Processing of End-Of-Life Flowlines, Umbilicals and Tyres into Useful Energy Resources

The global drive for sustainable waste management has highlighted the urgent need for viable solutions to process complex composite waste such as subsea umbilicals, flowlines, risers and used tyres. This project aims to explore a thermochemical conversion route using pyrolysis to transform these waste materials into valuable energy products liquid fuels, monomers, and hydrogen while minimizing solid residues and eliminating landfill disposal. The broader goal is to support the development of scalable, modular, or mobile systems for waste recycling and energy recovery. Flowline, Umbilicals and Risers sample were mechanically separated, and their polymer fractions were thermally characterized using thermogravimetric analysis (TGA), revealing over 96% volatile content in the yellow polypropylene layer from Flowlines. Bench-scale pyrolysis experiments were conducted at 500°C, achieving a high yield of condensable liquid (85.37%), non-condensable gases (9.74%), and minimal solid residue (4.89%). Elemental analysis was performed to determine carbon, hydrogen, nitrogen, sulfur, and oxygen content, while GC-MS was used to identify the presence of nitrogen-containing amides. Micro-GC analysis was conducted on gases produced from oil heating to assess hydrogen concentration. The results demonstrated significant energy recovery, with a marked increase in hydrogen content from 14.2% to 26.2% as the pyrolytic oil was heated from 275°C to 300°C, confirming its potential as a hydrogen source. Importantly, no NOx emissions were detected. The minimal residue (4-5%) left after pyrolysis of flowline validates the approach for near-zero landfill waste. These findings support the feasibility of deploying a pyrolysis-based system for recycling decommissioned offshore infrastructure. This research establishes a pathway for the conversion of complex polymeric and composite offshore waste into useful energy products using low-to-moderate temperature pyrolysis. The ongoing work focuses on the characterization and processing of additional materials, including umbilicals, risers, tyres, and conveyor belts. Progress to date supports the future development of a modular or mobile pilot-scale processing unit, complemented by life cycle and techno-economic assessments to enable commercialization. This work advances circular economy initiatives and offers a scalable solution to the environmental challenges associated with offshore waste.