ABSTRACT
Biodiesel  was  produced  from  the  seed  oil  of  Luffa  cylindrica.  The  oil  obtained  was transesterified to produce methyl-esters and glycerol. The percentage oil yield of 36.32% was obtained from Luffa cylindrica seed. Biodiesel properties of methyl-esters were determined using American Society for Testing and Materials (ASTM) Standards and compared with that of petrodiesel. The methyl-ester yield of 92.06 % was obtained from Luffa cylindrica seedoil. Higher viscosity at 40oC (15.50 mm2/s) was obtained for the seed oil whereas it  was reduced to 3.80 mm2/s after transesterification  which is comparable with that of  biodiesel standards.  Lower  heating  value  (29.39  MJ/kg)  was  obtained  for  methyl-ester  of  Luffacylindrica compared to 42.85 MJ/kg obtained for petro diesel. Higher pour, cloud and flash points of 4 oC, 8 oC and 150 oC respectively were obtained for Luffa cylindrica seed methyl- ester, compared to -12 oC, -16 oC and 74 oC respectively obtained for petrodiesel. Biodiesel produced from Luffa cylindrica seed oil had cetane number (71.93), refractive index (1.465 nm)  and  relative  density  (0.88  kg/m2)  which  is  comparable  to  biodiesel  standard.  The chemical  properties  acid  value  (0.52  mgKOH/g)  and  iodine  value  (57.87  mgI2/g)  also compared well with most standard biodiesel. The seed oil of Luffa cylindrica could be a good source of biodiesel.
CHAPTER ONE
INTRODUCTION
Biodiesel is an alternative fuel made from renewable biological sources such as vegetable oil and animal fats (Raja et al., 2011). Due to the depleting world’s petroleum reserves, threatening to run out in the foreseeable future and the increasing environmental concerns, there is a great demand for alternative sources of petroleum- based fuel including diesel and gasoline (Sambo, 1981; Munack et al., 2001). Indiscriminate extraction and increased consumption of fossil fuels have led to the reduction of the underground-based carbon resources (Ramadhas et al., 2004). Biofuels are produced from renewable sources; they do not add to the stock of total carbon-dioxide in the atmosphere. These plant forms remove carbon-dioxide from the atmosphere and give up the same amount when burnt within a few years. Hence, biofuels are considered to be “CO2 neutral” (Ramadhas et al., 2004). The primary goals of National Energy Policy are to increase the energy supplies using mixtures of domestic resources and to reduce our dependency on imported oil or petroleum. As a domestic renewable energy source, biomass offers an alternative to conventional energy sources and supplements national energy security, economic growth and environmental benefits (Ma and Marcus, 1999). Currently, biodiesel is considered a promising alternative due to its renewability, better gas emission, non toxicity and its biodegradability (Hossain et al., 2010). Plant oil and animal fats contain three ester linkages between fatty acids and glycerol which makes them more viscous. Among the techniques applied to overcome the difficulties encountered in using vegetable or animal oil in engines, transesterification of oil to biodiesel seems the most promising (Zhang et al., 2003). The high viscosities of vegetable oils are reduced through the process of transesterification (Alamu et al., 2008). The production of biodiesel from edible and non edible oil has progressively affected food uses, price, production and availability (Rashid et al., 2008). Vegetable oil seeds that do not compete with traditional food crops are needed to meet existing energy demands (Xu and Marcus, 2009). Reducing the cost of the feedstock is necessary for biodiesel’s long-term commercial viability. In order to achieve production cost reduction and make biodiesel more competitive with petroleum diesel, low cost feedstocks, such as non-edible oils, waste vegetable oils could be used as raw material (Xiaohu and Geg, 2009). In this research therefore, attempt is being made to explore the oil of Luffa cylindrica seed from Nigeria in an industrial process for the production of biodiesel.
1.1 Luffa cylindrica plant.
Loofa is derived from the cucumber and marrow family, and originates from America (Mazali and Alves, 2005). Luffa commonly called sponge gourd, loofa, vegetable sponge, bath sponge or dish cloth gourd, is a member of cucurbitaceous family. The number of species in the genus Luffa varies from 5 to 7. Only 2 species L. cylindrica and L. acutangula are domesticated. 2 wild species are L. graveolens and L. echinata. Loofa sponge is a lignocellulosic material composed mainly of cellulose, hemicelluloses and lignin (Rowell et al., 2002). The fibers are composed of 60% cellulose, 30% hemicelluloses and 10% lignin and the fruits smooth and cylindrical in shape.
Luffa cylindrica has alternate and palmate leaves comprising petiole. The leaf is 13 and 30 cm in length and width respectively and has the acute-end lobe. It is hairless and has serrated edges. The flower of L. cylindrica is yellow and blooms during August-September. The plant is cultivated in many countries, including Brazil, where its cultivation has an increasing economic importance (Mazali and Alves, 2005).
Luffa cylindrica is a sub-tropical plant, which requires warm summer temperatures and long frost-free growing season when grown in temperate regions. It is an annual climbing plant which produces fruit containing fibrous vascular system. It is a summer season vegetable. It is difficult to assign with accuracy the indigenous areas of Luffa species. They have a long history of cultivation in the tropical countries of Asia and Africa. Indo-Burma is reported to be the center of diversity for sponge gourd. The main commercial production countries are China, Korea, India, Japan and Central America (Bal et al., 2004).
The oil extracted from L. cylindrica is finding increasing use in the production of biodiesel which is now gaining wide acceptance because of low CO2 emission and other considerations (Ajiwe et al., 2005).The plant is classified as follows:
Luffa cylindrica Linn.
Kingdom : Plantae Division : Mangoliophyta Class : Mangoliosida Order : Cucurbitales Family : Cucurbitaceae Genus : Luffa
Specie : Cylindrica
Vernacular Names
Hindi : Ghiatarui Sanskrit : Rajakoshataki Bengali : Dhundul Tamil : Pikku
Telungu : Guttibira Bombay state : Ghosali Malayalam : Tureippirku
Fig.1.1. Luffa cylindrical seed. (Moser, 2009) Fig. 1.2. Luffa cylindrical Fruit. (Moser,
2009)
In oriental medicine, L. cylindrica has effect on the treatment of fever, enteritis and swelling etc. The extracts from its vines are used as an ingredient in cosmetics and medicine (Lee et al., 2006). Immature fruit is used as vegetables, which is good for diabetes (Bal et al., 2004). In Nigeria, Luffa cylindrica plant grows in the wild and on abandoned building structures and fenced walls in towns and villages (Ndukwe et al., 2001).
1.2 Biodiesel
Biodiesel is a mono-alkyl ester of long chain fatty acid derived from renewable biological sources (ASTM, 2008a). It is used directly in the compression ignition engine (Knothe et al., 1997). Biodiesel is a clean burning alternative fuel that comes from 100% renewable resources. Many people believe that biodiesel is the fuel of the future; it is occasionally referred to as biofuel. Biodiesel which is derived from triacylglycerol by transesterification and from the fatty acids by esterification has attracted considerable attention during the past decade as a renewable, biodegradable, eco-friendly and non- toxic fuel (Knothe et al., 2006; Demirba, 2008). Recently, it is used as a substitute for petroleum based diesel due to environmental considerations and
depletion of vital resources like petroleum and coal (Ma and Marcus, 1999). The possible use of renewable resources as fuels and as a major feedstock for the chemical industry is currently gaining growth.
The majority of biodiesel today is produced by alkali-catalyzed transesterification with methanol, which results in a relatively short reaction time. However, the vegetable oil and alcohol must be substantially anhydrous and have low free fatty acid content, because the presence of water or free fatty acid or both promote soap formation. Generally, transesterification is used to produce biodiesel from vegetable oil or animal fat containing low free fatty acid (FFA) through a reaction involving alcohol and an alkaline catalyst (Ma et al., 1998; Gerpen et al., 2004; Prateepchaikul et al., 2007). When biodiesel is produced from high FFA oils by transesterification, the high FFA content in the oils reacts with the metallic alkoxide to produce soap (Brown et al., 2003; Gerpen et al., 2004). In addition, if oils contain high moisture content, saponification and hydrolysis occur. These reactions cause a lower yield and washing difficulty. The problem can be solved via four methods: enzymatic-catalyzed transesterification, acid-catalyzed transesterification, a supercritical carbon dioxide technique and a two-stage process (Ma and
Marcus, 1999).
Fig. 1.3: Production of biodiesel. Source: (Moser, 2009a)
Three moles of biodiesel and one mole of glycerol are produced for every mole of triacylglycerol that undergoes complete conversion. The transesterification reaction is reversible, although the reverse reaction (production of monoacylglycerols from fatty acid alkyl esters and glycerols) is negligible largely because glycerol is not miscible with fatty acid alkyl esters
especially fatty acid methyl esters (FAME) when using methanol as the alcohol component. The reaction system is biphasic at the beginning and at the end of biodiesel production as methanol, vegetable oil glycerol and fatty acid methyl esters are not miscible. The chemical composition of biodiesel is dependent upon the feedstock from which it is produced, as vegetable oils and animal fats of differing origin have different fatty acid compositions. The fatty ester composition of biodiesel is identical to that of the parent oil or fat from which it is produced. Vegetable oils such as soybean oil, rapeseed oil (canola oil) and in countries with more tropical climates, tropical oils (palm oil and coconut oil) are the major sources of biodiesel (Demirbas, 2006). However, in recent years, animal fats and recycled greases as well as used vegetable oils have found increasing attention as sources of raw materials for the production of biodiesel, as the latter primarily is inexpensive feedstocks (Mittelbach and Tritthart, 1988).
In all the feedstocks, transesterification reactions are carried out to produce biodiesel. The vegetable oil production and biodiesel feedstock usage are intimately related. Feedstocks for biodiesel production vary with location according to climate and availability (Demirbas, 2006). Generally, the most abundant commodity oils or fats in a particular region are the most common feedstocks. Thus, rapeseed and sunflower oils are principally used in Europe for biodiesel production, palm oil which predominates in tropical countries are widely used in tropical countries, soybean oil and animal fats are most common in the United States of America (Demirbas, 2006). During the transesterification process, intermediate glycerols, mono- and diacylglycerols are formed; small amounts can remain in the final biodiesel (methylester) product. Besides these partial glycerols, unreacted triacylglycerols, unseparated glycerol, free fatty acids, residual alcohol and catalyst can contaminate the final product. The contaminants can lead to severe operational problems when using biodiesel such as engine deposits, filter clogging, or fuel deterioration. Therefore, in the United States, an ASTM (American Society for Testing and Materials) standard is developed and also, in some European countries, such as Austria, Czech Republic, France, Germany and Italy, standards have been developed that limit the amount of contaminants in
biodiesel fuel. In these standards, restrictions are placed on the individual contaminants by inclusion of items such as free and total glycerol for limiting glycerol and acylglycerols, flashpoint for limiting residual alcohol, acid value for limiting free fatty acids and ash value for limiting residual catalyst (Mittelbach, 1994).
1.2.1 Advantages and disadvantages of biodiesel.
The advantages of biodiesel as a diesel fuel are portability, availability, renewability, higher combustion efficiency, lower sulfur and aromatic content (Ma and Marcus, 1999; Knothe et al., 2006), higher cetane number and higher biodegradability (Mudge and Pereira, 1999; Speidal et al., 2000 ; Zhang et al.,
2003), as well as its potential for reducing a given economy’s dependency on imported petroleum, high flash point and inherent lubricity in the neat form (Mittelbach and Remschmidt, 2004; Knothe and Steidly, 2005). Biodiesel is better than diesel fuel in terms of sulfur content, flash point, aromatic content and biodegradability (Bala, 2005). The economic advantages of biodiesel are that it reduces greenhouse gas emissions, helps to reduce a country’s reliance on crude oil imports and supports agriculture by providing new labor and market opportunities for domestic crops. In addition, it enhances lubrication and is widely accepted by vehicle manufacturers (Palz et al., 2002).
The major disadvantages of biodiesel are its higher viscosity, lower energy content, higher cloud and pour points, higher nitrogen oxide (NO) emissions, lower engine speed and power, injector choking, engine compatibility, high price and higher engine wear (Prakash,1998). When biodiesel is used instead of pure petro diesel, fuel consumption rises with the overall cost of application of biodiesel as an alternative to petro diesel. Biodiesel neat and blends increase nitrogen oxide (NO) emissions compared with petroleum-based diesel fuel used in an unmodified engine. Peak torque is lower for biodiesel than diesels; on average it decreases power by 5% compared to diesel at rated loads (Demirbas, 2006). The technical disadvantages of biodiesel/fossil diesel blends include problems with fuel freezing in cold weather, reduced energy density and degradation of fuel under storage for prolonged periods. One additional problem is encountered when blends are first introduced into
equipment that has a long history of pure hydrocarbon usage. Hydrocarbon fuels typically form a layer of deposits on the inside of tanks and hoses. Biodiesel blends loosen these deposits causing them to block fuel filters. However, this is a minor problem easily remedied by proper filter maintenance during the period following introduction of the biodiesel blend. Many of these deficiencies can be mitigated through cold flow improver (Hancsok et al.,
2008) and antioxidant (Tang et al., 2008) additives, blending with petro diesel (Benjumea et al., 2008) and reducing storage time (Bondioli et al., 2003). Additional methods to enhance the low-temperature performance of biodiesel include crystallization, fractionation (Kerschbaum et al., 2008) and transesterification with long or branched-chain alcohols (Wu et al., 1998).
Strategies to improve the exhaust emissions of biodiesel, petrol diesel and blends of biodiesel in petro diesel include various engine or after-treatment technologies such as selective catalytic reduction (SCR), exhaust gas recticulation (EGR), diesel oxidation catalysts and NO or particulate traps (McGeehan, 2006). However, feedstock acquisition currently accounts for over 80% of biodiesel production expenses, which is a serious threat to the economic viability of the biodiesel industry (Retka-Schill, 2008). One potential solution to this problem is employment of alternative feedstocks of varying type, quality and cost. These feedstocks may include soapstocks, acid oils, tall oils, used cooking oils, waste restaurant greases, various animal fats, non-food vegetable oils and oils obtained from trees and microorganisms such as algae. However, many of these alternative feedstocks may contain high levels of free fatty acids (FFA), water, or insoluble matter, which affect biodiesel production (Moser, 2009a)
1.2.2 Alcohols used in the production of biodiesel.
As previously mentioned, methanol is the most common alcohol used in the production of biodiesel. Other alcohols may also be used in the preparation of biodiesel such as ethanol, propanol, iso-propanol and butanol (Rodrigues et al., 2008). Methanol is used widely because it is relatively cheaper than other alcohols and has chemical and physical advantages over other alcohols (Ma and Marcus, 1999). Butanol may also be obtained from biological materials (Qureshi et al., 2008), thus yielding completely bio-based biodiesel as well as Methanol, propanol and iso-propanol which are normally produced from petrochemical materials such as methane obtained from natural gas.
This material content is developed to serve as a GUIDE for students to conduct academic research
PRODUCTION AND CHARACTERIZATION OF BIODIESEL FROM LUFFA CYLINDRICA SEED OIL>
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