Incineration is to dispose of waste materials by burning them. The end results are heat, ash and gases.
High-temperature waste treatment systems are described as “thermal treatment”.
Incinerating reduces the need for landfill but does not eliminate it. It reduces the soid mass of waste by 80–85% . The reamaining ashes still have to be disposed of.
A dump truck drops the municipal waste into a warehouse-sized pit. Then a giant claw (much like one that picks up loot in an arcade game) grabs nearly a truckload of garbage and dumps it into an incinerator.
The incinerator is initially fired up with gas or other combustible material.
The process is then sustained by the waste itself. Complete waste combustion requires a temperature of 850º C for at least two seconds but most plants raise it to higher temperatures to reduce organic substances containing chlorine. Flue gases are then sent to scrubbers which remove all dangerous chemicals from them. To reduce dioxin in the chimneys where they are normally formed, cooling systems are introduced in the chimneys. Chimneys are required to be at least 9 meters above existing structures.
Technology developed in Europe mixes the waste at temperatures of up to 2,000 degrees Fahrenheit. The heat then makes steam, which runs a turbine and produces electricity.
sources
http://www.brighthubengineering.com/structural-engineering/89810-pros-and-cons-of-incineration-for-landfill-relief/
https://www.scientificamerican.com/article/does-burning-garbage-to-produce-energy-make-sense/
The Advantages Of Incineration & Waste To Energy
Pathogens and toxins can be destroyed by high temperatures making incineration a very good choice for certain kinds of waste.
Unlike landfill there is no release of methane. Every ton of MSW incinerated, prevents about one ton of carbon dioxide equivalents from being released to the atmosphere.
The leachates that are produced in landfills by waste are totally eliminated.
By reducing waste it reduces the pressure on landfill space.
As for carbon dioxide—the big class of emissions that isn’t yet regulated—WTE actually performs quite well compared with other methods of electricity generation. On its face, WTE appears to be very carbon-intensive. The EPA reports that incinerating garbage releases 2,988 pounds of CO2 per megawatt hour of electricity produced. That compares unfavorably with coal (2,249 pounds/megawatt hour) and natural gas (1,135 pounds/megawatt hour). But most of the stuff burned in WTE processes—such as paper, food, wood, and other stuff created of biomass—would have released the CO2 embedded in it over time, as “part of the Earth’s natural carbon cycle.” As a result, the EPA notes, only about one-third of the CO2 emissions associated with waste-to-energy can be ascribed to fossil fuels, i.e., burning the coal or natural gas necessary to incinerate the garbage. In other words, WTE really only produces 986 pounds of carbon dioxide per megawatt hour. “So we’re roughly equivalent to natural gas, and half of coal,” Michaels says. “But coal and natural gas don’t manage solid waste.”
However not all good news….
The ashes are toxic and so need further treatment. As such they were cause for concern however “Ash from modern incinerators is vitrified at temperatures of 1,000 °C (1,830 °F) to 1,100 °C (2,010 °F), reducing the leachability and toxicity of residue. As a result, special landfills are generally no longer required for incinerator ash from municipal waste streams”
The gases too need to be “cleaned” of pollutants before they are dispersed into the atmosphere. proponents of the technology claim that the flue scrubbers are up to the job while many others feel there is cause for concern.
Waste To Energy Systems
The heat created when incinerating the waste is used to make electricity which seems like a good idea.
It is important to remember that waste to energy systems do not make money or even cover the cost of waste incineration but they do offset it.
The plants are very expensive to build and once built need a lot of fuel (waste) to run them. They need to be kept running. This means that alternatives forms of waste disposal like recycling are no longer promoted.
Here are some figures from 2009 for Spokane County
WASTE TO ENERGY FACILITY
Mandatory service area: Spokane County / 430,000 ratepayers
Type of contract: Full service/Operate Wheelabrator / Waste Management
Ownership: City of Spokane
Financing ($110 million): Revenue Bonds – Mandatory debt to entire County
Department of Ecology Grant ($60 million)
Start-up: 1991
Expenses and Revenues for 2009:
Cost of Operation $17.2 million ($62 per ton)
Cost of Ash Disposal $4.1 million ($47 per ton)
Cost of Debt $9 million
TOTAL COSTS $30.3 million
Electricity Revenue $11.4 million
Materials Recovery $0.1 million
NET COST OF OPERATIONS $18.8million ($68 per ton)
Refuse Combustion:
Operation: 24-hours per day, 7 days per week
Process Lines: 2 @ 400 tons-per-day
Plant maximum daily capacity: 800 tons
Average thru-put: 720 tons per day (365 days per year)
Feed system: 2 overhead refuse cranes with ram feeder
Grate design: Von Roll reciprocating
Combustion temperature: 2500° F
Auxiliary fuel: Natural gas
Waste weight reduction: 65%
Annual Greenhouse Gas Production 600,000,000 Pounds CO2
CO2 per MWH 4480 pounds of total CO2 per Megawatt Hour:
1580 pounds of fossil CO2 / MWh plus,
2900 pounds of bio CO2 / MWh
BTU values:
Garbage = 4,800/pound
Coal = 12,000/pound
Plastic = 14,000/pound
Tires = 16,000/pound
The Friends Of The Earth worries about the waste of resources. The Following was taken from the website
Resource efficiency: Incineration wastes valuable resources such as metals, plastics, wood or biodegradable materials that could otherwise be salvaged through recycling. Every tonne of incinerated materials has to be extracted and processed again, increasing environmental damage and the European economy’s dependence on expensive imports. More energy is saved through recycling than is extracted by burning most waste
Climate change: Incineration produces greenhouse gas emissions – a typical incinerator converting waste to electricity produces around 33 percent more fossil fuel-derived carbon dioxide than a gas-fired power station. In contrast, recycling saves greenhouse gas emissions by avoiding the need to extract and process primary resources.
Jobs: Recycling creates jobs. Recycling 10,000 tonnes of waste creates up to 250 jobs, compared to 20 to 40 jobs if the waste is incinerated, and about 10 if it is landfilled.
Laura Haight, senior environmental associate at New York Public Interest Research Group (NYPIRG), says that if the petition passes, waste will take incentives away from more sustainable technologies like wind and solar. She also says that presenting the issue as though incineration offsets landfill emissions is the wrong approach.
“In framing this whole debate as incineration versus landfills, they’re pushing the needle back 20 years,” said Haight. “Twenty years ago, people used to say we need to do more recycling; now we’re talking about more burying or burning. No, we need to be doing more recycling.”
Haight points out that more energy is saved by reusing materials instead of destroying them. Also, rather than being burned, biomass could be composted and used for energy recovery, she said.
More information on waste to energy can be found here
Plastic to Energy
- Gasification – resulting in a gas (!)
- Pyrolysis – plastic to fuel
- Thermal depolymerization (TDP) – plastic to fuel
Burning Plastic On Open Fires
NB Burning plastic on open fires can release carcinogens and toxins…