Guide

How to manage organic waste

Physical and chemical treatment of organic waste

There are various other physical and chemical methods that food and drink producers and hospitality businesses can use to treat organic waste. However, these tend to be large-scale solutions, so smaller businesses are likely to need other organisations as partners or contractors.

Rendering involves the partial recovery of materials from animal by-products (including former foodstuffs) by crushing and grinding, followed by heat treatment to reduce the moisture content and kill micro-organisms.

Renderers process most animal by-products from the meat production chain to produce tallow and protein meal. Tallow is used in industries as diverse as paint manufacture and tyre production, as well as for fuel.

Autoclaving is a conventional combination of heat treatment under pressure and has been used for many years as a sterilisation process. Heat is applied to material either directly as steam or by heating the vessel to release steam from the moisture content of the material being treated. This increases the pressure within the closed vessel.

Organic waste such as food and vegetable residues, paper and cardboard, etc will result in an organic 'wool' or fibre when treated in an autoclave.

Hydrolysis is a process in which chemical bonds are broken by the 'insertion' of water between the atoms in the chemical bond. This destroys the protein/amino acid framework of organic waste and is particularly suited to high-risk wastes, such as high-level animal by-product wastes.

Microwave treatment of organic waste tends to be small scale and is predominantly used to sterilise high-risk material.

Microwave systems are either batch or through-flow, and may be used alone or in combination with steam injection systems, which increase the efficiency of the microwave process and help to raise its temperature to pasteurisation levels.