Garbage Gasification - A Better Garbage Disposal Technology?
Published by Mackintosh | August 10, 2012 - 10 hours 31 min ago
1. Explanation of plasma gasification
Plasma gasification is a garbage disposal technique that converts garbage into energy in the form of electricity (Tech-FAQ, 2012). It uses a technology known as plasma technology to convert organic matter into syngas, its basic molecular structure. Although plasma technology has been around for many years, it was only recently that plasma gasification has been taken into consideration (Recovered Energy, n.d.). As landfills are filling up and the cost of fuel to transport garbage is constantly rising, plasma gasification is an option countries around the world can explore. The garbage is placed into an auger, which is a machine that shreds it into smaller pieces (Tech-FAQ, 2012). The smaller pieces are moved into the plasma chamber, a sealed stainless steel vessel that contains nitrogen or air. A high voltage electrical current is passed between two electrodes, which removes electrons from the air, and creates plasma. With a constant flow of electricity through the plasma, the intense energy is powerful enough to disintegrate the small garbage pieces into its base elements (Tech-FAQ, 2012). The main purpose of plasma gasification is to generate electricity, and reduce the large amounts of garbage being sent to landfills (Tech-FAQ, 2012).
2. Four other types of gas technologies
Four other types of gasification technologies are: counter-current fixed bed/co-current fixed bed, fluidized bed and entrained flow (the ENERGY lab, n.d.). The counter-current fixed bed gasifier and co-current fixed bed gasifier both involve a layer of fuel that is at a constant level by adding fuel from the top of the gasifier. The gasification agent is added in two different ways. For counter-current fixed bed, the gasification agent is added from the bottom otherwise known as “up draft”. When the gasification agent is added the same way the fuel is, it is called co-current fixed bed (Department of Medical Engineering, 2007). Fluidized bed gasifiers convert biomass waste products into combustible gas. During fluidized bed gasification, air is blown into the bed gasifier at a constant speed. As the gasifier is being heated, the fuel is added from the bottom. The materials will instantly heat up to the gasifier temperature (Energy Products of Idaho, 2012). In an entrained flow gasifier, coal, steam and air are added from the top. This causes the temperature to increase, which melts the materials into slag (Emerging Fuels, n.d.).
3. Entrained Flow technology vs. Plasma technology
Similarities and Differences
- Both of the gasification techniques require oxygen (Tech-FAQ, 2012)
- Both of them produce simple molecules that can be reused (Tech-FAQ, 2012)(the ENERGY lab, n.d.)
- Entrained flow requires more oxygen due to the way it gasifies, but plasma technology requires less (the ENERGY lab, n.d.)
-The fuels are used differently. In Entrained flow, the fuel is mixed with the oxygen, but in plasma, the fuel is passed through (Recovered Energy, n.d.)
4. List the toxic emissions generated by plasma technology
Plasma gasification produces three main products. It produces synthetic gas (syngas), slag and heat (Strickland, J, 2012). Syngas contains main gases, but mainly contains hydrogen and carbon monoxide. Syngas can be used as a fuel source. Although harmful gases such as carbon dioxide, nitrogen oxide and sulfur oxide, their emissions to the atmosphere are rather low. The nitrogen oxides and sulfur oxides, which can be found in syngas, is cleaned after the plasma gasification process (Westinghouse Plasma, 2012). The carbon dioxide produced can be captured to lower greenhouse gas emissions. After the syngas is fully processed, it can be used to create diesel fuels, heat, steam and electricity. The slag, which contains metal and non-combustible inorganics, can be used as construction materials. The toxic emissions of plasma technology are rather low because most of the gases are contained and cleaned (Strickland, J, 2012). The electricity produced from the syngas can be reused for the plasma gasification itself, or sold to electricity companies. Although some toxic emissions are captured and cleaned, some of it is released into the atmosphere (Tech-FAQ, 2012).
5. Environmental and social impacts of emissions
Environmental Impacts
Plasma gasification converts waste into clean synthesis gas, slag and a small amount of residual waste product as well as heat. Solids produced are recovered metals and marketable slag material that is inert and virtually un-leachable, meaning they will not contaminate our underground water supplies (Alliance Federated Energy, 2010). Plasma gasification produces useable slag instead of potentially hazardous bottom ash and minimal quantities of fly ash or particulate matter, which requires land filling or special facilities with engineered retaining walls (Westinghouse Plasma, 2012). Plasma gasification of Municipal Solid Waste (MSW) to generate electricity produces substantially less carbon dioxide and other emissions per megawatt-hour of electricity produced than traditional mass-burn incineration. Furthermore plasma gasification is cleaner, higher in energy conversion, and better for the environment. Lastly, up to 50% more electricity can be produced per ton with plasma gasification as compared with incineration. (Alliance Federated Energy, 2010)
Social Impacts
Plasma gasification is a reliable technology that deals with the disposal of hazardous waste safely. Plasma gasification offers a highly efficient method to mitigate the risk of dangerous toxins—by eliminating them (Westinghouse Plasma, 2012). This is very useful to society and human health, as it removes hazardous materials from the environment and our cities, and turns it into safe, clean energy. The process is not only environmentally friendly due to its closed nature, but it also eliminates sources of waste and garbage in the environment, which clears the land and oceans of useless clutter. With most of the dangerous toxins eliminated, the plasma gasification process is very safe and is not hazardous to human health.
6. Techniques to treat emissions and waste
The principal product of plasma gasification is synthesis gas composed of carbon monoxide and hydrogen. This gas can be burned to produce heat and steam, chemically scrubbed and filtered to remove impurities, or cleaned and used as a turbine or engine fuel to produce electricity. Heat energy can also be recovered through water tube heat exchangers when the hot syngas is cooled. Similarly, the slag can be treated in many different ways. Slag takes on many different forms depending on how it is cooled. If slag is air-cooled, it forms black, glassy rocks that look and feel like obsidian, which can be used in concrete or asphalt. When compressed air is blown through a stream of molten slag, rock wool is formed. Rock wool has the appearance of gray cotton candy and is a very efficient insulation material. The rock wool is twice as effective as fiberglass, lighter than water, and also very absorbent. (Strickland, J, 2012).
7. List of cities in Ontario and Canada using this technology
• Tekna Plasma Systems, Inc., Sherbrooke, Quebec, Canada (Plasmas Science and Technology, n.d.)
• RCL Plasma, Inc., Ottawa, Ontario, Canada (Plasmas Science and Technology, n.d.)
• Plasco Energy Group, Ottawa, Ontario, Canada (Plasmas Science and Technology, n.d.)
• SatCon Power System, Burlington, Ontario, Canada (Plasmas Science and Technology, n.d.)
• IE Power, Inc., Mississauga, Ontario, Canada (Plasmas Science and Technology, n.d.)
8. Impact success rate
The plasma gasification process has a very high success rate for many reasons. Using the Plasma Gasification System, there is approximately a 99 percent conversion from solid-state waste to syngas. The remaining 1 percent is transformed into slag (Shimkus, J, 2011). Due to the nearly total destruction and reformation of the organic waste fed into the system produces very little in the way of emissions of greenhouse gas or hazardous pollutants (Burger, A, 2009). Steam produced during the gasification process is collected and fed into the electricity generation process to improve its efficiency (Lahey, J, 2008). Furthermore, the PGP system can process any waste stream such as Municipal Solid Waste, biomedical waste and spent pot liner, biomass, oil shale, automobile fluff, lead contaminated and more (Lahey, J, 2008). Finally, there is virtually no limit to the amount of waste which can be processed, meaning the machine can handle tons of waste every day (Lahey, J, 2008).
9. Describe the methods of garbage disposal in your city
There are a few different types of methods for garbage disposal in Toronto. The main method of garbage disposal in Toronto are landfills (City of Toronto, 2012). Items are only placed into a landfill if they cannot be recycled or reused. Other methods of disposal include the green bin which collects organic waste (fruit and vegetable, spoiled meat) for composting (City of Toronto, 2012). Another method is blue bins. Blue bins are designated to recycle anything from paper to plastics (City of Toronto, 2012). Trucks provide their service of picking up the waste from residential and industrial sites regularly, in an organized fashion. These trucks are provided by the Mini Millennium Disposal Services. Due to their nature and composition, old or unwanted electronics are recycled and kept out of landfills. (City of Toronto, 2012)
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