Development of a sap squeezing system from felled oil palm trunks for bioethanol production
Oil palm trees are felled and young trees are replanted in their place at an interval of approximately 25 years because of their decreased productivity. Consequently, the enormous amounts of felled trunks are disposed as wastes in the palm oil producing countries. We found that large quantity of fermentable sugars comparable to sugars taken from other sources such as sugar cane, etc. are accumulated in felled oil palm trunks during maturation. There is no available apparatus which can efficiently squeeze the sap from oil palm trunks, although some portions of old felled trunks are utilized for plywood manufacturing. So, we developed this new system to squeeze sap efficiently from oil palm trunks.
The squeezing system is a combination of the existing rotary lathe, a new shredder, and a new press mill. The inner part of the palm trunk (palm trunk core), whose bark and outer cover are removed, is crushed into small chips by the shredder, and then, the sap is squeezed from the small chips by the press mill (Fig1). The shredder is composed of two parts; the stage part, which rolls the palm trunk core and sends it to the cutting part (Fig 2-1A), and the cutting part, which shreds the palm trunk core into small chips (Fig 2-1B). The trunk core, which is sent to the cutting part, is stably supported by the receiving roller and roller press, and is shredded into small chips by rotary cutter.
The press mill has double mills (Fig 2-2). Each mill is composed of three rotary-hydraulic-press rollers. The small chips, which enter into the slots of the press mill, are squeezed in the first mill, and compressed chips from the 1st mill are squeezed again in the 2nd mill. The squeezed sap is collected in a pan under each mill, and the compressed residues are discharged via the eject chute to the outside of the press mill.
Since the fibers of the oil palm trunks are shorter and thicker than the ones of sugar cane, we improved the following points; (1) the press rollers of the mills have large grooves to apply to short and thick fibers, therefore, there were able to enhance the loading of the shredded chips; (2) the press rollers of the mill have low-cut chevron for efficient squeezing, therefore, these are able to suppress the slipping of the shredded chips in between the press rollers.
When the palm trunk core (15-20 cm in diameter, and 1.2m in length) was crushed into small chips in the shredder, and the shredded chips were squeezed by the press mill, the sap yield was maintained at around 80% under slow rolling speed (2.1 rpm on the 1st mill and 2.4 rpm on the 2nd mill) and high pressure (29.5 MPa on the 1st mill, and 32.5 MPa on the 2nd mill) (Table 1: Conditions 1 and 2). The press mill has a water jet pump between the 1st mill and the 2nd mill, therefore, it is able to increase the sap yield by adding water during pressing (Table 1: Condition 3 and 4). This system can maintain high sap yield (around 80% of sap recovery), and can process approximately 500kg of trunk per hour.
Although our shredder supports small size core (20cm in diameter, and 1.2m in length) after plywood manufacture, it is able to shred larger palm trunk cores by scaling-up the stage and cutting part of the shredder.
The shredder which crushed the inner parts of palm trunks (palm trunk core) into small chips (2-1), and the press mill which squeezed sap from the small chips (2-2)
Table 1. Conditions of the press mill for efficient sap squeezing
Japan International Research Center for Agricultural Sciences Post-harvest Science and Technology Division
- Term of research
- Responsible researcher
MURATA Yoshinori ( Post-harvest Science and Technology Division )
KOSUGI Akihiko ( Post-harvest Science and Technology Division )
ARAI Takamitsu ( Post-harvest Science and Technology Division )
MORI Yutaka ( Post-harvest Science and Technology Division )
- Publication, etc.
Mori et al. Japanese Patent Application No. 2009-238779.
Murata et al. Nikkei business daily 17-11-2009
Murata et al. (2009) The 6th Biomass-Asia Workshop
- Japanese PDF