BY DAVID BOTT

Science is hard work. Understanding the world around us well enough to predict the behaviour of everything from sub-atomic particles to planets requires insight, patience, imagination and rigour. But science also lays the foundations of many of the industries that have changed our world – from pharmaceuticals to airplanes.

It is this application of science to address societal challenges that benefits people. And one of the biggest challenges is moving away from using virgin fossil carbon to feed the chemical supply chain!

It is worth stating at this point that, as we have talked about this work, we meet many people who do not understand how the chemistry using industries underpin other supply chains. We have had to explain many times to disbelieving audiences that cleaning products are currently mostly made from oil!

At the moment, the many branches of the chemistry using supply chains start with about 2.6 billion tonnes of carbon dioxide equivalent produced from oil and gas extracted from the fossil reserves (about 5-6% of the carbon extracted annually goes into this use). There are other sources of carbon and the science to use them is proven, but we need to start development and implementation. This means designing and building manufacturing capacity that operates efficiently to produce the volume of material needed to satisfy the current and future market needs – and this is a lot!

Technology, Development, Innovation – whatever you call the process of turning science into products is also hard, but in a different way. Something may be scientifically possible, but to make a product out of it for less than the price people will pay for it and at a volume that all the people that want it will be satisfied can be difficult. And competing with an established route where the feedstocks are cheap and easily available, and the processes have been optimised and scaled over decades, requires tenacity.

Flue2Chem is an Innovate UK funded consortium of 16 organisations that could make up a wholly new supply that produces the materials we currently use at a large scale but without starting from virgin fossil carbon. Rather than trying to do everything all at once, it is focused on a single product – a surfactant that is widely used in a range of cleaning products. It is one way to re-imagine the future of those parts of chemistry based industries that currently use virgin fossil carbon as a feedstock. The project is focused on demonstrating that carbon dioxide can be collected from flue gases and, by a series of chemical steps, turned into that common surfactant. Although it is focused on a single product, the processes and the learning from scaling them up could be applied more widely.

Flue2Chem consortium members

The challenge of scaling-up

Making a lot of anything usually involves making it in a large factory – and the more product needed to satisfy the market demand, the larger the factory. We are mainly talking about chemistry here, so the core manufacturing unit is a reactor. In the laboratory, most people think that chemistry is done in test tubes, but the truth is that the most common reaction vessel is probably a sub 1 litre round-bottomed flask. This is where the science of the basic reactions is tested and optimised. The next step is then a vessel between 5 and 25 litres in size. This is where we first encounter scaling laws! If we make a reaction vessel which is twice as big in the linear sense, it has 8 (23) times the volume and 4 (22) times the surface area. Most chemical reactions involve either the absorption or emission of heat – the amount of heat (absorbed or generated) increases with the volume of the reaction, but the heat must move through the walls of the vessel. So, a reactor three times as big (the 1 litre to 25 litre example above) generates or absorbs 27 times the heat but it must move through 9 times the surface area. The reactor surfaces must be three times as thermally conductive to allow this. The 25 litre flask is often exactly the same design and made of the same material as the 1 litre flask, so this does not happen!

Given that chemical reactors can have a capacity up to 1,000,000 litres these are substantial size differentials! Here the ratio between the initial reactor and the final, at-scale reactor means the challenges for this simplest reaction parameter must change 1000 times.

And thermal management is not the only challenge. Mixing also requires more energy at larger scales; removing the by-products of the reaction is also more problematic as reactor size increases.

But working at large scale has some commercial advantages – the cost of capital equipment needed usually scales at a lower rate than the science gets hard, and the complexity of the ancillary equipment can also be optimised, making larger factories more commercially attractive. Since big factories are often more commercially attractive, the technological challenges have been worked on for decades and large reactors for the currently used reactions are well optimised!

This optimisation, or scaling-up of the process nearly always goes in steps, and the size of those steps depends on the confidence of those in charge! These days, a lot of these steps can be carried out using computer based process software – decades of scaling things up has given industry experience of and insight into the critical factors that need to be considered, but moving to new reactions means the basic information must be measured again!

And this is just to get it to work!

But how big should you make it? An important factor in determining the size of the reactor is the size of the market – and therefore how much product you need to make.

So, how much do we need to make to prove this new supply chain will work?

For most people, the scale of the chemistry based industries are not even recognised, let alone considered.

At present the petrochemicals industry, which provide the bulk of feedstocks to the chemistry based industries globally uses about 2.6 billion tonnes of carbon dioxide equivalent a year. To give an idea of scale, if all that was made into polyethylene (commonly used in packaging, toys and cars) it would be a cube just under a kilometre along each length.

As already described, the target molecule of Flue2Chem is a simple surfactant with a chain of 12 carbon atoms as the oleophilic (the bit that attaches to the dirt) end and 5 to 7 ethoxy units as the hydrophilic (the bit that dissolves in the water) end. It is widely used for all sorts of cleaning products – globally figures of around 17,600,000 tonnes a year are quoted. This is equivalent to about 44,000,000 tonnes of carbon dioxide equivalent – so about 1.7% of the global petrochemicals market! What sounds a lot rapidly becomes small when you look at the actual numbers!

And how is it playing out for the Flue2Chem supply chain?

When we started the project, we had two carbon capture streams – an established liquid based system capable of collecting 10 tonnes/day and a start-up solid state system with a capacity of 1 tonne/day. Given that we also had three sites from which to capture carbon dioxide and the plan was to run each for 30 days, that would have given us an input of just under a 1000 tonnes of carbon dioxide.

At the other end of the supply chain, the final assembly of the surfactant could be carried out at about 1000 tonnes and the consumer products companies could use all that output to carry out test marketing of at least three products.

We rapidly discovered that the bottleneck would be the chemistry to turn carbon dioxide into ethylene oxide (for the hydrophilic end of the surfactant) and dodecanol (for the oleophilic end). The thermo-catalytic routes might be able to make about a kilogramme of the ethylene oxide and probably much less of the dodecanol. And on the biotechnology side of the options, although there were companies making ethanol (a precursor to ethylene oxide) from flue gases, they were not using carbon dioxide as the source. Biotechnology routes are often attractive because they make a single product, but using the biobased route to dodecanol looks like it would be hard to make even a kilogramme.

This would give us a few problems, but as the project progressed, we ran into another challenge. The company with the liquid system decided to withdraw from active carbon capture in the UK (the subject of a later blog), and one of the carbon sources got a government grant to radically overhaul their plant to drastically lessen the amount of carbon dioxide they might produce, so they have “paused” their direct involvement in that part of the project. We had now gone from a capacity of 990 tonnes to 60 tonnes. This was still more than enough to keep the chemists happy, but it gave us another opportunity to be innovative. The two carbon dioxide sources were in Cumbria and North Ayrshire, but the chemistry to convert it was being carried out in Sheffield and Germany and the biology in North Yorkshire. How could we transport that amount of carbon dioxide? At about 1000 tonnes, it might have been possible to “rent” a bottling facility and install it at the capture sites. At less than 100 tonnes, the equipment did not even exist! The solution we are adopting is to pressurise about 3 kilogrammes of carbon dioxide in pressure vessels and transport it from site to site. This limit on how much carbon dioxide we can transport from the emitters to the converters puts another size restriction in place, so a sizable fraction of the carbon dioxide we capture will have to go back into the flue! This is not ideal, but given the goal is to validate a wholly new, more sustainable supply chain and the lack of any other options, we don't have much choice.

There will be more…

Stepping stones to wisdom – what have we learned?

Perhaps we should have checked our numbers before we submitted the proposal, but since any scale-up project is designed to see how difficult it is to scale-up, discovering that there are issues beyond the technological is good learning.

The chemical and biological restrictions are a result of the lack for scale-up facilities in the UK, and we currently have no other options. If we are to develop the new chemistries required to switch feedstocks away from virgin fossil carbon to carbon dioxide, waste biomass or recycled plastics and oils, we will need several levels of scale beyond those currently available.

Underpinning this last point is the fact that many do not understand how the chemistry using industries underpin other supply chains – even their own. We have had to explain the range of products made from virgin fossil carbon (IEA figures are plastics packaging 36%, upholstery, carpets and paints 16%, textiles 15%, home and personal car products 10%, pharmaceutical and agricultural products 11%, car interiors and tyres 7% and electrical 4%) many times and often find ourselves trying to convince disbelieving audiences that cleaning products are currently made from oil! This means that many in government do not see the need to invest at the national scale in them in a coordinated manner. Scaling-up chemistry is generally not well catered for.

Written by David Bott, Director of Innovation at SCI and originally published on Linkedin