How to manage organic waste

Heat treatment of organic waste

Food and drink producers and hospitality businesses can consider various other treatment systems involving the use of heat. These all require specialist facilities.

Incineration does not produce usable by-products, although the energy can be used to generate electricity. Many organic wastes have a high moisture content and may require drying before combustion.

Incinerator plants that burn only animal carcasses or parts of carcasses must be approved under the Animal By-Products Regulations, but are exempt from more onerous waste incineration controls. However, plants that burn other animal by-products must be permitted or licensed by the Northern Ireland Environment Agency.

Pyrolysis is the thermal destruction or decomposition of material occurring in the absence of oxygen. In fast pyrolysis, the waste degenerates to give vapours, aerosols and some charcoal. After cooling and condensation, a dark brown liquid is formed which has a heating value about half that of conventional fuel oil. Virtually any form of organic waste can be considered for fast pyrolysis.

Gasification is closely linked to pyrolysis. When waste material is heated with no more than around one-third of the amount of oxygen needed for efficient combustion, it gasifies to a mixture of carbon monoxide and hydrogen (synthesis gas or syngas) potentially with carbon dioxide and methane. The amount of oxygen and other conditions determine whether the biomass gasifies.

Biomass and biowaste gasification can improve the efficiency of large-scale biomass power facilities and specialised facilities.

In plasma gasification, waste is fed to a reactor where it is exposed to an electrically-generated plasma. The waste is heated to over 2,000 degrees Celsius, causing organic compounds to break down to form molecules such as hydrogen, carbon monoxide, carbon dioxide, water vapour and methane.

The gas from the reactor is suitable as fuel for a gas-fired generation unit or can be used as a feedstock for chemical processes such as methanol production.