Conversion Pathways

Carbon dioxide (CO₂) reduction pathways—either direct or indirect—can be divided up by the conversion technology and the method for electricity utilization.

Direct Pathways

Direct pathways involve electrons directly in the chemical reduction process.

Microbial Electrosynthesis

Micro-organism enabled low-temperature electrocatalytic reduction.

High-Temperature Electrolysis

High-temperature electrocatalytic reduction in a ceramic membrane reactor.

Low-Temperature Electrolysis

Low-temperature electrocatalytic reduction in polymer electrolyte membrane reactors.

Indirect Pathways

Indirect pathways utilize intermediate electron carriers, such as hydrogen.

Thermochemical Conversion

Catalytic hydrogenation of carbon dioxide using heat and pressure.

Biological Conversion

Microbial fermentation of carbon dioxide and hydrogen.

Summary Table

Pathway	Product	2014–2018 Market Price Range (2016$/kg)	Current	Future	Theoretical
			Projected Costs (2016$)
Low-Temperature Electrolysis	Carbon Monoxide	0.17–0.26	1.55	0.23	0.07
	Formic Acid	0.66–0.67*	1.36	0.23	0.05
	Oxalic Acid	1.40**	2.23	0.33	0.03
	Ethylene	0.38–1.29	6.39	1.20	0.42
	Ethanol	0.42–0.72	6.07	0.74	0.30
Microbial Electrosynthesis	Methane	0.13–0.23	107.8	1.90	0.76
	Acetic Acid	0.50–0.71	5.32	0.57	0.22
	Formic Acid	0.66–0.67*	26.42	0.29	0.21
	Ethanol	0.42–0.72	441.01	1.10	0.54
High-Temperature Electrolysis	Carbon Monoxide	0.17–0.26	0.38	0.15	0.05
High-Temperature Electrolysis	Methane	0.13–0.23	11.15	0.77	0.36
Biological Conversion	Methane	0.13–0.23	2.22	1.04	0.64
	Acetic Acid	0.50–0.71	0.95	0.34	0.21
	Ethanol	0.42–0.72	1.27	0.64	0.39
	Polyhydroxybutyrate	2.40–3.30***	1.36	0.64	0.37
Thermochemical Conversion	Carbon Monoxide	0.17–0.26	0.45	0.25	0.16
	Methane	0.13–0.23	2.28	1.08	0.68
	Dimethyl Ether	0.49–0.72	1.89	0.87	0.58
	Methanol	0.25–0.48	1.66	0.80	0.52
	Fischer-Tropsch Liquids	2.14–3.41	4.52	1.31	0.81

*Data only for 2014 and 2016
**Data only for 2017
***Data from 2017, includes all PHAs

Publications

For more analysis and discussion on these CO₂ conversion pathways and their products, see these accompanying publications.

The Economic Outlook for Converting CO₂ and Electrons to Molecules, Energy & Environmental Science (2021)

Transforming the Carbon Economy: Challenges and Opportunities in the Convergence of Low-Cost Electricity and CO₂ Utilization, Energy & Environmental Science (2019)