Fish bones turn plastic waste into valuable oil

The study was published in the journal Sustainable Carbon Materials. Polyethylene film is widely used in agriculture, but recycling it is often uneconomical because the cost of cleaning the material can exceed the cost of producing new plastic. Collecting plastic residues from fields is also difficult, as they can remain in the soil and gradually break down into microplastics.

Conventional thermal treatment is not considered an ideal solution either, as it requires extremely high temperatures and can produce an unpredictable mixture of products.

The researchers developed an unconventional catalyst using recycled bones from whitefish. The bones were treated with phosphoric acid, combined with iron and heated in the absence of oxygen. The resulting material helped steer the breakdown of plastic film towards the production of more desirable compounds.

In a two-stage reactor, the plastic was first heated to 550°C before its vapours were passed through the catalyst at 350°C. Under optimal conditions, the process achieved a liquid product yield of 89.32%.

Almost all of the hydrocarbons produced fell within the desired C6–C12 range, while olefins—key building blocks for the chemical industry—accounted for 84.03% of the products. Only 0.43% of coke was formed.

The catalyst retained its high efficiency after five regeneration cycles. The researchers now plan to investigate its resistance to coke deposition and assess whether the technology can be scaled up for industrial use.