A system that generates energy from rubbish is being sent by defence firm Qinetiq to the US army.
The PyTEC system heats mixed waste, releasing a gas that can be burned to produce five times more energy than is required to drive the system.
Qinetiq say that the system, already in use on British navy ship HMS Ocean, has been "containerised" for US army use.
The approach could see use in urban areas, reducing municipal waste volume by 95% while producing energy.
The process hinges on pyrolysis, in which waste subjected to high temperatures releases combustible gases.
In essence it is the same process that happens above a match; heating of the wood releases gases that burn in the presence of oxygen, producing the visible flame.
In pyrolysis, the heating occurs in the absence of oxygen, and the released gases are gathered and stored for later use.
"We're reducing their logistical footprint, reducing the number of body bags, and reducing their fossil fuel usage"
This is in contrast to simple incineration or gasification - another energy-from-waste approach that heats particular kinds of waste in the presence of oxygen to create combustible gases.
Typically, such systems require that the waste be of a singular type, and diced up before entering the gasification chamber.
In the PyTEC system, a large screw-shaped column takes in up to 100kg per hour of untreated mixed waste - including glass and tin, particularly troublesome waste sources for thermal waste approaches.
The waste is heated, releasing gases that are removed and used to power a steam turbine.
What exits the system is a glassy substance just 5% the volume of the waste that entered, along with 400kW of power.
A similar system was installed on the UK navy ship HMS Ocean late last year.
There are already (a few) sludge incinerators at wastewater treatment plants in the US that generate electricity from sewage sludge. And trash incinerators that burn mixed household waste. Environmental concerns pretty much stopped construction of new trash incinerators in the US.
I doubt if it is economically competitive if all of the environmental control issues are added in.
In Europe it would have to meet the Waste Incineration Directive. This imposes relatively low limits for NOx, CO etc. The cleanup can be large and costly to purchase and operate.
There are some commercial scale gasification plants being developed in Europe, but the tend to be fairly large - 10MW or so. This is because of the size of plant required to handle say 100,000 tonnes of waste a year.
I'm worried about the reference to body bags..... just what are they intending to put in there?
I think that's not what it is (incinerators)! I have seen methane produced from landfills and used in generating power with gas-fed engines. I don't know if those are economically feasible but it works.
The issue on ships is the space it would take to store the waste, or the enviromental impact to deep six the waste. That seems more likely why it would be good on a ship.
But on land, what is the incentive? Waste reduction, or cost recovery?
Land fill gas is a nice idea to use developed methane, although cost is a concern. And it looks like the equipment life of around 15 years might just match the production time of the land fill. But this isen't the same as the orignal concept, or is it?
Only disposing municipal waste is not feasible.If you dispose industrial waste and produce electricty with steam turbine, it is feasible together.I was working mass gasification plant in Turkey.Waste inciniration is more common than gasification.
With Pyrolysis, there would be no ash since combustion did not take place. You are left with carbon black, which can be used
for filters, ink, pigment, etc. I worked at a facility in the early 90's that had 2 such machines. We processed all plastics, tires, and municipal waste. Our end products were a heavy oil, light oil (approx 90% benzene), carbon black, and the non condensible gas was basically natural gas which would become the fuel to feed our burners. The additional gas that was produced went to a flare which ran at 1400 deg. F. When processing tires, we could also recover the fiberglass and steel with the use of a magnetic separator and a centrifuge.
Most of these systems have been around for years. But few can stand alone on economics. Natural gas is cheap and clean and unless there is some other factor, such as someone heavily subsidising the overall installation and operating costs, it is a sure way to burn money.
these plants make money with high profit.Because, disposing prices are too hight, especially for industrial wastes.Because, number of plants are fewer in world.Surely, nstallation cotst are high , but it can amortize in short term.If you combine these plants with steam turbine, you dont only install a waste plant , you also install a power plant and can sell it to grid.
They all produce C02 and would be subject to any carbon tax. They also have a waste product. Fluidised beds was supposed to be the salvation for garbage burning, but it has not really worked out. Recycling is a better option.
Burning waste products works when you can incorporate it into another process like petroleum coke or sugar cane waste. Still have a CO 2 problem.
