Why we need carbon
It is difficult to say exactly when the “synthetic” world started, but the huge expansion came with the use of fractions of the oil and gas we were extracting from the ground as a fuel as material feedstocks about 120 years ago. The petrochemicals supply chain now accounts for about 2.6 billion tonnes of carbon dioxide equivalent a year (about 5.7% of the carbon extracted) and is growing at about 8% a year – therefore roughly doubling every 10 years. And the products at the end of the many supply chains that start with these fossil feedstocks range from things we cannot do without (such as disinfectants, soaps, textiles for clothes and so on) to things we “like” to have but would probably fight to keep (such as cosmetics and flying)!
The focus is often on single-use plastic packaging, which makes up about 30% of that 2.6 billion tonnes. But there are many other products that depend on the same source – products for use in the home (carpets, upholstery, paint and adhesives) at about 16%, textiles (mostly for clothes) at about 15%, pharmaceuticals, agrochemicals and fertilisers at about 11%, cleaning products and cosmetics at about 10%, the interiors of cars and their tyres at about 7% and the use in electrical and electronic products (both insulation and cases) at about 4%. Such is society’s use of these products, that we cannot simply stop using them, or make them from something other than carbon. We will need a source of carbon at the same scale.
At this point in the narrative, it is worth pointing out that although many uses of fossil carbon as a fuel can be replaced by alternative technologies, aviation fuel is different. Although there are prototype electric planes for short haul flights, and visions of hydrogen powered planes at some point, the options for long haul air travel look distinctly limited – with really only Sustainable Aviation Fuel as a runner. The aviation industry would need about 1.3 billion tonnes of carbon dioxide equivalent a year to keep going at their current rate, so about half that needed to supply our material needs. It faces the same challenge as the carbon based materials – if they do not use fossil carbon, where would it come from?
Where we can get carbon from
The source that gets talked about a lot is “biomass”. At the global level, it is estimated that about 100 million tonnes of biomass is produced each year, roughly half on the land and half in the sea. This equates to roughly 200 million tonnes of carbon dioxide equivalent. Most reviews discount the marine biomass as difficult to harvest and then calculate that of the land based only about 8 million tonnes (so, 16 million of carbon dioxide equivalent) a year can be harvested “sustainably”.
Another factor often quoted is the logistical cost of harvesting, since for some crops the energy required to harvest compromises the efficiency of the process. The factor that doesn’t get talked about much is the difference between the biological building blocks and the petrochemical ones we are used to – which would require us to build a different set of supply chains and result in products with different properties.
The second source is the materials made of fossil carbon we have already extracted. There are various estimates of how much plastic is in landfills, but the average seems to be about 5 billion tonnes of plastic – about 15 billion tonnes of carbon dioxide equivalent. This would need to be chemically recycled back to feedstocks equivalent to those that underpin the current supply chains.
The third source is the carbon dioxide we have been “storing” in the atmosphere. Since the start of the industrial revolution when our emission of carbon dioxide started in earnest, we have emitted close to 2.2 trillion tonnes of carbon dioxide – half of which is in the atmosphere and the rest has partitioned into the oceans. The problem is that it is very dilute, so you would have to capture a lot of “air” to get meaningful amounts of carbon dioxide – but people are trying!
However, since we are still burning a lot of fossil fuels (and biomass) at the moment, we have flues and chimneys where the carbon dioxide concentration is many times higher. Why not start there and increase the process efficiency with experience?
However, there is a challenge with using carbon dioxide as a source for carbon-based materials. Carbon dioxide is where carbon tends to end up in an oxygen-rich environment – particularly where there is light. It is basically at the bottom of a thermodynamic well and it needs a lot of energy – and green hydrogen – to get it back to those feedstocks we need to go on making things that we want in a way that keep the cost down.
What next?
So, we have a very large problem, some options – each of which has advantages and “issues”, and it will take a long time to change our supply chains, so we need to act fairly quickly before our filling the atmosphere with carbon dioxide does irreparable damage to our environment. We need a plan…
Written by David Bott, Director of Innovation at SCI and originally published on Linkedin
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