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The background to this research is that across the world there will be 200,000 tonnes of wind turbine blade waste to be disposed of each year from 2033. The purpose of the research is to compare the relative sustainability of alternative ways to deal with this waste, these being: landfill, incineration with heat recovery, co-processing in cement kilns, making furniture and bridge fabrication. The method is to use the UN Sustainable Development Goals (SDGs) to select 11 metrics for sustainability. The use of the SDGs adds to the objectivity of this process overcoming one of the principal weaknesses of Multiple Criteria Decision Analysis (MCDA). Quantitative information methods from Life Cycle Assessment, Geographic Information Science, census data and real options analysis of R&D, alongside qualitative information from Delphi studies and Strengths/Weaknesses/Opportunities/Threats analysis are combined in the assessment. Three MCDA methods are used, each calculates economic, social and environmental sustainability indices for the end-of-life alternatives which are then combined into integrated sustainability indices. A novel Delphi stopping condition based on consensus, consistency and convergence is used. The primary result is that bridge fabrication is the most sustainable alternative with furniture making in second place. Co-processing, incineration with heat recovery and landfill are progressively less sustainable alternatives. This result is robust to substantial changes in the selection of experts' opinions, the weights for MCDA and the values of the metrics. These findings offer researchers and policymakers a robust decision making process, applicable to situations where choices are made on sustainability criteria.

This paper describes repurposing projects using decommissioned wind turbine blades in bridges conducted under a multinational research project entitled “Re-Wind”. Repurposing is defined by the Re-Wind Network as the re-engineering, redesigning, and remanufacturing of a wind blade that has reached the end of its life on a turbine and taken out of service and then reused as a load-bearing structural element in a new structure (e.g., bridge, transmission pole, sound barrier, seawall, shelter). The issue of end-of-life of wind turbine blades is becoming a significant sustainability concern for wind turbine manufacturers, many of whom have committed to the 2030 or 2040 sustainability goals that include zero-waste for their products. Repurposing is the most sustainable end-of-life solution for wind turbine blades from an environmental, economic, and social perspective. The Network has designed and constructed two full-size pedestrian/cycle bridges—one on a greenway in Cork, Ireland and the other in a quarry in Draperstown, Northern Ireland, UK. The paper describes the design, testing, and construction of the two bridges and provides cost data for the bridges. Two additional bridges that are currently being designed for construction in Atlanta, GA, USA are also described. The paper also presents a step-by-step procedure for designing and building civil structures using decommissioned wind turbine blades. The steps are: project planning and funding, blade sourcing, blade geometric characterization, material testing, structural testing, designing, cost estimating, and construction.

Fiber reinforced polymer (FRP) composite materials have been used in a variety of civil and infrastructure applications since the early1980s, including in wind turbine blades. The world is now confronting the problem of how to dispose of decommissioned blades in an environmentally sustainable manner. One proposed solution is to repurpose the blades for use in new structures. One promising repurposing application is in pedestrian and cycle bridges. This paper reports on the characterization of a 13.4-m long FRP wind blade manufactured by LM Windpower (Kolding, Demark) in 1994. Two blades of this type were used as girders for a pedestrian bridge on a greenway (walking and biking trail) in Cork, Ireland. The as-received geometric, material, and structural properties of the 27 year-old blade were obtained for use in the structural design of the bridge. The material tests included physical (volume fraction and laminate architecture) and mechanical (tension and compression) tests at multiple locations. Full-scale flexural testing of a 4-m long section of the blade between 7 and 11 m from the root of the blade was performed to determine the load-deflection behavior, ultimate capacity, strain history, and failure modes when loaded to failure. Key details of the testing and the results are provided. The results of the testing revealed that the FRP material is still in excellent condition and that the blade has the strength and stiffness in flexure to serve as a girder for the bridge constructed.

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