An Easy Laboratory Method for Optimizing the Parameters for the Mechanical Densification Process: An Evaluation with an Extruder

Currently, Mexico and most developing countries have problems during dry seasons, due to shortage of forage which may cause economic losses to cattlemen. But, Mexico produces about 60 million tons of agricultural crop residues every year. An interesting use for these residues is to produce animal feed after harvesting as an efficient alternative to cattle feed. Some handling problems are associated with the low density of these materials, such as storage and transportation. In order to solve these problems, the densification process is proposed as a solution. However, before selecting or designing any commercial machine, it is necessary to know the mechanical behavior of the material and the processing conditions. The main objective of this work is to present an easy laboratory method to find optimal conditions of the densification process for producing animal feed. The studied material was a sheep feed, which consisted mainly of alfalfa hay and corn crop residues. An open-end die was used to simulate the extrusion process. A Box Behnken design was run in the laboratory to find the best levels of the factors (moisture content, temperature and die length) on the responses (extrusion pressure, pellet density, and specific energy consumption). Afterwards, three runs were developed in the laboratory to confirm the optimum results. Also, same levels of the factors were used on real scale single-screw extruder to confirm the laboratory results.