Page 123 - Materials Chemistry, Second Edition

Life Cycle Assessment of Biodiesel from Palm Oil 109

the cultivation of FFB, palm oil milling and conversion into biodiesel are excluded
from the system boundary for this chapter. This assumption is based on the results
from previous studies (Schmidt 2007; Novizar and Dwi 2010) which report neg-
ligible contributions because on a basis of per kilogram inputs, small amount of
energy is accounted for when the energy embodied in the machinery is distributed
over the amount of outputs from the machine over its entire life cycle.
Again, the energy for constructing the biodiesel plant as well as the energy
production facilities, such as hydropower plants, thermal plants, has equally
negligible contributions of less than 1 % hence neglected in the system boundary
for this chapter. This is because, on per kilogram basis of biodiesel, the plant
would have very low energy and emission contributions since the energy
embedded in fixed inputs would have to be distributed over the total biodiesel
production during the lifespan of the plant (Schmidt 2007; Novizar and Dwi 2010).
The production of seeds (for nursery) and organic fertilizer is also excluded from
the system boundary. Organic fertilizers are assumed to be residues that are not
produced specifically for oil palm cultivation.
The functional unit (FU) in LCA appends a reference to which the input and
output resources are related. An FU of 1 kg of PME in Malaysia is chosen as the
reference unit for all the input and output streams as well as the potential envi-
ronmental effects.

4.1.2 Allocation Procedures

The choice of LCA allocation methods for multi-input/output process like biodiesel
from palm oil is critical in quantifying the environmental burdens of the coproducts
generated by the various unit operations (Tillman 2000) because they may have a
significant impact on the final results (Bernesson et al. 2006). Since biodiesel
production from palm oil generates many kinds of coproducts (by-products or
wastes) such as oil palm fronds, empty fruit bunches, glycerin (depending on the
raw material inputs and production processes employed), realistically the main
product (biodiesel) should not carry all the environmental burdens. Allocations of
such environmental burdens to the different coproducts are made based on ISO
14041 LCA allocation procedures. In this chapter, the main LCA allocation method
used is the system expansion where no allocation is made (‘avoiding allocation’).
By this method, all the major unit processes to be allocated are divided into sub-unit
processes. The PME is thus expanded to involve the other functions related to the
coproducts, but PME is allocated the most share of the energy consumption within
the process chain. This method has the advantage of modeling the indirect effects of
the environmental burdens on the coproducts (Ekvall and Finnveden 2001). As
reported by Bernessen et al. (2006) for systems whose coproducts can replace other
products in later processes, the expansion method of LCA allocation is suitable for
application in this chapter.