Biodegradation

Lore & Background

Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. In contrast, phytodegradation relies on green plants but has few applications. The process can be divided into three stages: biodeterioration, biofragmentation, and assimilation. Biodeterioration is a surface-level degradation that modifies mechanical, physical, and chemical properties, often influenced by abiotic factors like light, temperature, and chemicals. Biofragmentation involves cleaving bonds within polymers to generate oligomers and monomers, with aerobic digestion producing carbon dioxide, water, residue, and biomass, while anaerobic digestion also produces methane. Assimilation integrates the resulting products into microbial cells, where they enter catabolic pathways.

Reader's Guide

Biodegradation is significant because it governs the natural recycling of organic materials and informs waste management and environmental policy. The European Union defines biodegradability as conversion of over 90% of original material into CO2, water, and minerals by biological processes within six months. Factors affecting the rate include light, water, oxygen, temperature, and bioavailability. Testing methods such as respirometry measure CO2 production for aerobic microbes or methane for anaerobic microbes. However, lab results may not reflect real-world conditions, as landfills often lack necessary light, water, and microbial activity. The term 'biodegradable plastics' refers to materials that break down into low-weight compounds and non-toxic byproducts after use, though rates vary widely. For example, starch-based plastics degrade within two to four months in a home compost bin, while polylactic acid requires higher temperatures. The plastics industry uses its own definition of compostable, and the European Union offers four criteria including chemical composition limits and biodegradability of over 90%.

Did You Know?

• Biodegradation does not apply to elements; heavy metal pollutants do not biodegrade.
• Anaerobic digestion produces methane, while aerobic digestion does not.
• The European Union standard for biodegradability requires over 90% conversion to CO2, water, and minerals within six months.
• A bacterium named Ideonella sakaiensis was found to biodegrade PET.