Organic waste materials, such as food scraps, crop residues and manure are collected and sorted to remove non-organic contaminants such as plastics and metals.

In certain circumstances, this organic waste will be prepared before being placed in a digester such as being shredded.

Bio digesters, such as the Ecoco Solutions range of compost machines, will convert food waste into compost by breaking down the organic material through a biological process that takes place in a controlled environment. The two primary byproducts of this process are biogas and digestate, a solid material that can be used for compost.

Source: EPA

The anaerobic digestion process

The breakdown of food waste happens in a series of biological stages, facilitated by different microorganisms. These key stages of this digestion process include:

Hydrolysis

The first stage of the bio digestion process, hydrolysis involves the breaking down of complex molecules such as carbohydrates, fats and proteins into simpler compounds such as sugars, amino acids and fatty acids.

Acidogenesis

Once the hydrolysis process has taken place, the compounds are further broken down into volatile fatty acids, alcohol, hydrogen and carbon dioxide. This is where the organic acids are formed.

Acetogenesis

During this stage of the process, the volatile fatty acids are converted into acetic acid, along with carbon dioxide and hydrogen.

Methanogensis

The final stage of the process, methanogenic bacteria will convert acetic acid, hydrogen and carbon dioxide into methane and water. The methane produced is a biogas, which can be used for energy, while the remaining material is digestate. This solid or semi-solid material that remains afet anaerobic digestion is a nutrient-rich substance that contains nitrogen, phosphorus and potassium, which are vital for plant growth.