Polyethylene (PE) is the most important synthetic polymer material produced. Its excellent material properties arise from crystalline interactions in its hydrocarbon chains. This simple concept inspires studies of materials based on alternative non-fossil feedstocks and with additional traits such as a non-persistent nature. Renewable seed oil or microalgae oil lipids can serve as a feedstock for long-chain difunctional monomers. Catalytic conversion of their unsaturated fatty acids by e.g. isomerizing carbonylation or olefin metathesis yields long-chain monomers X-(CH 2 ) n -X with 18–26 carbon atoms and terminal dicarboxy, diol or diamine groups (X), and ultralong-chain PE telechelics with 48 carbon atoms. These can be polymerized to polyesters, polycarbonates and other (ultra)long-chain polycondensates. These in many cases possess PE-like solid-state structure and properties. Unlike PE, they contain in-chain functional groups that can potentially enhance degradability. The crystalline and hydrophobic nature of the polymers decelerates degradation strongly compared to rapidly degrading shorter chain analogues. Our preliminary findings suggest that a non-persistent nature can be achieved for these materials. This review article is based on a lecture held at the Royal Society Discussion Meeting on Science to enable the circular economy. This article is part of a discussion meeting issue ‘Science to enable the circular economy’.