Bacteria convert steel waste to capture carbohydrate

Researchers in China have developed a microbial system that converts waste of steel into useful building materials while capturing carbon dioxide from cement plant emissions. The technology solves two major environmental challenges with a single biological solution.

The study, published in engineering, shows how bacteria accelerate the conversion of steel furnaces (a huge industrial by-product) that can actively remove carbon dioxide from the atmosphere. More than 400 million tons of steel slag are accumulated worldwide each year, and less than 30% of people find productivity.

Microbial engineering at work

The research team, led by Professor Chunxiang Qian of Southeast University, used mucosal bacteria in a rotating reactor system that handles cement kiln flue gas. Microorganisms accelerate chemical reactions that usually require high temperatures and pressures, making the process energy efficient and scalable.

In just one hour, the microbial system achieved a carbon dioxide fixation ratio of about 10%, almost twice the rate without bacterial assistance. The process remains consistent across seasons and different flue gas compositions, indicating that industrial applications are very stable.

Solve multiple issues

Steel furnaces face major challenges to the construction industry. Its easily expanded compound makes it unsuitable for widespread use, and its low reactivity limits its effectiveness as a cement substitute. The microbial carbonic acid process solves these two problems at the same time.

The researchers found: “When the carbon dioxide fixation ratio exceeds 8% and the specific surface area is at least 300 square meters per kilogram, the sound problem of the steel furnace can be effectively solved, thereby promoting the safe use of the steel trough.”

Key Performance Indicators

• Compared with non-microbial processes, the carbon dioxide fixation rate has doubled
• Consistency in batch processing and seasonal variation in four different troughs
• When replacing 30% of cement clinker, the activity index is 87.7%
• The reaction transition zone is 50% deeper than the chemical process only
• Porosity in final cement products decreased by 15%

Biological Advantages

Bacteria not only speed up the reaction, but also fundamentally changes the characteristics of the final product. The calcium carbonate crystals produced by microbial action are significantly smaller than those formed by pure chemical processes, and are measured only 30.7 nanometers, while the alternative method for chemical synthesis is 61.1 nanometers.

These smaller crystals will produce denser, stronger cement structures. The bacterial cells themselves remain in the final product, acting as nuclear sites, and continue to enhance the performance of the material during construction application.

Analysis showed that the microorganism consumed 71.40% of the dinuclear silicone and 68.25% of the silicone salt after 48 hours, 63% higher than the chemical process alone. This enhanced reactivity stems from the bacteria’s ability to accelerate ion dissolution and carbonate precipitation.

Industrial implementation

The team tested their system using actual cement kiln gases containing 22-31% CO2 and various pollutants including sulfur dioxide and nitrogen oxides. The bacterial system has proven to be elastic to these harsh conditions and can maintain effectiveness in the range of 48°C to 67°C.

The rotary reactor is designed with a diameter of 1.1 meters and a length of 3 meters, and the materials are processed continuously instead of batch processing. This approach facilitates large-scale production while ensuring a thorough mixing between the steel slag powder and carbon dioxide gas.

Environmental impact

Cement production accounts for about 8% of global carbon dioxide emissions, while in China alone, steel slag accumulation exceeds 1 billion tons. Microbial technology provides a way to solve both problems while creating valuable building materials.

This process turns the problematic waste stream into a high-performance cement alternative that meets the first-level standards set out in the Chinese Building Guidelines. With proper optimization, the technology can significantly reduce the environmental footprints of both industries while creating economic value from waste materials.

The study shows how biological systems enhance industrial processes in ways that pure chemical methods cannot match. When the construction industry seeks sustainable alternatives, microbial engineering may provide both environmentally beneficial and viable solutions.

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