In response to mounting environmental issues and climate change, such as rising temperatures, deforestation, and pollution, many industries are taking new initiatives to reduce their footprint on the world. Industries are modifying their materials and manufacturing processes to reduce environmental degradation, improve water quality, and preserve natural resources.

One such example is Armstrong. Armstrong is a global construction manufacturer; they mass produce ceiling tiles, and floorboards.

Recently, as part of an initiative to be more sustainable and environmentally conscientious, Armstrong switched from using raw trees to produce their ceiling tiles, to recycling paper products. This change would enable usage of already available resources, repurposing old paper, rather than cutting down new trees to produce their ceiling tiles.

But this well-intentioned change has unforeseen consequences.

Production of paper-based ceiling tiles is a “wet” process. A million gallon water system is run through the system to produce the tiles, then treated and reused.

A schematic of Armstrong's treatment plant, used to filter and process the water.

The switch to paper products, which have already been processed once, resulted in short chain cellulose fibers. Of these fibers, not all are incorporated into the tiles, and remain in the water system. A variety of microbes feed off these cellulose fibers in the water system. Of these, some bacteria strains produce butyric acid as a byproduct of anaerobic fermentation. Butyric acid has a highly unpleasant smell; it is the major distinctive smell in human vomit, and can be detected by humans at concentrations as low as 10 parts per million.

Butyric acid production is activated by low oxygen conditions. Regulating the oxygen levels of such a large system, a million gallons, is challenging. Armstrong uses aeration pumps and basins. A complication is that this mechanism can get clogged, preventing them from functioning properly at times.

A photograph of an aeration basin used to incorporate oxygen into the water system.

When this occurs the water system can change from its targeted oxygen level of 2.0 mg/L, to nearly 0 mg/L oxygen, resulting in anaerobic conditions. Subsequently, it activates an anaerobic fermentation pathway, in which butyric acid is an end product.

Currently Armstrong remediates this issue by periodically using biocides,chemicals that eliminate al microbial growth, when the butyric acid concentration is too high. This solution has many drawbacks. First, it is a short term solution, it kills all the microbial growth, but the butyric-acid-producing bacteria re-emerge, except now some may even be resistant to the biocides. Biocide treatment is an expensive treatment and also has to be closely monitored. Lastly, there are potential environmental risks and hazards; the biocides could leave the closed factory system and contaminate the natural ecosystem, negatively affecting wildlife and their habitats.

Faced with a dilemma, Armstrong presented us with this real world industrial problem with environmental consequences, asking us to create a sustainable solution that could be applied immediately in their factory. By using synthetic biology, we created a cost efficient, scalable,environmentally safe, and long term solution.