Tyre pyrolysis oil is a mixed bag. We’ve seen analyses of TPO from a range of processes with wide and varied results and concluded that it does really depend on the process and subsequent treatment. For example tyres are made with natural rubber and thus some of the hydrocarbons gases and liquids produced will be biogenic. You might expect the biogenic content of these both to match the mixture of natural and synthetic rubber in the tyres, but apparently not. Several years ago we had a TPO analysed and it had with <6% biogenic content (from car tyres, which are typically 30% natural rubber); meanwhile Enviro’s returned >45% biogenic content (from 85% car tyre). In both cases you could determine where the balance of biogenic or fossil content ended up (e.g. in the gas or light hydrocarbons), but it tells us two things: that the natural and synthetic rubbers both decompose into liquids and gases, but which goes where is process dependent. There are numerous other factors to consider (monomers, aromatics etc) which also vary; we can’t say Enviro’s oil is better than the rest, but it’s up there and at least Wärtsilä is happy to endorse its use.