Biodeterioration is the break-down of materials through biological processes. The process typically starts as an invisible biofilm, also called a pioneering biofilm, before becoming visible, or mature, biofilm. What impact does biodeterioration have? What are some of the conventional and innovative ways to fight it?
Heavy Social and Economic Impact
Biodeterioration, and more specifically its prevention and treatment, has a high social and economic impact. Whether its concrete becoming weak and failing or wood rotting, biodeterioration heavily reduces the durability of building materials.
This most heavily impacts culturally and historically important artifacts or sites. Because these types of artifacts and structures are typically open to the elements and ancient, biodeterioration can really take a toll.
Some examples of this are Angkor Vat in Cambodia and the ruins of the archaeological site of Milet in Turkey. At the Milet site in Turkey, a black biofilm was causing excessive solar heating of the marble and causing microcracking.
At Angkor Vat, a significant site that records the history of the Khmer civilization, the large number of microbes was causing discoloration of the sandstone and ultimately deterioration through mineral dissolution and acid production.
Biodeterioration also impacts current building sites. While the age of the structure is younger, the exposure to the elements can cause significant damage in a relatively short time.
In both new and old structures, the effects of biodeterioration steeply increases the cost to upkeep. Especially in poorer communities, the financial burden of preventing and treating biodeterioration can mean the loss of historically and culturally significant sites and artifacts. It’s just too expensive to save them.
Biodeterioration can cause a loss of function. A bridge or dam that has significant biofilm will eventually fail. The loss of structures like bridges or dams has a significant economic and quality-of-life impact on communities.
Methods to Fight Biodeterioration
Current methods to fight biodeterioration are high-pressure cleaners, biocides, or preventative measures like water-repellent coatings. These methods often have a good enough cost-benefit ratio, but they come with a lot of limitations.
They are not typically long lasting. Studies have often shown recolonized right after application or use of the method.
There is also a significant issue with the biofilm developing resistance to biocides. To make the problem even worse, organic biocides can be used as a nutrient source by some microflora once they develop resistance to the biocide.
Perhaps most significantly, many of the current methods are eco-toxic and harmful to humans.
In some countries new regulations have limited the use of these methods and products. Clearly, new strategies are needed.
Some of the new strategies being looked at are ionic liquids and natural compounds like plants and essential oils. In general, natural compounds are less toxic than purely synthetic alternatives.
Ionic liquids could be a viable alternative to biocides for stone. Ionic liquids are salts with a melting point above 100°C. They are liquid at room temperature.
Ionic liquids are very antimicrobial thanks to the interaction with the cell walls of bacteria. Studies have shown them to be very effective again various bacteria, yeast, hyphomycetes, and algae – making them ideal to fight biodeterioration.
By observe plants in nature, more than 60 potentials have been identified and researched, such as Chili peppers, Eucalyptus, Melaleuca, and Thyme. Both the whole plant and essential oils have been used in the research.
One drawback to using natural compounds is cost. The high cost of production makes them not feasible for large scale operations.
Studies, like this one published in the Journal Science of The Total Environment, have found that biodeterioration should be fought on a case by case basis and have a multi-pronged attack. For example, pretreating with water-repellent coatings has been shown to lower the amount of biocide needed.
Researchers have also concluded that the methods need to be optimized to increase effectiveness. For example, some biocides are more effective if the biofilm is hydrated before application.
In general, there is still a lot of learning and research to be done to understand biodeterioration and the efficacy of various treatment methods.