Following is an explanation of the rendering process;

There are three basic levels of processing.


Level 1 processing

Level 2 processing

Level 3 processing


The production of conventional animal protein meals

The processing of animal material not fit for human consumption

The processing of animal material with a higher risk of containing TSE

Application Examples

Animal slaughter and processing wastes

Downer animals of all species except bovine

Specified Risk Materials (SRM) and bovine downers

Examples of products typically produced

Protein meals for inclusion in animal rations; eg meat and bone meal, poultry and feather meal, fish meal
May produce tallow for general use

Protein meals for inclusion in animal rations or for use as soil conditioners.
May produce tallow for general use1


TSE inactivation logs reduction


~ 3.5

- 4>6

1 Dependent upon jurisdiction

Essentially the process is the same as any standard low temperature rendering process with the exception of an altered treatment of the non tallow fractions. This means that most of the equipment necessary for a rendering plant is commercially available world wide from various manufacturers. The process can easily be scaled up or down according to operational requirements and can effectively be applied to all animal waste rendering applications.

The variation of the non tallow component is that this is simply treated with an alkali and dried in a rotary dryer with a high velocity of warm air. There is no requirement for steam in the drying process. The equipment is simple in design giving savings in initial capital cost, maintenance costs and operational costs. Most if not all dryers used in low temperature plants commercially operational are unsuited to the ADT process as they operate at too higher temperatures and serious product degradation will occur.

Alternatively if there is current rendering equipment in place, then the hydrolysis of the protein meals can be applied post production.

The advantages of the ADT process

Level 1 Processing.

  1. Energy efficiencies. Energy costs for rendering are usually the biggest single operating cost. In documented evidence savings of up to 25% in heat energy costs can be achieved when compared with a state of the art modern high temperature plant. Additional energy savings can be made with the use of low grade waste heat sources such as heat recovery from the exhaust, cold room condensers or even solar collection in some cases.
  2. Environmental considerations. The exhaust from the tallow separation is standard according to the equipment installed and usually only requires only a small biofilter for odour control. The exhaust from the dryer (2700 – 4500    SOU/M 3) will only have emission levels equivalent to a standard rendering plant biofilter (3000 – 9000 SOU/M 3) which is 20 times less than a standard continuous high temperature cooker.
  3. Meat and bone meal sterility. Most efficient plants can produce a meat and bone meal free of any bacterial contamination as is the case with the ADT process. However with the meat and bone meal produced with the ADT process, if post production contamination occurs as is often the case with such species as Salmonella spp and coli , these and other species are actually killed off in the meals due to the residual alkalinity.
  4. Protein meal quality. Meat and bone meal digestibility studies have demonstrated that the meals produced are of the highest quality and that essential amino acids such as lysine are almost totally available. Due to the hydrolytic process, water is biochemically bound into the meals as well as the alkali treatment being retained. This gives a higher dry matter yield of 5 – 7 % with a corresponding apparent reduction in protein content; therefore a typical 50% CP meat and bone meal will be reduced to 46 - 48% CP but with the higher yield and better digestibility.

A typical analysis for a material producing a 50% CP meal in a conventional system will produce under the ADT process:


+ 5 – 7 %

Crude Protein

46 – 48 %


7 – 8 %


34 – 36 %

Pepsin digestibility

92 – 94 %

Biochemical theory suggests that there may be the formation of some unwanted compounds with the alkaline hydrolysis of proteins. Tests for some of these have been conducted including di-amino acid formation and all tests have concluded that no unwanted or toxic compounds have ever been detected. Additionally commercial breeding swine have been fed meat and bone meal produced by the ADT process at normal inclusion rates in their feed for well over 2 years with no adverse results.

Level 2 processing.

This is the general waste processing level of the ADT process. The system can be applied from very small, simple localised units with a capacity as low as 100 kg / hour, typically “in house” waste processing, to large facilities with a capacity of > 20 tons per hour. Typically tallow separation is not applied to units < 2 tons/hour.

The analyses of the meals produced will be dependent on input material; however they are excellent soil conditioners with levels of TSE inactivation ranging from 3.5 logs reduction to > 6 logs reduction depending on the treatments applied.

Level 2 processing displays similar energy and environmental factors as in level 1 processing.

Level 3 processing.

This level of processing was specifically developed for the processing of SRM and Category 2 material.

The general process is the same as Level 1 processing but with a very aggressive hydrolysis stage to ensure that all protein and other bipolmeric material is hydrolysed to a residual molecular size of < 5 KDa. This ensures that any TSE infectivity will be reduced by > 6 logs so the material can then be safely applied as a soil conditioner.