CITY & SOLID WASTE PROBLEM

as a business man everybody including MNCs like thermax is installing incinarators.new technologies are coming up in USA for transforming heat into electricity (HEAT MACHINES).India is better off than other countries in recycle and reuse of solid waste. but a total failure in reducing the quantity of solid waste generated. who is to blame? and 90 % of indian population still lives in villages where there is no problem of solid waste.it s a city phenomenon.

Refuse-Derived Fuel Processing

Waste to Energy Facilities
Solid Waste Incinerators, Refuse-Derived Fuel Processing and Solid Waste Pyrolysis Units


http://www.dec.state.ny.us/website/dshm/sldwaste/facilities/wte.htm

methane gas generation in bio gas plant

Methane Generation From Livestock Wastes

by R.W. Hansen ¹

Quick Facts... Anaerobic fermentation or digestion is the most promising process for converting organic materials to methane and other gases. A simple apparatus can be constructed to produce bio-gas. Bio-gas usually contains about 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and other gases. The heat value of raw bio-gas is approximately half that of natural gas under typical Colorado conditions. Take precautions when processing and handling the gas. It is highly explosive and difficult to detect. Energy conservation, coupled with concern for the management of livestock wastes, has revived an interest in generating methane from livestock manures. Converting organic materials, such as animal wastes, to an easily used form of energy can be accomplished by several methods. The process with the greatest potential is anaerobic fermentation or digestion. The extraction of energy from wastes using anaerobic digestion to produce bio-gas is not new and the general technology is well known. Bio-gas, which is methane and other gases, has been known as swamp gas, sewer gas and fuel gas. Sewage treatment plants generate bio-gas from the sewage sludge as part of the sewage treatment processes. Many small units were used in Europe and India after World War II. Characteristics of Bio-Gas Bio-gas usually contains about 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and other gases, including ammonia, hydrogen sulfide, mercaptans and other noxious gases. It also is saturated with water vapor. The heat value of the raw gas at typical Colorado atmospheric pressures is about 400 to 600 British thermal units (Btu) per cubic foot. In comparison, natural gas has a heat value of 850 Btu per cubic foot and gasoline contains approximately 120,000 Btu per gallon. Partial removal of the impurities may be required. This is not necessarily difficult, but it does complicate the system. Basic Digester Process Methane is produced by bacteria. The bacteria are anaerobes and operate only in anaerobic environments (no free oxygen). Constant temperature, pH and fresh organic matter promote maximum methane production. Temperatures usually are maintained at approximately 95 degrees F. Other temperatures can be used if held constant. For each 20 degrees F decrease, gas production will be cut approximately one half or will take twice as long. A constant temperature is critical. Temperature variations of as little as 5 degrees F can inhibit the methane-formers enough to cause acid accumulation and possible digester failure. Anaerobic digestion is a two-part process and each part is performed by a specific group of organisms. The first part is the breakdown of complex organic matter (manure) into simple organic compounds by acid-forming bacteria. The second group of microorganisms, the methane-formers, break down the acids into methane and carbon dioxide. In a properly functioning digester, the two groups of bacteria must balance so that the methane-formers use just the acids produced by the acid-formers. A simple apparatus can produce bio-gas. The amount of the gas and the reliability desired have a great influence on the cost and complexity of the system. A simple batch-loaded digester requires an oxygen-free container, relatively constant temperature, a means of collecting gas, and some mixing. Because methane gas is explosive, appropriate safety precautions are needed. Tank size is controlled by the number, size and type of animals served, dilution water added, and detention time. The factor that can be most easily changed with regard to tank size is detention time. Ten days is the minimum, but a longer period can be used. The longer the detention time, the larger the tank must be. Longer detention times allow more complete decomposition of the wastes. Fifteen days is a frequently used detention time. Table 1 shows some recommended sizes, dilution ratios and loading rates for different types of animals. Little volume reduction occurs in an anaerobic digester. Waste fed into the digester will be more than 90 to 95 percent water. The only part that can be reduced is a portion of the solids (about 50 to 60 percent). The processed material will have less odor. Because it still contains most of the original nitrogen, phosphorus and potassium, and is still highly polluted, the waste cannot enter a stream after it leaves the digester. Lagoons are commonly used to hold the waste until it can be disposed of by either hauling or pumping onto agricultural land. Table 1: Loading rate guidelines for heated, mixed anaerobic digesters at 95 degrees F being fed fresh livestock manures.* Factor Swine (growing-finishing) Dairy Beef under 700 lbs Poultry layer Poultry broiler Dilution ratio manure (manure to water) 1:2.9 Undiluted 1:2.5 1:8.3 1:10.2 Estimated dilution water (gal water/1,000 lbs body wgt)** 15 0 11 47 79 Hydraulic detention time (days) 12.5 17.5 12.5 10 10 Loading rate (lbs volatile solids/cubic foot/day)** 0.14 0.37 0.37 0.13 0.1 Digester volume (cubic feet/1,000 lbs animal wgt)** 30 24 14 72 120 *(From R.J. Smith, The Anaerobic Digestion of Livestock Wastes and the Prospects for Methane Production, Midwest Livestock Waste Management Conference, ISU, Ames, Iowa, Nov. 27-29, 1973) **To convert to metrics use the following equivalents: 1 gal = 3.8 l; 1 lb = .45 kg; 1 cu ft = .03 cu m. The volume of effluent actually may be greater than the volume of manure prior to digestion. This increase is due to the dilution water added to liquefy the manure to the desired solid content for the digester. There is no increase in the amount of nitrogen, phosphorus or potassium in this material, although it may be in a more available form. A small portion of the nitrogen may be lost to the gas portion of the system, thus reducing the amount of nitrogen initially available. Gas Production Total bio-gas production varies depending on the organic material digested, the digester loading rate, and the environmental conditions in the digester. Under ideal conditions (95 degrees F temperature and proper pH), it is possible to produce about 45 cubic feet of gas at atmospheric pressure from one day's manure from a 1,000 pound cow. Not all of the bio-gas energy is available for use. Energy is required to heat and mix the digester, pump the effluent, and perhaps compress the gas. Table 2 summarizes the estimated gas production from various animal wastes. Table 2: Bio-gas production (60% methane and 40% carbon dioxide) from animal wastes per 1,000 pounds body weight. Animal Volatile solids (lb per animal per day) Probable volatile solids destruction (percent)1 Gas (cu ft per day) Btu (per day)2 Beef 5.9 45 30 18,000 Dairy 8.6 48 44 26,000 Poultry, layers 9.4 60 72 43,000 Poultry, broilers 12.0 60 92 55,000 Swine (growing-finishing) 4.8 50 29 17,400 1Percent destruction of volatile solids varies depending primarily on detention time and digester temperature. 2Calculated at 600 Btu/ft3* (heat content varies depending on quality of gas). For comparison, some other heating values are: gasoline, 124,000 Btu/gal; diesel fuel, 133,000 Btu/gal; natural gas, 850 to 1,000 Btu/ft3; propane, 92,000 Btu/gal. *To convert to metrics, use the following equivalents: 1 lb = .45 kg; 1 cu ft = .03 cu m; 1 gal = 3.8 1. Basic Elements Figure 1 shows the basic elements of a single-stage anaerobic digester. Submerged inflow and outflow lines are needed to prevent gas from escaping. Either a mechanical mixer can be used, or the liquid or gas can be recirculated for mixing. A heat exchanger and thermostat maintain the proper temperature. The heat exchanger can be either internal or external. Methane is drawn off the top of the digester. For gas utilization, a compressor and storage tank are used, along with the hardware to provide flame traps, regulators, pressure gauges, hydrogen sulfide scrubber, carbon dioxide removal and pressure relief valves. A common facility for gas storage is the floating cover that floats upward while maintaining essentially constant pressure. Methane or bio-gas cannot be converted to a liquid under normal temperatures as can LP gas (LP gas liquefies at 160 psi). Under constant temperature, volume reduction is inversely proportional to the pressure; that is, as the pressure doubles, the volume becomes half as large. The more the gas is compressed, the more energy it takes to compress it. Figure 1: Basic components of anaerobic digester. Liquefaction of methane requires pressures of nearly 5,000 psi and is not practical. If the gas is compressed to just 1,000 psi, it requires about 1,320 Btu of energy to put 6,350 Btu into a storage container. Because bio-gas cannot be liquefied, it is best suited for stationary uses, such as cooking, heating water and buildings, air conditioning, grain drying, or operating stationary engines. It is not feasible as a tractor fuel. One cubic foot of compressed bio-gas at 3,000 psi would run a 100-horsepower tractor approximately 7 1/2 minutes. Most tractor fuel tanks occupy about 8 cubic feet. A special high-pressure tank with 8 cubic feet of gas and 3,000 psi would run the tractor approximately one hour. A 3,000-psi tank bouncing around on a tractor would present a serious safety hazard. The tractor would run 6 minutes on 8 cubic feet of gas compressed to 300 psi, a more realistic pressure. A well-insulated, three-bedroom home takes about 900,000 Btu per day for heating during cold weather. Because 50 percent of the bio-gas goes back into maintaining the necessary temperature of the digester, it would take the manure from 50 cows to produce enough bio-gas each day for home heating. Bio-gas is produced on a relatively constant basis. Most applications are somewhat intermittent; therefore, storage is required. The amount of storage depends on the storage time and pressure. High demand applications, such as grain drying, normally are impractical due to the excessive storage capacity required. Hazards Methane in a concentration of 6 to 15 percent with air is an explosive mixture. Since it is lighter than air, it will collect in rooftops and other enclosed areas. It is relatively odorless and detection may be difficult. Extreme caution and special safety features are necessary in the digester design and storage tank, especially if the gas is compressed. Summary Concerns for energy conservation, environmental pollution, and the fact that agricultural organic wastes account for a major portion of our waste materials, has created renewed interest in the processing of these wastes for energy recovery. Of the several types of energy capturing processes available, anaerobic digestion appears to be the most feasible for the majority of agricultural operations. Anaerobic digestion can stabilize most agricultural wastes while producing bio-gas or methane gas. This concept has been extensively applied in Europe and India during energy shortages. Similar equipment has been used for gas production with domestic wastes. Primarily, disadvantages are the amount of management required due to the sensitivity of the digesters, the high initial investment required for equipment, and the fact that the wastes still must be disposed of after digestion. Research is in progress to make the process more practical for energy production. Bacteriologists are investigating new strains of bacteria and culturing techniques for producing methane. Engineers are investigating digester designs and operation to reduce construction and operational requirements and costs.

1 R.W. Hansen, former Colorado State University Cooperative Extension specialist and associate professor. 9/92. Reviewed 1/03 by L.R. Walker, Cooperative Extension specialist, chemical and bioresource engineering.

http://saleemindia.blogspot.com

TEAM (TERI Enhanced Acidification and Methanation) process Bio gas plant

http://www.teriin.org/energy/waste.htm
Magnitude of waste and potential for energy recovery
Waste disposal is one of the major problems being faced by all nations across the globe. The daily per capita solid waste generated in India ranges from about 100 g in small towns to 500 g in large towns. It takes anywhere between three and seven days for the waste to be disposed from the time of its generation. Major portion of the collected waste is dumped in landfill sites. The recyclable content of waste ranges from about 13% to 20%. In a developing country like India, paper, plastic, glass, rubber, ferrous and non-ferrous metals – all the material that can be recycled are salvaged from this waste to produce low-cost products extensively used by the lower-income groups of the society. However, data collected from 44 Indian cities have revealed that about 70% of them do not have adequate capacity for collection and transportation of MSW (municipal solid waste) (Pachauri and Sridharan 1998). The uncollected waste that usually finds its way in sewers is eaten by the cattle, or left to rot in the open, or burnt on roadsides.
In the face of burgeoning urban populations and growing mounds of garbage, initiatives like converting garbage into energy could show the way for cities. A private company has begun converting the city's garbage into fuel pellets and now plans to establish a 10 MW power plant. According to TIFAC (Technology Information Forecasting and Assessment Council), Delhi, Mumbai, and Calcutta would be generating 5000 tonnes of garbage every day, in about a decade, and disposal would be difficult. The existing dumping years would create enormous pollution and health hazards. Municipal authorities would find it expensive to transport garbage and dispose it of scientifically, according to a TIFAC data sheet on 'Fuel pellets from municipal waste'. As part of a pilot project for integrated waste management, the Department of Science and Technology had established a prototype fuel pelletization plant at Deonar, Mumbai, in the early 1990s. The plant was designed to process Indian garbage. The garbage was first dried to bring down the high moisture levels. Sand, grit, and other incombustible matter were then mechanically separated before the garbage was compacted and converted into pellets. Fuel pellets have several distinct advantages over coal and wood, according to the TIFAC data sheet. It is cleaner, free from incombustibles, has lower ash and moisture contents, is of uniform size, cost-effective, and eco-friendly (The Hindu, 2 May 2000).
In addition to MSW, large quantity of waste, in both solid and liquid forms, is generated by the industrial sector like breweries, sugar mills, distilleries, food-processing industries, tanneries, and paper and pulp industries. Out of the total pollution contributed by industrial subsectors, 40% to 45% of the total pollutants can be traced to the processing of industrial chemicals and nearly 40% of the total organic pollution to the food products industry alone. Food products and agro-based industries together contribute 65% to 70% of the total industrial waste water in terms of organic load (Pachauri and Sridharan 1998a). Table 1 gives an estimate of waste generated in India by various sectors and industries.
Table 1 Estimated quantity of waste generated in India
Waste
Quantity
Municipal solid waste
27.4 million tonnes/year
Municipal liquid waste (121 class I and II cities)
12145 million litres/day
Distillery (243 nos)
8057 kilo litres/day
Pressmud
9 million tonnes/year
Food and fruit processing waste
4.5 million tonnes/year
Willow dust
30000 tonnes/year
Dairy industry waste (COD level 2 kg/m3)
50–60 million litres/day
Paper and pulp industry waste (300 mills)
1600 m3 waste water/day
Tannery (2000 nos)
52500 m3 waste water/day
Source Bakthavatsalam (1999)
In addition, the daily per capita sewage generation is about 150 litres. The total sewage generated in India, about 5 billion litres/day in 1947, grew to 30 billion litres/day in 1997. However, the total treatment capacity available is only about 10% of this quantum generated. It is estimated that under the Ganga Action Plan, 46 000 Nm3 (normal cubic metre) of biogas can be produced daily from the sewage treatment plants in 21 Indian cities by treating about 339 million litres/day of municipal waste water. This, with appropriate biogas power plants, will generate total electrical energy of 99 450 kWh/day (Singh 1996).
The urban municipal waste (both solid and liquid) – industrial waste coming from dairies, distilleries, pressmud, tanneries, pulp and paper, and food processing industries, etc., agro waste and biomass in different forms – if treated properly, has a tremendous potential for energy generation as shown in Table 2.
Table 2 Estimated renewable energy potential in India
Energy source
Estimated potential
Bio energy
17000 MW
Draught animal power
30000 MW
Energy from MSW
1000 MW
Biogas plants
12 million plants
Source Bakthavatsalam (1999)
Options for waste management
Last year, the INSWAREB (Institute of Solid Waste Research and Ecological Balance) came up with the theory that rice husk, a cheap by-product of paddy milling, has the potential to galvanize the electricity-starved rural India. With a gross calorific value of 3000 kcal/kg, rice husk, capable of high-efficiency combustion, could serve as the fuel for mini power plants of 1 to 2 MW capacity that can be set up in rural areas. The RHA (rice husk ash), obtained as a by-product by burning it, can generate power in the process.
The cost of establishing and maintaining the mini power plant can be easily made good by exporting RHA, which can fetch $50 a tonne. INSWAREB has drawn an action plan for promoting RHA fully exploiting its export potential. It proposes to initiate a couple of mini power plants to popularize the theme. (The Hindu, 9 February 1999).
Similarly, at an inter-ministerial meeting involving the ministries of power, environment and forests, and urban affairs and employment, it was decided to encourage the use of fly ash bricks in all construction activities. The NTPC (National Thermal Power Corporation) had thought of setting up two fly ash brick manufacturing plants at Badarpur and Dadri near Delhi; the theory being that fly ash, apart from being used as a substitute for bricks, could also be utilized for the embankment of roads.
The enormous amount of ash generated in Indian thermal power stations poses a serious threat to the environment. In principle, this problem can be tackled by using fly ash in building construction. Increased awareness and use of fly ash bricks, which is stronger (100 kg/cm2 compared to 50–75 kg/cm2 of conventional bricks) and smoother on the sides (reducing plastering costs significantly), can provide an eco-friendly solution. Fly ash bricks are better than traditional bricks in the sense also that ash bricks do not use the top fertile soil of the earth, thus protecting the land from agricultural use. Located at the south-east corner of Delhi, the BTPS (Badarpur Thermal Power Station) meets more than 25% of the energy consumption of the capital. It also produces a staggering amount of ash every day (almost 5000 tonnes). The station has, however, been making concrete efforts in ash utilization as a responsible corporate citizen. It has given a major thrust in ash utilization through the manufacture of bricks from fly ash. At present, it has seven units given to private contractors, which manufacture around 16 000 bricks every day. The BTPS had installed a pilot-cum-demonstration plant at its ash dyke way back in 1993. The station adopted the FAL-G technology for the manufacture of ash bricks, which does not require firing or autoclaving. These bricks require natural drying and hence are totally energy-efficient and environment-friendly (The Financial Express, 4 April 1999).
It was also estimated that an energy-from-waste plant, which was to be set up in Scotland, would annually convert 120 000 tonnes of the city's municipal and commercial waste into electricity. It as also to deal with small amounts of non-hazardous clinical and liquid wastes. Besides generating adequate electricity for the plant's in-house needs of around 2.2 MW, it would sell 8.3 MW to the National Grid, electricity distribution network of UK. The facility incorporated two separate systems – fuel processing and combustion.
To produce the fuel, incoming waste is fed into one of the two hammer mills, where it is shredded into coarse floc material. Each of the mills handles 30 tonnes of waste an hour, almost double the plant's throughput of 15.6 tonnes an hour. The over-capacity allows for unplanned downtime. Magnets remove ferrous materials before the floc is carried by conveyor to a fuel-storage building capable of holding enough for two days’ operation—about 800 tonnes of refuse-derived fuel (The Hindu, 21 October 1999).

Role of the scientists
Scientists have developed a technique to treat foul-smelling polluted distillery wastes, using energy from the sun and a chemical catalyst. Tests on a small laboratory-type reactor showed that the method can detoxify 100 litres of diluted distillery waste water in five days. Results of the project at the NARI (Nimbkar Agriculture Research Institute) at Phaltan in Maharashtra were submitted to the MNES (Ministry of Non-conventional Energy Sources). The scientists had applied for a patent on the chemical catalyst. The emphasis after this was to try to improve the technique so that waste treatment is over in just two days. The NARI scientists had taken cues from work on solar detoxification of ground-water and industrial wastes using titanium dioxide catalyst.
By purifying biogas produced from distillery wastes, scientists claimed to have generated huge quantities of com-pressed methane, a gas with immense potential as an alternative source of vehicle fuel. Experimenting with bulk distillery wastes from alcohol manufacturing breweries, researchers from the chemical engineering department of the Jadavpur University produced the gas by a process called biomethanation of the effluents. The process, which also cuts down on the environment pollution, has proved to be an eco-friendly energy production method (The Observer of Business and Politics 25 April 2000).

TERI shows the way
TERI—scientists has been developing new technologies to tackle the problem of waste management
TERI has developed a high-rate digester for fibrous and semi-solid municipal waste with the promise of revolutionizing the waste disposal industry. Described as TEAM (TERI Enhanced Acidification and Methanation) process, for which the patent has also been filed, the digester is said to be quick, economically viable, and suitable for food and agro-based industries and markets. In the face of evident environmental drawbacks of waste disposal methods like land-filling and incineration, the process of biomethanation of waste by anaerobic digestion has economical and social benefits apart from being environment-friendly (The Hindu, 18 March 2000).
TERI began work on the development of a high-rate digester for fibrous and semi-solid MSW in 1996. TEAM process is the culmination of these efforts. The salient features of TEAM are listed below.
Lowered retention time (7 days) and plant area for the whole process to make it economically viable as compared to conventional single phase reactors (30–40 days) or aerobic composting (3 to 6 months)
Complete elimination of engineering problems like scum formation, floating of feed leading to incomplete digestion, feed flow problem, etc.
Technology suitable for adoption by small entrepreneurs
Low water consumption because of reuse of the UASB reactor overflow to acidification reactor
Production of good quality biogas, which can be used for power generation or thermal application like cooking or production of process steam as per the needs,
The decrease in total volume of the feed stock after decomposition is more than 50%
The residue after drying is good organic manure.
Currently, a bench-scale plant for processing 50 kg of vegetable waste per day is operational at the Gual Pahari campus of TERI, at Gurgaon, and efforts are under way for upscaling.
The wastes generated by various sectors need to be assessed and evaluated for their energy potential or reuse in any other form. Biomethanation has emerged as the best option for the treatment of high organic content liquids for energy generation. The use of this technology to Indian MSW is still in its developmental stage. Once a commercially proven technology is established, it will go a long way in dealing with energy problems in the country.