Chemistry for the Environment
University of Exeter
l.newsome@exeter.ac.uk
ECG Bulletin January 2022
Theme 1: Carbon capture
The event commenced with a talk by Professor Colin Snape FRSE (University of Nottingham) on “Adsorbents for CO2 capture: the challenges and the pitfalls regarding scale-up”. Although new CO2 capture technologies with novel materials are demonstrated in laboratory conditions, many fail to deal with the challenges associated with scale-up, such as chemical and physical stability, minimising adsorbent replacement costs, and dealing with moisture co-adsorption. Any new materials that adsorb CO2 need, as well as good sorption properties, to account for cost, durability, stability, and kinetics before they can move to pilot scale. The only large-scale demonstration to date has been at the Hadong power station in South Korea, using potassium carbonate-bicarbonate. This, however, requires high regeneration energy, limiting its potential for commercialisation. The talk explained how amine scrubbing is the most mature technology for separating CO2, but the relatively high costs mean alternative technologies are being sought, such as silica-polyethylenimine, and activated carbons. Professor Snape found treating activated carbon with KOH can double the adsorption capacity. His team also synthesised a successful ultra-microporous CO2 adsorbent from polyisocyanurate resins (but this has issues with moisture adsorption).
Following this, Professor Christopher M. Rayner FRSC (University of Leeds) talked about “Carbon dioxide capture chemistry – from laboratory to power station, and beyond”. Here, he described C-Capture Ltd., a company spun out of the University of Leeds in 2009, which developed a new approach for separating CO2 from large point source emitters. The company is unique in its focus on chemistry rather than engineering. C-Capture have been developing adsorbents based on amines, which present major challenges, particularly with respect to their own environmental impact. Steam use is important, and less is better when it comes to the amount required to regenerate the amines. Carbon capture technology has a 40% lower parasitic load, and lower energy penalty, as well as low corrosivity, minimal environmental impact, and very low degradation rates. This has been scaled up from the lab (~g CO2/day) to a bioenergy demonstrator plant (~1 tonne CO2/day), with C-Capture collaborating with Drax power station.
“CO2 utilisation: driving a renaissance in the chemicals sector” was given by Professor Peter Styring FRSC (University of Sheffield). Whilst it is possible to capture CO2 from large anthropogenic CO2 point sources and convert it to useful products, this process is currently expensive. However, diminishing costs over time are expected to help us towards a circular economy. Products made from CO2 are already available and include vodka, hand sanitiser, and synthetic petrol from flue gas (1-butan-ol). Another promising possibility is upgrading of biogas, where CO2 is removed from the mix by precipitating it as CaCO3, leaving a useful methane product.
The panel comprised Kathy Page (Environment, Science Policy Unit at Royal Society of Chemistry), Dominic Falcão (Deep Science Ventures), Gael Gobaille-Shaw (Chief Mission Zero Technologies and Supercritical Solutions) and Sam Olof (Science Creates Venture). The discussion covered entrepreneurial careers and the need for more electrochemical training. The panel agreed that the next ten years will be crucial for making significant changes to save our environment. Key tasks include sustainable aviation fuel, and energy storage. Due to an innovation gap to achieve the transition to net zero – something that policy makers are not necessarily aware of – we are not yet at the stage where scale-up of technologies is the only issue.
Dr Miriam Ribul (Royal College of Art) spoke on “Multi-stakeholder material systems: designing with materials in 2021”. Dr Ribul introduced life cycle analysis, and how it is ideal to obtain multiple reuses of an individual product. As such, new materials should be designed with recycling in mind, including downcycling, where the recycled material is of lower quality and functionality than the original, e.g. fabrics for insulation. Her research explores how to convert bio-based waste-derived feedstock into polymers to produce textiles for a circular economy. Dr Ribul and colleagues have produced novel, high-performance biocelluose composites, including a paper-like material from waste. Bio-based recycling complements physical and chemical techniques.
This was followed by “Engineering natural enzymes for the circular recycling of plastics” by Professor John McGeehan FRSB FRSC (University of Portsmouth). His team discovered an enzyme, PETase, that can digest PET polymers. Crucially, this enzyme can be engineered. To achieve this, samples from two natural environments were collected. The first sample consisted of gribble worms from Southend pier: these creatures produce enzymes that degrade the lignocellulose wood supports into organic acids. For the second, microbes were harvested from South East Asia mangrove root systems. Professor McGeehan’s team buried plastics in order to harvest bacteria. It was found that the PETase has similarities to another enzyme, cutinase, which breaks down waxy coatings on leaves, e.g. in mangroves. Professor McGeehan is now searching for more thermotolerant enzymes and working with GlaxoSmithKline to scale up production.
The final session began with “Metal pollution from mining: challenges and opportunities” by Professor Karen Hudson-Edwards (University of Exeter). She explained how we need metals for green technologies (phones, bikes, electric cars, etc.). As, currently, not enough of these are recycled, we turn to mining to meet demand. Mining, in turn, produces wastes, metal pollution, and harms the environment through tailings dam failures. Ongoing research is looking at minerals in mine wastes, how plants adapt to metal pollution, new sustainable ways for recovering metals with green solvents, microorganisms, and how life cycle analysis can improve sustainability.
The final talk, given by Professor Bhaskar Sen Gupta OBE (Heriot-Watt University), was on “Solar powered, chemical, and waste-free arsenic removal system for community-level water treatment”. Arsenic contamination was first noticed in the 1970s, and was linked to the development of a hybrid rice variety that increased yield but demanded much more fertiliser and groundwater. The mitigation technology he developed is simple: it involves pumping water to the surface, mixing it with oxygen, then returning it to ground, where additional O2 supports As(III)- and Fe(II)-oxidising bacteria to precipitate Fe(III) minerals that sorb aqueous As(V). These pumps are solar powered and have been used in Cambodia, Malaysia, Bangladesh, and Mexico.
Finally, the speakers joined together to highlight challenges that are common to all environmental issues and to share best practices for overcoming them. Interacting with politicians was one of the items discussed – to do so successfully, the scientific message needs to be related in clear and simple language, and focused towards the main political interest (which is almost always economics). If working in other countries, it is also essential to have a local partner to understand the issues and the bigger picture (e.g. local conditions, byproducts available). In order to achieve success for the environment, we should work with a range of people from companies to environmental groups – and having an independent life cycle analysis really supports getting buy-in from a diverse range of parties.
Francis Lister, Mary K. Phillips-Jones, Klaus Rumple (RSC Biotechnology Group), Laura Newsome (RSC Environmental Chemistry Group) and Ben Reeve.