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PALM DIESEL: AN OPTION FOR GREENHOUSE GAS MITIGATION IN THE ENERGY SECTOR

PALM DIESEL: AN OPTION FOR GREENHOUSEGAS MITIGATION IN THE ENERGY SECTOR

CHOO YUEN MAY*; MA AH NGAN*; CHAN KOOK WENG* and YUSOF BASIRON*

* Malaysian Palm Oil Board,P. O. Box 10620,50720 Kuala Lumpur, Malaysia.E-mail: [email protected]

Keywords: palm diesel, palm oil methyl esters, biodiesel, diesel substitute, greenhouse gas.

Date received: 5 March 2004; Sent for revision: 22 March 2004; Received in final form: 29 August 2004; Accepted: 8 September 2004.

Journal of Oil Palm Research Vol. 17 June 2005, p. 47-52

ABSTRACT

The fast diminishing energy reserves coupled with increasing energy consumption as a nation develops and

greater environmental awareness have led to an intensified search for viable alternate sources of energy.

Natural and renewable resources such as vegetable oils can be chemically transformed into clean-burning

biodiesel. Biodiesel is a fuel substitute that is biodegradable and can contribute to alleviating environmental

pollution. Research and developmental efforts have demonstrated that palm diesel (palm oil methyl esters) is

a good source for energy production. Palm diesel produced using patented PORIM/PETRONAS production

technology has been extensively tested as a diesel substitute in a wide range of diesel engines including

stationary engines, passenger cars, buses and trucks. Palm diesel exhibits fuel properties comparable to those

of petroleum diesel and can be used directly in unmodified diesel engines. The production and usage of palm

diesel has great environmental impact with its closed carbon cycle. A fuel switch from fossil fuel to palm diesel

will contribute greatly to the reduction of greenhouse gas (GHG) emissions that lead to global warming.

Therefore, palm diesel production, because of its contribution to lower GHG emissions, can generate carbon

credits under the Clean Development Mechanism (CDM) of the Kyoto Protocol 1997. The financial incentives,

like the attractive carbon credit scheme, would bring about an additional positive impact on the economic

viability of palm diesel production as a renewable fuel. Furthermore, exhaustive field trials have also shown

that diesel engines running on palm diesel do not emit black smoke. There are also reductions in carbon

particulates, carbon monoxide and sulphur dioxide. The effort and initiative to utilize palm oil as an alternative

energy source are also in line with the Malaysian Government’s five-fuel diversification policy to include

renewable energy as the fifth fuel.

INTRODUCTION

Three issues, the energy crisis in the mid 1970scoupled with the fast diminishing energy reserves,a greater environmental awareness and an increasingenergy consumption, have all led to an intensifiedglobal search for viable alternative sources of energy.In recent years, a great deal of attention has beendirected to plant-based resources for fuels,particularly fuels for diesel engines. Vegetable oils,

being renewable and biodegradable, have thegreatest potential as biofuel resources.

In 2002, the annual worldwide vegetable oilproduction was about 97.8 million tonnes, with 29.9million tonnes of soyabean oil, 25.0 million tonnesof palm oil, 13.3 million tonnes of rapeseed oil and7.6 million tonnes of sunflower oil (MPOB, 2003).The production of biodiesel in European Union (EU)countries and the U.S.A in 2002 was more than onemillion tonnes and about 0.54 million tonnes,respectively (Anon, 2003). Out of the worldproduction, 84% was from rapeseed oil, 13% fromsunflower oil, 1% from palm oil, 1% from soyabeanoil and 1% from other sources (Figures 1 and 2)(Korbitz, 2002). Biodiesel is made from palm

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JOURNAL OF OIL PALM RESEARCH 17 (JUNE 2005)

(Malaysia), coconut (Philippines), rapeseed (Europe)and soya (United States) oils. If the choice ofvegetable oil depends on the cost of production andreliability of supply, palm oil would be the preferredchoice. One reason is that oil palm is the highest oil-yielding crop (4-5 t ha-1 yr-1).

In line with international efforts in promoting theuse of green fuels to reduce air pollution, theMalaysian Government has expanded its four-fueldiversification policy to include renewable energyas the fifth fuel under the Eighth Malaysian Plan andthe Third Outline Perspective Plan for 2001-2010(OPP3). It is reported that Malaysia’s crude oilreserves stood at 3.39 billion barrels in 2001. Naturalgas reserves also declined to 82.5 trillion standardcubic feet (tscf) for the same period (PETRONAS,2002). At the current rate of production, the averagelives for Malaysia’s oil and gas reserves are 16 yearsand 32 years, respectively. If no new discoveries of

oil wells are made, Malaysia will be a nett importerof petroleum by the 2100s and thus alternativerenewable fuels have to be sought. Dieselconsumption in Malaysia in 2002 was 8.61 milliontonnes, 50% of that consumed by the transportationsector (Ministry of Energy, Communications andMultimedia, 2004). The diesel demand is expectedto increase steadily to keep pace withindustralization and growth of the economy. Inaddition, the government initiative in promotingrenewable energy, especially from oil palm biomass,has also been seen as a move towards another cleanand environment-friendly alternative fuel.

In the sixth edition of International EnergyAgency (IEA, 2002) published statistics on GHG, thetwo largest overall sources of emissions were fromenergy and agriculture. The energy sectorcontributes about 70% of the emissions, mainly inthe form of CO2, while agriculture contributes about

Figure 1. Raw materials for biodiesel production.

Figure 2. World production of biodiesel.

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20% of GHG emissions, mainly as CH4 and N2O (IEA,2002). The palm oil industry therefore has animportant role to play in the energy sector andcontribute to the reduction in emissions to slowdown climate change.

Biodiesel is the term that refers mainly to methylor ethyl esters derived from vegetable oils. It can alsorefer to pyrolysis products, diesel-vegetable oilblends, microemulsions of alcohols and water invegetable oils and fermentation butanol. The conceptof using vegetable oil as a fuel dates back to 1895when Dr Rudolf Diesel developed his engine to runon vegetable oil (Nitske and Wilson, 1965). Hesuccessfully demonstrated the engine at the WorldExhibition in Paris in 1900 using peanut oil as fuel.The use of methyl esters of vegetable oils as dieselsubstitute has been extensively evaluated in manycountries (Choo et al., 1997; Choo and Cheah, 2000;Choo and Ma, 2000; Korbitz, 2000).

PRODUCTION TECHNOLOGY OF PALMDIESEL

Commercially, methyl esters of fatty acids can bemanufactured either by esterification of fatty acidsor by transesterification of fat triglycerides. Thepredominant process for the manufacture of methylesters is transesterification of fats and oils withmethanol. The ester interchange, i.e. replacement ofthe glycerol component by methanol, takes placequite easily at low temperature, 50˚C to 70˚C, andunder atmospheric pressure with excess methanoland an alkaline catalyst such as sodium hydroxide(Sonntag, 1982; Kreutzer, 1984; Freedman et al., 1984;1986). These mild reaction conditions, however,require oils neutralized by alkaline refining, steamdistillation or pre-esterification of the free fatty acids.

Esterification may be carried out batchwise at200˚C to 250˚C under pressure. For high yield, thewater produced during the reaction has to beremoved continuously. Esterification can also becarried out continuously in a counter current reactioncolumn using superheated methanol (Kreutzer,1984). Esterification is the preferred method for esterpreparation from specific oil and fat fractions suchas palm stearin and olein.

Vegetable oils such as crude palm oil with varyingamounts of free fatty acids can be converted to estersin a continuous process by combining theesterification and transesterification processes. Thiswas successfully demonstrated in a 3000 tpy pilotplant (Choo et al., 1992). The novel aspect of thispatented process is the use of solid acid catalysts forthe esterification (Choo and Goh, 1987; Choo andOng, 1989; Choo et al., 1992). The reaction is carriedout below 100˚C at atmospheric pressure in a columnof solid catalyst. The resultant of the reaction

mixture, which is neutral, is then transesterified inthe presence of an alkaline catalyst. The conventionalwashing stage or neutralization step after theesterification process is obviated and this is aneconomic advantage.

This patented process can also be applied to otherraw materials such as palm oil products (palmstearin and palm olein) and used frying oil.

ENGINE PERFORMANCE OF PALM DIESEL

Crude palm oil methyl esters (palm diesel) weresystematically and exhaustively evaluated as dieselsubstitute from 1983 to 1994. These includedlaboratory evaluation, stationary engine testing andfield trials on a large number of vehicles includingtaxis, trucks, passenger cars and buses. All the testswere successfully completed. It is worth mentioningthat the tests also covered stationary engine testingand field trials with 30 Mercedes Benz of Germanymounted onto passenger buses running on threetypes of fuels, namely, 100% petroleum diesel, blendsof palm diesel and petroleum diesel (50:50) and 100%palm diesel. Each bus covered 300 000 km, theexpected life of the engines (total mileage coveredby the 10 buses on 100% palm diesel was 3.7 millionkm).

Generally, palm diesel has very similar fuelproperties to petroleum diesel (Table 1). Its specificgravity is slightly higher than that of petroleumdiesel. Palm diesel has higher cetane number (63)than petroleum diesel (less than 40) (Table 2). A highercetane number indicates a shorter ignition time delaycharacteristic and, generally, a better fuel. Althoughits viscosity is slightly higher than that of petroleumdiesel, the flow is satisfactory under warm weather.However, its high pour point of 15˚C limits its useas fuel to tropical countries only. It can be improvedby adding pour point depressants or other processesfor possible use in temperate climate countries.Furthermore, with very little or no sulphur, it doesnot contribute to SOx pollution. It can be used directly

Vegetable + Alcohol Esters + GlycerolOil

CH2OOCR1 R1COOMe CH2OH

CHOOCR2 + 3 MeOH R2COOMe + CHOH

CH2OOCR3 R3COOMe CH2OH

(Triglycerides) (Methanol) (Methyl (Glycerol)esters)

1 t 0.1 t 1 t 0.1 t

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as fuel in conventional diesel engines withoutmodification and obviously it can be used as dieselimprover.

No technical problem was reported throughoutthe field trial as long as the engines were maintainedaccording to their service manuals. The operatorswere not able to detect any difference in terms ofgeneral engine performance. The conclusionsderived from the engine evaluation are as follows:

• no modification of the engines is required;• the performance of engines running on palm

diesel is generally good, smooth and easy tostart with no knocking;

• the exhaust emission is much cleanercompared to petroleum diesel with lesshydrocarbon, CO2 and SO2; therefore the fuelis more environment-friendly;

TABLE 1. FUEL CHARACTERISTICS OF METHYL ESTERS OF CRUDE PALM OIL (CPO) AND CRUDE PALM STEARIN (CPS)

Test Methyl esters Methyl esters Malaysianof CPO of CPS diesel

Specific gravity 0.8700 @ 74.5˚F 0.8713 0.8330 @ 60.0˚FASTM D1290Colour (visual) Reddish Orange YellowSulphur content (% wt.) < 0.04 < 0.04 0.10IP 242Viscosity @ 40˚C (cSt) 4.5 4.6 4.0ASTM D445Pour point (˚C) 16.0 17.0 15.0ASTM D97Distillation: final recovery (ml) 98.0 98.5 -ASTM D86Gross heat of combustion (kJ kg-1) 40 135 39 826 45 800ASTM D2382Flash point (˚C) 174 165 98ASTM D93Conradson carbon residue (% wt.) 0.02 0.05 0.14ASTM D198

TABLE 2. CETANE NUMBER OF CRUDE PALM OIL (CPO) METHYL ESTERS, PETROLEUM DIESEL (from Europe) ANDTHEIR BLENDS

CPO methyl esters (%) Petroleum diesel (%) Cetane number (ASTM D613)

100 0 62.40 100 37.75 95 39.210 90 40.315 85 42.320 80 44.330 70 47.440 60 50.5

• the engine lubricating oil was not undulydiluted by the palm diesel and was stillusable at the recommended mileage;

• palm diesel does not produce an explosiveair-fuel vapour. With a higher flash point(174˚C compared to 96˚C for petroleumdiesel), it offers enhanced safety;

• for the buses under trial, the fuelconsumption of palm diesel was comparableto that from petroleum diesel (e.g. 3-4 kmlitre-1); and

• palm diesel shows good ignition property.It can be used as a cetane number/dieselimprover because of its high cetane number(62.4 compared to 37.7 for petroleum dieselfrom Europe).

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CARBON CREDITS FOR PALM DIESEL

Palm diesel can be used to replace conventional fuels,e.g. petroleum, coal and natural gas, to certain extentfor power production. However, at present, its higherproduction cost is the major obstacle to itswidespread use. The economics of the palm dieselproject can be enhanced by the recovery of usefulco-products such as carotenes, vitamin E, sterols,squalene, co-enzyme Q and phospholipids as wellas glycerol derivatives.

One main benefit derived from this renewablesource of energy is the reduction in emission of GHGsuch as carbon dioxide. The production andconsumption of palm diesel form a closed carboncycle (Figure 3). Oil palm draws carbon dioxide fromthe atmosphere to build its trunk, fronds, seed androots. When biodiesel (converted from palm oil) isburned and the leftover plant materials decompose,carbon from the fuel and plant matter is merely beingreturned to the atmosphere. This closed carbon cyclerecycles the carbon dioxide and, therefore, there isno accumulation of carbon dioxide in theatmosphere. It was reported that biodiesel (methylesters) produces 78% less carbon dioxide than diesel.According to the U.S. Department of Energy (2000),biodiesel produces 0.6898 kg carbon dioxide per litrecompared to 3.266 kg litre-1, which is about 4.7 timeshigher for petroleum diesel. Subsequently, as palmdiesel, because of its lower GHG emissions, cangenerate carbon credits under the CDM of the KyotoProtocol 1997.

Under the terms of Kyoto Protocol 1997 (a majorinternational initiative established to reduce thethreat of global warming), there is potential value totransact the GHG benefits by the palm oil industry

under the CDM. This mechanism allows emissionreduction projects to be implemented and creditsawarded to the investing parties. Financialincentives, like attractive carbon credits, shouldfurther enhance the economic viability of theserenewable fuels.

In 2002, Malaysia consumed 8.61 million tonnesof petroleum diesel. The transport sector aloneconsumed 4.63 million tonnes and generated 18.1million tonnes of carbon dioxide. Transport has alsobeen identified as one of the chief contributors to airpollution, particularly black smoke (from diesel) andcarbon dioxide. If 10% of the diesel (0.463 milliontonnes) were replaced by palm diesel, the industrywill be entitled to 1.81 million tonnes of carbon creditor USD 18.1 million at USD 10 t-1 of carbon dioxide.

CONCLUSION

Palm diesel has been previously found to be asuitable fuel for diesel engines. It can readily replacepetroleum diesel used for power generation andtransportation. A fuel switch from a fossil fuel torenewable fuels will contribute greatly to thereduction in GHG emissions that lead to globalwarming. Unlike petroleum diesel, it does notcontribute to the increase in carbon dioxide andhence, cause global climate change. Furthermore, theraw material can be replenished by growing of oilpalm, a perennial crop.

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ANON (2003). Biodiesel battles for bigger marketshare. Oils and Fats International Vol. 19 No. 4 (July2003).

CHOO, Y M and GOH, S H (1987). Esterification ofcarboxylic acid/glyceride mixtures. U.K. patent2148897.

CHOO, Y M and ONG, A S H (1989). Carboxylic acidesterification. U.K. patent 2161809.

CHOO, Y M; ONG, A S H; CHEAH, K Y and BAKAR,A (1992). Production of alkyl esters from oils and fats.Australian patent No. AU 626014.

CHOO, Y M; MA, A N and ONG, A S H (1997).Biofuel. Lipids: Industrial Applications and Technology(Gunstone, F D and Padley, F B eds.). Marcel DekkerInc., New York. p. 771-785.

CHOO, Y M and CHEAH, K Y (2000). Biofuel.Advances in Oil Palm Research (Yusof Basiron; Jalani,B S and Chan, K W eds.). Volume II. MPOB. p. 1293-1345.

Figure 3. The production and consumption of palmdiesel: a closed carbon cycle.

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FREEDMAN, B; BUTTERMFIELD, R O and PRYDE,E H (1986). Transesterification kinetics of soyabeanoil. J. Amer. Oil Chem. Soc., 63: 1375-1380.

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