Advetec has applied its knowledge of microbes to the waste sector, developing a technology that rapidly consumes organic waste.
Craig Shaw, Advetec’s chief executive, spent 30 years as a marine biologist, a rather unusual background for someone working in waste: “I used to do a lot of work on underwater volcanoes and collecting bacterial cultures, minerals and nutrients for pharmaceutical companies.”
The knowledge he gained led to the development of the company’s Bio-Thermic Digester (BTD), a machine designed to reduce volumes of organic waste quickly. It can be applied to pure organic streams, such as sewage sludge or sludge from anaerobic digesters, or waste streams with high levels of organic content such as packaged food or that from municipal black bags.
It is built on the concept of reducing waste volumes, to save haulage and disposal costs.
According to Shaw, the digester can reduce volumes of waste by 96% over three days. It does this by using extremophilic bacteria which naturally - and rapidly - break down organic waste. Shaw describes it as “like a composting machine, but on steroids”.
He explains that most composting technology uses thermophilic bacteria that live in temperatures from 50-70°C. The BTD uses bacteria that live in much higher temperatures.
This is where Shaw’s previous experience came into play: “I said that we need to use extremophiles, which live on the outer rims of underwater volcanoes, are aerobic and feed on organic material which has been deposited. They eat it fast because they are living in temperatures of 190-200°C.”
He approached some of the people he used to work for, seeking out bacteria that would live at 150-220°C: “We worked backwards and found the workers that would do the job. Then we just had to create the environment, the optimum conditions for them to survive. Then you throw anything in and it gets eaten.”
Essentially, waste is put in at the front end of the enclosed system, the bacteria eat the organic fraction in an aerobic process, and they leave a largely ‘clean’ and dry mixture of non-organic matter, such as glass, plastics and metals, depending on the infeed. It is a continuous process, so the machine needs loading only once a day, and does not need staffing or to be run by a waste specialist.
Shaw explains that the output can then be mechanically sorted, a task that is much easier once the ‘gooey’ organic fraction has been removed. Dependent on the waste being fed into the front end of the process, the output can also be used as a refuse-derived fuel for the cement industry or biomass plants because it has a moisture content of less than 10%.
The organic matter can be composted for fertiliser. And for machines processing pure organic material, the undigested organic soil material that comes out (4-5%) can be used for biomass fuel, with a calorific value of 18-22kJ/kg compared with coal at 32kJ/kg.
Advetec is currently doing some consultative work with pyro-forming technology firms because the BTD removes the fraction they do not want in their processes.
Shaw says: “What comes out is very dry and is not smelly - it is an inert substance because is free from pathogens. It allows [clients] to either resell it or reuse it.
“We are looking at projects for two large companies in London who deal with lots of broken glass which is contaminated with organics. They are putting the broken glass through our machines with the organics - we are removing the organics and the moisture and giving them glass that is ready for recycling.”
The company recently installed an industrial-sized BTD at a waste transfer station in London, which has been approved by the Environment Agency and meets its emissions and monitoring requirements.
But its biggest market is the US, where it has been approved by the Department of Environmental Protection, and countries such as Mexico, Bolivia, Paraguay and Columbia. These are mainly processing municipal black bag waste. With black bags containing 30-50% organics, metals, plastics, wood, paper and so on, clients are shredding or putting mixed waste through a trommel and then through its BTD process to remove the organic fraction.
Of the US sales pipeline, a significant number are for waste management companies.
Shaw says: “The reason is that my machine is about the same size and pricing as a truck. Clients can still be charged for the tonnage they produce but, instead of hauling it and paying the disposal cost at landfill, waste firms put one of my machines in at the back of that facility and produce, say,
20 tonnes a day.
“So they still have the same revenue but their profit margin goes through the roof because there is no on-going disposal cost.”
The average payback on the capital expenditure is 18 months, with the BTD designed for a usable life of 10 years. A chest freezer-sized machine costs around £20,000, while an articulated lorry-sized one costs around £700,000, which would do 55 tonnes of waste a day.
Once you have bought the machine, for every metric tonne of waste that is put into the front, Advetec calculates the disposal cost at £1.21.
Shaw says the technology is complementary to existing processes. A client in Abu Dhabi was using a MRF to sort mixed waste, but the MRF frequently got clogged up with organic material and had to be shut down. So it installed a BTD pre-MRF, and it has reduced downtime, improved the working environment and enabled non-organic materials to be sorted.
Incinerator operators are also interested. In the US, a pilot plant is being built in Tampa. The current 100MW plant cannot run above 75MW due to the organic content and moisture in black bag waste. The pilot will trial whether pre-processing the material
with the BTD, so that only the inorganic fraction goes into the incinerator, will generate a better energy yield.
And California is looking at putting all of its waste through a BTD process so that what comes out is sorted and can be recycled.
Shaw sees the technology - with everything out the back end of the machine being recyclable, apart from heavy metals and radioactive waste - as part of the shift towards zero waste.
Advetec was formed in 2000, as a specialist in bio-stimulants and ‘understanding how to get the most work out of bacteria’. It has worked in waste water, industrial effluents, river contamination and landfill contamination.
The idea for the BTD came about back in 2006/07 when one of its clients bought an in-vessel composting machine that was struggling to process the waste it was being. Advetec started looking into what strains of bacteria would eat this type of waste quickly.
The initial machine was ready to launch in 2008, just as the global financial crisis hit. So it used the past five years to enhance, redevelop and trial the technology.
The machines, manufactured in the UK, have been available since September.
Other key markets include the utilities sector and the military, as well as new sustainable housing developments.