Report Efficiency: Over 85 % of the mass of plastic converted to hydrocarbon product Advantages: High conversion efficiency, the technology is scalable, controllable reaction, process flexibility, and does not generate toxic products. Disadvantages: Does not mention specifically thermoset materials Case study ReNew ELP is the first commercial-scale HydroPRS site, already under construction, with an annual capacity of 80,000 tonnes on completion. Companies: ReNew ELP Location: Teesside, North East England Input material: End-of-life plastic Output material: Naphtha, distillate gas oil, heavy gas oil, heavy wax residue Objective: Recycle all kinds of plastics Methods: N/A Results: N/A Additional information: HydroPRS process breaks down the long-chain hydrocarbons and donates hydrogen to produce shorterchain, stable hydrocarbon products for sale to the petrochemical industry for use in the production of new plastic and other materials. The use of supercritical water provides an organic solvent, a source of hydrogen to complete the broken chemical chains, a means of rapid heating, avoiding excessive temperatures that would lead to excessive cracking, and a scalable process. This helps to create a circular economy for plastic by diverting those materials that cannot be recycled via traditional means away from landfills and incineration and into recycling, thus reducing unnecessary single-use plastics and reducing carbon emissions. Additional insight taken from the interview with Sudhin Datta The most important classical thermosets that are recyclable are polyurethanes, epoxies, and silicones. Additionally, there are materials which behave like thermosets in the recycling process, such as PVC, Teflon, and PEX, cross-linked polyethylene. The three classical thermosets are recycled for different purposes: • Polyurethanes are recycled because there is a very large volume in the world in the low-density form. There is inherent value in the materials that come out of polyurethane recycling, and the process only takes a couple of hours. It is not being done in North America and Western Europe, as the companies in such regions would much rather export that waste polyurethane foam to lower cost countries in Asia. • Epoxies have inherently no value, but reinforced epoxies are recycled for carbon fibre recovery, which are 10 times more expensive than the epoxy itself. • Silicones are recycled because silicone monomers are very expensive. Other materials face more economic barriers, such as Teflon and PVC: • Thermal recycling turns Teflon and PVC into dark intractable solids while releasing toxic acid gases which damage the equipment. • Teflon recycling is hampered because typically it is present in small quantities by weight and recovering and recycling is economically unjustifiable. • Typical PVC pipes for city water are composed of filled PVCs. So whatever recycling process should first remove the filler, which is a toxic waste that corresponds to around 40 % of the volume. The recycling processes are usually not disclosed by the companies, but they can be understood based on their chemistries: Polyurethanes Chemical structure of polyurethanes Polyurethanes are soaked, and then a glycolysis process is carried out by heating up ethylene glycol (at around 280°C) for about four or five hours and breaking the big molecules down to smaller molecules, which can be distilled and recovered. It is claimed a 95 % efficiency of whatever output material as free monomers. The process is fairly well understood. Epoxies Chemical structure of the epoxide group, a reactive functional group present in all epoxy resins. Reinforced epoxies are recycled via alcoholysis, or there is typically a catalyzed degradation of the process. The epoxies come off and the catalyst is washed off, so the carbon fibres are recovered. The chemistry is well understood, but there is some work to be done to understand the catalyst. Silicones Silicones are recycled in a similar way to polyurethanes, but the molecules are broken down to polydimethylsiloxane (PDMS). Chemical structure of silicones (PDMS) The full report is available from the website. AT www.prescouter.com/inquiry/recyclingof-thermoset-materials/ 58 bioplastics MAGAZINE [03/22] Vol. 17
Bioeconomy is not alone From Bioeconomy to Carbon Management The bioeconomy faces great expectations and hopes in the fight against climate change, and at the same time is viewed critically. The biggest problems in building a strong bioeconomy are direct and indirect land-use changes, which have significant impacts on biodiversity, climate change, and food security. What could be a solution here? The most prevalent approach is to develop comprehensive sustainability indicator systems to identify the consequences of land use changes. But so far, it has proven very difficult to develop consistent and harmonised systems that are also applicable. Especially because dilemmas arise when such indicators intrinsically oppose each other. Apart from this, the Renewable Energy Directive (RED) in Europe led to the development and establishment of various biomass certifications on the market that also request compliance with sustainability criteria. However, the application of strict sustainability criteria for biomass also means that not enough biomass can be used to replace the fossil feedstock, which in turn has significant impacts on climate protection, biodiversity, and food security. Nevertheless, there is a completely new and surprising solution, an out of the bio-box thinking, by expanding the frame of reference. The bioeconomy has never been an end in and by itself, it has never been propagated for its own sake. Rather, the bioeconomy was promoted to help reduce greenhouse gas (GHG) emissions in the areas of fuels, chemicals, and materials by replacing the fossil economy. The carbon needed for these sectors should then no longer be taken from fossil sources in the ground, but instead through plants straight from the atmosphere. Over the past decade, however, it has become clear that the bioeconomy cannot achieve this without seriously compromising food security and biodiversity. For this reason, we also see a European bioeconomy policy that acts very cautiously and focuses primarily on biogenic waste streams. Fortunately, new technologies have been developed in the last ten years that represent further alternatives to fossil carbon. In the transportation sector, electric mobility and hydrogen fuel cells are promising options for future mobility. For the chemical and material industries, CO 2 utilisation (Carbon Capture and Utilisation (CCU)) and plastic waste recycling represent significant alternative carbon streams that can and already do substitute additional fossil carbon. The bioeconomy is no longer alone. Together, all three renewable carbon sources – biomass, CO 2 utilisation, and recycling – can replace the entire fossil system. With the introduction of chemical recycling, the limitations of mechanical recycling can be overcome so that almost all waste streams can be used as a carbon source. The use of CO 2 , with the help of green hydrogen from renewable energy sources, brings significant advantages over biomass due to considerably higher land efficiency and the option to utilise non-arable land such as deserts. This can substantially reduce the pressure on natural ecosystems. Finally, CO 2 use fits perfectly with the emerging hydrogen economy. So, the question on how to deal with sustainable tradeoffs of the bioeconomy has a surprising answer: expand the reference system to all alternative carbon sources. A new, comprehensive strategy for sustainable chemicals and materials must include the long-term carbon demand that still exists after the extensive decarbonisation of the energy sector. Furthermore, it needs to show how this carbon demand can be covered in the most sustainable way possible – and what role the bioeconomy will play in this, in different regions, for different applications and technologies. Most certainly, the bioeconomy will continue to play an important role, short as well as long term. There will always be biogenic material flows that can only be used outside the food sector. There will be areas that can produce additional biomass without any competition with the food supply. There will be special fine chemical molecules that can be best produced from biomass. And in addition to thermo-chemical and chemical-catalytic processes, biotechnology including synthetic biology will continue to develop rapidly and make the use of biomass ever more efficiently. Biotechnology is not limited to biomass but will also play an important role in CO 2 utilisation and enzymatic recycling. Carbon management By expanding the reference system, we properly integrate the bioeconomy into a long-term strategy for future carbon demand in the material sector. This facilitates what we call carbon management, which is an overarching challenge of the future and could serve as an excellent framework for constructive discussions between all stakeholders. What is the longterm carbon demand of chemicals and materials after the energy sector has been largely decarbonised? And how can this demand be met as sustainably as possible, including all alternative carbon sources? What is required here is an overarching carbon management strategy that also takes specific regional and application-related features into account. Which simultaneously applies the same sustainability requirements to all renewable carbon streams. Such a strategy does not yet exist, but it is indispensable if we want to shift towards renewable chemicals, materials, and products. This is the only way to develop a realistic strategy to completely substitute fossil carbon and thus tackle the climate problem at its root. www.nova-institute.com | www.renewable-carbon.eu/publications/ By: Michael Carus nova-Institut Hürth, Germany Renewable Carbon bioplastics MAGAZINE [01/22] Vol. 17 59
