Executive Summary

The ENERFISH project aims to plan and demonstrate a new poly-generation application with
renewable energy sources at the fishery industry. The distributed energy system utilizes
cleaning waste of a fish processing plant to produce biodiesel. The biodiesel is used to
produce electricity and further locally needed cooling/freezing and heating energy. The
project is financed mainly by EU-TREN, and it belongs to FP7-research programme.
The research contribution focuses on optimisation, simulation, validation and planning of
piloted concepts. An energy integration auditing and optimisation tools will be developed to
carry out feasibility studies for the fishery industry. The advanced CO2 based
freezing/cooling system requires optimization and control system planning of special highpressure equipments. The final biodiesel will be tested in appropriate engines.
The demonstration will take place in Vietnam. In the demonstration case, the main product of
the fish processing plant is catfish filet. The fish cleaning waste of 80 ton amount and the fat
content of 22 per cent results in a production of biodiesel of about 13 t/d in the demonstration
processor.
This report D1 “Optimization of energy systems in an integrated fish-processing plant”
focuses on the following results obtained in WP 1 “Overall optimization and dimensioning of
integrated energy system”:
• Description of an initial system
• Integration energy related process subsystems in close co-operation
• Optimization the integrated energy system, with respect to size, type of
technology, energy flows, material flows etc.
VTT coordinates WP1, and VTT is the main contributor of this report. The work in WP has
been enabled by contribution of all the Enerfish partners and also results in the other WPs has
been utilised in WP1.
The demonstration plant and test runs give more information for economical calculations and
thus the results in D1 report will be checked and updated later during the project.
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Summary
Fish farming and processing plants in Vietnam produce frozen fish fillet with capacity from
some tonnes per day to dozens tonnes/day. One third of fresh fish is yielded as fillet and the
rest of fish is treated as fish cleaning wastes. There are some alternatives for utilisation of fish
cleaning wastes, one of them is biodiesel and energy production at own factory.
The energy demand at the fish processing factory is dominated by cooling and freezing
facilities. 80 % of electricity consumed at the factory is supplied for cooling/freezing
compressors, and the cold energy of low temperatures is needed in freezing and cold storage
facilities of fillet. Cooling energy of about zero degrees is needed for space cooling of
production halls. The specific electricity consumption is about 400 kWh per tonne fresh fish,
or 1400 kWh per tonne fish fillet. The electricity load is typically very steady over a day and a
year in the Vietnamese conditions.
From the energy viewpoint the fish processing plant is energy self-sufficient, when the fish
waste oil is processed in a biodiesel processor and further converted to electricity. In addition
to this, a part of biodiesel can be sold to the fuel market. The fish processing factory
producing fish fillet of 40 ton/day consumes electricity average at a power of 2 MW. 11
ton/day biodiesel is needed for that power production and a surplus biodiesel of 2 ton/day is
available for fuel market. At the same time, diesel engine plant generates heat energy at a
capacity of 2,6 MW, which is also available. The other end in possibilities of poly-generation
is to generate all biodiesel, 13 ton/day, to the fuel market.
In Vietnam, electricity and diesel fuel prices are very low being for electricity average 42,6
€/MWh for industry customers, and diesel fuel costs 400 €/ton. This results in shutdown of
private electricity production (except during electricity blackout), even if cogeneration heat
could be utilized. And the markets for biodiesel should be found outside Vietnam.
According to the calculations and assumptions presented in this report, biodiesel production
from fish cleaning wastes is profitable, and the payback period of the investment seems to be
very short. However, more information on the technical and economical performances related
to the operation and equipments are needed.
Energy balances in a cold store of fish products depend on heat insulation of the building and
very much also on air leakage and air ventilation of the cold space. Warm and moist air
results in a load which is higher than the heat transfer flow through the walls and roof. Some
measures to avoid excess air change are beneficial to be realised.
If the cold energy supply breaks due to the electricity blackout or other technical failure, the
storage with 920 ton of frozen fish reaches the temperature of 0 °C in 52 and 319 hours, if the
air leakage and ventilation is zero and 1 kg/s respectively. However, the indoor temperature
rises from -22 °C to -15 °C in about 2 hours assuming air leakage of 1 kg/s.
Heat capacity of a cold store gives some possibilities that can be utilised economically in
normal operation and in failure situations, e.g. in the case of time tariff, electricity load can be
shifted to low price hours, electricity peak load can be restricted, and reserve capacity of
diesel engine plants can be lowered.
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Contents
Executive Summary ………………………………………………………………………………………………. 4
Summary ……………………………………………………………………………………………………………… 5
1 Introduction…………………………………………………………………………………………………… 7
2 Description of the fish processing plant…………………………………………………………….. 8
2.1 Main activities and dimensions at fishery industry………………………………………….. 8
2.2 Energy systems……………………………………………………………………………………….. 11
3 Integration of energy systems and utilisation of fish cleaning wastes …..
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1 Introduction
Utilisation of distributed energy resources for energy and fuel production is highly promoted
in European Union and in many other parts of the world. This tendency is driven by several
things, e.g. environmental and security issues of the energy systems, diminishing fossil
reserves, renewable sources available, weaknesses in the national distribution networks, and
geopolitical pressures. Fish oil from fish cleaning wastes is estimated to be a promising
source for locally produced energy and fuel. Fish farming and fish processing are widely
distributed business taking place in every continent, but especially in SE-Asia. Respectively
energy and fuel poly-generation using fish cleaning wastes could take place in the same areas.
The target country for building up the demonstration plant in Enerfish project is Vietnam, and
also the feasibility study is made in the conditions of Vietnam. However, the poly-generation
of energy and fuel based on fish cleaning wastes enables bio-fuel trade over country borders,
whereas the electricity and heat energies are more national and local products and their
profitability depends on the local conditions. The optimisation tools prepared in Enerfish
project are aimed to be for common cases, and only the values of parameters and variables are
dependent on the local conditions.
The common calculation case of the waste to energy – configuration contains equipments for
fish oil extraction/animal feedstock preparation plant, biodiesel processor, and diesel engine
plant with co-generation facilities. The optimisation procedure finds the most economical
combination for poly-generation. This basic poly-generation alternative can be compared with
the initial system, i.e. fish cleaning wastes are sold to another company, or with any other
thinkable solution. The scope of calculation has to include also energy consumption of the
fish processing factory and alternative energy supply systems, especially the electricity supply
from nation electricity grid.
The biodiesel production needs energy and also some chemicals, which have an effect on the
total costs of poly-generation. The uncertainty in the amount and price of these chemicals and
in performance of the equipments result in only preliminary conclusions. An updating of the
calculations is needed after additional information from demonstration runs. Also the
assessment of investments is not included in this report, only operational costs and incomes at
this moment.
In the study related to the freezing/cooling system using CO2 circles, the calculations are
focused on general process values, on demand for cold energy in a store, and on dynamic
behaviour of a cold store. These studies are waited to give many ideas for energy saves and
energy management at the fish processing factory.
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2 Description of the fish processing plant
2.1 Main activities and dimensions at fishery industry
The scale of fish farming and fish processing varies very much in the target country of
Enerfish project. According to the information of International Vietfish fair in 2009 (1) the
largest fishery companies in Vietnam have a capacity of 200 ton fish fillet per day. In these
cases the factories are located in different areas in Vietnam. Normally fishery companies have
a factory area with necessary facilities and a capacity of 10 – 50 ton per day. The number of
fish producer and exporter companies is about 150 in Vietnam (2).
The target fishery company presents a situation, where the whole chain from fish farming to
fillet cold storing is integrated to a functional factory and the facilities are located at the same
area. Fig. 1 shows the units including in the factory: Fish farming and fish food production
facilities are located on a side of a river and fish processing on the opposite side of the river.
The main part of fish food feedstock comes from the rice factory owned also the company.
Fish processing, freezing and cold storing compose a functional and logistical entity. The
main product, frozen pangasius, is exported to Asian and European countries. Fish cleaning
wastes are sold to another company.
Reservoir,
Fish
Breeding
Fileting
Freezing/
Cold store
Fish food factory
production
Waste
water
treatment
Fish
nursery
Rice
factory
Fish waste for utilisation
Fish filet products
rice products
Input for fish food production (husks etc)
Soy, etc.
River
Baby
fish
Any other waste
waste water
waste water sludge
Fish feed
HT Food
Thot Not factories
Reservoir,
Fish
Breeding
Fileting
Freezing/
Cold store
Fish food factory
production
Waste
water
treatment
Fish
nursery
Rice
factory
Fish waste for utilisation
Fish filet products
rice products
Input for fish food production (husks etc)
Soy, etc.
River
Baby
fish
Any other waste
waste water
waste water sludge
Fish feed
HT Food
Thot Not factories
Figure 1. Fish farming facilities.
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Fish processing comprises various working phases, presented in Fig. 2 and treated more
detailed below. Most of the phases contain manual labour, which can be seen also in Fig 3
showing a view over filleting hall.
Figure 2. Fish processing scheme.
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Figure 3. Manual labour in fish processing hall.
Receiving fish
The fish, each 0,9-1,2 kg, are transported by fish-containers to the processing factory and
conveyed in bowls using conveyer chain for slaughtering. The fish is alive and fresh during
the transportation process, and are slaughtered just before they are taken for processing. The
fish receiving room is cooled with air cooler units.
Filleting and skinning
The fishes are then washed after slaughtering. The filleting process is done manually by
knives. Next the fillets are washed and the skin is removed in the skin remover machine.
Process room is cooled with air cooler fan units
Trimming and checking
The fillet and skinned fishes are trimmed. All the skins are removed and all the remaining
fatty areas will be trimmed off. The trimming work is also done manually. Next the trimmed
fishes pass through the quality check. After this process, the passed fillets are washed once
again and wait for the next processing phase.
Sizing
Special parameters determine the size of the fillets and they are sorted into the corresponding
boxes waiting for the next processing phase. The customers decide the size and condition of
the fish they purchase.
Freezing
Before weighing and packing, the fillets have to pass through the block or IQF-freezer
(Individual Quick Frozen). The fish are either frozen or frozen and glazed according to the
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demands of individual customers and products. Glazing is the name of the process where
frozen fish is dipped into glazing water so that the ice solution builds up a good glaze.
Weighing and packaging
After freezing and glazing the fish products are transferred for weighing. The weighed fish are
packed into plastic bags. The bags are vacuum sealed. Next the bags are packed into carton
boxes, shifted through the metal detector to avoid possible foreign metal pieces. Finally the
boxes are loaded onto the ballets.
Storing
The pallets are moved to the freezing store waiting for transportation. The end product is
transported by insulated and cooled trucks to the customers.
2.2 Energy systems
Based on the energy audit at the target fish processing factory of the project, the energy
consumption calculated per live fish input is 414 kWh/ton, and the energy source is
electricity. The amount of 3,6 litre oil per ton input has been used in diesel generators to
produce electricity during the electricity supply shortages. If energy consumption is allocated
to the fillet, the energy intensity is 1380 kWh per ton fillet. The demand of electricity is quit
stabile over a day and over a year while due to the three-shift work and short annual breaks.
Fig. 4 shows the use of electricity in different sectors. The main consumption takes place in
freezing systems, 336 kWh/ton input or 1120 kWh/ton fillet product. In the table 1, the
percentage distribution of electricity consumption has been presented. 80 % of electricity is
needed for cooling/freezing compressors. Devices related to fish treatment take about 10 % of
the electricity. The lighting system uses energy saving lamps and causes only 3 per cent share
in electricity consumption.
In air conditioning systems, fan units are located in suitable positions all over the fishery
halls. Compressors use NH3 as a coolant. Also in freezing system the coolant is NH3. Heat
relieving agent in cooling towers (evaporation condensers) is water.
According to the energy audit energy saving possibilities can be found in storage systems,
e.g.: Loading area should be closed and air conditioned all the time to minimize warm and
humid air flow in to the store when opening the freezing store door. Freezing store loading
door should be electrically operated and well sealed. In the freezing store, the air cooler units
should be defrosted regularly.
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Figure 4. Energy characteristic use at fish processing factory allocated to the fish intake.
Table 1. Distribution of electricity use at fish processing factory.
Fish processing 9,6 %
Compressors 80 %
Air conditioning 5,4 %
Heat supply system (boiler) 0 %
Lighting 3 %
Other 2 %
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3 Integration of energy systems and utilisation of fish
cleaning wastes
3.1 Energy loops
The cleaning wastes of pangasius fish contain fat about 22 percent. This fish waste oil can be
extracted from the rest wastes and led to energy utilisation. Biodiesel processor produces fuel
from fish oil. Assuming that the capacity of the processor is 13 ton biodiesel per day, as
shown also in Fig. 5, the amount of fish oil input is about 17 ton/day, and further, the amount
of fish cleaning wastes for energy system is about 80 ton/day. This amount of cleaning wastes
is produced if fish fillet production is 40 ton/day and live fish intake about 120 ton/day.
In addition to the biodiesel processor also other demonstration facilities of Enerfish project
are presented (red colour) in Fig 5. A part of biodiesel is used in generator set producing
electricity with capacity of 1,1 MW and possible heat energy of 1,3 MW. The rest of
biodiesel, about 7 ton/day can be sold to the fuel market. Electricity network of the fishery
factory is supplied by the diesel generator and the national electricity distribution network. In
principally, electricity produced in generator can be sold to the national network or areal
industrial use.
Freezing compressors are the main consumer of electricity in the fishery factory, and in this
Enerfish demonstration a cold store will be supplied by freezing energy from cascade type
compressor system using two-stage circles. The main circle is working with NH3 coolant and
the distribution circle is working with CO2-fluid/gas. The initial system is based on
conventional NH3 circle containing evaporators, compressors and condensers. The capacity of
cooling/freezing plant of Enerfish project covers only a part of cold energy needed at the
whole factory.
A by-product of biodiesel processor is glycerine, and it can also utilize as energy source in
boiler or biogas plants. Normally it is refined for different kind of purposes, e.g. food
additives. More detailed description of glycerine is presented in D2 report.
In addition to fish oil the biodiesel processor needs also methanol and potassium hydroxide
for the process. Antioxidant is probably needed when storing biodiesel to avoid oxidation
process in fuel. More information on these issues is in D2 and D3 reports.
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Biodiesel
process
(1×13 t/day)
(inc.chemical
pretreatment)
120 t fish
processing
(fat content 22 %)
39 t
fillet
Diesel gen-set
1.1 MW(el)
1.3MW(th)
13 t
Biodiesel
CO2
-Freezing/Chilling:
0.3 MW; 6,3 MWh/day
Industrial
network
26 MWh/day
Hot water/Steam
42 t
Remains
81 t
Cleaning
waste
ThermoMechanical
treatment
2 t
Crude Glycerine
17 t
Fish oil
Waste water
treatment
Sewage
Glycerine
Treatment
Useful glycerine product
Mass and Energy
balances are per day
~ 1 MWh/day (60 ºC)
~ 31 MWh/day
Process integration
Main
Compressors
Exchanger
2 t Methanol
0,05 t KOH
3 t water
– normal/+50 ºC
5,5 MWh(e)/day
7 t Biodiesel
to fuel market
Animal
feedstock,
Other use
P/C
110 kV
380 V
Biodiesel
process
(1×13 t/day)
(inc.chemical
pretreatment)
120 t fish
processing
(fat content 22 %)
39 t
fillet
Diesel gen-set
1.1 MW(el)
1.3MW(th)
13 t
Biodiesel
CO2
-Freezing/Chilling:
0.3 MW; 6,3 MWh/day
Industrial
network
26 MWh/day
Hot water/Steam
42 t
Remains
81 t
Cleaning
waste
ThermoMechanical
treatment
2 t
Crude Glycerine
17 t
Fish oil
Waste water
treatment
Sewage
Glycerine
Treatment
Useful glycerine product
Mass and Energy
balances are per day
~ 1 MWh/day (60 ºC)
~ 31 MWh/day
Process integration
Main
Compressors
Exchanger
2 t Methanol
0,05 t KOH
3 t water
– normal/+50 ºC
5,5 MWh(e)/day
7 t Biodiesel
to fuel market
Animal
feedstock,
Other use
P/C
110 kV
380 V
Figure 5. Integration of energy and mass flows at a fish processing factory.
3.2 Alternative use for fish cleaning wastes
From the viewpoint of a fishery factory there are several possibilities to utilize fish cleaning
wastes. Fig. 6 illustrates economical applications: 1) Fish cleaning wastes are sold to other
companies maybe more valuable parts, e.g. heads, separated from the rest parts. 2) Fish
company has facilities for fish waste treatment to separate fist oil from wastes. In this case,
fish oil is a main product, which can be further processed for energy purposes. Also other use
can be found for fish waste oil, but it is not allowed to use for food purposes for example in
EU area. The remains of extraction plant can be processed for animal feedstock based on the
content of protein and trace elements in fish wastes. 3) Biodiesel processor can be established
by the fishery, and fish oil needed as raw material can be produced in own extraction plant or
fish oil can be purchased from other producer. Biodiesel can be sold to fuel market or utilized
in own energy production. 4) In the case of own energy production, a cogeneration plant
enables production of electricity, heating energy and low pressure steam. Heat energy can
reach temperature over 100 C-degree by the heat recovery from flue gas. The produced
energy can further be utilised in cooling/freezing energy production. Electricity in compressor
systems and heat energy in absorption system can be used as energy source for cooling plant.
In freezing energy production, compressor system is typically more economical compared to
absorption system.
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Figure 6. Possible economically feasible application routes of fish-waste.
3.3 Fuel and Energy Poly-generation
There are some basic alternatives to utilise biodiesel locally in energy production or at the fuel
market. Four cases are described below and presented in Fig. 7. An assumption is made that
the amount of fish cleaning wastes available for biodiesel production is 80 ton/day and the
biodiesel production is 13 ton/day, equivalent to 150 MWh/day.
a) Biodiesel is used for electricity production in a diesel engine plant. The output is 57
MWh(e)/day by average power of 2,4 MW. Energy losses are 84 MWh/d and energy
efficiency is 38 %. This kind of local power plant can be built to be independent of the
national grid, but in this case the power system should contain more than one unit in order to
meet the reliable criterion.
b) In addition to power production, the main part of heat losses are utilised for useful
purposes. A total efficiency of 89 % can be reached and 77 MWh/day by heat flow of 3,2
MW is produced. The sources for heat energy are heat from cooling of lubricating oil and
engine and from exhaust gases. The appendix A (5) shows a principal equipment scheme for
the heat recovery.
c) In this configuration, electricity production is assumed to cover the whole consumption of
electricity at a fish processing plant utilising 120 ton/day live fish in input and freezing and
storing fish fillet of amount of 40 ton/day. About 48 MWh/day at average power of 2 MW is
produced by diesel engine plant. Thermal energy of 64 MWh/day is also available. 11 ton
Cleaning Wastes
Fish Treatment
Cooling
Fillet Freezing
Cold Storage
Fish
waste oil
Biodiesel
Energy
Production
Electricity
Heating energy
Cooling energy
Local, National
Local
Local
Local
Europe
USA
ASIA
Neighboring
countries
Local
Biofuel
Fish waste oil
Fish powder
Other parts
OUTPUTS MARKET
Cleaning Wastes
Fish Treatment
Cooling
Fillet Freezing
Cold Storage
Biodiesel
Energy
Production
Heating energy
Cooling energy
Local
Local
OUTPUTS MARKET
Fish Cleaning
Wastes
Fish oil
separation
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biodiesel is used for the power plant, and the amount of 2 ton is daily for sale to the fuel
market. This energy configuration can be used without connection to the national grid.
d) The whole amount of biodiesel, 13 ton/day, from biodiesel processor is sold to fuel market.
The diesel engine plant is maybe as stand-by stage for blackouts in the electric network.
150 MWh/day
biodiesel
Electricity
2,4 MW
80 ton /day
fish cleaning
wastes
17 ton/day
fish oil
Biodiesel
processor:
13 ton/day
biodiesel
Gen-set:
Average fuel
capacity:
6,3 MW Heat
losses
3,9 MW
57
MWh/day
150 MWh/day
biodiesel
Electricity
2,4 MW
80 ton /day
fish cleaning
wastes
17 ton/day
fish oil
Biodiesel
processor:
13 ton/day
biodiesel
Gen-set:
Average fuel
capacity:
6,3 MW
57
MWh/day
Heat energy
3,2 MW
Heat losses 0,7 MW, 17 MWh
77
MWh/day
Electricity
2 MW
80 ton /day
fish cleaning
wastes
17 ton/day
fish oil
Biodiesel
processor:
13 ton/day
biodiesel
Gen-set:
Power
capacity:
2 MW
48
MWh/day
Heat energy
2,67 MW
Heat losses 0,56 MW
64
MWh/day
126
MWh/day
biodiesel
Biodiesel to market Heat losses 0,6 MW, 14 MWh
2 ton/day
Electricity
– MW
80 ton /day
fish cleaning
wastes
17 ton/day
fish oil
Biodiesel
processor:
13 ton/day
biodiesel
Gen-set:
Power
capacity:
– MW

MWh/day
Heat energy
– MW
Heat losses 0,56 MW

MW
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is assumed to run at full power. The right scale shows electricity and total energy production,
and the left scale shows biodiesel amount available for fuel market. The minimum rate for
power generator is assumed to be 0,5 MW.
Energy balances in polygeneration
Fuel to market
Power production
Co-gen capacity
0
2
4
6
8
10
12
14
0 0,4 0,8 1,2 1,6 2 2,4
Power rate, MW
Biodiesel fuel, ton/day
0
1
2
3
4
5
6
7
Energy production, MW
Heat available
Energy balances in polygeneration
Fuel to market
Power production
Co-gen capacity
0
2
4
6
8
10
12
14
0 0,4 0,8 1,2 1,6 2 2,4
Power rate, MW
Biodiesel fuel, ton/day
0
1
2
3
4
5
6
7
Energy production, MW
Heat available
Energy balances in polygeneration
Fuel to market
Power production
Co-gen capacity
0
2
4
6
8
10
12
14
0 0,4 0,8 1,2 1,6 2 2,4
Power rate, MW
Biodiesel fuel, ton/day
0
1
2
3
4
5
6
7
Energy production, MW
Heat available
Figure 8. Energy and fuel balances in alternative solutions of poly-generation.
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4 Conditions for poly-generation
4.1 Market situation of electricity and heat
Economical production of electricity is depending aside the own energy system of the
company on the electricity price supplied from the national distribution network. In Vietnam,
industry customers can purchase electricity based on energy tariff, normally on daily three
time tariff of high, basic and low price hours. In the Enerfish case, the average total price for
electricity from grid is 42,6 €/MWh. Thus the price level is rather low compared for example
to Finland, where the total price including electrical energy, distribution and taxes for industry
customers of a comparable scale is about 100 €/MWh. The price level in Finland belongs to
the lowest in Europe. But, an abnormal price situation with low energy prices occurs during
the economical recession in 2009.
Another feature in the power system in Vietnam is supply breaks lasting for some seconds
and minutes to hours. Typically the end-users are provided with own reserve capacity,
normally with diesel engine plants.
Heat energy is more local product, and the end-user should be located within distance of some
kilometres. Alternative sources to produce heat energy in Vietnam are electricity, heating oil
and coal, partly also natural gas.
4.2 Market situation of biodiesel
World energy and fuel demand is expected to rise significantly over the next few decades
despite some bending down in recession years 2008/2009. Most of this increase in energy
demand is expected to come from Asia.
While reserves of fossil fuels are thought to be sufficient until at least 2030, the price of fossil
fuels is expected to grow steadily over the coming decades driven by increasing resource
scarcity. The price of oil is on an upward trend – driven by increased demand, diminishing
reserves, increasing costs of extraction, geopolitical pressure and environmental concerns.
Fig. 9 shows how the cost of crude oil has varied during the last decades (3). A steady
increase over the last 10 years period can be noted. The lower level of price following the
peak price in 2008 seems to be a temporary stage, and the growing price trend is reached in
2009. It is also expected to continue.
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Figure 9. Crude oil price (3).
The price curve of diesel fuel shown in Fig. 10 (4) seems to follow the development of crude
oil price. A quite steady rising trend took place in year 2005-2008. Then there is a peak price
period of over 1400 USD/ton in 2008 followed by low prices in 2009 only 500 – 600
USD/ton. However, some differences between the price development of crude oil and diesel
oil can be seen, Fig. 11. The price of biodiesel has been about twenty USD per barrel higher
than crude oil before the price peak period, when the difference was even 50 USD. During the
recession year 2009 diesel price was only 10 USD per barrel higher than crude oil.
Normalisation of the world economy can be expected to lead growing prices of diesel oil.
This means that the diesel price of 1000-1200 USD per ton can be reached in two years.
Figure 10. Diesel fuel price (4).
Figure 11. Price difference between diesel fuel and crude oil, also petrol case is shown (4).
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Formation of biodiesel and other bio-fuel market is based mainly on the concern of energy
security and environment and carbon dioxide emissions. These concerns cause a growing
requirement for governments to change the energy mix, and to utilise renewable energy
sources. Despite the regulatory actions, the price of biodiesel follows the price of mineral
based diesel oil.
Biodiesel can be used in modern diesel engines with little or no modification, and can be
mixed with mineral diesel in any percentage. In many European countries, 5% biodiesel blend
is widely used and is available at thousands of fuel stations, although in some countries –
notably Brazil – some stations sell 100% biodiesel. The EU is currently the largest consumer
of biodiesel.
Vietnam has own oil sources and it is a net exporter of oil. At the same time Vietnam also
imports oil products. The price level of diesel fuel at refuelling station is about 10 000 VND
per litre, which means about 425 Euros per tonne.
5 Operational Optimization of poly-generation
5.1 Model Description
The purpose of creating an optimization model for fish oil based bio diesel process is to
describe in a simple way cost-minimized operation of the production chain in order to e.g.
perform sensitivity analysis of technical and economical parameters. Material flow chart of
the optimization model is illustrated in
Figure 12. The three separate process phases are fish oil extraction, bio diesel production and
production of electricity and heat by diesel engines. In order to model the entire process
properly but in a simplified manner, linear optimization model is used with some integer
variables. Time frame of the model is hourly operation of one day (t = 1,…,24), and these
operational days are multiplied in order to obtain annual costs and revenues. Furthermore,
these annual values are used in discounted cost analysis of infrastructure investments.
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Fish cleaning
waste
Formid acid
Heat
Sold fish remains Electricity
Fish
waste oil
Fish waste oil
extraction
Methanol
KOH and water
Electricity
Heat
Crude glycerine
Bio diesel
fuel
Bio diesel fuel
production
Bio diesel and
diesel fuel mix
Heat Electricity
Other diesel
power plant
Electricity
CHP diesel
power plant
Sold bio diesel
Figure 12. Process flow chart of the fish oil based bio diesel production used in optimization model.
The first phase in the process is extraction of fish waste oil from fish cleaning waste. This
process uses formic acid, heat and electricity and produces dried fish remains as residuals to
be sold. Variables of the optimization model in this process phase are defined as follows:
Cfish(t): consumption of fish cleaning waste
Cacid(t): consumption of formid acid
Premain(t): production of fish remains
Pfishoil(t): production of fish waste oil
Efish(t): consumption of electricity in fish oil extraction
Hfish(t): consumption of heat in fish oil extraction
Rates of consumption and production of materials per produced ton of fish waste oil are based
on the daily parameters of the fish waste oil extraction plant illustrated in Error! Reference
source not found.. Also, costs of materials, sold or purchased, are presented in Table 3.
Table 2. Consumption rates and costs of raw materials in fish waste oil extraction process.
Material Daily rate per ton of fish oil Parameter Cost/Profit Parameter
Fish waste oil 17 ton 1.000 ton
Fish cleaning waste 81 ton 4.765 ton ȕfish 100 €/ton pfish
Sold fish remains 18 ton 1.058 ton Ȝremain 280 €/ton sremain
Formid acid 2 ton 0.118 ton ȕacid 550 €/ton pacid
Heat 4000 kWh 235 kWh șfish
Electricity 700 kWh 41 kWh İfish