Driving ahead with plastic diesel
You know the world is evolving when the cling film from your sandwich drives you to work. You can then go about your daily tasks, before cadging a lift home from your trusty plastic shopping bag.
Sadly, this is not a prelude to another dodgy Alice in Wonderland sequel. It is a reality of sorts. By 2012, the first UK facility to convert end-of-life plastics into road specification diesel and other kerosene fuels is scheduled to open.
Recycling and resource management company SITA has collaborated with Londonbased patent holders Cynar to find a home for the waste plastics from recycling facilities.
Phil Holland, Development Manager at SITA, explains the market need for this technology. ‘If one looks at general industrial packaging waste and municipal waste, most of the recycled plastics go through materials recycling facilities.
The valuable polymers get pulled off during the traditional recycling process, but there is still a residual material that would then be required to go to landfill or incineration. We’ve estimated that in London alone, there are 26,000 tonnes of these types of material.’
SITA intends to take most of these residual plastics, which include films, bags and plastic trays. After the materials have been separated at source through municipal waste or commercial contracts with packaging companies or food processing companies, they go through shredding and dry washing systems. The process will accept various polyethylenes, polypropylenes and polystyrenes, though PET and PVC cannot be accepted.
The materials will be fed into a pre-heating system that will heat the plastics into a thick liquid until it reaches about 300ºC. The liquid plastic will then be channelled into one of four pyrolysis chambers, at which point the volatile hydrocarbon gases eventually come off. The gases go through to distillation processes in the form of two distillation columns. The output from the columns will be diesel, kerosene and a light petroleumtype oil.
According to Holland, this process can produce about 700 litres of full road specification diesel and 200 litres of kerosene for every tonne of suitable waste product inputted. He says trials found that it has an equivalent octane or cetane rating to road diesel, and that it is less harmful to the environment than mineral diesel.
‘We’ve done tests on the fuel on combustion and particulates, and it is directly comparable to the mineral diesel. We also believe it will have a lower carbon footprint compared with mineral diesel because there is a significant footprint in producing mineral oil diesel. The kerosene is similar,’ he claims.
That said, the process has encountered teething problems. He explains, ‘If you put PET waste into the plant, you will spoil your fuel output. So, the fuel is somewhat dependant on the plastics input.’ He adds that the materials have to be kept dry. The Erema extruder will only accept up to 12% moisture content, ‘which can be a problem, because anything stored in the UK will be at those sort of levels’.
Holland envisages that three or four of these conversion plants will be built in the UK over the next two or three years, with 5-6,000 tonnes going through each plant annually. The first, in Avonmouth, UK, is scheduled to be up and running by 2012.
SITA expects to sell the fuel as a bulk diesel product at current market price, and will charge a gate fee of £25- 30 per tonne for the waste plastics. While SITA intends to sell the fuel to local suppliers, Holland is unperturbed if this doesn’t bear fruit. ‘We have 1,700 trucks in our fleet in the UK alone,’ he says. ‘We can burn the fuel we produce on our own.’