INTRODUCTION

Bioenergy refers to energy derived from all land and water based vegetation as well as organic wastes which meet the energy needs of people at large. Bioenergy is available in plenty in nature and at relatively lesser cost than fossil fuels and is also free from pollution.

The different sources of bioenergy are as follows

1. Biomass

2. Biodegradable waste

3. Biofuels

4. Others

BIOMASS

Biomass is produced by green plants through photosynthesis using sunlight. Biomass contains organic matter which can be converted to energy and replenished by human effort. Biomass can be broadly classified into three categories, namely

1. Field level residues ( Paddy straw, stalks of various crops etc. )

2. Plantation crop residues ( coconut residues like fronts, stems, palmyrah tree residues etc.)

3. Agro industry residues ( Rice husk, coconut shell, groundnut shell etc. )

Biomass today accounts for over one-third of all energy used in the developing countries. The estimated power generation potential from biomass in India is about 19000 MW. Energy can be produced from biomass through gasification as well as combustion route. In combustion route, biomass is burnt to produce steam which in turn is used for power generation through turbines. In gasification process, biomass is converted into producer gas which is used for thermal or electrical application.

POWER GENERATION FROM BIOMASS

Bagasse based Co-generation

Generation of steam at high pressure for power generation in turbines and subsequent use of the same at lower pressure for process heating application is termed as cogeneration.  Conventional combustion technology is used for producing steam by burning bagasse. The sugar mills generate power through burning of bagasse. The bagasse produced during crushing season in a sugar mill is burnt in the boiler to generate high pressure superheated steam ( 87 ata & 515 ° C ). The steam is then fed into the steam turbine - coupled with alternator to produce power. The outlet steam from the turbine coming at a lower pressure is used for processing sugarcane juice to produce sugar.

The sugar mills use bagasse as fuel during crushing season and coal / other biomass during non-crushing season. A sugar mill of 2 500 TCD can produce 15 MW power.

A sugar mill without cogeneration normally consumes about 50 % of bagasse for steam generation for use in the process and the surplus is sold to paper mills fetching a minimal income while drawing power for own use from EB grid. On the other hand, sugar mills with cogeneration use the entire bagasse and produce surplus power which after meeting own consumption is exported to grid, earning higher income. This improves the profitability of sugar mills.

Tamil Nadu is No. 1 state in the country in co-generation of power from sugar mills - 3 co-operative and 16 private sugar mills have installed cogeneration plant.  The total  installed capacity under cogeneration is 446.10 MW which is 30 % of the installed capacity in the entire country and the exportable surplus is 256.11 MW as on 31.03.2008. 

View the list of cogeneration sugar mills

Cost, Incentives etc.

The tentative cost of cogeneration plant is Rs. 3.5 to 4 crores / MW. MNRE provides capital / interest subsidy. DPR has to be prepared for availing loan from IREDA / financial institutions and claiming incentives from MNRE, Govt. of India. 

Biomass based power generation

Biomass can be burnt in a boiler for production of high pressure superheated steam using conventional combustion technology that would generate power through steam. The standard pressures of steam generation are 62 ata / 80 ata / 100 ata.

The biomass based power generation projects can be set up for various purposes such as

1. Investment purposes i.e for power generation and sale of power to TNEB wherever sufficient biomass is available.

2. Generation of power for captive use in industries at lower cost than fossil fuels.

3. Biomass power projects can also earn revenue from carbon trading under Clean Development Mechanism (CDM)

Incentives, assistance etc.

* MNRE, Govt. of India

1. Fiscal incentives in terms of excise duty concession, reduced customs duty.

2. 80 % accelerated depreciation for IT purposes in the first year of installation to industries.

3. Capital subsidy @Rs.20.00 lakhs / MW subject to a maximum of 5 MW per project.

4. Tax holiday for 10 years for profit from the project.

*  (This is likely to be revised soon)

TNEB, Govt. of Tamil Nadu

1. Purchase of power at Rs. 3.15 / unit as per tariff order of TNERC

2. Concessional wheeling charges of 3 % for  distance upto 25 km and 6 % for distance beyond 25 km for captive use

DPR has to be prepared for availing loan from financial institutions, obtaining statutory clearances from various Government bodies and claiming incentives from MNRE.

View the list of Projects in operation (Total 99 MW)

View the list of consultants

New Initiatives

(a)   Taluk Level Biomass Assessment Study

TEDA carried out detailed surplus biomass availability studies in 49 taluks. District level biomass assessment study has also been carried out for the entire state of Tamil Nadu under the financial assistance from MNRE. The  draft report submitted to MNRE is under scrutiny and when it is published it would give useful information on biomass available in various Districts. 

TEDA in association with BITSUNAMI Trust carried out Biomass assessment study in 3 talukas in Nagapattinam District, which indicated the following potential.

Bitsunami Trust was formed by BITS Pilani alumini with the objective of rehabilating the December 2004 Tsunami affected villages in Nagapattinam District.  The trust has already created a coastal belt of a large plantation of casuarina trees in the villages of Naluvedaputhy and Pushpavaram in Vedaranyam Taluka.  TEDA is giving a helping hand to the Bitsunami Trust on their initiative to harness the biomass in and around these villages by setting up a Biomass based power plant.

(b)   Constitution of Standing Committee

A Standing Committee has been formed by the Govt. of Tamil Nadu to select biomass based power projects under the Chairmanship of the Chairman and Managing Director, TEDA to examine the applications from prospective entrepreneurs, select  suitable projects taking into account the availability of biomass and facilitate installation of power plants..

The Committee has selected and forwarded 27 projects for about 242 MW to TNEB out of 109 applications received by TEDA for issue of consent in the last 2 years. Consent issued for 31 projects involving total of 200.70 MW out of which 5 projects of total capacities of 54 MW has been commissioned.

ENERGY GENERATION THROUGH GASIFICATION

Biomass Gasifiers

Gasification is a process in which solid biomass material (wood waste, agro residues, branches and twigs of plants etc.) is subjected to partial combustion in the presence of a limited supply of air. The ultimate product is a combustible gas mixture termed as Producer gas. This gas has a relatively low calorific value (900 – 1100 kcal / m³). The typical composition of this gas is carbon monoxide (20 – 22%), hydrogen (12 – 15%), nitrogen (50 – 54%), carbon dioxide ( 9 – 11 % ) and methane ( 2 – 3 % ). This gas can be burnt easily and used for process heat or power generation.

Configuration

Gasifier is a vertical cylindrical unit made of mild steel / stainless steel. Different types of biomass gasifiers have been developed and based on the direction of flow of air / gas through gasifier, these are classified as down-draft, updraft and cross-draft type gasifiers. Gasification takes place in 4 distinct stages viz., drying (moisture removal takes place), pyrolysis (volatiles are released), oxidation (combustion of limited quantity of fuel) and reduction (evolution of producer gas).

Most widely used gasifier types are Updraft and Downdraft. In Updraft gasifier fuel and air flow in counter current fashion, fuel coming down from the top. In the down draft gasifier fuel and air flow in co-current fashion from top to bottom. The gas from updraft gasifier is more suitable for heating applications. The Downdraft gasifier produces a relatively clean gas with less tar and is more suitable for power generation.

Potential for Use 

1. Cooking and hot water generation for institutions

2. Process heat applications in industries

3. Crematorium maintained by local bodies

4. Power generation for electrical applications such as water pumping, street lighting etc. especially in remote places

5. Power generation for captive use in industries or for export to grid.

Tentative Cost and Subsidy
 

Preparation of DPR

The gasifier projects for a capacity of more than 100 kWe or more require Detailed Project Report (DPR) preparation  for availing incentives from MNRE. The DPR can be prepared with the help of MNRE approved consultants after carrying out detailed study of energy requirement of the beneficiary and the biomass availability.

The DPR shall cover the following aspects. 

1. Nature & description of Technology

2. Availability of proposed fuel / biomass

3. Engineering, procurement and construction

4. Project implementation

5. Estimated cost and project funding

6. Techno Economic Analysis

Systems installed in Tamil Nadu

Tamil Nadu is one of the leading states in India in the promotion of biomass gasifiers. Number of systems installed as on 31.3.2007 are as follows :

Biomass power captive / co-generation (non-bagasse) projects (subject to change)

Capital subsidy @ Rs.20.00 lakhs / MWe would be provided to promoters for installation of Biomass co-generation (non-bagasse) / projects including capative projects based on direct combustion.

The capital subsidy will be considered subject to the following :

1. The amount of capital subsidy would be calculated on the basis of installed capacity

2. CFA would be limited to a maximum capacity of 5 MW in erspective of installed capacity of the project.

Promotional incentives @ Rs.1.00 lakh / MW subject to a maximum of Rs.5.00 lakh / project to financial closure including preparation of DPR.

View the list of installations of biomass gasifiers in Tamil Nadu

View the list of manufactures / consultants

BIODEGRADABLE WASTES

BIOGAS PLANT :

Process involved

Biodegradable organic wastes such as cowdung, kitchen waste, poultry litter, night soil etc. can be potential energy sources when they are subjected to anaerobic digestion. Biogas plants work on this principle and produce methane and carbon-di-oxide. This process is also called as biomethanation Anaerobic digestion is the stabilization of organic material by bacteria in the absence of oxygen. The organic wastes undergo three stage process in biomethanation, namely,

1. Hydrolysis where the complex organic material is converted into simple compounds such as sugars.

2. Acid formation where the simple compounds are   converted into volatile fatty acids through acetogenesis bacteria.

3. In the third and final stage, fatty acids are converted into methane and carbon-di-oxide gas by methanogenic bacteria. The solid residue remaining is an organic manure.

Biomethanation technology is one of the oldest and most appropriate option for meeting the growing energy needs in rural areas. Biogas which contains methane is a clean and convenient fuel for cooking and lighting for households or for power generation in large establishments using gas engines.

Configuration

A typical biogas plant consists of the following  :

1. a digester - where the slurry (dung mixed with water) is anaerobically fermented

2. an inlet tank where dung and water are mixed

3. a gas holder / dome into which the generated gas is collected

4. an outlet tank to remove the digested slurry

5. a manure pit for digester slurry storage

6. distribution pipelines - to take the biogas to utility points

Biogas plants are classified into three categories namely,

1. Batch type - the loading of digester is done periodically and after fall in gas production, the digester is reloaded and recharged - suitable for wastes which do not mix with water easily.

2. Semi-continuous digester - feeding is done once in 3 – 4 days and suitable for cowdung, crop residues etc.

3. Continuous digesters suitable for wastes which could be mixed easily.

Commercial models

There are two types of biogas plants available in the market. These plants have capacity ranging from 2 m³ to 85 m³ of gas production.

Model 1 - KVIC ( floating drum)

This type was developed by Khadi and Village Industries Commission (KVIC) and constructed with bricks and cement mortar. The gas storage drum is made of steel / ferro cement / fibre glass. This drum moves up and down on a guide frame depending on the quantity of gas generated / stored.

To start with, cowdung is mixed with water to form a slurry (that has less than 10 % solids) and fed to the digester through the inlet tank. The anaerobic bacteria present digests the organic matter and other bio degradable materials and in that process produces methane which gets released along with carbon-di-oxide. The gas generation is directly linked to the slurry temperature. Higher the slurry temperature higher is the gas production. The digester slurry comes out from the outlet tank.

The plant capacity can vary from 2 m³ to 85 m³ and for a plant of 2 m³ capacity,        50 kg of dung would be required daily.

Model 2 - Deenabandhu ( fixed dome )

As the name suggests, this model has a fixed dome in the form of a hemisphere that  acts both as digester and gas holder. Since this model has a fixed dome gas accumulation under constant volume takes place that results in increased pressure in the gas dome. When the gas is drawn the pressure decreases. Alternate increase and decrease of pressure in the dome makes the slurry mixing very efficient. This model is also constructed out of bricks and mortar.

This model is quite suitable for toilet linked biogas plants and is available in capacities ranging from  6 m³ ( UP NEDA Model ) to 35 / 60m³ (SULAB Model).

Potential for use

Individuals                            :     Cooking / lighting in house
Local bodies / institutions     :      Cooking, water pumping
Industries                            :      Thermal  – cooking in canteens / townships       
                                                 Electrical – lighting, water pumping

 Cost & Subsidy

Tentative cost of Biogas plant of 10 m³ capacity is about Rs.2.00 lakhs depending on the model selected. The cost may go up by 30 % for installations in hilly areas.

Subsidy is available for household plants only.

No. of systems installed

          Upto    

          2002 – 03       :     Community type Biogas plants : 129

                                     Toilet linked Biogas plants       :    2

          2003 – 04       :     Toilet linked biogas plants :
           programme          Integrated sanitary complexes : 25
                                     Other Institutions                    : 15

          2004 – 05       :     Integrated Sanitary Complexes  : 16

           programme          Other Institution                        :  2

View the list of biogas plants (Toilet linked biogas plants) installed

View the List of contractors for installation of biogas plants

BIOFUELS

Biofuels are liquid fuels produced from biological materials which are renewable energy sources. Biofuels have the potential to become substitutes for conventional fossil fuels, namely, petrol / diesel oil and can help conserve the same. Biofuels have two origins,  (i) Alcohol based ( Ethanol ) and (ii)  Vegetable oil based (Biodiesel). 

Ethanol

Ethanol is also known as ethyl alcohol or fermented alcohol (C₂H₅OH). It is colourless and has a sweet flavour when diluted with water. It has a more pungent and burning taste when concentrated. It is widely used in medicines, lotions, tonics, colognes, solvents etc. Ethanol is highly inflammable, burns with light blue flame and has excellent fuel properties for spark ignition internal combustion engines.

Ethanol can be produced from molasses, corn, maize, sugar beet etc. and blended with petrol and used as fuel in motor vehicles. Usage of petrol upto 5 % ethanol mix does not require changes in engine. Ministry of Petroleum, Govt. of India has permitted blending of petrol with 5 % ethanol in 9 states including Tamil Nadu from January 2003. Vehicles have been designed and developed for using ethanol as fuel in various proportions upto 100 % in Brazil.

Potential

In Tamil Nadu, there are 38 sugar mills which produce sugar and molasses. Molasses production is about 9 lakh tonnes per annum which is used for producing alcohol in distilleries.

The following five distilleries have been permitted to set up ethanol plants

Govt. of Tamil Nadu is also promoting cultivation of sweet sorghum and sugar beet for ethanol production.

Biodiesel

All non-edible vegetable oils can be converted into biodiesel by a process called transesterification.  Biodiesel in combination with HSD can be used in diesel vehicles. The use of biodiesel in vehicles reduces emissions. Govt of India has identified jatropha and pungam for cultivation in large scale for production of biodiesel. Bio-oil is also used in some areas directly for running tractors, pumpsets in a limited way.

Potential for Use

Biodiesel can be used as alternative fuel for existing diesel engines. Biodiesel is environment - friendly and results in substantial reduction in toxic emissions from engine exhaust.

Biodiesel can be produced at the village level to meet the requirements of diesel in pump sets and other applications.

Women Self Help Groups can set up biodiesel production unit and sell biodiesel to local farmers and earn regular income. One Women SHG in Thoothukudi District has taken up production of bio-oil from pungam on a pilot basis. 

Economics

The use of Jatropha / pungam has not been tried out at a commercial level for biodiesel production and hence specific data on the economics are not readily available. But it offers considerable opportunity for employment generation, augmenting income in rural areas and achieving energy security. Ministry of Petroleum and Natural Gas, Govt. of India has announced that begining from 1.1.06 public sector oil marketing companies will be purchasing biodiesel at Rs.25.00 per litre for belnding with diesel to the extent of 20 % in phases.

OTHERS - WASTE TO ENERGY PROJECTS

Generation of wastes both in solid and liquid form is associated with industrial and other activities. Civic activities generate solid and liquid wastes while industrial activities mainly generate liquid wastes.  Both types of wastes can be used for production of energy. The different processes used for recovery of energy from waste are as follows :

1. Biomethanation 

2. Combustion  

Biomethanation is the most preferred route for recovering energy from biomass wastes as they have higher moisture and high organic content. The following types of wastes can be effectively treated through biomethanation.

1. Organic wastes can be segregated from Municipal Solid Waste and digested under anaerobic conditions to produce methane gas which in turn, can be used for power generation.

2. Sewage water, which poses a major problem of disposal, can be used in combination with other organic waste.

3. Industrial waste water containing high levels of BOD / COD.

Combustion technology is used for producing steam from MSW that contain high amount of organic non-bio degradable matter and low moisture content. The steam so produced is used for power generation through conventional turbines. 

Potential for use

Municipal Solid Waste   :   Biodegradable organic wastes can undergo Biomethanation process and produce biogas / methane which can be used for power generation. Non-biodegradable organic wastes can undergo combustion for production of steam and power generation.

Incentives and Assistance from MNRE

Energy Recovery from Urban Wastes (subject to changes)

1. Commercial projects for MSW in fact tract mode - Rs.1.5 crore / MW

2. Projects based on high rate biomethantion technology - Rs.2.0 crore / MW

3. Demonstration projects for power generation from MSW through new technologies - 50 % of the project cost subject to limit of Rs.3.00 crore / MW

4. Power generation at sewage treatment to a limit of Rs.2.00 crore / MW

5. Power generation from other urban wastes 50 % of the project cost subject to limit of Rs.3.00 crore / MW.

The financial assistance provided for any single project will be limited to Rs.8.00 crore for projects indifferent categories, mentioned above.

Energy Recovery from Industrial and Commercial Wastes (subject to changes)

Demonstration projects taken up 

Under Biomethanation the following projects have been taken up in Tamil Nadu

Wind Energy  ||   Solar Energy   ||  Other Projects