Small-scale plastics-to-diesel plants can be used by communities and in cooperation with municipalities to derive value from waste plastics, says Plastic Diesel cofounder and entrepreneur Deon Bester.

With the help of a research partner in New Zealand, the plant has been developed from 2012 to 2014. Similar pyrolysis technologies are used in the US and UK, but Bester has aimed to keep the price of the plants low to enable their broad and small-scale use.

The plants are fully automated and changing the programmable logic controller settings can enable different fuels, such as jet fuel, paraffin and petrol, to be captured. However, these fuels are reused instead to heat the plastics in the reactor.

“The main concept behind our design of the plant was to ensure that it does not need to use power from the grid, as is commonly done in other countries. Therefore, the machine creates diesel and about 10% of various mixed fuels, called multifuel, which are then used as fuel for the pyrolysis.”

The initial start-up – heating the reaction chamber and the plastics to 420 ºC – uses liquid-petroleum gas, which is another one of the fuels liberated from the plastics, but once the process is running, the machine runs completely on the multifuel it liberates.

The plant uses a two-column distillation process that includes a catalytic conversion chamber to improve conversion of the liberated polymers into diesel and related fuels; air- separation vortices, based on the specific gravities of the various fuels; and another distillation column to condense the diesel into a tank.

“In testing, 1 kg of plastic converts to about 800 mℓ of fuel, of which about 10% is multifuel and 720 mℓ diesel. Oil and wear specialist company Wearcheck conducted tests on the diesel, which found that it had 19 ppm sulphur content and met South African National Accreditation System requirements.”

The machine can convert any oil-containing plastics to diesel, including shopping bags, containers and tyres, as well as used oils. The two types of plastics that do not contain enough oils are polyvinyl chloride, mostly used for water and utility pipes, and polyethylene terephthalate, commonly used to manufacture water bottles.

The first Plastic Diesel plant will be installed later this month in Bothaville, the Free State, with another plant to be installed in Hoedspruit, Limpopo, in early 2015.

Plastics are fed into a preheating hopper that heats the plastics to 120 ºC and continuously feeds plastics into the reaction chamber of the plant. The plant runs for seven to ten days and produces about 2 000 ℓ/d of diesel. The char is then removed from the reaction chamber before the plant is run again.

Waste plastic is commonly available at about R3.50/kg, which should produce diesel to the value of R9, at the October price of R12.53/ℓ.

“Community recycling projects can be effectively incentivised through the production of diesel, with community recyclers receiving money for each kilogram of plastics they deliver to the plant. The municipalities can use the diesel produced to run their fleets or sell it to local companies or users,” says Bester.

The company held a demonstration at the University of Pretoria (UP) LC de Villiers sports campus, and UP landscaping and sport facilities operations manager Johan Britz says the university would provide waste plastics for use in such plants as part of its recycling initiatives.