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Bio-diesel plant innovation
Biodiesel is an alternative biofuel produced by chemically reacting a vegetable oil oranimal fat with a short-chain alcohol, such as methanol, ethanol, or buthanol and acatalyst (Meher et al., 2006). Biodiesel is obtained from vegetable oils and animal fats
(Marchetti et al., 2007), so it is an important tool for combating environmental degradation because of its ecofriendly nature, liquid nature, and easy portability (Balat,2007; Beer et al., 2002). However, a global debate has now emerged because this fuel is derived primarily from soybean oil or other cereals and using food to produce fuel is notreasonable considering the increase in world population.
In order to solve this problem, industries use waste vegetable oil and grease and animal fats from poultry to produce biodiesel (Nebel and Mittelbach, 2006; Phan and Phan,2008). In addition, researchers are developing certain crops with high oil content just forthe production of biodiesel (Cardone, et al., 2003; Gressel, 2008) or looking for new
sources to produce biodiesel (Kondamudi, et al., 2008).Therefore, it would be very useful to look for new raw sustainable materials for biodiesel production that do not involve the use of cereals. In this work, an innovative biodiesel production from Galician marine algae has been carried out. The use of this raw material can give a solution from an environmental and economic point of view.
Galicia (north eastern Spain) has 35% of the total Spanish coastline. It is a region with an abundance and wide diversity of marine species and has a deeply-rooted seafaring
tradition. Algae in Galicia have been traditionally used for agricultural uses. Coastal
residents have always collected upon arrival at the coast after storms, to use such as
fertilizer, correcting the soil pH, and even as food for livestock. And Galicians have also
used seaweed for their own consumption in times of great famine.
There are a great number of different marine algae but only some species are being used
as a food product. The other species are collected in the beaches and they are treated as
a waste. Then, we have focused the biodiesel production from algae that do not have
any use. In this paper, a brief description on the extraction, transesterification, and
purification process to produce biodiesel from marine alga is reported.
- Materials and Methods
2.1 Materials
Different type of marine algae (Fucus Spiralis, Saccorhiza Polyschides, Sargassum
Muticum, Codium Tomentosum, Ulva Rigida, Enteromorpha Intestinalis, Ascophyllum
Nodosum, Pelvetia Canaliculata) were collected from the Galician beaches, washed
with water and sun-dried for a few days, since water inhibits transesterification. After
that, the dried algae were crush in two steps in order to obtain small solid particles.
Fatty acid methyl esters, anhydrous methanol (ACS grade), sodium hydroxide (98%), nhexane (ACS grade) were supplied by Panreac.
2.2 Oil Extraction
Three hundred mL of n-hexane was used for 40-60 g of dried algae, depending on the
algae type, for the oil extraction. The extraction was carried out in a Soxhlet apparatous
for 4 h according to UNE-EN 734-1 (2006). The extraction was carried out in order to
determine the algae oil content.
All of the experiments were carried out using a 0.5 L round-bottomed glass flask. The
resultant solution was separated from solvent by distillation. The solvent was reused in
the next batch of extraction. Finally, the sample was dried in an oven (100 ºC) until
constant weight.
Transesterification Process
The transesterification process was conducted simultaneously with the extraction in
order to avoid the previous step of oil extraction and purification of obtained oil. Then,
100 g of dry algae was mixed with 300 mL of hexane and introduced in a thermostated
reactor. The mixture was heated at 62 ºC and after that, methanol (10 wt % dry basis) in
which sodium hydroxide (0.1 wt% dry basis) had been previously dissolved was added
to the reactor. Reaction was conducted at the same temperature for four hours with
constant stirring at 110 rpm. The reaction mixture, after the reaction, was cooled to
room temperature. Then, the solid phase was separated by filtration using a Buckner
funnel under vacuum. Finally, the bottom layer of glycerin was separated from the
mixture biodiesel and hexane layer (top layer), which was then washed with water to
remove the methanol excess and the traces of catalyst (Karaosmanoglu et al., 1996;
Lang et al., 2001). In order to obtain the crude biodiesel was necessary to remove the
solvent by distillation. The solvent was reused in the next batch of reaction.
Analysis of fatty acid methyl esters
The linolenic acid methyl ester content was quantified using a gas chromatograph Trace
GC-Ultra connected to an Innowax capillary column (60m x 0.25mm x 0.25µm), from
Agilent Technologies. The temperature program was as follows: 50 ºC for 2 min and
raised to 240 ºC at a rate of 10 ºC/min and maintained for 27 min. The injector was set
up for 240 ºC and the FID detector at 220 ºC. Helium was used as carrier gas, at
constant flow of 1 mL/min.
The analysis was carried out by diluting the biodiesel (diluted to 1 µL by adding 1000
µL of hexane), and 0.5 µL of this solution was injected through the column. Nonanoic
acid methyl ester was used as an internal standard. - Results and Discussion
This work has been divided in two main sections. The first step on this research
consisted of algae characterization in order to determine the best type to carry out the
transesterification process. Once algae were characterized, the reaction was carried out
simultaneously with the oil extraction with the aim of optimizing the process. Algae characterization
Eight types of algae collected from Galician coast were analyzed in order to determine
the oil content using n-hexane to carry out the extraction. It was observed that these
algae do not have a very high oil content (Fig. 1), therefore it will be necessary to use a
great amount of raw material in order to obtain the biodiesel. This could seem an
inconvenient; however only at south of Galicia more than 1500 tonnes/year are
collected from the beaches.
Figure 1. Oil content of the different type of algae: 1 Fucus Spiralis; 2 Saccorhiza
Polyschides; 3 Sargassum Muticum; 4 Codium Tomentosum; 5 Ulva Rigida; 6
Enteromorpha Intestinalis; 7 Ascophyllum Nodosum; 8 Pelvetia Canaliculata.
Considering that most of the types have a lower content, the algae were mixed in order
to obtain a homogeneous value for oil content. Moreover, the algae are mixed when
they are collected from the beaches. Three different mixtures were obtained and their oil
content was also determined by extraction with n-hexane. The oil content of the three
mixtures is showed in table 1.
The composition of algae mixture was the following:
MIX 1: Fucus Spiralis, Sargassum Muticum, Codium Tomentosum, Ulva Rigida,
Ascophyllum Nodosum, Himantalia Elongata.
MIX 2: Fucus Spiralis, Sargassum Muticum, Codium Tomentosum, Ulva Rigida,
Ascophyllum Nodosum, Himantalia Elongata, Cryptopleura Ramosa, Undaria
Pinnatifida, Padina Pavonia.
MIX 3: Enteromorpha Intestinalis, Ulva Rigida.
Table 1. % oil content of the different samples.
SAMPLE % OIL
MIX 1 1.26
MIX 2 0.65
MIX 3 0.31
Transesterification Process
Extraction and transesterification of extracted oil to biodiesel was carried out
simultaneously. In order to check the viability of the simultaneous process, a sample of
algae were undergone to Soxlhet extraction with n-hexane, as described for determining
the oil content of algae, after the completion of reaction and it was observed that the
most algae content had been extracted during the reaction (more than 75%).
Finally, the conversion of oil to biodiesel was determined for each sample. As expected,
the maximum oil to biodiesel transformation was observed in mixture 1 which the most
oil content (Fig. 2). Then, it can be said that the conversion of oil to biodiesel is very
high.
Figure 2. Conversion of oil from algae to biodiesel of the different samples.
Finally, the linolenic acid methyl ester content was determined by gas chromatography.
It was observed a great variation among the samples (Fig. 3), that could be due to the
different type of algae oil. Although all of them have values lower than 12%, in
accordance with the specifications reported in UNE-EN 14214 (2003).
Figure 3. Linolenic acid methyl ester content of biodiesel of the different samples.
In conclusion, it has been demonstrated that marine algae could be used as a source to
produce biodiesel so about 75% of the oil obtained from algae was converted to
biodiesel with more that 90% yield.
