Conversion of CO2 to methanol
CO2-to-methanol conversion has the potential to play a significant role in reducing greenhouse gas emissions and advancing a more sustainable energy system.
MERYT Catalysts & Innovation
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Methanol has many uses, including as the starting feedstock for several high-demand chemicals, such as dimethyl ether oxymethylene ethers, as an additive or as a fuel component for gasoline engines and fuel cells. It is also one of the leading contenders as a renewable fuel for marine engines. Building on the hydrogen economy, the hydrogenation of carbon dioxide (CO2) to produce methanol could potentially lead to the generation of the ‘methanol economy’.
The conversion of CO2 to methanol is a process known as CO2 reduction and involves the following steps:
- Capture and purification of CO2: CO2 is captured from industrial processes or directly from the air, then purified to remove impurities.
- Production of low-carbon-intensity hydrogen, initially from the reforming of methane with carbon capture, but over time, increasingly from the electrolysis of water using renewable electricity from solar, wind or hydroelectricity.
- Conversion of CO2 to carbon monoxide (CO): CO2 is reacted with hydrogen gas (H2) to produce carbon monoxide (CO) and water (H2O). This is known as the reverse water-gas shift reaction.
- Conversion of CO to methanol: The CO produced in the previous step is then reacted with hydrogen in the presence of a catalyst to produce methanol (CH3OH).
The cost of producing fossil fuel-based methanol is in the range of $100-250 per tonne.
Renewable methanol can be produced using renewable energy and renewable feedstocks via two routes:
- CO2 would most likely be captured from the combustion of fossil fuels in power plants, or furnaces for industrial steel and glass manufacture. Even though recycled, it originates from non-renewable fossil fuels, making the overall process net CO2 positive. However, given that the CO2 from these sources would otherwise be released into the atmosphere, using it to produce methanol with green hydrogen would result in low-carbon methanol. It would also displace a corresponding amount of fossil fuel otherwise required. In the case of cement, the CO2 is released from the chemical process itself.
- CO2 from biogenic sources such as distilleries, fermentation units, municipal solid waste (MSW) incinerators, and power plants that burn biomass or biogas to generate electricity is normally treated as off-gas and emitted to the atmosphere (usually at high CO2 concentrations but atmospheric pressure). These biogenic sources are considered to be renewable, sustainable, and net CO2 neutral.
- However, when the CO2 from these biogenic sources is captured for storage or utilisation, the process is usually referred to as bioenergy with carbon capture and storage (BECCS). BECCS and CO2 obtained from the atmosphere via direct air capture (DAC) are considered net CO2 negative.
Bio-methanol is produced from biomass. Potential sustainable biomass feedstocks include forestry and agricultural waste and by-products, biogas from landfill, sewage, MSW, and black liquor from the pulp and paper industry.
Green e-methanol is produced from CO2 captured from BECCs and DAC together with low-carbon-intensity hydrogen.
In general, each molecule of CO2 entering the process will exit as a methanol molecule. However, each CO2 molecule requires three molecules of hydrogen and will produce one molecule of water for each molecule of methanol. Accordingly, about 1.38 t of CO2 and 0.19 t of hydrogen (~1.7 t of water) are needed to produce one tonne of methanol. About 10-11 MWh of electricity is required to produce one tonne of e-methanol, most of it for the electrolysis of water (assuming CO2 is available).
With a 100 MW electrolyser, about 225 t/d of e-methanol could be produced. Such electrolysers, although large, are already available from Thyssenkrupp.
For a large 1,000 t/d e-methanol plant, an electrolyser of at least about 420 MW would be necessary. To replace a conventional mega-methanol plant with a production capacity of 2,500 t/d, an electrolyser in the gigawatt range would be needed. Such large electrolysers are still in the development phase.
Since production is currently low, limited data are available on actual costs, meaning that potential costs must be estimated. The bio-methanol production cost will depend on the bio-feedstock cost, investment cost, and the efficiency of the conversion processes.
In the short term, biomass could be co-fed into a coal-based gasifier, or biogas fed into a natural gas-based methanol plant, so allowing for the gradual introduction of biomass as a feedstock and making methanol production more sustainable at a potentially lower cost.
The cost of e-methanol depends to a large extent on the cost of hydrogen and CO2. The cost of CO2depends on the source from which it is captured, such as from biomass, industrial processes or DAC. The current production cost of e-methanol is estimated to be in the range of $800-1,600/t, assuming CO2is sourced from BECCS at a cost of $10-50/t. If CO2 is obtained by DAC, where costs are currently $300-600/t, then e-methanol production costs would be in the range $1,200-2,400/t (Zhang, 2019), (Chaplin, 2013).
The future cost of green hydrogen production mainly depends on further reductions in the cost of renewable power generation and electrolysis, and gains in efficiency and durability. With anticipated decreases in renewable power prices, e-methanol costs are expected to decrease at rates of $250-630/t by 2050.
As in the case of bio-methanol, the co-production of brown/grey (fossil) and green e-methanol could allow the gradual introduction of green e-methanol at a reasonable cost. Currently, the main barrier to renewable methanol uptake is its higher cost than fossil fuel-based alternatives, and that cost differential will persist for some time. Its value lies in its emissions reduction potential compared to existing options.
Addressing process differences and facilitating the scale-up of production and use can help reduce costs but will require a variety of policy interventions. With the right support mechanisms and the best production conditions, renewable methanol could approach the current cost and price of methanol from fossil fuels.
Different groups are developing efficient and cost-effective methods to carry out this conversion. While this process has the potential to reduce greenhouse gas emissions and produce a useful fuel, it is still in its early stages of development and has yet to be implemented on a large scale.
Several research groups around the world are working on CO₂-to-methanol conversion, and it is difficult to say which one is more advanced as each group has its unique approach and research focus. However, here are a few examples of prominent research groups in this field:
- Researchers at the University of Cambridge in the UK have developed a process that uses a copper catalyst to convert CO2 to methanol using hydrogen gas. Their process is highly efficient and has the potential to be scaled up for industrial use.
- Researchers at the Lawrence Berkeley National Laboratory in California, USA, have developed a hybrid catalyst that can selectively convert CO2 to methanol with high efficiency. Their catalyst is made from copper oxide and platinum and operates at low temperatures, which reduces energy requirements.
- Researchers at the Korea Institute of Science and Technology in South Korea have developed a process that combines CO2reduction with wastewater treatment. Their process uses a microbial electrochemical system to convert CO2to methanol while simultaneously treating wastewater.
These are just a few examples of the many research groups working on CO2-to-methanol conversion. The field is rapidly evolving, and new breakthroughs are being made all the time. Here are some more examples of the economics of CO2-to-methanol conversion:
- Carbon Clean Solutions in India has developed a CO2 capture technology to capture CO2 emissions from industrial processes and convert them into methanol. The company estimates that its technology can produce methanol at around $150 per ton, which is competitive with traditional methanol production processes. The company is planning to build a commercial-scale plant with a capacity of 10,000 tons per year.
- In the US, Carbon Recycling International has developed a CO2-to-methanol conversion process that uses renewable energy sources such as geothermal and hydroelectric power to generate the required electricity and hydrogen. The company estimates that its process can produce methanol at around $ 600 per ton, which is higher than the current market price for methanol but competitive with traditional methanol production processes.
- Researchers at the Dalian Institute of Chemical Physics in China have developed a new CO2-to-methanol conversion process that uses a copper-based catalyst and a novel reactor design to improve the efficiency of the conversion process. The researchers estimate that their process can produce methanol at around $500-$600 per ton, which is higher than the current market price for methanol but lower than the estimated production cost for previous CO2-to-methanol conversion processes.
- In Sweden, Carbon Clean Solutions is building a commercial-scale CO2-to-methanol plant with a capacity of 5,000 tons per year. The plant will use CO2 emissions from a local cement factory as feedstock, and the methanol will be sold to local customers for use as a fuel and chemical feedstock. The company estimates that the plant will cost around €20 million ($23 million) to build and will produce methanol at around €500-600 ($580-700) per ton.
- LanzaTech in the US has developed a CO2-to-ethanol conversion process that uses waste gases from industrial processes as a feedstock. The company estimates that its process can produce ethanol at around $1.50 per gallon, which is competitive with traditional ethanol production processes. The company is also developing a methanol production process using the same technology.
- Researchers at the University of Cambridge in the UK have developed a new CO2-to-methanol conversion process that uses a copper-based catalyst and a novel reactor design to improve the efficiency of the conversion process. The researchers estimate that their process can produce methanol at around $500 per ton, which is competitive with traditional methanol production processes.
- Carbon Clean Solutions in India is also developing a CO2-to-methanol plant in the UK with a capacity of 60,000 tons per year. The plant will use CO2 emissions from a local power plant as a feedstock, and the methanol will be sold to local customers for use as a fuel and chemical feedstock. The company estimates that the plant will cost around £60 million ($81 million) to build and will produce methanol at around £450-500 ($610-680) per ton. Syngas conversion to methanol is a commercial technology with many years in the market. Most syngas production originates in a fossil feedstock. The main idea of direct conversion of CO2 is converting CO2 from emissions sources, CO2 from waste or natural sources of CO2, and conversion of industrial flue gas.
Table 2 shows a detailed SWOT analysis comparing syngas-to-methanol and CO2-to-methanol processes with green hydrogen.
Pilot units operating up to 2023
As of 2023, several pilot plants for CO2-to-methanol conversion are operating around the world. Here is a non-exhaustive list of some of these plants and their capacities:
- Carbon Clean Solutions, Tuticorin, India: Pilot plant capacity of 10 tons of CO2 per day using a proprietary solvent-based absorption technology for CO2 capture and conversion to methanol.
- Carbon Clean Solutions, Teesside, UK: Collaboration with the utility company Northern Gas Networks with a pilot plant capacity of 0.1 tons of CO2 per day using the same solvent-based absorption technology for CO2 capture and conversion to methanol as the Tuticorin plant.
- Global Thermostat, Huntsville, Alabama, USA: Pilot plant capacity of 4 tons of CO2 per day using a patented direct air capture technology for CO2 capture and conversion to methanol.
- Siemens Energy, Rotterdam, Netherlands: Pilot plant capacity of 1.25 tons of CO2 per day using a novel CO2 electrolysis technology to convert CO2 to methanol.
- Carbon Recycling International, Iceland: In 2019, Carbon Recycling International opened a plant in Svartsengi, Iceland, with a capacity of 50 tons of methanol per year using a process that combines CO2 from geothermal power plants with hydrogen from electrolysis.
- Enerkem, Edmonton, Alberta, Canada: Pilot plant capacity of 1 ton of CO2 per day using a thermochemical process to convert CO2 to methanol.
- Mitsubishi Heavy Industries, Yokohama, Japan: Pilot plant capacity of 0.3 tons of CO2 per day using a proprietary catalyst to convert CO2 to methanol.
- Hubei Sanning Chemical, China: Pilot plant capacity of 5,000 tons of methanol per year using SCT’s CTL catalyst and a hydrogenation process.
Pilot units efforts for process and catalyst development and scale-up
As of 2023, there are several important scale-up efforts for process and catalyst development for CO2 -to-methanol conversion. Some future projects are shown in Table 3. In addition, a lot of effort is being put into development and study to optimise the process:
- Electrochemical CO2 conversion: Electrochemical CO2 conversion is a promising method for CO2-to-methanol conversion gaining traction in recent years. Research groups are working to scale up electrochemical reactors and optimise the operating conditions to improve the efficiency and economics of the process.
- Hybrid catalysts: Hybrid catalysts combine multiple active components to achieve better selectivity and stability, and they are being developed and tested at larger scales. These catalysts may improve the overall efficiency and economics of the CO2-to-methanol conversion process.
- Integration with renewable energy sources: Research groups are exploring the integration of CO2-to-methanol conversion with renewable energy sources, such as solar, wind, and hydropower, to produce a sustainable and carbon-neutral fuel. This approach has the potential to reduce the energy requirements and carbon footprint of the conversion process.
- Process optimisation: Process optimisation efforts are ongoing, with researchers working to optimise the conditions and parameters of the CO2-to-methanol conversion process to improve its efficiency and economics. This includes exploring different reaction conditions, such as temperature and pressure, as well as optimising the catalyst loading and reactant ratios.
Overall, these scale-up efforts are focused on improving the efficiency, scalability, and economics of CO2 -to-methanol conversion. With continued research and development, the technology has the potential to play a significant role in reducing greenhouse gas emissions and advancing a more sustainable energy system.
Chaplin, A.G., 2013. “Renewable Methanol. An analysis of technological potentials in light of the EU biofuels policy objectives of Greenhouse Gas Savings, Security of Supply and Employment. Master’s thesis, Sustainable Energy Planning https://books.google.co.uk/books/about/Renewable_Methanol.html?id=QMgHAwAAQBAJ&redir_esc=y
Cheng Wu-Sun & Kung, Harold, H., 1994. Methanol Production and Use (Chemical Industries), V.57. New York: M. Dekker.
IRENA and Methanol Institute, 2021. Innovation Outlook: Renewable Methanol, International Renewable Energy Agency, Abu Dhabi. https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2021/Jan/IRENA_Innovation_Renewable_Methanol_2021.
Raimon, M. (2022, August). Power-to-X integration, the methanol case. Retrieved from Decarbonisation Technology magazine: https://ptqmagazines.digitalrefining.com/view/200571133/63/
Veolia. (2022, April 6). Veolia launches an innovative industrial solution to produce CO2 neutral biofuel from pulp production. Retrieved from Veolia: www.veolia.com/en/our-media/newsroom/press-releases/veolia-launches-innovative-solution-produce-CO2-neutral-biofuel
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