Reactor (wastes are fed in to the system and all the degradation steps are allowed to follow sequentially).

• Single Stage Batch Reactor is prefered over Two Stage Batch Reactor, because it’s easy and simple to operate and involves low cost.

Why Anaerobic Digestion?

• Vegetable and Fruit waste are high in organic content.

• The VSS of these type of waste is very high (around 4880 mg/l).

• This high amount of VSS results in high calorific vale that can be used for energy generation.

• In aerobic treatment the calorific value of waste reduces as it get oxidized.

• Thus anaerobic process is preferred.

Challenges

• Physical or Municipal• Handling of waste• Segregation of waste.

• Scientific or Technical• Lower pH value• Decomposition of Cellulose and Lignin

Lower pH Value• Vegetable and fruit waste contains acid, thus

the waste has lower pH value.• In anaerobic digestation it can produce fatty

acids.• By giving proper pre treatment it can be

controlled.• Pre treatment should not be aerobic as once

the waste is treated aerobically it won’t be able to produce biogas.

• Pre treatment is done by proper dosing of lime.

Cellulose and Lignin

• Cellulose and Lignin are most abundent polymers persent on earth.

• Both of natural polymer made of alot of small molecules.

• Cellulose and lignin both can be decomposed almost in same manner.

• But since lignin is somehow harder and less degradebale than cellulose.

• Lignin can be decomposed by using gram negative bacteria aerobically.

• Since generation of biogas is cann’t be done after treating the waste aerobically, thus this method cann’t be used.

• By pretreating waste with acids such as HCl and H2SO4, lignin can be decomposed.

• But this method will make the waste slurry highly acidic andthe waste is already having the lower pH value.

• Cellulose and lignin cann’t be segregated.• Conversion of cellulose into cellulose

ethanol as biofuel is under investigation.

Method Used

• Granding and Slurry Formtion• Feed to bioreactor i.e. UASB reactor, as it

is Single Step Fed-Batch Reactor.• Biogas obtained as Bi product.• Waste waste to be recycled for sluury

formation after being treated at ETP.

Mixing Tank For

Slurry Formatio

n

Grinder

Fed-Batch Reactor(UASB)

ETP

Sludge and other

residue

Organic Fraction Of

MSW

BioGas Generated

170KLD waste water

150 kld water for

recirculation

SINGLE LINE DIGRAM OF PROCESS

Formation of Slurry

• Waste collected is fed to the digestor but before feeding it must be in form that it is needed by reactor.

• For this waste is mixed with the water abd slurry is formed.

• For 20 tonnes of waste per day water required will be 150,000 L.

• As previous study shows, 200g substrate need 1.5L of water.

• Thus the slurry formed will be 170 KLD.

Design of Bioreactor

• Upflow Anaerobic Sludge Blanket Reactor is used as mentioned previously.

• Design of reactor depends upon the influent loading.

• As slurry formed is 170KLD, so reactor will be designed for this loading.

• For ease it can be designed at 175KLD.

• As lignin is a problem, then for removing it the basic principle of physics is used.

• There are some lignin which have more density than water and some have lesser.

• Thus some will float and some will sink according to their relative density.

• If the case is of full floating, then the lignin will be collected with the effluent.

• If the case is of full sink then all lignin will be setteled down.

• As study shows, 5% of total vegetable and fruit waste is lignin then it will be around 1 ton per day.

• If an additonal space at the bottom of reactor is provided for the setteled lignin then they can be collected from that and seprated out.

• The settled lignin will be collected after a fixed interval of time i.e.5 days for that 10 cum additional volume is required.

• The effulent obtained will be treated in Effluent Treatment Plant.

• The traeted effluent is again used for slurry formation.

• The ETP will consist of grit settler, any aerobic aeration process and settling tank.

• UASB is designed at SRT of around 30 to 50 days in India.

• SRT is provided so that sludge can stabilized sludge for disposal on open sand beds.

• Desired volume of UASB is calculated by calculating following:– HRT (Hydraullic Retention Time).– Organic Loading.

Once the volume of reactor is fixed then upflow velocity can be determined.

Method

Generation Of Biogas

• By providing retention time of 30days and hydraullic retention time of 40hr, the biogas will be produced.

• The production of biogas depends upon the amount of volatile component present in waste.

• Since Volatile solids present in waste is 4880mg/l.

• Thus amount of gas produced will be 0.9L/g VS fed.

• After calculation this will come out to be 746.3m3.

• Calculation for generation of biogas.

Total VSS in Waste = 4880mg/L

= 4.88 g/L

According to study L/g of biogas produced is 0.9L/g = (4.88*.9) l of

biogas produced per gram

= 4.39L of biogas

Total feed is 170kld

Thus biogas from total feed = (170*4.39) m3

=746.3 m3

Total VSS in Waste = 4880mg/L

= 4.88 g/L

According to study L/g of biogas produced is 0.9L/g = (4.88*.9) l of

biogas produced per gram

= 4.39L of biogas

Total feed is 170kld

Thus biogas from total feed = (170*4.39) m3

=746.3 m3

Result & Conclusion

• For 20 tonnes/day of vegetale waste, the amount of waste water gengerated is 170KLD.

• The UASB reactor is desigend to treat that waste water is of 280 cum volume.

• Amount of biogas generated is 746.3 m3.

• In order to attain ZLD (Zero Liquid Discharge) effluent water from UASB is treated in ETP and then recycled.

Result & Conclusion

• ETP consists of a grit settler, extended aeration or any of the aerobic method for waste water treatment and settling tank.

• The generated gas can be used directly as fuel or can be sold in compressed for and can also be utilized for electricity generation.

• The project will be suitable for both urban as well as rural areas.