Gasification

Gasification heats the waste with little or no oxygen in order to produce a chemical reaction. The waste does not burn rather the chemical reaction produces synthetic gases.

These can be burned to turn a turbine, which spins a generator and creates electricity.

As yet gasification technologies have ‘to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning.”

Plastic can be regasified (?) along with all sorts of other products.

Incineration

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.

The Process of Incineration

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.

Emmisions (Copied from Slate)

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, aspart 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

Burning Plastic On Open Fires 

NB Burning plastic on open fires can release carcinogens and toxins…

post

Oil from plastic…

Don’t throw those sweet wrappers away you may need them to run your car. They can be turned into oil by

  • Thermal depolymerization (TDP) or
  • Pyrolysis System.

Thermal Depolymerization 

is the thermal decomposition of organic compounds when heated to high temperatures in the presence of water. Organic compounds can mean anything from pig poop to plastic.

How it works….

Feedstock materials are first ground into small pieces and mixed with water. The mixture is then heated to 482°F (250°C) for approximately 15 minutes in a pressure vessel. The steam generated raises the pressure in the vessel to approximately 600 pounds per square inch (PSI) which, at the end of the heating process, is rapidly released. This causes the water to flash off or rapidly evaporate, thus leaving residual solids and crude hydrocarbons behind.

These constituents are separated and the hydrocarbons collected for further refinement. This involves further thermal treatment to 930°F (500°C) and fractional distillation sorting. The results are light and heavy naphthas, kerosene, and gas oil fractions which are suitable for the production of several grades of fuel oil. The residual solids remaining after the initial thermal treatment may be used as fertilizers, filters, soil fuels, and activated carbon for wastewater treatment. Wise Geek

It can be used in the recovery of PET, polyamides (except Nylon), and polyurethanes (except Styrofoam).

It mimics the natural geological processes thought to be involved in the production of fossil fuels. Under pressure and heat, the long chain polymers are broken down into short-chain petroleum hydrocarbons.

With thanks toWikipedia and Green Manufacturing 

Average TDP Feedstock Outputs[8]
Feedstock Oils Gases Solids (mostly carbon based) Water (Steam)
Plastic bottles 70% 16% 6% 8%
Medical waste 65% 10% 5% 20%
Tires 44% 10% 42% 4%
Turkey offal 39% 6% 5% 50%
Sewage sludge 26% 9% 8% 57%
Paper (cellulose) 8% 48% 24% 20%

(Note: Paper/cellulose contains at least 1% minerals, which was probably grouped under carbon solids.) Wikipedia

Pyrolysis

This company, Cynar,  use pyrolysis to turn plastic into oil. Here’s what they have to say on the subject

Suitable end of life plastics are preprocessed to size reduce and remove any contaminants or non-plastic materials from the feedstock at the first stage of the Cynar Technology. The shredded plastics and are then loaded via a hot melt in-feed system directly into main pyrolysis chambers. Agitation commences to even the temperature and homogenise the feedstocks. Pyrolysis then commences and the plastic becomes a vapour. Non-plastic materials fall to the bottom of the chamber.

The vapour from the chambers passes into the contactor which knocks back the long chained carbons and allows the required condensable vapours to pass into the distillation column. The system diverts the non-condensable synthetic gas through a scrubber and then back into the furnaces to heat the pyrolysis chambers. The condensable vapours are converted in the distillation column to produce lite oil and raw diesel. The lite oil is put into storage. The raw diesel is passed to the vacuum distillation column to be further refined to produce diesel, kerosene and lite oil; the distillates then pass into the recovery tanks.

The pyrolysis system is the prime chamber, which performs the essential functions of homogenisation and controlled decomposition in a single process. The Cynar Technology process requires minimal maintenance and produces a consistent quality distillate from end of life plastic.

Taken from the website

Wikkipedia has this to say on the subject.

Anhydrous pyrolysis can also be used to produce liquid fuel similar to diesel from plastic waste, with a higher cetane value and lower sulphur content than traditional diesel.[15] Using pyrolysis to extract fuel from end-of-life plastic is a second-best option after recycling, is environmentally preferable to landfill, and can help reduce dependency on foreign fossil fuels and geo-extraction.[16] Pilot Jeremy Roswell plans to make the first flight from Sydney to London using diesel fuel from recycled plastic waste manufactured by Cynar PLC.

Japan

Blest Technology based in Japan will sell you a machine to do it yourself at home .As the process sounds exactly like the one above  I am guessing it’s a pyrolysis based system.

Recyclable plastics are polypropylene (PP), polyethylene (PE) and polystyrene (PS). They cannot recycle PET.

“Teaching this at schools is the most important work that I do,” Ito reflects. In Japan too, he visits schools where he shows children, teachers and parents how to convert the packaging and drinking straws leftover from lunch.

If we were to use only the world’s plastic waste rather than oil from oil fields, CO2 emissions could be slashed dramatically, he says.

“It’s a waste isn’t it?” Ito asks. “This plastic is every where in the world, and everyone throws it away.” quoted here

“The carbon-negative system  is a highly-efficient technology, converting 1 kilogram (about 2 lbs.) of plastic into 1 liter (about a quart) of oil using just 1 kilowatt of power (cost: about .20 cents).

Of course, the end product of this conversion system is still fuel that must be burned, and thus, it will give off CO2 as part of the combustion process.  Read more here

Ocean Ambassadors promote its use.

It is in operation in over 80 countries worldwide, and has a processing capability of up to 20 tons a day.There are pilot projects in works from various universities as well as the UNDP.

We advocate and educate on this technology as a solution to island nations as it provides a real-time solution to effectively processing these “waste materials” locally and providing an end product that has a high demand in all locations.

As it is a low-sulfur burning content fuel and recorded as environmentally friendlier than standard diesel, we feel this technology offers us an option for the time being before we phase into plastic alternatives that are bio-based.

Homemade

Or you can build your own machine in your back yard like this guy!

 

Projects that look interesting

The Waste Combuster

Plastic is first processed in an upper tank, which converts the material into gas through a process called pyrolysis. Then, the gas moves to the lower tank, where it’s burned with oxidants. That burning generates heat and steam, which drive combustion and generate electric power. While other waste-to-fuel generators have been developed, Levendis says his machine has the added bonus of not producing harmful emissions.

The waste combustor is currently still in prototype phase, but Levendis is dreaming big: Eventually, he envisions scaling up this concept to juice a large power plant. A connected plastic recycling center could provide a constant stream of fuel.

India

Heres a plant in India thats transforming plastic into motorbike fuel  They say of the process that it “converts all sorts of waste plastic into fuel oil, petroleum gas and solid petroleum coke. It can work with all kinds of plastic waste, and doesn’t need the waste to be cleaned first. A fractional residue containing metals is the only possibly harmful by-product.”

Pretty sure that is thermal depolymerization

Talking of which .. I got this comment to one of my posts

If there is anybody who seriously wants an eco-friendly disposal system for used plastics, please contact me for this existing zero percent emission process technology that converts plastics into EN590 Diesel – ready for use in vehicles and other uses such as power generation.

Contact:  Mr. Anvi Arcilla

E-Mail: anvi@greenerpowersolutions.com

America

And the yanks are doing it too. This company in America are setting up a business that they hope will turn a profit in 15 months

More

Other ways to recycle plastic can be found here

And more ways to dispose of plastic here