Institute of hotel management & catering technology & applied nutrition Research project By
Bineet Merrie Jan 3rd year
Topic
Feasibility study on setting up of proper waste management system in the food and beverage industry.
Roll no.: 060685
IGNOU Roll no.:063206499
Year: 2008- 2009
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RESEARCH PROJECT A Feasibility study on setting up of proper waste management system in food and beverage industry. This is a bonafied record of work done by Bineet Merrie Jan, Roll No. 060685. Submitted in partial fulfillment of the requirement for the Final Year Bachelor in Hotel Management and Catering Technology 2008- 2009.
Faculty Guide Principal
Research Coordinator
SUBMITTED FOR THE VIVA VOICE EXAMINATION HELD ON ………………...
Internal External Examiner
Examiner
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RESEARCH PROJECT A Feasibility study on setting up of proper waste management system in food and beverage industry. This is a bonafied record of work done by Bineet Merrie Jan, Roll No. 060685. Submitted in partial fulfillment of the requirement for the Final Year Bachelor in Hotel Management and Catering Technology 2008- 2009.
Faculty Guide Principal
Research Coordinator
SUBMITTED FOR THE VIVA VOICE EXAMINATION HELD ON ………………...
Internal External Examiner
Examiner
3
AUTHENTICATION CERTIFICATE I Bineet Merrie Jan, Hereby declare that this project is my original work and that I have not submitted this report to any university or academic institute for the partial fulfillment of any course or degree or diploma as the case may be. Station: Chennai Student Signature Date: I certify that the above particulars are true and the project work has been done under my supervision. Station: Chennai Guide Signature Date:
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ACKNOWLEDGEMENT I Bineet Merrie Jan, would like to acknowledge my sincere thanks and gratitude to Mr. S Rajamohan, Principal IHM Chennai, for the support extended by him in completing this project.
I would also like to thank Mr. Jitendra Das, my project guide and also project coordinator Mr. Thriulogachandar, for all the assistance they offered, which enabled me to complete this project. I also thank them for the guidance they provided in finalizing project.
I cannot forget the valuable contributions the hospitality students, educator respondents, and recruiters, made to this project and I want to thank them for their informative responses.
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CONTENTS PROPOSAL FORMAT
06
DEFINING WASTE MANAGEMENT
09
WASTE MANAGEMENT CONCEPTS
10
WASTE DISPOSAL METHODS
12
HISTORY OF ANAEROBIC DECOMPOSITION
19
METHOD. BIOGAS PLANT FOR BIOLOGICAL WASTES RECYCLING WHAT ARE THE BENEFITS OF BIOGAS PLANT?
25 28
BIOGAS PRODUCTION PROCESS
31
BIOGAS PLANT SCHEME
46
CONCLUSION
55
BIBLIOGRAPHY
56
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PROPOSAL FORMAT NAME: Bineet merrie jan COURSE/ YEAR, BATCH: Bsc. H&ha 3rd year, ‘A’ batch. TITLE: Feasibility study on setting up of proper waste management system in the food and beverage industry.
INTRODUCTION Waste is an important by-product of the food and beverage industry. Also it poses a great threat to the environment in which we survive. Hence it is very much important to eradicate the various threats that are caused by the pollution. At this present century waste management is an important strategy that every industry is looking forward to. Through my research project I would like to bring out the various strategies that food and beverage industry has taken to do a proper waste management.
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OBJECTIVES •
To study about various waste management systems prevalent in the industry.
•
To study about the various waste products that our industry produce and its impact on the environment
•
To plan out a proper waste management system for the industry.
•
Providing information about use of biogas production technology in reducing the pollution.
METHODOLOGY •
Information through various books and newspapers.
•
Information from Internet.
•
Information from various personalities working in the industry.
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SCOPE OF STUDY •
This research project is carried out in order to bring out an awareness in the people regarding the need for proper waste management system that has to be installed in the food and beverage industry in order to reduce the environment pollution that it causes.
•
It also provides an outline about the strategies that the industry has to plan in order to have a self-sustainable growth.
SIGNATURE OF THE STUDENT.
GUIDE
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Defining Waste Management Waste minimization is a methodology used to achieve waste reduction, primarily through reduction at source, but also including recycling and re-use of materials, as shown in the figure below.
The benefits of waste minimization are both environmental and financial and wide in their coverage. Some of the main benefits include the following:
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•
Improved bottom line through improved process efficiency
•
Reduced burden on the environment, with improved public image and compliance with legislation
•
Better communication and involvement of employees and therefore greater commitment to the business
Waste management concepts There are a number of concepts about waste management, which vary in their usage between countries or regions. Some of the most general, widely used concepts include:
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Diagram of the waste hierarchy. •
Waste hierarchy - The waste hierarchy refers to the "3 Rs" reduce, reuse and recycle, which classify waste management strategies according to their desirability in terms of waste minimization. The waste hierarchy remains the cornerstone of most waste minimization strategies. The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste.
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•
Extended producer responsibility - Extended Producer Responsibility (EPR) is a strategy designed to promote the integration of all costs associated with products throughout their life cycle (including end-of-life disposal costs) into the market price of the product. Extended producer responsibility is meant to impose accountability over the entire lifecycle of products and packaging introduced to the market. This means that firms which manufacture, import and/or sell products are required to be responsible for the products after their useful life as well as during manufacture.
•
Polluter pays principle - the Polluter Pays Principle is a principle where the polluting party pays for the impact caused to the environment. With respect to waste management, this generally refers to the requirement for a waste generator to pay for appropriate disposal of the waste.
Waste Disposal Methods
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Source reduction Volume of solid waste is reduced by reducing packaging, disposable products, etc. Could introduce advanced practices, reducing waste at source. Many sources lie outside individual cities.
Uncontrolled dumping Controlled application of waste on land. Low-cost and low technology solution when land available. Risks in certain circumstances, e.g., to water supply.
Sanitary land filling Controlled application of waste on land. Low-cost and low technology solution when land available. Risks in certain circumstances, e.g., to water supply.
Composting 14
Biological decomposition of organic matter in waste under controlled conditions. Needs correct proportion of biodegradable material in waste. May be expensive where no market for compost. Large decentralized schemes claimed to be unsuccessful.
Multi-material recycling Complements
composting
Design
products
for
ready
recycling/reuse, sorting by consumers and pick-up by types of materials. Recycling and reuse already occurs in many countries as a matter of economic necessity.
Incineration Controlled burning of waste at high temperatures to reduce its volume; possibility to gain energy from combustion.
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High capital cost; requires skilled operation and control. Waste must have high calorific value. Advantage if land not available for landfill.
Gasification Biological decomposition of organic matter in waste under controlled conditions to obtain methane and other gases. High cost and technologically complicated.
Refuse derived fuel Separation of combustible materials from solid waste to be used for fuel purposes. Assumes combustible material not separated out. Costs and operational issues not widely known for large-scale operations.
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Pyrolysis High temperature conversion of organic material in absence of oxygen to obtain combustible by-products. Capital intensive with high running costs, and technically complex.
Advantages and Disadvantages OCEAN DUMPING Advantages: •
Convenient 17
•
Inexpensive
•
Source of nutrients, shelter and breeding Disadvantages:
•
Ocean overburdened
•
Destruction of food sources
•
Killing of plankton
•
Desalination
SANITARY LANDFILL Advantages: •
Volume can increase with little addition of people/equipment
•
Filled land can be reused for other community purposes Disadvantages:
•
Completed landfill areas can settle and requires maintenance
•
Requires proper planning, design, and operation
INCINERATION 18
Advantages: •
Requires minimum land
•
Can be operated in any weather
•
Produces stable odor-free residue
•
Refuse volume is reduced by half Disadvantages:
•
Expensive to build and operate
•
High energy requirement
•
Requires skilled personnel and continuous maintenance
•
Unsightly - smell, waste, vermin
OPEN DUMPING Advantages: •
Inexpensive Disadvantages:
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•
Health-hazard - insects, rodents etc.
•
Damage due to air pollution
•
Ground water and run-off pollution
RECYCLING Advantages: •
Key to providing a livable environment for the future Disadvantages:
•
Expensive
•
Some wastes cannot be recycled
•
Technological push needed
•
Separation of useful material from waste difficult
History of anaerobic decomposition method. Scientific interest in the gasses produced by the natural decomposition of organic matter, was first reported in the seventeenth century by Robert Boyle and Stephen Hale, who noted
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that flammable gas was released by disturbing the sediment of streams and lakes. In 1808, Sir Humphry Davy determined that methane was present in the gasses produced by cattle manure. The first anaerobic digester was built by a leper colony in Bombay, India in 1859. In 1895 the technology was developed in Exeter, England, where a septic tank was used to generate gas for street lighting. Also in England, in 1904, the first dual purpose tank for both sedimentation and sludge treatment was installed in Hampton. In 1907, in Germany, a patent was issued for the Imhoff tank, an early form of digester. Through scientific research anaerobic digestion gained academic recognition in the 1930s. This research led to the discovery of anaerobic bacteria, the microorganisms that facilitate the process. Further research was carried out to investigate the conditions under which methanogenic bacteria were able to grow and reproduce. This work was developed during World War II where in both
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Germany and France there was an increase in the application of anaerobic digestion for the treatment of manure.
Applications Anaerobic digestion is particularly suited to wet organic material and is commonly used for effluent and sewage treatment. Anaerobic digestion is a simple process that can greatly reduce the amount of organic matter, which might otherwise be destined to be land filled or burnt in an incinerator. Almost any organic material can be processed with anaerobic digestion. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. The exception to this is woody wastes that are largely unaffected by digestion as most anaerobes are unable to degrade lignin. The exception being xylophalgeous anaerobes (lignin consumers), as used in the process for organic breakdown of 22
cellulosic material by a cellulosic ethanol start-up company in the U.S. Anaerobic digesters can also be fed with specially grown energy crops such as silage for dedicated biogas production. In Germany and continental Europe these facilities are referred to as biogas plants. A co-digestion or co-fermentation plant is typically an agricultural anaerobic digester that accepts two or more input materials for simultaneous digestion. In developing countries simple home and farm-based anaerobic digestion systems offer the potential for cheap, low-cost energy for cooking
and
lighting.
The
United
Nations
Development
Programme has recognized anaerobic digestion facilities as one of the most useful decentralized sources of energy supply. From 1975, China and India have both had large government-backed schemes for adaptation of small biogas plants for use in the household for cooking and lighting. Presently, projects for anaerobic digestion in the developing world can gain financial support through the United
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Nations Clean Development Mechanism if they are able to show they provide reduced carbon emissions. Pressure from environmentally related legislation on solid waste disposal methods in developed countries has increased the application of anaerobic digestion as a process for reducing waste volumes and generating useful by-products. Anaerobic digestion may either be used to process the source separated fraction of municipal waste, or alternatively combined with mechanical sorting systems, to process residual mixed municipal waste. These facilities are called mechanical biological treatment plants. Utilizing anaerobic digestion technologies can help to reduce the emission of greenhouse gasses in a number of key ways:
•
Replacement of fossil fuels
•
Reducing methane emission from landfills
•
Displacing industrially-produced chemical fertilizers
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•
Reducing vehicle movements
•
Reducing electrical grid transportation losses
Methane and power produced in anaerobic digestion facilities can be utilized to replace energy derived from fossil fuels, and hence reduce emissions of greenhouse gasses. This is due to the fact that the carbon in biodegradable material is part of a carbon cycle. The carbon released into the atmosphere from the combustion of biogas has been removed by plants in order for them to grow in the recent past. This can have occurred within the last decade, but more typically within the last growing season. If the plants are re-grown, taking the carbon out of the atmosphere once more, the system will be carbon neutral. This contrasts to carbon in fossil fuels that has been sequestered in the earth for many millions of years, the combustion of which increases the overall levels of carbon dioxide in the atmosphere. If the putrescible waste processed in anaerobic digesters were disposed of in a landfill, it would break down naturally and often 25
anaerobically. In this case the gas will eventually escape into the atmosphere. As methane is about twenty times more potent as a greenhouse gas as carbon dioxide this has significant negative environmental effects. Digestate liquor can be used as a fertilizer supplying vital nutrients to soils. The solid, fibrous component of digestate can be used as a soil conditioner. The liquor can be used as a substitute for chemical fertilizers, which require large amounts of energy to produce. The use of manufactured fertilizers is therefore more carbon intensive than the use of anaerobic digestate fertilizer. This solid digestate can be used to boost the organic content of soils. There are some countries, such as Spain where there are many organically depleted soils, and here the markets for the digestate can be just as important as the biogas. In countries that collect household waste, the utilization of local anaerobic digestion facilities can help to reduce the amount of waste that requires transportation to centralized landfill sites or 26
incineration facilities. This reduced burden on transportation has and will reduce carbon emissions from the collection vehicles. If localized anaerobic digestion facilities are embedded within an electrical distribution network, they can help reduce the electrical losses that are associated with transporting electricity over a national grid.
Biogas plant for biological wastes recycling What is biogas plant? Biogas plant produces biogas and bio-fertilizer from biological wastes of agricultural and food industries by means of oxygen-free fermentation (anaerobic digestion). Biogas plant – is the most active system of biological recycling. This system performs utilization, recycling and has shortest payback period. The differences from the other recycling systems are the following.
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1) biogas plant does not consumes power, but produces it 2) produced electricity is used by the enterprise and end products of other recycling systems (dry feed or dry manure) needs to be sold or recycled.
Following raw materials can be used for biogas production:
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Cattle manure, pig manure, chicken dung, slaughterhouse waste (blood, fat, entrails, and rumen content), plants waste, silage, rotten grain, waste water, fats, bio-waste, food industry waste, malt remnants, marc, distillery slop, bioethanol plant slop, brewer’s grain (crushed malt remnants after wort filtration), sugar beet and fruit pulp, sugar beet tops, technical glycerin (after biodisel production), fiber and other starch and treacle production, milk whey, flotation sludge, dewatered flotation sludge from municipal waste water treatment plants, algae. Most of the raw materials can be mixed with each other.
What are the benefits of biogas plant? Waste recycling gives:
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Main benefits 1. Ecological cleaning 2. Gas, 3. Bio-fertilizer, 4. Investment cost saving (for new enterprises)
Additional benefits 1. Electricity, 2. Heat,
\
Ecological cleaning and utilization Biogas plant can reduce sanitary zone (distance from the enterprise to residential area) from 500m to 150m. In many cases such ecological issues are vital for some enterprises. 30
Out-of-date lagoons occupy lots of space and have bad smell. Biogas plant requires space that several times less if to be compared to lagoons and manure storages. Water in lagoons is bounded by colloid compounds hence evaporation is very faint. After treatment in biogas plant water is separated and easily vaporized. Digested biomass can be released to the fields without any time delays, which can reduce lagoons area up to 5 times! Investments into lagoon construction are money thrown down the drain. By investing into biogas plant you payback your money with profit and make land usage more effective. Biogas plant construction is useful not only for new farms but for existing as well, because old lagoons maintenance cost are considerable. Some of waste products can be stored in lagoons while the other requires energy and cost consuming utilization (slaughterhouse waste), biogas production looks more attractive in that respect. Usage of conventional lagoons and land fills often makes possible filtrate percolation to the groundwater that causes health problems
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to people and animals as well as sanctions from state sanitary service and costly medical treatment. Using biogas plant system you will avoid diseases, medical and penalty bills. Equipped with additional filtration devices (pressure filter, decanter) biogas plant can reduce COD and BOD levels in filtrate so it can be discharged to sewage system or factory water treatment facility. COD – chemical oxygen demand and BOD – biological oxygen demand. Biogas plant makes possible removal of most part of contaminating biological matter (organic matter content reduced up to 60-70%).
Biogas production process
Four steps of fermentation
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Scheme 1. Metabolism products of the anaerobic fermentation Bacteria decompose the organic matter in anaerobic environment. Biogas
is
an
intermediate
product
of
their
metabolism.
The decomposition process can be divided into 4 steps (see scheme 1) each of those accompanied by different bacteria groups: In the first stage aerobic bacteria reconstructs high-molecular substances (protein, carbohydrates, fats, cellulose) by means of enzymes to low-molecular compounds like monosaccharide, amino acids, fatty acids and water. Enzymes assigned by hydrolysis bacteria decompose substrate components to small water-soluble molecules.
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Polymers turn into monomers (separate molecules). This process called hydrolysis. Then acid-forming bacteria make decomposition. Separate molecules penetrate into bacteria cells where further transformation takes place. This process is partially accompanied by anaerobic bacteria that consume rest of oxygen hence providing suitable anaerobic environment for methane bacteria. This step produces: •
Acids (acetic acid, formic acid, butyric acid, propionic acid, caproic acid, lactic acid),
•
Alcohols and ketones (methanol, ethanol, propanol, butanol, glycerin and acetone),
•
Gases (carbon dioxide, carbon, hydrogen sulfide and ammonia). The step is called oxidation.
Afterwards acid-forming bacteria form initial products for methane
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formation: acetic acid, carbon dioxide and hydrogen). These products are formed from organic acids. For vital functions of these bacteria that consume hydrogen, stable temperature mode is very important. The last step is methane, carbon dioxide and water formation. 90% of methane yield takes place at this stage, 70% from acetic acid. Thus acetic acid formation (3rd step) is the factor that defines the speed of methane formation.
One and two stages process
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Scheme 2. One and two stages methane production process.
In most cases such processes take place simultaneously it means that there is no boundaries for place and duration of decomposition. Such technology is called two stages technology. For fermentation of rapidly decomposable raw materials in pure state two stage technology required. For example chicken dung, distillery slop shouldn’t be recycled in one digester. In order to process those substrates hydrolysis reactor is needed. Such reactor allows control over the acidity and alkalinity level in order to avoid bacteria collapse and increase methane yield. (Scheme 2.)
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For successful lifecycle of all microorganisms inside the digester special conditions must be secured. Mandatory factors for that are the following: Anaerobic environment - active functioning of bacteria is possible only
in
oxygen-free
conditions.
Biogas plant design takes that into consideration. Humidity - bacteria can live, feed and propagate only in moist conditions. Temperature - the optimum temperature for mode for all bacteria groups is 35-40о С range. Human is not able to control this, that is why it is done by automatic control system. Fermentation period - The quantity of produced biogas is different within the fermentation period. In the beginning of fermentation it is more intensive then at the en of it. Then comes the moment when further biomass presence in the digester is economically unfeasible. Our specialists rest upon long-term experience while calculating 37
fermentation period efficiency.
рН level - hydrolysis and oxidation bacteria can live in acid environment with pH level 4.5-6.3 while methane and acetic acid formation bacteria can exist only in low alkalinity environment with pH 6.8-8. All the bacteria kinds have tendency to suspend their activity in case pH level is higher of the optimum hence the biogas production suspends as well. That is why the best pH level 7 should be maintained. Even substrate feed - the by-products of each group of bacteria lifecycle are the nutrients for other bacteria group. The all work with different speed. The bacteria should not be overfeed as they hardly be able to produce nutrients for another group. That is why the substrate feed is calculated and programmed for each project carefully. Nutrients supply - bacteria provided with all necessary nutrients that are contained in substrate so the only thing is needed is constant
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substrate supply. Substrate contains vitamins, soluble ammonia compounds, microelements and heavy metals in small quantities. Nickel, cobalt, molybdenum, wolfram and ferrum are required by bacteria for enzyme formation and are also present in substrates. Particle size - The smaller the better rule is working here. Bacteria size 1/1000 mm the smaller the substrate particles the easier the decomposition made by bacteria. Fermentation period becomes shorter and biogas production faster. If necessary additional substrate disintegration should be done before substrate feed into reactor. Mixing - is important not only to avoid floating cork and sediment formation but also for biogas extraction (mixers help bubbles to go up the digester). Mixers work constantly in a bacteria preserving mode. Process stability - microorganisms are used to certain feed other modes. Any changes should be done smoothly. Avoid getting into reactor antibiotics, chemical and disinfection 39
means, big quantities of heavy metals. Our specialists can advice you on that. The end product of biological treatment are: •
biogas (methane not less then 55%, carbon dioxide not more then 45%, hydrogen sulfide not more then 2%, hydrogen not more then 1%);
•
fermented substrate as fermentation residue, consisting of water, cellulose residues, small quantity of bacteria and organic nutrients (nitrogen, phosphorus, potassium etc.).
Biogas What is biogas? Biogas is the gas consisting of approximately 50-70% of methane (CH4) and 50-30% of carbon dioxide (CO2). Synonyms for biogas such words as sewage gas, marsh gas, methane. Different microorganisms metabolizing carbon from organic matter in oxygen-free environment (anaerobically). This process is known as 40
decomposition or anoxic fermentation and follows food chain. In the process of fermentation biological waste produces biogas. This gas can be used as natural gas for technological purposes, heating or electricity production. It can be stored, pumped, used as vehicle fuel or sold to your neighbors. In order to produce electricity no additional treatment of biogas is required. By properties biogas is similar to natural gas. In case adjustable burner is used biogas needs only drying, hydrogen sulfide and ammonia removal. If the burner is not adjustable the system of carbon dioxide removal will be needed. For vehicle refueling additional gas treatment system should be used. After such treatment biogas becomes pure natural gas analog (90-97% of methane (CH4) and 10-3% of carbon dioxide (CO2)). Another by-product of biogas treatment is CO2. This gas used as dry ice, for beverages production or technological purposes and can be sold as valuable commodity.
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Biogas yield m3/t of raw Raw material Cow manure Pig manure Chicken dung Fat Distillery slop Grain Silage, plant
material 60 65 130 1300 70 500-560 tops, 400
grass, algae Milk whey 50 Fruit and sugar beet 50-70 pulp Technical glycerin 500 Brewer’s grains 180 Anyone understands that natural gas price increase is inevitable and substantial. Gas pipeline broaching worth millions of dollars, contrarily biogas plants construction is more cost effective. After investment into gas pipeline we have to pay for gas as well, to be compared with biogas it is nearly costless (less then 30 123 per 1000 m3). Biogas plant is the best solution for gas supply to remote regions. 42
Bio-fertilizer Raw manure or other biological waste is not applicable as fertilizer for 3-5 years. Anaerobically digested biomass is a finished and ready for use high-performance bio-fertilizer. This is not only ecological issue, but the matter of profit. In raw biological waste (manure for example) minerals are chemically bounded to organics that complicates their consumption by plants. For example mineralization in raw manure is 40% if to be compared to 60% in digested biomass. Digested biomass is finished solid and liquid bio-fertilizer free of nitrites, weed seeds, pathogenic microflora, helminth eggs and odors. As a result of balanced bio-fertilizer application crop yield can be increased up to 30-50%. Biogas plant produces high quality bio-fertilizer. Bio-fertilizer is a commodity. The quality of bio-fertilizer is higher then mineral fertilizers and the net cost almost equals to “0”. As a commodity it can be sold to anyone.
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Investment savings New enterprises can have considerable investment savings due to the possibility to avoid building new gas pipeline, electricity line, auxiliary generators and waste storage facilities. Thanks to the short digestion period the volume of waste lagoons can be reduced twice. Investment cost savings can reach about 30-40% from biogas plant price. Electricity Combustion of 1 m3 produces 2 kWh of electricity. You get fluctuation free electricity in comparison with public electricity network. By building biogas plant you will have electricity at a fixed price, that makes about 0.01$/kWh. Heat Heat from generator cooling or biogas combustion is used for working
premises
heating,
technological
purposes,
steam
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generation, seeds drying, firewood drying, hot water supply and stock keeping. New or existing greenhouse nearby biogas plant is a perfect solution. Heat can come directly from biogas combustion or from generator cooling device. Only generator cooling device can heat 2 Ha of greenhouse area. 90% of expenses for growing greenhouse cucumbers, tomatoes and flowers are heat and fertilizer costs. If greenhouse combined with biogas plant it is possible to reach 300500% of profitability. Heat is also used to activate refrigerator vaporizer and produce cold for refrigeration of fresh milk at dairy farms or meat and eggs storage. Vehicle fuel After treatment of biogas you get biomethane (90-95% methane, the rest is CO2). Biomethane is complete analog of natural gas by
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its properties and quality. The only difference is the source of the gas. Such methane can be and should be filled into vehicle tank. Huge gas filling station network already exists. In the circumstances of constant diesel fuel rice in price, methane usage becomes more attractive. Biogas plants equipped with biogas treatment system and methane filling station. Also we can undertake conversion of engines to run on methane. Conversion of one system unit to run on methane costs 2200 123, all materials and work included. Methane filling station payback period is about half a year. Net cost of biomethane is 1200 Rs for 1000 m3, and price for diesel fuel 50000 Rs for 1000 L. 1 L of diesel fuel equals 1 m3 of biomethane.
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Biogas plant scheme
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Operation principle of biogas plant Liquid biological waste is pumped to biogas plant by sanitary pump or extraction pipeline. Sewage pumping station (SPS) is located in a separate service room. Solid biological waste (manure, dung) delivered by belt conveyor, in case of manure or dung storage, delivery made by tractor. Liquid wastes initially come to primary tank. In primary tank waste homogenized and heated
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(sometimes cooled) for required temperature. As a rule such tank has 2-3 days storage capacity. Solid waste can be loaded to that tank as well for homogenization or get into digester through screw charger. From homogenization tank and screw charger biomass (manure, dung or distillery slop) comes to digester (biological reactor). Biological reactor is gas-proof tank made of acid-resistant concrete. Reactor is heat-insulated. The heat-insulation is calculated depending on the biogas plant site climate conditions. For microorganisms’ vital activity a constant and even temperature inside the digester is kept, usually it is mesophilic temperature mode (+30-41°С). In some cases termophilic mode of temperature is used (about 55°С). Biomass mixing inside the digester is made by several ways and depends on the type of raw material, its humidity and other features. Mixing can be done by slopped mixer, “paddle giant” type mixer or submersed mixers. Al mixer types are made of stainless steel. In some cases mixing device can be
49
hydraulic instead of mechanical. Such mixers pump the biomass into the layers with bacterial clumps. Bioreactors are built with wooden or concrete dome and have service life of 25-30 years. Digesters are heated by hot water with inlet temperature about 60°С and discharge temperature of about 40°С. Heating system is a network of pipes, which can be built-in to reactor wall or to be mounted to interior side of the digester wall. In case biogas plant equipped with co-generation unit, digester can be heated by generator cooling water. Generator cooling water has temperature of 90°С and before getting into digester heating system it is mixed with 40°С water so that heating system receives water with 60°С. The water is previously treated and returnable. In winter time biogas plant requires up to 70% of heat from generator cooling device and 10% in summer time. If biogas plant is purposed only for gas production hot water is taken from a special water boiler. Biogas plant self energy and heat consumption usually makes from 5% to 15% of overall produced.
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The average hydraulic retention time of biomass in bioreactor (depending on the material type) is 20-40 days. During this time organic matter is metabolized (modified) by microorganisms presented in the biomass. Corn silage hydraulic retention time is about 70-160 days. The hydraulic retention time defines the size of the digester. The fermentation process is made by anaerobic microorganisms, which are injected into the digester during the biogas plant start up. Any
further
microorganisms
injection
is
not
required.
Microorganisms injection is made by one of three ways: 1) microorganisms concentrate injection 2) fresh manure addition or 3) injection of biomass from operational biogas plant. As a rule 2nd
and
3rd
methods
are
used
being
cheapest
ones.
Microorganisms get into manure from animal bowels and are not harmful to human or animal. Moreover bioreactor is a hermetically sealed container. That is why bioreactors or fermenters can be placed near the farm or production facilities.
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As end products we have: biogas and bio-fertilizer (composted or liquid). Biogas is stored at a gasholder. Inside the gasholder pressure and biogas composition is evened. Gasholder is a high-tensile and distensible EPDM membrane. The membrane material is resistant to sunlight and internal bioreactor sediments and evaporations. Gasholder service lifetime is 15 years. Bioreactor hermetically sealed by the gasholder from the topside and covered by additional tilt cover. The space between the gasholder and tilt cover is pumped with an air in order to form pressure and heat insulation. Sometimes gasholder is a multichamber cover. Depending on the project solution such cover can be secured by belts on the top of the concrete dome or to be placed in a separate concrete tank. Gasholder volume capacity is 0.5 – 1 operational day. From the gasholder biogas constantly comes to gas or diesel/gas co-generation unit. Here heat and electricity are being produced. 1m3 of biogas produces 2 kWh of electrical and 2 kWh of heat 52
power. Big biogas plants are equipped with an emergency flare for instances of engines malfunction and the necessity to burn the excessive biogas. Biogas system can be equipped with ventilation, condensate extractor and desulphurization unit. The automatic control unit operates the whole system. Control unit operates the work of pumping station, mixers, heating system, gas automatics and generator. For operational control only one person for 2 hours a day is required. This person affects the control with the help of computer. After two weeks of training any person without any special skills can operate the biogas plant. Anaerobically digested biomass is finished and ready for use as fertilizer. Liquid bio-fertilizer is separated by separation unit and stored in a tank. In Germany this liquid (ammonia water) is used as a fertilizer due to high ammonia (NH4) content. Solid fertilizer is stored separately. From the storage tank liquid bio-fertilizer is pumped to transportation tanks for further distribution or sale. As an option biogas plant can be supplied with fertilizer packing line 53
(bottles 0.3, 0.5, 1.0 l). In case liquid fertilizer is of no interest for biogas plant owner, such plant can be equipped with additional wastewater treatment modules. When company doesn’t need electricity but gas for vehicle filling, biogas plant supplied with gas treatment system and methane filling station. Gas treatment system is equipment that separates carbon dioxide from biogas and is based on absorption and stripper technology. Carbon dioxide content can be reduced from 40% up to 10% (even 1% is possible if required). This option is very interesting taking into consideration diesel fuel high prices. For some types of biological waste above mentioned operation principle requires modification. For example it is not workable with single raw materials such as distillery slop and brewer’s grain. In that instance two stage systems with additional hydrolysis reactor should be used. The peculiarity of the process is the support of acidity level in hydrolysis reactors. This technology patented by
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123 and is under protection that makes impossible it’s usage by other companies. Biogas plant self energy consumption is 10-15% in wintertime and 3-7% in summer time. In order to operate even big biogas plant only one person for two hours a day required. Biogas plant equipment and facilities 1. Homogenization tank 2. Solid biomass loader 3. Bioreactor (digester) 4. Mixing devices 5. Gasholder (gas storage) 6. Water mixing and heating system 7. Gas system 8. Pumping station 9. Separator 10. Control gauges
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11. Control equipment with visualization 12. Emergency flare system and security system
CONCLUSION Thus it can be concluded that waste management is an important part in outlining the developmental strategies
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of every industry especially in the food and beverage industry. Now a days since the environmental laws are really strict it becomes the need of the hour to plan and execute the various waste management programmes that are necessary for the industry.
BIBLIOGRAPHY •
The Hindu Daily.
•
Hotel and Hospitality Magazines
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•
Wikipedia.org
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Gdrc.org
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Zorg-biogas.com
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Wm.com
•
Auroville.com
•
Ficci.com BOOKS •
Journal of industrial Ecology, S. Nakamura. 2002.
•
International
Journal
Of
Contemporary
Hospitality Management, D. Krik- 1995 •
Waste Management And Reserch,Y. S Wang-1997
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