thermal conversion - coming to a site near you.

CWT - keeping up the pressure

V irritatingly I find that some of my posts, eg this one, preserve the date of my first saving them in draft form, so don't trust these dates, as I sometimes don't complete the pieces for days or weeks.

Just read a fascinating article in the current issue of Cosmos, the Oz science mag, about the commercialisation of a process for turning waste into oil.

Changing World Technologies (CWT) is a company based in Carthage, Missouri, the American mid-west. It's 'the first commercial biorefinery in the world that can make oil from a variety of waste streams', according to its CEO, Brian Appel.

It's taken some time, with many headaches along the way, to make the process viable, but at its heart the technology's disarmingly simple. It's called the Thermal Conversion process - originally called the Thermal Depolymerisation process, which is unwieldy but gives more insight into what's involved. The key to the process is temperature and pressure. The raw material can vary - the technology's incredibly adaptable - but currently it's mostly animal waste, eg tonnes of turkey remains and excrement from a food processing plant involved in a joint venture with CWT. Here's the mag's summary:

A pressurised pipe pushes raw material into a brawny grinder that chews it into pea-sized bits. Dry raw materials such as tyres and plastics require extra water at this stage, but offal is wet enough. A first-stage reactor uses heat and pressure to break down the material , after which the pressure rapidly drops, flashing off excess water and minerals. In turkeys, minerals come largely from bones, and are shunted to a storage bin to be dried into a high-calcium fertiliser.
The remaining concentrated organic soup moves to a second reaction tank where it is heated to 260 C and pressurised to 42 kg/cm (squared). In just 15 minutes, the process can shorten complex long-chain molecules of hydrogen and carbon into rather shorter and lighter molecules of oil.
Next, the pressure and temperature drop and the soup swirls through a centrifuge that separates the remaining water from the oil. The water, which in the case of slaughterhouse waste is laden with nitrogen and amino acids, is stored to be sold as a high-potency liquid fertiliser. Meanwhile, the oil goes into the storage tank to await the next truck.

It's very fuel-efficient, apparently, with only 15% of the potential energy of the feedstock being used to power the plant. It's also just giving a helping hand to 'nature' you might say, as this is just the process that creates oil in the ground over time. The Thermal Conversion process removes the haphazardness and chaos from nature's way, using optimal heat and pressure for depolymerisation to take place.

So how come it's taken so long to come up with this process? Well, some scientists have succeeded in converting organic molecules into oil on a small scale, but there have been many drawbacks to commercial-scale operation. One of the problems has been the removal of water, which requires a lot of energy. Superheating to drive off the water and break down the molecules in one step has proved highly inefficient - CWT's process involves harnessing the water to limit the reactions and then separating it out via centrifuges and rapid depressurisation.

Not that there haven't been enormous teething problems. The enormous stench involved in working with this waste material had local authorities and residents most upset for quite a time, but this has apparently been fixed up. Another major problem was adjusting the plant's pressure, temperature and water levels to a varying supply of waste material. A truckload of bones and feathers will have a very different chemical composition, and will be much drier, than a truckload containing a lot of blood, for example.

There were many other construction problems and delays, too, causing the 'moment' of the plant's commercial viability to be put back months and years. There were also issues around market response and subsidies, and these are ongoing to some extent but have improved in recent months, not surprisingly.

I must admit to a sense of wowness in reading about this - something of a fillip to my jaded nature. One of the most impressive things about the process is that all the products have a solid potential use (as per above quote).

The oil itself is of a type widely used to power electrical generators. It can be sold to utilities for this purpose or further refined into vehicle-grade diesel and petrol. And the fertiliser by-products are apparently of eye-popping standard.

Also the system is flexible enough to be adjusted to take in all sorts of raw materials, including junked car parts once the scrap metal is removed. Hydrochloric acid, for use in industrial solvents, become a useful by-product in this instance.

The technology obviously deserves support, but has struggled for it. Europe has shown rather more interest than the US, where only 3 states have provided incentives to make the process financially worthwhile. Needless to say, the conventional fossil fuel industry is v heavily subsidised.

And what about Oz? We have a company here called Ozmotech which uses a patented process called ThermoFuel to transform waste plastic to diesel. The possibility of thus diverting thousands of tonnes of plastic from landfill should have caught the imaginations [sic] of our leaders. However, no Australian plastics are currently used inthe ThermoFuel process, and it's doubtful if this will change in the foreseeable, as the federal government has proposed a tax on the fuel thus produced.