Abstract

In the last decade, a great effort has been made to achieve a transition from the current linear economy to a circular economy. This transition also affects the composites sector, which, due to the intrinsic complexity of recycling, requires the implementation of recovery and remanufacturing processes that will be technically, economically and environmentally feasible. This challenge was addressed within the FiberEUse project, in which one of the working lines was based on waste recycling from wind and aeronautical sectors. Both glass and carbon fiber were recovered by pyrolysis. Subsequently, the recycled fiber was treated and processed with thermoplastic matrices used in automotive applications. The technologies used and the results obtained throughout the value chain, from the waste to the part, are presented in this paper. Formulations with different recycled fibers, with and without sizing treatments and with different matrices, were manufactured by compounding-injection. These materials were mechanically analysed and tested with the aim of selecting three formulations. The reinforced materials were validated in three real automotive prototypes: a pedal bracket, a front-end and a cowl top support. As a result, the prototypes were manufactured, tested and validated by the automotive companies.

Abstract

This paper presents the experimental validation of a thermal treatment technology to recover added-value substances from the plastic matrix of end-of-life wind turbine blades, when these are subjected to a pyrolysis process to recover the glass fibres. The experiments have been carried out in a laboratory installation consisting of two reactors in series, in which pyrolysis and thermal treatment of pyrolysis gases and vapours take place, respectively. The application of this treatment enables a 25 wt.% reduction in the production of pyrolysis liquids, increasing the production of gases in an equivalent way and without compromising the pyrolysis conditions to be used to recover the glass fibres. The two-phase liquids are converted into single-phase aqueous ones, while the hydrogen concentration in the gases increases from 4 % to almost 50 % in volume. This high concentration of hydrogen in the gases allows them to be used as a source of hydrogen for various applications. Consequently, the technology demonstrates that the plastic matrix of wind turbine blades can be valorised in a pyrolysis based recycling process.

Abstract

With fuel economy and lightweight design becoming ever more significant due to the current materials, resources and environmental crisis, the manufacture of polymer composites for automotive industry use has experienced a steady growth in the last years and is expected to keep growing in the coming years. This means that there is a vast range of different polymer composites available in the market, with their unique properties, manufacturing processes and materials imbedded in them, each with their own set of impacts on the environment throughout their whole life cycle. The end-of-life treatment of a composite determines a substantial fraction of its footprint on the planet, and advanced treatments, namely pyrolysis can be used to obtain high value added compounds such as hydrogen and other light fuels. This study aims to address and quantify the impacts associated with the manufacturing and end of life treatments of an experimental glass fibre mat reinforced thermoplastic composite and compare them with the impacts caused by materials currently used in the automotive industry. Life Cycle assessment methodology will be used to compare the environmental impacts of this new material with traditional glass fibre composites, natural fibre reinforced composites and other materials with similar mechanical properties.

Abstract

Pyrolysis is a technically suitable process for recovering fibres from reinforced plastic waste that may also contain other types of materials (wood, foam, lacquer, etc.), such as wind turbine blades at the end of their useful life. The economic profitability of the pyrolysis recycling process depends mainly on the value of the recovered fibres, since pyrolysis liquids currently have no industrial application (and are therefore hazardous waste) and the gases are usually used to partially supply the energy requirements of the process, which is endothermic. Given that the wind turbine blades currently being retired are mainly made of glass fibres, which have low economic value, the profitability of the pyrolysis recycling process for this type of blade is a critical issue. This paper presents an analysis of the increase in the profitability of a wind turbine blade pyrolysis process that includes a treatment stage to improve the properties of the liquid and gaseous products. To this end, the investment required for this treatment (additional process units) has been defined and the energy costs and liquid waste management costs have been quantified in scenarios with and without treatment, including in the latter case the income from the sale of hydrogen. With this information and the amortisation expense, the incremental income statements derived from carrying out the treatment have been prepared, obtaining the net cash flows (NCF). The NCF has been used to calculate the net present value (NPV) of the investment project, as this is the best criterion from a financial point of view for evaluating a project. Finally, a sensitivity analysis was performed taking into account deviations in the investment to be made, income and costs. The results show that the cost of managing liquid waste is the parameter with the greatest influence on profitability, meaning that implementing the treatment increases the profitability of the recycling process.

Abstract

This chapter describes the physical-chemical properties and market options of pyrolysis oils and pyrolysis gases coming from residual fiber-reinforced plastic materials. The description focuses on the pyrolysis products generated from the two predominant types of resin in these materials, i.e. epoxy and unsaturated polyester, from both production and end-of-life waste. Pyrolysis oils and gases have two potential industrial applications: the petroleum refining and petrochemical industries, and the alternative fuels market, namely, refuse derived fuels (RDF). However, it can be observed throughout the chapter that the physical-chemical properties of these two products are far from the standards currently required by the industry. Finally, the state of the art of the research on the optimization possibilities of these products is presented, highlighting a successful case where the oils are eliminated and hydrogen-rich gases are generated, increasing the economic profitability of the pyrolysis processes applied to this kind of waste.

Abstract

The recycling of composites by pyrolysis is a technology still under development, and although it is beginning to be implemented, it still poses different problems to be solved to ensure its viability and profitability. Thus, key aspects such as the high energy consumption of the process, the search for commercial outlets for secondary products, as well as maximising the value of the main products, understood as the reinforcement fibres of the composite itself, must be tackled. Regarding the reduction of energy consumption, AIMPLAS is working on the use of microwave radiation as a more efficient source of energy than convection heating, studying the possibility of reducing the temperature of the process, analysing the effect of this radiation on the quality of the fibres obtained and the final mass balance of the different fractions. Additionally, AIMPLAS has worked on the study of the application of sizings, mainly in carbon fibres. AIMPLAS is working on the development of new products and the optimisation of the application method to obtain short fibres coated with sizings, showing the improvement in the mechanical properties of the final composite due to a better interaction with the resin.