Do recycled carbon fuels have a future?

From the middle of 2021, when the new Renewable Energy Directive comes into force, countries in Europe will be able to count recycled carbon fuels towards their targets for renewable transport fuels. Diesel and petrol made from waste plastic, end-of-life tyres and other fossil waste can all qualify as ‘recycled carbon fuels’.  But firstly these wastes have to be liquefied or gasified if they are to be made into fuel.  

In the UK the government just announced grants to scale up plastic liquefaction technology.  Chevron Phillips has started commercial operation of a similar process in the US.  Other companies are developing their own technology as well. But these businesses are focussing on producing chemicals and plastic via ‘chemical’ or ‘molecular’ recycling. There is no discussion about the parts of the liquefied product that can’t readily be transformed back into new plastics. Yet these difficult fractions could be transformed into recycled carbon fuels. Unfortunately such fuels are facing opposition, which doesn’t take into account the realities of waste management and recycling carbon-containing materials.

Liquefying or gasifying waste, so it can be recycled into something useful, is expensive. The intermediate liquid (or gas) contains most of the impurities that were originally present in the waste. There is sulphur in used tyres, chlorine in end-of-life PVC and bromine in flame-retardant treatment. These impurities have to be removed.  Also, transporting the waste to processing facilities in the first place is expensive. If all the costs could be shared between recycled plastics and recycled carbon fuel then both technologies could see increased take up.

Opponents are already urging policy makers to avoid these fuels. Opposition to recycled carbon fuels centres on whether they will save enough greenhouse gas emissions and whether they will compete with established recycling routes. First of all let’s examine the importance of GHG savings. From a climate point of view, burying end-of-life fossil material in a landfill is not a bad option, as it locks up the carbon semi-permanently. However poor waste management and landfilling has led to pollution. The imperative of keeping waste plastic out of the oceans has, in effect, become more important than the magnitude of the GHG savings of differerent treatment routes.

Now lets look at the argument that says recycled carbon fuels will compete with current recycling. Policy makers and NGOs are promoting conventional mechanical recycling as the preferred option. However there are limits to the number of times plastic can be mechanically recycled before it deteriorates and has to be disposed of.  Mechanical recyclate also has a limited range of uses. For instance, food contact approval is difficult, if not impossible to obtain for much mechanical recyclate. For these reasons companies are turning to chemical/molecular recycling to obtain a high quality product. 

There are already incentives to recycle plastic waste either chemically or mechanically into new plastics.  Fractions of the waste that can’t be economically recycled are likely to be burnt for heat or energy anyway. So why not accept that they can be used for road transport fuel? Recognising that recycled carbon fuels have an important role is the only way we will square the circle of carbon recycling. 

Published: 20 October 20

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