Challenges in biodiesel industry with regards to feedstock, environmental, social and sustainability issues: A critical review

Renewable and Sustainable Energy Reviews 58 (2016) 208–223

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Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Challenges in biodiesel industry with regards to feedstock, environmental, social and sustainability issues: A critical review Mohd Razealy Anuar, Ahmad Zuhairi Abdullah n School of Chemical Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia

art ic l e i nf o

a b s t r a c t

Article history: Received 6 March 2015 Received in revised form 14 December 2015 Accepted 27 December 2015

This paper addresses the challenges in developing a sustainable biodiesel industry especially in Malaysia. The challenges discussed in this paper are divided into three main sections covering issues before, during and after biodiesel processing. The pre-processing problems concern the feedstock market, legislation through policies, fuel–food competition, deforestation issue and alternative feedstock conflict. Problems with regards to the uncontrollable glycerol production and its global market crisis are also reviewed. Besides, some suggestions on poising back the glycerol market stability are reviewed through several upgrading processes and methods that can convert glycerol to its functional chemicals. The last section covers the social issue of biodiesel in obtaining people's acceptance and capability of this industry to cultivate the sustainable practices along the processing line. Moreover, challenges in verifying its commercial value by fulfilling the global biofuel standards are also highlighted. & 2016 Elsevier Ltd. All rights reserved.

Keywords: Biodiesel industry Challenges Feedstock Environment Social Sustainability

Contents 1. 2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Feedstock issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Feedstock demand and price fluctuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Tax, policy, subsidy and legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Competition with food industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Deforestation issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5. Waste cooking oil as feedstock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Waste management problems (glycerol by-production) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Glycerol from biodiesel production. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Glycerol glut problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Global glycerol market issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. Crude glycerol upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Quality and acceptance issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Quality and standards of biodiesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Acceptance of society to the new energy source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Advantages of biodiesel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Towards sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1. Sustainability background and schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2. Sustainability keywords and aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3. Quest towards sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

n

Corresponding author. Tel.: þ 604 599 6411; fax: þ604 594 1013. E-mail address: [email protected] (A.Z. Abdullah).

http://dx.doi.org/10.1016/j.rser.2015.12.296 1364-0321/& 2016 Elsevier Ltd. All rights reserved.

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1. Introduction The great invention of biodiesel by Rudolf Diesel in 1970s has been a historical beginning of alternative fuel to replace the fast depleting fossil fuel. Started when he demonstrated an impressive replacement of engine fuel with peanut oil [1]. The unexpected brilliant replacement was favorable and the research has evolved. Currently, efforts towards producing biodiesel from vegetable oil are widely studied. The high demand for biodiesel in replacing fossil fuels has driven many researches to come out with new ideas and inventions. Moreover, acts, policies and legislations on biodiesel implementation programs have been developed. They include the selection of sustainable feedstock, production process improvement, improvement in the quality of biodiesel, possible blending with petroleum fuels and etc. [2]. However, even though the burgeoning of biodiesel industry indicates more advantages than disadvantages, several obstacles remain. The challenges include problem faced during pre-processes, during processes (waste problem) and after-processes (quality and sustainability). Preprocesses are the most important in starting a good and economical biodiesel production. Problem will arise when the feedstock selection gets insufficient attention from the producer. It happens when the feedstock is too expensive compared to the processing cost itself. There is also a significant challenge to biodiesel industry when the demand for feedstock fluctuates and destabilizes their market. It sequentially causes another arising issues with regards to the policy, fuel–food competition, deforestation issue and waste oil feedstock problem. In the processing line, there are several problems that cannot be resolved with regards to the waste management problem, especially the by-production of crude glycerol. Less attention has been given until the glycerol has experienced a serious downturn in the market. This problem does not only affect the economic itself but it also severely creates an environmental issue with regards to the decomposition of glycerol. After the processing stage, quality verification step should be done to evaluate whether the biodiesel produced can be ideally used for engine and comparable with the existing fossil fuel. If its quality fulfills the international standard of biofuels which is the ASTM D 6751 [3], it can be used for transportation and industry purposes. Besides, the physic-chemical properties of the produced biodiesel should comply with the ASTM limits to meet the commercial specification of biofuels [4]. However, to fulfill that high quality standard, optimization and refinement of crude biodiesel are needed. Besides, there is also an acceptance issue by the society whereby biodiesel usually receives poor acceptance that might lead to the downturn of the biodiesel industry. This review will discuss about the challenges regarding the inline biodiesel processing problems including feedstock, policies, glycerol market crisis, product quality, societal acceptance and sustainability issues. In addition, some possible solutions to overcome the problem are suggested accordingly.

2. Feedstock issues 2.1. Feedstock demand and price fluctuation Before determining the biodiesel processing system, feedstock selection is the most important aspect that should be taken into account. The inappropriate selection of feedstock could cause the first problem which is the over budget production. In every production line, the feedstock price should not be more than 50% of the production cost. Higher cost (50–70%) of feedstock might result if refining and treatment are needed before feeding into the

Fig. 1. Palm oil and crude oil price fluctuation from 1997 to 2012 [5].

processing line. The addition of a treatment plant only for feedstock would lower the net profit of the industry. In Malaysia, palm oil is the most commonly used biodiesel feedstock as this country is among the biggest producers of palm in the world. Yield of palm oil in Malaysia is recently about 4–5 t per hectare [3] and palm oil trees can have commercial lifespan of about 25 years [5]. The oil production can start as early as in 3 years after cultivation but 8–9 years are generally considered the maturity age for the trees [3]. The comparison has been made between the price of crude palm oil and crude petroleum oil (Fig. 1) and it shows that their prices are comparable [5]. From January 2005 to January 2007, the price for crude petroleum oil was higher than crude palm oil. At the beginning of 2007, the prices were more or less the same but a sudden increase in the crude palm oil price occurred. The fluctuation trend of the prices for both oils started when Malaysia carried out a massive promotion on their palm oil as the source of alternative fuel [1]. The increase in stockpile has further encouraged the promotion to create the demand for crude palm. In tandem with that, the price of crude palm oil also increased up to USD 1150 per ton in early 2008, defeating the price of crude petroleum oil. The feedstock prices also experienced severe fluctuation as illustrated in Fig. 1. The price for both oils experienced either sharp increases or sudden decreases throughout 2007 and 2008. Sometimes, there is no benefit of producing biodiesel even if the price for of feedstock is comparable with that of the crude petroleum oil. The estimated biodiesel price should be relatively higher so that it is better to stick to the conventional fuel. It is made worse when there is insufficient publicity given to biodiesel and its advantages to the society. Thus, efforts to replace fossil fuel will not receive favorable response. Malaysia used to have bad experience with regards to this issue when its government mandated the use of B5 biodiesel. As a result, the license of the biodiesel plant had to be reduced [1]. Mekhilef et al. [6] reviewed the potential and capability of palm oil as a major feedstock in producing biodiesel. They concluded that the selection of palm oil as feedstock for biodiesel can significantly affect its market situation and subsequently causes the palm oil price fluctuation. However, the growth of biodiesel industry has created vast opportunity for the diversification of palm oil utilizations to create the demand for this oil. Janaun and Ellis [7] in their perspective view suggested that sequential scenario that will result from this issue could be related to the prognosis of the future outlook of palm oil industry. It includes the replacement of palm oil with alternative oils as feedstock. This might show the benefits of developing biodiesel industry to the sustainability of palm oil industry. Currently, palm oil is the most preferred choice for most biodiesel producers. Malaysia was stricken by dry spell starting from early December 2013 until April 2014. The draught significantly affected the palm oil plantation area and directly undermined the crude palm oil production. Over a period of 6 months (end of November 2013 until April 2013), the stockpile was at the low level and with this

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rate of production, the crude palm oil could not be sold at usual price. The previous year showed higher price due to the subdued stocks, sluggish export and also tepid performance of crude palm oil averaging at about RM 2550 [8]. The price was predicted to further push up and probably to the range between RM 2600 and RM 3000 a ton in 2014 [9]. 2.2. Tax, policy, subsidy and legislation One of the massive endeavors in order to empower the enforcement of biodiesel is the implementation of law and legislation. It also includes taxes, policies and subsidies from the government. Under certain circumstances, the enforcement needs certain laws and guidelines so that the economics of biodiesel will be systematically improved. Basic planning on alternative fuels had been proposed by the European Commission in which the renewable fuel should constitute 2% of the traffic fuel. By the end of 2010, the figure was predicted to increase to 5.75%. In tandem with this objective, necessary renewable fuel policies have been developed including mandates, tax incentives, and subsidies to ensure the viable expansion of biodiesel industry in the future [10]. This effort has widely opened the opportunities for biodiesel to be used globally thus replace petroleum-based fuels as the world's main energy source. According to Ong et al. [11], larger share of global biofuel market was previously dominated by ethanol. However, biodiesel has placed itself on top of the list to be the most demanded fuel in the market. Moreover, this situation proved that the adopted policies (tax, mandates and incentives) successfully drove the growth of biodiesel, especially in the European Unions and Asia. This encouragement was highly needed so that the development was on the right track and effectively enhanced the enforcement of the legislations [11]. In Malaysia, MPOB (Malaysian Palm Oil Board) is the premier government agency with the responsibility to keep the progression of Malaysian palm oil sector with full support from the government. The agency focuses on constructing the commercial palm biodiesel plants with a capacity of 60,000 t per annum starting from the design, installation and commissioning of the plant. This effort also includes the development of new technologies for producing palm biodiesel and winter-grade palm biodiesel. By utilizing all resources from palm oil such as the palm fruits and palm biomass, its research and development division has focused on the best resources to be technically used by considering on the value of the resource itself [12]. It was reported that, there were 12 biodiesel plants that were in operation in 2013 with a total production capacity of 1.22 million tons per annum [13]. When Kyoto Protocol was introduced in the late 90s, is also encouraged MPOB to streamline back their objectives which include the uplifting of biodiesel as a possible substitution fuel

[14]. This was also reinforced with the introduction of the Envo Diesel through the National Biofuel Policy in 2006 [15]. The idea was to blend 5% of biodiesel with petroleum fuel and the blending would save an enormous amount of petroleum that might prolong the depletion period of the fossil fuel [1]. However, the project was halted because of the market failure in 2008 [2,16]. It was mainly due to the apprehension on the engine whereby the blending might cause engine clogs. On the other hand, the failure of Envo Diesel gave way to methyl ester (B5) program and it was initially used in February 2009 [16]. The B5 program was strengthen with the subsidies provided by the Malaysia government whereby almost RM 300 million (RM 80 per ton) was spent in order to establish B5 biodiesel blending and storage facilities in peninsular region [17]. It was reported that, starting from July 2013, the government kicked start the implementation of B5 to various regions except the Central Region where the establishment was started back in 2009. It included the Southern Region (July 2013), Northern Region (October 2013), Kelantan and Terengganu (December 2013) and lastly East Malaysia that was expected to launch come mid 2014 [18]. Once the implementation runs smoothly, further framework was drafted in which 7% and 10% blends of methyl ester (B7 and B10 biodiesels) would be the next focus [8,13,17]. However, it was not that easy when some problems arose when the price of petroleum was around USD 100 per barrel so that the B5 biodiesel was still unprofitable. It might be caused by the insufficient subsidies provided to make the B5 biodiesel price comparable with petroleum. For such a situation, consumers had no reason to switch to B5 biodiesel when the price was not reasonable and the quality was still dubious. Moreover, lack of advertisement in the society caused people's lack of awareness about this product. Besides, the availability is also limited to certain regions and outlets making it difficult to be found when needed. In 2006, the government of Malaysia prescribed a systematic enforcement of biodiesel through the formulation of the National Biofuel Policy that enlisted 5 key thrusts including all sectors in Malaysia [2,19]. This initiative brought about a favorable consequence on the implementation of biodiesel and one of the biggest initiatives was to upgrade its acceptance to the next level. The policy covers entirely the benefits to major consumers in Malaysia. Besides, the opportunities offer comprise between the development of new working sector, national income and global consultancy on environmental issues. As shown in Table 1, few ideas for strengthening the biodiesel industry and future outlook results from the good practice of the policy are highlighted. There are opinions claiming that biodiesel might become a savior to the depleting petroleum diesel. However, there are also opinions regarding the ineffectiveness of policies that lead to the failure of biodiesel policies. The issues are usually related to the lack of monitoring of licensed companies and standards. Mekhilef

Table 1 Suggestion on ideas and outlook of biofuel thrusts. Thrust

Ideas and outlook

Transportation

          

Industry

Technology

Exports Cleaner environment

Gradually increases the subsidies for biodiesel every year and lower the subsidies for petroleum diesel. Increase the availability of biodiesel in rural area by increasing the number of outlets even in the interior region. Intensified biodiesel starts from the minor machinery and equipment. Comprehensive maintenance and monitoring for major equipment. Emphasizing the consumption of biodiesel in agriculture sector. Establishment of specialized agency for national management of biodiesel. Creates job opportunities and formulation of new syllabus regarding biodiesel in educational institution. Open the opportunities for Malaysia to become a global expertize in biodiesel industry. Diversified national income in addition to oleochemicals and petroleum industry. Malaysia can become an international role model in establishing good policy and practice in biodiesel industry. Serves as a global consultant in controlling greenhouse gasses issue once the implementation of biodiesel is successful.

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et al. [6] had their own view on this problem in which the policy was claimed to be still ineffective with the sluggish mechanism in enforcing the policy and infrequent monitoring of the licensed companies. This might cause a tepid performance of biodiesel. As an active member of the Roundtable Sustainable Palm Oil (RSPO), Malaysia should frequently monitor the enforcement according to the established guidelines [20]. 2.3. Competition with food industry The proliferation pace of biodiesel supported by governmental policies is not yet guaranteed when there is another issue that arises which is the constraint from food industries. It is especially relevant to oleochemical industry which is well recognized as the major palm oil product consumer and this industry uses entirely palm oil as feedstock. However, the boom in biodiesel industry to some extent will threaten the smoothness of this industry and the demand for the feedstock would sharply increase year by year. Lim and Teong [1] highlighted that palm oil had high demand as feedstock in Malaysian food industries. Palm oil is healthier if compared to other resources because of its saturated and unsaturated fatty acids contents, medium chain triglycerides and also its special antioxidant quality. For such a good quality, it is not technically justified to turn it into fuel that will finally be converted into greenhouse gasses. Biodiesel industry has also been blamed by some non-governmental organizations because of the rapid expansion that directly caused shortage in the supply of palm oil. Thus, resources availability would be limited and the price would sharply increase [1,21]. High demand for the feedstock consequently causes negative impact on economical value of food which is food inflation. In one of the bioenergy publications of Purdue University, Alexander and Hurt [22] made arguments on the impact of biofuels to the food industry according to several questions regarding food inflation and the sustainability impact towards stabilization of food industries. They concluded that food inflation might occur and it is influenced by the increase in farm prices of commodities. It will happen when there is a competition for land between different crops. The competition is caused by greater incentives given so that it encourages them to expand the farm to meet the demand. Thus, with the increase in the land prices, the cost of food supply would also increase and this might cause consumers to suffer from food inflation [22]. Doornbosch and Steenblik [23] claimed that 50 l of biofuel is equal to 200 kg of feedstock (maize) that is grossly predicted to similar with 1 year supply for one person. It seems like the implementation is far more important than to fight the hunger. Thus, they listed 2 integrated ways of simultaneous production between fuel and food industries. First, it combines the land used for both fuel and food feedstock and the plantation will be carried out stage by stage. Secondly, the transformation of by-product of a system as the feedstock for the other should be attempted. In line with this effort, research works are needed and some new inventions for utilizing waste or by-product should be explored [23]. 2.4. Deforestation issue Sustainability strategies towards implementation of biodiesel in Malaysia are not only focused on reduction of green house gasses emissions. In fact, the complete package is about being economically and environmentally friendly. However, in maximizing the proliferation of biodiesel production, one issue that is usually ignored is deforestation. Demand on crops increased with the advent of the biodiesel program especially in Malaysia. Biofuel industry has been blamed for the replacement of virgin rainforest

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with palm oil plantation. Deforestation in lower latitude area might cause global warming while that at higher latitude causes global cooling [24]. Whereas the utilization of biodiesel in many sectors is expected to stabilize the carbon-cycle, the deforestation process would destabilize it. Currently, 20% of Malaysia's oil palm is planted on the drained peat land and mostly located in the state of Sarawak [25]. In only 5 years time, almost 10% of entire Sarawak's rainforest that covered 353,000 ha of peat swamps forest had been cleared for palm oil plantation purposes [26]. As a consequence, the emission of greenhouse gas was estimated at about 40 t of CO2 per hectare per year of peat land palm oil plantation, thus, causing a massive contribution of some 20 million tons of CO2 annually [27,28]. Efforts by the Roundtable Sustainable Palm Oil (RSPO) were severely criticized because the guidelines were ineffective and the deforestation issue was not holistically addressed [1]. Besides uncontrollable deforestation of peat swamp forest, RSPO was also criticized because of the irregularities committed against animal in jeopardy with possible extinction of various species particularly orangutan. This issue was questioned by a board protecting the rights of orangutan called ‘The Orangutan Project (TOP)’. In one of their web pages [29], they stated that there is confusion between having RSPO certification and being RSPO member. In addition, there also questioned about the RSPO certification criterion of ‘Primary Forest’ and the requirement to maintain the ‘High Conservation Values (HCV)’ area. They claimed that forest containing orangutan did not meet that criterion, thus, that area could be arbitrarily deforested. The issue has also been touted by other organization that focusing on research regarding global warming. The Union of Concerned Scientists also doubted the ‘Certified Sustainable Palm Oil (CSPO)’ provided by RSPO and claimed that there was no guarantee for deforestation-free [30]. Changes in the indirect land use should also be given full attention. Even though sustainability program and policy are usually focused on direct deforestation, unnoticed land use change still happens. This problem is rather severe in Central America, Mexico and Brazil. It is caused by the abuse of power and higher land prices that prompt poor farmer to sell their holdings [21]. For this reason, EU Renewable Energy Directive has put some requirements on the types of land that can be used as biofuel feedstock plantation. There are 4 criteria which include the area like primary forest, wetland, continuously forested area and land with specific tree height and canopy type [31]. However, these criteria are not complete as they do not involve the protected animal rights. 2.5. Waste cooking oil as feedstock One of the approaches to overcome the market and demand fluctuations, the insistence from food industry and deforestation is by replacing the edible with non-edible feedstock. For this purpose, waste cooking oil can be seen as the most ideal replacement since it is highly available and very cheap. In this section, the ability of waste cooking oil in replacing crude palm oil and challenge behind it will be discussed. Utilization of virgin oil or crude oil for biodiesel production is one of the solutions. Feedstock represents almost 80% of total biodiesel production cost. Thus, by using waste oil as feedstock, it might cut the production cost since it can be acquired at almost no charge [32]. Due to the high food consumption in restaurants, fast food chains, shopping centers and food manufacturing facilities, high amount of waste cooking oil is generated. This might facilitate the search for feedstock by its availability. Thus, investigation of its performance as biodiesel is also highly recommended. However, a new challenge could be faced as the feedstock might contain high free fatty acid (FFA) and water contents.

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Usually, the FFA content for waste cooking oil is about 0.5–15% whereas for a refined oil, it is about 0–0.5% [33]. Moreover, it will be very challenging as the product from the use of high impurities feedstock needs to meet the international standards for biodiesel (ASTM D 6751 and EN 14214) so that it can be further used as fuel [34,35] Javidielesaadi and Raeissi [36] reviewed the effect of high FFA and water contents feedstock and they identified 2 major disadvantages. It included the contamination of catalyst used by the FFA and also the competition problem of biodiesel price and diesel fuel cost. This might also require the addition of pre-treatment processes and the unit also faces the risk of pipeline corrosion [1,36]. High impurity waste oil should be subjected to several refining processes before entering the biodiesel processing unit. This might create another challenge whether the standard quality of treated waste oil will meet the quality that is offered by virgin or crude oil. At this stage, the refined waste oil would determine the effectiveness of the whole processing line. According to the standard of refined waste oil feedstock, the treatment processes also include degumming, caustic refining, bleaching and deodorization so that it is usually called Refined Bleached and Deodorized Palm Oil (RBDPO) [37]. When the idea of using waste oil is the best alternative for replacing crude oil, then there must be a good collection planning. The collection system should cover the whole country including the hospitality sectors and every region. However, it is easy to plan than the enforcement if the tight promotion is not widely exposed to society. It will be very difficult because they will stick to the conventional method of disposing waste oil either by pouring down into the sewage system or waste it together with other garbage to the landfill. The main obstacle of using this type of feedstock is mainly due to the difficulty encountered in waste collection system as its sources are normally scattered. To make it easy and acceptable by the society, the collection should be handled with no charge. The system should also include the periodically collection time, availability of facilities like waste oil drum container, waste oil recycler lorry while the collection should also cover rural areas. What makes waste cooking oil differs from virgin oil is the content of triglycerides. Thus, for determining the effectiveness of biodiesel production, 99.5% of it should be triglycerides. The obstacle for utilizing waste cooking oil as biodiesel feedstock is the presence of polar compounds and impurities. Pursuant to several reviews on waste cooking oil as biodiesel feedstock [38,39], the frying process and exposure to high heat might change the physical properties of the oil. Unwanted reactions could have occurred and undesired product would be produced. Three unwanted reactions expected during frying are thermolytic, oxidative and hydrolytic reaction in which every reaction might cause the

production of harmful compounds [38]. Table 2 lists all the unwanted reactions and the corresponding undesired products. The presence of impurities in waste cooking oil is unavoidable since the frying purpose is carried out at high temperatures. Besides, there are also the food scraps and high water content that might interfere in the biodiesel production. Basically, pretreatment processes can improve the physical and chemical properties. Thus, the main objectives for intensifying the pretreatment involve the removal of solids scraps, organic compounds, free fatty acids and water contents [32]. All these methods are listed in Table 3 below. Even though the pre-treatment processes have been extensively studied, when applied to pilot plant treatment, it might require high cost. The more waste cooking oil collected, the more impurities will be removed and consequently creates another problem which is solid waste from the harmful organic compound. In conjunction with that, research on used cooking oil solid waste management should be carried out before it becomes another uncontrollable problem. In conjunction to this, Phan and Phan [49] reviewed that pre-treatment process is highly required when acid value of the oil is above 2%. Moreover, they also reviewed successful research works on alkali transesterification of waste cooking oil having high acid value without any pre-treatment process [49].

3. Waste management problems (glycerol by-production) 3.1. Glycerol from biodiesel production Recently, endeavors to reduce the usages of fossil fuels and included renewable fuels as the future main fuels have been underway. In 2005, the European Union Directive stated that the renewable fuel should constitute 2% of the traffic fuel and by the end of 2010, the figure was predicted to increase to 5.75%. In tandem with this effort, necessary renewable fuel policies have been developed that they could cover the mandates, tax incentives and subsidies to ensure the viable expansion of biodiesel industry in the future [10]. This effort has widely opened the opportunities of biodiesel to be used globally to replace petroleum based fuels as the world's main energy source. Basically, biodiesel is produced from the transesterification process of triglyceride in which 90 wt% of methyl ester (biodiesel) and 10 wt% of glycerol are produced. The process is enhanced by alkali catalysts to produce better biodiesel yield. This has been reviewed by Leung et al. [50] and they mainly focused on the effects of some critical variables such as catalyst type and reaction conditions. The optimized reaction conditions might assist in overcoming the undesirable reactions that will lead to the

Table 2 Undesired reactions and products during frying process. Reaction

Description

References

Thermolytic reaction Conditions: High temperature with the absence of oxygen [40] Products:  From saturated fatty acids – alkanes, alkenes, symmetric ketones, oxopropyl esters, lower fatty acids, carbon monoxide and dissolve carbon dioxide.  From unsaturated fatty acids-dehydrodimers, saturated dimers and polycyclic compounds polymerized unsaturated fatty acids reaction through Diels–Alder reaction. Oxidative reaction Conditions: Reaction of oil/fat with dissolve oxygen, mainly reaction of oil with unsaturated acylglycerols. [39,41] Products: Various oxidation products e.g. alkoxyl radicals, saturated and unsaturated aldehydes, ketones, hydrocarbon, lactones, alcohols, acids and esters, dimeric and polymeric acid and volatile polar compounds e.g hydroxyl and epoxy acid. Physical change: Increase in viscosity. Hydrolytic reaction Conditions: Occurs when steam is produced during preparation of food. [40] Products: Dissolved water oil/fat, fatty acid, monoglycerides and diglycerides.

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Table 3 The pre-treatment methods for purifying waste cooking oil. Pretreatment method

Description

References

Filtration

Purpose: Removing food scraps, solids, inorganic material, substances carbonaceous produced from burnt organic material and solid fats or products of low melting points from the frying process. Operating procedure: Using vacuum suction operated at high (above 60 °C) and low temperature. Centrifugation Purpose: Removing solid matter. Operating procedure: Using centrifugation at 3500–4000 rpm in 25–30 min. Preheated Purpose: Removing moisture and water content. Operating procedure: Heating in oven (100–110 °C) for desired time or heating at 100 °C with continuous stirring for 15–20 min. Deasidification (Neutralization) Purpose: Removing free oils fatty. Operating procedure:  Neutralization with alkaline solution: acid is removed by saponification. Carried out using KOH as catalyst at 65 °C for 90 min. Removing high polymer content by treating with activated charcoal. Determining the sufficient amount of catalyst used by titration with NaOH.  Neutralization by caustic soda: bleaching the dark color oil by making soaps.  Esterification with glycerin.  Extraction by solvents: extracting by means of ethanol (1.3 times the amount of oil).  Distillation: Distillation of fatty acids requires high energy cost.  Ion-exchange: Using strongly basic resin character for removal of free fatty acids and color. Steam injection Purpose: Reducing humidity, free fatty acids content, viscosity and increase the calorific power. Operating procedure: Steam and sedimentation method. Involving two steps 1) heating oil at 65 °C followed by sedimentation. Dehydration Purpose: Reducing water content and humidity. Operating procedure: Drying using magnesium sulfate, anhydrous sulfate or calcium chloride (drying agent) followed by filtration under vacuum to remove any suspended matter especially drying agent crystal.

production of undesired products (soap and etc.) while at the same time directly increases the biodiesel yield. Conventionally, the market of glycerol has developed on the basis of 3 major strides. Each of them may have a substantial effect on the long term glycerol production market. The strides begin with the development of glycerol production industry from the approval for the use of Olestra by the end of 1994 by the US Food and Drug Administration. Then, it was followed by the investment of the large scale corn fermentation (bioethanol) in the United States [51]. Currently, the development continues with the main focus given to glycerol that is produced as a by-product from the manufacture of biodiesel. By-production of glycerol from the transesterification process is achieved when the triglycerides (animal or plant fats) consisting of 3 long chains fatty acids are linked to 3 hydroxyl groups with an ester bond upon reaction with an alcohol causing the breakage of the ester bond. This reaction directly cleavages the ester bond thus producing crude solution of glycerol in water [50,52]. Meanwhile, the fatty acid chains that are released will combine with carbonyl group from the alcohol to form biodiesel. From 1992 to 2003, glycerol production was dominated by fatty acids and soap industries where the amount of glycerol produced was quite stable and the price at that time was rather high with high market demand (Fig. 2). After 2005, biodiesel industry emerged and dominated the production of glycerol amounting to nearly 60% compared to other industries (2006–2010). The production of glycerol from biodiesel sharply increased from about 400,000 MT in 2005 to the outstanding amount of 1,600,000 MT in 2010. This domination gave significant impact on the surplus of glycerol where the sudden increase made the glycerol market price unstable. 3.2. Glycerol glut problem Despite of the worldwide drastic increase in biodiesel production, there is an inevitable problem that arises which is the glycerol glut. The world market of glycerol is currently facing an oversupply problem which is purportedly caused by the intensification of biodiesel industry. The production of biodiesel through the transesterification process creates a massive amount of

[42,43]

[39]

[39,41,42]

[44]

[45–48]

Fig. 2. Glycerol production by source [10].

Fig. 3. Market of glycerol in 2010 [10].

glycerol by-product. As shown in Fig. 3, it was reported in 2010 that 64% of glycerol market originated from biodiesel industry while another 34% was contributed by fatty acids, fatty alcohol, soap and other industries. The boom of biodiesel industry causes the domination of the global glycerol production. Besides, the development of biodiesel also has enticed many biomass sources to be used as raw materials. This scenario has influenced the oleochemical industries to face the same implication as well.

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Table 4 Fraction of biofuels and global production of glycerol. Year

Fraction of biofuel (by European Union Directive)

2005 2% 2010 5.75% 2020 20%

Global production of glycerol (tons) 0.8 million [10] 1.25 million [53] 7.66 million (prediction) [12]

When the raw material used in the oleochemical industry is quite similar to that in biodiesel industry, there is a competition on the supply of raw materials and causes its price to increase. In line with this, the advent of biodiesel will directly cause an overabundance of glycerol and indirectly causes a decline in the oleochemical industry. From previous section, the renewable fuel policy can be correlated with the sharp increase in glycerol production from 2005 to 2010. The fraction of biofuel recommended by European Union Directive has clearly influenced the global production of glycerol. It is noted in Table 4 that the enforcement of the policy to constitute 5.75% of traffic fuel with renewable source in 2010 was directly involved in the increase of glycerol production. The estimation has been made by Yazdani and Gonzalez [53] in which up to 1.25 million tons of glycerol might be produced when the enforcement is fully implemented. The enormous increase in glycerol production (7.66 million tons) has been estimated to happen when the renewable energy content is further increased to 20% in the future (2020). The implementation of the energy policy is such a good endeavor that should be done with respect to the promotion of renewable energy in the future. However, holistic consideration on the glycerol surplus problem should also be given a serious attention.

Fig. 4. Price fluctuation of glycerol [54].

Fig. 5. Crude glycerol export by country [10].

3.3. Global glycerol market issues With the current rate of production, the global amount of glycerol is expected to increase every year and the surplus of glycerol might cause the plummeting of the global glycerol price and market demand. High purity natural glycerol has a fairly stable market price and the global market demand was also very promising of about USD 1200 to USD 1800 per ton from the 1970s until the last few years before the emergence of biodiesel industries [52]. The production of biodiesel affected the global glycerol market with the sudden increase to 800,000 t of glycerol produced in 2005 (400,000 t from biodiesel) compared to only 60,000 t in 2001 [53]. Fig. 4 shows the fluctuation of glycerol price over the recent years. As suggested by the figure, the production and price of glycerol trend are interrelated. From 1996 to 2001, the glycerol price was reported to be stable with a stable production of glycerol. However, there were rather small ups and downs in the market price trend of glycerol. The price dropped from 1996 to 1998 in about 325 USD/Mg but it was poised back in 2000 (870 USD/Mg). Even when the fluctuation was significant, the price at that time was still acceptable. Unfortunately, from 2004 onwards, the market was facing a worst downturn when the price sharply decreased until below 100 USD/Mg. It is actually predicted to further decrease if the feasible technology for utilizing glycerol to be converted to value-added products cannot be developed in time. Therefore, instead of enforcing necessary policy for the promotion of renewable fuel, the consequent effects with respect to the vulnerability of glycerol should also be schemed out. Thus, efforts and technologies that lead to the development of the

glycerol utilizing industry can be encouraged to poise back the glycerol market. The value of crude glycerol has miserably dropped until the current prices for pure glycerol and crude glycerol are quoted at USD 0.50 to USD 1.50/lb and USD 0.04 to USD 0.33/lb, respectively [55]. Most biodiesel producers attach zero value to the crude glycerol, and at least some producers have to pay for its transport to a purification unit. Crude glycerol can be assumed to have a negative value in the future [52]. Malaysia and Germany are the two largest exporters of glycerol in the world as shown in Fig. 5. Export of crude glycerol from Germany decreased steadily over time and decreased to nearly zero by 2007. This is because the market price for crude glycerol did not meet the cost to ship crude glycerol from Europe to the United States [10]. The market price value of crude glycerol was grossly low compared to that of pure glycerol. The value of glycerol market price is some time does not meet the shipping cost which is very high from different countries to the United States. Thus, the exports from Germany will face a loss. Similar problem can also happen to Malaysia. Palm oil industry in Malaysia has historically put the country as the major player in the free fatty acids in the international arena. As the advent of biodiesel industry, free fatty acid has become the most crucial raw material. It means that, the country will produce even more glycerol as the biodiesel production is intensified. Thus, the export value of Malaysia's crude glycerol will experience further decline until it achieves nearly zero in the future. Technically, in 2011, it was expected that 2 million tons of the total 5.1 million tons of glycerol would be used which meant that only 40% of the crude glycerol was utilized while the remaining 60% was considered as oversupply [56]. In 2007, 490,000 t of crude

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glycerol was sold in Europe and by 2013, the market was expected to reach 775,700 t [57]. The 2008 consumption was estimated at 395,000 t with a 1.7% growth per year [58]. 3.4. Crude glycerol upgrading In 1990's, glycerol was traditionally produced as a by-product of fats hydrolysis in soaps production and this process was significantly one of the contributors to the global glycerol production volume of about 600,000 t annually. However, soap industry as the main producer for glycerol was getting lesser importance due to the replacement of soaps with detergent [59]. Unfortunately, in 2000 onwards, the scenario worsened with the emergence of biodiesel industry that contributed about 65–85% (w/w) of crude glycerol [60,61]. Crude glycerol from biodiesel contains a variety of other elements such as metals e.g. calcium, sodium, potassium, magnesium, phosphorous, or sulfur and 25% carbon [62]. Hence, purification process is highly required. The refining processes depend on the availability of glycerol purification facility such as filtration, chemical addition and fractional vacuum distillation to yield a commercial grade and also economically depends on the production scale [62]. There is a problem when the 80% purity of glycerol is still not considered as an acceptable quality as it is usually contaminated with methanol. It has been a major focus for the glycerol refiner that they have to produce a pharmaceutical-grade glycerol with nearly 100% purity. The currently developed technology to remove impurities present in the biodiesel by-product glycerol is based on high temperature low-pressure distillation process. However, as glycerol is contacted with methanol, it is unsuitable for that type of process [63]. Consequently, majority of companies that produce glycerol have shut down their production due to the plunge in glycerol prices [64,65]. The next problem that emerges from the surplus of low value crude glycerol is its disposal problem. Incineration is the current method of disposal for the surplus glycerol in which it is used to produce energy [66,67]. However, burning of glycerol as a fuel will cause the generation of toxic material as at high temperature as glycerol will polymerize and partially oxidizes into acrolein which is a highly toxic material [68]. Thus, glycerol from biodiesel industry should be transformed into suitable value-added chemicals instead of being incinerated that may produce a highly polluting material. Besides, it is desirable to produce something new from the transformation of low value glycerol to that can provide benefits to the economy and society. Problems regarding the surplus of glycerol that are directly responsible for the market downturn of global glycerol market can be overcome by invention towards utilization of glycerol itself. In order to upgrade the low graded glycerol, its molecular structure can be polymerized through etherification process. The process will upgrade glycerol to the other value-added products and might broaden the potential for utilization of glycerol to many industries. Therefore, the surplus problem can be effectively managed. Catalytic etherification of glycerol can enhance its conversion to form useful products. It can be catalyzed by either homogenous or heterogeneous catalyst. Conventionally, homogeneous catalyst is usually used [69–71]. Whereas the conversion of the fuel is usually high, it gives some problems with respect to the difficulty to separate the product as both reaction product and catalyst are in the same phase. Homogenous catalyst is nowadays gradually being replaced with heterogeneous catalyst that is more beneficial in terms of catalyst separation and reusability. Furthermore, the design of the solid catalyst has made significant advancement in which both physical and chemical characteristics of the catalyst can be modified. This is a clear advantage compared to homogenous catalyst in which only chemical characteristics can be

215

altered. As such heterogeneous catalyst is more flexible while the robustness of the catalyst can be improved by modifying the surface area, pore size, particle size and chemical composition [72– 75]. Heterogeneous catalysts could be acidic or basic in nature. For etherification, it is preferred to use basic catalyst rather than acidic one as the product is more selective (avoid higher oligomer) while showing higher etherification activity [74,76]. However, there is a problem when dealing with basic catalyst with respect to the leaching of active material. The active metal component in the catalyst could leach out from the structure to cause lower product purity. Many researchers are striving to come out with various catalytic systems in order to solve the leaching problem. Acid catalyzation has several disadvantages where the reaction products formed are cyclic polyglycerols. Deterioration of product quality will occur as it can lead to secondary reactions which are dehydration and oxidation of the intermediate product [69]. Whereas, the conversion of reactant to product is relatively higher and faster, the selectivity is still low [70]. Basic catalysis of glycerol seems to be very effective as the product is more selective with higher degree of conversion. Glycerol can be categorized into three main types which are crude glycerol, purified glycerol and refined or commercialized glycerol. Crude and purified glycerol show significant differences in several parameters where the purification processes on the crude glycerol are really needed to obtain a refined and commercialized glycerol to be used in many applications. The general differences are shown in Table 5. The effort of upgrading crude glycerol is to increase the glycerol content to decrease the contaminant content, to achieve pH neutralization and to remove the cloudy color. The glycerol produced from any processes such as transesterification as by-product is regularly a glycerol mixture with about 60–80% of glycerol purity. Increasing the glycerol content to 99.8% usually requires costly processing steps in order to meet the expected quality of the refined or commercial glycerol. Crude glycerol contains high amount of impurities and it differs from purified or refined glycerol in which the moisture, ash and soap contents should be reduced to at most 0.1%. The abundance of glycerol with the currently uncontrolled production has enticed many attempts especially among researchers to come out with new inventions that can be utilized to cope with the glycerol surplus problem. The upgrading from low graded to high graded glycerol has been widely attempted with various methods of modification on the physico-chemical characteristics of glycerol. There are many research works towards the upgrading of glycerol to other products through etherification, oligomerization, esterification of glycerol and many other processes to convert it to its derivatives [63,78,79]. Fig. 6 shows the possibility of glycerol to be upgraded to high value added chemicals through several processes. In this case, the glycerol is either Table 5 Quality parameters of crude, purified and refined/commercial glycerol [77]. Parameter

Crude glycerol

Purified glycerol

Refined/commercial glycerol

Glycerol content (%) Moisture content (%) Ash (%) Soap (%) Acidity (pH) Chloride (ppm) Color (APHA)

60–80

99.1–99.8

99.2–99.98

1.5–6.5

0.11–0.8.

0.14–0.29

1.5–2.5 3.0–5.0 0.7–1.3 ND* Dark

0.054 0.56 0.10–0.16 1 34–45

o 0.002 N/A 0.04–0.07 0.6–9.5 1.8–10.3

*

N.D. Not determined.

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Fig. 6. The platform of glycerol to its functional chemicals [79].

directly converted to functional chemicals or glycerol derivatives like glycerol carbonate are being used as starting materials in many industries. Behr et al. [78] reviewed the glycerol derivatives produced by several processing including the formation of glycerol esters, glycerol ethers, glycerol acetals and ketals, glycerol to functional chemicals and also the formation syngas from glycerol. Esters of glycerol can be produced by reacting glycerol with carboxylic acid in a transesterification process under suitable reaction conditions [80]. Carbonylation of glycerol in which the glycerol carbonates are produced by reacting carbon dioxide and glycerol is also possible [81]. The directly reacting glycerol with certain catalyst can enhance the production of glycerol oligomers (di-, tri-, tetraglycerol and etc.) under specific reaction conditions [72,76,82]. Meanwhile, when glycerol is reacted with aliphatic alcohol, alkyl halide and addition of alkene, the alkyl ethers of glycerol are produced [83]. Telomerisation of glycerol will produce unsaturated ethers of alcohol that can be utilized as surfactants due to their amphiphilic nature [84]. Besides, they also reviewed the formation of functional chemicals from glycerol [78]. The acetalisation of glycerol will produce various aldehydes or ketones that are very useful as ignition accelerators and antiknocks additives, scent or flavor, basis of surfactant and disinfectant or solvent in cosmetics or medical purposes [85,86]. The hydrogenolysis of glycerol will produce propanediols which are applicable as diols in the production of polyesters, polycarbonates and polyurethanes and as additives, solvents and other chemical agents [87]. Epichlorohydrin from glycerol can be produced from the reverse of classic synthesis and it consumes less water. The oxidation of glycerol product is categorized based on the degree of oxidation of hydroxyl group [88]. The oxidation of secondary, tertiary and further oxidation of

hydroxyl will produce dihydroxyacetone, glyceraldehydes and a series of carboxylic acids, respectively. Meanwhile, the dehydration of glycerol will produce acrolein which is applicable as an intermediate in the production of acrylic acid, glutaraldehyde and methionine [89,90]. Lastly, glycerol can be used to synthesize synthetic gases including carbon monoxide and hydrogen through specific reforming of steam and gasification process [91,92]. The summary of glycerol derivatives and applicable processes are tabulated in Table 6.

4. Quality and acceptance issue 4.1. Quality and standards of biodiesel In promoting and enticing people with the effectiveness of biodiesel as replacing fuel, the quality of biodiesel produced must fulfill the global standard of biodiesel. The main focus of biodiesel framework in Malaysia is to achieve B100 standard which meet with the standard of ASTM 6751 as prescribed by the American Society for Testing and Materials or European Standards EN 14214 [3]. At this stage, biodiesel can stand alone and completely replace the petroleum fuel as the standard quality is highly guaranteed. However, the real challenge along the production line is to ensure the quality of biodiesel produced meet the international standard. Different feedstocks would produce different qualities of biodiesel in which differs according to its content. After the process of converting triglycerides and free fatty acid to biodiesel, the product must undergo another refining plant to ensure the quality meet the standard as commercial fuel. If there is lack in observing the quality of biodiesel, it might affect the consumers especially transportation engine and also the industrial machinery.

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Table 6 Summary of glycerol derivatives. Glycerol derivatives

Process

Product

Reference

Glycerol esters

Esterification, Carbonylation

[80,81,93]

Glycerol ethers

Etherification, Oligomerization, Telomerisation

Glycerol acetals and ketals

Acetalisation, Transacetalisation

Glycerol to propanediols Glycerol to epoxides Glycerol oxidation and dehydration

Hydrogenolysis Oligomerization Oxidation, Dehydration

Glycerol to synthesis gas

Steam reforming, Aqueous phase reforming (APR), Supercritical water gasification (SCWG)

Glycerol esters with carboxylic acid e.g. monoglycerides, diglycerides, glycerol carbonates. Glycerol oligomers e.g. diglycerol, triglycerol and etc. Glycerol alkyl ethers e.g. glycerol 1-monoethers, glycerol tertiary-butyl ether (GTBE), sodium glycerolate etc. Glycerol alkenyl ether (telomers) e.g. unsaturated ethers of glycerol. Cyclic acetals e.g. [1,3] dioxan-5-ols, [1,3] dioxolan-4-ylmethanols. 1,2-propanediols and 1,3-propanediols. Epichlorohydrin Glycerol oxidation product e.g. dihydroxyacetone (DHA), glyceraldehyde, glyceric acid, tartonic acid, mesoxalic acid. Glycerol dehydration e.g. acrolein Carbon monoxide, pure hydrogen

[76,83,84,94]

[85,86,95,96] [87,97,98] [99] [88–90]

[91,92]

Table 7 Major problems associated with the application of poor quality biodiesel [102]. Major problem

Engine parts

Major causes

Deposition  Carbon  Heavy gum  Wax Blocking, coking and plugging

Piston, piston rings, valves, engine head, injector tips and cylinder wall

High viscosity, poor combustion, oxidation

Corrosion

Filter, injector, nozzle,

Polymerization and poly-substances problem (polyunsaturated oil), impurities, glycerin, monoglyceride, diglyceride, triglyceride, solid foreign material and chemicals. Pump (high pressure injecting, supply and Impurities e.g. water, acids, methanol, chemicals (NaOH or KOH). feed pump), injectors, nozzles, high pres- High viscosity, iodine value and acid number. sure pipes Piston, nozzle, rubber Polyunsaturated vegetable oil, polymerization, water, methanol.

Lubricating failure and elastomer (nitrile rubber softening, swelling, hardening, cracking) Cold performance failure Spark plug, cylinder, ring, piston

Consequently, this might cause a serious boycott from society and significantly tarnish its integrity as replacing fuel. For current production, it is still too far to achieve the B100 standards as there are many challenges during the processing line. Implementing 100% purity of biodiesel as fuel is highly difficult since the production from waste-based feedstock still needs sturdy processing line that comes out with very pure methyl ester product. In conjunction with that, as the biodiesel utilization in many sectors is still scarce, the blend standard set by ASTM 975 is the best platform to provide the opportunity for this fuel to be recognized. This standard has prescribed the biodiesel produced to specify the diesel standard so that it can drive up the petroleum diesel performance. However, with the problems occurred during processing, even this blending standard is difficult to achieve. In order to make sure the biodiesel produced can be commercially used, these standard including ASTM 6751, EN 1424 and ASTM 975 should be followed or it just left as unusable fuel [100,101]. Ong et al. [11] have reviewed the effect of biodiesel to transportation and it has given a negative drawback to the engine including formation of injector coking due to unsuitable fuel characteristics. Jayed et al. [102] reviewed all the problems affecting biodiesel and the causes are thoroughly explained. From the review, several problems have been highlighted including all failures that might occur to the engine parts. Generally, the poor biodiesel quality might give severe effect to the engine and it mostly in the form of deposition, blocking, plugging, corrosion, lubricating failure and cold performance failure. All problems and causes are concluded in Table 7.

High viscosity, low flash point and low cetane number.

One scenario that can happen among the biodiesel producers, distributors and consumers is with regards to the quality of biodiesel. One of the well-known sites that are focusing on the updates of biodiesel globally exposes that, this problem arose when the non-conformance ASTM 6751 standard biodiesel was sold it quickly collect many complaints from consumers [103]. This has put the fuel distributors as victims and received many complaints from consumers related to poor quality in which the terrible technical problems were associated with the fuel itself. When inspection was done, the problem was actually caused by the fuel that was contaminated by glycerol and impurities. 4.2. Acceptance of society to the new energy source Consequent to the issue regarding standards and quality of biodiesel, it might lead to the next issue which is acceptance by society. When the consumers are experiencing a bad perception with misleading by biodiesel producers, it is difficult to them to accept it. Otherwise, they have gain strong assurance about the quality before use it to their transportation. Besides, they also want money back guarantee if there any happen to their transportation or machinery while totally using biodiesel. In Japan, the automobile manufacturing company JAMA (Japan Automobile Manufacturers Association) has stated their rejection on biodiesel because of the temperature incompatibility properties of biodiesel that causes high damage to their engine such as filter plugging, corrosion and also not compatible with material used in engine [1]. In implementing new product that might change the world perception, a good model regarding acceptance should be

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developed. Wüstahagen et al. [104] claimed that the efficacy on acceptance of biofuel should mainly include by three perspectives including socio-political, community and market. These perspectives have been well illustrated in their triangle dimension model of social acceptance. The model could be a good reference in generating a sturdy acceptance from all parties. According to the model, the most vital dimension is from the socio-political view where it acts as a pioneer and initiator to the biofuel program [104,105]. The related aspects such as development of technologies, policies, subsidies, and also attention from stakeholder should be streamlined so that strong base on biofuel can be created. From this model, it can be analyzed that, the continuous support from many parties is the most important in which the succession of biofuel is coming from trust. If any problem can be avoided and immediately solved with some supports thus the establishment of biofuel industry would achieve high penetration in fuel market globally. However, there was a bad propaganda amidst the development of Malaysian palm oil industry towards strengthening the county's biodiesel market base. The defamation was perpetrated by American Soybean Association (ASA) that claim the Malaysian palm oil would cause a severe problem on healthy when consumed by human. At that moment, supports from Malaysian related agencies were highly needed to deny the defamation. The MPOB and RSPO has come forward to refuse the tension and defending the Malaysian palm oil market [1]. From this scenario, it proves that, the supportive attempts especially in developing a strong biodiesel base in any country especially Malaysia should gained at the first place followed by the support and acceptance from others. In one of the analysis and survey regarding social acceptance on biodiesel, one of the factors that contribute to the increasing of biodiesel consumers is education [106]. The highly educated people are those who expected to have more information and well recognize biodiesel as the most ideal alternative fuel. However, the expectation is not much to rely on when the high education has instigate this group of people to recognize biodiesel based on its disadvantages and negative perception that have been touted. Based on the survey of the willingness to pay (WTP) of biodiesel, the high educational people are the group who are not willing to pay for this fuel. On the other hand, the group that gains less information about this fuel is willing to pay for replacing their transportation fuel with biodiesel. Supposedly, biodiesel should not be blamed only just looking to its negative impact to environment and food industry but they should have considered on the beneficial value especially towards sustainability. The advance production technologies with the most ideal feedstock and the high quality biodiesel produced are still unsuccessful unless this fuel is well accepted by society. Basically, this is the most difficult issue to overcome because it relates to the people trust. We can find the best feedstock and we can fix any problem during the production line. However, when it comes to people trust and willingness to use the fuel, it literally needs massive attempts. We cannot blame the society or force them to accept unless those people who working in this area to give high commitment especially in convincing people to accept this fuel. Even the authorities should exhibit a good discipline in replacing the depleted petroleum with biodiesel. 4.3. Advantages of biodiesel It is unfair to blame biodiesel with bad pre-judgment since the advent of this industry still in the developing stage and need a comprehensive observation. Since it can be categorized as new thus the growth is not yet complete. There are many improvement should be executed for the fuel to be viable with the existing one. Although its application is still debatable and questionable, there

are some compelling reasons for this fuel to stand up as the best option to replace petroleum fuel. As a supportive society, all the advantages should be taken into account because it has been developed with holistic consideration. Thus, this fuel deserves an opportunity to show its credibility and appear as a savior for petroleum depleting problem. All the biodiesel advantages that include environment, economic, performance and social sides are highlighted in Table 8. This might give well exposure to society the probabilities that can be triggered especially in re-stabilization of the global energy fuel in the future.

5. Towards sustainability 5.1. Sustainability background and schemes In other perspective, all the challenges confronted by biofuel industry have indirectly lifted up the maturity level of this industry especially in managing the environmental problem. Serious effort in addressing the challenges has enlighten the global organization to redesign the sustainability program which includes issues on feedstock, geographic land region and some legislations are enacted because of the impact of biofuel industry to the environment. In 2011, the European Commission reframed the sustainability program through 7 main voluntary schemes that were applied directly to 27 members [108]. By targeting a minimum share of 10% renewable energy in transportation by 2020, the schemes has guaranteed to control 3 major issues regarding environment. Firstly, the guarantee of conservation of tropical rainforest and peat land in enlarging the feedstock plantation area. Secondly, biofuel would results in tangible greenhouse gas savings. Thirdly, the implementation of sustainable practice is for the entire biofuel production and supply chain. It involves the holistic view of sustainability in every aspect during the production line. Table 9 provides some brief overview of the 7 voluntary schemes. From the entire schemes, it can be analyzed that, the framework is focusing on two main sustainable criteria which are the greenhouse gas emission control and protection of biodiversity plantation area. The scheme has also provided the certification system for biofuel producer. In any processing related to biofuel either feedstock or production line, they must be certified and periodically monitored in order to avoid factors that might cause the environmental issue. Besides, it also emphasizes the conservation of protected rainforest and peatland as well as the protected animal habitats. Moreover, the stabilization on the economic side of feedstock from diversified sources has been focused especially in overcoming the food–fuel competition issue. The explicit goal of the scheme is actually to cultivate the sustainable concern throughout the processing line of biofuel. As such, it can be widely practiced in every production stage starting from the feedstock plantation area until it is converted to the product. This also highlights the importance of good sustainable starts that consequently lead to the real production of environmental friendly fuel. Above all, these schemes have been supported by legal international organization and accredited by International Accreditation Forum [110]. The best way of implementing the correct way of sustainability practices is by exposing the real concept and its basic framework. Attempts have been made by European Directive in dividing and managing the global sustainability practices according to particular schemes of feedstock [109]. It provides an explicit guideline and directs the sustainable discipline through the role of stakeholders and supportive organizations. Thus, the intervention of organization in encouraging the sustainable practice is highly necessary. In conjunction with that, Maletič et al. [111] provided a clear explanation on understandings of conceptual framework that

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Table 8 Advantages of biodiesel. Advantages

Reference

Environment  Biodiesel is renewable, non-toxic, non-flammable, portable, readily available, non-visible smoke and noxious fumes and odors and free from sulfur and aromatic content.  Fewer greenhouse gases emissions such as CO2, CO, SO2, particulate matter and hydrocarbon compared to diesel hence reduces air toxicity  Carbon-dioxide emissions reduction by 78% on a lifecycle basis and reduces smoke due to free soot.  Helps in stabilizing carbon-cycle because the combustion of palm based biodiesel does not increase the level of CO2 in the atmosphere  The feedstock can be sustained by re-planting and systematic plantation scheme.  Biodiesel is biodegradable and safe to handle means any spill over will be easier and cheaper to clean up.  Helps Malaysia to oblige to the Kyoto Protocol treaty by reducing greenhouse gases emission to required target.  Encouraging other industries related to production of biodiesel to do some transformation to environment-friendly production system.  Reducing cancer risks and neonatal defects.  Reducing environmental effect of a waste product since the use of cooking oils and lards are compatible as biodiesel feedstock. Economic  Potentially increase the country's gross income.  More cost efficient as it can be produced locally and not required importation business.  Raise the country's self-esteem as Malaysia's capabilities could be demonstrated in the international stage.  The great source for country's revenues due to the exportation to other countries. Performance and technology  Easy to produce and consume short production time compared to diesel.  Biodiesel has a cetane number of over 100 in about 60–65 depends on the type of vegetable oil that makes the vehicle perform better and reduces the ignition delay.  Prolongs engine's life and less maintenance in which biodiesel has better lubricating qualities that improves lubrication in fuel pumps and injector units which decreases engine wear, tear and increases engine efficiency.  Unlike diesel engine, it can be used without adding additional lubricant since it possesses high clarity and the purity characteristics.  No drilling, transporting and refining process as it locally produced from various feedstock and can be produced by any country thus there is no tariffs or taxes to pay for importation.  No required engine modification for low percentage blending. Minor modification required only exceeding B20 blending.  Higher combustion efficiency since it has 10–11% of oxygen.  Suitable for operations in countries where the pour point is low as it possesses the winter grade compatibility biodiesel.  High flash point (above 100–170 °C) makes it safe for transportation, handling, distribution and utilization. Social  Potentially stimulating a sustainability practice for development of many aspects and sectors related to biodiesel industry.  Promoting rural development by reducing petro-diesel dependency and evolving the agricultural industry thus helps to restore the degraded land.  Creates good potential on rural employment through development of agricultural.  Strengthening the country's economic ability by reducing the total unemployment rate.  Great solution for energy security issue.  Indirectly increase the living standard of the villagers in Malaysia (mostly are estate workers).  The growth of biodiesel industry can actually trigger the advancement of upstream and downstream industries.

[2,4] [1,2,6,107] [4,6] [107] [6,107] [6,107] [1] [4] [4]

[2,4,107] [1] [1,6] [2] [2,4] [4] [2] [2,4] [2,4,6] [2,4] [6,107] [2,4,6]

[1,2,6] [4,6,107] [1,107] [6,107] [6,107] [1]

Table 9 Brief overview of sustainability schemes [109]. Schemes

Brief overview

ISCC (International Sustainability and Carbon Certification)

Background – A voluntary certification system focusing on justifying a sustainable differentiation of biomass, biofuels and bioliquids include the monitoring of greenhouse gas emissions. Supported by the German Federal Ministry of Food, Agriculture and Consumer Protection via the Agency for Renewable Resources (FNR). Scheme scopes – All feedstock and geographic locations. Also covers all economic operators along the supply chain. Background – A global multi-stakeholder non-profit initiative of sugarcane based ethanol standard dedicated to reducing the environmental and social impacts of Brazilian sugarcane production. Scheme scopes – Sugarcane and all geographic locations. Bonsucro Production Standard and Bonsucro Mass Balance Chain of Custody Standard Background – A global platform that highly aims the economically, socially and environmentally sustainable soy production comprised by stakeholders from throughout the soy value chain. Scheme scopes – Soy and feedstock cultivated outside the European Union. RTRS EU RED Compliance Requirements for Producers, and the RTRS Chain of Custody Standard. Background – A development of an international standard for sustainable biofuels production and processing, applicable to all feedstock in all geographical locations by multi-stakeholder initiative. Scheme scopes – All feedstock and geographic locations Background – A French initiative that demonstrate to Member States the sustainability criteria relating to greenhouse gas savings, land with high biodiversity value and land with high carbon stock and peatlands. Scheme scopes – All feedstock and geographic regions. Cover the whole supply chain (from the biomass producer to the final biofuels distributors). Background – An initiative scheme developed by Abengoa Bioenergia. A company's mechanism designed to prescribe the sustainability criteria included in RED (GHG savings, land with high biodiversity value and with high carbon stock). Scheme scopes – All feedstock and geographic region. Two options for fuel chain which are from agricultural production units until biofuel conversion unit and from agricultural production units until final economic operator. Background – An initiative developed by Greenergy International Ltd that implemented a verification program for Brazilian sugarcane bioethanol based on the UK Government's Renewable Transport Fuel Obligation (RTFO). Scheme scopes-Sugarcane feedstock only (for the production of bioethanol) and geographic region of Brazil only.

Bonsucro EU

RTRS EU RED (Roundtable for Responsible Soy)

RSB EU RED (Roundtable on Sustainable Biofuels)

2BSvs (Biomass Biofuels Sustainability voluntary scheme)

RBSA (Abengoa RED Bioenergy Sustainability Assurance)

Greenergy Brazilian Bioethanol verification program

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relates the sustainability practices with organizational performance. They proposed the concept of corporate sustainability through proposed conceptual and theoretical framework approach in literature. They also highlighted the types of sustainability practices in their conceptual research that include the sustainability exploitation and sustainability exploration. The practices have contributed to the starting point of sustainability strategy in any organization and also encouraging the cultivation of corporate sustainability while competing in global market [111]. 5.2. Sustainability keywords and aspects The development in biodiesel industry is not a conundrum. It is a serious effort to overcome the severe issue on petroleum depletion. Besides, it also provides a good practice on sustainability and empowering renewable energy not only for petroleum but for all non-renewable resources. The successful of sustainable program can be achieved generally through three main keywords which are motivation, strategy and enforcement. A good starts will followed by a good end. Holistically, sustainable is not only focusing on preserving nonrenewable resources but it embraces many aspects and covers all related element so that it provides benefits for present and future generations. There are many sustainable ways that can be referred as it organized to complete the related aspects in developing biodiesel industry. Besides, the pathway would not ignore and always prioritizes the consideration of the impact either towards society, environment and also economic. For such considerations, Basiron and Yew [112] had their view on the evaluation of sustainability. By referring to the surrounding issues related to biodiesel industry, they stated that the sustainability should be viewed through the three major aspects. 5.3. Quest towards sustainability The fostering of sustainability especially in biodiesel industry is limitless. Before the production is carried out with a viable pace, the underlying issues that must first be focused are the sustainable fundamentals. Once the practices are strictly followed, then the issues regarding environment and food crisis are able to be controlled. As the time goes by, the biodiesel industry is booming in tandem with the sustainability enculturation in any types of industry. Consequently, the sustainable transformation of industries would be significant and the production of biodiesel might increase without risking the environment with the negative impact. However, the transformation would be materialized when there is no intensive assessment and systematic monitoring procedure towards sustainability program. For that reason, in mid2006, the Global Bioenergy Partnership (GBEP) was created with the participation of 10 nations and 7 international organizations [113]. Up until 2011, there were 23 partner countries and 13 partner international organizations participated. Malaysia has participated as an observer country. The GBEP has an explicit mission in promoting the extensively production of renewable energy based on three strategic areas which are sustainable development, climate change and food and energy security. The partnership activities are also guided by 24 indicators where they describe the three pillars of sustainable development including economic, environmental and social. However, Hayashi et al. [114] had their own opinion on these indicators. They questioned the unclear sustainability definition and the lack of holistic assessment on the final judgment from the GBEP indicators. In conjunction with that, they came out with the assessment tool and clarification on the sustainability concept of bioenergy program [114]. They proposed the Multi-Criteria Analysis (MCA) and concluded that,

some of the GBEP indicators were not related to sustainability. In addition, by focusing on lowering the production cost, the policymaker would promote the sustainability through the economic viability. de Mora et al. [115] had their own way in defining sustainability through the concept of energy balance. In their work, they highlighted the sustainability practices through the calculation of energy return on investment (EROI). EROI has been introduced in one of the commercial work of energy balance calculation by Cleveland et al. [116]. However, there are some limitations on EROI where the quality of energy is not included and it might cause the misleading in balancing the energy used for production [116,117]. Thus, the new quality correction calculation on energy balance has been proposed in which the exergy and the capacity to produce energy have taken into account. Basically, exergy is the minimum amount of work required to produce energy. For that reason, the concept of Exergy Return on Exergy Investment (ExROI) was defined [115]. ExROI is the new approach on energy balance that relates between the exergy of a particular resource and the amount of exergy required. From the calculation using ExROI, it can be concluded that, ExROI is the appropriate tool to determine the energy required to produce biodiesel. Besides, ExROI is another indicator for sustainability and the concept is a parameter that using energy input–output value in determining sustainability in biodiesel production. The advent of renewable energy era has shown the emergence of many perspectives and opinions on sustainability. The perspectives basically cover the sustainable criteria that require any related industries to follow. Besides, it is purposely created for preventing the uncontrollable problem, especially towards environment. It also includes the social and economic perspectives that can be categorized as the main pillars on sustainability criteria. However, the abundance of opinions and perspectives might create confusion while the issues remain debatable. This issue has enticed Buccholz and the co-workers [118] to come out with a series of surveys in order to analyze the most critical sustainability criteria. From the literature and previous works, there are 35 sustainability criteria have been identified [119–121]. The criteria were grouped into 3 broad categories which are further divided into 15 social criteria, 16 environmental criteria and 4 economic criteria. The surveys were conducted to 137 bioenergy experts where each expert is considered as influential in the discussion of sustainability assessment of bioenergy system. The experts need to rate all 35 sustainability criteria to 4 attribute including relevance, practically, reliability and importance. The results from the survey showed that, energy balance and greenhouse gasses are the most critical sustainability criteria as it received the highest ratings. Besides, some of the criteria that received low ratings were characterized as gaining lack of consensus and the inclusion in sustainability assessment is still debatable. As can be analyzed from the survey, the assertion on the environmental issue is significant whereby most international organizations have specified the importance of sustainability to preserve the environmental rights. For that reason, many bioenergy companies in Asia and all over the world have started their pace in applying the sustainability practices. In Malaysia, the empowerment of sustainability practices was carried out by introducing the green initiative program. The aim of the program was to encourage the green initiative by developing National Green Technology Policies and Green Building Index [122]. The initiatives were fully supported by Ministry of Energy, Green Technology and Water. It was accelerated by GreenTech Malaysia and Green Technology Council. Besides, the initiatives also proposed the Fiscal incentive like the one stated in the National Budget 2009 that included pioneer status, investment tax allowance and exemption from payment of Import Duty and/or Sales Tax. In order to assess the effectiveness of the green

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initiatives program, Eltayeb and the co-worker [123] conducted a survey on green supply chain. The sampling frame was represented by 569 ISO 14001 certified firms to analyze the actual outcomes and effectiveness of green supply chain initiatives. The survey proved that the initiatives were successfull in empowering sustainability through social, environment and economic benefits (‘triple bottom line’). According to Manan et al. [124], the empowerment of sustainability in Malaysia could be achieved by implementing the energy efficiency (EE) award. By referring to several developed countries, the encouragement of EE awards might be significant in Malaysia [124]. After a survey on ‘Proposed implementation of EE award in Malaysia’ was conducted, the stakeholders showed their readiness and acceptance in implementing such awards in Malaysia. Thus, the empowerment of sustainability is emphasized in tandem with the advancement of biodiesel industries in Malaysia.

6. Conclusions Biodiesel is a buzzword in overcoming nowadays global petroleum depletion issue. Although biodiesel would give a big impact in conserving the non-renewable resources, this industry has been stricken by misconception, prejudice and bad prejudgment. For these reasons, biodiesel application is still questionable and debatable with some arguments that cause bad perception in the society. From the pre-processing towards the production of commercial biodiesel, this industry has been confronting with many challenges including feedstock, environment issues, waste glycerol glut problem, product commercialization and acceptance by the society. All the challenges should be addressed with systematic solutions so that the downturn of biodiesel industry will never happen. With the ordination of biofuel policy, the future of biodiesel is more secured where it is totally supported by legislation and government subsidies. Besides, it could also foster the sustainable practice when the non-edible feedstock like waste cooking oil is alternatively used to replace the edible vegetable oil as feedstock. For uncontrollable waste glycerol production problem, the issue could be oppositely shifted to a beneficial value when it might entice a new opportunity in researching the needs for glycerol upgrading. In conjunction with that, it would directly encourage the development of glycerol market besides creating a new framework of glycerol application to many industries. The holistic view on the advantages of biodiesel has been focusing on the sustainability where it relates to many aspects and elements. With all the challenges and solutions to overcome the issues concerned, it indirectly cultivates the sustainable discipline in every sector, thus, biodiesel will gain a full trust from the society. Lastly, this review provides a good exposure and consciousness to the scenario that hit the biodiesel industry nowadays. It also highlights the importance of the establishment of biodiesel industry to address the critical global petroleum issue and stands as the reason for future comfort.

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