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Renewable and Sustainable Energy Reviews

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A review of biomass-derived heterogeneous catalyst for a sustainablebiodiesel production

Sharifah Hanis Yasmin Sayid Abdullaha, Nur Hanis Mohamad Hanapia, Azman Azida,Roslan Umara, Hafizan Juahira,b, Helena Khatoonc, Azizah Enduta,d,⁎

a East Coast Environmental Research Institute, Universiti Sultan Zainal Abidin, Gong Badak Campus, 21300 Kuala Terengganu, Terengganu, Malaysiab Faculty of Bioresources and Food Technology, Universiti Sultan Zainal Abidin, Tembila Campus, 22000 Besut, Terengganu, Malaysiac School of Fisheries and Aqua-Industry, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysiad Faculty of Innovative Design and Technology, Universiti Sultan Zainal Abidin, Gong Badak Campus, 21300 Kuala Terengganu, Terengganu, Malaysia

A R T I C L E I N F O

Keywords:BiodieselBiomassHeterogeneous catalystSolid base catalystSolid acid catalyst

A B S T R A C T

Biodiesel production is commonly carried out through the process of transesterification reaction. The reaction isexpedited with a suitable catalyst either homogeneous or heterogeneous. The selection of an appropriate catalystdepends on the amount of free fatty acids in the oil. Recently, homogeneous catalysts are widely chosen forbiodiesel production in large scale operation. However, they are toxic, highly flammable and corrosive in nature.

Furthermore, the use of homogeneous catalyst produced soaps as by-product and large amount ofwastewater that required additional processing technologies and cost for proper disposal. On the contrary,heterogeneous catalysts are capable to overcome the problems faced by the former ones. However, they weremostly derived from non-renewable resources, highly expensive with low stability. Recently, heterogeneouscatalysts derived from biological waste have gotten more attention. This type of catalysts offers severaladvantages, including renewable resources, non-toxic, reusable, high catalytic activity, stability in both acidicand basic conditions and high water tolerance properties, which depend on the amount and strengths of activeacid or basic sites. Basic catalyst can be subdivided based on the type of metal oxides and their derivatives.Similarly, acidic catalyst can be subdivided depending upon their active acidic sites. In this article, efforts havebeen taken to review the bio-based heterogeneous catalyst utilized for sustainable biodiesel production and theirsuitability for industrial application. Catalyst generated from bio-waste and other biocatalysts, which areheterogeneous in nature and extensively reported in literature are also reviewed. The utilization of thesebiomass derived catalysts provides a greener synthesis route for biodiesel production.

1. Introduction

Nowadays, biofuel such as biodiesel and bioethanol has become agreat interest to be the alternative source of energy as opposed to theconventional fossil fuel. The detrimental effect of global warming,rising numbers of environmental related problems, depletion of fossilfuel resources become the main factors that contribute to the globaltransformation in the development of biodiesel [1–4]. The used ofbiodiesel as a source of fuel offers several advantages, includingrenewable and sustainable resources, non-toxic, environmentalfriendly where it reduces the emission of CO2, and hazardous com-pound namely arithmetic, sulfur, particulate matter and NOx [1–5].The application of biodiesel showed a reduction in the net carbondioxide emissions on a life cycle basis, carbon monoxide, particulate

matter and unburned hydrocarbons by 78, 46.7, 66.7 and 45.2%,respectively [6]. Hence, the use of biodiesel will significantly reduce theeffect of global warming. On top of that, biodiesel can be directly usedin the engine or with little modification, blended with regular petro-leum-based diesel at any ratio without losing the engine performance[2]. In addition, no sulfur content in biodiesel provides greater lubricitythan conventional diesel fuel, thus improves the durability of theengine [7]. Generally, biodiesel displays good oil qualities, includinghigher cetane number, higher combustion efficiency, and less emission[8–10].

Biodiesel or chemically known as fatty acid methyl ester (FAME)can be derived from the chemical reaction of feedstock either vegetableoils or animal fats and alcohol with or without the presence of acatalyst. Several types of oil have been studied for the biodiesel

http://dx.doi.org/10.1016/j.rser.2016.12.008Received 4 September 2015; Received in revised form 29 July 2016; Accepted 3 December 2016

⁎ Corresponding author at: East Coast Environmental Research Institute, Universiti Sultan Zainal Abidin, Gong Badak Campus, 21300 Kuala Terengganu, Terengganu, Malaysia.E-mail addresses: shanisyasmin@yahoo.com (S.H.Y.S. Abdullah), nhanismh@gmail.com (N.H.M. Hanapi), azmanazid@unisza.edu.my (A. Azid),

roslan@unisza.edu.my (R. Umar), hafizanjuahir@unisza.edu.my (H. Juahir), hlnkhatoon@gmail.com (H. Khatoon), enazizah@unisza.edu.my (A. Endut).

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1364-0321/ © 2016 Elsevier Ltd. All rights reserved.

Please cite this article as: Sayid Abdullah, S.H.Y., Renewable and Sustainable Energy Reviews (2016),http://dx.doi.org/10.1016/j.rser.2016.12.008

production, including the first generation fuels which can be categor-ized as edible oil including palm oil [11,12], sunflower oil [13,14] andsoybean oil [15,16]. The second generation fuels component of thenon-edible oil including Jatropha curcas seed oil [17,18], neem oil[19,20], castor oil [21] and waste cooking oil [22,23]. Lastly, the thirdgeneration fuel comprises of microalgae-based oil [24–26]. Apart fromoil, biodiesel can also be derived from spending bleaching clay, a wastefrom an edible oil refinery process [27].

At the present time, there are several methods for producingbiodiesel, including direct use and blending of raw oils, dilution,microemulsion, thermal cracking or pyrolysis and transesterification[28]. Among all, transesterification is the easiest and most cost effectiveapproach to produce biodiesel [29–31]. Transesterification or alcoho-lysis can be defined as a reaction of fats or oils with an alcohol in thepresence of a catalyst to form fatty acid methyl ester and glycerol [32–34]. The general transesterification routes for biodiesel production areas illustrated in Fig. 1. Several types of alcohol can be used, includingmethanol, ethanol, butanol and amyl alcohol. However, methanol iswidely used since it is cheaper, short chain alcohol, quickly reacted andeasily dissolved into the reaction medium.

The catalyst for transesterification reaction can be either alkali oracid or enzyme. Table 1 summarizes the advantages and disadvantagesof each type of catalyst. The enzymatic transesterification is consideredto be the most effective method for biodiesel production [35,36].However, the cost catalyst is extremely high and the reaction rate istoo slow, hence retards broader application [1,9]. Currently, homo-geneous base catalysts have been widely chosen in industrial scale forbiodiesel production [7]. A homogeneous base catalyst such as sodiumhydroxide (NaOH) and potassium hydroxide (KOH) offer severaladvantages, including high catalytic activities [37,38], shorter reactiontime [39], modest operating conditions [1], raw materials are extre-mely cheap and abundantly available [31,32]. However, the homo-geneous base catalyst reaction is highly sensitive to the presence of freefatty acids (FFA) and water. Moreover, the formation of soaps as aresult of side reaction of neutralization and saponification will deter theseparation and purification process, produced a large volume ofwastewater and incur an additional cost of operation. This requirementmakes this catalyst environmentally unfriendly [29,31,39].

On the contrary, a homogeneous acid catalyst such as sulphuric acid(H2SO4), hydrochloric acid (HCl) and phosphoric acid (H3PO4) aresuitable for feedstock with high FFA content such as waste cooking oil,crude vegetable oils and animal fats. It significant advantages over theformer one includes the insensitivity to the presence of FFA and water,ability to catalyze both transesterification and esterification reactionsand no formation of soap by-products [6,29,31]. However, slowreaction time becomes the major factor that retards the wide applica-tion of this catalyst [32,39]. It has been reported that the conversionrate of acid-catalyzed transesterification is about 4000 times slowerthan that of base catalyst [6,31]. Apart from that, homogeneous acidcatalysts are highly acidic and corrosives in nature [31,40]. Productseparation and purification in homogeneous operation required anumber of steps, produce a large amount of wastewater and contributeto the increase in the operational cost [41]. In addition, recovery and

regeneration of homogeneous catalyst are difficult, not feasible, requiremore processing steps and extremely expensive [42].

The application of heterogeneous or solid catalyst has gainedinterest in the biodiesel production. The catalysts are neither consumednor dissolved in the reaction mixture which made it easier to beseparated from the product in the later [41]. On top of that, therecovered catalyst can be reused back in the reaction, hence reducingthe catalyst consumption and cost associated [3]. The heterogeneous-based operation offers several benefits including noncorrosive, easyseparation and longer catalyst life [31,32,39]. Numbers of catalysts areavailable in the market for basic-catalyzed reaction, which includesmetal oxide, mixed oxide and hydrotalcite [43]. On the other hand,transition metal oxide, ion exchange resin, carbon-based catalyst, andzeolites are among the catalysts available for acidic operation [44].However, the presence of three-phase system in a heterogeneoussystem will lead to diffusion problem that will inhibit the reaction[1]. Three phases of solid catalyst-alcohol-oil that is highly immisciblelimit the mass transfer efficiency, thus lowering the rate of reaction[29,45]. Moreover, Sani et al. [42] stated that mass transfer efficiency islimited within a bulky molecule hence resulted in the poor conversioninto biodiesel. Additional problems faced by solid catalyst are a lownumber of active sites, micro porosity, leaching, toxic, expensive,derived from non-renewable resources and environmentally unfriendly[40,46,47]. Hence, in order to produce an excellent solid acid catalyst,the catalyst must comprise of more specific surface area (hydrophobi-city, external catalytic sites, etc.) and a large pore diameter [45].

Bio-based or ‘green’ catalyst is a term referring to a type of catalystderived from natural sources such as biomass. The current trend showsthat application of the natural biological source of calcium and carbonbecomes a potential heterogeneous catalyst for transesterification ofvegetable oil. This application is a promising method since it canproduce a highly efficient bio-based heterogeneous catalyst. The solidcatalysts prepared from biomass presents an environmental friendlysolution since it is non-toxic, non-corrosive and eliminate the produc-tion of wastewater [40]. On top of that, it is mainly derived frombiomass that is considered as a low-cost material and abundantlyavailable [48]. Apart from that, there is no imminent disposal problemsince the catalyst itself is biodegradable [49]. The present study reviewsthe development of heterogeneous base and an acid catalyst derivedfrom biomass for biodiesel production. The source of catalyst, methodsof preparation and performance of these catalysts is presented in thisstudy. This paper aims to provide useful and informative knowledge onthe current biomass-derived heterogeneous catalyst for future devel-opment in the field of biodiesel process and production.

2. Biomass-derived heterogeneous alkali/base catalyst

2.1. Sources of catalyst

2.1.1. Waste shellThe application of solid base catalyst in biodiesel production is

advantageous since it can be easily separated and further reused backin the process. However, the extremely high price of the available

Fig. 1. General transesterification reaction scheme.

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catalyst since it requires a number of chemical reagents and multi-steppreparation procedure retards further applications of this type ofcatalyst [47]. Hence, the search for greener catalyst to replace theuse of conventional base catalyst has been reported by numerousstudies. Most of them utilized the catalyst derived from calciumcarbonate enriched organic waste such animal bones and shells [50].Upon high temperature combustion, calcium carbonate (CaCO3) will beconverted into calcium oxide (CaO), which is a highly active basecatalyst for biodiesel production [51]. Generally, CaO can be obtainedfrom calcium carbonate from limestone. However, the length and costof the synthesis route become a burden besides the impact of thenonrenewable sources of limestone [52]. Hence, a catalyst derived fromorganic waste materials has gained much attention as they are non-toxic, safe to handle and store, abundantly available, low cost and comefrom renewable sources [47]. Waste shells mainly composed of CaCO3

(96–98%) with trace amount of magnesium carbonate (MgCO3),

strontium carbonate (SrCO3), calcium phosphate, organic substanceand water [53]. Most of them have no value, no practical use andabundantly discarded by marine product manufacturers and localrestaurant into landfill [54]. The high amount of CaCO3 in waste shellsmakes it a promising source for the synthesis of CaO-derived catalyst.On top of that, the synthesis route for the biomass-derived catalyst israther simple, inexpensive and environmentally-friendly [55].Utilization of waste shells may eliminate the waste and producevalue-added byproducts. Various types of CaCO3-enriched organicwastes have been investigated as the potential catalyst for biodieselproduction, including waste shell [55–58], waste egg shell [59], wastecoral fragment [60], waste fish scale [61] and waste animal bones[47,62].

2.1.2. Biomass ashesApart from that, several studies investigated the potential of

Table 1Advantages and disadvantages of different types of catalyst for transesterification reaction.

Type of catalyst Examples Advantages Disadvantages References

HomogeneousAlkali NaOH, KOH • High catalytic activity

• Faster reaction time

• Low cost

• Favorable kinetics

• Modest operational conditions

• Low FFA requirement in thefeedstock ( < 1 wt%),

• Highly sensitive to water andFFA

• Saponification as side reaction,

• Soap formation

• High volume of wastewater

• Catalyst is non-recyclable

• Equipment corrosion

[1,31,32,39]

Acid H2SO4, HCL, HF, H3PO4, ρ-sulfonic acid • Insensitive to FFA and water content inoil

• Catalyzed simultaneous esterification andtransesterification reactions

• Avoid soap formation

• Slow reaction rate

• Long reaction time

• Equipment corrosion

• Higher reaction temperatureand pressure

• High alcohol/oil requirement

• Weak catalytic activity

• Catalyst is difficult to recycle

[1,31,32,39]

HeterogeneousAlkali CaO, MgO, SrO, mixed oxide and hydrotalcite • Non corrosive

• Environmentally benign

• Recyclable

• Fewer disposal problems

• Easy separation

• Higher selectivity

• Longer catalyst life

• Slow reaction rate compared tohomogeneous one

• Low FFA requirement in thefeedstock ( < 1 wt%)

• Highly sensitive to water andFFA

• Saponification as side reaction

• Soap formation

• High volume of wastewater

• Leaching of active catalyst sites

• Diffusion limitations,

• Complex and expensivesynthesis route

• High cost of catalyst synthesis

[1,31,32,39]

Acid ZrO, TiO, ZnO, ion-exchange resin, sulfonic modifiedmesostructured silica, sulfonated carbon-based catalyst,HPA and zeolites

• Insensitive to FFA and water content inthe oil

• Catalyzed simultaneous esterification andtransesterification reactions

• Recyclable, eco-friendly

• Non-corrosive to reactor and reactor parts

• Slow reaction rate

• Long reaction time

• Higher reaction temperatureand pressure

• High alcohol/oil requirement

• Weak catalytic activity

• Low acidic site

• Low micro porosity

• Leaching of active catalyst sites

• Diffusion limitations

• Complex and expensivesynthesis route

• High cost of catalyst synthesis

[1,31,32,39]

Enzyme Candida antarctica fraction B lipase, Rhizomucor mieheilipase

• Insensitive to FFA and water content inthe oil

• Avoid soap formation

• Non-polluting

• Easy purification

• Possible reuse

• Very slow reaction rate

• Highly expensive

• Highly sensitive to alcohol

• Denaturation of enzyme

[1,9,31]

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biomass ashes to be the catalyst for biodiesel production. Naturally,organic compound may contain high amount of carbon (C) and oxygen(O) and metal salt including potassium (K), sodium (Na), magnesium(Mg), calcium and (Ca) [48]. Upon combustion at a very hightemperature, the C and O content will abruptly reduce, leaving thealkali metal oxides such as CaO, potassium oxide (K2O) and magne-sium oxide (MgO) as the main active ingredients in the ashes [18]. Thepresence of high basic strength oxides in the ashes increased itscatalytic ability to produce biodiesel [63]. In another study by Ofori-Boateng and Lee [64] reported that, potash as the potential catalyst forbiodiesel production. In another study by Potash or potassium-bearingmaterials can be found in the form of potassium carbonate (K2CO3) orpotassium chloride (KCl), a by-product of biomass combustion.Inorganic-derived potash has proven to possess high catalytic abilityand being used as a base catalyst in biodiesel production, but theirsynthesis is rather hazardous, environmentally damaging and unsus-tainable. Thus, biomass-derived potash exhibits similar catalytic activ-ities of the previous one in addition to environmentally friendly, safeand sustainable.

2.1.3. Activated carbon supported catalystActivated carbon (AC) is a form of amorphous carbon with high

porosity nature [31]. It is mainly derived from high carbon contentcompounds such as coal, wood, and coconut shell. AC is widely beingused in pollution control applications including air and gas filtersystem, wastewater treatment, removal of toxic compounds such asorganic pollutants, heavy metals, and organic dyes as well as a catalystsupport [65]. AC provides higher surface area through the existence ofhigh numbers of pores where active metal particles can be anchored[29]. The utilization of catalyst support in a heterogeneous reactionmay reduce the mass transfer limitation hence increased the rate ofreaction [66]. The commercially available catalyst supports such asalumina and silica is highly expensive thus retard wider use. Thus, theuse of low-cost AC as support for biodiesel production will reduce theoverall cost of production [67]. Several studies investigated thepotential of biomass-derived activated AC as catalyst support byimpregnating with certain active metals to improve its catalyticperformance. Previously, Vadery et al. [18] stated that chemicaltreatment with a K or CA containing compound has significantlyincreased the catalytic ability of AC catalyst. A high number of activesites in AC indicated by surface porosity provide sufficient adsorptivesites for reaction to take place [68]. In another study by Chakrabortyet al. [59] concluded that high amount of SiO2 and Al2O3 of fly ashprovides a good low-cost catalyst support as opposed to the conven-tional one. Hence, the overall performance for biodiesel production wassignificantly increased. Quite a few biomass ashes have been studied intheir potential as a solid base catalyst including cocoa pod husk ash[64], coconut husk ash [18] and empty palm bunch ash [68]. Table 2summarizes the wide variety of solid base catalyst has been studied forbiodiesel production.

2.2. Catalyst preparation

Calcination is the most common method utilized for the prepara-tion of biomass-derived solid base catalyst. Calcination involvedthermal treatment in the absence of air and oxygen in order to breakdown or decompose a compound into a smaller component. Generally,calcination can be carried out at a wide range of temperature rangingfrom 300 to 1000 °C depending on the type of feedstock. Uponcombustion, CaCO3 in the organic compound will break down intoCaO and releases CO2 gas. Fig. 2 illustrates the general procedure forpreparation of CaO-derived catalyst from waste shells.

The calcination temperature plays a significant role in the forma-tion of CaO as well as development of the surface morphology of thecatalyst. Since most waste shells are most likely non-porous material,size of developed particles on the catalyst surface reflect the total

surface area of a prepared catalyst. Hence, the catalytic activity of aprepared catalyst is highly dependent on the calcination temperaturethat determined the intensity of active sites. In a study by Smith et al.[47] investigated the effect of different calcination temperature ofbovine bone waste. It was found that, no significant changes and nopositive effect on FAME yield were observed for calcined sample in therange of 350–550 °C. This suggests that, the utilized temperature doesnot have sufficient energy for the conversion of CaCO3 into CaO. Theincrement in the calcination temperature from 650 to 950 °C con-firmed the presence of CaO in the calcined bone sample. Highest FAMEyield was obtained using catalyst calcined at the temperature of 750 °C.On top of that, the formation of CaO created additional void on thecatalyst surface that simultaneously increase the total pore volume andpore diameter of the prepared catalyst. Following that, higher catalyticactivity was observed. However, further increment in the calcinationtemperature exceeding 950 °C showed a drastic reduction in thecatalyst activity due to low pore volume and presence of micro poresthat could relatively reduce the quantity of accessible active site on thecatalyst surface. In another study by Boro et al. [55] found thatcalcination temperature does affect the surface morphology of thecalcined sample. At a lower calcination temperature of 600 °C, thecatalyst surface was observed to have non-uniform and aggregatedarrangement as a result of amalgamation of the various elementalcomponents including Ca, Na, Mg, Si and Sc. The total pore volume didnot show any significant change meaning that there were additionalpores present on the catalyst surface. On the other hand, at highertemperature of 700–900 °C, Ca becomes the major compound in thecalcined sample along with the appearance of particles with varioussizes and shapes. The higher surface area was observed with a higherdegree of calcination due to the formation of crystal growth of CaO inthe calcined sample. Moreover, development of surface porosityindicated by the increase in the pore volume in the calcined shell wasattributed to the evolution of gaseous carbonization product as well asCaO formation. In addition, the calcination holding time also givessignificant effect on the CaO development. The short holding time maybe a great disadvantage since the CaO might be underdeveloped thusaffecting the catalytic activity. Longer calcination time is required toensure complete conversion of CaCO3. However, the prolonged calci-nation process caused sintering effect to the particles that lead toshrinkage of the catalyst grains. Hence, a reduction in the total effectivesurface area resulted in significant in the catalytic activity [60].

The preparation of supported solid base catalyst can be carried outthrough a tri - step procedure of calcination-wet impregnation-activa-tion as shown in Fig. 3. Calcination can be conducted at a specifictemperature depending on the type of feedstock. Wet impregnation is achemical treatment in which various types of active metal precursormix with the calcined sample in an aqueous or organic solution in orderto produce supported catalyst. High basic strength metal salts andoxides, including NaOH, KOH and CaO are being commonly used inwet impregnation. Upon impregnation, the metal salt will tend todiffuse in the porous structure of the catalyst support. Consequently,the impregnated calcined sample will be subjected to thermal activa-tion to remove moisture and volatile matter as well as aid in depositingthe metal salt on the catalyst surface. The catalytic activity of supportedcatalyst is higher than that of unsupported one due to enhancement intheir basic strength.

2.3. Biodiesel production

2.3.1. Waste shellWaste shells are the widely investigated as heterogeneous base

catalyst for biodiesel production. Previously, Boey et al. [70] studiedthe use of the waste cockle shell of Anadara granosa in biodieselproduction from palm olein oil. The waste shell was calcined at 900 °Cfor 2 h to produce an active catalyst that mainly composed of 71% ofCa. Further utilization in the transesterification process resulted in

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97.48% of FAME yield within 3 h reaction time. The spent catalyst canbe reused three cycles upon treatment with methanol and hexanefollowed by re-calcination at 900 °C for 2 h. In another study by Boroet al. [69], the waste shell of Turbonilla striatula was found to be apromising catalyst for biodiesel production using mustard oil. Effect ofdifferent calcination temperature was studied (600–900 °C) and tem-perature of 700 °C was found to be the most optimum temperaturewith highest FAME yield of 93.3%. At this temperature, presence of

particles with various sizes and shapes were observed on the catalystsurface. The reusability study confirmed leaching of active species thatsignificantly reduce the efficiency of the catalyst. However, the spentcatalyst regained its activity upon re-calcination at 900 °C for 3 h.Suryaputra et al. [58] prepared a new heterogeneous catalyst forbiodiesel production from waste Capiz shell of Amusium cristatum.The catalyst was calcined in a furnace at 900 °C for 2 h to ensurecomplete conversion of CaCO3 into CaO. A high FAME yield of 93%was obtained with the use of 3 wt% of prepared catalyst in a 6 hreaction. After the third cycle, the activity of the catalyst was abruptlydecreased by almost 50% of the fresh one due to several factorsincluding contact of basic sites with ambient CO2 and water.

Table 2Biomass-derived solid base catalyst for biodiesel production.

Type of biomass Type of feedstock Catalyst preparation conditions Transesterification reaction FAME References

CT (°C) Ct (h) CI T (°C) t (h) CL (wt%) MTOR Y or C (%)

Waste shellWaste shell of Turbonilla striatula Mustard oil 600–900 4 – 65 3 3 9:1 93.3(Y) [69]Waste cockle shell of Anadara granosa Palm olein oil 900 2 – – 3 4.9 0.54:1 97.4(Y) [70]Waste fish scale of Labeo rohita Soybean oil 600–1000 2 – 70 5 1.01 6.27:1 97.7(Y) [72]Waste oyster shell Soybean oil 1000 4 KI 50 4 1 mmol/g 10:1 85(C) [73]Waste shell of golden apple snail Palm olein oil 800 2–4 – 60 2 10 18:1 93.2(Y) [71]Waste shell of meretrix venus Palm olein oil 800 2–4 – 60 2 10 18:1 92.3(Y) [71]Waste capiz shell of Amusium cristatum Palm oil 900 2 – 60 6 3 8:1 93.0(Y) [58]Scallop waste shell Palm oil 1000 4 – 65 3 10 9:1 95.4(C) [54]Crab shell Sunflower oil 900 2 – 60 4 3 6:1 83.1 (C) [52]

Waste coralWaste coral fragment Vegetable oil 700 0.5–1.5 – 65 2 100 15:1 98.0(Y) [60]

Waste egg shellWaste egg shell Palm olein oil 800 2–4 – 60 2 10 18:1 94.1(Y) [71]Duck eggshell Palm oil 900 4 – 60 4 20 9:1 92.9(Y) [53]Chicken eggshell Palm oil 900 4 – 60 4 20 9:1 94.4(Y) [53]Eggshell Sunflower oil 900 2 – 60 3 3 9:1 97.8 (C) [52]

Animal bonesBovine bone waste Soybean oil 350–1000 6 – 65 3 8 6:1 97.0(Y) [47]

Biomass ashesMusa balbisiana Colla ash T. peruvinia seed oil – 0.5 – 32 3 20 20:1 96.0(C) [74]Tars and alkali ashes Sunflower oil 600–800 4 – – 12 – – 75.0(C) [48]Coconut husk ash Jatropha oil 250–500 1 – 45 0.5 7 12:1 90.0(Y) [18]

Activated carbon supported catalystFly ash/CaO-derived eggshell Soybean oil 1000 2 CaO 70 5 1 9:1 96.9 (Y) [59]Cocoa pod husk ash/MgO Soybean oil 650 4 MgO 40 0.5 7 6:1 98.7 (Y) [64]Empty palm bunch ash Waste cooking oil – – KOH 60 2 17.3 5:1 – [68]

CT=Calcination temperature, Ct=Calcination holding time, CI=Chemical impregnation, T=Reaction temperature, t=Reaction time, CL=Catalyst load, MTOR=methanol-to-oil molarratio.

Fig. 2. General flowchart for the preparation of CaO-derived catalyst.

Fig. 3. General flowchart for the preparation of supported catalyst.

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Furthermore, the number of active sites decreased caused by sidereactions with FFA and leaching of CaO into polar solvent. Anothersource of CaO-derived catalyst, the waste scallop shell was investigatedby Buasri et al. [54] for biodiesel production from palm oil. Prior totransesterification reaction, scallop shell undergoes calcination at1000 °C for 2 h that resulted in the formation of smaller size of thegrains and aggregates on the catalyst surface. This condition led to anincrement in the specific surface area of the catalyst and simulta-neously improves its catalytic activity. The resultant catalyst was able toyield 95.44% of FAME within 3 h reaction time.

On the other hand, Correia et al. [52] evaluated the performance oftwo different types of waste shells in the transesterification of sunfloweroil. Eggshell and crab shell were calcined at 900 °C for 2 h todecompose organic matter and complete conversion into CaO. Theuse of eggshell resulted in 97.75% of FAME yield under reactionconditions of 3 wt% catalyst load, methanol-to-oil ratio of 9:1 and 3 hreaction time. On the other hand, crab shell showed FAME yield of83.1% under reaction conditions of 3 wt% catalyst load, methanol-to-oil ratio of 6:1 and 4 h reaction time. Eggshell showed better catalyticactivity than that of crab shell owing to the higher surface content of Caas a result of homogeneously distributed and well-develop pores duringcalcination process. A similar study was conducted by Viriya-empirikulet al. [71] that compared the performance of three types of waste shellson the biodiesel production from palm olein oil. Waste shells of egg,golden apple snail, and meretrix venus were transformed into CaOthrough calcination at 800 °C for 0.5–8 h before subjected to transes-terification reaction. After 1 h reaction, the yield of biodiesel usingwaste shells of egg, golden apple snail, and meretrix venus were 93, 86and 74% respectively. Eggshell showed excellent ability as a catalystcompared to others due to the formation of the smallest particles ofvarious shapes and size that provide highest surface area for thereaction. Nevertheless, all catalysts provides FAME greater than 90% atreaction time of 2 h. The authors also studied the effect of variouscalcination time on the calcined sample. From the observation,prolonged calcination time gave sintering effect on the catalyst particleand shrinkage to the grains that might lower the surface area. Hence,the catalytic activity was drastically reduced and reducing the yield ofbiodiesel. The optimal calcination holding time was found to be at 2–4 h.

Buasri et al. [53] compared the performance of chicken and duckeggshell as the source of catalyst for biodiesel production. The catalystswere prepared by calcination at 900 °C for 4 h before being used in thetransesterification reaction. Upon calcination, formation of particleswith irregular shapes and various sizes on the catalyst surface providehigh specific active site for reaction. However, higher surface area andpore volume in were observed in chicken eggshell represented by BETsurface area and pore volume value of 136.10 m2/g and 0.12 cm3/grespectively. At reaction conditions of 20 wt% catalyst loading andmethanol-to-oil ratio of 9:1, biodiesel yield of 94.49% and 92.92% wereobtained using chicken and duck eggshells respectively. Reusabilitystudy that was carried out showed that the spent catalyst displayedexceptional catalytic activity of ( > 80%) up to four treatment cycles.The decrease in the activity is mainly due to leaching of active sitesattributed to the bond breaking and formation of Ca2+ and CH3O

−.Apart from waste shells, several studies investigated the potential of

other CaCO3−enriched wastes, including the waste coral fragment,waste fish scale, and waste animal bones. Waste coral showed excellentability with a FAME yield of 98% when used for transesterification ofwaste cooking oil. The high porosity nature of the prepared catalyst wasobserved after calcination at 700 °C for 1 h that improves the numberof active sites available for catalytic reaction [60]. In another study byChakraborty et al. [61] demonstrated the application of waste fish scalefor biodiesel production from soybean oil. The waste fish scale wascalcined 900 °C for 2 h prior to transesterification reaction to converthydroxyapatite into tri-calcium phosphate, which is the main activecompound that catalyzed the reaction. A maximum FAME yield of

97.73% was obtained under 5 h of reaction time. In another study, theapplication of fish bone supported with copper was studied as solid acidcatalyst for biodiesel production. The impregnation of copper signifi-cantly improved the catalyst performance with a maximum oleic acidconversion of 91.86% [72]. In addition, Smith et al. [47] investigatedthe potential of bovine bone waste as the catalyst for biodieselproduction. Bovine bone composed mainly of crystalline calciumcarbonate and hydroxyapatite. Calcination at 650–950 °C for 6 hresulted in the conversion of carbonate into CaO. Bovine bone-derivedcatalyst demonstrated excellent catalytic activity with a FAME yield of97% in 3 h reaction time. The authors suggested on doubling theamount of catalyst loading to maintain effectiveness of spent catalystup to six consecutive runs. Regeneration might not be a cost and energyeffective option considering the low cost and ease of catalyst prepara-tion.

In another study by Jairam et al. [73], the applicability of KI-impregnated oyster shell as catalyst for biodiesel production wasinvestigated. The catalyst was prepared through calcination at1000 °C for 4 h, followed by impregnation with KI and re-calcinationat 300 °C for 2 h. Impregnation improves the surface chemistry of thecatalyst by formation of thick layers of KI and increment in the surfacearea from 1.8 to 6 m2/g (31-fold of untreated catalyst). Further use inthe transesterification of soybean oil resulted in 85% conversion intoFAME using 1 mmol/g of catalyst loading for 4 h reaction time.

2.3.2. Biomass ashesDeka and Basumatary [74] investigated the potential of banana

trunk ash as a solid base catalyst for transesterification of T. peruviniaseed oil. Banana trunk of the family of Musa balbisiana Colla wasignited and burned to produce ash. Major components presented in theash including K, Na, CO3, Cl, and traces amount of some other metalssuch as Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb. Further use in thetransesterification reaction resulted in 96% conversion of biodiesel atroom temperature in 3 h. The biodiesel produced from this processpresented sulfur-free product with a high cetane number. In anotherstudy, Luque et al. [48] reported the use of tars and alkali ashes ascatalyst for biodiesel production. Tars and alkali ashes are the by-products of syngas production that become a major disposal problem.It is mainly composed of C, O, Si and smaller quantity of metalsincluding Na, Mg, K, Ca, S and P. The catalyst was prepared throughcalcination at 500 −800 °C for 4 h. Upon calcination, significant massloss was observed due to removal or carbonaceous and volatile matterwithin the catalyst. Hence, metal oxides become the main activeingredient in the catalyst with 36 wt% composition of Ca. The preparedcatalyst presented moderate catalytic activity with the production of75% biodiesel conversion in 12 h reaction. Meanwhile, Vadery et al.[18] investigated the potential of coconut husk as the catalyst forbiodiesel production from Jatropha seed oil. The catalyst was preparedthrough calcination at 250–500 °C for 1 h. Upon combustion, carbonand oxygen content were rapidly reduced, leaving K species, includingKCl, K2Si2O5, and K2SO4 as the main components in the ash. Furtheruse of coconut husk ash as a catalyst transesterification reactionresulted in 97% of FAME yield within 30 min reaction. The preparedcatalyst showed excellent performance ( > 95%) even at room tempera-ture and lower methanol-to-oil ratio. However, reusability studyindicated that spent catalyst loss their activity due to excessive leachingof active components thus prevent from repeated use.

2.3.3. Activated carbon supported catalystPreviously, Chakraborty et al. [59] utilized fly ash, a coal combus-

tion waste as CaO- supported catalyst for biodiesel production fromsoybean oil. Fly ash is mainly composed of a mixture of metal oxidewith high amount of SiO2 and Al2O3 which make it possible to be usedas catalyst supports. In this study, the catalyst was calcined at 1000 °Cfor 2 h prior to wet impregnation with 30 wt% of CaO derived from theeggshell. Then, the catalyst was activated at 1000 °C for 2 h. The

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6

performance of fly ash-derived catalyst was confirmed with high FAMEyield of 96.97% under the following reaction conditions; catalystloading of 1 wt% and methanol-to-oil ratio of 6.9:1. This catalystshowed superior catalytic activity compared to the unsupported CaOcatalyst judging from the increase in the BET surface area up to 89.73%than that of unsupported ones. In addition, high potential of reusabilityup to 16 runs makes supported fly ash-derived catalyst a cost-effectiveand sustainable option. In another study, the application of tars andalkali ashes were investigated for biodiesel production. Anotherpotential source of AC supported catalyst is a cocoa pod husk wasthoroughly investigated by Ofori-Boateng and Lee [64]. The cocoa podhusk was calcined at 650 °C for 4 h in order to produce potash (K2CO3),which the main active compound to catalyze the reaction. Theperformance of unsupported and MgO-supported potash catalyst wasinvestigated in the transesterification of soybean oil. The biodiesel yieldusing MgO-supported and unsupported potash were 98.7% and 91.4%respectively. High FAME yield using MgO-supported catalyst wasmainly due to the higher specific surface area of (1021.8 m2/g) thanunsupported catalyst (987.2 m2/g) that increased the availability ofactive sites on the surface of the catalyst. The application of empty fruitbunch ash as AC supported catalyst was reported by Riadi et al. [68].1.5 wt% of KOH were wet impregnated into empty fruit bunch toimprove its catalytic ability. The KOH-loaded catalyst showed excellentperformance with the production of short chain FAME and long chainFAME of 85.772 mg/L and 655.286 mg/L respectively.

3. Biomass-derived heterogeneous acid catalyst

3.1. Source of catalyst

Recently, the application of biomass-derived solid acid catalyst hascaught the world's interest. It was first introduced by Toda et al. [75] inthe esterification of oleic and stearic acid into FAME by using a catalystprepared from sulfonation of incompletely carbonized carbon material.This sulfonated carbon-based catalyst (SCBC) shows a promisingpotential since it is stable, safer, renewable, inexpensive and simplersynthesis routes. Kastner et al. [76] stated that the most distinctivefeatures of SCBC when compared to the conventional solid acid catalystbearing single functional group, is the presence of three acid sites,namely weak carboxylic acid (-COOH), medium phenolic acid (−OH)and strong sulfonic acid (−SO3H). Even though, −SO3H is the mainactive acid site for catalytic reaction, both -COOH and -OH willimprove the hydrophilic properties of catalyst surface thus providemore access for reactants [77]. On top of that, SCBC has a greaterresistance towards H2O deactivation during an esterification reaction,allowing them to maintain their activity during the reaction [78].Generally, SCBC can be derived from a number of carbon-enrichedsources that will be further discussed in this section. Table 3 sum-marizes the type of biomass used as the solid acid catalyst for biodieselproduction.

3.1.1. Refined carbohydrateThe earliest study conducted on sulfonated carbon-based catalyst

utilized the use of refined carbohydrate as the precursor carbon for theprepared catalyst. Carbohydrate is a biological molecule that is mainlyconsists of carbon, hydrogen, and oxygen. High carbon content in thecarbohydrate makes it a promising source as a carbon precursor forSCBC. Various types of refined carbohydrate were extensively studied,including simple carbohydrate; glucose [41] complex carbohydrate;starch [79] and dietary fiber carbohydrate; cellulose [80]. The applica-tion of refined carbohydrate as solid acid catalyst showed a greatpotential, however, pre-processing is required to extract and separaterefined carbohydrate from biomass prior to transesterification process.This may incur additional cost for the biodiesel production.

3.1.2. Biomass residueBiomass residue or waste biomass is a waste produce as a result of

the oil extraction process from oil-bearing plant parts which mainlyconsists of large organic hydrocarbon compound. The residue presentsan environmental problem and need for a proper treatment anddisposal that may incur additional cost to a facility. Hence, to avoidthis, a study on the potential of re-utilization of waste biomass as solidacid catalyst in biodiesel production has been conducted. A number ofpotential biomass was studied including vegetable oil asphalt [46,82]and C.inophyllum seed cake [83] and microalgae residue [84]. Thebiodiesel production using biomass residue may be a great option sinceit is low cost, readily available and environmentally friendly [82]. Fuet al. [84] stated that the utilization of biomass residue as the precursorcarbon for solid acid catalyst is advantageous as it is a cheap materialand usually discarded as waste. In another study by Silva et al. [85]stated that apart from being low cost material, the uses of biomassresidue as catalyst allows changing on the surface chemical propertiesin the appropriate manner. On top of that, the alternative uses ofbiomass residue may reduce the volume of waste generated as well as areduction in the cost associated with a proper and hygienic wastedisposal [82].

3.1.3. BiocharBiochar can be defined biomass-derived char, a carbonaceous

compound that mainly consists of 60–90% carbon with a highly porousstructure [86]. Biochar can be obtained as a by-product of pyrolysisprocess, a process where biomass is directly converted into liquid, charand condensable gases at high temperature condition in the absence ofoxygen. Upon pyrolysis, biomass components (lignin, cellulose, andhemicelluloses) will undergo a series of thermal reactions and mole-cular arrangement to form a polymerized aromatic structure. Thepresence of highly cross-linked and multi-ringed aromatic structure ofbiochar makes it possible to be functioned with active compounds.Biochar is widely applied to increase soil fertility in the plantation area[87]. The nature of biochar that is highly porous with high surface areawill improve the soil characteristic thus promote the plant's growth.Recently, the application of biochar as a catalyst has been widelydiscussed, including utilization of biochar in the decomposition ofsyngas [88], conversion of syngas into liquid hydrocarbon [89],hydrolysis of hemicellulose [90] and biodiesel production [76]. Thecatalytic activity of biochar derived catalyst is highly correlated to itsporosity, surface area, and mineral content. The wide applications ofbiochar derived catalyst provide a value-added product to the existingwaste and residue from industrial processing.

3.1.4. Activated carbonGenerally, AC can be obtained from thermal decomposition of high

carbon content compounds such as coal, wood and coconut shells.Upon heat treatment, water will be removed through vaporization andlead to carbonization that converts all organic materials into elementalcarbon. As a result, a highly disorganized form of carbon with a widerange of pore sizes, cracks and crevices is obtained [31]. The highporosity nature of AC makes it a promising choice as a carbonprecursor for sulfonated carbon-based catalyst. Sulfonation of AC willresult in the formation of a catalyst with catalytic performance. Apartfrom that sulfonated-AC catalyst offers several advantages includinglow cost, high surface area, high heat resistance and stability in bothacidic and basic environments. The utilization of sulfonated-ACcatalyst in biodiesel production have been widely investigated usingdifferent raw materials such as peanut hulls [76], corn straw [91],Xanthoceras sorbifolia Bunge hulls [92], oil palm trunks and sugar-cane bagasse [6].

3.2. Catalyst preparation

SCBC is prepared through incomplete carbonization of precursor

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7

Table

3Biomass-derived

solidacid

catalyst

forbiod

ieselproduction.

Typ

eof

biom

ass

Typ

eof

feed

stock

Catalystpreparationconditions

Transesterificationreaction

FAME

Referen

ces

CT(°C)

Ct(h)

SAST

(°C)

St(h)

T(°C)

t(h)

CL(w

t%)

MTOR

Yor

C(%

)

Refi

ned

carboh

ydrates

D-glu

cose

Oleic

andstearicacid

400

15Con

c.H

2SO

4(>96

%)

5015

801

0.2g

–44

µmol/m

in[41]

D-glu

cose

Oleic

andstearicacid

400

15Fum.SO

3(15wt%

)50

1580

10.2g

–86

µmol/m

in[41]

Starc

hWaste

cook

ingoil

400

–Con

c.H

2SO

4(>96

%)

≥10

0–

803

1020

:195

(Y)

97Cellulose

Waste

cook

ingoil

400

–Con

c.H

2SO

4(>96

%)

≥10

0–

803

1020

:188

(Y)

[97]

Sucr

ose

Waste

cook

ingoil

400

–Con

c.H

2SO

4(>96

%)

≥10

0–

803

1020

:180

(Y)

[97]

Glu

cose

Waste

cook

ingoil

400

–Con

c.H

2SO

4(>96

%)

≥10

0–

803

1020

:176

(Y)

[97]

D-glu

cose

-starc

hm

ixtu

reOleic

acid

400

1–1.5

Con

c.H

2SO

4(>98

%)

150–

160

560

–80

125

10:1

96(Y)

[76]

D-glu

cose

-starc

hm

ixtu

reTriolein

400

1–1.5

Con

c.H

2SO

4(>98

%)

150–

160

580

125

30:1

60(Y)

[76]

D-glu

cose

-starc

hm

ixtu

reWaste

cotton

seed

oil

400

1–1.5

Con

c.H

2SO

4(>98

%)

150–

160

580

125

20:1

90(Y)

[76]

D-glu

cose

C.inop

hyllum

seed

oil

400

5Con

c.H

2SO

415

010

180

45

15:1

51.4

(C)

[75]

Micro

crys

tallin

ece

llulose

C.inop

hyllum

seed

oil

400

5Con

c.H

2SO

415

010

180

45

15:1

99(C

)[75]

Biomassresidue

Vegetable

oil

asp

halt

Cottonseed

oil

500–

700

–Con

c.H

2SO

4(>98

%)

120

426

03

0.2

18.2:1

89.93(C

)[46]

Vegetable

oil

asp

halt

Waste

vegetableoil

500–

700

2°C

/min

Con

c.H

2SO

4(>98

%)

210

1022

04.5

0.2

16.8:1

80.5(C

)[82]

Vegetable

oil

asp

halt

Waste

vegetableoil

500–

700

2°C

/min

Con

c.H

2SO

4(>98

%)

210

1014

03

0.3

–80

(C)

[101

]Petroleum

asp

halt

Waste

vegetableoil

500–

700

2°C

/min

Con

c.H

2SO

4(>98

%)

210

1014

03

0.3

–50

(C)

[101

]C.inophyllum

seedca

kere

sidue

C.inop

hyllum

seed

oil

400

5Con

c.H

2SO

415

010

150

50.3g

5.5g

36.4

(C)

[83]

C.inophyllum

seedca

kere

sidue

C.inop

hyllum

seed

oil

400

5PTSA

150

1015

05

0.3g

5.5g

14.2

(C)

[83]

Bioch

arPyr

olyze

dharw

oodch

ar

Can

olaoil

––

Con

c.H

2SO

4(>98

%)

150

2465

35

18:1

89[7]

Pyr

olyze

dharw

oodch

ar

Can

olaoil

––

Fum.SO

3(15wt%

)15

05,

1565

35

18:1

92[7]

Peanuthull,pin

eandwoodbioch

ar

Soyb

eanoil

400–

600

1Con

c.H

2SO

4(>98

%)

100,

150,

200

1257

–59

64–

7.5

20:1

70(C

)[76]

Woodybiom

ass

char

Can

olaoilan

doleicacid

mixture

675

2Fum.SO

3(>20

wt%

)15

015

150

35

10:30

48(Y)

[102

]Ricehusk

char

Waste

cook

ingoil

510

480°C

/s(4

s)Con

c.H

2SO

4(95–98

wt%

)90

0.5

110

155

20:1

87.57(Y)

[103

]

Activated

carbon

Peanuthull

Soyb

eanoil

––

Con

c.H

2SO

4(>98

%)

100,

150,

200

1257

–59

64–

7.5

10:1

97(C

)[76]

Peanuthull

Soyb

eanoil

––

Fum.SO

3(15wt%

)23

6days

57–59

34–

7.5

6:1

>94

(C)

[76]

Xanth

oce

rasso

rbifoliahull

Acidifiedsoyb

eansoap

stock

400

1Con

c.H

2SO

4(98%

)15

02

705

791

97(C

)[92]

Corn

stra

wOleic

acid

300

1Fum.SO

3(30wt%

)80

460

47

7:1

98(Y)

[91]

Oil

palm

trunk

Palm

olein

400

8Con

c.H

2SO

4(95–97

%)

150

1565

0.75

2Pseudoinfinite

93(Y)

[6]

Sugarc

anebagass

ePalm

olein

400

8Con

c.H

2SO

4(95–97

%)

150

1565

0.75

2Pseudoinfinite

94(Y)

[6]

Sugarc

anebagass

eWaste

cook

ingoil

400–

800

5Con

c.H

2SO

4(98%

)12

0–20

05–15

665

118

:194

(C)

[104

]Sugarbeetpulp

Palm

fattyacid

distillate

400

2Con

c.H

2SO

4(98%

)30

06

855

3g

5:1

92(Y)

[105

]

CT=Carbo

nizationtemperature,C

t=Carbo

nizationholdingtime,SA

=Su

lfon

atingag

ent,ST

=Su

lfon

ationtemperature,S

t=Su

lfon

ationholdingtime,T=Reactiontemperature,t=Reactiontime,CL=Catalystload

,MTOR=methan

ol-to-oilm

olar

ratio.

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8

carbon followed by sulfonation with various types of sulfonating agentas shown in Fig. 4. To this extent, pyrolysis and hydrothermalcarbonization are the widely used carbonization method to prepare acarbon-based catalyst. Pyrolysis is often carried out at a temperature inthe range of 200–700 °C under nitrogen flow or argon atmosphere. Thepreparation variables, including carbonization temperature, carboniza-tion time and sulfonation temperature greatly influenced the texturalproperties of the prepared catalyst. The high temperature will result inthe formation of rigid carbon structure which hindered the anchoringof sulfonic (−SO3H) groups, thus reduced the density of active acidsites on the prepared catalyst [77]. On the other hand, synthesis ofcarbon catalyst at a lower pyrolysis temperature (400–500 °C) willresult in the generation of soft aggregated, cross-linked polymer that issusceptible to being sulfonated at the highest degree [76]. Further useof the catalyst showed highest esterification activity. In a study by Shuet al. [81], SCBC that was carbonized at lower temperature (650 °C)showed excellent performance on the conversion of cottonseed oil andFFA compared to those with high carbonization temperature (950 °C).This is attributable to higher acid site concentration and larger porediameter in the prepared catalyst at a lower carbonization temperature.On top of that, Lou et al. [92] stated that formation of water layer wasobserved on the surface of catalyst at a lower carbonization tempera-ture that will prevent access to hydrophobic materials including FFA.On the other hand, hydrothermal carbonization can be defined aspressurized thermal conversion conducted at a lower temperature(150–350 °C) with the presence of water [93,94]. Hydrothermalcarbonization produces a carbonaceous residue called hydrochar whichmainly consist of 45–75% carbon content [95]. Utilization of SCBCprepared from hydrothermal carbonization showed excellence catalyticactivities comparable to homogeneous H2SO4 process [96]. Deshmaneet al. [97] reported that SCBC synthesis using hydrothermal carboniza-tion presented low evidence in the leaching of colloidal carbon.

Sulfonation is a process where precursor carbon is functionalizedwith active sulfonic acid (−SO3H) group. It was found to be an effectivecatalyst for esterification and transesterification reaction [98].Sulfonation will result in the increased in the total acid density ofSCBC by formation of −SO3H groups and additional weak carboxylic(−COOH) and phenolic (−OH) groups [76]. Total acid density andparticularly sulfonic acid density are the crucial factors in the determi-nation of catalytic activity. Concentrated and fuming H2SO4 are widelyused as sulfonating agent in the preparation of SCBC due to availabilityand cheaper prices [99]. Fuming H2SO4 showed superior activity thanthat of concentrated H2SO4 indicated by the higher value of total acid

density in SCBC prepared via fuming H2SO4 [101]. Takagaki et al. [41]highlighted that higher catalytic activity in fuming H2SO4 is attribu-table to the high water consumption that promotes formation of−SO3H through the reaction of water and H2SO4 hence strongersulfonation was observed. Another study by Dawodu et al. [82]compared the performance of concentrated H2SO4 and P-toluenesul-fonic acid (PTSA) to functionalize carbon catalyst. It was found thatsulfonation using concentrated H2SO4 showed superior activity thanthat of PTSA due to higher sulfur content in concentrated H2SO4 thatleads to higher distribution of the acid density when compared to thePTSA. Apart from that, sulfonation also promotes the activation andoxidation of carbon that led to the improvement in the surface area andpore structure [97]. However, the catalytic activity of SCBC is alsodependent on the type of precursor carbon structure as previouslymentioned in a study by Kastner et al. [76]. In the study, sulfonationusing concentrated H2SO4 generated higher acid site density in biocharon the other hand sulfonation using fuming H2SO4 generated higheracid density in activated carbon.

3.3. Biodiesel production

3.3.1. Refined carbohydratePreviously, Takagaki et al. [41] prepared a solid acid catalyst from

D-glucose as the precursor carbon for the esterification of higher fattyacid mixture. The carbon sample was carbonized at lower temperatureprior to sulfonation with two types of sulfonating agents (concentratedand fuming H2SO4). Fuming H2SO4 displayed higher esterificationefficiency denoted by higher rates of FAME formation of 86 µmol/minthan only 44 µmol/min in concentrated H2SO4. In addition, the bothcatalysts showed remarkable catalytic activity in comparison to thecommercial solid acid catalysts such as Nafion (NR50), niobic acid andH-mordenite. The presence of −SO3H groups in the prepared catalystssignificantly improved the total acid density in the prepared SCBC thatcontributes to their high performance. In another study by Lou et al.[92] compared the performance of four different refined carbohydratesas solid acid catalyst for the transesterification of waste cooking oil. Therefined carbohydrate including starch, cellulose, sucrose and D-glucosewere carbonized at 300 °C followed by sulfonation with concentratedH2SO4. After 3 h reaction, the four corresponding catalysts preparedfrom starch, cellulose, sucrose and D-glucose resulted in FAME yield of95, 88, 80 and 76% respectively. Thus, the type of precursor carbonplays a big part in the determination of catalytic activity. It was foundthat higher surface area and total acid density in starch-derived catalystexplained the superior activity of the catalyst compared to others.Larger pore size and volume promotes the incorporation of the bulk oilmolecules into the active sites of the catalyst thus improves the catalyticefficiency of starch-derived catalyst. On the other hand, Chen and Fang[79] investigated the potential of glucose-starch as solid acid catalystfor biodiesel production. The glucose-starch mixture was incompletelycarbonized at 400 °C for 60–90 min and sulfonated using concentratedH2SO4 at 150–160 °C for 5 h. The result of the study indicated that theamylopectin content in starch greatly influenced the attachment of−SO3H group onto the carbon compound. Further utilization of theprepared catalyst in esterification and transesterification processesshowed a biodiesel yield of 96% and 60% respectively. Reusabilitystudy confirmed that the catalyst activity remained ≥90% up to 15cycles with regeneration of catalyst using H2SO4. The potential ofcellulose-derived catalyst for biodiesel production has been investi-gated by Ayodele and Dawodu [80]. The catalyst was prepared bycarbonization under dry N2 at 400 °C for 5 h to produce carbonaceoussolid. The resulting solid was a sulfonated using concentrated H2SO4 at150 °C for 10 h. The esterification activity of cellulose-derived catalystwas investigated using C.inophyllum oil and the results displayedsuperior performance of cellulose-derived catalyst as compared toglucose-derived catalyst with a biodiesel yield of 99 and 51.4%respectively. The high activity of cellulose-derived catalyst is due to

Fig. 4. General flowchart for the preparation of sulfonated carbon based catalyst (SCBC).

S.H.Y.S. Abdullah et al. Renewable and Sustainable Energy Reviews (xxxx) xxxx–xxxx

9

high acid density and better porous structure than that of D-glucose-derived catalyst.

3.3.2. Biomass residuePreviously, Shu et al. [46] investigated the potential of solid acid

catalyst derived from vegetable oil asphalt for biodiesel production.Vegetable oil asphalt consists mainly of hydrocarbon, a solid residue ofbiodiesel production. Vegetable oil asphalt was first carbonized at 500–700 °C at a rate of 2 °C/min under argon atmosphere. The sulfonationof carbonized product was performed using concentrated H2SO4 at120 °C for 4 h to obtain sulfonated vegetable oil asphalt. The carboni-zation process produced a carbon catalyst with loose irregular networkstructure with several micropores. Upon sulfonation, the pore sizesbecome larger due to particle agglomeration and disintegration. Thesulfonated vegetable oil asphalt catalyst displayed high catalytic activitywith 89.93% conversion of cottonseed oil into FAME. This is mainlydue to the accessibility of reactant into the active acid sites on thesurface of the catalyst, hence better activity. Comparison with sulfo-nated multiwalled carbon nanotube (s-MWCNT) showed higher per-formance of the prepared catalyst. It can be noted that surface area andporosity greatly influenced the activities. The author further investi-gated the use of vegetable oil asphalt derived catalyst for the transes-terification of waste vegetable oil [86]. The results of the study showedhigher activity of the prepared catalyst with 80.5% conversion. Thisindicated that different feedstock gives minimal impact on the catalystperformance. In another study, the activity of two different catalystsources was investigated [100]. Solid acid catalyst derived fromvegetable oil asphalt and petroleum asphalt was prepared using thesame procedures. The catalysts differ in their textural properties andsurface porosity due to the difference in their elemental compound andmolecular structure. Vegetable oil asphalt-based catalyst exhibitedsuperior activity than that of petroleum asphalt derived catalystattributable to high acid density and larger pore diameter. Higherconversion of FFA and triglyceride was observed using vegetable oilasphalt derived catalyst. Dawodu et al. [87] investigated the potentialof the seed cake residue of C. inophyllum as precursor carbon forSCBC. The catalyst was carbonized at 400 °C for 5 h to obtainincompletely carbonized compound. Sulfonation of carbon compoundwas carried out using two different sulfonating agents which areconcentrated H2SO4 and PTSA. Carbon catalyst sulfonated usingconcentrated H2SO4 exhibited high activity due to the high degree ofsulfonation compared to PTSA with FAME conversion of 36.4% and14.2% respectively.

3.3.3. BiocharA study by Dekhoda et al. [7] investigated the use hardwood char as

a catalyst for biodiesel production. The char was commerciallyobtained and sulfonated using concentrated and fuming H2SO4 at120 °C for 24 h and 15 h respectively. From the observation, sulfona-tion greatly improved the textural properties of the catalysts. However,higher total acidity, surface area, and porosity were observed in thecatalyst sulfonated with fuming H2SO4 compared to concentratedH2SO4. The transesterification capacity of both catalysts was studiedusing canola oil resulted in higher conversion of biodiesel of 89 and92% using concentrated and fuming H2SO4 respectively. Higher sur-face area and porosity in the prepared catalyst indicated that highavailability of the active site for reaction to take place. Thus, thecatalytic performance will be significantly improved. In another study,mixture of peanut hull, pine logs residue, and wood chips were used togenerate biochar [76]. The biochar was functionalized with concen-trated and fuming H2SO4 at 150 °C for 12 h to produce sulfonatedbiochar. The result of the study showed that the prepared catalyst had ahigh esterification efficiency with 70% FAME conversion. The reusa-bility study indicated that the catalyst loss its activities to half of itsoriginal conversion capacity due to strong water absorption, particleattrition and leaching of active site. In another study by Dekhoda and

Ellis [101] investigated the effect of different alcohol to oil molar ratioand alcohol to FFA molar ratio of the biodiesel yield. Biochar-derivedsolid showed high efficiency with 48% yield in 3 h reaction time. On theother hand, Li et al. [102] compared the performance of rice husk charderived catalyst with commercial catalyst Amberlyst-15 for biodieselproduction. Rice husk char was sulfonated using concentrated H2SO4

at 90 °C for 30 min to produce sulfonated char with high sulfonic aciddensity. The transesterification of waste cooking oil showed a high yieldof biodiesel using the prepared catalyst as compared to Amberlyst-15with 87.57% and 45.17% respectively.

3.3.4. Activated carbonKastner et al. [76] studied the performance of sulfonated AC from

peanut hulls for biodiesel production. The sulfonation procedure wasconducted using two different sulfonating agents which are concen-trated and fuming H2SO4. It was found that, fuming H2SO4 providehigher acid density in the sulfonated AC due to the fact that fumingH2SO4 is more reactive and selective than concentrated H2SO4. Bothcatalysts showed excellent performance with > 90% biodiesel conver-sion. The novel solid acid catalyst for biodiesel production was derivedfrom residual lignin of Xanthoceras sorbifolia Bunge hulls [90]. Thecatalyst was carbonized and sulfonated using concentrated H2SO4. Theperformance of catalyst was later investigated in the esterification ofacidified soapstock. The high performance of the prepared catalyst wasobserved with 98% of FFA conversion. The recycled catalyst loses itsactivity after fourth cycles, thus affected the FFA conversion. A study byLiu et al. [90] prepared sulfonated corn straw AC as solid acid catalystfor the esterification of oleic acid. The catalyst was heated under N2

flow, followed by sulfonation using fuming H2SO4. A high acid densitycatalyst with good dispersion and hydrophobic properties was obtainedfrom this study. The hydrophobic nature of the catalyst will preventfrom hydration thus retained its stability in the presence of water.Biodiesel production using sulfonated corn straw AC produced 98% ofFAME yield. Previously, Zhang et al. [104] evaluated the performanceof sugarcane baggase derived catalyst in biodiesel production. Thecatalyst was prepared through a series of carbonization and sulfonationprocess in order to produce highly active catalyst. The effects ofpretreatment conditions on the catalytic activity were extensivelystudied. The outcome suggested that, carbonization temperature of600 °C and a sulfonation temperature of 200 °C is the optimalcondition in production highly active solid acid catalyst from sugarcanebaggase. In another study by Babadi et al. [104] investigated thepotential of sugar beet pulp as solid acid catalyst for biodieselproduction from palm fatty acid distillate (PFAD), a major by-productin palm oil industries. The solid acid catalyst was successfully preparedby sulfonation of incompletely carbonized AC using concentratedH2SO4. The morphology study revealed a porous solid acid catalystwith high total acid density. Further use in the transesterificationreaction of PFAD and ethanol resulted in 92% FAME yield.

4. Future perspective

The utilization of biomass-derived heterogeneous catalyst forbiodiesel production seems to be a promising choice as it eliminatesthe tedious and problems faced by homogeneous operations. Theexploration of biomass or waste as the source of catalyst may reducethe associated cost for commercially available solid catalyst as well asprovide new applications for the waste. However, further investigationand development of biomass-derived catalyst are necessary to improvethe catalytic performance for biodiesel production as well as otherchemical processes.

Acknowledgement

The authors would like to acknowledge the MyBrain15 scholarshipprovided by Ministry of Higher Education, Malaysia and research

S.H.Y.S. Abdullah et al. Renewable and Sustainable Energy Reviews (xxxx) xxxx–xxxx

10

financial support from FRGS Research Grant, Project No. RR067,Project Code FRGS/1/2014/STWN01/UNISZA/02/2.

References

[1] Leung DYC, Wu X, Leung MKH. A review on biodiesel production using catalyzedtransesterification. Appl Energy 2010;87:1083–95.

[2] Ahmad AL, Mat Yasin NH, Derek CJC, Lim JK. Microalgae as a sustainable energysource for biodiesel production: a review. Renew Sustain Energy Rev2011;15:584–93.

[3] Singh B, Gulde A, Rawat I, Bux F. Towards a sustainable approach for develop-ment of biodiesel from plant and microalgae. Renew Sustain Energy Rev2014;29:216–45.

[4] Borges ME, Diaz L. Recent developments on heterogeneous catalysts for biodieselproduction by oil esterification and transesterification reactions: a review. RenewSustain Energy Rev 2012;16:2839–49.

[5] Cheirslip B, Louhasakul Y. Industrial wastes as a promising renewable source forproduction of microbial lipid and direct transesterification of the lipid intobiodiesel. Bioresour Technol 2013;142:329–37.

[6] Ezebor F, Khairuddean M, Abdullah AZ, Boey PL. Oil palm trunk and sugarcanebaggase derived solid acid catalysts for rapid esterification of fatty acids andmoisture-assisted transesterification of oils under pseudo-infinite methanol.Bioresour Technol 2014;157:254–62.

[7] Dekhoda AM, West AH, Ellis N. Biochar based solid acid catalyst for biodieselproduction. Appl Catal A Gen 2010;382:157–204.

[8] Ma F, Hanna MA. Biodiesel production: a review. Bioresour Technol1999;70:1–15.

[9] Marchetti JM, Miguel VU, Errazu AF. Possible methods for biodiesel production.Renew Sustain Energy Rev 2007;11:1300–11.

[10] Demirbas A. Progress and recent trends in biodiesel fuels. Energy Convers Manag2009;50:14–34.

[11] Taufiq-Yap YH, Lee HV, Hussein MZ, Yunus R. Calcium-based mixed oxidecatalysts for methanolysis of Jatropha curcas oil to biodiesel. Biomass Bioenergy2011;35(2):827–34.

[12] Petchamala A, Laosiripojana N, Jongsomjit B, Goto M, Panpranot J,Mekasuwandumrong O, et al. Transesterification of palm oil and esterification ofpalm fatty acid in near- and super-critical methanol with SO4-ZrO2 catalysts. Fuel2010;89:2387–92.

[13] Chopade SG, Kulkarni KS, Kulkarni AD, Topare NS. Solid heterogeneous catalystsfor production of biodiesel from transesterification of triglycerides with methanol:a review. Acta Chim Pharm Indica 2012;2(1):8–14.

[14] Stamenkovic OS, Rajkovic K, Velickovic AV, Milic PS, Veljkovic VB. Optimizationof base-catalysed ethanolysis of sunflower oil by regression and artificial neuralnetwork models. Fuel Process Technol 2013;114:101–8.

[15] Liu XY, Huang M, Ma HL, Zhang ZQ, Gao JM, Zhu YL, et al. Preparation of acarbon-based solid acid catalyst by sulfonating activated carbon in a chemicalreduction process. Molecules 2010;15:7188–96.

[16] Xu W, Gao L, Wang S, Xiao G. Biodiesel production in a membrane reactor usingMCM-41 supported solid acid catalyst. Bioresour Technol 2014;150:286–91.

[17] Taufiq-Yap YH, Abdullah NF, Basri M. Biodiesel production via transesterificationof palm oil using NaOH/Al2O3 catalysts. Sains Malays 2011;40(6):587–94.

[18] Vadery V, Narayanan BN, Ramakrishnan RM, Cherikkallinmel SK, Sugunan S,Narayanan DP, et al. Room temperature production of jatropha biodiesel overcoconut husk ash. Energy 2014;70:588–94.

[19] SathyaSelvabala V, Selvaraj DK, Kalimuthu J, Periyaraman PM, Subramaniam S.Two-step biodiesel production from Calophyllum inophyllum oil: optimization ofmodified B-zeolite catalyzed pre-treatment. Bioresour Technol2011;102:1066–72.

[20] Betiku E, Omilakin OR, Ajala SO, Okeleye AA, Taiwo AE, Solomon BO.Mathematical modeling and process parameters optimization studies by artificialneural network and response surface methodology: a case of non-edible neem(Azadirachta indica) seed oil biodiesel synthesis. Energy 2014;72:266–73.

[21] Bankovic-Ilic IB, Stamenkovic OS, Velkovic VB. Biodiesel production from non-edible plant oils. Renew Sustain Energy Rev 2012;16:3621–47.

[22] Talebian-Kalaieah A, Amin NAS, Zarei A, Jaliliannosrati H. Biodiesel productionfrom high free fatty acid waste cooking oil by solid acid catalyst. In: Proceedings ofthe 6th International Conference on Process System Engineering (PSE Asia).Kuala Lumpur; June 2013. p. 25–27.

[23] WNNW Omar, Amin , Biodiesel NAS. production from waste cooking oil overalkaline modified zirconia catalyst. Fuel Process Technol 2011;92:2397–405.

[24] Tran DT, Yeh KL, Chen CL, Chang JS. Enzymatic transesterification of microalgaloil from Chlorella vulgaris ESP-31 for biodiesel synthesis using immobilizedBurkholderia lipase. Bioresour Technol 2012;108:119–27.

[25] Teo SH, Islam A, Yusaf T, Taufiq-Yap YH. Transesterification of Nannochloropsisoculata microalga's oil to biodiesel using calcium methoxide catalyst. Energy2014;78:63–71.

[26] Galadima A, Muruza O. Biodiesel production from algae by using heterogeneouscatalyst: a critical review. Energy 2014;78:72–83.

[27] Nurfitri I, Maniam GP, Hindryawati N, Yusoff MM, Ganesan S. Potential offeedstock and catalysts from waste in biodiesel preparation: a review. EnergyConvers Manag 2013;74:395–402.

[28] Khan TMY, Atabani AE, Badruddin IA, Badarudin A, Khayoon MS, Triwahyono S.Recent scenario and technologies to utilize non-edible oils for biodiesel produc-tion. Renew Sustain Energy Rev 2014;37:840–51.

[29] Zabeti M, Daud WAW, Aroua MK. Activity of solid catalysts for biodieselproduction: a review. Fuel Process Technol 2009;90:770–7.

[30] Singh SP, Singh D. Biodiesel production through the use of different sources andcharacterization of oils and their esters as the substitute of diesel: a review. RenewSustain Energy Rev 2010;14:200–16.

[31] Konwar LJ, Boro J, Deka D. Review on latest developments in biodieselproduction using carbon-based catalysts. Renew Sustain Energy Rev2014;29:546–64.

[32] Tariq M, Ali S, Khalid N. Activity of homogeneous and heterogeneous catalysts,spectroscopic and chromatographic characterization of biodiesel: a review. RenewSustain Energy Rev 2012;16:6303–16.

[33] Kouzu M, Kasumo T, Tajika M, Sugimoto Y, Yamanaka S, Hidaka J. Calcium oxideas a solid base catalyst for transesterification of soybean oil and its application tobiodiesel production. Fuel 2008;87:2798–806.

[34] Sani YM, Daud WAW, Aziz ARA. Solid acid-catalyzed biodiesel production frommicroalgal oil-The dual advantage. J Environ Chem Eng 2013;1:113–21.

[35] Christopher LP, Kumar H, Zambare VP. Enzymatic biodiesel: challenges andopportunities. Appl Energy 2014;119:497–520.

[36] Tran DT, Chen CL, Chang JS. Effect of solvents and oil content on directtransesterification of wet oil-bearing microalgal biomass of Chlorella vulgaris ESP-31 for biodiesel synthesis using immobilized lipase as the biocatalyst. BioresourTechnol 2013;135:213–21.

[37] Semwal S, Arora AK, Badoni RP, Tuli DK. Biodiesel production using hetero-geneous catalysts. Bioresour Technol 2011;102:2151–61.

[38] Islam A, Taufiq-Yap YH, Chan ES, Moniruzzaman M, Islam S, Nabi MN. Advancesin solid-catalytic and non-catalytic technologies for biodiesel production. EnergyConvers Manag 2014;88:1200–18.

[39] Helwani Z, Othman MR, Aziz N, Kim J, Fernando WJN. Solid heterogeneouscatalysts for transesterification of triglycerides with methanol: a review. Appl CatalA Gen 2009;363:1–10.

[40] Lam MK, Lee KT, Mohamed AR. Homogeneous, heterogeneous and enzymaticcatalysis for transesterification of high free fatty acid oil (waste cooking oil) tobiodiesel: a review. Biotechnol Adv 2010;28:500–18.

[41] Takagaki A, Toda M, Okamura M, Kondo JN, Hayashi S, Domen K, et al.Esterification of higher fatty acids by a novel strong solid acid. Catal Today2006;116:157–61.

[42] Sani YM, WMAW Daud, Aziz ARA. Activity of solid acid catalyst for biodieselproduction: a critical review. Appl Catal A Gen 2014;470:140–61.

[43] Gotch AJ, Reeder AJ, McCormick A. Study of heterogeneous base catalysts forbiodiesel production. J Undgrad Chem Res 2009;8(9):22–6.

[44] Chouhan APS, Sarma AK. Modern heterogeneous catalysts for biodiesel produc-tion: a comprehensive review. Renew Sustain Energy Rev 2011;15:4378–99.

[45] Macario A, Giordano G. Catalytic conversion of renewable sources for biodieselproduction: a comparison between biocatalysts and inorganic catalysts. Catal Lett2013;143:159–68.

[46] Shu Q, Zhang Q, Xu G, Nawaz Z, Wang D, Wang J. Synthesis of biodiesel fromcottonseed oil and methanol using a carbon-based solid acid catalyst. Fuel ProcessTechnol 2009;90:1002–8.

[47] Smith SM, Oopathum C, Weeramongkhonlert V, Smith CB, Chaveanghong S,Ketwong P, et al. Transesterification of soybean oil using bovine bone waste as newcatalyst. Bioresour Technol 2013;143:686–90.

[48] Luque R, Pineda A, Colmenares JC, Campelo JM, Romero AA, Serrano-Ruiz JC,et al. Carbonaceous residues from biomass gasification as catalysts for biodieselproduction. J Nat Gas Chem 2012;21:246–50.

[49] Sanjay B. Heterogeneous catalyst derived natural resources for biodiesel produc-tion: a review. Res J Chem Sci 2013;3(6):95–101.

[50] Verziu M, Coman SM, Richards R, Parvulescu VI. Transesterification of vegetableoils over CaO catalysts. Catal Today 2011;167:64–70.

[51] Oliveira DA, Benelli P, Amante ER. A literature review on adding value to solidresidues: egg shells. J Clean Prod 2013;46:42–7.

[52] Correia LM, Saboya RMA, Campelo NdS, Cecilia JA, Rodriguez-Castellon E,Cavalcante Jr CL, et al. Characterization of calcium oxide catalysts from naturalsources and their application in the transesterification of sunflower oil. BioresourTechnol 2014;151:207–13.

[53] Buasri A, Chaiyut N, Loryuenyong V, Wongweang C, Khamsrisuk S. Application ofeggshell wastes as a heterogeneous catalyst for biodiesel production. SustainEnergy 2013;1(2):7–13.

[54] Buasri A, Worawanitchaphong P, Trongyong S, Loryuenyong V. Utilization ofscallop waste shell for biodiesel production from palm oil-Optimization usingTaguchi method. APCBEE Procedia 2014;8:216–21.

[55] Boro J, Deka D, Thakur AJ. A review on solid oxide derived from waste shells ascatalyst for biodiesel production. Renew Sustain Energy Rev 2012;16:904–10.

[56] Rezaei R, Mohadesi M, Moradi GR. Optimization of biodiesel production usingwaste mussel shell catalyst. Fuel 2013;109:534–41.

[57] Girish N, Niju SP, Begum KMMS, Anantharaman N. Utilization of a cost effectivesolid catalyst derived from natural white bivalve clam shell for transesterificationof waste frying oil. Fuel 2013;111:653–8.

[58] Suryaputra W, Winata I, Indraswati N, Ismadji S. Waste capiz (Amusiumcristatum) shell as a new heterogeneous catalyst for biodiesel production. RenewEnergy 2013;50:795–9.

[59] Chakraborty R, Bepari S, Banarjee A. Transesterification of soybean oil catalyzedby fly ash and eggshell derived solid catalysts. Chem Eng J 2010;165:798–805.

[60] Roschat W, Kacha M, Yoosuk B, Sudyoadsuk T, Promarak V. Biodiesel productionbased on heterogeneous process catalyzed by solid waste coral fragment. Fuel2012;98:194–202.

[61] Chakraborty R, Bepari S, Banerjee A. Application of calcined waste fish (Labeo

S.H.Y.S. Abdullah et al. Renewable and Sustainable Energy Reviews (xxxx) xxxx–xxxx

11

rohita) scale as low cost heterogeneous catalyst for biodiesel synthesis. BioresourTechnol 2011;102:3610–8.

[62] Farooq M, Ramli A, Naeem A. Biodiesel production from low FFA waste cookingoil using heterogeneous catalyst derived from chicken bones. Renew Energy2015;76:362–8.

[63] Chouhan APS, Sarma AK. Biodiesel production from Jatropha curcas L. oil usingLemna perpusilla Torrey ash as heterogeneous catalyst. Biomass Bioenergy2013;55:386–9.

[64] Ofori-Boateng C, Lee KT. The potential of using cocoa pod husks as green solidbase catalysts for the transesterification of soybean oil into biodiesel: effects ofbiodiesel on engine performance. Chem Eng J 2013;220:395–401.

[65] Islam MS, Rouf MA. Waste biomass as sources for activated carbon production: areview. Bangladesh J Sci Ind Res 2012;47(4):347–64.

[66] Lee AF, Bennett JA, Manayil JC, Wilson K. Heterogeneous catalysis for sustain-able biodiesel production via esterification and transesterification. Chem Soc Rev2014;34:7887–916.

[67] Hameed BH, Goh CS, Chin LH. Process optimization for methyl ester productionfrom waste cooking oil using activated carbon supported potassium fluoride. FuelProcess Technol 2009;90:1532–7.

[68] Riadi L, Purwanto E, Kurniawan H, Oktaviana R. Effect of bio-based catalyst inbiodiesel synthesis. Procedia Chem 2014;9:172–81.

[69] Boro J, Thakur AJ, Deka D. Solid oxide derived from waste shells of Turbonillastriatula as a renewable catalyst for biodiesel production. Fuel Process Technol2011;92:2061–7.

[70] Boey PL, Maniam GP, Hamid SA, Ali DMH. Utilization of waste cockle shell(Anadara granosa) in biodiesel production from palm olein: optimization usingresponse surface methodology. Fuel 2011;90:2353–8.

[71] Viriya-empirikul N, Krasae P, Nualpaeng W, Yoosuk B, Faungnawakij K. Biodieselproduction over Ca-based solid catalysts derived from industrial waste. Fuel2012;92:239–44.

[72] Chakraborty R, Chowdhury D. Fish bone derived natural hydroxyapatite-sup-ported copper acid catalyst: taguchi optimization of semibatch oleic acid ester-ification. Chem Eng J 2013;215–216:491–9.

[73] Jairam S, Kolar P, Sharma-Shivappa R, Osborne JA, Davis JP. KI-impregnatedoyster shell as a solid catalyst for soybean oil transesterification. BioresourTechnol 2012;104:329–35.

[74] Deka DC, Basumatary S. High quality biodiesel from yellow oleander (Thevetiaperuviana) seed oil. Biomass Bioenergy 2011;35:1797–803.

[75] Toda M, Takagaki A, Okumura M, Kondo JN, Hayashi S, Domen K, et al. Biodieselmade with sugar catalyst. Nature 2005;438:178.

[76] Kastner JR, Miller J, Geller DP, Locklin J, Keith LH, Johnson T. Catalyticesterification of fatty acids using solid acid catalysts generated from biochar andactivated carbon. Catal Today 2012;190:122–32.

[77] Kang S, Ye J, Chang J. Recent advances in carbon-based sulfonated catalyst:preparation and application. Int Rev Chem Eng 2013;5(2):133–44.

[78] Fu XB, Chen J, Song XL, Zhang YM, Zhu Y, Yang J, et al. Biodiesel productionusing a carbon solid acid catalyst derived from B-cyclodextrin. J Am Oil Chem Soc2015;92:495–502.

[79] Chen G, Fang B. Preparation of solid acid catalyst from glucose-starch mixture forbiodiesel production. Bioresour Technol 2011;102:2635–40.

[80] Ayodele OO, Dawodu FA. Production of biodiesel from Calophyllum inophyllumoil using a cellulose-derived catalyst. Biomass Bioenergy 2014;70:239–48.

[81] Shu Q, Gao J, Nawaz Z, Liao Y, Wang D, Wang J. Synthesis of biodiesel from wastevegetable oil with large amounts of free fatty acids using a carbon-based solid acidcatalyst. Appl Energy 2010;87:2589–96.

[82] Dawodu FA, Ayodele O, Xin J, Zhang S, Yan D. Effective conversion of non-edibleoil with high free fatty acid into biodiesel by sulfonated carbon catalyst. ApplEnergy 2014;114:89–826.

[83] Fu X, Li D, Chen J, Zhang Y, Huang W, Zhu Y, et al. A microalgae residue based

carbon solid acid catalyst for biodiesel production. Bioresour Technol2013;146:767–70.

[84] Silva F, Batista LN, Cunha VS, Costa MAS. Production of catalyst to vegetable oilepoxidation from toxic biomass residue. Waste Biomass Valor 2016. http://dx.doi.org/10.1007/s12649-016-9616-z.

[85] Kong SH, Loh SK, Bachmann RT, Rahim SA, Salimon J. Biochar from oil palmbiomass: a review of its potential and challenges. Renew Sustain Energy Rev2014;39:729–39.

[86] Qian K, Kumar A, Zhang H, Bellmer D, Huhnke R. Recent advances in utilizationof biochar. Renew Sustain Energy Rev 2015;42:1055–64.

[87] Mani S, Kastner JR, Juneja A. Catalytic decomposition of toluene using a biomassderived catalyst. Fuel Process Technol 2013;382:197–204.

[88] Yan Q, Wan C, Liu J, Gao J, Yu F, Zhang J. Iron nanoparticles in situ encapsulatedin biochar-based carbon as an effective catalyst for the conversion of biomass-derived syngas to liquid hydrocarbons. Green Chem 2013;15:1631–40.

[89] Ormsby R, Kastner JR, Miller J. Hemicellulose hydrolysis using solid acidcatalysts generated from biochar. Catal Today 2012;190:80–97.

[90] Liu T, Li Z, Li W, Shi C, Wang Y. Preparation and characterization of biomasscarbon-based solid acid catalyst for the esterification of oleic acid with methanol.Bioresour Technol 2013;133:618–21.

[91] Guo F, Xiu ZL, Liang ZX. Synthesis of biodiesel from acidified soybean soapstockusing a lignin-derived carbonaceous catalyst. Appl Energy 2012;98:47–52.

[92] Lou WY, Zong MH, Duan ZQ. Efficient production of biodiesel from high free fattyacid-containing waste oils using various carbohydrate-derived solid acid catalysts.Bioresour Technol 2008;99:8752–8.

[93] Parshetti GK, Hoekman SK, Balasubramanian R. Chemical, structural andcombustion characteristic of carbonaceous products obtained by hydrothermalcarbonization of palm empty fruit bunches. Bioresour Technol 2013;135:683–9.

[94] Reza MT, Andert J, Wirth B, Busch D, Pielert J, Lynam JG, et al. Hydrothermalcarbonization of biomass for energy and crop production. Appl Bioenergy2014;1:11–29.

[95] Lu X, Jordan B, Berge ND. Thermal conversion of municipal solid waste viahydrothermal carbonization: comparison of carbonization products to productsfrom current techniques. Waste Manag 2012;32:1363–5.

[96] Liang X, Zeng M, Qi C. One-step synthesis of carbon functionalized with sulfonicacid groups using hydrothermal carbonization. Carbon 2010;48:1844–8.

[97] Deshmane CA, Wright MW, Lachgar A, Rohlfing M, Liu Z, Le J, et al. Acomparative study of solid carbon acid catalyst for the esterification of free fattyacids for biodiesel production. Evidence for the leaching of colloidal carbon.Bioresour Technol 2013;147:597–604.

[98] Shuit SH, Tan SH. Feasibility study of various sulfonation methods for trans-forming carbon nanotubes into catalysts for the esterification of palm fatty aciddistillate. Energy Convers Manag 2014;88:1283–9.

[99] Emrani J, Shahbazi A. A single bio-based catalyst for bio-fuel and bio-diesel. JBiotechnol Biomater 2012;2(1):1–7.

[100] Shu Q, Nawaz Z, Gao J, Liao Y, Zhang Q, Wang D, et al. Synthesis of biodieselfrom a model waste oil feedstock using a carbon-based solid acid catalyst: reactionand separation. Bioresour Technol 2010;101:5374–84.

[101] Dekhoda AM, Ellis N. Biochar-based catalyst for simultaneous reactions ofesterification and transesterification. Catal Today 2013;207:86–92.

[102] Li M, Zheng Y, Chen Y, Zhu X. Biodiesel production from waste cooking oil using aheterogeneous catalyst from pyrolyzed rice husk. Bioresour Technol2014;154:345–8.

[103] Zhang M, Sun A, Meng Y, Wang L, Jiang H, Li G. Catalytic performance ofbiomass carbon-based solid acid catalyst for esterification of free fatty acid inwaste cooking oil. Catal Surv Asia 2015;19:61–7.

[104] Babadi FE, Hosseini S, Soltani SM, Aruoa MK, Shamiri A, Samadi M. Sulfonatedbeet pulp as solid catalyst in one-step esterification of industrial palm fatty aciddistillate. J Am Oil Chem Soc 2016;93:319–27.

S.H.Y.S. Abdullah et al. Renewable and Sustainable Energy Reviews (xxxx) xxxx–xxxx

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