While traditional resources are becoming scarce, the wastes these resources eventually become are leading to serious pollution problems in the atmosphere, land and seas. Waste valorization is becoming more popular but it is mostly small scale and with low efficiency. The most chemically interesting of the large volume wastes includes forestry and agricultural by-products, and many industrial wastes. Current waste valorization is largely limited to simple recycling and anaerobic digestion for bio-wastes. However, these renewable resources can form the basis of future waste valorisation plants including bio-refineries that can make a wide range of chemical, material and energy products. To fully exploit the concept and make it widely useful while maintaining environmental advantage, we need to use Green Chemistry to ensure that future processes using, and products from waste are genuinely green and sustainable. Green chemical technologies that can convert waste streams into valuable chemicals include low-temperature microwave processing and benign solvent extraction. The integration of thermo-chemical and bio-chemical technologies will also become increasingly important as we seek to increase the efficiency of biomass conversion and develop efficient chemistry on fermentation broths. In this way we have shown that microwave pre-treatment of biomass substantially increases the yield of fermentable sugars.
These processes can produce bio-based platform molecules which in turn can be used to make many new green bio-based products. Countries including the UK are beginning to identify their priority platform molecules that can form the basis of new green and sustainable supply chains. For example the new bio-based solvent cyrene, can easily be made from the platform molecule levoglucosenone which is made in one catalytic step the woody waste in paper and pulp mills. Cyrene is already commercially available and its invention has led to international awards.
New solvents and many other new “green” chemicals are becoming essential as increasing legislation adds to pressures to replace hazardous substances. We need new strategies to find greener replacements including our in silico approaches to help refine the list of potential candidates. In this way we are able both to identify likely replacements for a toxic chemical and target the most likely applications for new greener chemicals. Two solvent-related examples will be used to illustrate this strategy: finding a safe alternative for toluene in some polymerisations and selecting the best bio-based solvent for the manufacture of graphene.
Discovering the best green and sustainable solvents for the manufacture of graphene
James Clark is Professor of Chemistry at the University of York, and is Founding Director of the Green Chemistry Centre of Excellence and the Bio-renewables Development Centre. He was recently appointed as a Chair Professor at Fudan University in China where he was previously a Fudan Fellow. He holds Visiting Professorships in South Africa and China. He started the award-winning company Starbons Ltd and he is now involved in commercialisation of other green technologies not only in the UK but also in Brazil and China. He was founding scientific editor of the world-leading journal Green Chemistry and started the Green Chemistry Network (more recently the Global Green Chemistry Centres, G2C2). He is now editor-in-chief for the RSC Green Chemistry book series. His research involves the application of green chemical technologies to waste or low value feedstocks notably biomass so as to create new green and sustainable supply chains for chemical and material products. In this way he has led on projects that have resulted in new commercial bio-based solvents and materials. His research work and his work on education has led to numerous awards including Honorary Doctorates from universities in Belgium, Germany and Sweden as well as prizes from the RSC, SCI, ACS and EU. In 2018 he won the RSC Green Chemistry Prize. He has published over 500 articles (h index 72) and written or edited over 20 books.