Environmental Engineering Reference
In-Depth Information
and thus does not contribute to the net increase in atmospheric CO
2
. From 1996 to 2008, the biodiesel
production capacity in the European Union increased by a factor of 13 from 591,000 tons to a total
of 7.755 million tons (Bockey 2002, 2004; EBB 2009).
Further utilization of biodiesel is anticipated because of initiatives around the world aimed at
promoting its use. The European Union Directive 2009/28 is aiming at replacing 10% of all trans-
port fossil fuels with biofuels from renewable sources by 2020 (European Union 2009). The current
trends and legislation will create momentum for greater biodiesel production and consumption.
Thus, there will be an upward course and new market opportunities for biodiesel.
Methyl esters of vegetable oils have been successfully evaluated as a diesel substitute worldwide
(Choo et al. 1997; Choo and Ma 2000). For example, the following have been studied: rapeseed
methyl esters in Europe, soybean oil methyl esters in the United States, sunflower oil methyl esters
in Europe and the United States, and palm oil methyl esters in Malaysia. Because the choice of
vegetable oil depends on the cost of production and reliability of supply, palm oil would be the
preferred choice because it is the highest oil-yielding crop (4-5 tons/ha per year) among all of the
vegetable oils.
Malaysia began its extensive biodiesel program in 1982. This includes development of production
technology to convert palm oil to palm oil methyl esters (palm biodiesel), pilot plant studies of
palm biodiesel production, and exhaustive evaluation of palm biodiesel as a diesel substitute in
conventional diesel engines, both stationary and in vehicles.
CPO can be readily converted to its methyl esters. The production by MPOB (then Palm Oil
Research Institute of Malaysia, PORIM)/PETRONAS patented technology (Ong et al. 1992) has
been successfully demonstrated in a 3000 tons/year pilot plant (Choo et al. 1995,
1997; Choo
and Cheah 2000). The novel aspect of this patented process is the use of solid acid catalysts for
the esterification. The product of the reaction mixture, which is neutral, is then transesterified in
the presence of an alkaline catalyst. The conventional washing stage or neutralization step after the
esterification process is obviated, creating an economic advantage. This patented process can also
be adopted for other palm oil products such as crude palm stearin and crude palm kernel oil as well
as other raw materials such as used frying oil.
CPO methyl esters (palm biodiesel) were systematically and exhaustively evaluated as a diesel
fuel substitute from 1983 to 1994 (Choo et al.
1995, 2002b). This included laboratory evaluations,
stationary engine testing, and field trials on many vehicles including taxis, trucks, passenger cars,
and buses. All of these tests were successfully completed. It is worth mentioning that the tests also
covered stationary engine testing and field trials with 36 Mercedes Benz engines mounted onto
passenger buses running on three types of fuels: 100% petroleum diesel, blends of palm biodiesel
and petroleum diesel (50:50), and 100% palm biodiesel. Each bus covered 300,000 km, which is
the expected life of the engines (total mileage covered by the 10 buses on 100% palm diesel is
3.7 million km). The results from this exhaustive field trial are promising. Fuel consumption of palm
biodiesel by volume was comparable to the petroleum diesel. Differences in engine performance are
so small that an operator would not be able to detect. The exhaust gas was found to be much cleaner;
it contained comparable NO
x
, but fewer hydrocarbons, CO, and CO
2
. The very obvious advantage
is the absence of black smoke and SO
2
from the exhaust.
Methyl esters from CPO produced by MPOB/PETRONAS technology have very similar fuel
properties to the petroleum diesel (Table 17.10). They also have a higher cetane number (63) than
diesel (<40) (Table 17.11). A higher cetane number indicates shorter ignition time delay characteristics
and generally a better fuel. These methyl esters can be used directly as fuel in unmodified diesel
engines or, of course, for blending traditional diesel. Compared with CPO, these methyl esters have
very much improved viscosity and volatility properties and do not contain gummy substances.
However, it has a pour point of 15°C, and this has confined its utilization to tropical countries.
In recent years, research efforts have produced palm biodiesel with a low pour point (without
additives) that can be produced to meet seasonal pour point requirements, e.g., spring (-10°C),
summer (0°C), autumn (-10°C), and winter (-20°C). The MPOB patented technology (Choo et al.
