Waste . . . zzzzt . . . Energy.
Waste disposal’s suddenly gotten sexy! Here’s the lowdown, with much thanks to waste-management-world.com.
Plasma arc gasification is a high-temperature process whereby the waste solids (a.k.a. carbon-based material, organic matter, shit, etc.) are superheated in the absence of oxygen and converted into a synthesis gas – syngas – that is mostly carbon monoxide and hydrogen. Leftover inorganic materials and minerals produce a vitrified slag. The required high temperature is created by an electric arc that converts a gas into a plasma. [FFS!] The reactor temperature is typically 4000°C – 7000°C (7200°F – 12,600°F). FFS.
FYI, the average surface temperature of the Sun is 5505 °C ( 9941 °F). Here’s what a plasma arc gasification plant looks like. It’s not so horrible.
Here’s the process.
Here’s the plasma arc gasification reactor/furnace. Not much to it, really.
Here’s the full plant.
You needn’t use syngas for electricity if you don’t want to. You can use chemical processes to extract elements and fuel compounds, or biochemical processes to extract fuels such as methane and ethanol. Let’s not forget the original Ford T could run on either gasoline or ethanol but the motor industry chose to go down the gasoline route. This wasn’t a good idea, in retrospect.
Main advantages of plasma technologies for waste treatment are:
- Thermally efficient
- Can process a variety of different solid wastes
- There is minimal pretreatment and presorting of solid wastes
- The syngas can be converted into other energy sources such as steam, electricity and/or liquid fuels
- There is environmental appeal as syngas can produce various energy products
- There are no toxic emissions. The extreme temperature of the plasma followed by quick cooling inhibits the formation of dioxins and other nasty stuff called furans.
- Unlike competing technologies including conventional incineration, there are no environmental issues regarding the disposal of slag.
- The slag can be be used to produce value-added products such as metals, construction aggregates and abrasives.
- It either minimises or eliminates the need for landfill.
- Existing landfills can be mined.
Here’s a comparison of plasma arc gasification with other technologies courtesy of waste-management-world. MSW stands for Municipal Solid Waste.
PAG delivers the most energy per tonne of MSW. Here’s a cost comparison.
PAG comes out on top.
What’s not to like?
- large initial investment costs relative to landfill and
- the plasma flame reduces the diameter of the sampler orifice over time, necessitating occasional maintenance.
- Some environmentalists say the ability to fully dispose of waste will discourage recycling and the development of renewable products.
I’m not sure what to make of the third disadvantage. If somebody makes themselves a business recycling rubber tyres into beach sandals or such then good for them.
PAG recycles compounds, molecules and atoms. I don’t think that’s a negative for this is what Our Universe does. It can’t be a bad thing. PAG is the closest we’ll get to throwing all our garbage down a black hole. If PAG does becomes incredibly inexpensive then goods handmade from recycled and reused goods and/or repurposed products will gain the status of value-added craft goods. They’re sort of going that way now. A 150,000 tonne/year PAG plant will employ 42 full-time operators. Let’s keep it real.
The second disadvantage can be discounted. A PAG plant is not clever enough to maintain itself and it’s unfair to expect it to. Here’s what a plasma torch looks like btw. The anode is good for 1,000 hours, the cathode 500. It’s the price one pays. No problem.
More to the point, if landfills worked perfectly nobody would even think of deconstructing waste into atoms. It’s the landfill thing that’s stopping PAG becoming more mainstream. Dumping stuff in a hole and forgetting about it isn’t without its problems. For an accurate comparison, we need to cost landfill to the stage where all toxicity has been removed and the land can be safely built upon or cultivated.
Despite these downers …
- As reported in a 2012 NY Times article, a PAG system at Hurlburt Field Air Force base in Florida processes 10 tons of garbage per day and produces sufficient energy to sustain the system. This is interesting because we now have a feel for how much energy it takes to fire up a torch to a temperature hotter than the Sun.
- Japan has three plants in operation: a 166 ton-per-day pilot plant in Yoshi, co-developed by Hitachi Metals Ltd. and Westinghouse Plasma Corp., which was certified after a demonstration period from 1999-’00;
- a 165-ton-per-day plant in Utashinai City, completed in 2002; and
- a 28 ton-per-day plant commissioned by the twin cities of Mihama and Mikata in 2002.
- Advanced Plasma Power has built a Gasplasma modular test facility in Faringdon, Oxfordshire, England.
- PlascoEnergy Group currently employs a plasma-arc waste demonstration plant in Ottawa, Canada, at the Trail Road Landfill. It processes 150,000 tonnes of municipal waste per year and produce 15MW of energy. Now we’re cooking! 10,000 tonnes of waste in = 1MW energy out.
- The USS George H.W. Bush (2003) aircraft carrier had serious problems with its gravity-driven collection holding and transfer (CHT) system for the handling of sewage. [Hmmm. Transfer to where? And when?] The next-generation Gerald R. Ford-class (2013) aircraft carriers have a vacuum system combined with a Plasma Arc Waste Destruction System. All combustible solid waste generated on board is blasted back into the Hadean Era when the 28 elements necessary for human life were just being formed.It’s nice to know the USS Gerald R. Ford won’t contaminate the ocean as it goes about its business. It’s essentially a closed system – a microcosm, a small city with its own energy source in the form of two nuclear reactors that can keep it at sea for 20 years if need be.That’s unlikely however as it’s home to 4,000 crew. That’s 2,000 less than its predecessor the USS Enterprise (1961) but 1,000 more than the USS Intrepid (1943) fabulously docked at Pier 66, NYC.The Intrepid’s kitchens used to shift 3.5 tons of food per day so the Gerald R. Ford must be processing approx. 4.6 tons per day. That’s a lot of organic matter whichever end you look at it. Today’s sailors hopefully get more fibre.
The onboard system is known as a PAWDS (for, Plasma Arc Waste Destruction System – what else?) and is manufactured by Pyrogenesis Canada. They’re on facebook. Check it out. You can find out interesting things like this. Note the military-friendly language linking winning the war on waste to winning wars.
We shouldn’t be surprised by such language. Everyone wants to flog their product to those who can pay the most. Frank Lloyd Wright tried to market his low-density Broadacre City to the US government as patriotic insurance against atomic attack. Mies van der Rohe wanted Hitler to adopt (his) Modern architecture as a symbol of a progressive regime, as Mussolini had done in Italy. It still happens today with architects trawling China, the Middle East and the former Soviet states for clients with deep pockets. It’s one of those facts of life.
The bigger problem I see with Pyrogenesis Canada talking the same language as the US Navy is that they have less incentive to make their system cheaper for non-military use.
The bottom line
Waste-management-world tells us the break-even point when income from electricity sales covers running costs is 180–270 tonnes waste/day (200–300 tons waste/day). Economy of scale matters. Pyrogenesis Canada also make a PAWDS for military land use. [Download the brochure.] It fits into five 20-foot containers and can process 400lbs (180kg) of MWS per hour. Sounds fab. It’ll easily sort out a medium-size apartment building generating the American average of 4.4lb (2kg) of waste per person per day.
Misfits would like to see one PAWDS per building. We’d also like it to include the energy recovery module that’s currently optional for the military.
Footnote: Here I’ve only mentioned what PAG can do for waste disposal. Not only does it destroy waste but it converts it into energy and other userful stuff. It can run off of existing landfill if we can be bothered. It can also help clean up our planet in other ways such as destroying refrigerants and the nasty fluorinated chemicals. That’s not a bad thing. PAG’s wonders never end. These things also eat chemical weapons for breakfast. Two mobile 20 foot containers can safely destroy up to two barrels of CWA per day. This is more than waste disposal, it’s the righting of wrongs.