CO2 Fermentation Boosts Natural-Process Coffee Scores in Colombian Trial

Sealed Containers and CO2 Transform Natural Coffee Quality

A new study conducted in Colombia suggests that the use of sealed containers and a small amount of carbon dioxide (CO2) gas can transform ordinary “natural” coffees into highly specialized coffees.

The study was conducted by researchers at the Colombian Institute of Technology (SENA) and the University of Valle, comparing open-air and closed-air fermentation methods. The researchers fermented coffee beans from a single field using five different types of fermenters before drying them; the coffee was then dried, crushed, and graded on a 100-point scale by the International Specialty Coffee Association (SCA).

CO2-Fermented Coffee Scores Highest

The coffee that had been stored in a sealed container for 24 hours in carbon dioxide gas came out on top with an average score of 86.90, while the coffee that had not been processed at all scored only 82.15.

The study, published in December 2025 in the prestigious Scientific World Journal, is said to point to a new direction for the specialty coffee market — one that is scientifically proven and can be widely applied, rather than being based only on experience and small-scale experiments.

Filling a Gap in Coffee Fermentation Research

The researchers noted: “Although much research has been conducted on the fermentation process of coffee, most of it has focused on laboratory-controlled or wet processing; its applicability to natural coffee has been limited. In particular, there has been a lack of scientific data on the effect of carbon dioxide-assisted fermentation on natural coffee preparation and chemical composition in real production sites.”

Implications for Coffee Producers

This new discovery suggests a simple and effective way for coffee producers to improve quality. The sealed-container CO2 fermentation method could be particularly valuable for natural-process coffee origins, offering a scientifically validated technique to elevate cup scores and market value.