What Does Biodegradable Mean?
In simple terms, a biodegradable substance is one that can be broken down by natural biological processesprincipally by microorganisms such as bacteria, fungi, and algaeinto simple, nontoxic components like water, carbon dioxide (or methane in anaerobic conditions), and mineral salts. The time required for this transformation can range from a few weeks to several years, depending on the material, environmental conditions, and the presence of a suitable microbial community.
How Biodegradation Works
Biodegradation is a multistep process:
- Colonisation Microorganisms attach to the surface of the material.
- Enzymatic Attack Enzymes break complex polymers into smaller molecules.
- Assimilation Microbes absorb the smaller molecules for growth and reproduction.
- Mineralisation The absorbed substances are converted into inorganic endproducts (CO, HO, NH, etc.).
Factors influencing the rate of biodegradation include temperature, moisture, oxygen level, pH, and the presence of a diverse microbial community.
Common Biodegradable Materials
Paper & Cardboard
Made from cellulose fibers that decompose readily in the presence of moisture and microbes.
Wood
Natural lignocellulosic material; rate varies with type of wood and treatment.
Food Waste
Organic matter such as fruit, vegetable scraps, and coffee grounds breaks down quickly in compost.
Bioplastics (e.g., PLA, PHA)
Plantbased polymers that can be composted under industrial conditions.
Natural Fibres (cotton, hemp, jute)
These fibres degrade within months in a warm, moist environment.
StarchBased Materials
Often blended with other polymers to improve flexibility; they decompose in compost.
Environmental Benefits
Switching to biodegradable alternatives can mitigate several environmental problems.
- Reduced Landfill Volume Materials that decompose shrink the amount of longlasting waste.
- Lower GreenhouseGas Emissions When composted aerobically, carbon is released as CO rather than methane, a more potent greenhouse gas.
- Soil Enrichment Compost produced from biodegradable waste adds nutrients and organic matter to soils.
- Marine Protection Some biodegradable polymers break down more readily in marine environments, lessening the threat to marine life.
Comparison of Degradation Times
| Material | Typical Decomposition Time (Aerobic) | Typical Decomposition Time (Anaerobic) |
|---|---|---|
| Paper (uncoated) | 24 weeks | 12 months |
| Cardboard | 13 months | 36 months |
| PLA (industrial compost) | 13 months | 612 months |
| Wood (hardwood) | 612 months | 12 years |
| Food waste (home compost) | 28 weeks | 36 months |
How to Choose Truly Biodegradable Products
Not every product marketed as biodegradable meets scientific standards. Follow these guidelines:
- Look for certifications Look for labels such as EN 13432, ASTM D6400, OK compost or BPI certified. These confirm that the product meets defined compostability criteria.
- Check the endoflife route Some items are only biodegradable in industrial composters, not in a backyard pile.
- Read the material composition Materials based on natural polymers (cellulose, starch, polylactic acid) are more reliably biodegradable than blends with conventional plastics.
- Avoid biodegradable plastic bags Many are made from oxodegradable polymers that fragment into microplastics without true mineralisation.
- Consider the whole system A product may be biodegradable, but if it requires transport to a specialised facility, its carbon footprint could offset the benefits.
