“Acetogens are thought to be one of the first life-forms on Earth. The ancient Earth’s atmosphere was very different to the atmosphere today — there was no oxygen, yet plentiful carbon dioxide.
Acetogens were able to recycle this carbon using chemical energy sources, such as hydrogen, in a process called gas fermentation. Today, acetogens are found in many anaerobic environments, such as in animals’ guts.
Not being able to use oxygen makes acetogens less efficient at building biomass; they are slow growers. But interestingly, it makes them more efficient producers.
For example, a typical food crop’s energy efficiency (where sunlight is turned into a product) may be around 1%. On the other hand, if solar energy was used to provide renewable hydrogen for use in gas fermentation (via acetogens), this process would have an overall energy efficiency closer to 10-15%.
This means acetogens are potentially up to twice as efficient as most current industrial processes — which makes them a cheaper and more environmentally friendly option. That is, if we can bring the technology to scale.
Gas fermentation is scaling up in China, the United States and Europe. Industrial emissions of carbon monoxide and hydrogen are being recycled into ethanol to commercially produce aviation fuel from 2022, plastic bottles from 2024 and even polyester clothes.”
The authors published “an economic assessment in Water Research to help chart a pathway towards widespread acetogen-carbon dioxide recycling […] and found economic barriers in producing some products, but not all. For instance, it is viable today to use carbon dioxide-acetogen fermentation to produce chemicals required to make perspex.”