Waste converter
Encyclopedia
A waste converter is a machine used for the treatment and recycling of solid and liquid refuse material. A converter is a self-contained system capable of performing the following functions: pasteurization
of organic waste; sterilization
of pathogenic or biohazard waste; grinding and pulverization of refuse into unrecognizable output; trash compaction; dehydration
. Because of the wide variety of functions available on converters, this technology has found application in diverse waste-producing industrial segments. Hospitals, clinics, municipal waste facilities, farms, slaughterhouses, supermarkets, ports, sea vessels, and airports are the primary beneficiaries of on-site waste conversion.
The converter is an evolution of the autoclave
, invented by Sir Charles Chamberland in 1879, but differs from a waste autoclave
in several key characteristics. While the autoclave relies on high temperature and pressure to achieve moist heat sterilization
of waste, a converter operates in the atmospheric pressure range. Superheating
conditions and steam generation are achieved by variable pressure control, which cycles between ambient and negative pressure within the sterilization cell. The advantage of this updated approach is a safer and less complicated operation that does not require a pressure vessel
. Additionally, while autoclaves require external water input, modern converters utilize the moisture content already present in the conversion cell to generate steam sterilization conditions. Any water that is introduced into the process can be recycled in a closed-loop system as opposed to being dumped as run-off sewage. In general, the converter is a simplified, cleaner, and more efficient update to Sir Charles's invention.
Converter technology is an environmentally-friendly alternative to other traditional means of waste disposal that include incineration
, plasma arc, and landfill dumping in that waste conversion results in a small carbon footprint
, avoids polluting emissions into the atmosphere, and results in a usable end product such as biofuel
, soil compost
, or building material (see also Refuse-derived fuel
).
(municipal solid waste) or infectious waste, depending on the type of plant, is sterilized and converted into a sterilized organic and inorganic, innocuous end-product. Machines used in such large-scale applications process between 1,000 and 4,000 kg of waste per hour. At the end of each cycle, lasting as little as half-hour in Converters (that are capable of grinding), the pulverized, sanitized, and dehydrated product is off-loaded and segregated for other uses. Some of the product is routed for use in pulp production, composting, or refuse-derived fuel.
Applications outside of waste treatment centers are increasingly common due to the portability and simplicity of modern converters. Hospitals are a large beneficiary of converter technology, which allows for the immediate treatment of potentially infected hazardous waste at its source. Hospitals and clinics equipped to have a zero hazardous waste footprint operate by having a converter placed on every floor where single use sanitary items such as needles, scalpels, bandages, and blood bags are immediately converted into innocuous product. In addition to the marked improvement in sanitation, on-site treatment of hazardous waste allows operational cost savings for these facilities. The government of Tuscany, Italy for example calculated an annual figure of 8 Million Euro that was saved by turning to on-site treatment of medical hospital waste.
Supermarkets and food producers who dump unused food waste in municipal landfills at a rate that is alarming many conservationists, have found a use for converter technology. By processing unused and decomposing food matter together with packaging and other refuse on site, supermarkets have achieved improvements in terms of waste disposal costs. This is in addition to improvements in public perception, which had been seriously critical of the amount of waste sent to landfills by food stores. In the UK alone 6.7 million metric tons of food waste goes into landfills each year, resulting in 8 million metric tons of CO2 being emitted.
Farms, slaughterhouses, and other food producers are likewise becoming more involved in on-site waste conversion. Larger installations especially, where garbage hauling is a major and expensive operation, currently have economic and legislative incentives to move towards operating own converters. Recent drives toward environmentally conscious or "green" technologies have even provided government budgets for such installations.
Naval vessels, cruise liners and off-shore installations such as gas-drilling rigs and oil platforms are another logical application of converter technology. Due to the extended isolation periods of sea-going vessels and off-shore platforms there is an issue of how to store and dispose of refuse in an efficient and sanitary way. World-wide legislation on sea dumping is strict and does not allow, under stringent penalties, any ships or sea vessels to dump waste, gray water, or even ballast water that has been collected in a remote geographic location due to the danger of biological contamination. Ship-generated waste is either held and disposed of in port waste disposal facilities, or can be converted directly on the vessel for easier storage and at times (depending on waste composition) for additional fuel.
The converter is one of the "green technologies" available today for waste treatment. There is a clear and definite positive environmental impact stemming from the use of waste conversion into biofuel
, building material, and soil compost. In 2009 ever-increasing numbers of waste exporters around the world are finding it difficult to find buyers for their cargo. Increasing numbers of local and national governments are also turning to recycling and conversion technology to relieve the pressure on already-full or overfilled landfills. Waste conversion, augmented by traditional recycling methods, now allows nearly 99% of all MSW to be reused in some way, thus sharply reducing the demand on landfills.
In 1980 only about 10% on municipal solid waste was recycled, and the product consisted largely of paper and glass recycled material. With the widespread use of autoclaves, that percentage climbed to a significant 45% by the year 2000, when composting and energy recovery became more common. With the evolution of the autoclave and the arrival of converters new uses of converted product are emerging on an ongoing basis. Some application only recently implemented are: Composting and combining with farm fertilizer, building material such as concrete
additive, gasification fuel, and furnace/boiler pellet additive. The latter two are energy recovery options that only became acceptable on a large scale once the product was demonstrated to burn cleanly and within EPA emission regulations. A notable fact about energy recovery is that even though some waste was already reused in this way as early as 1980, the current generation of converters produces Biomass
Fuel that burns exponentially cleaner than the incinerated waste of those times.
There are environmentally conscious improvements that have been built into the design of converters based on the lessons learned from older technologies. The new machines run on much less power than the large pressure vessel type autoclaves, and can be plugged into 400V power supplies or run off of a small motor as stand-alone units. As a result of this, a new degree of portability became possible, and now facilities such as hospitals are placing dish-washer sized units in every department. One important advent that allowed for a leaner, green technology is the ability of modern converters to transfer mechanical energy and friction force on the waste mass into heat energy that is used in the pasteurization and sterilization processes.
The precise conditions needed to achieve pasteurization
and sterilization
are controlled by a programmable logic controller
(PLC) in millisecond intervals. This level of control in modern units has allowed for the simplification of autoclave technology to the point where heavy and potentially dangerous pressure vessels are not needed, and sterilization conditions are reached by depressing the conversion cell and continuing to evaporate moisture from the product under negative pressure
. The result is a statistically safer and more reliable machine, which is also smaller and lighter than older autoclaves.
The conversion cycle consists of several sequential steps or phases. The waste is first ground and pulverized to an unrecognizable mixture by a combination of fixed and actuated hardened steel blades. The mixture is then heated through the injection of steam and also by the heat generated by frictional forces of the grinding phase. The exact temperature required to pasteurize, and in the subsequent phase to sterilize the waste, is maintained for a time that allows for a 18 log 10 reduction in microorganisms. In order to eliminate the required amount of microorganisms required by government regulations, a complete saturation of waste matter with superheated steam is required for a minimum amount of time, also regulated by environmental agencies. The modern converter achieves saturation within 10–15 minutes due to the high degree of pulverization preceding the sterilization phase, whereas older models required up to several hours to saturate and sterilize the same load.
The cycle ends in a cooling phase, during which product continues to be dehydrated. Upon reaching temperature at which product is safe to handle, near ambient temperature, the cycle automatically shuts down. The end product is expelled into a tray that can then be hauled off for storage. The entire process and statistics are recorded and stored in computer memory for record keeping.
Waste converters do have indirect competition since there are many modes of waste disposal available in the market. However, most of the 'competing' technologies can be added into a larger waste conversion process that will usually place the waste converter at the forefront of a supply chain for on-site waste conversion into a sanitized and dehydrated bulk material. Following processing, the bulk material will follow one of several process paths; see Applications section.
Plasma-arc gasification
plants are able to process all types of waste under extreme heat that emanates from plasma torches that are in contact with the refuse. Plasma-arc plants produce two types of output; syn-gas, which is collected for use as fuel, and a composite solid that has some properties of plastic and can also be recycled for use in consumer goods. Plasma-arc and gasification plants are highly complex installations and only compete with converter technology at the level of industrial-size converters. The two technologies can still be used in series by sterilizing and lightening waste on-site, before sending it to a gasification plant for syn-gas extraction. This way transportation and storage costs are kept down while maintaining a more sanitary operation. Adding a waste converter at the front-end of a gasification process will theoretically produce less emissions and a cleaner, more usable end product.
Micro-wave and other irradiation sterilization has been used to sterilize bio-hazard material in large quantities, but all such approaches suffer from major drawbacks as compared to converters. Irradiation plants are large installations that are expensive to build and maintain, and must necessarily be hub locations as part of a larger supply chain. There is also a health risk and a danger of exposure to radioactive material in installations that use energy sources for generation of gamma rays and other types of radiation. In general, Micro-wave and Irradiation technology was used to treat hazardous pathogenic waste before the widespread adoption of moist-heat sterilization that both autoclaves and converters use. These solutions have been economically forced out of the mainstream use because of their high complexity and operational costs.
The introduction of autoclaves was a big step in the direction of widespread treatment of refuse, and so many functional forms of autoclaves are currently in operation at landfills and treatment centers around the world. Some common features of autoclaves that differentiate them from competing technologies are as follows. Autoclaves employ the moist-heat method to sterilize and deactivate refuse in a large pressure vessel where saturated steam is injected. The end product is completely sanitized and even previously bio-hazardous waste can be discarded in a normal municipal landfill. Autoclaves employ the same method of sterilization as converters, but do so using larger and more complex equipment that also has higher safety and energy consumption requirements. In a majority of cases, autoclaves are hub-and-spoke operations requiring regional treatment centers and a supply chain.
Incineration and compaction have traditionally been treatment options and still compete with newer technologies by virtue of having a proven track record. These solutions are widely recognized as obsolete due to their impact on the biosphere; while compaction has nearly no effect on the long-term goal of reducing waste dumping, incineration had been notorious for polluting the atmosphere. While incineration is popular for its ability to recover energy from waste, it has been widely debated and regulated in order to preserve clean air. One solution that had been instituted to update incineration technology is to add converter stations into the supply chain of clean-burning RDF, of refuse-derived fuel. This, along with advanced filtering and condensation scrubbers was able to render energy recovery from waste a feasible and eco-friendly solution.
http://www.cali.gov.co/
http://www.ecogeek.org/content/view/2510/81/
http://www.ecologicasud.it
http://www.environmentalleverage.com
http://www.epa.gov
http://www.gov.bw/
http://www.hitechambiente.com/index.asp
http://www.ms.ro/
http://www.organicfarming.com.au/
http://www.smrc.com.au/
http://www.svswa.org/
Sterilizzatore "Converter", University of Napoli study by Prof. Paolo Marinelli
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
of organic waste; sterilization
Sterilization (microbiology)
Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...
of pathogenic or biohazard waste; grinding and pulverization of refuse into unrecognizable output; trash compaction; dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
. Because of the wide variety of functions available on converters, this technology has found application in diverse waste-producing industrial segments. Hospitals, clinics, municipal waste facilities, farms, slaughterhouses, supermarkets, ports, sea vessels, and airports are the primary beneficiaries of on-site waste conversion.
The converter is an evolution of the autoclave
Autoclave
An autoclave is an instrument used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents. It was invented by Charles Chamberland in 1879, although a precursor known as the...
, invented by Sir Charles Chamberland in 1879, but differs from a waste autoclave
Waste autoclave
A waste autoclave is a form of solid waste treatment that utilises heat, steam and pressure of an industrial autoclave in the processing of waste. Waste autoclaves process waste either in batches or in continuous-flow processes. In batch processes, saturated steam is pumped into the autoclave at...
in several key characteristics. While the autoclave relies on high temperature and pressure to achieve moist heat sterilization
Moist heat sterilization
Heating an article is one of the earliest forms of sterilization practiced. Moist heat, as the name indicates, utilizes hot air that is heavily laden with water vapour and where this moisture plays the most important role in the process of sterilization....
of waste, a converter operates in the atmospheric pressure range. Superheating
Superheating
In physics, superheating is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling...
conditions and steam generation are achieved by variable pressure control, which cycles between ambient and negative pressure within the sterilization cell. The advantage of this updated approach is a safer and less complicated operation that does not require a pressure vessel
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
. Additionally, while autoclaves require external water input, modern converters utilize the moisture content already present in the conversion cell to generate steam sterilization conditions. Any water that is introduced into the process can be recycled in a closed-loop system as opposed to being dumped as run-off sewage. In general, the converter is a simplified, cleaner, and more efficient update to Sir Charles's invention.
Converter technology is an environmentally-friendly alternative to other traditional means of waste disposal that include incineration
Incineration
Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas, and...
, plasma arc, and landfill dumping in that waste conversion results in a small carbon footprint
Carbon footprint
A carbon footprint has historically been defined as "the total set of greenhouse gas emissions caused by an organization, event, product or person.". However, calculating a carbon footprint which conforms to this definition is often impracticable due to the large amount of data required, which is...
, avoids polluting emissions into the atmosphere, and results in a usable end product such as biofuel
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...
, soil compost
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...
, or building material (see also Refuse-derived fuel
Refuse-derived fuel
Refuse-derived fuel or solid recovered fuel/ specified recovered fuel is a fuel produced by shredding and dehydrating solid waste with a Waste converter technology. RDF consists largely of combustible components of municipal waste such as plastics and biodegradable waste...
).
Applications
Application of the converter is common in centralized waste conversion centers, where large machines process waste on an industrial scale. MSWMSW
-Computers:*Microsoft Windows, an operating system*Machine Status Word, a data segment in the LOADALL instruction set for Intel 286 processors*Microsoft Office Word, a proprietary word processor-Science and Engineering:...
(municipal solid waste) or infectious waste, depending on the type of plant, is sterilized and converted into a sterilized organic and inorganic, innocuous end-product. Machines used in such large-scale applications process between 1,000 and 4,000 kg of waste per hour. At the end of each cycle, lasting as little as half-hour in Converters (that are capable of grinding), the pulverized, sanitized, and dehydrated product is off-loaded and segregated for other uses. Some of the product is routed for use in pulp production, composting, or refuse-derived fuel.
Applications outside of waste treatment centers are increasingly common due to the portability and simplicity of modern converters. Hospitals are a large beneficiary of converter technology, which allows for the immediate treatment of potentially infected hazardous waste at its source. Hospitals and clinics equipped to have a zero hazardous waste footprint operate by having a converter placed on every floor where single use sanitary items such as needles, scalpels, bandages, and blood bags are immediately converted into innocuous product. In addition to the marked improvement in sanitation, on-site treatment of hazardous waste allows operational cost savings for these facilities. The government of Tuscany, Italy for example calculated an annual figure of 8 Million Euro that was saved by turning to on-site treatment of medical hospital waste.
Supermarkets and food producers who dump unused food waste in municipal landfills at a rate that is alarming many conservationists, have found a use for converter technology. By processing unused and decomposing food matter together with packaging and other refuse on site, supermarkets have achieved improvements in terms of waste disposal costs. This is in addition to improvements in public perception, which had been seriously critical of the amount of waste sent to landfills by food stores. In the UK alone 6.7 million metric tons of food waste goes into landfills each year, resulting in 8 million metric tons of CO2 being emitted.
Farms, slaughterhouses, and other food producers are likewise becoming more involved in on-site waste conversion. Larger installations especially, where garbage hauling is a major and expensive operation, currently have economic and legislative incentives to move towards operating own converters. Recent drives toward environmentally conscious or "green" technologies have even provided government budgets for such installations.
Naval vessels, cruise liners and off-shore installations such as gas-drilling rigs and oil platforms are another logical application of converter technology. Due to the extended isolation periods of sea-going vessels and off-shore platforms there is an issue of how to store and dispose of refuse in an efficient and sanitary way. World-wide legislation on sea dumping is strict and does not allow, under stringent penalties, any ships or sea vessels to dump waste, gray water, or even ballast water that has been collected in a remote geographic location due to the danger of biological contamination. Ship-generated waste is either held and disposed of in port waste disposal facilities, or can be converted directly on the vessel for easier storage and at times (depending on waste composition) for additional fuel.
Environmental Impact
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...
, building material, and soil compost. In 2009 ever-increasing numbers of waste exporters around the world are finding it difficult to find buyers for their cargo. Increasing numbers of local and national governments are also turning to recycling and conversion technology to relieve the pressure on already-full or overfilled landfills. Waste conversion, augmented by traditional recycling methods, now allows nearly 99% of all MSW to be reused in some way, thus sharply reducing the demand on landfills.
In 1980 only about 10% on municipal solid waste was recycled, and the product consisted largely of paper and glass recycled material. With the widespread use of autoclaves, that percentage climbed to a significant 45% by the year 2000, when composting and energy recovery became more common. With the evolution of the autoclave and the arrival of converters new uses of converted product are emerging on an ongoing basis. Some application only recently implemented are: Composting and combining with farm fertilizer, building material such as concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
additive, gasification fuel, and furnace/boiler pellet additive. The latter two are energy recovery options that only became acceptable on a large scale once the product was demonstrated to burn cleanly and within EPA emission regulations. A notable fact about energy recovery is that even though some waste was already reused in this way as early as 1980, the current generation of converters produces Biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
Fuel that burns exponentially cleaner than the incinerated waste of those times.
There are environmentally conscious improvements that have been built into the design of converters based on the lessons learned from older technologies. The new machines run on much less power than the large pressure vessel type autoclaves, and can be plugged into 400V power supplies or run off of a small motor as stand-alone units. As a result of this, a new degree of portability became possible, and now facilities such as hospitals are placing dish-washer sized units in every department. One important advent that allowed for a leaner, green technology is the ability of modern converters to transfer mechanical energy and friction force on the waste mass into heat energy that is used in the pasteurization and sterilization processes.
Operation
A typical treatment cycle will begin with the loading of unsorted waste material and end in the offload of a dry powder (product), which now possesses new characteristics and that the input material did not. The garbage is loaded into a chamber, also the conversion cell, by hand or through the use of a loading elevator or conveyor belt, depending on the application and toxicity/danger level associated with handling the waste. The previous batch of post-treatment product is removed and a new cycle is started through an electronic control panel. Modern converters are fully automatic and will finish the computer controlled cycle autonomously, unless a failure occurs.The precise conditions needed to achieve pasteurization
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
and sterilization
Sterilization (microbiology)
Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...
are controlled by a programmable logic controller
Programmable logic controller
A programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...
(PLC) in millisecond intervals. This level of control in modern units has allowed for the simplification of autoclave technology to the point where heavy and potentially dangerous pressure vessels are not needed, and sterilization conditions are reached by depressing the conversion cell and continuing to evaporate moisture from the product under negative pressure
Negative pressure
Negative pressure may refer to:*negative pressure as opposed to positive pressure*stretched liquid*vacuum*negative gauge pressure, a way of expressing pressure measurements below atmospheric pressure*suction*transpirational pull...
. The result is a statistically safer and more reliable machine, which is also smaller and lighter than older autoclaves.
The cycle ends in a cooling phase, during which product continues to be dehydrated. Upon reaching temperature at which product is safe to handle, near ambient temperature, the cycle automatically shuts down. The end product is expelled into a tray that can then be hauled off for storage. The entire process and statistics are recorded and stored in computer memory for record keeping.
Competing Technologies
Plasma-arc gasification
Gasification
Gasification is a process that converts organic or fossil based carbonaceous materials into carbon monoxide, hydrogen, carbon dioxide and methane. This is achieved by reacting the material at high temperatures , without combustion, with a controlled amount of oxygen and/or steam...
plants are able to process all types of waste under extreme heat that emanates from plasma torches that are in contact with the refuse. Plasma-arc plants produce two types of output; syn-gas, which is collected for use as fuel, and a composite solid that has some properties of plastic and can also be recycled for use in consumer goods. Plasma-arc and gasification plants are highly complex installations and only compete with converter technology at the level of industrial-size converters. The two technologies can still be used in series by sterilizing and lightening waste on-site, before sending it to a gasification plant for syn-gas extraction. This way transportation and storage costs are kept down while maintaining a more sanitary operation. Adding a waste converter at the front-end of a gasification process will theoretically produce less emissions and a cleaner, more usable end product.
Micro-wave and other irradiation sterilization has been used to sterilize bio-hazard material in large quantities, but all such approaches suffer from major drawbacks as compared to converters. Irradiation plants are large installations that are expensive to build and maintain, and must necessarily be hub locations as part of a larger supply chain. There is also a health risk and a danger of exposure to radioactive material in installations that use energy sources for generation of gamma rays and other types of radiation. In general, Micro-wave and Irradiation technology was used to treat hazardous pathogenic waste before the widespread adoption of moist-heat sterilization that both autoclaves and converters use. These solutions have been economically forced out of the mainstream use because of their high complexity and operational costs.
Incineration and compaction have traditionally been treatment options and still compete with newer technologies by virtue of having a proven track record. These solutions are widely recognized as obsolete due to their impact on the biosphere; while compaction has nearly no effect on the long-term goal of reducing waste dumping, incineration had been notorious for polluting the atmosphere. While incineration is popular for its ability to recover energy from waste, it has been widely debated and regulated in order to preserve clean air. One solution that had been instituted to update incineration technology is to add converter stations into the supply chain of clean-burning RDF, of refuse-derived fuel. This, along with advanced filtering and condensation scrubbers was able to render energy recovery from waste a feasible and eco-friendly solution.
Sources
http://ompeco.comhttp://www.cali.gov.co/
http://www.ecogeek.org/content/view/2510/81/
http://www.ecologicasud.it
http://www.environmentalleverage.com
http://www.epa.gov
http://www.gov.bw/
http://www.hitechambiente.com/index.asp
http://www.ms.ro/
http://www.organicfarming.com.au/
http://www.smrc.com.au/
http://www.svswa.org/
Sterilizzatore "Converter", University of Napoli study by Prof. Paolo Marinelli