About Rendering
What are animal by- products?
For various reasons not all of slaughtered animal carcasses end up for human consumption.
For various reasons not all of slaughtered animal carcasses end up for human consumption. Some of the parts are plainly inedible, some are not allowed to be used for human consumption and some are taken out of the food chain as precautionary measures to prevent disease transmission. Increasingly, however, meat is taken out of the human food chain as a matter of customer choice.
It has been estimated that humans directly consume only 68% of a chicken, 62% of a pig, 54% of a bovine animal and 52% of a sheep or goat. The remainder of the carcass and animals not fit for human consumption are termed animal by-products and these form the raw material for rendering.
These raw materials come from a variety of sources such as butcher shops, restaurants, supermarkets, farmers and meat and poultry processors.
Within Europe animal by-products are controlled by strict regulations. These regulations recognise the different types of animal by-products and the risks that they can pose. The regulations classify animal by-products into three categories based on their potential risk to animals, the public or to the environment, and sets out how each category must or may be disposed of.
By-product categories
- Category 1 materials are animal by-products that are kept out of any food chain to control environmentally harmful products and to prevent the spread of certain diseases. Category 1 materials must be completely disposed of by incineration or landfill; landfill can only occur after suitable rendering treatment.
- Category 2 materials are animal by-products from animals showing signs of infectious diseases or killed as part of measures to control the spread of such diseases. They can be disposed of in the same way as Category 1 materials but can also be recycled for uses other than feeds after appropriate treatment (e.g. biogas, composting, oleo-chemical products).
- Category 3 materials are animal by-products from healthy slaughtered animals. Almost all category 3 materials would be fit for human consumption but are not consumed for reasons of culture and customer choice. As well as being treated in the same way as category 1 and 2 materials category 3 materials can be recycled in approved plants for the manufacture of pet feeds and fertilisers.
Since 1st May 2003 there has been a common regulation across Europe controlling animal by-products click here to read the regulation
The Regulation requires that only animal by-products derived from animals fit for human consumption (category 3) may be used for animal feed. In other words, the same health standards required by EU legislation for human food will be required for animal feed.
In order to guarantee that animal by-products derived from animals unfit for human consumption cannot enter the human food or animal feed chain, the following requirements have been introduced:
- complete separation during collection, transport, storage, handling and processing of animal waste not intended for animal feed or human food;
- complete separation of plants dedicated to feed production from plants processing other animal waste destined to destruction;
- stricter rules for traceability of animal by-products, including the control of movements of BSE specified risk material by a record keeping system and accompanying documents or health certificates, and visual markers for animal proteins and fats intended for destruction.
The Regulation also requires reliable traceability and identification systems of marking for certain materials intended for specific disposal options (e.g. incineration of meat and bone meal) to avoid possible frauds or risk of diversion of unauthorised products into food and feed. More detailed information on the Categories of Animal By-products and the regulations controlling them can be found on the DEFRA web-site (http://www.defra.gov.uk/animalh/by-prods/publicat/bp-regs4.pdf).
What is rendering?
Aside from reducing the amount of waste produced by the meat processing industry, these rendered fats and proteins have many uses
Rendering is a cooking and separating process that uses animal and poultry by-products including bone, fat, hide and feathers to produce purified fat and protein products. These inedible portions of animals are cooked at high temperatures to remove moisture, kill bacteria and separate out the fat and protein.
Aside from reducing the amount of waste produced by the meat processing industry, these rendered fats and proteins have many uses. Traditionally, the fat was used to make candles and soap; now it is used in the manufacture of steel, pet and livestock feed, and as a source of fatty acids and glycerine for the chemical industry. The protein is used in the production of gelatin and cosmetics and is sold to feed manufacturers as a high quality protein source, primarily for swine, poultry and pet feeds.
The rendering process
raw materials are stored for the minimum length of time to keep them as fresh as possible
All rendering plants contain some or all of the following process steps and the figure below shows how they fit together in the overall plant.
- raw material reception - this is where the incoming raw materials enter the facility and is usually characterized by some form of double door to provide an odour lock to prevent the release of odours during unloading operations.
- storage and handling of raw materials - raw materials are stored for the minimum length of time to keep them as fresh as possible. Usually they will be stored in lidded hoppers which have odour extraction and control fitted to them. To comply with animal by-products regulations rendering facilities need to keep accurate records of what raw materials are received, when they are received and when they are processed. Rendering plants also keep their own internal logs of raw materials and their condition so that the production schedule is arranged so as to minimise degradation of materials.
- size reduction of raw materials - before being passed into the rendering process the raw materials are reduced in size. This is important in allowing accurate heat transfer during the rendering process which ensures that all parts of the rendered materials receive sufficient treatment to fully sterilise them.
- processing of materials - the crushed raw materials are heated in the rendering plant, of which almost all in the UK are continuous units. The rendering equipment will produce a defined temperature and residence time that will achieve sterilisation of the raw materials. All rendering plant is checked and validated by DEFRA to exacting European standards before it can receive an operating license.
- treatment of odorous emissions - because it deals with natural by-products (some of which may be quite old before they are even sent to the rendering plant) rendering does produce odours. All plants go to great lengths to fit odour capture and extraction equipment and to fit effective odour abatement equipment. In the past few years many UK rendering plants have spent several hundreds of thousands of pounds fitting thermal oxidisers to give the best possible destruction of captured odours.
- storage of processed materials - after rendering the meal and fat are separated and stored prior to being dispatched off the site.
- washing and cleaning - vehicles delivering the animal by-products, processing equipment and the general rendering plant building all require regular washing and cleaning. Plants aim to minimise the amount of water used, and effluent produced, by having policies on housekeeping and spill procedures that use dry cleaning as far as possible; they also design their equipment and operations to be as leak proof as practically possible.
- effluent treatment (on site or to discharge) - the washing and cleaning operations produce effluent. The rendering operation itself also produces quantities of water that is driven off the product during rendering. Some plants pass this water vapour through the thermal oxidiser directly but others condense out the majority of the water first. All effluent produced is either treated in an approved process on site or sent off site for treatment at a suitable treatment works.