🌎 Best Way To Scale CO₂ Capture 🌎
My Climate Journey (Update 3)
Welcome to My Essays
Hi! I’m Ahmed, a curious analyst.
I dive into topics and share what I discover through essays like this.
I hope you enjoy reading them!
What I’m Sharing Today
An analysis of the best way to make money from carbon capture.
If you missed why I’m looking into carbon capture, check out this essay.
What Is The Best Way To Make Money From Carbon Capture?
The carbon capture industry centers around two questions:
How will you capture CO₂?
What will you do with the CO₂ once you capture it?
The first question is about the cost of capturing CO₂.
The second question is about how you will make money from it.
Your product or application decides what kind of capture system you need.
It is best to start by answering the second question.
What will you do with the CO₂ once you capture it?
There are 2 general paths you can take.
Store CO₂ Underground
Turn CO₂ into Products
In a previous essay, I explored the idea of storing CO₂ underground and found it unlikely to succeed.
To recap: the problem lies in the revenue model.
Companies aim to store CO₂ underground and expect others to pay for it.
The problem is this approach works like a charity.
People give you money and get nothing in return.
People, companies, and governments don’t like spending money without receiving value.
This means that storing CO₂ underground is not a reasonable option.
This essay will focus on option 2: turning CO₂ into products.
Assessing CO₂-to-Product Approaches
Product #1: CO₂ + H₂ to Make Natural Gas (CH₄)
To produce 1 MMBTU of natural gas, we need 57.89 kg of CO₂ and 10.61 kg of H₂.
The minimum energy for that amount of CO₂ and H₂ costs $5.76 per MMBTU.
The market price for natural gas is $2.12 per MMBtu (as of November 2024).
The new approach will be more expensive than extracting natural gas from the ground.
This option is not viable.
Product #2: CO₂ to Biomass
Biomass refers to organic material produced by biological organisms as they grow.
There are a few applications.
Energy Application
Let’s say we aim to produce biomass to replace energy from natural gas.
Natural gas costs about 0.7 cents per kWh.
Biomass has an energy content of 19 MJ/kg.
1 MJ = 0.27 kWh, so one kg contains 5.2 kWh.
To compete with natural gas, the maximum cost per kg of biomass must be 3.64 cents/kg.
If we had a production cost of 0, the profit per kg is terrible.
It is unlikely that you can scale with a profit margin so low.
Biochar Application
Biochar is made by burning biomass and turning it into a solid carbon product.
The main application is improving soil. You can learn about the benefits of biochar here.
Let’s say we want to provide biochar for corn farming.
The average corn yield in the US is 177.3 bushels per acre.
The price of corn is $4.17 per bushel as of October 2024.
This means an average farmer earns about $739 in revenue per acre.
The average fertilizer application is 180 to 280 pounds per acre, or 81 to 127 kilograms.
Fertilizer costs between $450 to $800/tonne.
If fertilizer costs $500/tonne, farmers spend $40 to $63 per acre on fertilizer.
If biochar is priced at $500/tonne, what would the fertilizer cost be?
In large-scale biochar studies, application rates ranged from 2 to 60 tons per hectare.
This is about 0.81 to 24.28 tonnes per acre.
Applying 0.81 tonnes per acre would cost $405.
This means farmers pay 8 to 10 times more than fertilizer for the same short-term yield benefits.
To sell biochar, you need a comparable price to fertilizer.
This means you need to sell biochar for $50-$75/tonne and applying the minimum application rate.
Can we produce biochar at a cheap enough price?
There are two general paths you can take to produce biochar.
Option 1: Centralized production
Let’s consider producing biochar in a centralized facility.
The desert is an ideal location for such a facility.
In the desert, solar energy is cheap, and the land is inexpensive because it has limited utility.
For example, you could set up a facility in the New Mexico desert and ship biochar to farmers in Iowa.
(Iowa is the largest corn producer in the US)
The distance from New Mexico to Iowa is about 1,100 miles.
The cost of shipping is $0.16/tonne/mile.
This means it would cost $176/tonne to ship biochar from New Mexico to Iowa.
As we established before, any price over $50-$75 is likely too expensive for farmers.
This moves us to option 2.
Option 2: Biochar production at the farm
This option involves removing extra biomass from farms. Use that biomass to create biochar.
You could put biochar machines on farm tractors.
As the tractor collects crops, it could also collect biomass.
The machine could turn the biomass into biochar as the tractor moves.
The biochar could be dropped directly into the soil.
In this scenario, the cost of biomass is zero.
The transportation cost is zero.
You only pay for the biochar machine and the energy to convert the biomass into biochar.
This is the most cost-effective way to make biochar.
The amount of CO₂ you can capture is limited by what plants already absorb.
If plants absorbed CO₂ at a high enough rate, we wouldn’t have a problem with emissions.
This approach will reduce CO₂ but cannot address the 37 billion tonnes of annual CO₂.
This is not the best approach for large scale carbon capture.
Charcoal Application
When biomass is heated to around 400 degrees, you get biochar.
If you increase the temperature to about 700 degrees, you get charcoal.
Both biochar and charcoal are solid carbon products.
The difference lies in their properties, which are influenced by the heating temperature.
The two general paths for producing charcoal are the same as those for biochar:
Produce it on-site.
Produce it at a centralized facility.
The key difference between charcoal and biochar is the selling price.
The current price of charcoal is $895/tonne.
At this price, shipping costs become less of an issue.
The global market for charcoal is about 54.9 million tonnes.
The large market and high selling price of charcoal make it a good option for scaling carbon capture.
Activated Carbon
If you want to further process biochar or charcoal, you can produce activated carbon.
The only issue is the global market for activated carbon is just 5.8 million tonnes per year.
The market is too small for significant CO₂ reduction.
You might make money, but your overall impact on emissions would be relatively small.
Product #3: CO₂ to Jet Fuel
To produce 1 tonne of dodecane (an overly simplified model for jet fuel), you need 3,100 kg of CO₂ and 438 kg of H₂.
Most CO₂ capture companies estimate their cost will be at $50/tonne at scale.
A general benchmark for hydrogen cost is $1.50/kg.
Using these costs, the production cost of jet fuel becomes $811.8 per tonne.
The market price of jet fuel is $734.55 per tonne.
CO₂-to-jet fuel is too expensive and not a viable option.
Product #4: CO₂ to C₂H₄ (Ethylene)
Ethylene is a key building block for one of the most common plastics: polyethylene.
To produce 1 tonne of ethylene, we need 3.13 tonnes of CO₂ and 1.284 tonnes of H₂O.
Assuming CO₂ costs $50/tonne and using the highest water purification cost of $14.6/tonne, the material cost is $175.73.
Assuming energy costs 1 cent per kWh, the total energy cost to produce 1 tonne of ethylene is $143.6.
The total input cost is $319/tonne of ethylene.
Ethylene sells for $735/tonne, leaving a decent margin for machines and profit.
This approach has potential.
Product #5: CO₂ to Glucose
The Plant Method
Plants use photosynthesis to convert CO₂ and H₂O into glucose.
This is how people produce glucose today.
To know if we can add more sugar crops, let’s look at the global land usage below.
When we look at the land options for growing sugar crops, here’s what we find:
Agriculture – This land is needed to grow food, so we can’t use it.
Forests & Shrubs – Cutting these down would increase emissions instead of reducing them.
Glaciers – Crops can’t grow on ice.
Barren Land (Deserts) – Deserts aren’t good for farming.
Freshwater – Crops can’t grow on water.
Urban Land – Cities and towns can’t be turned into farmland.
The conclusion is there is no extra land to grow enough sugar crops.
Synthetic Chemistry Process
The formose reaction converts formaldehyde (CH₂O) into glucose (C₆H₁₂O₆).
The problem is that only 1% of the formaldehyde turns into glucose.
This is because converting formaldehyde to glucose requires many intermediate steps.
Formaldehyde and its intermediates are highly reactive.
This leads to the formation of unwanted side products.
As the molecule grows larger, the chances of unwanted side reactions increase.
There’s little you can do to fundamentally improve the formose reaction.
Bacteria Method
To produce glucose, you need bacteria cells, sunlight for energy, CO₂, and nutrients from the BG-11 medium.
BG-11 medium costs about 0.69 cents per liter.
In a lab, bacteria have a productivity of 1.5g of glucose per liter of culture medium.
At this rate, producing 1 tonne of glucose would require 666,666.7 liters of BG-11 medium.
The total cost for the medium alone would be $4,599.6/tonne of glucose.
The market price for glucose is $636/tonne.
This does not seem like a viable concept.
Can you do something to improve productivity?
There are two options for growing bacteria: indoors or outdoors.
If we grow bacteria outdoors, we cannot control the conditions.
This will result in limited yield, likely worse than 1.5g of glucose per liter of culture medium.
The volume of BG-11 medium needed and its high cost make outdoor glucose production unviable.
If we grow bacteria indoors, we can control the conditions and improve the yield.
Indoor systems requires you to pay for the energy, and photosynthesis has a 26% energy efficiency.
This means only 1 out of 4 energy units produces useful output, which is inefficient.
The minimum energy to convert CO₂ and water into glucose is 4,321 kWh per tonne of glucose.
At 1 cent per kWh, the minimum energy cost is $43.
To provide the energy, LED lights are required.
There is a trade-off between brightness and intensity.
This results in a maximum efficiency of 50%.
Adjusting for this, the energy cost doubles to $86.
With photosynthesis at 26% efficiency, the cost increases to $330 per tonne.
We still need the culture medium.
At 1.5 grams of glucose per liter of culture medium, we need 666,666.7 liters of BG-11 medium.
This adds $4,599.6 per tonne of glucose.
To break even, we need a 14x productivity improvement.
This analysis does not include the cost of facilities, employees, land, or other expenses.
The conclusion is that both indoor and outdoor paths are not promising.
Synthetic Biology Method
In the bacteria method, a cell is used.
A significant amount of energy is spent on growing and maintaining the cell.
Since we only care about glucose production, using energy to grow the cell is inefficient.
When we examine cells, we find that enzymes are the key to driving reactions.
Enzymes act as catalysts, enabling the specific chemical reactions we need.
By isolating the enzymes, we can create a cell-free enzyme system.
A cell-free system offers several advantages.
The first reason is that enzymes can catalyze reactions with 90%+ efficiency.
This means minimal resources are wasted, which is important for good economics.
The second reason is that it removes the need for a culture medium.
Since we don’t need to grow a cell, we don’t need the culture medium to provide nutrients.
This eliminates a major cost.
The minimum energy required to convert CO₂ and water into glucose is 4,321 kWh per tonne of glucose.
Assuming 90% energy efficiency, the energy required increases to 4,801 kWh.
After accounting for 50% LED light efficiency, the energy requirement becomes 9,602 kWh.
At 1 cent per kWh, the energy cost is $96.02 per tonne.
Since we removed the cost of the culture medium, this process is cost-efficient.
This leaves over $500 per tonne for machines and profit margin.
Product #6: CO₂ to Urea
Urea is one of the most common fertilizers.
It is produced by combining ammonia and CO₂.
Existing ammonia plants already have integrated CO₂ capture systems.
This makes an external CO₂ capture system unnecessary for urea production.
Product #7: CO₂ to Concrete
This method uses CO₂ in the process of producing concrete.
Concrete is composed of 10-15% cement.
For a tonne (1000 kg) of concrete, 100 to 150 kg is cement.
Cement costs about $150/tonne which translates to $15–$22.5 per tonne of concrete.
A company working on this concept is CarbonCure.
They inject 0.6 kg of CO₂ per cubic meter of concrete.
This reduces cement usage by 15 kg per cubic meter.
A cubic meter of concrete weighs 2.4 tonnes.
A 15 kg cement reduction equals 6.25 kg of cement saved per tonne of concrete.
This means you save $0.94 per tonne of concrete.
To get this saving, you need 0.25 kg of CO₂ per tonne of concrete.
To be profitable, your CO₂ cost has to be below $3,760/tonne.
Current CO₂ capture costs are $200–$300/tonne.
This means that this concept is viable.
Global concrete production is about 30 billion tonnes annually.
Injecting 0.25 kg of CO₂ per tonne of concrete could reduce up to 7.5 million tonnes of CO₂ per year globally.
This reduction is small compared to the 37 billion tonnes of CO₂ emitted annually.
This product is insufficient to address global emissions.
Conclusion
A few products show potential for success: ethylene, charcoal, and glucose.
Glucose stands out as the best path forward.
Glucose vs Ethylene
Ethylene can be turned into plastics or other chemicals.
It is versatile for hydrocarbon derivatives but lacks functional groups for making complex molecules.
Glucose has multiple hydroxyl (-OH) and carbonyl (-CHO) groups.
These functional groups enable diverse reactions: oxidation, reduction, esterification, and dehydration.
This makes glucose a better starting molecule for producing chemicals compared to ethylene.
Glucose vs Charcoal
The maximum market for charcoal is 54.9 million tonnes per year.
The global production of glucose is 180 million tonnes per year.
Glucose can be transformed into cellulose.
This adds another 180 million tonnes per year of products.
Cellulose can be used in the paper industry.
This adds another 414 million tonnes per year of products.
Glucose can be used for chemicals to replace CH₄ (natural gas).
This adds another 2.3 billion tonnes per year of products.
This means glucose could be used to produce over 3 billion tonnes of products annually.
Glucose is a clear winner here.
Next Steps
I will learn how to design enzymes that convert CO₂ and H₂O into glucose.
I will share my discoveries with you along the way.
A Few Final Words
I hope you found this essay interesting!
If you know someone who might enjoy it, feel free to share.
Got feedback? Email me at theahmedhassan1@gmail.com.
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Until next time,
Ahmed
