ENERGY GENERATION BY HOT ROCK ENERGY (HDR) TECHNOLOGY

Hot Rock Energy is a vast, environmentally friendly, economically attractive energy source.

The concept is very simple.

Water is injected into a borehole and circulated through a “heat exchanger” of hot cracked rock several kilometres below the surface. The water is heated through contact with the rock and is then returned to the surface through another borehole where it is used to generate electricity. The water is then re-injected into the first borehole to be reheated and used again.

 

Hot Dry Rock Geothermal Energy

HDR geothermal energy relies on existing technologies and engineering processes, and is the only known source of renewable energy with a capacity to carry large base loads. The concept behind HDR geothermal energy is relatively simple. Heat is generated by special high heat producing granites located 3km or more below the Earth’s surface. The heat inside these granites is trapped by overlying rocks which act as an insulating blanket. The heat is extracted from these granites by circulating water through them in an engineered, artificial reservoir or underground heat exchanger.

 

HDR geothermal energy relies on existing technologies and engineering processes such as drilling and hydraulic fracturing, techniques established by the oil and gas industry. Standard geothermal power stations convert the extracted heat into electricity. HDR geothermal energy is environmentally clean and does not produce greenhouse gases.

It has been classified as renewable by National and International authorities.

 

The Hot Rock Energy system works with two closed circulation loops

 

The subsurface loop

This loop circulates water down an injection borehole where it passes through the

underground “heat exchanger” and is heated. The superheated water is then recovered by one or more production boreholes which return it under pressure to the surface. By keeping the water under pressure and preventing it turning to steam, any materials dissolved from the underground rock mass (such as silica or carbonates) are kept in solution and can be returned to the ground.

 

At the surface, the superheated water is passed through a metal heat exchanger where most of the heat is removed. The now cooled water is then returned to the injection borehole where it is sent down again to recover more heat.

 

The power station loop

 

At the surface a second closed loop fluid system is used to transfer the heat into the power station and generate the electricity in a turbine. The fluid used in the power station loop can be water, but more usually a lower boiling point fluid is used. Organic fluids such as refrigerants and iso-pentane are often used.

 

The HDR Energy Extration Process

All modern HDR development work is based on the relatively simple concept described in a US Patent issued to Los Alamos when HDR technology was more theory than reality. A well is first drilled into hot, crystalline rock. Water is then injected at pressures high enough to open the natural joints in the rock, thereby creating an engineered geothermal reservoir.

 

The reservoir consists of a relatively small amount of water dispersed in a very large volume of hot rock. The relative dimensions and orientation of the reservoir are determined by the local geologic and stress conditions, while its ultimate volume is a function of the duration of the hydraulic fracturing operation and the fracturing pressures applied.

 

Seismic techniques are used to follow the growth of the reservoir, to assess its location, and to determine its approximate dimensions. Using the seismic data as a guide, one or more production wells are subsequently drilled into the engineered

reservoir at some distance from the first well. In a properly engineered HDR reservoir, there are a number of fluid-flow pathways between the injection and production wellbores.

 

Operation of an HDR heat mine is extremely simple. A high-pressure injection pump

provides the sole motive force to circulate water through the engineered reservoir and deliver it to a power plant on the surface. The hydraulic pressure applied via the injection pump also serves to keep the joints within the reservoir propped open. The operating parameters applied to the injection pump thus greatly affect both the flow rate through the reservoir and its instantaneous fluid capacity. By using a  Combination of injection and production control measures, an almost limitless variety

of operating scenarios may be employed to mine the heat.

 

The Major Components of a HDR System

1. One, or more, hot dry rock reservoirs are created artificially by hydraulically fracturing a deep well drilled into hot, impermeable, crystalline basement rock. The hydraulic fracturing, achieved by pumping water into the well at high pressure, forces open tiny pre-existing fractures in the rock, creating a system or “cloud” of fractures that extends for tens of meters around the well. The body of rock containing the fracture system is the reservoir of heat. The fracture system provides for the heat transport medium, water, to contact a large area of the rock surface in order to absorb the heat and bring it to the surface. More than one reservoir could supply hot water to a single power plant.

 

2. Deep wells are meant for production and injection of water. The wells are drilled with conventional rotary drilling technology similar to that used for drilling deep oil and gas wells. The total number of wells and the ratio of production wells to injection wells may vary. Experimental HDR systems to date have typically involved one injection well and one production well. The earliest commercial HDR systems will likely include a “triplet,” two production wells for each injection well. A triplet of deep wells will support about 5 MW of power plant capacity, assuming adequate flow rates and fluid temperature. It is possible that other well configurations, such as a

quadruplet (3 production wells per injection well) or a quintuplet (4 production wells per injection well) could be used.

 

However, the cost effectiveness of using a quadruplet or quintuplet has not been established. Also, the ellipsoidal, rather than spherical, shape of the fracture pattern at Fenton Hill suggests that one production well on each side of the injection well, on the long axis of the reservoir, is the logical configuration. For these reasons, this analysis is limited to a ratio of two production wells per injection well, with earlier commercial systems limited to three wells total, and later systems using multiple triplets of wells. The original well, from which the fracture system is created, is

used for injection. Two additional nearby wells are drilled directionally to intersect the fracture system and are used as production wells. Operation of the system involves pumping water into the fracture system through the injection well, forcing it through the fracture system where it becomes heated, and recovering it through the production wells.

 

3. A system of microseismic instruments in shallow holes around the well that is being fractured is used. During the fracturing operation, this system gathers seismic data, which is used to determine the extent and the orientation of the hydraulically created fracture system. This information is then used to guide the drilling of the production wells so that they intersect the fracture system at depth. Although the HDR system, once it is completed, can operate without it, the microseismic system is included here because itis an integral part of creating the HDR reservoir and because it may be left in place to gather additional information which could be useful later in

the life of the HDR system.

4. A shallow water well to provide water (or other source of fresh water).

5. Surface piping, or gathering system, to transport water between the wells and power plant.

6. A binary power system is used to convert the heat in the water to electricity. This system is comprised of the following major components:

a. One or more turbines connected to one or more electric generators.

b. A heat exchange vessel to transfer heat from the hot water to a secondary working fluid with a low boiling temperature.

c. A heat rejection system to transfer waste heat to the atmosphere and condense the vapor exiting the turbine. A wet, or dry, cooling system can be used. The capital cost of a wet cooling system is only marginally less expensive than for a dry cooling system.

However, this cost advantage is largely offset by the higher operating cost of the wet

cooling system. For this reason, and since HDR sites in the U.S. are likely to be in arid areas with limited water supplies, this technology characterization is limited to a dry cooling system.

d. Injection pump(s) circulate the water through the HDR reservoir.

e. Pumps repressure the working fluid after it condenses and a vessel storing the working fluid.

f. Electrical controls and power conditioning equipment.

 

Development of an Engineered Artificial Reservoir

Granites have an internal fabric of cooling joints and fractures, a result of cooling down from a melt (like molten glass) to a solid that we see today. Developing an underground heat exchanger involves increasing the hydraulic pressure at the bottom of a deep drill hole (approx. 4- 5km) until the existing fractures and joints are slightly opened.

HONGE OIL AS A BIODIESEL

There are near about 300 varieties of non-edible oil seed bearing trees in India. Many of the foresters were of the view that the Honge Tree is God’s gift to India. It is very versatile tree that grows in land as well as in coastal area and all these without much care. Growing these trees enhances the maintenance of environment of the surrounding and offers employment opportunities. Honge oil is extracted from the seed of Honge tree, whose Latin name is Pongammia Pinnata and whose international name is Pongammia Pinnata Perry. Honge oil can be produced on a commercial scale provided the right strategies are followed.

 

The performance of the engine with Honge oil is found to be satisfactory. The viscosity of Honge oil has to be corrected by preheating the oil. The output of the engine remains almost the same though the calorific value is slightly lower. Taken into account the sale value of cake which is a good fertilizer, Honge oil works out to be cheaper (i.e. Rs 13 per kg) compared to current price of diesel. The high viscosity of Honge oil interferes with injection process and leads to poor fuel atomization. The high viscosity has to be overcome by using methyl ester honge oil. The  transformation of Honge oil to its methyl ester reduces molecular weight to one third, reduces viscosity to one eighth and increases the diesel index.

Karanj and Jatropha cultivation

Bio Diesel is source of energy, supplement for Petroleum products. Bio Diesel is manufactured by using different edible and non-edible oils but edible oils use is not economical and no surplus production for costing purposes. So other sources are non-edible oils, such as Karanj oil, Neem oil, Mahua Oil, Jatropha oil, and Karanj oil. In compression ignition and spark ignition engines for different utilities Since India can not affroad the use of edible vegetable oils as power sources because of short supply, Researcher and planner suggested the use of non edible vegetable oils as alternatives fuels like Pongamia, Jatropha and Neem etc .As India consists of 40% of waste land .It is develop all theses lands by growing non edible oil plants which not only gives the oil but also enriches the environment by adding the green forest cover for Ecological balance.

 

According to Indian climate and Research Government of India decided to undertake plantation of Karanj and Jatropha plants in barren, waste and unfertile soil from North to South and East to West, Government of India decided two Non Edible oils from Karanj and Jatropha plants are suitable for Biodiesel manufacturing.

 

So it is better to use the available plants, which produce the non-edible oil seeds to cater the needs at rural level for self-sustainability. Though there are more than 300 different species of trees which produces oil bearing seeds, pongamia and jatropha are the drought resistant plants, which grow with limited water which has enough potential to meet the fossil fuel demand at rural level. Hence these plants can well be utilized to produce the Biodiesel at rural and industrial level. Karanj plant is known by different names as per local level. Pongamia pinnata is botanical name from leguminosea family. It has different uses, medicinal as well as Ayurvedic. Karanj has long life from 60 to 80 years. It has tendency to stay in drought condition, no need of irrigation. Karanj plant is resistant to diseases and insects free. They also used as road shading tree because it is green in summer also. So it helps to increase the natural beauty and decrease the soil erosion. Karanj cake and leaves also helpful in organic manure accordingly it helps to increase the economy of Indian farmers.

 

Now a days agriculture forestry Dept. worked on different varieties of Karanj plant for high yielding and high oil percentage. Some institutions like SUTRA, Dept. of Mechanical Engg., Indian Institute of Science, Bangalore has developed the hybrid variety by grafting which is high yielding and oil percentages. Planting methods, fertilizers and new techniques also developed. Stump technique is method in which plants are grown for one year in nursery and transfer in the field after one year by making stump shape by removing leaves and branches which is more convenient for transportation. It saves the money and nursery accessories. Other technique is tissue culture, helps to produce good quality seed plant in short time.

 

Jatropha curcus is plant belongs to Euphorbiaceae family known by Mogali Erand, Ratan jyot, Ratna jyot in Telagu Nepalam and Yellamunaka, in Kannada Kadalabudu.etc. in different regions of India . Jatropha plant is used by local and Adivasi people for different purpose. All parts of plants are used by local people. It has medicinal value. Its roots are used against Aatisaar, stem used for dental problem an4 tooth cleaning, leaf extract also useful in cattle problem.

 

Benefits of Karnj and Jatropha cultivation: -

• Cultivation of Karanj and Jatropha plants prevents soil erosion and makes the soil fertile.

• Cost of cultivation is low as compare to other plants.

• Low requirement of water and also stay in low ground water level.

• Seasonal and regional acceptance.

• Often cheated by unfavorable monsoon.

• Lack of insurance coverage.

• Long life plant

• Low insect and disease damage.

• It increases rural employment.

• Pollution control.

 

Bio-Diesel Plantation Requirement

PRESENT CONSUMPTION OF DIESEL 3 CRORES 70 LAKH TON

IF 20% BIODIESEL USED WITH DIESEL REQUIRED 70 TO 80 LAKH TON BIODIESEL OIL

80 LAKH TON OIL REQUIRED

FOR 80 LAKH TON OIL REQUIRED 

1 CRORE HECTRE LAND FOR PLANTATION

Biodiesel program in India

In India most of the trials were done using bio diesel from Karanj and Jatropha.

 

Indian Railway Conducted a successful trial run of an Express Passenger train on the Delhi-Amritsar route using 5% of biodiesel as fuel. Indian Oil Corporation began in January 2007 field trials of running buses on diesel doped with 5% biodiesel. Hariyana Roadway buses used of Biodiesel. Automobile manufacturers like Mahindra and Mahindra, Ashok Leyland etc. have already tried biodiesel mix as a fuel for their vehicles. Harbinsons Biotech Pvt. Ltd. has set up pilot plant at Gurgaon. IIT Delhi, IIT Chennai, have already set up a biodiesel products facility of 60 kg/day at Faridabad. Mahindra and Mahindra Ltd. has a pilot plant using Karanj for Biodiesel production in Mumbai.

 

What are biofuels

 Renewable fuels from biosources includes : -

1. Ethanol

2. Biodiesel

3. Biogas

Why Biofuels

• Pollution threat

• Reduction of green house gas emission

• Regional development

• Social structure & Agriculture

• Security of supply.

Importance of Biodiesel

• Environment friendly

• Clean burning

• Renewable fuel

• No engine modification

• Increase in Engine life

• Biodegradable & non toxic

• Easy to handle and store.

 

 

Sr.	Parameters	Quantity	Rs in crores
1	Imports Currently Petroleum Products	70%	1,27,000
2	Petroleum Products Demand target (200-07)	120.4 MT
3	Domestic Production of Crude oil and Natural gas	33.97 MT
4	Huge gap between Demand and Production	86.43 MT
5	Current Consumption of Diesel in India Approx	40 MT
6	Consumption Expected to reach in 2006-07(5.6%)	52.32 MT
7	Crude Oil Requirement	105 MT
8	Imports of Crude Oil	70.00%
9	Present Production of Crude oil	30.00%
10	Demand of Crude oil in 2006-07	78.00 MT

 

The economy of a country mainly depends upon its energy source. Energy source is the main contribution factor for the development and growth of the developing countries. Among the various sources identified for alternate fuel Non-edible oils were considered to be ideal in view of compatible properties with respect to diesel. This Biodiesel concept is been adopted with Jatropha and Karanj oils in our country.

 

India has vast tract of degraded lands, mostly in areas with adverse Agro – Climatic condition, where hardy tree bone oil seed Species like jatropha, Karanj, etc. can be grown easily. Even 30 million Hectares planted for Biodiesel can completely replace the current use of Fossil fuel. Our oil bill is presently $ 6 Million a Year and the Waste Land Development would required only about 1000 Crores per Year for 20 Years to make India self sufficient forever in oil. Developing A strong market for Biodiesel would have Treatmendous economic Benefits. Investment in Biodiesel will have great

Future.

BIODIESEL FUELS FOR THE FUTURE

India is the sixth country in the world with a billion population. Our country faces problems in regard to the fuel requirement for increased transportation demand and now imports about 70 % of its petroleum requirement .The petroleum import bill is about 14 billion dollars. The current yearly consumption of diesel oil in India is approximately 40 million tones forming 40 % of the total petroleum products consumption. The potential demand for Biodiesel at 20% blend is estimated at 13.38 million tones per annum by 2012. In the present problematic traditional cultivation, raising of energy plantation to produce Biodiesel, farmers can develop and utilize waste lands and improve incomes, rural labour will have more employment opportunities and soil fertility and condition will improve. Any vegetable oil can be converted in to Biodiesel; however, in India there is no surplus production of edible oil. Therefore, the oil that can be used as Biodiesel has to be non-edible oil.

 

Produced in abundance and with stand harsh climate, as they would be taken up in wastelands, the most suitable species in this regard are Jatropha and Pongamia. These plants could be grown on wasteland about 80 million hectares of which is available in India. The oil extracted from the seed is used in place of diesel after simple filtration. After further processing this can be used in four wheelers. The seed cake after extraction of oil will be very good organic manure as it contain high nitrogen content. This cake can also be utilized for biogas production. The pruned leaves are used as green leaf manure.

BIO-GAS -A BOON FOR RURAL ELECTRIFICATION SYSTEM

The world today is behind two resources – energy and water. Over the years man has utilized positively or negatively various conventional resources to satisfy his needs and greed. Thus, limited storage of resources have been depleting steadily. Hence the propagation of non-conventional energy sources and their utilization is imperative today.

 

Why Bio-gas?

Bio gas generated from locally available waste material seems to be one of the answers to the energy problem in most rural areas of developing countries. Gas generation consumes about one fourth of the dung but available heat of gas is about 20% more than that of obtained by burning the entire amount of dung directly. This is mainly due to very high efficiency (60 %) of utilization compared to poor efficiency (11%) of burning dung cakes directly. The technology thus seeded and spawned is populist technology based on ‘Nature’s income and not on nature’s capital’ so being an agricultural country use of bio-gas as a fuel for cooking or lighting purpose can be the best solution for all Indian farmer families.

 

Potential for Bio-gas energy

The potential of renewable energy in India is estimated as 1,00,000 MW while for bio-gas and bio-mass it is 19,500 MW. So there is need to bring about change in mind to focus on renewable sources of energy. No matter whether you get the power from Thermal Power station , Hydro Power Plant or from Bio-gas Plant, the end product is energy and power.

 

Bio-gas technology – General Description

Bio-gas or gober-gas is clear, odorless combustible gas which is produced when organic matter content in animal excrements like dung, human night soil, parts of a tender plants or residues like leaves, stems and straws are anaerobically fermented with the help of methenological bacteria in air and water tight containers called bio-gas digester.

 

Chemically, a useful gas is just a methane gas. It’s chemical composition consist of one part of carbon (C) and four parts of Hydrogen molecule. It’s chemical formula is CH4 .Bio-gas burns with clear blue flame without giving any smoke. It’s flame temperature is up to 800 oC and it has calorific value of 5650 KCAL/ m3

 

Technical aspects

Bio-gas is a mixture of :

Methane (CH4 ) : 50 to 70 %

Carbon-dioxide (CO2) : 30 to 40 %

Hydrogen (H2 ) : 5 to 10 %

Nitrogen (N2 ) : 1 to 2 %

Hydrogen Sulphide (H2 S) : Small quantity

 

Bio-gas is generated when bacteria degrade biological material in absence of oxygen process known as anaerobic digestion. This process produces less temperature hence valuable in terms of energy conservation.

 

Advantages

One cubic meter of biogas is equivalent to –

3.47 Kg of wood

0.63 liter of kerosene oil

0.61 liter of diesel oil

1.5 Kg Of coal

1.25 KWh of electricity

0.45 Kg of LPG

13 Kg of fuel dung

0.5 Kg of butane.

 

 

It is non polluting

It gives cheap and easily available energy.

It uses waste like animal and human excreta and plant residues, which can otherwise create undesirable conditions. So it can give hygienic, clean and safe atmosphere around populated areas.

Its slurry could be used as a nutrient rich manure in farms and could tremendously improved agriculture production.

It can substitute firewood for cooking, heating, fuel and kerosene for lighting so saving in foreign currency normally spent in fuel and fertilizers.

 

Socially it can save a lot of time and labour in activities such as cleaning, washing and cooking, which they can use for other income generating /saving activities to care more for their children and to learn.Environmentally information technology can save wood and through that help to save vulnerable forest, soil, water and clean of the environment.

Agro Waste Potential

The agricultural waste is a low-density biomass, scattered all over the country. Also, it is available in a wide variety of forms having a wide variety of physical and chemical properties. As a result, in spite of its tremendous potential as a renewable source of energy, it has remained more or less neglected by the energy planners as well as technocrats. Also, almost all attempts at finding economically feasible ways of using biomass as a source of energy on a wide scale have proved unsuccessful and unsustainable. We however, believe that it is techno economically feasible to use biomass as a source of energy.

 

An excellent example of the right approach to use of biomass energy is a chain of technologies developed and successfully commercialized by Appropriate Rural Technology Institute.

 

Every year, farmers in Maharashtra state alone are simply burning off millions of tons of sugarcane trash (dried leaves of sugarcane left in the field after harvesting of the cane). In 2005, the government undertook a project that attempted to explore means of converting this biomass into a value added fuel, namely char briquettes. Under the project an oven-and-retort type charring kiln was developed. It converted sugarcane trash into powdery char. The charring kiln can be easily dismantled and transferred from one location to other, thereby eliminating the need to transport large quantities of loose biomass. Operated as a continuous batch process, it consumes about 250 kg of trash to generate about 50 kg of char powder every day. Three unskilled labourers can operate two kilns simultaneously to produce 100 kg char powder per day. The powder can then be briquetted by using a briquetting machine. The production cost of the briquettes is about Rs. 8 per kg.

 

Kerosene, which is the preferred cooking fuel for of the urban poor, is getting costlier and costlier as the government is gradually withdrawing the subsidy on it. We felt that the char briquettes made from agricultural waste could be a suitable low cost alternative fuel for the urban poor. However, switching from one form of fuel to other also requires a switch over from one type of cooking stove to other. It was, therefore, necessary to develop a cooking stove that was designed to suit the combustion characteristics of the char briquettes. Therefore Sarai cooker was developed. The cooker combines the principle of a hotbox, with the principle of a fuel-efficient stove. The result is so energy efficient that it requires just about 100 gm of char briquettes to cook vegetables, rice and dal for a family of five, and another 50 gm or so for roasting rotis on the charcoal burning stove which is part of the cooker assembly. Even if the briquettes are available in the urban market at the rate of Rs.10 per kg, the Sarai system requires fuel worth just about Re.1 per meal. No other fuel-stove system has such a low operating cost.

 

The concept has taken off very well among urban as well as rural households in rice eating localities in Maharashtra. The reason for it is its practical feasibility which is as follow:

1. Conventional thinking had always focused on producing tons of briquettes in a centrally located factory. This involves collection and transportation of widely scattered and low density raw material, and the transportation cost itself renders the entire project impractical. Our approach of decentralized production of char, and transportation of the char to a centrally located briquetting facility makes more economic sense.

 

2. The Sarai cooker is assembled using components already available in the utensils market. Thus, the production of the cooker does not involve any dedicated machinery or infrastructure. As a result, the cooker can be produced at a relatively low cost of about Rs.350-500 (depending mainly on the cost of stainless steel) making it affordable for the target users and profitable for the producer and retailers.

 

3. Because of the efficient design of the stove, the quantity of fuel required per meal is very less, keeping the cost of fuel per meal cooked at the lowest possible level for the consumer. This allows the per kg cost of the briquettes to be high enough to provide sufficient net income to the char producers, the briquetters, as well as the retailers. This example clearly demonstrates that it is possible to find ways of using biomass energy in techno economically feasible ways. Considering the huge amount of agrowaste produced annually in India, it can be easily seen that the chain of technologies described here can have a tremendous positive impact on the rural economy of the country.

WEALTH FROM AGRO WASTE

Agricultural out put from India has seen phenomenal growth. Factors, which contributed to the development, were research in seeds, access to water and power, effective pesticides, communication and improvement in storage facility. With the growth in production of agricultural output agro-waste production is also increased. However, local thermal energy which are needs of rural sector were mainly managed through cow dung, wood, kerosene and lately LPG. Agro mass had few takers. In fact, storage of agro-mass posed problems such as security risk due to fire hazard, growth of pests, blockage of covered space etc. Simplest solution, which is even practiced today, is spread the waste and burn it. On the other hand, in urban sector industrial growth is pushing the energy needs to hilt. Queues at petrol pump and chimneys spewing, fossil fuel burnt CO2 are the concerns. Indian government had recognized and efforts to use biomass were started in 1980’s. Some of the difficulties, which were noted in use of biomass, were:

 

       Low bulk density and tendency to scatter around.

       Moisture content.

       Transportation costs.

       Drying and briquetting

 

Fiscal and economical incentives were announced and that led to installation of various briquetting plants. Early birds however, did not have the beginner’s advantage. On the contrary arm twisting techniques of urban buyers, poor credit facility, enforced most of the entrepreneurs to shut the shop. Today however, due to movement called clean development mechanism, renewed vigour is felt in this area.

 

Briquetting process

The briquetting process is pretty simple. The machinery involved is a simple reciprocating machine that compresses the bio-mass to one fifth volume. The mechanical pressure exerted on the biomass is equivalent to 1350 kg/cm2. Due to this high-pressure mechanical operation, there is heat generation, which evaporates the entrapped moisture and gives a polished finishing. The compacted biomass is extruded through a die, which also decided the diameter of briquette. Some raw materials are wet and do not form good solid compact briquette. There is a separate dryer provided in the system for making the material suitable for briquetting. Lubricating oil cooling system and electrical system are additionally required for briquetting plant. Power requirement for briquetting plant is proportional to tonnage. A broad requirement of 60 Units per ton of briquette can be considered as benchmark.

 

Raw Material

Though biomass is a very popularly talked about term, the real meaning of it is not clearly understood. Particularly, in the context of briquette manufacturing, all bio degradable agro wastes can be easily briquetted. The briquettable bio mass need not be always raw material in the same form. High moisture content bio mass needs be solar dried or dried by fuel firing before briquetting. Some of the raw materials are not easily briquetted. It is necessary to add agro or synthetic binders. Briquettes made out of such binders are not of desired quality, as the binders do not mix thoroughly and uniformly.

 

Business effectiveness

Manufacturing of briquette can be classified as high volume low cost business. Approximate breakup 45% raw material, 15% raw material transportation, 15% Power, 10% Investment (full production), 9% Other expenses and 6% Profit. Thus, it is essential to procure raw material in time. The rural sector demands immediate cash payments. Therefore, liquidity by prompt recovery of dues is necessary. Business is quite sensitive to cost of transport fuel. Convenient Transporters who are having two-way business offer low rates. Planning of loading unloading manpower, knowledge of status of inventory at user end can affect profitability substantially.

BIOMETHANATION PLANT

A reviewed interest in renewable energy and related conversion technologies is emerging again. Although the eventual depletion of fossil fuels lurks in the background as a long-term incentive for the development of sustainable energy forms, more urgent incentives to re-emphasize renewable energy are related to global environmental quality. The first concern to emerge was release of toxic compounds and oxides of nitrogen and sulphur resulting from combustion of fossil fuels. These air pollutants contribute globally to health and environment problems, the most common of which is referred to as acid rain. The greatest threat is that of global warming related to an increased concentration of carbon dioxide and other upper atmospheric pollutants resulting from anthropogenic activities.

 

Use of renewable biomass (including energy crops and organic wastes) as an energy resource is not only greener with respect to most pollutants, but it’s use represents a closed balanced carbon cycle with respect to atmospheric carbon dioxide. It could also mitigate atmospheric carbon dioxide levels through replacement of fossil fuels. A third concern is the recognized need for effective methods of treatments and disposal of large quantities of municipal, industrial and agricultural organic wastes. These wastes may not only represent a threat to environmental quality, but also represents a significant renewable energy resource.

 

Why methane?

Biomass may be converted to a variety of energy forms including heat, steam, electricity, hydrogen, ethanol, methanol and methane. Selection of product for conversion is dependent upon a number of factors including need for direct heat or steam, conversion efficiencies, conversion and use of hardware and environmental impact of conversion process, waste stream and product use. Compared to other fossil fuels methane produces few atmospheric pollutants and generates less carbon dioxide per unit energy because methane is comparatively a clean fuel. The trend is towards its increased use for appliances, vehicles, industrial applications and power generation. Ethanol is becoming a popular biomass – derived fuel.

 

Conversion processes

Methane can be produced from biomass by either thermal gasification or biological classification. Economic application of thermal processes is limited to feeds with either low water content or those having the potential to be mechanically dewatered inexpensively. Feedstocks containing 15% of total solids require all of the feed energy for water removal. Thermal processes for methane production also are only economic at large scales and generate a mixture of gaseous products that must be upgraded to methane. The product gas is composed primarily of methane and carbon dioxide with traces of hydrogen sulphide and water vapour. The major limitation of biological gasification is that conversion is usually incomplete, often leaving as much as 50% of the organic matter unconverted.

 

Principles of anaerobic digestion

It is the application of biological methanogenesis, which is anaerobic process responsible for degradation of much of the carbonaceous matter in natural environment, where organic accumulation results in depletion of oxygen for aerobic metabolism. This process, which is carried out by a consortium of different organisms is found in numerous environments, including sediments, flooded soils and land fills.

 

In generalized scheme for anaerobic digestion feedstock is harvested, shredded and placed into a reactor which has an active inoculum of microorganisms required for methane fermentation. A conventional reactor is mixed, fed once or more per day, heated to a temperature of 350C and operated at a hydraulic retention time of 20 – 30 days and loading rate of 1.7 kg VS m3d-1. Under these conditions about 60% reduction in organic matter is achieved corresponding to a methane yield of 0.24 m3 per kg VS added. The biogas composition is typically 60% methane and 40% carbon dioxide with traces of hydrogen sulphide and water vapour. The conventional design is being replaced by more innovative designs influenced primarily by feed suspended solids content.

The objective of these designs is to increase solids and microorganism retention, decrease reactor size and reduce process energy requirements. Improved designs have increased possible loading rates 20 fold, reduced residence times and improved process stability.

  

Renewable methane from biomass

Resource potential estimates for terrestrial biomass is estimated to be 22 EJ while for feed stocks like grass, wood, seaweed it is 7 EJ.The potential for marine biomass is huge at greater than 100 EJ per year.

 

As biomethanogenesis decomposes organic matter with production of useful energy products, anaerobic digestion of organic matter is receiving increased attention. Solid and agricultural wastes release undesired methane into the atmosphere due to anaerobic digestion in landfills, lagoons or stockpiles. Treatment and recovery of this gas in reactors would reduce this source of atmospheric methane. An attractive option for treatment of the organic fraction of these wastes is to separately treat organic fraction by composting and applying the stabilized residues in land as a soil amendment. The residues would reduce water needs and prevent erosion.

 

As population increases and technology development begin to result in significant resource depletion and environmental deterioration, we must take a universal view on the ground rules for sustaining our species in a manner that is compatible with preservation of biosphere. This will require production of feed, food and energy by technologies that are indefinitely sustainable and which have minimal environmental impacts. This will involve a major shift to renewable resources of energy, sustainable agricultural practices for production of food, feed and energy and recycle of all non- renewable resources. Derivation of methane from energy crops and organic wastes has an important role towards achieving this objective.

BIOMASS AS ENERGY SOURCE -II

Another form of standardised fuel which is already being used in the rural areas is that of biogenous methane. The biological process of methane production results in a mixture of methane and carbon dioxide, which is called biogas. Burnt in a properly designed burner, biogas produces a blue flame, which is absolutely clean. This technology is at least 150 years old.

 

Traditionally, cattle dung is used as feedstock for producing biogas, and therefore it is also called gobar gas in India. During the last 50 years, the Government of India has made great efforts to popularise the gobar gas technology, but the present figures indicate that there are only about 2.5 million working domestic biogas plants in India, covering hardly 1.8% of the rural households. The failure of the gobar gas technology in India was due to the fact that it is not a very user-friendly technology. It requires dung from at least 6 to 8 heads of cattle. In order that the dung be easily available, the cattle must be penned and not allowed to roam.

 

The present technology also requires the dung to be mixed with equal volume of water to form a slurry. Villagers do not have tap water in their houses. Therefore, the water has to be fetched by the women from a source that is often far away from the house. The water is generally carried in pots balanced on their heads. Fetching water for the household is itself quite a strenuous task. Fetching daily additional 40 to 50 litres of water for the biogas plant only adds to the women’s burden, which they generally resent. The drudgery doesn’t just stop at fetching dung and water. Disposal of daily about 80 litres of spent slurry is also often a problem.

 

The new proposed system produced a more user-friendly biogas system based on starchy or sugary feedstock. Just 2 kg of sugar yield as much biogas as 40 kg of dung, and while dung requires a retention period of about 40 days, sugar yields the gas within just a single day. Starch also works equally well as feedstock. Our novel biogas system operates on waste starchy or sugary material such as leftover food, oilcake of non-edible oilseeds, fruits, tubers, rhizomes or grain that cannot be marketed due to poor quality, or non-edible material like rhizomes of banana, fruits of wild ficus etc.

 

A biogas plant based on this technology is quite small, having a capacity of just 1000 litres, and its cost is also much less, only about Rs.6000. About 200 of such gas plants are already installed, in various parts of Maharashtra, and this number is going to increase to 2000 in the next year.

 

Biogas can also be used as fuel in internal combustion engines. The CNG technology that is currently available in India can be used in both ways as bigas and an automotive fuel. Wood gas is the third alternative representing standardized fuel made from biomass. This technology does not lend itself well to being used in domestic cookstoves, but larger stoves, used in bakeries, langars or restaurants can be based on it.

However, wood gas is currently being used as fuel in internal combustion engines for generating electricity. Many such units are being operated all over the country. Biogas based electricity generation should be seriously considered by our planners and administrators as a means of supplying electricity to villages.

 

The electricity demand of a village is not very high. Supply of such small amount of electricity from a central generating facility is generally very costly because of the capital expense of the conduction system. There are also losses and theft of electricity when it is transmitted over such long distances. The village level generators should be operated by the villagers themselves. They can then generate electricity as and when they want and also use it for whatever purpose they want.

 

This discussion would not be completed without mentioning biodiesel and alcohol. Biodiesel is made from vegetable oil. In the Western countries, edible oil like soybean oil or rapeseed oil are used as a source of biodiesel. Our country, currently imports almost 50% of its total demand of edible oil. Under such circumstances, using edible oils for biodiesel is out of question.

 

Among our indigenous plant species, castor and rice are the only sources of oil that are produced by farmers. Castor oil, having special chemical composition, is not only being used by industries but it is also exported, while rice bran oil is used almost entirely by the organised soap industry. The remaining non-edible oils, being produced from seeds of various uncultivated tree species, play only a minor role in our economy. Being uncultivated, their supply is unreliable and therefore one cannot base a major industry like biodiesel on them. Currently India requires annually about 50 million tonnes of diesel. Substituing just 5% of this by biodiesel would require 2.5 million tonnes of vegetable oil. Considering average yield of 500 kg oil per hectare, one would require an area of 5 million hectares under oilseed production. I quote these figures only to bring into focus the magnitude of this endeavour. There is talk of introducing Jatropha curcas as a new oil bearing plant. It is claimed that  Jatropha requires very little water.

 

It is clear  that all plant species, irrespective of whether they are drought tolerant or not, require monthly about 200 mm water, if they are to give a good yield. Tolerance to drought means only that the plant can survive under conditions of drought and that it does not die under drought. It does not mean that it would give high yield under such conditions. It has been shown that even Jatropha needs about 800 to 900 mm of water to become economically viable. If a farmer has at his disposal this much water, he would rather grow a cash crop like cotton, groundnut, soybean or onion, than a low yielding plant like Jatropha.

 

The situation of alcohol is similar to that of biodiesel. Currently, alcohol is made from

molasses, a free by product of the sugar industry. As the cost of sugarcane, its harvest, transport, and processing are borne by sugar, the present cost of alcohol is low. But if crops like sugarcane, sugar beet or sweet sorghum are grown exclusively for alcohol production, the above mentioned costs would have to be borne by alcohol, which then would not be so cheap. Also the area required to be planted to produce alcohol would be of the same magnitude as that required by biodiesel.

 

Production of biomass in any form requires the use of land, and it would require the

involvement of rural people to do it. Chemical fertilizers, an important input required in agriculture, need a large quantities of fossil fuel in their production.

 

This concept is based on the assumption that soil micro-organisms degrade the soil minerals to provide the green plants with all the mineral nutrients that they need. If the soil micro-organisms are adequately fed with organic matter, there is theoretically no need to apply chemical fertilizers to the soil. Traditional agricultural scientists recommend the application of organic matter in the form of compost. However, the nutritional value of composted organic matter is so low, that one has to apply 20 to 50 tonnes of compost per hectare. In practical terms, it means that one has to use the biomass produced in about 10 hectares for providing organic matter to one hectare.

 

Research has shown that if organic matter having high nutritive value, like sugar, starch, protein etc. is used as manure, application of just 10 to 25 kg per hectare of it is enough to produce high crop yield without using any other form of chemical or organic nutrients. This new discovery would reduce the cost of agriculture substantially and would also reduce the cost of producing biomass.