Pure & sustainable: High-end circular solvents
Submitted by:
Andrew Warmington
The term 'solvent' is applied to a large number of chemical products that are used to dissolve or dilute other substances or materials. Many solvents are used as chemical intermediates, fuels, and as components of a wide range of products.
In fact, it seems fair to say that industrial solvents are somewhat ubiquitous, being used in the manufacture of a vast range of products, from pharmaceuticals and agrochemicals to batteries, microelectronics, the automotive industry and more. Solvents are usually organic liquids, although industrial solvents are often mixtures of several individual substances, and they can be found under a variety of trade names.
Disposal risks
Most leftover or used solvents are considered hazardous materials, and their improper disposal can lead to significant environmental contamination, including soil and water pollution, air pollution from volatile organic compounds (VOCs), and potential health risks to humans and wildlife.
As a result, the disposal of used solvents has become increasingly regulated, and failing to comply with disposal regulations can come at a very large cost. In the UK, fines for the illegal storage of hazardous materials such as used solvents has seen companies fined £1 million or more.
Fortunately, most current-day companies dispose of their leftover or used solvents properly and responsibly. This is a good outcome, but proper disposal of hazardous materials is expensive, and companies find themselves in a constant cycle of buying and transporting new solvents, just to use them, dispose of them, and then buy more new ones again. Surely, in our modern world of technological advances, there must be a better, more efficient and sustainable way.
Sustainable solutions
In fact, solvents lend themselves well to a circular economy. Solvent recovery processes extract pre-used solvents from industrial streams, so they can be used again - and again, and again.
Using current technologies, companies can typically expect to recover up to 95% of used solvents, even from more complex mixtures. It is possible to recover and recycle industrial solvents with the purity and quality of new virgin materials. In fact, in terms of quality and purity, most recovered solvents are indistinguishable from virgin solvents and they can be used for any solvent applications.
Solvent recovery improves process efficiency, saves costs and simplifies the supply chain by eliminating the need to constantly purchase new solvents. Furthermore, if the recovery is performed on-site, it significantly reduces transportation costs, as well as reducing the overall supply chain burden and removing the need for expensive disposal procedures.
Modern technologies enable the recovery of very complex solvents and they are presenting solutions to contemporary global issues. For example, the rapid growth of the electric vehicle market has created a booming battery industry. The manufacture of batteries requires large quantities of solvents such as N-methyl pyrrolidone (NMP) for coating the electrodes. Conventionally, NMP recovery has been impractical due to the complexities and costs arising from metal contamination.
However, recent research by Indaver Solvents and the Flemish Institute for Technological Research has shown that an advanced separation technology can effectively remove these metals at a level that satisfies the strict purity standards of the battery and microelectronics industries. In fact, the recovered solvents are so pure they can even be used in the pharmaceutical industry.
This new approach not only allows for the sustainable recovery and re-use of solvents used in battery manufacture but also reduces costs and CO2 emissions. The practical, complete and safe re-use of critical substances like NMP is an important step towards full circular recycling, in which materials are not just reused but even given higher value.
Solutions at all scales
The goal is to provide solutions that are available, affordable and reliable. To this end, another important factor is scalability. The ability to recover solvents from even small volumes of contaminated mixtures is important, if this approach is to bring value throughout industry. In order to achieve full circular recycling, it must be possible to leverage processes that can be scaled from small quantities to full-scale manufacture.
As well as enabling companies recycle their own solvents on-site, independent solvent recovery sites facilitate the collection of even low volumes of used solvents for processing at a central point. Modern distillation and cooling columns can provide improvements in efficiencies and capacity, as well as better recovery from a wide variety of very complex industrial streams. In addition, the implementation of boiler systems that run on used lower grade, recycled solvents can significantly reduce reliance on fossil fuels and lead to a lower CO2 footprint.
Solvent recovery is usually based on multi-stage fractionation and distillation (Figure 1). Both of these processes separate components based on differences in their boiling points, with fractionation offering a more refined separation by using a fractionating column to achieve multiple vapour-liquid equilibrium stages.
These are both efficient and sustainable approaches that achieve high-purity solvent recovery. However, recent developments in available technologies are allowing companies to raise the efficiency, capacity and sustainability of their solvent recycling processes even further.
For example, a new pressure swing plant will come into commission at Indaver Solvents’ UK site in the summer of 2025. This bespoke technology is a niche offering that enables the management of highly complex mixtures, as it can break azeotropes that conventional distillation plants struggle to manage.
Pressure swing plant technology is generally more economical than the conventional methods like extractive distillation and no extra solvent is required to achieve the separation of solvent mixtures. Therefore, day-to-day use of pressure swing distillation for the separation of azeotropic mixture adds another solution to the solvent recovery sector that drive us further towards a fully circular economy.
Calculating environmental impact
The EU Green Deal highlights the need for Europe to work towards economic growth without increasing consumption of materials. Together, we need to build a more sustainable future. The sources we tap for our energy, the efficient use of raw materials, and the approaches and actions required to protect people and planet – much of this can be traced to the advance of the circular economy.
Secondary raw materials recovered from industrial streams can replace primary raw materials if the recovered materials are of good quality, and if they are as reliable and as safe as the virgin alternatives. Solvents are perfect candidates for this circular model and recycling them contributes to environmental protection and can enhance a company's green credentials – something that is becoming more and more important for investors and customers alike. The technologies involved in solvent recovery are highly scalable, making them accessible for companies of all sizes.
High-grade, low carbon solvents
By recycling solvents, companies can minimise the amounts of hazardous materials that need to be managed and disposed, while reducing the carbon footprint associated with producing and transporting new solvents. In fact, it should be possible to offer a carbon calculation for any industrial recovery project.
These calculations include a number of components, including energy and fuel efficiencies. As well as internal tools customised for specific extractions, a very useful tool for estimating carbon savings is the University of Manchester’s CCaLC (Carbon Calculations over the Life Cycle) lifecycle methodology and decision support tool for industrial users.
CCaLC calculates the carbon savings that can be made from recycling materials from industrial streams. It includes a large database of more than 6,000 items, and helps manufacturers understand and demonstrate the carbon savings made through recycling solvents and other raw materials, rather than always using virgin materials. According to a recent study performed by the University of Manchester using CCaLC, recycling solvents can save 46-92% of greenhouse gas emissions, compared with virgin solvents.
Path to sustainability & cost-efficiency
The transition from buying new solvents to practicing routine solvent recovery brings various benefits that help companies save money, simplify their supply chains and become more environmentally friendly.
Modern technologies and processes enable the recovery of increasingly complex solvents, across a range of volume scales. They also ensure that many recovered solvents are chemically indistinguishable from virgin materials, with high quality and purity being achieved as solvents are recovered exactly to their original forms.
In fact, the advantages of solvent recovery are so overwhelming – economically, practically and environmentally – surely the question is no longer why companies should be doing it, but rather, when?
We anticipate a future in which all companies embrace the principles of using their industrial streams to recover secondary raw materials and supply clean energies. Such a shift seems inevitable, as a growing and increasingly demanding global population must take heed of limited resources. A circular economy provides the only logical solution, and the sooner we embrace it, the better off we all will be.
Contact:
Stuart Barker
Commercial Manager EU & UK
Indaver Solvents
http://indaversolvents.com