Plasma gasification has become a buzzword and the new kid on the waste to energy block. One company has trialled its new process in Mexico, known as microwave plasma gasification, and is starting work on its first commercial facility in Texas. Tom Freyberg investigates claims that the process is 60% more efficient and can produce diesel from waste.

With landfill sites reaching capacity around the world, more and more municipalities are incorporating waste to energy (WtE) technologies into their waste management plans. Political and planning challenges to one side, modern technologies have proven their ability to produce energy or a valuable biogas/synthetic gas (syngas) from waste and divert millions of tonnes from reaching landfill.

Many WtE processes such as mass burn have been in use for decades, but have been refined over the years to their current state today. But it is pyrolysis/gasification currently grabbing the headlines, especially plasma arc gasification.

In short, the latter involves processing organic waste at extreme temperatures (4000ºC – 7000ºC) using an electric arc in a torch to produce a syngas and vitrified slag, a rock-like glassy by-product. Developing across Europe quickly, companies such as UK-headquartered Advanced Plasma Power (APP) has already formed a joint venture to gasify thousands of tonnes of waste unearthed from a landfill mining project in Belgium.

Even across the pond, the North American market is one where companies are also trying to rapidly establish a foothold in the enormous waste market. And it’s clear to see why. Figures from the Environmental Protection Agency (EPA) show that in 2009 Americans generated 219 million tonnes of waste. Of this amount, 74 million tonnes were recycled, resulting in a 33.8% recycling rate. A total of 26 million tonnes were used for energy recovery (11.9%). Interestingly, around 31 million tonnes were sent for thermal processing back in 2000. So, over the period of nine years the amount of waste sent for WtE processing decreased by five million tonnes.

This raises the question of whether plasma gasification could help spearhead a revitalisation of waste to energy across the continent? And developments to date suggest this could be the case.

Plasma gasification progress in the U.S.

To kick this technology off in the region, Geoplasma, part of real estate developer Jacoby Group, has secured a permit from Florida’s Department of Environmental Protection to build the St. Lucie Plasma Gasification Facility in St. Lucie County, worth an investment of $140-150 million. The facility is set to produce 24 MW (gross) of power from nearly 600 tonnes of waste and tyres per day.

Speaking to Waste Management World magazine (WMW), Geoplasma president Hilburn Hillestad says the firm intends to break ground on the project in January 2012, with an 18-month construction period meaning the project will be ready by mid 2013. Technology will be provided by Westinghouse Plasma Corporation, subsidiary of Alter NRG.

Results from Waste2Energy’s pilot plant show 10-20% of energy recovered can power the microwaves

Moving south into Central America, it is new venture Plasma2Energy making headway, using a trial in Mexico as a springboard into the rest of America. The pilot plant in Monterrey, Mexico is processing 10 tonnes of waste per day (3,600 tonnes per year), established in early 2007.

The company is in final negotiations for an agreement with the City of McAllen in Texas, for a 180,000 tonnes per year facility worth $117 million, to process all residential, commercial and green waste generated within the city. It is also set to recover over 1500 tonnes of recyclables over the course of the year. Currently in negotiation with the city municipality, the company says a long-term contract between 20-25 years will be established.

“The first phase of the McAllen project will take 18 months and then another 24 months for phase two, so it will be three and a half years before we start taking waste from the municipality,” Rodolfo Sanchez, CEO of Plasma2Energy™ tells WMW. “The city produces 450 tonnes of waste per day and after separation and moisture content we will need to gasify around nearly 300 tonnes of waste per day and generate 27 MW of electricity net to the grid.”

Microwave plasma gasification

As the technology distributor, Plasma2Energy uses ABA’s technology, which the company is keen to position as “microwave plasma gasification”. According to the company’s literature: “By harnessing the power of microwave radiation through a patented plasmatron array in the reactor, waste feedstocks and other carbonic materials are heated until they are heavily ionized, forming a cloud of plasma in the material.”

Waste feedstocks and other carbonic materials are heated until they are heavily ionized, forming a cloud of plasma

Heated water vapour is then added to the plasma to create a syngas and inert slag. Produced gas can then be purified and some of it “re-fed” through the reactor, to recover energy and provide enough energy to power the microwaves. In Layman’s Terms, this means the process could be self sufficient.

Plasma2Energy says the microwave technology is where efficiencies can be made. And the question of whether the technology is a giant version of household microwaves used to heat up soup is not as ridiculous as you might think!

“Yes, it is effectively giant microwaves that use heat to ionise the waste,” Sanchez says. “Other processes out there, such as electric plasma arc torch processes, consume almost 80% of the energy they generate. In comparison, the ABA process consumes only 20% of the recovered energy.”

The CEO is keen to stamp out any accusations about company brochures being notorious for self-promotional, exaggerated claims.

“We generate heat by breaking the molecules until they get ionised so we can form the plasma,” he says. “The energy that we use on those microwaves to produce the gas needed is much less than the energy produced from the syngas. Results from our pilot plant in Mexico show that we need 10-20% of energy recovered to power the microwaves.”

The million dollar question to any small start up keen to take on larger, established companies is how does the process differ from the competition? And more importantly, how is this different to plasma arc gasification?

“What we have seen is that with plasma arc and plasma torch processes, you have several torches in the gasifier. They apply the energy to a single point whereas in the case of microwaves, you have a whole area where you’re applying the heat. We actually generate the plasma at the very beginning when the matter enters the microwaves. Energy is applied directly to the matter to form a vortex, helping the heat reach a plasma state and subsequent reaction afterwards.”

Black gold? Plasma rock and diesel

While organic processes are combusted and eventually transformed into a syngas, other materials such as metals, glass and minerals are not gasifiable, but are melted into an inert slag residue. Already established as a recyclable by-product, many waste to energy companies are branding the vitrified recyclate to help with marketing. An example of which is APP’s “Plasmarok”, which it says can be used as a building material or replacement aggregate.

For Sanchez, he says that variations in the feedstock play a big part in the quality, and quantity, of the plasma by-product from the Plasma2Energy process. “In Texas we’re going to have a moulding machine underneath the reactor so we can form bricks,” he says. “It is very light and can take the form of whatever you put it in and cool it. The slag itself is inert and we have a market – construction and the product even has a quality suitable for homes and gardens.

“The most important thing is that the volume of the slag depends on the feedstock. If you separate metals at the beginning, which is what we are planning to do, you have a more efficient process as you don’t have to use the energy to heat the metals. You can recover more energy.”

Plasma2Energy’s proposed $117m facility would process 180,000 tonnes per year of waste in Texas

Another important process by-product in need of discussion; in fact of more significance (and value) than the glassy rock recyclate, is that of the diesel produced. As part of the process, the firm says that clean gas can be processed through a Fischer-Tropsch reaction stage, where part of the synthetic gas condensates into a liquid. This can then be refined to produce biofuels, ethanol as well as ammonium nitrate as a biofertiliser. “The oil that we have collected from the pilot plant comprises 70% diesel,” the CEO quips. “When we are cooling and cleaning the gas, some parts are condensed into synthetic oils. The process can be refined to this set up and whatever you don’t need you put add back to the process for gasification.”

On the topic of how the proposed process will fit in with established recycling efforts in the region, Sanchez says: “We have made the commitment with the City of McAllen that recycling will be priority number one,” says Sanchez. “At households waste is being separated into two different bins – one goes to recycling centres where they separate metals, paper and cardboard. That will continue until we get into the second phase and then we will implement what the city wants to do with the recycling.”

Spreading the word

Moving beyond Texas, the CEO – an engineer by trade – says the patented technological research into plasma gasification took a mighty 17 years to reach market, eventually published by the World Intellectual Property Organization (WIPO) in 2009. Plasma2Energy can now apply for a certificate of patent in the 160 countries that belong to WIPO, with Sanchez admitting his company has an application pending for certification of patent in the United Sates and the European Union.

Plasma is generated at the start when waste enters the microwave

“We have received requests from all over the world and we have a list of project developers identified and ready to specify our technology. We have received several requests from the UK, Italy, Spain, France, Switzerland, Asia, South America and Africa.”

The waste sector, more than others, is known for its slow uptake of new technologies that have yet to be commercially proven. In fact, the expression “the proof of the pudding is in the eating” is frequently cited at conferences discussing new technologies and trials.

Sanchez admits he is facing similar challenges with interested companies requesting data from the Texas facility. Until this facility comes online to produce needed data and the waste agreement with the City of McAllen finalised, Plasma2Energy could find it a challenge to roll out a second full-scale facility.

But, with claims that microwave plasma gasification is 60% more efficient than existing processes, and the ability to produce 70% diesel as a by-product; the ABA process really could be game-changer on the WtE landscape.

Watch this space: microwaves could soon be used for a lot more than heating up your lunchtime soup.

Tom Freyberg is the chief editor of WMW World magazine. email tomf@pennwell.com

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