CO2 to X summary of approaches and research

Ian Page -2023.12.27

Some recent papers indicate that a lot of research is trying to navigate a rather complex space, essentially to come up with answers to the critical issue of how civilization reduces the concentration of CO2 in the air from 400+ppm to 300 to avoid the worst effects of climate disaster.

 

The diagram indicates the major components which I will discuss, but the key overall measures are: 

%C   

How much of the expensively captured CO2 is converted to either permanently sequestered carbon which reduces the concentration of CO2, or something that replaces oil and gas extraction which reduces the annual addition of CO2 to the environment. Losses of C along the way may appear to be small but will tend to end up as CO2 again, or large quantities of some material that must be disposed of.

e  

How large an increase in generated electricity worldwide is needed to drive the systems. I have recently pointed out from a paper that this could involve multiples of the current world energy production.

$  

How much will it cost in capital, labor, etc.  Again, a recent paper proposed figures of the order   of world GDP. for current approaches.

land 

The scale of any operation that makes a difference will be vast- possibly of the order of the land used for agriculture or silviculture using some approaches.

We must start by dispelling some assumptions.

1. CO2 capture is not a new technology- you probably did it in science at school when you blew into a solution of calcium hydroxide and saw a cloud of calcium carbonate appear. It's been used for many years by the oil industry to clean up gas, Plants have been doing it for eons on a huge scale. 
2. Most if not all carbon capture "research" and prototypes are basically greenwashed by oil companies to get subsidies to do things that actually increase oil output.
3. There is no magic bullet or new fundamental technology that will dramatically change things. There is however a lot of research that can improve things to various degrees and given the scale of the issue, a 10% or more improvement saves the GDP of many significant countries.
4. Many of the steps on my diagram are feasible or already done often at an industrial scale in some form today. - although by different routes, to different extents, and for different reasons. - they usually have reaction names from famous chemists of the past.

Thus, the issue is to find innovative ways of minimizing the key overall parameters of C, e, $, and Land, much of this will be beyond the basic technology and will be found in technology scale, infrastructure, and hybridization.

Capture:

This fundamentally is defined by the quantity of wind that has to be passed over or through some absorbent, and the energy needed to regenerate it to CO2 for the industrial approach, or the amount of land, water, and cropping needed for the natural approach.

Capture by bubbling air through some capture solution will involve pumps. Capture by allowing air to blow over sheets of absorbent plastic uses less energy as you only need to move the plastic ribbon on an endless belt slowly to the regenerating section, which could be simple heating (have some iron in the plastic and microwave it), or use solar heating during the day, and absorption at night. Notably the lower energy processes are slower, and because the regeneration energy needs to be minimized ( unless it's free like sunlight, or overproduced wind) only a property of the CO2 will be captured ( you can easily capture nearly 100% by using a vicious chemical like potassium hydroxide but this will need high temperatures to regenerate it) The gentle amine process captures a much lower proportion. This may however not matter. While capturing Co2 from smokestacks where the concentration of Co2 is high and drives the capture equilibrium, you only get one chance to capture it. If you are just using the natural wind, the portion captured is not so critical since the wind is always there.

Nature in some newer plants uses a cunning system of concentrating the CO2 by one process before passing it to photosynthesis. This costs more but reduces the losses from oxygen poisoning in a photosynthetic process.

The easiest to scale is probably the natural system, although following the infrastructure considerations I outlined in previous papers, there is a limited amount of parasitism potential before new land resources need to be developed on land that is not currently agri or silvi-cultured.

A recent innovation is macroalgae culture. The concept is to grow it on wires in a large circle during the day and lower it into the depths at night to pick up nutrients. (Global warming has increased the tendency of surface layers to stay separate from deeper layers thus they rapidly become deprived of nutrients.) The algae grow about 3X as fast as normal with this process. About 25% falls off and drops into the depths where there is no oxygen. They will then either be sequestered in the abyssal mud or possibly turn into methane which will generally be eaten by bacteria. Lots of questions to be investigated, but the concept does not use the ocean that otherwise is being used for fish or may actually increase fish yields. It's thus highly scalable.

The biological route leads to sugars, fats, and lignins. All of these have chemical routes to useful substances that are either independent of the petrochemical industry or displace petrochemical inputs or products.  Since petrochemicals don’t have to pay for the CO2 they create in their use or disposal, or for cleaning up the non-degradable effects, the biological route is generally financially disadvantaged. For example, sugars turn to alcohol by yeast and brewing but this is generally more expensive than making alcohol from ethane in natural gas. However if you note that the CO2 in natural alcohol comes from the air and balances the CO2 released when the alcohol is burnt in a car say, and the alcohol from fossils is a net gain for CO2 emissions, we note that this is purely a mistake caused by incorrect pricing. It will be far cheaper to not release the fossil CO2 and then have to capture it than to not produce it in the first place.

CO2 conversion

The industrial CO2 route leads to CO2 in pipes or cylinders and there is a great deal of research discussion over whether it's better to convert CO2 directly to useful fossil replacing products (CO2RR) or to use a catalytic process to strip an oxygen off making a far more reactive CO and then convert this electrolytically to (CORR) products. Both paths are being actively developed. The CO2RR path involves powerful alkalis and may be merged with the powerful alkali capture path but has issues with loss of C to non-useful products. There are some very clever electrolytic cell concepts that capture and recycle the lost CO2. currently achieving a high %C but also high energy and must run fairly slowly to allow the various reactions to happen as desired.  

The CO route has recently been improved (at least in research) dramatically by using a catalyst support that absorbs and concentrates the CO overcoming the depletion at the catalyst that normally happens at high throughput. They Have achieved long-lasting operation at 1000 ma/cm2 which is several times what would be acceptable industrially, with high energy efficiency and low side emission of hydrogen.

Thus, at present both pathways are being improved by cunning approaches. approaching or passing industrially acceptable levels. 

Substitution

How much of the existing petrochemical industry do we need to replace directly at the feedstock level, and how much at the end product level.  

Before 1800 chemistry and chemical products were mainly obtained by processing natural products e.g. methyl alcohol has an old name "wood alcohol”, and turpentine, caffeine, and vanilla.

Once coal became a thing, chemists worked out what they could best make of the chemical that came with it, leading to town gas (natural gas plus 50% carbon monoxide), mothballs, benzene, and all the aromatics and dyestuffs.

Oil arrived leading chemists to develop aliphatics (simpler chemicals not based on a benzene ring)

Natural gas led us back to very simple reactions with just a few carbon atoms (e.g. turpentine substitute or white spirit)

However, the main difference between the chemistries is that fossil chemistry leads most naturally to compounds of carbon and hydrogen. In contrast, natural sources lead to compounds of carbon hydrogen and oxygen and often nitrogen i.e. CHON. The extra oxygen atoms make it easier for nature to break the compounds down, and even when nature produces non-oxygen compounds such as terpenoids it builds in weak bonds to provide an attack point. It's notable that amongst all the C5 terpenoids the only ones that nature produces have at least one double bond. Artificial ones can be made with the same formula, but nature isn't interested and can't break them down (e.g. adamantane),

The CORR, CO2RR, sugars, fats, and lignin routes all produce CHO products that nature can generally handle. - in fact, often the issue makes them a bit more difficult to handle so they last longer.

The sugars route also leads to natural and non-natural products made by pursuing e coli or yeast to make more of, or different, compounds e.g. pharmaceuticals.

Overall chemists and biochemists have a rich knowledge of these areas and are still innovating new reaction pathways at a high rate.

To summarize, CO2 capture will cost, however, this can to some extent be defrayed by the products that can be created as a result. Using CO2 directly and industrially can be made less expensive by scale, and by using cheap or free energy, by co-locating plants, and all the usual industrial and commercial approaches.  It can also be made more competitive by fully accounting for the issues from fossils. Whether it can be cheaper than using free concentrated energy from the ground is unknowable at present, but it could be.

The Natural route is very much a regenerative path. Large areas of land must be brought into use; however, it is entirely possible that this will be a good thing. The main issue is probably water- however given that the Amazon is a natural sand desert, made fertile, and wet by the trees themselves, perhaps the Sahara, Negev, and Gobi deserts might be green once more. The sea is a huge opportunity and also a problem if misused but fast growth of the many types of algae, which can also be adapted to produce different useful substances, including food, is a plausible and potentially easily scaled path. 

I’ve ducked the issue of overall cost partially because if you look at the whole petroleum industry it's a massive cost, and does massive damage that has built up future costs that are in the hundred trillion dollars scale.( 100 trillion or so just removing the excess CO2 produced, plus plastics issues etc.), The CO2 industry will also be massive, employing probably more people, and needs to be seen in terms of its benefits, At present many of these are unknown or hard to nail down but also many are obvious.

How is you balance all this is above my paygrade, 

but it seems that the opportunities offered by chemistry, biochemistry, wrights law, and avoiding the twin crunches of too much CO2, and over-expensive petroleum products as the wells run out, seems like a sensible direction to go

Ian

Dec 2023.