Page 115 - Materials Chemistry, Second Edition

Life Cycle Assessment of Biodiesel from Palm Oil 101

leave about 11 mg (per kg body weight) of its content on the sprayer’s skin after
some few minutes (DEQ 1990).
Oil palm plantation has resulted in rampant deforestation, burning of forests,
peat land degradation, and habitat loss of critically endangered species, and this
direct land use has brought about significant emission of CO 2 and N 2 O into the
atmosphere. Forest fires used to clear vegetation for oil palm plantations are one
source of CO 2 . The smoke produced through forest burning can contribute to GWP
as well as posing serious health threats to plantation workers and close neighbors.
For instance, in Malaysia and Indonesia, 1997 recorded the highest CO 2 emissions
resulting from bush burning since 1957 (Román-Cuesta et al. 2011). An estimated
0.81–2.57 gigatons of carbon was released into the atmosphere by the fires:
13–40 % of the mean annual global carbon emissions from fossil fuels in that year
alone (Clay 2004). Again, in Indonesia and Malaysia, over 140 and 47 land
mammalian species are endangered, respectively, as a result of oil palm plantation.
Over 45 % of the total peat land has been converted to oil palm plantation due to
the increase demand of palm oil, and this has put the leading producers of palm oil
on top of major emitters of greenhouse gas (GHG) in the world. Currently, the
annual cropland for oil palm plantation in Indonesia and Malaysia contributes
about 2.63 t CO 2 eq. and 2.44 t CO 2 eq. per tonne FFB processed, respectively
(Clay 2004). The situation becomes aggravated during deforestation and bogs
draining which releases the peat bogs that store great quantities of carbon. Hence,
appropriate management of plantation and the use of the biomass from the plan-
tation as well as the processing residues from palm oil production (fibers, kernel
shells, POME) for biofuel can have an effect on reducing GHG emissions.

2.2 Palm Oil Milling (Oil Extraction)

Figure 3 summarizes the main processes involved in the milling or extraction of
palm oil from FFB. Sterilization of FFB is done in a steamer (pressurized cages) at
about 2–3 bars to ameliorate the content of FFA which could reduce the quality of
the oil. A rotation drum stripper is used to thresh the fruitlets from the sterilized
bunches and the fruitlets sent to the digester. The EFB are also used as mulch in
the oil palm plantation.
The digester then removes the fruits’ mesocarp from the nuts by continuously
heating the fruits with steam which helps to open the oil cells in the mesocarp for
effective oil extraction. The oil extraction is done with the help of screw press
where the press cake and nuts are conveyed to the palm kernel crushing (PKC)
plant and the pressed liquor also sent to a vibrating screen where it is diluted. The
oil is then clarified and purified to remove dirt and moisture before it is dried. The
sludge (comprising mainly water soluble parts of the palm fruits and suspended
materials like palm fibers) from the clarifier is desilted and further sent to the
centrifuge to recover the excess oil which is recycled into the clarifier. The water–
sludge mixture (palm oil mill effluent, POME) is then sent to the effluent treatment