Agricultural plastic mulch helps farmers conserve water, control weeds, and improve crop productivity, but disposing of the used films creates a growing environmental challenge. Researchers have now developed a catalyst made from fishbone-derived char, phosphoric acid, and iron that converts low-density polyethylene agricultural film into bio-oil with a yield of up to 89.32 wt.% and an olefin selectivity of 84.03%.
The study, published in Sustainable Carbon Materials , explores a microwave-assisted catalytic pyrolysis process designed to recover valuable hydrocarbons from waste agricultural plastics while also finding a productive use for discarded fish bones.
“ Our goal was to develop a low-cost catalyst that can direct plastic pyrolysis toward more valuable products rather than simply breaking the polymer into a complex mixture of hydrocarbons, ” said a study author. “ By combining the natural mineral structure of fish bones with phosphorus and iron, we were able to create complementary acid and metal active sites that strongly favored the formation of olefins. ”
Low-density polyethylene, or LDPE, is widely used for agricultural mulch because it is lightweight, durable, and effective at retaining soil moisture. After use, however, contaminated films can be difficult to collect and recycle. Landfilling or incineration can waste their carbon resources and may create additional environmental burdens.
Pyrolysis offers another route by heating plastics without oxygen and breaking their long molecular chains into smaller hydrocarbons. A major challenge is controlling what those reactions produce.
The researchers prepared fishbone char and modified it with different concentrations of phosphoric acid and iron. Among the catalysts tested, 20Fe-30P@FC, produced using 30 wt.% phosphoric acid treatment and a nominal 20 wt.% iron loading, showed the strongest overall performance.
Without a catalyst, the plastic produced a bio-oil yield of 72.3 wt.% with an olefin selectivity of 43.78%. With 20Fe-30P@FC, bio-oil yield increased to 89.32 wt.% and olefin selectivity rose to 84.03%. Most notably, C6-C12 compounds accounted for 99.78% of the targeted hydrocarbon fraction under the optimized conditions.
Materials characterization indicated that phosphoric acid treatment altered the original hydroxyapatite-rich fishbone structure and introduced acidic phosphate groups. Iron loading subsequently created strongly interacting Fe-O-P structures. The researchers propose that this combination provides acid sites that promote carbon-carbon bond cleavage together with iron-based sites that help regulate dehydrogenation and hydrogen-transfer reactions.
The team also optimized operating conditions. The best results were obtained at a plastic pyrolysis temperature of 550 °C, a catalytic temperature of 350 °C, and a catalyst-to-feedstock mass ratio of 1:2.
Reusability tests further showed that the catalyst retained much of its activity after repeated regeneration. After five cycles, bio-oil yield decreased only from 89.32 wt.% to 86.52 wt.% , while olefin selectivity remained at 82.32% and the C6-C12 fraction remained at 99.11% .
The findings suggest that combining fish-processing waste and agricultural plastic waste in one resource-recovery strategy could provide a promising route toward more selective chemical recycling. Further work will be needed to evaluate long-term catalyst durability, process scale-up, and economic performance before industrial application.
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Journal reference: Yang J, Zhang Y, Duan D, Chen X, Lan X, et al. 2026. Iron and phosphoric acid co-modified fishbone char for olefin-rich bio-oil production from waste agricultural films via microwave-assisted pyrolysis. Sustainable Carbon Materials 2: e026 doi: 10.48130/scm-0026-0021
https://www.maxapress.com/article/doi/10.48130/scm-0026-0021
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Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
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Sustainable Carbon Materials
Experimental study
Iron and phosphoric acid co-modified fishbone char for olefin-rich bio-oil production from waste agricultural films via microwave-assisted pyrolysis
30-Jun-2026