Bacterial-fibre test block

Speculative concept
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

This is an idea, not a product. Nothing here has been built or tested unless a linked technology profile says so.

The problem

Builders may want building materials with a lower carbon footprint than conventional cement-based or fired products. A material grown from bacterial protein fibres is one possible option, but it is an open question whether it could meet the same structural and durability needs, and no carbon benefit has been shown for it.

The idea

A realistic first step would be a small, non-structural test block made from engineered bacterial protein fibres, shaped and dried in a laboratory. It would not be sold or used in buildings. Its purpose would be to test whether the process can make repeatable blocks of a set size, and how the material behaves in compost and in moisture. Carbon storage is not assumed. Any carbon claim would need separate lifecycle accounting.

Enabling technology

  • Engineered living materials: Engineered living materials are materials made with the help of living cells or the structures they produce. A 2024 laboratory study made a stretchable, compostable film from engineered bacterial protein fibres, but the work is at prototype stage and does not show a product that can replace plastic.

What stands in the way

  • The best-documented example, MECHS, is a thin film made at laboratory scale, with a yield of 0.5 to 1 gram of film per litre of culture (Manjula-Basavanna and colleagues, 2024). The sources reviewed do not show a block-scale production process.
  • The authors state that ultimate tensile strength, tear strength and resistance to water need further improvement (Manjula-Basavanna and colleagues, 2024). A block would need to resist cracking, crumbling and moisture.
  • The film did not fully dissolve in the authors' water test. The compost test used small 5 by 5 cm samples in one compost at 20 degrees Celsius. Durability outdoors or in buildings has not been tested.
  • The sources reviewed report no carbon storage measurement for an engineered living material and no life-cycle assessment (Manjula-Basavanna and colleagues, 2024). Feedstock, fermentation, drying, transport and end-of-life would all need counting before any carbon claim is made.
  • The sources reviewed contain no structural, fire or service-life data for a block of this material. Building codes and procurement rules would normally require such data (general observation, not drawn from a specific source).

A cheap way to test it

In a laboratory, with approval from the institution's biosafety committee because the bacteria are genetically engineered, make 3 batches of 5 by 5 cm test coupons using the bacterial-fibre process described in the MECHS paper (Manjula-Basavanna and colleagues, 2024), with at least 3 coupons per batch. Weigh each coupon dry before burial. Bury the coupons in fish-manure compost at 20 degrees Celsius and 80% relative humidity, as in the published compost test. Dry and weigh any recovered residue at day 75. Pass if every coupon has lost at least 95% of its dry mass by day 75, the longest time the published dried-compost case reported, and if the time to reach 95% mass loss differs by no more than 15 days between batches. Fail if any coupon is below 95% loss at day 75, or if batch results differ by more than 15 days. The 95% threshold and 15-day spread are proposed for this test plan and are not taken from the published work. Also record the Young's modulus of the same coupons by tensile test and compare it with the published range of 6 to 450 MPa. This is a recording step, not a pass or fail test. No human or animal exposure is part of this experiment, and waste containing engineered organisms must be disposed of under the lab's biosafety rules.