Resultaten en bevindingen van project
Enzymatic glycerol-free biodiesel production
Dit rapport is onderdeel van de projectencatalogus energie-innovatie. Tussen 2005 en 2011 kregen ruim 1000 innovatieve onderzoeks- en praktijkprojecten subsidie. Ze delen hun resultaten en bevindingen, ter inspiratie voor nieuwe onderzoeks- en productideeën. De subsidies werden verleend door de energie-innovatieprogramma's Energie Onderzoek Subsidie (EOS) en Innovatie Agenda Energie (IAE).
Datum Juli 2010 Status Definitief Technische Universiteit Eindhoven e.a. in opdracht van Agentschap NL
Resultaten en bevindingen van project
Enzymatic glycerol-free biodiesel production
Dit rapport is onderdeel van de projectencatalogus energie-innovatie. Tussen 2005 en 2011 kregen ruim 1000 innovatieve onderzoeks- en praktijkprojecten subsidie. Ze delen hun resultaten en bevindingen, ter inspiratie voor nieuwe onderzoeks- en productideeën. De subsidies werden verleend door de energie-innovatieprogramma's Energie Onderzoek Subsidie (EOS) en Innovatie Agenda Energie (IAE).
Datum Juli 2010 Status Definitief Technische Universiteit Eindhoven e.a. in opdracht van Agentschap NL
Colofon
Projectnaam Enzymatic glycerol-free biodiesel production Programma Energie Onderzoek Subsidie Regeling Nieuw Energie Onderzoek Projectnummer NEOT05008 Contactpersoon Technische Universiteit Eindhoven Hoewel dit rapport met de grootst mogelijke zorg is samengesteld kan Agentschap NL geen enkele aansprakelijkheid aanvaarden voor eventuele fouten.
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NEOT05008 external.doc
Responsibility
Title Enzymatic glycerol-free biodiesel production
Commissioner SenterNovem
Project number NEOT05008
Document NEOT05008 external.doc
Author(s) Dr.ir. J.M.N. van Kasteren, Q Zhou (TU/e)
Ir. A. Hoogendoorn, Ir. T. Adriaans (Ingenia)
Number of pages 9
Date 01 July 2010
Dit project werd uitgevoerd met subsidie van het Ministerie van Economische Zaken; Besluit Energie
Onderzoek Subsidie: Lange Termijn (NEO): Projectnummer NEOT05008
This project was executed with a grant from the Dutch Ministry of Economic Affairs; Besluit Energie
Onderzoek Subsidie: Lange Termijn (NEO): Projectnumber NEOT05008
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1 Enzymatic glycerol-free biodiesel production ............................................................. 5
2 General information about enzymatic biodiesel production ........................................ 6
3 Results .......................................................................................................................... 8
4 Recommendations ........................................................................................................ 9
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Abstract
Enzymatic biodiesel production out of vegetable oil is shown to be technically feasible. Enzymes can be used
instead of NaOH or KOH in order to produce biodiesel which consists of 100 wt-% methyl- or ethylesters.
In this report, also another pathway is proposed where a biodiesel which consists of 75-85 wt-% methylesters
(and the remainder being glycerides) is produced while still maintaining a good viscosity between 5-7 mm2/s.
This new biodiesel fuel does exhibit the following characteristics:
• 15-25% less methanol consumption;
• 24-38% less glycerin production;
• 2,5-4 wt-% more biodiesel produced from the same feedstock amount;
• Higher biodiesel plant efficiency due to mild process conditions.
To make the process sustainable the input should be waste oil.
This process is a very promising method to produce biodiesel. Besides the use of waste oils as input also fuel
properties like density, viscosity, calorific value and iodine value of the produced biodiesel should be
investigated for characterization.
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1 Enzymatic glycerol-free biodiesel production
The aim is to obtain, in one step, alkylesters combined with glycerides which can function as a new biodiesel
mixture preventing the formation of glycerin. In this process triglycerides are split to a glyceride and
methylesters under addition of a specific enzyme and alcohol according to the following reaction scheme:
Triglyceride + alcohol � glycerides + methylesters
The advantages of this new process are:
• A more simple and more energy efficient biodiesel production process
• Reduced feedstock quality requirements e.g. waste streams can be used
• No or lower amounts of glycerin are formed that would be difficult to sell
• The enzymatic catalysis requires mild reaction conditions
• About 33% less alcohol is required
• Less catalyst is needed, leading also to less contamination (salts) in the produced biodiesel
The disadvantages of this process seem the relative slow reaction and the high costs of the enzymes. Reuse of the
enzyme is crucial for the feasibility of the process.
Literature review as described in NEOH01010 (Van Kasteren et al., 2008) concludes that enzymatic
transesterification of vegetable oil with alcohols can thus produce a mixture of alkylesters and glycerides which
looks promising as a new type of glycerine free biodiesel. Glycerine is incorporated into the biodiesel mixture
preventing the formation of a glycerine rich waste stream and improving the energy efficiency of the biodiesel
production. Immobilization of the enzyme makes this process become more technical and economical feasible
because reuse of the enzymatic catalyst is essential for this process.
This report focuses on experiments with enzymes which are capable of producing glycerides from vegetables
oils via transesterification with alcohols.
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2 General information about enzymatic biodiesel production
In recent years using biocatalysts to synthesize biodiesel by alcoholysis of triglycerides and short chain alcohol
under mild conditions has attracted considerable attention. The main difference between the chemical and
enzymatic way to produce biodiesel is replacing the chemical catalyst by an enzymatic one. Enzymatic
approaches serve as a promising technology for biodiesel production compared with chemical methods.
Enzymatic biodiesel production has the following advantages:
• Not sensitive to lower oil qualities (FFA and water content)
• Much purer glycerine not spoiled by catalyst
• Operation at lower temperatures / better energy balance
• Much lower glycerine purification costs
• Lower biodiesel purification costs
Fats containing triacylglycerols and free fatty acid can be enzymatically converted to biodiesel in a one step
process because lipases catalyze both transesterification and esterification reactions (Antczak et al., 2008):
Parameters affecting the yield of enzymatic biodiesel production are: Type of lipase, immobilization, substrates,
molar ratio of substrates, solvent system, temperature, amount of water, glycerine concentration. The selection of
a lipase is based on its properties and reaction sought. The literature survey shows several types of lipases used
for biodiesel production. Economy is of the essence in the industrial applications so it is important to reuse the
enzyme. If the enzyme is immobilized it is possible to recover it after the reaction and use for continuous
processes. The most utilized acyl acceptor for biodiesel production is methanol. Methanol is cheaper than
ethanol. Ethanol is preferred because it is considered more renewable than methanol and hence more eco
friendly. And also it is known that methanol has an inhibitor effect on the lipase. Solutions for this have been
investigated e.g. stepwise addition of methanol or using a solvent. Other acyl acceptors for the enzymatic
biodiesel production are propanol, isopropanol, butanol, branched-chain alcohols, t-butanol and octanol. In
general, different lipases show different requirements of substrate amount for an optimal biocatalysis. Lipase
reactions are reversible. The molar excess of alcohol over fatty acids always increases the yield but it can also
deactivate the enzyme. Using a solvent in enzymatic biodiesel reaction ensures good solubility of substrates and
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increase enzymatic activity. Organic solvents are used in order to increase reaction rate through improved
solubility of alcohol. In that way organic solvent prevents alcohol to surround the lipase and inactivate it.
Synthesis of biodiesel was carried out in numerous organic solvents and yields of this process usually depended
on lipase preparation and composition of fat.
Optimum temperature for enzymatic biodiesel production depends on reaction rate, enzyme inactivation and
molar ratio of substrates. Increasing the temperature also increases the reaction rate but enzymes are very
sensitive to high temperatures and high temperatures inhibit their protein structure and cause enzyme
inactivation. Protection of the water surrounding the lipases is important for optimal conformation of enzyme.
Water is needed for the expression of enzyme activity. Optimal water activity for the enzymatic
transesterification reaction system is specific for lipase types. The key factor on deciding on the water activity is
if the enzyme is already stabilized in its active conformation or water is needed to stabilize the enzyme. However
large water contents favor oil hydrolysis, rather than transesterification and may destroy the microenvironment
of the enzyme resulting in decreased enzyme activity and stability. Many researchers agree that glycerine has an
inactivation affect on enzymes. Glycerine molecules were adsorbed on the surface of the enzyme and make it
inaccessible to hydrophobic substrates. Addition of another hydrophilic substance like acetone or silica gel to the
reaction mixture, partially remove glycerine from the lipase environment through adsorbing it on. A lot of
studies on biodiesel production with lipases have been investigated but did not lead to a commercial scale, main
reasons being the need for large amount of enzymes, its bad reusability and its low reaction efficiency.
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3 Results
Research on the enzymatic transesterification process for biodiesel production is still in an early developmental
stage, as this is still a relatively new field of study. The literature review shows that there is general consensus in
the studies that the enzymatic production of biodiesel is a superior method as compared to conventional chemical
transesterification, considering the lower complexity of the reaction process and the absence of waste products,
in particular soap (produced due to presence of free fatty acids in the waste oil), which will create environmental
problems if disposal is not handled appropriately.
Although enzymatic approaches have become more attractive, they have not been realized in the commercial
production of biodiesel due to the relatively high price of lipases and their short operational life caused by
negative effects of excess alcohol and by-product glycerin. It has been demonstrated that the immobilized lipases
are easily inactivated by contacting with insoluble alcohols existing as drops in the oils. Also the by-product
glycerin has negative effects on the enzymatic biodiesel production as it is hydrophilic and insoluble in the oil
and therefore easily adsorbed onto the surface of the immobilized lipase leading to negative effect on lipase
activity and operational stability. Several methods have been proposed to eliminate the negative effect caused by
glycerin. Experimental results prove that these problems can be overcome. So, the further development of the
enzymatic process for biodiesel production look promising in order to come to a cost effective and efficient
alternative option in the production of biodiesel.
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4 Recommendations
While this research yielded positive and promising experimental results, still a huge effort is needed towards the
use of waste oils and f.i. waste animal fats as feedstock and the understanding of enzyme deactivation and the
optimisation of enzyme regeneration and recycling.
The authors think that it is worthwhile to aim effort at the development of enzymatic biodiesel production
especially while using waste oils as feedstock.
It is also recommended that more research is needed into the combustion behaviour and impact of additives for
this new kind of biodiesel. The authors also think that research is needed towards diesel engine behaviour,
quality standard development for alternative biodiesel and the impact of waste streams on product and process
steps.