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Science to enable the circular economy

Discussion meeting








The Royal Society, London, 6-9 Carlton House Terrace, London, SW1Y 5AG


Scientific discussion meeting organised by Professor Matthew Davidson, Professor Richard Catlow FRS, Professor Adrian Mulholland and Professor Graham Hutchings CBE FRS.

PETase molecules breaking down PET-plastic © selvanegra

For society to be sustainable, realising circular flows of molecules and materials will be fundamental to delivering the circular economy. This meeting brought together scientists and engineers to highlight efforts to meet the formidable challenge of 'keeping the molecules in play' by addressing important global challenges such as using waste carbon dioxide, harnessing biotechnology and eliminating plastics pollution.

Recorded audio of the presentations will be available on this page soon after the meeting has taken place. Meeting papers are available in an issue of Philosophical Transactions of the Royal Society A.

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Schedule of talks

24 June

Session 1 09:00-12:30

Fuels and chemicals for a circular economy

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Professor Graham Hutchings CBE FRS, Cardiff University, UK

09:00-09:05 Welcome by the Royal Society and Matthew Davidson

09:05-09:30 TBC

Dr Mike Muskett, BP, UK

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09:45-10:15 Manufacturing chemicals with light: any role in the circular economy?

Professor Michael George, University of Nottingham, UK

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10:30-11:00 Coffee break

11:00-11:30 The mechanisms to achieve a circular economy

Dr John Warner, CEO & President Warner Babcock, USA


The natural world is a beautiful and intricate system of intertwined and overlapping materials ecosystems. As humans, our understanding of the various interrelationships is only at the most basic level. One important reason why these naturally interdependent cyclic systems exist with exquisite complexity is because of the very fact that they all co-emerged over hundreds of thousands of years in the presence of one another. Evolutionary forces drove symbiotic relationships by selecting for and against mechanisms and materials that were conducive to the success of the entire multi-component matrix. As human society seeks to create a circular economy, we unfortunately have the disadvantage that our various industrial “species” have developed with a level of independence, essentially unaware of adjacent processes. We are forced into a position of creating connectivities that were not part of the considerations in the original design. Obviously this creates a daunting challenge. While there have been some examples of the circular economy designed and deployed in many industrial settings, the vast majority of industrial products and processes continue to exist disconnected and unsustainable over the long run. The pathway to create most of these technological ecosystems will require the inventive application of green chemistry (the molecular level mechanistic underpinnings of sustainability). Nature creates materials of such exquisite structural complexity and diversity that humans may never be able to mimic them. Nature’s elegance is even more astounding when one considers the fact that most chemistry in the biological world is carried out at ambient temperature and pressure using water, for the most part, as its reaction medium. For society to become truly sustainable, the way we manufacture, use and repurpose materials must change dramatically. This presentation will describe John Warner’s mechanistic considerations of materials design and illustrate their application through recent R&D examples from the Warner Babcock Institute for Green Chemistry. Examples from pharmaceuticals, personal care, construction materials and textiles will be included.

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11:45-12:15 Catalyst design as key elements of an efficient use of renewable carbon resources

Professor Regina Palkowits, Institut für Technische und Makromolekulare Chemie, Germany


Renewable carbon feedstocks such as biomass and CO2 present an important element of future circular economy. Especially biomass as highly functionalized feedstock provides manifold opportunities for the transformation into attractive platform chemicals. However, these resources require novel paradigms in process design. Fossil feedstocks are processed in stationary gas-phase processes at elevated temperature. On the contrary, biorefineries are based on processes in polar solvents at moderate conditions to selectively deoxygenate the polar, often thermally instable and high-boiling molecules. Considering CO2 as a resource, the selective valorization at moderate reaction conditions requires tailored catalysts joining the design criteria known from molecular and heterogeneous catalysis. With regard to “green electrons” provided by renewable energy technologies, also dynamic (electro)catalytic processes become attractive as key technology of a throughout circular economy.

Herein, novel concepts in catalyst design will be discussed focusing on solid molecular catalysts for CO2 activation, novel biomass transformations as well as the future role of a potentially electrified biorefinery. Examples comprehend: (1) the selective reduction of CO2 over solid molecular ruthenium catalysts to formic acid and the reverse reaction for hydrogen generation on demand; (2) the design of novel value chains based on biogenic carboxylic acids and (3) and electrochemical transformation of biogenic carboxylic acids to promising fuel mixture as well as monomers such as acrylate and adipic acid, respectively.

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Session 2 13:15-17:00

Polymers for a circular economy

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Professor Matthew Davidson, University of Bath, UK

13:15-13:45 Seed and microalgae oils as feedstocks for monomers and polymers

Professor Stefan Mecking, University of Konstanz, Germany


The feedstocks employed and the further fate of a material after its useful lifetime cycle are obvious decisive parameters for the overall environmental impact and feasibility of an economy. Projections suggest that while crude oil consumption for the transportation sector may reach its peak in the next two decades, demand as a feedstock for chemicals will continue to increase. This is driven by the demand for polymers, which fulfill a myriad of functions in modern technologies. An alternative renewable feedstock is plant oils, namely seed or microalgae oils. However, traditional utilizations of plant oils to generate monomer building blocks for polymers often lose a considerable amount of the feedstock as waste. This can be overcome by advanced catalytic reactions that incorporate the entire length of the feedstock’s fatty acid chains. The latter also imparts the resulting polymers' properties beneficially in that they crystallize in a polyethylene-like fashion. Unlike traditional polyethylene, they contain potential break points in the polymer chains which can enable a slow degradation and impart a desirable non-persistent nature.

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13:55-14:25 Renewability is not enough: sustainable synthesis of biomass-derived monomers and polymers

Professor Michael A R Meier, Karlsruhe Institute of Technology, Germany


In ages of depleting fossil reserves and an increasing emission of greenhouse gases, it is obvious that the utilization of renewable feedstocks is one necessary step towards a sustainable development of our future. In order to develop truly 'green' approaches, using renewable resources is insufficient. The available feedstocks rather have to be used in a sustainable fashion by combining as many of the principles of green chemistry as possible and by accessing and comparing the sustainability of chemical transformations. Within this contribution, new approaches for the synthesis of monomers as well as polymers from plant oils, lignin and carbohydrates will be discussed, thereby highlighting developed sustainable (catalytic) modification strategies. The focus of this presentation will be on novel approaches towards the functionalisation of cellulose and lignin, including new solubilisation and catalysis concepts as well as the use of multicomponent reactions.

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14:35-14:50 Tea break

14:50-15:20 Polymers as a materials system in a circular economy

Professor David Bucknall, Heriot-Watt University, UK


A huge number of polymers are known and continue to be developed. This provides a very diverse choice of properties that have led to the use of polymers in a huge range of applications. It could therefore be argued that modern society is reliant on polymers. Despite the undoubted benefits of plastics, in recent years, the negative impacts plastics are having on the environment are gathering increasing public attention, and have produced wide spread calls for bans on use of plastics and single-use plastics in particular. In the UK, these calls together with other drivers have ensured that stakeholders in the plastics economy are setting targets to achieve massive reductions in the damaging effects plastics have on the environment. A major component of this circular economy approach is a significant increase in recycling of plastics from current levels to be achieved by 2025. Whilst these targets require economic, societal and behavioural changes, there are also significant materials challenges to be overcome in order for these targets to be met. This talk will discuss the context of these materials challenges and the approaches that are in development, as well as those that still need to be solved.

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15:30-16:00 Circular economy plastics

Professor Charlotte Williams, University of Oxford, UK


Catalysis plays a central role in delivering the circular economy and is central to ensuring the future of plastics manufacturing and recycling is more sustainable. This lecture will discuss the development of selective and active catalysts and processes that deliver new classes of recyclable and/or degradable polymers. It will describe the transformation of waste by-products from existing manufacturing, such as carbon dioxide and citrus fruit peel (limonene oxide), to high performance thermoplastic elastomers, coatings or rigid plastics. It will also describe how to apply switchable catalysis to mixtures of monomers including lactide, carbon dioxide, anhydrides and epoxides to produce block sequence controlled and recyclable materials (elastomers/rigid plastics). The polymerization kinetics and selectivity will be described and a hypothesis to rationalize block enchainment from mixtures presented. Switchable polymerization catalysis will be demonstrated to be generally applicable to a range of catalysts and monomers. The lecture will close by identifying future research challenges to improve the sustainability of plastics.

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16:30-18:00 Poster session

25 June

Session 3 09:00-12:30

Biotechnology in a circular economy

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Professor Adrian Mulholland, University of Bristol, UK

09:00-09:30 Enzyme catalysed reactions for high-value applications

Professor Nicholas Turner, University of Manchester, UK


This lecture will describe recent work from our laboratory aimed at developing new biocatalysts for enantioselective organic synthesis, with emphasis on the design of in vitro and in vivo cascade processes for generating chiral pharmaceutical building blocks. By applying the principles of ‘biocatalytic retrosynthesis’ we have shown that it is increasingly possible to design new synthetic routes to target molecules in which biocatalysts are used in the key bond forming steps.

The integration of several biocatalytic transformations into multi-enzyme cascade systems, both in vitro and in vivo, will be addressed in the lecture. In this context monoamine oxidase (MAO-N) has been used in combination with other biocatalysts and chemocatalysts in order to complete a cascade of enzymatic reactions. Other engineered biocatalysts that can be used in the context of cascade reactions include w-transaminases, ammonia lyases, amine dehydrogenases, imine reductases, and artificial transfer hydrogenases. We shall also present recent work regarding the discovery of a new biocatalyst for enantioselective reductive amination and show how these enzymes can be used to carry out redox neutral amination of alcohols via ‘hydrogen borrowing’.

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09:45-10:15 Biocatalytic recycling of plastic

Professor Wolfgang Zimmermann, Leipzig University, Germany


The global production of plastics made from non-renewable fossil feedstocks has grown more than 20-fold since 1964. While more than eight billion metric tons of plastics have been produced until today, only a small fraction is currently collected for recycling and large amounts of plastic waste are ending up in landfills or in the oceans. Pollution caused by accumulating plastic waste in the environment has therefore become world-wide a very serious problem.

Synthetic polyesters such as polyethylene terephthalate (PET) have widespread use in packaging materials, beverage bottles, foams, coatings, and fibers. Recently it has been shown that amorphous PET materials can be completely hydrolyzed by microbial enzymes at mild reaction conditions in aqueous media. Due to the restricted mobility of the polymer chains at ambient temperatures, an efficient biocatalytic degradation has to be performed close to the glass transition temperature of PET of about 70°C. Thermostable enzymes like those produced by actinomycete bacteria have therefore emerged as the most promising catalysts for the hydrolysis of PET to its monomeric building blocks. In a circular economy, the resulting monomers can be recovered and reused to manufacture novel PET again or other products without depleting fossil feedstocks. The enzymatic degradation of post-consumer plastic waste thereby represents an innovative, environmentally benign, and sustainable alternative to conventional chemical recycling processes. By the construction of powerful biocatalysts employing protein engineering techniques and an optimization of the bioprocess parameters, a biocatalytic recycling of PET can be further developed towards industrial applications.

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10:30-11:00 Coffee

11:00-11:30 Biocatalysis and biomass conversion: enabling a circular economy

Professor Roger Sheldon, Delft University of Technology


Two of the grand societal and technological challenges of the twenty first century are the 'greening' of chemicals manufacture and the ongoing transition to a bio-based economy: that is a sustainable, carbon-neutral economy based on renewable biomass as the raw material. These challenges are motivated by the need to eliminate environmental degradation and mitigate climate change. Waste minimisation and waste valorisation in a circular economy constitute a point of overlap of these grand challenges. In a bio-based economy, ideally waste biomass, particularly agricultural and forestry residues and food supply chain waste, are converted to liquid fuels, commodity chemicals, and biopolymers by employing clean, catalytic processes.

Biocatalysis has the right credentials to achieve this goal. Enzymes are biocompatible (sometimes even edible), biodegradable and essentially non-hazardous. Additionally, they are derived from inexpensive renewable resources which are readily available and not subject to the large price fluctuations which undermine the long term commercial viability of catalysts derived from scarce precious metals. Moreover, thanks to spectacular advances in molecular biology the landscape of biocatalysis has dramatically changed in the last two decades. Developments in (meta)genomics in combination with 'big data' analysis have revolutionised new enzyme discovery and developments in protein engineering by directed evolution have enabled dramatic improvements in their performance. These developments have their confluence in the bio-based circular economy.

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11:45-12:15 Cleaner NADH recycling for biocatalytic chemical synthesis

Professor Kylie Vincent, University of Oxford, UK


Enzymes are powerful catalysts for selective oxidation and reduction reactions, but one of the barriers to the scale-up of biocatalysis for bulk chemical transformations is the reliance of many of these enzymes on expensive nicotinamide cofactors, NADH or NADPH. The cost and complexity of these cofactors mean that they must be continuously recycled during chemical transformations. Recycling of the reduced cofactors is typically achieved using glucose as a sacrificial oxidant (hydride donor), generating substantial carbon-based waste. This talk will explore alternative, cleaner possibilities for recycling the reduced cofactors for reductive chemical synthesis, using hydrogen gas or electrochemical processes as the reductant for NADH or NADPH. Further, we show that immobilisation of the cofactor recycling system, together with the enzyme of interest, on a solid support offers advantages for scale-up and re-use of biocatalysts in batch reactors, and possibilities for implementing biocatalysis in continuous flow reactors. Developments in these areas will be critical in enabling biocatalysis to move beyond the small-volume, fine chemicals sector so that enzymes can play a significant role in circular transformations of commodity chemicals in a sustainable future economy

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Session 4 13:30-17:00

Techno-economic, societal and environmental impacts of the circular economy

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Professor Richard Catlow FRS, University College London, UK

13:30-14:00 Environmental aspects of the circular economy

Professor Adisa Azapagic, The University of Manchester, UK


The concept of circular economy has emerged in response to the need for decoupling the economic growth from resource consumption and environmental impacts. Aiming to maximise resource efficiency, it represents an alternative to the current linear ‘take-make-use-dispose’ economic model. The circular economy concept rests on three fundamental principles: i) preserving and enhancing natural capital; i) circulating products and materials at the highest utility as long as possible; and iii) designing out negative externalities. Therefore, transitioning to a circular economy will require a systemic change across supply chains, involving both technological and business model innovations. This in turn will necessitate a whole systems approach and life cycle thinking to capture and address the complex interrelationships between different aspects of a circular economy. One of the complexities is that ‘circular’ does not necessarily mean ‘sustainable’. Hence, we need to be able to understand the full implications of a switch from the ‘linear’ to ‘circular’ economic models. Focusing on environmental impacts of that switch, this presentation will discuss how we can measure the ‘circularity’ on a life cycle basis and what that may mean in practice, considering examples in the food, energy and plastics sectors.

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14:15-14:45 Biocatalysis: we create chemistry for a sustainable future - with a little help from enzymes!

Dr Kai Baldenius, BASF SE, Germany


In the last decades the application of enzymes for enantioselective syntheses has made its way to industrial use. BASF has led this development with its Chipros® product line of chiral intermediates with a particular focus on chiral amines. However, the horizon for enzymatic catalysis is now reaching beyond pharma intermediates. Biocatalysis application reaches to volume chemicals with a much larger leverage on resource efficiency. Opportunities to combine enzyme catalysis with renewable feed-stock are even greater. A carefully balanced view on how enzyme catalysis can support a circular economy and can actually lead to a more sustainable industry will be given.

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15:00-15:30 Tea

15:30-16:00 Chemistry and catalysis: key tools for a circular economy

Professor Matthias Beller, Leibniz Institute for Catalysis, Germany


In the past two centuries, science and engineering provided the basis for the development of new technologies, which dramatically improved the life of mankind all over the world. In this respect, chemistry and catalysis significantly contributed to better health, more food, clean water, new materials and so on. Nevertheless, despite these developments, still we face significant problems in the coming years. In this context, the sustainable use of resources and especially the reduction of fossil-based feedstocks are key issues. In the talk, the importance of chemistry and specifically catalysis for achieving a circular economy will be explained. Necessary catalytic advancements will be discussed for case studies such as the valorization of carbon dioxide for fuel production and chemical synthesis. Next to this, the presentation will give some insight on the potential of nanotechnology-derived catalysts and molecularly-defined catalyst systems for sufficient and sustainable supply of energy.

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16:00-16:30 Title TBC

Sir Patrick Vallance FMedSci FRS, Government Chief Scientific Adviser and Head of Government Science and Engineering Profession, UK Government

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16:30-17:00 Panel discussion

Related events

Science to enable the circular economy

24 - 25 June 2019

The Royal Society, London 6-9 Carlton House Terrace London SW1Y 5AG UK
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