Excerpt
Inhaltsverzeichnis
EXECUTIVE SUMMARY
INTRODUCTION
CONCEPT
MATERIAL AND METHOD
FINDINGS AND DISCUSSION
CONCLUSION
ACKNOWLEDGEMENT
REFERENCES
EXECUTIVE SUMMARY
Biodegradable component of municipal solid waste (MSW) may vary but generally is about 60 %, and food waste is about 60 % of the biodegradable component. In a city like Delhi, a total of 8000 MT day -1 MSW is generated (CPCB 2012) and food waste may account for about 2700 MT. Food waste is generated by households, hotels and restaurants etc, and market places. Due to deficient collection and ineffective monitoring and control, food waste is thrown on the street and footpaths, eventually being swept away in drains causing choking of drains and eutrophication. Cooked food to the extent of 40 – 60 % is wasted in different countries, and India is no exception. Putrefying food waste attracts flies, rodents, rats, dogs, birds, and all sorts of scavengers, emit foul smell, and causes environmental degradation. Flies are a known vector of many communicable diseases. Birds get attracted to the putrefying waste by itself, as well by the maggots which may breed in the putrefying food waste. Bird hits are a common cause of aircraft disability, including disasters. Current system of collection transportation and disposal by composting has not been successful in any urban locality in India. Composting require large area of land (not easily available). Treated compost by compost machines also require storage for curing for a period, at least for 7-10 days before it can be used as manure. Energy recovery requires sophisticated equipment, and transfer of the waste in shortest possible time so that energy content in food waste does not get dissipated, and may be a factor for climate change. As per Indian rules (MSW Rules 2000), food waste is to be composted and not sent to landfill. Considering the inadequacy in proper food waste management, and its damaging fallout on the environment and human health, a system of food waste management by application of thermal energy, a non- burn process has been developed and tested. Putrefaction process in the food waste is arrested by destroying the enzymes, and the end product can be used as manure or source of fuel, as the treated waste retains nutrients and calorific value. Advantages are that it is environment friendly process; end products are reusable, and the saves on carbon dioxide and methane emission, essential part of burn technology. Being non- burn process it qualifies for carbon credit.
INTRODUCTION
Biodegradable component of municipal solid waste (MSW) may vary, but generally is about 60 %, and food waste is about 50 - 60 % of the biodegradable component. Food waste is generated by households, hotels and restaurants etc, and market places where food hawkers are in abundance on the streets and footpaths. Due to deficient collection, ineffective monitoring and control, food waste is thrown on the street and footpath eventually being swept away in drains causing choking and eutrophication. Putrefaction continues in food waste by enzyme activity. Cooked food to the extent of 40 – 60 % is wasted in different countries and India is no exception. America throws away 43.6 million tons of food each year (US EPA 2000), and as per another report, 50 % of its food (foodnavigator-usa.com 2009). In the UK, 6.7 million tons food waste gets generated in a year amounting to £ 10.2 billion per year (The Observer 2007). In the food processing industries, up to 30% of incoming raw materials becomes waste rather than a value-added product (Schaub 1996). In another study, it was found that food waste comprised of 50 % of domestic waste (Qdais H.A. Abu 1997). Food waste impacts environment and eventually human health in many ways. Environmental impact of food waste has been reported to have eutrophication potential, acidification potential, and global warming potential (Bernstad 2012).
Putrefying food waste attracts flies, rodents, rats, dogs, birds, and all sorts of scavengers, emits foul smell, and causes environmental degradation. Flies are a known vector of many communicable diseases. Birds get attracted to the putrefying waste by itself, as well as by the maggots which may breed in the putrefying food waste. Bird hits are a common cause of aircraft disability, including aviation disasters (Hindustan Times 2011). Current system of collection transportation and disposal by composting has not been successful in any urban locality in India. Composting require large area of land- not easily available. Treated compost by compost machines also requires storage for curing for a few days before it can be used as manure. Energy recovery (waste to energy concept) requires sophisticated equipment and transfer of the waste in shortest possible time so that energy content in food waste does not get dissipated. As per Indian rules - MSW 2000, food waste is to be composted and not sent to landfill, as in the landfill methane is released which may be 21 times more damaging to the environment compared to carbon dioxide (Asnani 2008).
CONCEPT
Considering the inadequacy in proper food waste management, and its damaging fallout on the environment and human health, a machine for food waste management by application of thermal energy under controlled condition based on non- burn process has been fabricated (VEGMA FOODSTER), and tested. Putrefaction process in the food waste is arrested by destroying the enzymes, and proteins get stabilized by denaturing -an irreversible process (www.friedli.com); and the end- product can be used as manure, or source of fuel as the treated waste retains all ingredients, including calorific value. Advantages are that it is rendered non- attractive to flies, birds, and other scavengers and is environment friendly process. The end products are treated food waste which can be used as manure or fuel pallets, and steam/water which may be used as distilled water for commercial purposes, and the process qualifies for carbon credit.
The technology offered works at the doorstep of waste generation, thus ensuring 100 % collection of waste. It can work in close proximity to the households through Resident Welfare Associations (RWA), and market places, eating joints, hotels and cafeteria etc, thus eliminating the requirement of transportation. Power Consumption would be about 3-4 KW /hr, and cost would be about INR 250 per day assuming that the machine runs 16 cycles day-1. One cycle would be of about 30 to 50 minutes’ duration (depending upon moisture content). About 15 Kg waste would be treated in one cycle (as per the capacity of the vessel of the prototype developed). Treated waste would have a monetary value as manure/fuel pallets and distilled water. There will be no expenditure on transportation stage II and III (carrying the waste in motor vehicles), intermediary storage (Dhalaos),and land requirement for commposting or landfill.
It is an innovative approach to the perpetual problem of management of food waste. Food waste is a global problem. When left on streets and pavements etc it gets washed in drains, thus choking it, and higher nitrogen content would cause eutrophication of water bodies. A pilot study was undertaken which supports the hypothesis that food waste once subjected to thermal application under controlled process become stable and further putrefaction is arrested. Empirical observation confirms that once treated in the process it becomes non-attractive to flies, birds, scavengers etc even if left in the open for a few days.
MATERIAL AND METHOD
Material
1. The machine for food waste management has been fabricated (figure 1) with help from one engineering firm – “Micro Engineering, New Delhi”. The materials used were:
i) Boiler- 5kg/hr capacity of steam
ii) Feed water pump with 1hp motor
iii) 3hp variable speed motor fitted with shredder blade assembly
iv) Outer shell of 18’’ diameter having length of 700-750mm
v) Inner shell of 16 inches’ diameter of same length
vi) Shredder blades are of SS sheet of thickness 3-4mm
vii) Water level controller for boiler, pressure gauge, temperature, Gauge, safety valve, and auto cut-off.
viii) Electrical panel fitted with MCBs for boiler, feed water pump, motor of machine and other control devices.
Note –Once the boiler is heated electricity consumption would reduce substantially. Shredder is operated intermittently. Feed water pump also works intermittently and is controlled by an auto cut arrangement.
The Machine
illustration not visible in this excerpt
Figure 1: Vegma Foodster
2. Assorted food waste collected from households and roadside eateries.
Methodology
Having conceived the idea that food waste can be treated by application of thermal energy a series of meetings with the designers - the Micro Engineering were held where the concept was further examined and design finalized. Based on the concept that proteins get denatured by application of thermal energy a machine was fabricated and run as pilot project. The denaturation process presumably involves an unfolding, or at least an alteration the folded structure of protein molecules. Protein gets denatured by application of thermal energy.
The process is simple. Assorted food waste was collected, measured by weight and fed into VEGMA FOODSTER through the inlet port. The lid was secured and boiler switched on. When it started giving steam the temperature climbed up and on reaching the desired temperature of 1300 C steam was entered in the outer jacket of the machine. The steam then circulated in the outer jacket - a sealed unit, and heat transfer took place incident on the heap of waste, kept in the inner vessel. An in-built shredder was operated intermittently, to increase the surface area of waste for greater impact of thermal energy. Operating temperature was maintained at 130-1350 C for 40-50 minutes. Sample of food waste before and after treatment was collected for testing.
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