MASTER OF SCIENCE IN MARITIME SCIENCE
MASTER DISSERTATION
Academic year 2017 – 2018
Reducing the emissions of greenhouse gases from ships by using biofuel made
from microalgae
Sander de Nijs
Submitted in partial fulfillment of the requirements for the degree of: Master of Science in Maritime Science
Supervisor: Maxim Candries
Assessor: Marc Vantorre
Table of contents
1. Introduction ........................................................................................................................................... 1
2. Greenhouse gas reduction technologies ............................................................................................... 3
2.1 About greenhouse gases ............................................................................................................... 3
2.1.1 Terminology ........................................................................................................................... 3
2.1.2 Emission sources on ships ..................................................................................................... 4
2.2 Reduction technologies ................................................................................................................. 5
3. Biofuels in shipping ............................................................................................................................... 9
3.1 Marine engines and their fuels ..................................................................................................... 9
3.2 Biofuels: the four generations ..................................................................................................... 10
3.3 Candidates for marine application .............................................................................................. 11
4. Biofuel from algae ............................................................................................................................... 13
4.1 Cultivation ................................................................................................................................... 13
4.1.1 Closed photobioreactor systems ......................................................................................... 14
4.1.2 Open ponds ......................................................................................................................... 14
4.1.3 Suitable areas for cultivation ............................................................................................... 15
4.2 Harvesting.................................................................................................................................... 16
4.3 From algae to biofuel .................................................................................................................. 17
4.4 Challenges and potentials ........................................................................................................... 18
4.4.1 Techno-economic challenges .............................................................................................. 18
4.4.2 Environmental challenges ................................................................................................... 21
4.4.3 Life cycle assessment........................................................................................................... 22
4.4.4 Potentials ............................................................................................................................. 23
5 Fuelling the global shipping fleet ........................................................................................................ 24
5.1 How much is needed? ................................................................................................................. 24
5.2 Algal biofuel producers and projects .......................................................................................... 28
5.2.1 Global algae biofuel industry ............................................................................................... 28
5.2.2 Current and future microalgal production volumes ........................................................... 29
5.2.3 Shipboard projects .............................................................................................................. 30
6 Conclusion ........................................................................................................................................... 31
Bibliography ................................................................................................................................................. 35
List of abbreviations
IMO International Maritime Organization MARPOL International Convention for the Prevention of Pollution From Ships EEDI Energy Efficiency Design Index SEEMP Ship Energy Efficiency Management Plan RPM Revolutions Per Minute LNG Liquified Natural Gas LPG Liquified Petroleum Gas MDO Marine Diesel Oil MGO Marine Gas Oil HFO Heavy Fuel Oil IFO Intermediate Fuel Oil GHG Greenhouse Gas FAME Fatty Acid Methyl Ester SVO Straight Vegetable Oil HVO Hydrotreated Vegetable Oil HTL Hydrothermal Liquefaction PBR Photobioreactor ORP Open Raceway Pond LED Light-Emitting Diode DAF Dissolved Air Flotation SLS Solid Liquid Separation AD Anaerobic Digestion LCA Life Cycle Assessment WTP Well-To-Propeller WTT Well-To-Tank TTP Tank-To-Propeller TEA Techno-Economic Assessment WWT Wastewater Treatment
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1. Introduction
Global warming is a much discussed issue nowadays. To keep the global temperature rise this century well
below 2 degrees Celsius above pre-industrial levels as concluded in the Paris Agreement, the total emission
of greenhouse gases (GHG’s) worldwide has to drop significantly. The third IMO GHG study shows that for
the period 2007–2012, on average, shipping accounted for approximately 3.1% of annual global CO2
emissions and approximately 2.8% of annual GHG emissions on a CO2 equivalent basis (Smith et al., 2014).
This study also showed that the projected rise in demand for maritime transport is the main driver of
emissions increase and that this increase is projected to be 50%–250% in the period up to 2050 if no
measures are taken by the shipping industry.
The IMO adopted in 2011 an amendment to MARPOL Annex VI that made the Energy Efficiency Design
Index (EEDI) mandatory for new ships and the Ship Energy Efficiency Management Plan (SEEMP) for all
ships in order to promote the use of more energy efficient equipment and engines (The Marine
Environment Protection Committee, 2011). Shipowners and ship designers have the freedom to choose
the technical measures they prefer as long as a minimum energy efficiency level per capacity mile is
attained.
On 1 March 2018, amendments to MARPOL Annex VI on Data collection system for fuel oil consumption
of ships entered into force. Ships of 5,000 gross tonnage and above are required to collect consumption
data for each type of fuel oil they use, as well as other specified data including proxies for transport work.
The aim of these amendments is to assist Member States in making decisions about any further measures
needed to enhance energy efficiency and address greenhouse gas emissions from international shipping.
Data collection will begin on 1 January 2019. (International Maritime Organization, 2018a)
In April 2018, the IMO adopted an initial strategy on the reduction of greenhouse gas emissions from ships.
More specifically, GHG emissions from international shipping should peak as soon as possible and the total
annual GHG emissions should be reduced by at least 50% by 2050 compared to 2008 and if possible, efforts
should be pursued towards phasing them out entirely. (International Maritime Organization, 2018b)
There are however a lot of possibilities to reduce greenhouse gas emissions. Bouman et al. (2017) provides
a comprehensive overview of around 150 studies of the CO2 emission reduction potentials and measures
published in literature. Their findings show that of all the 22 individual reduction measures considered,
the use of biofuels has the greatest CO2 emission reduction potential. Although biofuels are not yet
commonly used on ships, marine engines can run on so-called drop-in fuels without too much difficulties
due to the very high flexibility of these engines. These drop-in fuels are liquid bio-hydrocarbons that are
functionally equivalent to petroleum-derived fuels and are fully compatible with existing petroleum
structure (Hsieh and Felby, 2017). Biofuels are currently categorised into four generations (Aro, 2016).
While first generation biofuels are made from crop plants grown on arable land, second generation
biofuels are made from feedstock of lignocellulosic, non-food materials like straw or forest residues. The
third generation biofuels are based on algal biomass. Photobiological solar fuels and electrofuels are the
fourth generation of biofuels.
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The main problem associated with first- and second generation biofuels is their negative environmental
impact due to land-use and competition with food production. Third generation biofuels extracted from
algae might provide a sustainable solution in this respect.
The objective of this thesis is to look if the maritime sector could consider the use of biofuels made from
microalgae to fuel its ships in order to mitigate its impact on global warming. This is done by means of a
literature review. First, there will be looked at the role shipping plays in global warming and possibilities
to reduce its impact. Then, a brief overview of the role biofuels can play herein is given. The main part of
this literature review is devoted to the possible use of microalgal biofuel by ships. The main question of
this thesis is therefore formulated as follows:
Is the use of biofuel made from microalgae a viable option to reduce the emissions of greenhouse gases
from the global shipping fleet considerably in the coming decades?
In order to answer the main question, the following sub-questions should be answered:
How are microalgal biofuels produced?
Are microalgal biofuels suitable for use in marine engines?
What are the challenges and potentials related to production and delivery of microalgal biofuels to the
global shipping fleet?
As a seafarer you are more or less directly contributing to global warming by navigating your ship. Climate
change and more important, how to prevent it has always raised my interest and I realise that my
generation will have to take actions in order to keep our planet liveable. Not only now, but also for our
children and the generations that follow. This is why I really wanted to write my thesis on this subject.
A review of greenhouse gas reduction technologies is given in the following chapter of this thesis. Chapter
3 then focuses on the use of biofuels in shipping. In chapter 4, the production process, the link with
greenhouse gases and the potential for use on ships of biofuel made from microalgae are described. The
fuel consumption of the global shipping fleet as well as current and future production volumes of
microalgal biofuel are considered in chapter 5. Finally, conclusions from the literature review are drawn in
chapter 6.
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2. Greenhouse gas reduction technologies
2.1 About greenhouse gases
2.1.1 Terminology
Before elaborating further on greenhouse gases in the shipping sector, it is necessary to explain what these
gases are, the most common terminology used and their role in the global climate change.
Baede et al. (2007) define greenhouse gases as follows:
Greenhouse gases are those gaseous constituents of the atmosphere, both natural and
anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of
thermal infrared radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds. This
property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO2), nitrous oxide
(N2O), methane (CH4) and ozone (O3) are the primary greenhouse gases in the Earth’s atmosphere.
Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such
as the halocarbons and other chlorine and bromine containing substances, dealt with under the
Montreal Protocol. Beside CO2, N2O and CH4, the Kyoto Protocol deals with the greenhouse gases
sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). (Baede et al.,
2007)
When reading through literature about this subject, it becomes clear that one type of greenhouse gas
plays an important role namely CO2. Baede et al. (2007) define carbon dioxide (CO2) as:
A naturally occurring gas, also a by-product of burning fossil fuels from fossil carbon deposits, such
as oil, gas and coal, of burning biomass and of land use changes and other industrial processes. It
is the principal anthropogenic greenhouse gas that affects the Earth’s radiative balance. It is the
reference gas against which other greenhouse gases are measured and therefore has a Global
Warming Potential of 1. (Baede et al., 2007)
Another term that is related to the previous definition is ‘Global Warming Potential’. This is defined as
follows:
An index, based upon radiative properties of well mixed greenhouse gases, measuring the radiative
forcing of a unit mass of a given well mixed greenhouse gas in today’s atmosphere integrated over
a chosen time horizon, relative to that of carbon dioxide. The GWP represents the combined effect
of the differing times these gases remain in the atmosphere and their relative effectiveness in
absorbing outgoing thermal infrared radiation. The Kyoto Protocol is based on GWPs from pulse
emissions over a 100-year time frame. (Baede et al., 2007)
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Finally, CO2-equivalent (CO2-eq) emission is defined as:
The amount of carbon dioxide (CO2) emission that would cause the same integrated radiative
forcing, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture
of GHGs. (IPCC, 2014)
Greenhouse gases thus contribute to the greenhouse effect. Simply put, the greenhouse effect is the
warming of Earth’s surface by infrared radiation originating from greenhouse gases in the atmosphere
(IPCC, 2018).
Figure 1: Representation of the greenhouse effect. (IPCC, 2018)
2.1.2 Emission sources on ships
It is clear from the definitions in the previous section that water vapour (H2O), carbon dioxide (CO2), nitrous
oxide (N2O), methane (CH4) and ozone (O3) are main greenhouse gases that contribute to global warming.
Smith et al. (2014) divide sources of GHG’s into two components: emissions resulting from the combustion
of fuels and other emissions originating from non-combustion sources (refrigerant gases). Although these
refrigerant gases have a significant GWP, their contribution to global warming is minor. They will not be
considered further in this dissertation. Three sources on board of ships are responsible for the production
of GHG’s from combustion: main engine(s), auxiliary engines and boilers (Smith et al., 2014). While CO2 is
produced in most combustion engines that run on conventional fossil fuels, the emission of methane is
more closely linked to LNG-powered vessels.
The amount of emissions from the main engine(s) depends on the age, power output and load factor of
the engine. The latter two vary over time and they depend on the ship’s operational mode, speed, loading
condition, weather etc. (Smith et al., 2014). Likewise, emissions from auxiliary engines depend on the
power demand, power output, load factor and engine build year. Boilers can be used for supply of hot
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water to the main engine(s), for heating of the accommodation or to power steam plants on tankers. Of
the three emission sources considered, they generally produce significantly fewer emissions than main- or
auxiliary engines (Smith et al., 2014).
Figure 2, taken from the Third IMO GHG study 2014, shows estimates of the emitted CO2 and CO2
equivalent from 2007-2012 of total shipping and international shipping. The GHG’s CO2, CH4 and N2O were
used to calculate the CO2 equivalent. During this period, total shipping emitted on average 1,015 million
tonnes CO2 and 1,036 million tonnes CO2 equivalent (Smith et al., 2014).
Figure 2: a) Shipping CO2 emissions compared with global CO2 (values in million tonnes CO2); and b) Shipping GHGs (in CO2e) compared with global GHGs (values in million tonnes CO2e). (Smith et al., 2014)
2.2 Reduction technologies
There exist a multitude of measures to reduce the emission of greenhouse gases from ships. The
effectiveness of these measures depend on the individual vessel size, type, machinery equipment installed
and the ship’s operational profile (DNV-GL, 2017). Maritime emission reduction measures are generally
categorized into two groups: operational and technical (Bouman et al., 2017). Operational measures are
measures that are related to the operations at ship or fleet level and can be applied to any ship type.
Technical measures focus on energy savings by optimizing the ship’s infrastructure or the fuel used for
propulsion or auxiliaries.
Bouman et al. (2017) reviewed the existing literature and divided the possible reduction measures into
five categories: hull design, power and propulsion, alternative fuels, alternative energy sources, and
operations. This can be seen in Figure 3, which will be discussed in this chapter.
Economies of scale, hull shape, light-weight construction, coating and lubrication of the hull are measures
that fall under the category ‘hull design’. Economies of scale is the idea that by increasing the ship’s size,
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relatively less fuel per freight unit transported is consumed. When the ship’s cargo-carrying capacity is
doubled, the required power increases with two thirds of the increase in ship size (Lindstad, 2013). The
large range of CO2 reduction potential (4–83%) (Faber et al., 2011; Gucwa and Schäfer, 2013; Halfdanarson,
2015; Lindstad et al., 2016, 2012; Lindstad and Eskeland, 2015; Miola et al., 2011; Pauli, 2016; Tillig et al.,
2015; Wärtsilä, 2009) for this measure identified in the study of Bouman et al. (2017) is notable. Viscous
resistance forms the biggest part of the total resistance of a ship moving through water (ABS, 2013). Skin
friction is the largest component of the viscous resistance and can be reduced by reducing the wetted
surface of the hull, reducing speed or by improving the way the wetted surface interacts with the fluid it
is in touch with (ABS, 2013). An obvious method is using good anti-fouling paint and regular cleaning of
the hull when the ship is in dry dock. Another technique is the use of air lubrication. The main principle of
this system is the reduction of wetted surface by maintaining a thin layer of air bubbles along the hull, thus
reducing skin friction (ABS, 2013). Although air resistance of a ship is limited, savings can also be made by
optimizing the design of the superstructure (Buhaug et al., 2009). The reduction potential of a light-weight
construction, coating and lubrication used as a single measure is somewhat limited (Bouman et al., 2017).
The category ‘power and propulsion’ has an overall low reduction potential. The maturity of technology
plays a role herein and future improvements will likely be limited as the physical limits are approached
(Bouman et al., 2017). ABS (2013) identifies Propulsion Improving Devices (PIDs). These include wake
equalizing and flow separation alleviating devices, pre/post-swirl devices and high-efficiency propellers.
Wake equalizing and flow separation alleviating devices correct known existing hydrodynamic problems
and are less effective when the ship geometry has been designed correctly. The most common examples
are Grothues spoilers, Schneekluth ducts and stern tunnels. While pre-swirl devices are hydrodynamic
appendages that improve the angle of attack of the water flow on the propeller blades, post-swirl devices
attempt to condition the flow behind the propeller. Also the propeller itself must be adapted to the
operational profile of the ship. Larger diameter propellers with fewer blades rotating at a lower RPM are
generally speaking more efficient than smaller ones. Examples of ‘special’ designs are contra-rotating
propellers, ducted propellers and propellers with end-plates (ABS, 2013).
Energy savings can be made on both the propulsion plant and the auxiliary engines. GLOMEEP (2018) gives
an overview of the most important measures to save energy for the machinery. Engine de-rating,
automatic and manual engine performance optimization, hybridization, the use of a shaft generator and
waste heat recovery systems are examples that are considered for the main engine. Cold ironing, the
optimization of the auxiliary systems and improve auxiliary engine load are measures that can be applied
to increase fuel savings for the auxiliaries.
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Bouman et al. (2017) considered two types of alternative fuels: biofuels and LNG. The use of biofuels has
the greatest CO2 reduction potential of all the measures considered in their paper (25 - 84% with a median
value of 70%) (Bengtsson et al., 2012; Brynolf et al., 2014; Eide et al., 2013; Faber et al., 2009; Gilbert et
al., 2014). This reduction potential is however influenced by some factors like changes in feedstock,
processes, efficiencies, etc. but also the method used to calculate the reduction potential. Biofuels will be
considered further on in this thesis. The use of the fossil fuel LNG will result in lower CO2 emissions but it
does not contribute to reducing CO2 emissions to the levels that would be required for addressing climate
change (DNV GL, 2014). LNG is however the most widely used alternative fuel today (DNV GL, 2017).
Liquified petroleum gas (LPG) also has potential to lower CO2 emissions (DNV GL, 2017). Nuclear power
has the advantage of not producing any GHG’s, but its use is controversial and although very little accidents
happen due to high safety standards, it is unlikely that this alternative will be used in shipping the coming
decades (DNV GL, 2014).
The category ‘alternative energy sources’ comprises wind- and solar power, fuel cells and cold ironing.
While wind power shows promising results, solar power has a lower reduction potential because of its
dependency on the installed area of solar panels and the amount of sunshine it receives during daytime.
Examples of measures that fall under ‘wind power’ are sails, kites and Flettner rotors. These measures are
however not mature in the sense that they are “new unproven-, unproven existing- , or proven existing
technology/principle but with very few installations and little to no operational experience”(GLOMEEP,
2018). The relative unreliability of these energy sources make them unsuitable for deep sea transport or
operations in some latitudes with seasonal weather conditions. To install sails, Flettner rotors and solar
panels, space is required which is not present on all ship types (e.g. sails on a container ship are difficult)
(DNV GL, 2014; GLOMEEP, 2018). Cold ironing, that is connecting the ship’s electrical grid to power from
the shore, can in theory be used on all types of ships but its reduction potential is dependent on the time
spent in port (Bouman et al., 2017). Fuel cells convert chemical energy directly into electricity in an
electrochemical process (Meek-Hansen, 2002). It could substitute the auxiliary engines partly or wholly,
but application for large power output is still questionable (Bouman et al., 2017; Lindstad et al., 2015).
The last category, ‘operation’, comprises operational measures like speed- and voyage optimization,
capacity utilization and other measures like trim/draft optimization. Especially speed optimization can
reduce fuel consumption considerably which in turn reduces emissions. At low speeds, the required power
for the propulsion of the vessel is proportional to the third power of the speed. When higher speeds are
reached, the resistance from wave generation becomes dominant and the demand for power increases to
more than the third power of speed which increases fuel consumption considerably (Buhaug et al., 2009).
Voyage optimization comprises advanced weather routing, route planning and voyage execution. Weather
routing for example, is trying to minimize the negative influence of wind and waves on the needed power
to propel the vessel. This can be used on all ships (GLOMEEP, 2018).
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Figure 3: CO2 emission reduction potential from individual measures, classified in 5 main categories of measures. (Bouman et al., 2017)
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3. Biofuels in shipping
It can be concluded from the previous chapter that biofuels have the largest potential to reduce CO2
emissions from ships when used as a single measure. What are biofuels, how are they produced and which
types are eligible for use in marine engines? This chapter will give an overview of this matter.
3.1 Marine engines and their fuels
Before continuing about biofuels and how they could be used on ships, it is important to see how a ship’s
propulsion- and power plant works and identify the fuels they run on.
According to Florentinus et al. (2012), two types of marine engines can be distinguished. The first type is
the Otto engine which ignites the fuel with a spark plug. This type is more used on smaller vessels. The
second type is the diesel engine whereby the fuel ignites spontaneously after compression. The latter is
most commonly installed on ships. Turbines are another type of engine, but the only ships built with steam
turbines today are military vessels or specialized vessels such as LNG carriers, in which the cargo can serve
a second purpose as fuel (Hsieh and Felby, 2017). There are also engines that can run both on diesel and
natural gas. These are the so-called dual fuel engines. They have the advantage of using either fuel
depending on price and availability without compromising performance (Hsieh and Felby, 2017).
Diesel engines exist in two-stroke and four-stroke versions. Two-stroke engines are often large, low speed
and have a high efficiency. Four-stroke engines generally have a lower power output and are more
compact than its two-stroke counterpart.
Figure 4 shows the different types of engines and the fuel they can run on.
Figure 4: Common types of marine engines and their fuel compatibility. HFO: Heavy fuel oil, MDO: Marine diesel oil, LSHFO: Low Sulphur Heavy Fuel Oil, LNG: Liquefied Natural Gas. (Hsieh and Felby, 2017)
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Marine fossil fuels can be divided into distillate- and residual fuels. Marine gas oil (MGO) and marine diesel
oil (MDO) are two commonly used distillate fuels. They are used in smaller vessels with medium and high
speed 4-stroke diesel engines. Light fuel oil (LFO) and heavy fuel oil (HFO) are residual fuels with a high
viscosity that need to be heated before use. They are used in larger ships. Intermediate fuel oil (IFO) is a
blend of gasoil and heavy fuel oil. Dimethyl ether (DME) and water-in-diesel emulsions (WiDE) are
alternatives to diesel and can be used as a drop-in fuel in diesel engines. These fuels are however not
produced on a large scale and their use in the shipping sector is thus limited (Hsieh and Felby, 2017).
LNG and LPG are gaseous fuels used in spark-ignition engines. These gases are made liquid to facilitate
storage on board. These fuels are used to a lesser extent than MDO, MGO or HFO. LPG is used more as a
heating fuel rather than for combustion in the propulsion engine. Gasoline, ethanol, methanol, biogas and
hydrogen gas can also be used in spark-ignition engines (Hsieh and Felby, 2017).
3.2 Biofuels: the four generations
Biofuels are fuels made from biological material from plants, microorganisms, animals and wastes. Unlike
fossil fuels, biofuels originate from “present-day” photosynthetic conversion of solar energy to chemical
energy (Aro, 2016). Four generations of biofuels can be distinguished nowadays. This classification is based
on the feedstock used, properties of the fuel and conversion technology used (Baker et al., 2017).
The first generation are the biofuels that are made from sugar, starch or lipid originating from crops. They
are considered as competing with food (Aro, 2016; Baker et al., 2017; Hsieh and Felby, 2017; Ullah et al.,
2014).
The second generation is already an improvement in the sense that it is made from non-edible,
lignocellulosic biomass sourced from forestry wastes or residues, purpose-grown perennial grasses or
trees. The energy content of the biofuel produced annually per hectare is likely to be higher than that of
first generation biofuels (Aro, 2016; Baker et al., 2017; Tyrovola et al., 2017)
Biofuels based on algae are referred to as the third generation. They require much less valuable land and
water that could otherwise be used for food production (Aro, 2016; Baker et al., 2017; Tyrovola et al.,
2017). There are a lot of advantages for this fuel type. Algae grow 20-30 times faster than food crops, they
can grow almost anywhere and contain up to 30 times more fuel than equivalent amounts of other biofuel
sources (Ullah et al., 2014).
Aro (2016) also considers a fourth generation of biofuels: the photobiological solar fuels and electrofuels.
Technology for production of such solar biofuels is an emerging field and further development in the field
of synthetic biology is needed (Aro, 2016).
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3.3 Candidates for marine application
There are a lot of different types of biofuels. Only the most important candidates for marine application
will be considered here. Changing equipment on board of a ship is a costly affair and in times of low profit
margins, shipowners are reluctant to do big investments. It would be useful to have a fuel that is
compatible with existing infrastructure without the need for major modifications of the ship. Drop-in
biofuels provide a solution here. They can be used as direct substitution for current conventional fossil
fuels (Baker et al., 2017). Engine manufacturers estimate that the additional costs for modifications of
ships engines to run on conventional biofuel is less than 5 per cent of the engine cost (DNV-GL, 2018).
Straight vegetable oils (SVOs) are oils extracted from plants and can be used in diesel engines without
processing. They can serve as a replacement for IFO or HFO in low speed engines. This is however not
recommended because the build-up of carbon deposits inside the engine can damage the engine and SVOs
can also damage the lubricant. Vegetable oils can also be processed by a process called transesterification.
Oils are converted to methyl esters with glycerol and water as side products that are later removed. The
result is biodiesel also known as fatty acid methyl ester (FAME). Biodiesel is better for the engine
performance than SVOs due to its lower boiling point and viscosity. FAME can be used to replace MDO
and MGO or it can be used as additive. A full replacement requires adjustments to diesel engines and
approval from the engine manufacturer. Blends up to 20% with petrodiesel are however possible with
little or no engine modifications (Hsieh and Felby, 2017).
Vegetable oils can also be hydrotreated. These hydrotreated vegetable oils (HVOs) are also known as
renewable diesel. The overall production process is more costly than for FAME, but the result is a drop-in
fuel that requires no modifications of diesel engines and distribution- and refuelling facilities. It can be
used as a substitute for HFO. Feedstock quality can be lower as that of biodiesel and due to the removal
of all the oxygen during the hydrogenation process, it can be stored for a longer period without oxidizing.
Renewable diesel can also be made from tall oil via a process called pulping. Tall oil is currently made from
Scandinavian pine, spruce, and birch, but production volumes are low. A process that has a promising
prospect is called hydrothermal liquefaction (HTL). HTL is used to convert biomass into gas, liquid and
solids in a hot (250 °C - 350 °C), pressurized (up to 300 bar) water environment for sufficient time to break
down the solid bio polymeric structure to mainly liquid components (Gollakota et al., 2018).
Another option to produce biodiesel is using algae (Hsieh and Felby, 2017). The possibility to use this fuel
in diesel engines and to blend it with petrodiesel is proven (Mostafa and El-Gendy, 2017; Topare et al.,
2011). In a recent study of Hossain et al. (2018), the engine performance and emissions of high speed and
low speed diesel engines using microalgae FAME and HTL biocrude was reviewed. The results of this review
indicate first of all that microalgae HTL biocrude has properties that are similar to HFO thus allowing it to
be used in low speed marine diesel engines without further treatment. Soot emission would be reduced,
but NOx emissions may however increase. The power output of the engine may be reduced when using
this HTL biocrude compared to HFO. The microalgae FAME biodiesel was found to be better suited for use
in high speed diesel engines (Hossain et al., 2018).
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Bioethanol is a fuel based on fermenting sugar or starch (first generation) or is made from lignocellulosic
feedstocks (second generation) and is the most common biofuel for use in petrol engines today. It is
however not suited as a drop-in fuel for marine diesel engines because of its low cetane number, low
energy content, its corrosiveness and poor lubricating ability. It can however be used in blends in high
speed auxiliary engines (Florentinus et al., 2012). Pyrolysis oil is made from lignocellulosic feedstocks and
has a high water- and oxygen content when untreated. Hydrogenation is necessary to make it suitable for
use in diesel engines, making it less attractive due to the higher price. Fischer-Tropsch diesel and dimethyl
ether are made by a gasification technology. Fuels produced with this method have however more
potential in the aviation fuel market. The technological development and commercial availability of
biomass gasification also limits its application potential (Hsieh and Felby, 2017).
Figure 5: Overview of different feedstock conversion routes to marine biofuels including both conventional and advanced biofuels. (Hsieh and Felby, 2017)
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4. Biofuel from algae
The main problem associated with first- and second generation biofuels is their negative environmental
impact due to land-use and competition with food production. Third generation biofuels extracted from
algae might provide a sustainable solution in this respect. Some important advantages of using algae
instead of plants or seeds for the production of biofuel are: their high grow rates, the capability of
production all year round, less water is needed than for the cultivation of terrestrial crops, no herbicides
or pesticides are needed and CO2 from flue gases emitted from fossil fuel-fired power plants and other
sources can be sequestered. Depending on the algae species, cultivation can be done in fresh water and
in salt water or even in wastewater (Laurens, 2017). In this chapter, the production process, the link with
greenhouse gases and the potential for use on ships of biofuel made from microalgae will be described.
There are a lot of possible pathways to produce biofuel from algae, but a few processing steps are similar
in all cases. First algae have to be cultivated, then they are harvested and finally they are processed further
to extract the oil and make biofuel out of it. These steps will be discussed further on.
4.1 Cultivation
When talking about algae, two groups can be considered: macroalgae and microalgae. Although the use
of macroalgae for biogas production is proven, the majority of research has been done to microalgae
(Laurens, 2017). According to Laurens (2017), “microalgae are diverse single-cell organisms, capable of
photosynthesis to convert inorganic carbon in the form of CO2/carbonate to organic constituents that
make up the cell’s composition”. It is estimated that there exist approximately 100,000 different species
of microalgae worldwide (Kröger and Müller-Langer, 2012). Microalgae are not only used for the
production of biofuel, but their use in e.g. food, cosmetics, pharmaceuticals or biofertilizers and soil
conditioners in agriculture is well known (Priyadarshani and Rath, 2012). Phototrophic growth or
cultivation is the photosynthetic conversion of CO2 with sunlight and nutrients to form lipids,
carbohydrates and protein. Heterotrophic production of microalgae involves the use of sugars and air or
molecular oxygen that are fed into a fermentor to grow algae to high algal cell mass concentrations. This
is done in more highly controlled conditions than are possible in outdoor systems where phototrophic
growth takes place. Two commonly used methods to do phototrophic cultivation is in closed
photobioreactor systems or in open ponds, which will be described further on (Laurens, 2017).
The main ingredients to cultivate algae are thus water, CO2, light and nutrients like carbon, nitrogen,
phosphorus, and potassium (Park and Lee, 2016). Daylight or artificial light can be used. It is however not
economically feasible to consume electricity to cultivate microalgae for biofuels and thus sunlight should
be used as the sole energy source (Blanken et al., 2013). Algae species with a high lipid content are desired
to attain high yields after processing (Gendy and El-Temtamy, 2013). The oil that is finally extracted, the
so-called microalgal lipids, is similar to vegetable oil and can besides biofuel also be used as e.g. cooking
oil (Chen et al., 2017). The oil productivity is the mass of oil produced per unit volume of the microalgal
broth per day and this depends on the algal growth rate as well as the oil content of the biomass (Yusuf,
2007). Although there are a lot of algae species, not all of them are equally suited for commercial
production and scientists are currently experimenting with different types to find an optimal solution.
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4.1.1 Closed photobioreactor systems
Photobioreactors (PBRs) are closed (or almost closed) systems for algal cultivation where light is supplied
either directly by the sun or via artificial sources such as LEDs. They are designed in different shapes with
transparent materials such as glass and plastic for efficient utilization of natural light. Examples of designs
that are commonly used are tubular- and flat plate PBRs. By circulating the algal culture, the exposure of
the algae to light can be maximized. The closed system prevents the introduction of contaminating living
organisms into the algal cultures and it also prevents escape of these organisms that could cause
environmental damage. The main advantage of using a PBR is higher biomass productivity and cell density.
Another advantage of this system is a better control of culture conditions such as temperature, light, pH,
and nutrients for prolonged durations as well as low water evaporation. A disadvantage of a PBR is the
high construction- and operation cost at large scale (Laurens, 2017; Shen et al., 2009).
4.1.2 Open ponds
The use of open ponds is the oldest, simplest and most used method for the cultivation of algae today.
Three types of ponds are commonly used: open raceway ponds (ORP), circular ponds, and unstirred ponds.
Raceway ponds, looking like an automotive raceway circuit, are constructed either in singles or as groups
of channels built by joining individual raceways together. The ponds have a depth between 15 and 30 cm
and a paddlewheel is often used to drive water continuously around the circuit in order to expose algae
cells to sunlight and CO2. Circular ponds are deeper than raceway ponds and use a centrally pivoted
agitator to mix the water. The unstirred ponds is the simplest, most economical and least technical type
of pond and uses no mixing device or whatsoever (Shen et al., 2009).
Figure 6: Three types of ponds. (Shen et al., 2009)
15
Advantages of this type of cultivation method are the relatively low construction and maintenance costs,
the ability to scale up by increasing the number of ponds, it is easy to clean and it provides for the
possibility of integration with wastewater treatment processes. Disadvantages are the relatively low
biomass yield per surface area compared with PBRs, high harvesting costs and contamination by fast‐
growing wild algae or microorganisms that feed on algae (Shen et al., 2009).
4.1.3 Suitable areas for cultivation
Park and Lee (2016) calculated the maximum global microalgal biomass and biofuel productivities based
on average annual surface solar and photosynthetic efficiency of algal culture systems. They considered a
land-based open raceway pond and a flat-panel photobioreactor. Both lipid-moderate (25%) and lipid-rich
(50%) microalgae were used for calculation.
They found that regions at lower latitude generally have a higher maximum biofuel productivity. The
equatorial region does however not have the highest biofuel productivity because it is frequently cloudy
and rainy in the Intertropical Convergence Zone. Weyer et al. (2010) note that solar irradiance is strongly
dependent on the climate and not only on latitude. Despite this, the tropical zone has the highest overall
biofuel productivity because of the substantially higher solar irradiance in the region. This can be seen in
Figure 7.
Gendy and El-Temtamy (2013) note that the countries with a coastline located in an area of the
Mediterranean Sea between 30°N and 45°N have good potentials for cultivating algae. These include
Morocco, Algeria, Tunisia and Egypt. Reasons for that are the good temperatures (not often below 15°C)
and lots of unused desert land. This industry can also provide for local jobs and help development of the
country involved.
Figure 7: Maximum microalgal biofuel productivity around the globe in ton of oil equivalent (TOE). (Park and Lee, 2016)
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4.2 Harvesting
Once the microalgae are fully grown, they can be harvested. This production step represents 20-30% of
the biomass production costs (Barros et al., 2015). The reason for that is because of the very small size of
microalgae and their growth in very dilute cultures with densities close to that of the water. Barros et al.
(2015) reviewed different harvesting methods applied to microalgae which are described below.
Before the ‘main’ harvesting process, pre-processing of the microalgae cultures can be done by screening.
This is basically capturing a first part of the microalgae by moving a screen with a fine mesh through the
algae. Only a relatively small part is harvested in this way.
The main harvesting process generally consists of two steps: thickening and dewatering. This is done to
obtain a thick algal slurry to enable further downstream processes. Harvesting methods can be divided
into mechanical, chemical, biological and electrical methods. Two or more of these methods can be
combined to obtain a better separation rate.
Thickening can be done by coagulation/flocculation, gravity sedimentation or flotation.
Coagulation/flocculation increases the effective particle size and concentrates the suspension 20–100
times. It consequently reduces energy demand, making it is the most economical method. This step is
generally followed by gravity sedimentation. Flotation makes, as the name suggests, the algae float on top
of the water by feeding gas bubbles to the water-algae mixture.
After a thick slurry is obtained, it has to be dewatered. This can be done by filtration or centrifugation. By
filtration, the fluid is forced through a filtration membrane leaving microalgal deposits behind. This
method is however not commonly applied in large scale processes despite its capability to harvest
microalgal cells of very low densities. Centrifugation is the fastest, but also the most expensive method
due to its high energy demand.
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4.3 From algae to biofuel
After harvesting, the yield has to be processed in order to make biofuel out of it. The whole process of
cultivation, harvesting and processing the algae to a finished end product (biofuel) is referred to as the
conversion pathway for fuel production. These conversion pathways are similar to chemical engineering
processes and they can basically be divided in biochemical and thermochemical processes (Laurens, 2017).
Figure 8 represents a base-case scenario of a conversion pathway process-flow. The process starts with
cultivation, harvesting and concentration which are previously described. Dissolved air flotation (DAF) is
used to concentrates the suspension and is followed by a solid liquid separation (SLS). The steps that follow
vary depending on the specific process. The obtained algal cell mass can be dried or processed wet. A
hydrophobic solvent (e.g. hexane) is used to extract the lipids. This solvent can be recycled afterwards.
The extracted lipids are then further processed to renewable diesel via hydrotreating or to FAME biodiesel
via transesterification which is the most common chemical reaction technique in biofuel production (Vo
Hoang Nhat et al., 2018). The residual cell mass can be used for the production of biogas by anaerobic
digestion (AD). This biogas can be deployed for the power generation of the entire plant. The advantage
of the anaerobic digestion is that the recycling of a large fraction of the nutrients used during cultivation
is possible (Laurens, 2017).
Figure 8: Basic conversion pathway from algae to fuel. (Laurens, 2017)
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4.4 Challenges and potentials
The use of microalgae for biofuel production might be a nice idea. There are however certain obstacles
that prevent large-scale production. A lot of research has been done whereby economic, technical,
environmental and other challenges are addressed. The good news is that there might also be some
opportunities to overcome these issues. The most important challenges and opportunities will be
reviewed here.
4.4.1 Techno-economic challenges
Since 2010, major developments are made in the field of algae production for bioenergy. This development
slowed down due to the decline in oil prices in August 2014. The absence of consistent policies on carbon
pricing together with low prices for natural gas contribute to this development (Laurens, 2017).
To understand the commercial viability of microalgae as a feedstock for biofuel, TEA (Techno-Economic
Assessment) modeling has been used. These assessments couple engineering-based process modeling
with economic estimates and financial assessment to quantify product selling prices, typically on a dollar-
per gallon basis (Quinn and Davis, 2015).
Figure 9, taken from Quinn and Davis (2015), shows the reported cost of the production of microalgal
biofuel found in the literature. The costs range from $1.65 gal-1 to $33.16 gal-1 (± €0.4 /l – €7.3 /l at current
exchange rate). The large variability can be attributed to differences in boundaries, processing pathways,
and modeling of either current or future systems (Quinn and Davis, 2015).
Figure 9: Techno-economic results from literature review of Quinn and Davis (2015). Costs are reported in 2014 dollars. (Quinn and Davis, 2015)
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The microalgae productivity is one of the most important factors in cost estimation as there will be great
difference on the output in the same capital investment with different biomass productivity (Chen et al.,
2018). Weyer et al. (2010) calculated the theoretical absolute upper limit to algal production as well as the
best case scenarios. They found that the theoretical maximum amount of unrefined algal oil that can be
produced is 354 m3 ha-1 yr-1 and best cases based on realistic efficiencies calculated for six global sites
range between 40.7 – 53.2 m3 ha-1 yr-1. Figure 10, taken over from Quinn and Davis (2015), shows various
reported oil yields in the literature with a minimum of 2.3 m3 ha-1 yr-1 reported by Ramachandra et al.
(2013) and a maximum of 136.9 m3 ha-1 yr-1 reported by Mata et al. (2010). There is thus a lot of uncertainty
in both current and future potential microalgae productivity (Quinn and Davis, 2015).
Figure 10: Oil yield assumptions for growth systems found in life cycle, techno-economic, and scalability assessment. Some studies report a range for the productivity with the high end reported and the low end illustrated in grey. (Quinn and Davis, 2015)
The biggest barrier to market deployment of microalgae for use as biofuel are the high cost of cultivating
and harvesting the algal biomass feedstocks (Chen et al., 2017; Laurens, 2017; Singh and Gu, 2010).
According to Chen et al. (2018) cultivation and harvesting are responsible for 50–65% of the total
production cost. Extraction, transesterification, purification and distributions would represent 15–25%,
10–15%, 2–3%, and 2–3% respectively (Chen et al., 2018). A reason of the high harvest cost is the low
microalgae concentration (Chen et al., 2017).
Even though closed photobioreactors have the advantages of higher biomass productivity and decreased
contamination, the high construction- and operation costs makes this option less interesting and it is
unclear whether this will ever become cost competitive with open pond systems for large-scale
deployment (Hannon et al., 2010)
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Due to the paucity of cultivation farms, there is a lack of data on large-scale cultivation (Gendy and El-
Temtamy, 2013). Laboratory-scale data is often extrapolated, which is not representative for large-scale
application (Quinn and Davis, 2015).
Hannon et al. (2010) state that crop protection is vital to ensure resistance against pests and pathogens.
Open ponds are in this respect more vulnerable for contamination by fast-growing wild algae or
microorganisms that feed on algae than closed photobioreactors (Shen et al., 2009). Protection can be
done by engineering species that have robust growth characteristics and significant lipid composition or
using multiple species to slow the spread of specific pests and minimize crop loss in large algal facilities
(Hannon et al., 2010). Genetically modified algae can however also pose a threat to the environment.
When they escape, these algae might persist and produce toxins or might become so abundant that they
create harmful algal blooms (Snow and Smith, 2012).
The challenges regarding the processing of algae oil to a usable liquid fuel are similar as those for
conventional fuel (Hannon et al., 2010). Chen et al. (2017) state that the technology for biodiesel
production from vegetable oil is relatively mature and since microalgal lipids are similar to vegetable oil,
conversion of the microalgal lipids to biodiesel is technically feasible. Future collaborations between
companies producing algae and major oil companies is expected because the latter have extensive
experience maximizing downstream processing efficiencies (Hannon et al., 2010).
Several researchers indicate that the sustainable cultivation of microalgae for biofuel production on a large
scale is not feasible in the short to intermediate term and that further research and development is
required (Bonvincini et al., 2015; Laurens, 2017; Vo Hoang Nhat et al., 2018). A key factor to achieve
economic viability is minimizing the operational and maintenance cost together with the maximization of
oil-rich microalgae production (Gendy and El-Temtamy, 2013).
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4.4.2 Environmental challenges
The cultivation of microalgae requires some basic resources like water, CO2, light and nutrients. The
amount of these resources needed can pose some problems if one wants to produce the biomass in a
sustainable way. Various studies have been published whereby resource requirements are assessed, but
there is a large uncertainty in the results due to the different assumptions that are made with regard to
productivity and the scope of the study (Quinn and Davis, 2015).
First of all, several authors address the issues associated with water requirements (Hannon et al., 2010;
Laurens, 2017; Park and Lee, 2016; Pate et al., 2011; Quinn and Davis, 2015). Pate et al. (2011) assessed
the amount of resources that would be required for large-scale production of microalgae in the United
States. Fresh water demand would pose a significant challenge due to evaporative water loss when a
biofuel production volume of 10 billion gallons per year is reached. Appropriation of irrigation water from
other agricultural applications would be needed to produce more than the aforementioned quantity (Pate
et al., 2011). Using algae strains that require fresh water can be unsustainable for large-scale cultivation
and worsen water scarcity (Gendy and El-Temtamy, 2013). Consequently, water use should be carefully
considered to avoid a future ‘water versus fuel’ debate (Hannon et al., 2010).
Another major challenge is providing enough nutrients to avoid growth reduction. The most essential
nutrients required by most algae are carbon, phosphorous, nitrogen, potassium (macronutrients) but
supply of micronutrients is also important (Markou et al., 2014). Nitrogen represents the lion share of the
overall nutrients composition, followed by phosphorous and potassium (Lam et al., 2012; Park and Lee,
2016). Scale-up of biofuel production could however lead to competition with agriculture for commercial
fertilizer use and it could also endanger sustainability (Pate et al., 2011). Park and Lee (2016) note that the
higher the lipid content of the algae, the lower the nutrient demand.
The cultivation of microalgae can also be a potential threat to local and regional ecosystems. Exotic species
that are released into the natural environment via the system’s wastewater can cause biological invasion
and threaten the safety of native species (Zhu and Ketola, 2012). Except from this threat, there can also
be a potential danger for people, plants and animals. Effluents can contain toxic substances from fertilisers
and disinfectants if not treated. When these are discharged into the environment, they can have a
detrimental effect (Zhu and Ketola, 2012).
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4.4.3 Life cycle assessment
An important element for this thesis are the greenhouse gases that are produced during the lifetime of
the biofuel. In order to estimate the real impact of algal biofuel on the environment, it is not enough to
only look at the impact of burning the fuel in the marine engine. It is more appropriate to take into account
the whole life cycle of the biofuel from production to consumption. This can be done with a so-called life
cycle assessment (LCA). Curran (2013) defines a life cycle assessment as follows: “Life Cycle Assessment
(LCA) is an analytical tool that captures the overall environmental impacts of a product, process or human
activity from raw material acquisition, through production and use, to waste management”.
Well-To-Propeller (WTP) studies are a type of LCA applied to ships. WTP can be divided into Well-To-Tank
(WTT) and Tank-To-Propeller (TTP). WTT comprises the production (from well/field or cultivation
ponds/bioreactors in the case of microalgae), transportation and processing, while the TTP concerns the
combustion of the fuel in the engine. Alam et al. (2012) note that no new carbon is released when burning
biofuel from microalgae because the CO2 that is added to the atmosphere during combustion was taken
out of the atmosphere when the algae biomass grew. Indeed, 1 tonne of algal biomass fixes 1.6-2 tonnes
of CO2 during production (Vassilev and Vassileva, 2016). The microalgae can however also release GHG’s.
During the night or on cloudy days, microalgae can consume oxygen, causing anaerobic zones in the
culture water with emission of CH4 and N2O as a result (Zhu and Ketola, 2012).
WTP studies are relatively new due to the recent focus on GHG emissions from maritime transport
activities and the stricter upcoming regulations on both air quality and GHG’s (DNV GL, 2014). A WTP study
specific on the use of microalgal biofuel on ships is not yet published in the literature to the knowledge of
the present author.
Nonetheless, a large number of LCA’s examining microalgae-to-energy systems have been published
reporting GHG emissions between -2.6 and 7.3 kg CO2eq MJ-1 with more than 85% lying between -0.35 and
0.5 kg CO2eq MJ-1 (Laurens, 2017). The majority of LCA studies do not have access to primary data and they
also fail to consider every process stage, preventing to comment on the overall impacts of microalgae-to-
energy production (Collotta et al., 2016). The outcome of an LCA is thus highly dependent on the system
boundaries and assumptions made, resulting in a wide range of life-cycle GHG emission estimates
(Laurens, 2017; Quinn and Davis, 2015). One should thus always handle results of these studies with care.
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4.4.4 Potentials
Some major advantages of microalgae are certainly the high growth rate, relatively high oil content (some
species have up to 50% of oil content by weight of dry biomass) and a multitude of different species
offering researchers many options (Hannon et al., 2010).
As previously mentioned, providing sufficient nutrients is vital during cultivation. These resources are
however not abundantly available. Integrating algal production and wastewater treatment (WWT) could
be a way to improve sustainability and economic viability of biofuel production from microalgae in the
short term (Laurens, 2017). Wastewater is suited as it is rich in nutrients such as carbon, nitrogen,
phosphorus and dissolved oxygen (Show et al., 2017). Using urban wastewater to cultivate algae for
biodiesel production is proven to be an economically viable and attractive option (Ramachandra et al.,
2013). Agricultural and industrial wastewaters could also be used. Reclaimed water, algae-based fertilizer
and algal biofuels would be the main products resulting from this process. WWT fees and sales from
reclaimed water would provide most of the revenue (Laurens, 2017).
Recycling of the valuable nutrients by anaerobic digestion or by hydrothermal liquefaction of the leftover
biomass could also be considered (Garcia Alba et al., 2013; Markou et al., 2014). The biogas (methane)
obtained from the anaerobic digestion can be used for generating the electrical power necessary for
running the microalgal biomass production facility and has the potential to improve the sustainability of
the ‘microalgae biomass to biodiesel’ conversion process, reduce its cost and environmental impact
(Ehimen et al., 2011).
Depending on the microalgae strain, 1-20% CO2 should be provided for optimal growth. Pumping air
through the culture is one way of doing this. However, air has a relatively low concentration of CO2 (0.04%)
so pumping demands a lot of energy. A higher concentration of CO2 is thus needed. Flue gas from a nearby
power plant can be a good source to provide sufficient CO2 for growing microalgae. However, the high flue
gas temperatures require cooling by a heat exchanger to ensure the survival of the microalgae and to avoid
too much evaporation of the culture water. An opportunity in this case is that the waste heat absorbed by
the cooling water can be further utilized to dry microalgae biomass. It should also be noted that
desulfurization of the flue gas is necessary to remove the SOx in order to avoid a negative effect towards
their growth rate. (Lam et al., 2012)
Park and Lee (2016) propose to culture the algae offshore, in the ocean. The problem with fresh water and
land-use are resolved in this way as seawater can be continuously provided to compensate for the
evaporation losses. The integration with wastewater is also proven to be possible (Novoveská et al., 2016).
CO2 can be provided in the form of flue gas when located near the shore. Culture mixing can be done by
using the ocean waves thus saving energy that would be otherwise consumed by paddle wheels normally
used in open pond systems (Park and Lee, 2016). Waste dumping and sewage discharges in the sea are
considered as pollution, but the high levels of nitrogen and phosphorus are a potential source of nutrients
for offshore microalgae cultivation (Kim et al., 2015). These offshore systems are however not studied as
extensively as land-based systems and issues with e.g. salt or fouling should be researched further (Park
and Lee, 2016).
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5 Fuelling the global shipping fleet
In order to estimate the viability of providing the global shipping fleet with algal biofuel, it is necessary to
know the quantities that should be produced and whether there is enough capacity to meet the demand.
This chapter will provide the necessary information with facts and figures obtained from the literature.
5.1 How much is needed?
An important question that should be answered is: ‘how much fuel must be provided yearly to the global
shipping fleet?’. The International Council on Clean Transportation (ICCT) calculated the total fuel
consumption of the global shipping fleet using Automatic Identification System (AIS) data and ship
characteristics data (Olmer et al., 2017). Total fuel consumption is a combination of the international-,
domestic- and fishing fleet. The results can be seen in Figure 11. This figure includes fuel consumption
estimates from the Third IMO GHG Study and the International Energy Agency’s (IEA’s). The fuel
consumption was a little less than 300 million tonnes per year in the last four years according to the IMO
and the ICCT and approximately 260 million tonnes according to the IEA.
The different methodological approach used can be an explanation for the gap between the estimates.
Whereas the IEA based its estimates on fuel sales data, the IMO and the ICCT used an activity-based
approach.
After a peak around 2008, the fuel consumption slightly decreased, but a trend of increasing consumption
is emerging as the economy recovers from the global financial crisis (Olmer et al., 2017).
Figure 11: Fuel Consumption estimates from IEA, IMO, and ICCT, 2007–2015. (Olmer et al., 2017)
25
The total fuel consumption was also divided into the categories international, domestic and fishing. As can
be seen in Figure 12, both the IEA and the ICCT agree that the lion share of fuel in 2015 is consumed by
international shipping. There is however a notable difference between the estimates for fuel consumption
of the domestic fleet. This can be explained by the fact that the IEA uses a different definition for
international shipping. They define international shipping as: ‘shipping occurring between ports in two
different countries’ and domestic shipping as: ‘shipping between two ports in the same country’. The IMO
and the ICCT, however, attribute different ship types and gross tonnages to each category (Olmer et al.,
2017).
Figure 12: Fuel consumption by international, domestic, and fishing activity, 2015. (Olmer et al., 2017)
Finally, Olmer et al. (2017) looked at the distribution between distillate- and residual fuels and LNG
consumption of the total shipping fleet. This can be seen in Figure 13. In 2015, the residual fuels accounted
for 72% of the consumption and distillate fuels for 26%. Only 2% of the total fuel consumption was LNG
(Olmer et al., 2017).
Figure 13: Fuel consumption by the global shipping fleet by fuel type, 2015. (Olmer et al., 2017)
26
Figures 11, 12 and 13 represent historical fuel consumption. In order to estimate the volumes of algal
biofuel to be supplied in the future, it is necessary to have an idea of the projected fuel consumption. This
is however not so certain and depends on a lot of factors. It could for example be useful to look at the
amount of ships that will be added to the present fleet and possible energy efficiency improvements of
ships in the future.
According to Hossain and Zakaria (2017) the shipbuilding market is driven by several key factors like gross
domestic product, global seaborne trade, improved economic growth, rising urbanization, fuel price, and
increase in global steel production. The same authors state that increased competition, environmental
regulations, enhanced globalization and political and financial instability will affect the expansion of the
shipbuilding industry. Nobody knows exactly how this will evolve and one can only guess.
Emissions from international shipping are however estimated to increase by 50%–250% in the period up
to 2050 if no measures are taken by the shipping industry, suggesting a growth in total fuel consumption
(Smith et al., 2014). As already mentioned in the introduction, the IMO adopted the first global mandatory
GHG-reduction regime for the shipping sector in 2011. More specifically, the Energy Efficiency Design Index
was introduced to ensure that a minimum energy efficiency level per capacity mile is attained for newly
build ships. This regulation entered into force on 1 January 2013. The EEDI is made stricter every few years
and ships constructed in 2025 will be required to be at least 30% more energy efficient than those
constructed in 2014. A study of Transport & Environment (2017) found that a substantial share of the new
build fleet already complies and over-complies with current and future (2025) design efficiency
requirements. A realisation that more has to be done to combat global warming triggered the adoption of
a new strategy by the IMO in April this year with a more ambitious target, namely the reduction of total
annual GHG emissions by at least 50% by 2050 compared to 2008 and if possible, efforts should be pursued
towards phasing them out entirely (International Maritime Organization, 2018c).
Two candidate short-term measures mentioned in the document (International Maritime Organization,
2018c) describing this strategy are:
“consider and analyse measures to encourage port developments and activities globally to
facilitate reduction of GHG emissions from shipping, including provision of ship and shore-
side/on-shore power supply from renewable sources, infrastructure to support supply of
alternative low-carbon and zero-carbon fuels, and to further optimize the logistic chain and its
planning, including ports”
and
“develop robust lifecycle GHG/carbon intensity guidelines for all types of fuels, in order to prepare
for an implementation programme for effective uptake of alternative low-carbon and zero-
carbon fuels”.
This shows that the IMO recognizes the importance of alternative fuels and considers its implication in
the coming years. These measures are also mentioned as candidates for mid- and long-terms.
27
DNV-GL (2017) assigned fuel consumption to vessel type- and size. It can be seen in Figure 14 that the
biggest consumers are the largest container ships, cruise ships, bulkers and crude oil tankers. Only 35% of
the global fleet is responsible for more than 80% of the total fuel consumption (DNV-GL, 2017). A big
container ship for example can store up to 10 kilotons of fuel and consume up to 200-250 tons of fuel per
day (Hsieh and Felby, 2017). These are huge amounts and bunker suppliers should be able to provide this
continuously and at irregular times. The fuel also has to be stored over long periods of time and should be
stable to transport over long distances. All these factors have to be taken into account when assessing the
viability of algal biofuel production and delivery possibilities on a long-term basis.
Figure 14: Annual fuel consumption per vessel. (DNV-GL, 2017)
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5.2 Algal biofuel producers and projects
5.2.1 Global algae biofuel industry
Laurens (2017) made an overview of the funded research projects and commercial operations of the algae
industry worldwide by executing browser searches and by reading company websites. Although the
overview is probably not complete, it gives an impression of the general trends worldwide and within
specific geographic regions as can be seen in Figure 15. The red balloons in the figure represent commercial
operations and the green balloons are research/demonstration projects (both micro- and macroalgae).
Various production strategies are used on a global scale, ranging from open pond cultivation and
photobioreactors for phototrophic cultivation to large-scale aerobic fermentors for heterotrophic
production. The companies included in the data are not only producing algal biofuels, but also higher value
products like skin care products, nutrients, and animal feeds. The research subsection includes
government funded projects, universities and national laboratories and mainly represents larger projects.
Research projects put a large emphasis on conversion to bioproducts and biofuels, but also strain
improvement strategies and cultivation improvements are studied (Laurens, 2017).
North American and European regions lead the academic publishing realm in the area of algal biofuels,
whereas the US, EU and China file the majority of patent applications worldwide. In Asia and a lot of
commercial groups in the European Union concentrate on the production of microalgae and seaweed as
food crops. Even though China historically has cultivated seaweed, a major part of today’s microalgae is
grown in this region as well. The Chinese Algae Industry Association alone has over 600 members.
According to Chen et al. (2018) there are many reports on plans to build microalgae biodiesel production
plants but no successful case has been known so far when considering cost comparability with petro-diesel
and vegetable biodiesel.
Figure 15: Overview of global commercial and research operations. (Laurens, 2017)
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5.2.2 Current and future microalgal production volumes
Numbers on the annual global production volume of microalgae and microalgal biofuel are scarce. The
development of algal biofuel slowed down due to the fall in world oil prices in 2014 and the recent global
economic crisis (Brutyan, 2017; Laurens, 2017).
Baker et al. (2017) examined the research & innovation potential for feedstock production, advanced
biofuels production and use of advanced biofuels in Europe. They found that the current production of
aquatic biomass from microalgae is negligible in Europe. Today’s global annual microalgae production for
food and feed products at a commercial scale is estimated to be 9 200 tonnes by Baker et al. (2017) and
only 1000 tonnes per year by Laurens (2017). The authors further anticipate that a technical production
potential of 41 Mt/y at costs below 1 330 €/t can be realized by 2030 in Europe and that this production
volume could be tripled per decade with production costs below 840 €/t by 2050. This can be seen in
Figure 16. Only twelve EU Member States currently provide significant amounts of aquatic biomass to the
EU market of which six are able to deliver quantities of 10 Mt dry matter or more. Spain is identified to
have the biggest potential to grow algae in comparison with other EU Member States. Baker et al. (2017)
finally conclude that despite its large theoretical potential, production of microalgal biomass is unlikely to
be competitive by 2030 or 2050.
Brutyan (2017) estimates that by 2030, biofuel from algae could replace more than 70 billion litres of fossil
fuel per year on a global scale.
Figure 16: Microalgae biomass availability potential. (Baker et al., 2017)
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5.2.3 Shipboard projects
In December 2011, a test with algal derived renewable diesel was performed aboard of the 300-meter
long Maersk Kalmar, a ship owned by Maersk Line, the biggest container liner in the world. The test was
done in cooperation with the U.S. Navy as part of an integrated testing and certification program on a
6500 nautical mile voyage from Germany to India. The fuel was delivered by Solazyme, a renewable oil
and bioproducts company based in San Francisco (Business Wire, 2012).
The Maersk Kalmar used a dedicated auxiliary test engine for this test and in total 30 tons of algal biodiesel
were burned with fuel blends ranging from 7% to 100% throughout the voyage. Emission data on nitrogen
oxides, sulphur oxides, CO2 and particulate matter as well as the effects on power efficiency and engine
wear and tear were obtained (Business Wire, 2012; The Maritime Executive, 2011).
In March 2012, the U.S Navy frigate USS Ford successfully sailed from Everett (Washington) to San Diego
using 25000 gallons (94635 litre) of a 50/50 algae-derived, hydro-processed algal oil and petroleum F-76
blend. The fuel was consumed by the ship’s LM 2500 gas turbines that functions as propulsion system. No
different procedures were needed for receiving, handling, or processing the biofuel than the normal ones
and the operational performance of the fuel system and gas turbine engines on the blend was almost
identical to operations on traditional F-76 (Naval Sea Systems Command Office of Corporate
Communications, 2012).
It should be mentioned that no test results have been published of the aforementioned projects to the
knowledge of the present author.
31
6 Conclusion
Today, shipping accounts for approximately 3% of annual GHG emissions and this could increase by 50%–
250% in the period up to 2050 if no measures are taken by the shipping industry. In April 2018, the IMO
adopted an initial strategy to reduce greenhouse gas emissions from international shipping by at least 50%
by 2050 compared to 2008 and if possible, efforts should be pursued towards phasing them out entirely.
There are a multitude of measures that can be used to achieve this. Using biofuels instead of the
conventional fossil fuels is identified as one of the better options.
Biofuels are fuels made from biological material from plants, microorganisms, animals and wastes. Unlike
fossil fuels, biofuels originate from “present-day” photosynthetic conversion of solar energy to chemical
energy. The main problems associated with first- and second generation biofuels is their negative impact
on land-use and competition with food production. Third generation biofuels made from microalgae might
provide a sustainable solution in this respect.
The major advantages of using microalgae as a feedstock for biofuel production compared with terrestrial
crops is their relatively high growth rate and high oil content. Cultivation can be done all year round and
no valuable land has to be used. The multitude of species that are able to thrive in fresh- and salt water
offer plenty of possibilities for scientists with regard to the optimization of the production processes.
The main question of this master dissertation was formulated as follows: ‘Is the use of biofuel made from
microalgae a viable option to reduce the emissions of greenhouse gases from the global shipping fleet
considerably in the coming decades?’. A literature review was performed in order to provide an answer to
this question.
The first sub-question that was asked reads as follows: How are microalgal biofuels produced?
The whole process of cultivation, harvesting and processing the algae to a biofuel is referred to as the
conversion pathway for fuel production. There are several options for each of the steps in this pathway.
Cultivation is typically done in photobioreactors or in open ponds. Closed photobioreactors have a high
biomass productivity, allow for a better control of culture conditions and prevent the introduction of
contaminating living organisms. Open ponds are much easier to construct and to maintain, but the lower
biomass yield and danger of contamination are weaknesses. Cultivation can take place at several locations.
However, the tropical zone has the highest biofuel production potential because of the high average
temperatures and solar irradiance that provide for favourable culturing conditions. Unused desert land or
land not suitable for agricultural use can be utilised for cultivation.
32
Harvesting is basically separating the algae from the culture water. The main harvesting process generally
consists of two steps: thickening and dewatering. This is done to obtain a thick algal slurry to enable further
downstream processes. The obtained algal cell mass can be dried or processed wet. The algal lipids are
then extracted and further processed to renewable diesel via hydrotreating or to FAME biodiesel via
transesterification which is the most common chemical reaction technique in biofuel production. A
process called hydrothermal liquefaction can be used to produce a biocrude.
The second sub-question that was asked reads as follows: Are microalgal biofuels suitable for use in marine
engines?
The answer is affirmative. Marine engines are highly flexible and especially the bigger types that run on
heavy fuel oil can burn a variety of fuel grades. The quality of the fuel can be lower than e.g. aviation fuel,
making production less expensive. It might be possible that some adjustments have to be made to the
engine. This must be first discussed with the engine manufacturer, but costs for these modifications are
expected to be minor.
Tests with pure microalgal fuel and blends on the Maersk Kalmar and the U.S Navy frigate USS Ford proved
to be successful. Results from a study of Hossain et al. (2018) confirm the technical feasibility and indicated
that microalgae HTL biocrude could function as a substitute for HFO and that microalgae FAME is suited
for use in high speed diesel engines without significant changes in engine performance.
A third question that was asked, is: What are the challenges and potentials related to production and
delivery of microalgal biofuels to the global shipping fleet?
There are numerous challenges that will have to be overcome before large-scale cultivation of microalgae
for biofuel will take place.
The main ingredients that are needed to cultivate microalgae are water, CO2, light and several macro- and
micro nutrients. There are however concerns that the supply of some of these resources can be
troublesome for large-scale cultivation. The demand for fresh water could lead to competition with
agriculture. Providing enough nutrients like phosphorous and potassium could lead to depletion of these
resources in the long term. Efficient supply of CO2 to stimulate growth is also an issue. Solutions have to
be found in order to make cultivation of microalgae more sustainable.
Integration of the algal production with wastewater treatment, feeding flue gas with the required CO2
from a nearby power plant, recycling nutrients by anaerobic digestion or hydrothermal liquefaction of the
leftover biomass and offshore cultivation in the ocean are promising methods to enhance the economic
viability and the sustainability of microalgae cultivation. Further research to develop these possibilities are
however required.
33
There is still a lot of uncertainty on how much GHG’s are really emitted during the full life-cycle of
microalgal biofuel. This can differ a lot due to the existence of various production pathways. It is said that
no new carbon is released when burning biofuel from microalgae because the CO2 that is added to the
atmosphere during combustion was taken out of the atmosphere when the algae biomass grew. Well-To-
Propeller studies for microalgal biofuel are not yet published and the existing LCA’s often differ in
outcome.
The biggest barrier to market deployment of microalgae for use as biofuel today are the high cost of
cultivating and harvesting the algal biomass feedstocks. This would be responsible for 50–65% of the total
production cost. Extraction, transesterification, purification and distribution would represent 15–25%, 10–
15%, 2–3%, and 2–3% respectively. The cost for the production of microalgal biofuel reported in the
literature ranges from €0.4 /l – €7.3 /l. The large variability can be attributed to differences in boundaries,
processing pathways, and modeling of either current or future systems. The microalgae productivity is one
of the most important factors in cost estimation, but reported assumptions are highly variable. Laboratory-
scale data is often extrapolated, which is not representative for large-scale application.
The amount of fuel that is consumed by the global shipping fleet today is approximately 300 million tonnes
per year. The evolution of this amount will depend on future growth of the fleet and developments in
energy efficiency of ships. Looking at estimates of future CO2 emissions, they generally tend to forecast an
increase for the coming decades. As CO2 emissions are closely linked to fuel consumption, it is possible
that more fuel will be needed in the future. To provide the bigger ships with fuel, large quantities have to
be delivered in one time.
Today’s global annual microalgae production for food and feed products at a commercial scale is estimated
to be 9 200 tonnes and does not even come close to the required volume for fuelling the global shipping
fleet. Several researchers indicate that the sustainable cultivation of microalgae for biofuel production on
a large scale is not feasible in the short to intermediate term. Providing 300 million tonnes of microalgal
fuel per year to the global shipping fleet in the short term might indeed be a little too ambitious. Aiming
at smaller quantities for use in auxiliary engine could be a more feasible target to strive for. The
International Maritime Organization recently indicated that alternative low-carbon and zero-carbon fuels
should be considered as a measure to reduce GHG emissions from shipping in the short-, mid- and long-
term.
Is the use of biofuel made from microalgae a viable option to reduce the emissions of greenhouse gases
from the global shipping fleet considerably in the coming decades? Today, it is not a viable option.
Researchers indicate that large-scale cultivation of microalgae only for biofuel will not be feasible either
in the short to intermediate term. Microalgal biofuel can be perfectly produced and used on board of ships,
but it is currently too expensive to produce it. As long as the world oil prices remain low, developments
will likely to progress slowly. It is possible that better options to reduce the emissions of GHG’s from ships
emerge and that microalgae will be of no importance anymore. Until that time, all the possibilities should
be examined to realize the IMO’s target for 2050, including the use of microalgal biofuel.
34
The following recommendations follow from this study:
In its search for sustainable greenhouse gas reduction measures, the IMO should consider the conduct of
Well-To-Propeller studies for microalgal biofuel. Even though large production volumes of microalgal
biofuel are not expected to become available in the next few decades, smaller quantities can become part
of the future alternative fuel mix and could possibly be used for propulsion of smaller ships or for use in
auxiliary engines or boilers.
More tests with biofuel made from microalgae on board of seagoing vessels should be done to analyse the
effects on engine performance and possible polluting substances in the exhaust gas composition. This data
will assist the IMO to further develop its greenhouse gas reduction strategy when considering this type of
biofuel.
Further research and development is necessary to find a solution for the expensive production process of
microalgal biofuel and especially the cultivation and harvesting steps need to be optimized. Offshore
cultivation and integration with wastewater treatment should be further developed as these are promising
options to enhance both the economic and sustainable viability.
35
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