http://www.biodieselmagazine.com/articles/127509/enzyme-catalyzed-biodiesel-made-from-low-quality-oils
[image in on-line article]
By P.M. Nielsen | July 15, 2014
Enzyme-catalyzed biodiesel made from low-quality oils
In the first quarter of 2014, both Blue Sun Biodiesel in St. Joseph,
Mo., and Viesel Fuel LLC in Stuart, Fla., announced the full-scale
production of biodiesel based on lipase as catalyst. Production at both
sites has been in operation for more than a year now.
Novozymes has been the enzyme supplier and partner, and the
accomplishment of full-scale production is the result of lengthy,
dedicated research and development work. The new lipase technology
enables the processing of oil feedstocks with any concentration of free
fatty acids (FFA) and with lower energy costs than with a standard
chemical catalyst.
Utilizing lipases in the production of biodiesel dates back more than 10
years, and a considerable number of articles suggest the use of
immobilized enzymes (Fjerbaek, L., et al., 2009). The first trials using
liquid formulated lipases instead of immobilized ones took place at
Novozymes’ laboratories in 2006 and resulted in the first patent filings.
In 2008, the Danish National Advanced Technology Foundation supported a
large research effort involving universities and a biodiesel producer.
At the same time, Novozymes began collaboration with Piedmont Biofuels
in Pittsboro, N.C. The objectives of both projects were to find a lipase
with a selling price low enough to compete in the chemical biodiesel
market and to demonstrate the enzymatic biodiesel process in pilot or
production scale. Originally, the collaborators believed that the result
would be a low-cost immobilized lipase, but with time the most efficient
process proved to be one with a new liquid formulated lipase (Cesarini,
S., et al., 2013). The results led to the latest patent filing in 2012,
which describes the basis for the registered BioFAME process utilizing
liquid-formulated lipases as a catalyst and includes the reuse of the
enzyme (Patent WO2012/098114, 2012).
The final enzymatic biodiesel process consists of an enzyme reaction
step followed by polishing as shown in Figure 1.
The operating principle of the enzyme reactor is the creation of an
emulsion with a small amount of water (1 to 2 percent), as the enzyme
works specifically at the interface between oil and water. Constant and
efficient mixing during the reaction is required. One crucial
specification for the oil feedstock was discovered; it must not contain
acidity from mineral acids added upstream. Neutralization of such acids
can be ensured by, for instance, 50 ppm NaOH added as a 10 percent
solution. The reaction temperature must be controlled to 35 degrees
Celsius/95 degrees Fahrenheit, and the methanol added gradually to
prevent enzyme inactivation.
Typically, the required methanol is added during the first six to 10
hours of reaction. An efficient enzyme dosage of 0.7 percent is
suggested, and with the reuse option the enzyme consumption will be
close to 0.2 percent w/w on oil. It is only in the first batch that the
addition of water is required. During additional batches the water from
the reused heavy phase and the wet methanol is normally sufficient.
Figure 1 shows the reactor in connection with centrifuges to separate
the fatty acid methyl esters (FAME) and glycerin after the reaction.
Alternatively, gravity settling in the reactor can be used, but it
requires a relatively long time to produce clear glycerin. In either
case, a small loss of enzyme activity occurs in every batch. The
methanol/ temperature conditions cause a slight inactivation of the
enzyme, and there is a physical loss of enzyme in the separation step.
Experience can ensure that the overall enzyme activity loss is limited
to less than 15 percent per batch.
Use of the liquid lipases was a breakthrough, as they are much cheaper
to produce and provide technological as well as cost benefits.
By using the lipase Novozymes Callera Trans, it is possible to produce
biodiesel from a large variety of oil qualities. The ability to produce
biodiesel from feedstock regardless of its free fatty acid (FFA) content
ultimately makes the process a more cost-efficient way to produce biodiesel.
One of the key technologies involved is the recovery of the enzyme. The
reaction time of 20 to 24 hours is dependent on a certain concentration
of enzyme, for example, 0.7 percent of the oil. To lower associated
costs, the enzyme is collected and reused. After the reaction, the
reaction mixture is separated by gravity/centrifuge into three layers as
illustrated in Figure 2. The glycerin phase after separation is very
different from the glycerin obtained from an alkaline-catalyzed process,
as it is almost free from salt.
The FAME phase from the enzyme reaction typically consists of a
composition with bound glycerin less than 0.22 percent and FFA 2
percent. The FFA content varies, as it is dependent on the FFA content
in the feed. At very high FFA content, such as that found in palm fatty
acid distillate, it can typically reach 2.5 to 3.0 percent FFA. A low
FFA content after the reaction can be achieved by controlling the water
and methanol contents, taking the water formed by the FFA esterification
also into consideration. Data from different oil reactions are included
in Table 1.
TABLE 1. Data from the testing of different oils at typical BioFAME
conditions—two used cooking oils, two corn oils from bioethanol
byproducts, and one PFAD
After BioFAME reaction
Feedstock FFA %, FFA %, Monoglycerides %, Diglycerides %, Triglycerides
%, Bound glycerides %
UCO* 1 6.3 1.6 0.36 0.34
0.30 0.17
UCO 2 8.5 1.4 0.40 0.60
0.13 0.21
Corn oil 1 8.9 1.4 0.46 0.20
0.02 0.15
Corn oil 2 9.1 1.3 0.45 0.28
0.02 0.16
PFAD** 85.0 2.7 0.90 0.30
0.10 0.29
*UCO, used cooking oil;
**PFAD, palm fatty acid distillate
The polishing step is required mainly owing to the FFA content which has
to be reduced to less than 0.25 percent according to ASTM specification.
This can take place as one of several alternative process steps:
1. Caustic wash. The caustic wash is based on the refining concept that
eliminates FFA by a NaOH wash of virgin oil. The residual FFA content in
the FAME phase is relatively low and the formation of soap is limited.
However, the solubility of soap in the FAME is different from its
solubility in oil, and a higher recirculation volume of soap/FAME than
the normal 2.5 times soap volume is required. One benefit of the caustic
wash is the significant reduction in monoglycerides.
2. Resin esterification. Resin technology is used today to eliminate FFA
from oil as a pretreatment to biodiesel production with Na-methoxide
catalyst. The concept is also applicable as a polishing step and uses a
resin catalyzing the esterification at high temperatures (90 C/195 F)
and methanol concentration (15 to 20 percent).
3. Sulfuric acid esterification. The sulfuric acid esterification is
well established as a pretreatment for high-FFA feedstocks, for example,
animal fat. There are limitations to the level of FFA that can be
esterified, and the equipment has to be glass lined to prevent excessive
corrosion. As the BioFAME reaction delivers FFA at a typical 2 percent,
the sulfuric acid process might be able to reach in-specification FFA
levels in one step.
4. Enzymatic esterification. Technically, this is probably the most
advantageous of the processes mentioned. Aside from the FFA
esterification, it also ensures the transesterification of the remaining
glycerides. The cost of the enzyme needs to be considered in this case.
Distillation of the final product is an option to secure against any
carryover from low -quality oils, for example, to ensure that waxes or
metal ions are not found in the final biodiesel. An improved color and
cold soak quality can also be secured by distillation.
Novozymes is currently finalizing the development work of the enzymatic
biodiesel application and is ready to officially launch the concept
later this year. Together with our partners who are using the lipase
Callera Trans in full-scale production, we have shown that biodiesel can
be produced from oils having different low qualities independent of FFA
content and having a low cost for methanol recovery. The process has
been installed at two full-scale plants, one as a retrofitted process to
a traditional plant and the other as a greenfield plant. This is the
first step into the biodiesel industry, but future perspectives for
enzymatic processes are already foreseen, such as combined degumming and
transesterification and sterylglycoside acylation.
Author: P.M. Nielsen
Senior Science Manager, Novozymes R&D Group-Bioenergy Opportunities
p...@novozymes.com
This article originally appeared in the July/August 2014 issue of Inform
magazine. It has been reprinted in Biodiesel Magazine with permission
from AOCS (www.aocs.org).
Works cited
-Cesarini, S., P. Diaz, and P.M. Nielsen, Exploring a new, soluble
lipase for FAMEs production in water-containing systems using crude
soybean oil as a feedstock, Process Biochem. 48:484–487, 2013.
-Fjerbaek, L., K.V. Christensen, and B. Norddahl, A review of the
current state of biodiesel production using enzymatic
transesterification, Biotechnol. Bioeng. 102:1298– 1315, 2009.
-Nielsen, P.M., Production of fatty acid alkyl esters, World
Intellectual Property Organization Patent WO2012/098114, 2012.
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