The growing use of carbon and glass fibres has increased awareness about their waste disposal methods. Tonnes of composite waste containing valuable carbon fibres and glass fibres have been cumulating every year from various applications. These composite wastes must be cost-effectively recycled without causing negative environmental impact. This review article presents an overview of the existing methods to recycle the cumulating composite wastes containing carbon fibre and glass fibre, with emphasis on fibre recovery and understanding their retained properties. Carbon and glass fibres are assessed via focused topics, each related to a specific treatment method: mechanical recycling; thermal recycling, including fluidised bed and pyrolysis; chemical recycling and solvolysis using critical conditions. Additionally, a brief analysis of their environmental and economic aspects are discussed, prioritising the methods based on sustainable values. Finally, research gaps are identified to highlight the factors of circular economy and its significant role in closing the life-cycle loop of these valuable fibres into re-manufactured composites.

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A review on the recycling of waste carbon fibre/glass fibre-reinforced composites: fibre recovery, properties and life-cycle analysis

Wind turbine blade waste in 2050.

Operations and maintenance of offshore wind turbines (OWTs) play an important role in the development of offshore wind farms. Compared with operations, maintenance is a critical element in the levelized cost of energy, given the practical constraints imposed by offshore operations and the relatively high costs. The effects of maintenance on the life cycle of an offshore wind farm are highly complex and uncertain. The selection of maintenance strategies influences the overall efficiency, profit margin, safety, and sustainability of offshore wind farms. For an offshore wind project, after a maintenance strategy is selected, schedule planning will be considered, which is an optimization problem. Onsite maintenance will involve complex marine operations whose efficiency and safety depend on practical factors. Moreover, negative environmental impacts due to offshore maintenance deserve attention. To address these issues, this paper reviews the state-of-the-art research on OWT maintenance, covering strategy selection, schedule optimization, onsite operations, repair, assessment criteria, recycling, and environmental concerns. Many methods are summarized and compared. Limitations in the research and shortcomings in industrial development of OWT operations and maintenance are described. Finally, promising areas are identified with regard to future studies of maintenance strategies.

Offshore wind turbine operations and maintenance: A state-of-the-art review

The wind power industry is a fast growing, global consumer of glass fiber-reinforced plastics (GFRP) composites, which correlates with the industry’s rapid growth in recent years. Considering current and future developments, GFRP waste amounts from the wind industry are expected to increase. Therefore, a sustainable process is needed for dealing with wind turbines at the end of their service life in order to maximize the environmental benefits of wind power. Most components of a wind turbine such as the foundation, tower, gear box and generator are already recyclable and treated accordingly. Nevertheless, wind turbine blades represent a challenge due to the type of materials used and their complex composition. There are a number of ways to treat GFRP waste, depending on the intended application. The best available waste treatment technologies in Europe are outlined in this paper. However, there is a lack of practical experiences in applying secondary materials in new products. A Danish innovation consortium was addressing this waste with a predominant focus on the blades from the wind power industry. The outcomes from the consortium and the various tested tools are presented in this paper as well as the secondary applications that were proposed. The outcomes are structured using Ellen MacArthur’s circular economy diagram. The “adjusted” diagram illustrates the potentials for a continuous flow of composite materials through the value circle, where secondary applications were developed in respect to “reuse”, “resize and reshape”, “recycle”, “recover” and ‘conversion’. This included applications for architectural purposes, consumer goods, and industrial filler material. By presenting the outcomes of the consortium, new insights are provided into potential forms of reuse of composites and the practical challenges that need to be addressed.

Wind turbine blade recycling: Experiences, challenges and possibilities in a circular economy

Microwave or dielectric heating is an accepted new technique to run chemical conversions on a lab scale as an alternative heating principle. Microwave heating is believed to be more depending on the molecular properties and the reaction conditions than conventional heating. At first sight microwave-assisted chemistry looks very promising given the overwhelming number of publications during the last two decades. To predict its potential for industrial purposes, it is necessary to make a proper comparison between both heating techniques. The underlying theory, “Green Chemistry” and the microwave effect are relevant topics to be studied in detail in nowadays’ organic chemistry. According to literature microwaveassisted chemistry seems to perform well and sometimes it even works better than expected. Magic or hidden logic?

A microwave heating

Wind turbine blade end-of-life options: An eco-audit comparison

Global wind energy is developing rapidly, with total installed capacity having increased from 24,332 MW in 2001 to 650,758 MW in 2019. Environmental concerns have been raised over the large volumes of waste that will be generated as these wind turbine blades are decommissioned over the coming decades. Although wind turbines are largely clean during operation, in manufacture and end-of-life stages they release emissions and consume significant energy. Wind turbine blades are mainly made from lightweight thermoset composites (glass fibre/carbon fibre), which are economically challenging to recycle. This study aims to understand the economic feasibilities of recycling technology options for blade waste management. We have used a quantitative method, first building a financial performance model for wind turbine blade end of life, then evaluating and comparing the financial performance for all available end of life options, and finally performing a sensitivity analysis. We found that mechanical recycling and fluidised-bed recycling are the optimal options of the ready-to-go technologies, and chemical recycling is the optimal option for technologies currently available only at lab scale. 

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Wind turbine blade end-of-life options: An economic comparison

The first generation of wind turbine (WT) blades are now reaching their end of life, signalling the beginning of a large problem for the future. Currently most waste is sent to landfill, which is not an environmentally desirable solution. Awareness of this issue is rising, but no studies have fully assessed the eco impact of WT blades. The present study aims to provide a macroscopic quantitative assessment of the lifetime environmental impact of WT blades. The first stage has been to analyse global data to calculate the amount of WT blade materials consumed in the past. The life cycle environmental impact of a single WT blade has then been estimated using eco data for raw materials, manufacturing processes, transportation, and operation and maintenance processes. For a typical 45.2 meter 1.5 MW blade this is 795 GJ (CO2 footprint 42.1 tonnes), dominated by manufacturing processes and raw materials (96% of the total. Based on the 2014 installed capacity, the total mass of WTB is 78 kt, their energy consumption is 82 TJ and the carbon dioxide footprint is 4.35 Mt. These figures will provide a basis for suggesting possible solutions to reduce WTB environmental impact.

https://iopscience.iop.org/article/10.1088/1757-899X/139/1/012032/pdf

The environmental impact of wind turbine blades

The main reaction range (350–550 °C) of oil-based drilling cutting (OBDC) pyrolysis was studied by a thermogravimetric analyzer and a vacuum tube furnace. The average activation energies calculated by four model-free methods were 185.5 kJ/mol (FM), 184.16 kJ/mol (FWO), 166.17 kJ/mol (KAS), and 176.03 kJ/mol (Starink). The reaction mechanism was predicted by the Criado (Z-master plot) method. It is found that a high heating rate is helpful to predict the reaction mechanism, but it cannot be described by a single reaction model. Under the conditions of target temperature higher than 350 °C, residence time higher than 50 min, laying thickness less than 20 mm, and heating rate lower than 15 °C, the residual oil content is lower than 0.3% and the recovery rate of mineral oil is higher than 98.43%. Solid phase products accounted for more than 70%, reached the maximum 17.04% at 450 °C, and then decreased to 15.87% at 500 °C. Aromatic hydrocarbons, as coking precursors, are transformed from a low ring to a high ring. Recycled mineral oil can reconfigure oil-based mud (OBM). The research results can provide a theoretical basis for process optimization.

Pu Liu

Papers

Wind turbine blade waste in 2050.

Wind turbine blade end-of-life options: An eco-audit comparison

Wind turbine blade end-of-life options: An economic comparison

The environmental impact of wind turbine blades

Study on Pyrolysis of Shale Gas Oil-Based Drilling Cuttings: Kinetics, Process Parameters, and Product Yield