Bioconversion of different

wastes for ENERGY options

Himali MehtaPrincipal Scientist

Sardar Patel Renewable Energy Research InstituteVallabh Vidyanagar

Indian Energy Scenario

• Coal dominates the energy mix in India - 55% of the total primary energy production

• Oil - 36 % of total energy consumption

• India - one of the top ten oil-guzzling nations in the world and will soon overtake Korea as the third largest consumer of oil in Asia after China and Japanof oil in Asia after China and Japan

• Natural gas - 8.9 per cent of energy consumption in the country

• Nuclear Power - 2.4 per cent of electricity generated

• Hydropower - steadily decreased and it presently stands at 25% of total power generated

Sector-wise Energy Consumption in India

India’s Reserves, MToE

Resource Reserve Production in 2004-05

R:P

Extractable coal

29139 157 186

Extractable 1220 9 135Extractable lignite

1220 9 135

Oil 786 34 23

Gas 1101 29 38

Source: Respective ministries

The basic aim of energy security for a nation is to reduce its dependence on the imported energy sources for its economic growth.

Year-wise Increase in Oil Import

Year Quantity (MMT) Value (Rs. In Crore)

1996-97 33.90 18,337

1997-98 34.49 15,872

1998-99 39.81 19,907

1999-00 57.80 40,028

2000-01 74.10 65,932

2001-02 84.90 8,116

2002-03 90 85,042

2003-04 95 93,159

2004-05 100 1,30,000

Hence, in nutshell, the issue is:

India has world’s 17% population and only 4% of primary energy

It is a growing economy and economic growth generates energy demand

Present pattern is predominantly fossil fuel based-87% of commercial energy and 64% of total

Fossil fuel reserves are limited

• Traditionally, biomass meant wood and other woody materials which were combusted as a direct source of heat – an energy form.

• Commercially also it was an important energy source till the development of coal based economy towards the end of eighteenth century.

• Even today, traditional biomass accounts for 7% of global • Even today, traditional biomass accounts for 7% of global energy demand.

• Primary sources of biomass could be agricultural crops, wood or aquatic biomass where as secondary sources could be crop residues and organic wastes from households,

agricultural operations and industries.

There are a variety of conversion technologies for conversion of biomass to various forms of energy – power, heat and fuels – for potential usages in

different sectors.

Biomass conversion routes for bioenergy

The definition of biomass extends well beyond wood and

woody type of material.

There is another category of organic matter which is high in moisture and low in lignin. moisture and low in lignin.

Leaf and other leafy biomass, animal and human wastes, crop residues, wastes from certain industrial operations and municipal solid waste falls in this group.

The potential of these materials could be extracted through microbial conversion pathways of either digestion or fermentation.

Fundamentals of Anaerobic Digestion

Cattle Dung based Biogas Plants

Alternative Feedstocks

• Banana stems

• Water hyacinth

• Eucalyptus leaves

• Composite agricultural • Composite agricultural wastes

• Kitchen waste

Utilization of Kitchen Waste through Biomethanation

KitchenKitchen

Waste

Pollution

Disposal

Cooking

Biogas

Fertilizer

Digested slurry

Biogas plant

Cooking

Kitchen waste fed, kg/day 140

Biogas generated, cu. m./day 14

Performance of Kitchen Waste Biogas Plant

LPG saved, kg/day 7

Kitchen waste biogas plant at Bayer ABS Ltd., Nandesari

Capacity: 20 cu mYear of installation: 2000

Kitchen waste biogas plant at air force, Agra

Capacity: 5 cu mYear of installation: 2001

Biogas from Jatropha Deoiled Cake

Around 320 litres of biogas with 66% methane can be produced from one kg of produced from one kg of jatropha deoiled cake

Fruit and Vegetable Waste

Towns and cities : 4,000Waste generation : 50,000 tpd

Installed capacity of fruits and vegetables processing industry : 2.1 million tpdindustry : 2.1 million tpd

Schematic Diagram of Biphasic Biomethanation

Biomethanation system (10 T/d) at Jain Irrigation Systems Pvt. Ltd, Jalgaon

Anaerobic filter at Vidya Dairy, AnandAnaerobic filter at Vidya Dairy, Anand

Comparative Economics of Comparative Economics of Aerobic and Anaerobic SystemAerobic and Anaerobic System

Parameter Aerobic system

Anaerobic system

Quantity of effluent, (l/d) 2,50,000 2,50,000

Influent COD, (mg/l) 4000 4000

Effluent COD, (mg/l) 150 450

Electricity used, (kWh/d) 700 20

Cost of aeration @ Rs.5.5/kWh 3850 110

Chemicals used, (kg/d) 35 -

Cost of chemicals, @Rs.75/kg 2625 -

Expected biogas production, (cu m/ d) - 390

Electricity equivalent of biogas, (kWh/d) - 650

Value of electricity produced, (Rs./ d) - 3575

Burnt wheat straw (Gujarat)

Cotton stalks on fire (Gujarat)

Uncontrolled burning of rice straw (Punjab)

The smoke screen (Punjab)

The charred field (Punjab)

Availability of Crop ResiduesAvailability of Crop Residues

• SPRERI considered crop residues, which are burntat present, as surplus; estimated 70 milliontonnes per year; Punjab alone burns about 14million tonnes of paddy straw during Octobermonth each yearmonth each year

• SPRERI conducted a study and developed atechnology package for collection, transportationand storage of 1,000,000 tonnes of straw/yr

Crop residue to fuel gas and compost

Biomethanation of dry crop residues at thermophilic temperatures

and of cattle dung at mesophilic temperatures

200

250

300

350

Cu

mm

ula

tiv

e b

iog

as

pro

du

cti

on

, l/k

gT

S

305 l/kgTS

Thermophilic fermentation

(Rice straw)

227 l/kgTS

Thermophilic fermentation

(Sugarcane trash)

0

50

100

150

1 5 9 13 17 21 25 29 33 37 41 45

Incubation period, days

Cu

mm

ula

tiv

e b

iog

as

pro

du

cti

on

, l/k

gT

S

227 l/kgTS

143 l/kgTS

Mesophilic fermentation

(Cattle dung)

218 l/kgTS

RICE STRAW

1T (DM) / HR

BIOGAS > 55 %

CH4 154 m3 / HR

77 LOE / HR

SEMI-DECOMPOSED

SOLID RESIDUE

0.7 T (DM) / HR

Energy & Compost Output of an Anaerobic Plant Converting

1 t rice straw / hr

BOILER ENGINE

450 kW

TURBINE

ENRICHED COMPOST

0.63 T (DM) / HR

ANNUAL OUTPUTS

ENERGY COMPOST

GROSS 3,400,000 UNITS

NET 2,890,000 UNITS

6,350 T

(25 % MC)

Outputs of Bioconversion of Rice Straw

Capacity Biogas (m3) per

dayper yr

Oil equivalent per yr (T)

Electrical energy

(kWh) per yr

Compost(T of d m) per yr

1 T / day

3009 x 104

45 14.6 x 104

(20 kW) *120

1 T / hr 7,2002.16 x 106

1,080 3.56 x 106

(500 kW)*2,880

10 T / hr

72,0002.16 x 107

10,800 3,56 x 107

(5 MW)*28,800

* 24 hr/day operation

• Extensive research is also underway for converting biomass into various transport fuels such as ethanol and butanol through the process of hydrolysis, saccharification and subsequent fermentation of these sugars.

• Technology using molasses and maize as substrate has been established though there are only a few pilot installations as the process is not yet economically viable for commercialization.

• However, throughout the world efforts are on to use various agro-residues as substrate, produce low cost enzymes, develop genetically modified microorganisms to give better yield in order to improve the economics of the whole process.

Comparison of Potential of Ethanol and Enriched Comparison of Potential of Ethanol and Enriched Biogas ProductionBiogas Production

Rice straw (1 ton)Rice straw (1 ton)

Cellulose/hemicelluloseCellulose/hemicellulose Biogas (275 m3)Biogas (275 m3)(600 kg)(600 kg) Methane (151 mMethane (151 m

33) )

equivalent toequivalent toPetrol 125 kg or 168 l)Petrol 125 kg or 168 l)Petrol 125 kg or 168 l)Petrol 125 kg or 168 l)

Sugars (300 kg)Sugars (300 kg)

Alcohol (133 kg or 168 l)Alcohol (133 kg or 168 l) Fuel CV (MJ/kg) SGFuel CV (MJ/kg) SGequivalent toequivalent to

Petrol (88 kg or 118 l) Petrol (88 kg or 118 l) Ethanol 30.14 0.794Ethanol 30.14 0.794SugarSugar 16.74 16.74 --Petrol 45.50 0.794Petrol 45.50 0.794

Hydrogen Synthesis

A little lesser explored aspect of the digestion process is hydrogen synthesis by suppressing methane production and then power generation through fuel cell route. route.

Certain technological interventions like heat treatment, use of inhibitors, maintenance of low pH etc. are being explored wherein hydrogen formation becomes a preferred pathway for the microorganisms involved thereby curbing methane formation.

Direct Extraction of Oils

• A variety of non-edible oilseeds are available in nature; most widely adopted among them for fuel-oil are jatropha, neem and karanj.

• These raw oils could be directly used for cooking or in engine-generator for power production.

• By dewaxing, degumming and transesterification of these oils, biodiesel could be produced which has diverse application than the raw oil.

• Apart from the use in engine-generator for power production, biodiesel could also be used as transport fuel.

Algae – Potential Fuel for Future

• A certain varieties of aquatic biomass also have a huge potential to develop as energy source for future. Algae, a photosynthetic, aquatic organism having a very high biomass production rate (more than perhaps 100 dry tons/hectare/year) contains varying amount of lipids (2-40% by weight), carbohydrates and proteins.

• According to an NREL (National Renewable Energy Laboratory) report, based on the photosynthetic efficiency and growth, annual algal oil production could be more than algal oil production could be more than 30,000 litres per hectare.

• This algal oil could be used to produce biodiesel.

• Once lipids/oils have been extracted, the left-over cake is primarily composed of carbohydrates and proteins which could be put through anaerobic digestion to produce biogas.

• Alternatively, carbohydrates • Alternatively, carbohydrates could be microbiologically converted into sugars for further fermentation to ethanol.

• Thus, algae give rise to the interesting possibility of producing both biodiesel and ethanol or biodiesel and biogas.

Biogas applications

Biogas could be used for:

direct thermal applications

as transport fuel after purification

Power production through an engine-generator

The technologies for these options are well established

Future Actions ?

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