Development of sap compressing systems from oil palm trunk

In an attempt to utilize felled palm trunks, we found that they contain a large quantity of sap, and that abundant glucose and other fermentable sugars exist in the sap. In this study, we developed a prototype system for compressing the sap from oil palm trunks; it is composed of a rotary lathe, a shredder, and a compressing mill. A high compression efficiency of the mill was maintained (a sap recovery of ∼80%) by properly preparing the trunks, which included peeling the bark and the outer layer of the trunks. In addition, a higher compression efficiency was obtained with a relatively slow rotation of the mill. Consequently, the net energy ratio (NER) reached 4.8 when the sugar concentration in the sap was 79 kg m−3. This is the first paper about new developed systems for sap compressed from oil palm trunk.