Garbage In, Energy Out

Plasco Energy Group’s electricity-producing facilities set to transform waste disposal

By Dan Pelton | May 10, 2008

Ottawa-based Plasco Energy Group’s demonstration facility converts municipal waste into electricity, and other saleable by-products, through a process called plasma gasification.

When an announcement comes that there’s trash talk going on in Ottawa, the inevitable response is “Yeah, so what else is new?” This time, though, it’s not heated banter from the House of Commons.

Rather, the talk centres around privately owned Plasco Energy Group Inc. and its potentially game-changing method for dealing with two of the most pressing social problems of the day: the need for clean, renewable energy and an efficient, eco-friendly way to dispose of municipal waste.

At its demonstration facility in Ottawa, PlascoEnergy employs a process that holds the promise of converting everyday trash into electricity and saleable by-products with a minimum of environmental impact.

In January 2008, the facility was put through its initial test when City of Ottawa trucks dropped off approximately 20 tonnes of municipal solid waste. Now, as it reaches its full capacity, the facility is converting each tonne of waste it receives into 1.4 MWh of electricity, 300 litres of potable water, between 5 and 10 kilograms of commercial salt, 150 kilograms of construction aggregate and 5 kilograms of agricultural-grade sulfur used in fertilizer.

As sci-fi as that may sound, the facility is able to achieve these conversion rates through a unique application of the plasma gasification process, a relatively new technology that vaporizes waste to create a synthetic fuel used to power generators.

“One of the big advantages PlascoEnergy has over anything else I’ve done is that there is a world urgency about climate change,” says company president and CEO Rod Bryden. “Ours is the only system in the world that has been able to receive random municipal waste, which is highly variable in its content, and produce gas that is consistent in its energy content and is clean.”

It’s a big claim, but Bryden—best known as the owner of the Ottawa Senators hockey team—is no stranger to high tech or the eco-business. Initially, he made his fortune as the entrepreneurial force behind Systemhouse, a computer systems integrator. Later, he became one of the pioneers of paper recycling in Canada, when only about 15 percent of the packaging materials in Canada were recycled.

Now, he says, the combination of overflowing landfills, skyrocketing energy costs and growing concern over global warming has made solutions like plasma gasification an attractive proposition whose time has come.

“It is well recognized that methane is one of the major sources of CO2, and that the decay of municipal solid waste is one of the key sources of methane,” he says. “There is an urgency here that results in governments looking for ways to have new technologies become effective very soon.”

How It Works

While plasma gasification is relatively new, the basic concept behind it has been in use for more than 100 years. As early as 1850, it was used to produce “town gas” for light and heat. In fact, until the advent of natural gas supplies and transmission lines in the 1940s and ’50s, virtually all gas for fuel and light was manufactured from the gasification of coal.

Until recently, however, the materials used in the process were limited to combustible minerals, such as coal and biomass (organic waste). In the ’80s, however, that limitation was lifted with the widespread use of plasma torches, industrial cutters typically used in manufacturing.

Plasma torches work by sending a pressurized gas, such as nitrogen, argon or oxygen, through a small channel. A negatively charged electrode sends a spark through the channel, heating the gas until it becomes plasma, the fourth phase of matter. This directed plasma, at approximately 30,000˚F (16,649˚C), releases free electrons that break down the molecular structure of any matter it comes in contact with. The torch’s intense heat makes it possible for any material to be gasified to its elemental components.

Over the last 20 years, a handful of companies, including Startech, Geoplasma, PyroGenesis and EnviroArc, have been pursuing the Holy Grail of plasma gasification, with greater or lesser success, but they employ a similar process.

When municipal waste is delivered, high-value ferrous and non-ferrous metals are removed for recycling before the waste is chopped into small chunks. That processed material is then fed into a conversion chamber where it’s typically passed through the intense heat of the plasma torches.

Free electrons in the low-oxygen atmosphere of the chamber attack the chemical bonds of the solid waste and push the resultant mixture of gases into a plasma state where only the elemental components, largely carbon and hydrogen atoms, are left. As they cool, those elements reform into a mixture of hydrogen gas and carbon monoxide, a synthetic fuel called syngas, which is then burned to create the steam that powers turbine generators.

At the same time, any matter not volatilized by the plasma torches collects as a glassy obsidian material, which can then be processed to make aggregate for road or other types of construction material.

One of the most compelling aspects of these facilities is that they power themselves. Some portion of the electricity produced goes to power the facility; the rest is fed to the grid for sale to the local power authority.

Refining the Process

While the above seems straightforward, PlascoEnergy technical marketing manager Zakiah Kassam, P.Eng., says there are a number of problems associated with it.

“When the plasma torches are applied to the waste directly, you have to apply a lot of heat in order to completely break up that waste,” she says. “It is a very expensive process, and a lot of the facilities doing it that way are not economically viable because they are using up so much energy.”

PlascoEnergy’s future commercial facilities, such as this one designed by Canadian architect Douglas Cardinal and proposed to the City of Los Angeles, will process 200 tonnes of municipal waste per day and generate approximately 11 MW of electricity.

To overcome this and other problems, PlascoEnergy has improved upon standard plasma gasification by breaking it into a multi-step process that not only increases the generating efficiency of the facility but also limits its environmental impact.

One thing that makes PlascoEnergy’s system different, Bryden says, is that the actual waste gasification comprises a fraction of the overall process

“Out of the total investment of $30 million in the plant, the gasification part was only about 10 percent of that,” he says.

In fact, unlike other operations, the PlascoEnergy facility never applies the plasma torches directly to the waste itself. Instead, raw waste, once it has been separated and shredded, is transported to the core of the company’s innovative process, a three-chambered conversion vessel.

In the main gasification chamber, heat recycled from a later stage in the overall process vaporizes the matter at approximately 600˚C to 700˚C. The resultant crude syngas then rises into the refinement chamber where plasma torches push it into a plasma state. Since only the gas is being heated, and not the material waste itself, the torches don’t run as hot and, therefore, don’t consume as much electricity.

It also means that the overall process doesn’t need to run as hot as other gasification processes, which employ stainless steel containment vessels, or liners, that can wear out over time under the constant intense heat. By contrast, PlascoEnergy’s liner is composed of refractory brick.

“There is a heat element, but we are also taking advantage of the catalytic properties of the plasma torches that others haven’t or aren’t doing,” Kassam says. “So after the crude syngas passes through the plasma torches, what you are left with are simple molecules—things like hydrogen (H2), carbon monoxide (CO), hydrochloric acid (HCl) and hydrogen sulfide (H2S).”

At this point, the PlascoEnergy process overcomes another of the criticisms of leveled at traditional plasma gasification systems: as the plasma cools, it can reform into toxic substances if it’s allowed to combine with particulates and oxygen.

To prevent this, the refined syngas produced by PlascoEnergy’s system travels to the company’s Gas Quality Control System (GQCS), a cleaning and cooling chamber where a heat transfer system shuttles waste heat back to the initial conversion chamber. More importantly, the GQCS injects activated carbon into the syngas to capture any heavy metals and particulate matter. That potentially toxic material (approximately 1.3 kilograms) passes through its own cleaning system so it can be disposed of in a controlled manner, Kassam says.

The syngas, however, must go through a few more steps before it’s ready to power the facility’s electricity-producing engines. Its next step is the HCl scrubber.

“What comes out from the scrubber is sodium chloride or salt,” Kassam explains. “After that, the syngas moves through the Thiopaq System, which removes the H2S as sulphur, but its structure is hydrophilic so it is easily soluble in water and can be used for agricultural purposes.”

The other major by-product is the solid residue that isn’t volitalized during the initial solid waste gasification. This material falls into the system’s slag chamber. Like the gas refinement chamber above it, the slag chamber also utilizes a plasma torch to melt and stabilize the solids by driving off any remaining volatile compounds.

The result is a stable, glass-like and molten obsidian material, which is then poured into a water bath where rapid cooling creates small solid pellets valuable as construction aggregate for roads, concrete or other building materials.

“The majority of it is silica,” Kassam says. “There are some metals in that slag, but its final form is oxidized and completely stable within that structure. The standard leachability test we do for our regulatory requirements involves exposing that material to acid. We performed the same test on a glass soda bottle and it leached out more heavy metals than the slag did.”

It should be noted that the point of all this technology is as much about energy production as waste destruction. The real target of the process is to create a renewable energy source (syngas).

Once it has been refined and purified, the syngas is fed into internal combustion engines rather than burned to create steam. This fact, Bryden says, makes for a system twice as efficient as other gasification facilities.

To illustrate, Kassam adds, a typical steam cycle reaches about 20-percent efficiency whereas a gas engine will hit 40 percent. All told, she says the company’s facility consumes only 20 percent of the electricity it generates. The other 80 percent—approximately 1.1 MWh in the test facility and 1.4 MWh-per-tonne of waste in the future commercial facilities—is available for export to the grid.

“A total of 68,000 tonnes per year, on the uptime of our system, will run a fully efficient commercial plant and achieve these conversion efficiencies,” Bryden explains. In other words, even smaller municipalities, with populations in the range of 100,000, could produce enough waste to run such a plant at top efficiency, providing both commercial and household waste were brought in.

Richard Urbanski, senior air and waste specialist for SENES Consultants Ltd., says that at same time that PlascoEnergy has maximized the efficiency of its facilities it has also strived to minimize their environmental impact. “From what I’ve seen, they are investing an immense amount of effort and resources to ensure everything is done appropriately,” he says. “In fact, PlascoEnergy has negotiated operational limits with the Ministry of Environment that are well more stringent than the maximum limits prescribed for other kinds of ‘energy from waste’ facilities.”

A Sustainable Future

At present, the company’s Ottawa demonstration facility is ramping up to the 85-tonne-per-day capacity limit set by the city during its initial testing phase. When the company goes into full production of commercial facilities in the next year, they will be manufactured in 100-tonne-per-day modules that can be assembled into 200- or 400-tonne-per-day facilities.

These expanded facilities will take up approximately four or six acres respectively and incorporate an additional mechanism for capturing waste heat to power steam generators. Kassam says, at full capacity, the 200-tonne-per-day commercial plants will produce a net power generation of approximately 11 MW.

“We completely finance our business model,” she says. “We build, own, operate and construct these facilities so there is no financial risk to the municipality at all.”

Kassam adds that, once in operation, PlascoEnergy will make revenues both from electricity sold to the local or provincial power authority and from the industry-standard tipping fees cities presently pay landfills to take municipal waste. “The tipping fee depends on the power price we get,” she says. “We have certain revenue targets we need to achieve per tonne, so at a power price of about 11 cents per kilowatt hour, for example, the tipping fee would be 65 dollars per tonne.”

The company currently has letters of understanding with Red Deer, Alta., and Ottawa but also has proposals before several other cities in Canada and the U.S., including Los Angeles.

“Our corporate philosophy is very different from anything that I’ve ever seen before,” says Kassam, who spent six years as a design engineer for the oil and gas industry in Calgary. “Our belief is that this system should be something that can go into a community and be an asset to them. The measures we take, like treating water to a potable quality standard, the environmental quality controls we put on the system and the continuous emissions monitoring, even when it isn’t required, those kinds of actions are part of our environmental ethic to keep pushing the limits and putting the best that’s available into our system.”
www.plascoenergygroup.com

Dan Pelton (dan.pelton at yahoo.ca) is a Guelph, Ontario-based freelance writer.