Reusability of offshore steel structural components for new buildings are presented in this paper. Status and benefits of reusing steel members are compared with the re-cycling. The reuse process of offshore steel for buildings is presented in detail as there is a lack of literature in this field. Hence, a framework is introduced by specifying each operation in the process such as decommissioning, demounting, cleaning, modification, material quality and geometry checks. An index is introduced to check the degree of reusability. Knowledge and research gaps related to technical, economic and environment aspects of the introduced framework are identified and recommended for future studies.
The steel industry requires quite a lot of energy which significantly affect the global CO2 emission. One third of the CO2 emissions are produced by the construction industry (Fujita et al, 2008, Tingley et al. 2017, Nordic circle,2023). Therefore, it is essential to reduce this emission. As a result of this, the industry is highly paying attention about the measures such as (i) the life extension of existing structures, (ii) the reusability of steel members which are used in decommissioned structures for new structures and (iii) the recycling of decommissioned steels (Fujita et al. 2008). Use of a structural component after its first use/life is generally defined as reuse.
From 5 to 600 ships are decommissioned every year and the total amount of decommissioned steel is around twelve billion (Barth, 2023). According to OSPAR inventory of offshore installations, average ages of North Sea installations are 26, 24, 24 and 22 years in UK, Norway, Netherland and Denmark, respectively. This indicates that majority of the offshore platforms are reaching to the end of their design life and either decommissioning or life extension is required. 12% of offshore installations (i.e. 88 oil platforms) are supposed to be decommissioned and 77 (i.e. 93%) of those are steel bottom fix and floating platforms (OSPAR 2019). The global decommissioning expenditure, from 2018 to 2027, is around 82 billion dollars which is one of the top global markets. The estimated amount of decommissioning steel in the North Sea from 2018 to 2017 are around 950000 tons from topsides, 475000 tons from jacket structures and a length of 5724km of pipelines (Noth Sea Transition Authority, 2018). Generally, these structural steel members/components are durable, robust and stable in dimensions with the lifetime. Therefore, it is possible to reuse steel of offshore installations as a scale of a module, structural system (i.e. truss, frame or etc) and/or individual member (i.e. basic structural element) as opposed to current common recycling practice. Average CO2 emissions for producing new steel, recycling and reuse (i.e upcycling) are 2.8, 1.35 and 0.24 metric Ton/1 Tons of steel respectively. Therefore, it is beneficial to reuse the steel used for marine structures for buildings as there are huge amount of steel after decommissioning of these structures.
