950,588 ha of palm oil farms are RSPO-certified (NEPCon
2018). The much stricter environmental policies implemented
by major importers and pressure exerted by NGOs affected
the prospect of oil palm industry, hence the growth of palm oil
output must increasingly focus on productivity improvements
such as FFB and CPO yield improvements, as well as speed
up replanting activities.
2 Palm Oil Mill Processes and Waste
Treatments
2.1 Palm Oil Production Process
Two common methods to extract CPO by the mills are either
using a dry or wet process. The most common method used
is the wet process which involves a large amount of water
and steam in the process to remove dirt and to sterilize the
fruit bunch in different steps, thus generating a high volume
of effluent termed as palm oil mill effluent (POME). It poses
a substantial threat to water pollution if released directly into
the water bodies without treatment. Figure 8 illustrates the
typical extraction process of palm oil followed by the
description of each stage (Hashim et al. 2012).
2.1.1 Sterilizing Fresh Fruit Bunch (FFB)
The first stage of crude palm oil extraction is the sterilization
or steaming process (Hashim et al. 2012). The fresh fruit
bunches are exposed to high-temperature pressurized steam at
140 °C for 75–90 min to deactivate the natural hydrolytic
enzymes which breakdown oil to free fatty acids. Exposure at
high temperature helps for easier detachment of fruits from
bunches in the subsequent process of stripping and threshing
(Liew et al. 2015; Rupani et al. 2010). The sterilization process stage is crucial to maximize fruit recovery (Junaidah
et al. 2015). The high volume of steam condensate from
sterilization is one of the main contributors to the mill effluent.
2.1.2 Stripping or Threshing
The sterilized FFB are transported to the thresher platform
using a scraper conveyor. Fruits are lifted and dropped
constantly in a rotary drum stripper to strip off and separate
the oil fruits or pulps from the bunches. A bucket conveyor
is used to collect the detached pulps and to transfer into a
digester (Iskandar et al. 2018; Ahmed et al. 2015). The
remaining empty fruit bunches (EFB) are discarded as a
solid waste (Rupani et al. 2010).
2.1.3 Digestion and Pressing for Crude Palm Oil
(CPO) Extraction
Digestion is a process of palm oil extraction by breaking
down the fruits via steam-heating in a vertical cylindrical
digester. Fruits are softened at 80–90 °C using a steam
jacket or by direct live steam injection (Ahmed et al. 2015).
Under high temperature and pressure, the oil-bearing cell of
the fruits will break to release the oil and a screw press
machine is used to enhance the extraction process. Hot water
is added during this process to enhance the oil mixture
product known as crude palm oil. Once CPO is extracted,
fine solids and water are removed using a vibrating screen,
hydro cyclone and decanters (Rupani et al. 2010).
2.1.4 Clarification and Purification of Crude Palm
Oil
Extracted CPO slurries contain a mixture of 35–45% oil, 45–
55% water and small portions of fibrous materials (Rupani
et al. 2010; Iskandar et al. 2018; Ahmed et al. 2015). The
oil–water mixture is further processed in a clarification tank
to collect oil by constantly skimming-off oil at the top of the
tank using a rotary strainer. The temperature of the tank is
maintained at 90 °C to keep the oil viscosity low for easier
separation. The bottom phase liquid in the tank is passed
through a centrifugal separator to separate CPO and oil
sludge. The recovered oil is returned to the clarifier and the
sludge is sent to a treatment facility for disposal. The CPO is
further refined using a centrifuge and vacuum dryer to
remove more solid residues prior to transferring into a
storage tank (Ahmed et al. 2015). The oil sludge produced
during these clarification processes contributes to the overall
wastewater of this industry or also known as palm oil mill
effluent (Iskandar et al. 2018).
2.1.5 Depericarping and Nut Fibre Separation
During the screw pressing process, the crude oils are
extracted from the fruit, forming the leftover press cake
which consists of moisture, nut and oily fibre. The pressed
cakes are sent to a depericarper to separate the fibre to be
used as fuel at the boiler house (Ahmed et al. 2015).
2.1.6 Separation of Kernels and Drying
The remaining nut will undergo winnowing and a hydro
cyclone process to separate palm kernel from its shell. The
liquid component or wastewater from the hydro cyclone is
discharged, while the palm kernel will undergo a drying
process in silos (Iskandar et al. 2018; Ahmed et al. 2015).
126
R. Shamsuddin et al.
2018). The much stricter environmental policies implemented
by major importers and pressure exerted by NGOs affected
the prospect of oil palm industry, hence the growth of palm oil
output must increasingly focus on productivity improvements
such as FFB and CPO yield improvements, as well as speed
up replanting activities.
2 Palm Oil Mill Processes and Waste
Treatments
2.1 Palm Oil Production Process
Two common methods to extract CPO by the mills are either
using a dry or wet process. The most common method used
is the wet process which involves a large amount of water
and steam in the process to remove dirt and to sterilize the
fruit bunch in different steps, thus generating a high volume
of effluent termed as palm oil mill effluent (POME). It poses
a substantial threat to water pollution if released directly into
the water bodies without treatment. Figure 8 illustrates the
typical extraction process of palm oil followed by the
description of each stage (Hashim et al. 2012).
2.1.1 Sterilizing Fresh Fruit Bunch (FFB)
The first stage of crude palm oil extraction is the sterilization
or steaming process (Hashim et al. 2012). The fresh fruit
bunches are exposed to high-temperature pressurized steam at
140 °C for 75–90 min to deactivate the natural hydrolytic
enzymes which breakdown oil to free fatty acids. Exposure at
high temperature helps for easier detachment of fruits from
bunches in the subsequent process of stripping and threshing
(Liew et al. 2015; Rupani et al. 2010). The sterilization process stage is crucial to maximize fruit recovery (Junaidah
et al. 2015). The high volume of steam condensate from
sterilization is one of the main contributors to the mill effluent.
2.1.2 Stripping or Threshing
The sterilized FFB are transported to the thresher platform
using a scraper conveyor. Fruits are lifted and dropped
constantly in a rotary drum stripper to strip off and separate
the oil fruits or pulps from the bunches. A bucket conveyor
is used to collect the detached pulps and to transfer into a
digester (Iskandar et al. 2018; Ahmed et al. 2015). The
remaining empty fruit bunches (EFB) are discarded as a
solid waste (Rupani et al. 2010).
2.1.3 Digestion and Pressing for Crude Palm Oil
(CPO) Extraction
Digestion is a process of palm oil extraction by breaking
down the fruits via steam-heating in a vertical cylindrical
digester. Fruits are softened at 80–90 °C using a steam
jacket or by direct live steam injection (Ahmed et al. 2015).
Under high temperature and pressure, the oil-bearing cell of
the fruits will break to release the oil and a screw press
machine is used to enhance the extraction process. Hot water
is added during this process to enhance the oil mixture
product known as crude palm oil. Once CPO is extracted,
fine solids and water are removed using a vibrating screen,
hydro cyclone and decanters (Rupani et al. 2010).
2.1.4 Clarification and Purification of Crude Palm
Oil
Extracted CPO slurries contain a mixture of 35–45% oil, 45–
55% water and small portions of fibrous materials (Rupani
et al. 2010; Iskandar et al. 2018; Ahmed et al. 2015). The
oil–water mixture is further processed in a clarification tank
to collect oil by constantly skimming-off oil at the top of the
tank using a rotary strainer. The temperature of the tank is
maintained at 90 °C to keep the oil viscosity low for easier
separation. The bottom phase liquid in the tank is passed
through a centrifugal separator to separate CPO and oil
sludge. The recovered oil is returned to the clarifier and the
sludge is sent to a treatment facility for disposal. The CPO is
further refined using a centrifuge and vacuum dryer to
remove more solid residues prior to transferring into a
storage tank (Ahmed et al. 2015). The oil sludge produced
during these clarification processes contributes to the overall
wastewater of this industry or also known as palm oil mill
effluent (Iskandar et al. 2018).
2.1.5 Depericarping and Nut Fibre Separation
During the screw pressing process, the crude oils are
extracted from the fruit, forming the leftover press cake
which consists of moisture, nut and oily fibre. The pressed
cakes are sent to a depericarper to separate the fibre to be
used as fuel at the boiler house (Ahmed et al. 2015).
2.1.6 Separation of Kernels and Drying
The remaining nut will undergo winnowing and a hydro
cyclone process to separate palm kernel from its shell. The
liquid component or wastewater from the hydro cyclone is
discharged, while the palm kernel will undergo a drying
process in silos (Iskandar et al. 2018; Ahmed et al. 2015).
126
R. Shamsuddin et al.