The X-tremophiles: Supercharging Organic Waste Digestion

A newly commercialised technology is exploiting the 'super powers' of extremophile organisms to digest organic materials in a variety of waste streams at 2 per tonne.

Deep sea diving: The extremophiles were harvested several years ago from underwater volcanoes Disposing of waste is becoming a major expense for businesses. In many countries landfilling is increasingly expensive due to taxation, while gate fees at energy recovery facilties can be costly. However, a newly commercialised technology that exploits the 'super powers' of extremophile organisms offers the potential to cut that to £2 per tonne. And it hasn't gone unnoticed.

By Ben Messenger

Until six or seven years ago, Bath, UK based biotech firm, Advetec was largely involved with the biological treatment of wastewater. It had developed different strains of nutrients for nurturing various species of bacteria in different liquid effluents - and that was the company's focus. But that all changed when a client asked it to look at a solids issue it was having with an in-vessel composter.

"One of our clients had bought this machine but it wouldn't get rid of all the different types of food waste that they were throwing in - a very varied mix with lots of grease, fats, oils, vegetable material, meats - everything," Craig Shaw, the company's founder and CEO tells WMW. “Our primary business was in dealing with organic loads in wastewater and what we developed as a company were biostimulants,” he elaborates.

Because of Advetec's understanding of microbial activity, and what gets microbes to work much faster, the company soon came to the conclusion that the machine would work just fine - if it processed half a load at a time.

"You're putting all these different things in and it's causing a bit of a caustic cocktail for the bacteria and they're not flourishing. They never will do the way that it's designed. It was designed to do green waste or 'off the plate waste', but not both at the same time'," he adds.

The Bio Thermic Digester

The company did a lot of development on its client's in-vessel composting machine and quickly realised that thermophilic bacteria - composting bacteria - wouldn't do. According to Shaw, while these bacteria do work, the process is slow, and if you're producing hundreds of tonnes of waste you need something that's fast.

"We asked what type of bacteria would eat all of this organic waste and clean up the in-organic waste, all in one machine?" he explains. "Well, there's a thing out there called extremophiles - bacteria that live in temperatures way above 100°C all the way up to 1000°C."

"We harvested our extremophiles several years ago," he adds. "Our background is that we're a deep sea exploration company, so we got the extremophiles from underwater volcanos."

The company used these organisms from the deep and applied them to the concept of in-vessel composting. In doing so it created a chamber where it could control the environment so that extremophiles flourished. And because they flourished, the bulk of the organic material that entered the chamber became their food.

"What we did is create an in-vessel composter on steroids, with a starting temperature of about 140°C to 150°C and a finishing temperature of anything up to 300°C to 325°C. We were then able to take large quantities of organic material and very rapidly reduce it down to its minimum consistency. That's what the Bio Thermic Digester is," he explains.

Development

"We were asked to reengineer this machine by our client, which we did - extremely successfully," says Shaw. “We then tried to sell our enhanced technology back to the manufacturer of the machine, which turned it down flat."

But that wasn't to be the end of Advetec's extremophiles and the Bio Thermic Digester (BTD) technology they made possible.

"We realised very quickly that there were a lot of our clients that have large volumes of organic waste. It can't go to AD because it's got mixed waste in there and bits of packaging and plastics and aluminium foil - or things that it shouldn't," continues Shaw.

So the company kept working on its BTD and honing the cocktail of microbes at its heart – as well as the mechanical requirements for them to not only survive, but thrive.

"It's all about keeping the bacteria in peak performance," says Shaw. "We have to inject the bacteria because they don't live naturally. They're our proprietary blend and we replicate them from core spores. We also know exactly how to feed them so that they eat through things as fast as possible."

"It means you can take black bag waste, shred it up and put it all through our machine, plastics, wood, metal, glass - everything just goes through the machine as one mix," he continues.

With the ability to prcess waste on-site at around £2 per tonne, the BTD technology has attracted considerable attention from across the globe

"What the machine does is it takes out all the organics and it reduces the moisture down to less than 8%, which for anybody dealing with mixed trash gives readymade RDF at the end of the process. There's nothing to put into landfill because the organics that would go to landfill have gone. You've got a machine that makes RDF from municipal waste," he adds.

Multiple capabilities

One of the benefits of the technology eulogised by Shaw is its ability to process a wide variety of waste streams. It can do this because extremophiles are not one species, but many. And like any team of superheroes each have their own special powers – of digestion. When it comes to how the various species of microbes are blended together, Shaw uses an analogy:

"You might like apples and I might like bananas. The situation is that different types of bacteria have different favourite foods. When you have an organic waste material there's two things you have to do. First of all find out which of the extremophiles like to eat it. Then you've got to think about what you put with them to have a healthy diet so that they're like an athlete rather than a couch potato.

"We make all those blends and those specific nutrients to make that work. That's why our BTD can deal with sewage sludge, food waste, black bag waste, organic waste from a food processor, raw peelings and fats, greases and oils. We just need to know what waste needs to be got rid of and we can customise it."

Following a number of trials around the world, the company says that the technology is now ready for commercial deployment. The system is modular, with the biggest machine able to process 50 tonnes per day.

"You put 50 tonnes of waste in at the front end every single day. It's not a batch process like most composting; it's a constant feed. You have to feed it seven days a week, 365 days per year," explains Shaw. “Once you've got the machine running it's extremely efficient because one of the beauties of extremophiles is that a lot of the organic material is turned into water, but it's also turned into heat. That's their by-products.

"We utilise that heat in a heat recirculation system in the machine, which means that once we've got it up to temperature we have minimal electrical costs," he continues. "Typically for a 50 tonne machine to process one metric tonne of municipal waste would cost around £1.50 to £2 in operating costs because the energy that's being produced from the biomass is being reutilised to sustain the 200°C to 300°C environment for the extremophiles."

The CEO adds that for the first 72 hours of operation the BTD units require around 30 to 60 kWh of electricity per day to get up to temperature. The only outputs from the machine are said to be distilled water, heat, a waste derived fuel and a small amount of digestate that even the extremophiles can't eat.

Shaw describes this as the "burnt toast" that the organisms have merely "nibbled at".

"It's the hardest part of the carbon within the food chain. It's a really dark brown material that looks like coffee grinds. It's organic in nature but only 3% to 5% of what went in. The digestate produced by AD is typically 70% of what went in."

Because a lot of the organic feedstock, and the by-product from the extremophiles, is H2O, the extreme temperatures generated create a lot of steam. The system condenses out the moisture from this steam and uses the dry heat in the process. Because of this there is a lot of condensate – water.

"We've just done two big installations at food factories in the Middle East and their primary concern is getting the water back for process as they use a lot of water for cleaning etc. By recuperating the water alone the machine will pay for itself in about 18 months, without counting the savings in disposal costs for the organic material," says Shaw.

He adds that a typical 50 tonne machine can produce as much as 30 to 40 tonnes of distilled water per day.

Complementing AD

According to Shaw, the sytem is capable of treating such a wide variety of wastes that even digestate from AD can be processed - reducing its volume by a further 80% in 72 hours.

"Extremophiles feed on matter that the thermophiles couldn't. We can be an add-on process to biogas plants, meaning that their operating costs are minimised because they've got less to dispose of," he says. "We don't see AD as our competition at all."

Shaw claims that if the quality of the digestate from the AD plant is not good enough to go to land, and disposal costs have to be met, then putting a BTD in at the end of the process can pay for itself in less than a year.

Commercial success

Because of the rate at which the BTD is able to process waste, Shaw says that the company has had a lot of interest and has developed numerous pilot projects across the globe.

Among the initial trialists was East London based Regional Waste Recycling (RWR), which collects the majority of the liquid waste generated within the M25 (London's 190km long ring road) and treats over 300,000 litres of gully, septic tank, flood and industrially contaminated water, as well as 150 tonnes of municipal waste daily.

Following the trial Advetec has now secured an order from RWR to supply and install an industrial scale BTD which will process up to 33 tonnes of organic waste every 72 hours.

"The smaller machine was regularly turning over 90% of organic waste into clean water and dry powder, so we're confident that the new, larger machine will cope with the huge volumes of solid sludge/organic waste we receive every day," comments John Edwards, director of RWR.

Advetec has also had a number of successful installations at U.S. wastewater treatment plants, as well as at food processors and retailers. Shaw explains that while in many cases sewage sludge does does make good fertiliser, there are now pharmaceuticals making their way through the wastewater that are left in the residue.

"You've also got the issue of heavy metals concentrations rising in certain population centres, which means the sludge from large utilities has to go to landfill because it's contaminated," he says.

In such instances Advetec is installing BTDs to process the organics and reduce the volume by 90% to 95% - and cutting disposal costs accordingly. According to Shaw the machine was the first in the U.S. to receive a DEP permit and is now accredited in Florida, Pennsylvania, California, Washington, New York and Michigan. "It's snowballing over there," he says.

The Future

The company currently has 17 BTDs in service, but according to Shaw interest is rapidly growing, and a further 47 machines are on order for delivery over the next two years.

"Our first really big orders started coming in from the U.S. in August last year, and then the Middle East. From there it took off," he says. "Today we have enquiries coming in from China, India, Belgium and Germany."

It may be early days for Advetec's BTD technology, but with the help of their superheros from the deep, it seems to have got off to an extremely good start.

Ben Messenger is managing editor of WMW
e-mail: benm@pennwell.com