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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ENZYMATIC GLYCEROL-FREE

BIODIESEL PRODUCTION

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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

TU/e

Postbus 513 5600 MB Eindhoven | Den Dolech 2 | Eindhoven | The Netherlands

T + 31-(0)40-2475481| F + 31-(0)40-2439475| E j.m.n.v.kasteren@tue.nl | I www.tue.nl

TU/e and Ingenia © 2010

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or any means, electronic, mechanical, photocopying, recording,

scanning or otherwise, except as with the written permission of Tue and Ingenia. This publication has been composed to provide accurate and authoritative information in

regard to the subject matter. However TU/e and Ingenia are not liable for any direct, indirect, incidental or consequential damage, caused by the use or application of the

information of or data from this publication, or the impossibility to use or apply this information and/or these data. Ingenia is a legally protected and registered trademark of

Ingenia (Bureau Benelux des Marques dep.nr. 100.09.58) .

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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.