Biodegradability is the ability of organic substances and materials to be degraded into simpler substances through the enzymatic activity of microorganisms. If this biological process is complete, there is a complete conversion of the organic starting substances into simple inorganic molecules such as water, carbon dioxide and methane.
The phenomenon of biodegradation is part of the natural carbon cycle of life on earth. Thanks to the photosynthesis activity of plants and algae, and the inexhaustible energy of the sun, carbon dioxide is removed from the atmosphere to synthesize the sugars and other substances used by plants to grow and develop. Through the food chain, the flow of matter and energy passes from plants to herbivores and from herbivores to carnivores. When plant and animal organisms die, micro-organisms, present everywhere in the environment, feed on the organic material through biodegradation processes and release water and carbon dioxide into the atmosphere, thus closing the cycle.
By imitating and exploiting these natural processes, even organic waste from human activities can be removed through biodegradation.
In order for this to be effective, however, it is necessary to identify the ideal environment in which the phenomenon can be maximized and to define a duration of the process that is "industrialisable" and compatible with the production rates of the organic waste itself.
In nature, in fact, each organic waste has its own biodegradation time; straw and wood will take longer than starch and cellulose. Similarly, in cold and dry environments the biodegradation processes will be slower than in warm and humid environments.
This means that biodegradation is strongly influenced by the chemical nature of the substance or material to be biodegraded and the biodegradation environment. The environments in which biodegradation occurs at a consistent rate and can be managed industrially are composting and anaerobic digestion.
In these systems, solid organic waste can be treated, including manufactured goods (e.g. biodegradable plastics) that have a biodegradation rate compatible with such treatments. In the case of composting, mature compost (which is a fertilizer) will be obtained, and in the case of anaerobic digestion (followed by stabilisation in composting) biogas (and therefore energy) and compost will be obtained.
Another biologically active environment is soil: some materials can biodegrade completely in soil, and this property can be exploited in specific applications such as mulching.
Strictly necessary