1.1 Current situation on fossil fuels and biofuels
In the past decade, the world has been facing critical environmental issues about fossil fuels exhaustion, carbon dioxide emission and also climate changes. Since people realise that fossil fuels will not last longer, then biofuels were introduced into the market. Presently, biofuel is one of the renewable sources, which are effective and efficient in order to substitute fossil fuels. Additionally, biofuels are categorised into 3 generation, including first-generation biofuels, second-generation biofuels and third-generation biofuels. The first-generation biofuels are derived from edible sugar, starch, or vegetable oil. The second-generation biofuels are produced from whole plant or waste biomass sources, which are not direct competition with food supply chain. The third-generation biofuels are derived from algae, including macroalgae and microalgae (Biofuel, 2010). Currently, the third-generation biofuels have not been commercial yet; they are still in experimental stage. However, it is estimated that algae can provide a variety of electricity generation, heating and transport, which are including biodiesel, aviation fuel and biogas. In fact, there are many types of fuels that can derive from algae, and biofuels are the most promising renewable energy for transport sector (Köpke, Noack & Dürre, 2011).
Recently, it is argued that biofuels are the most alternative fuels use for transport sector in the UK, which are derived from agricultural crops (Source). However, the first-generation biofuels are presently competing with food production for land and water resources. It leads people to motivate the search for alternative ways, which is carried out second-generation biofuels and third-generation biofuels. In fact, over 90 % of biofuels used in the UK are imported (Joint Nature Convervation Committee, 2009) and the most biofuels used in the UK are crop-based biofuels rather than second-generation biofuels. Originally, the second-generation biofuels remain more expensive per litre compare to first-generation biofuels and also require a significant capital investment in conversion plants until their production costs are reduced (Sims & Taylor, 2008) The second-generation biofuels is recently not well use as first-generation biofuels, even though the UK biofuels companies tend to take the commercial leap forward by built the UK’s first cellulosic ethanol facility in 2009. It has been running for several years with wide range of feedstock (Chemistry World, 2009). Surprisingly, it is predicted that both generation biofuel will not meet the demand in the future. Since first-generation biofuels have results in a series of problems related to food prices, land usages and carbon dioxide emission and then second generation biofuels suffer with cost effectiveness, technologies and feedstock collection networks (Singh & Olsen, 2011) To meet the future demand with both generation biofuels are argumentative due to various problems, so this leads to propose the third generation biofuels as it has proved that algae are capable of higher yield with lower resource inputs and algae also need less land due to algae can be cultivated in both freshwater and marine water.
1.2 Background on macroalgae-derived biofuel
Algae are a plenty range of aquatic plants. They can be derived by size into two groups that are macroalgae and microalgae. Initially, macroalgae are known as seaweed and they are also a large species of algae, which can be grown in marine water. Microalgae are small microscopic aquatic photosynthetic plants that require the aid of microscope to be seen (Shawn, 2012). Due to the diversity of algae can be derived to bioenergy, many commercial- scale facilities have been developed and try to deploy this third generation biofuels. Since macroalgae is estimated to be around 10 million tonnes reservation in the UK and mostly found in Scotland (Parlimentary Office of Science & Technology, 2011). It presently attracted attention as a possible feedstock for bio-refinery due to massive tonnes of wild seaweed that are available in the UK. However, wild seaweed harvesting alone will need strategy to minimise impacts on coastal degradation, habitat loss and aquaculture. Focusing on macroalgae, there are three types, including green, red and brown algae. Since the important biochemical component to produce biofuels is carbohydrate, which is abundant in macroalgae. For instance, the carbohydrate contents of green, red and brown algae are approximately 25-50%, 30-60% and 30-50% dry weight respectively (Wei, 2013). Corresponding to the climate in the UK, brown macroalgae are found in most of the country due to the low temperature in water, where as green and red macroalgae are familiar in warmer water. As liquid biofuel from macroalgae can effective derive by fermentation processes or known as Acetone-Butanol-Ethanol (ABE) fermentation. This fermentation in both pilot-scale and industrial sector have been successfully performed in various countries such as the United States, the Soviet Union, South Africa and France (Huesemann et al., 2011). The use of macroalgae as a commercial biofuels has not happen yet and the cost of production during the cultivated stage or extracted stage are still high compare to other generation of biofuels.
1.3 The biobutanol as an alternative biofuel for transport sector
Since the biobutanol from macroalgae is attracting research interest and investment in the USA due to its benefits that similar to gasoline more than ethanol. Butanol is mainly produced via chemical synthesis. Other fossil oil derived raw materials uses in the production of butanol are ethylene, propylene and triethyl aluminum or carbon monoxide and hydrogen (Zverlov et al., 2006). However, butanol can also derived from biomass and called as biobutanol. Essentially, both petrobutanol and biobutanol have exactly the same chemical components. The significant advantages of biobutanol that caught research attention is that biobutanol can be blended to any concentration with gasoline for internal combustion engines (Swana et al., 2011). In comparison of low heating value (LHV) of gasoline, bioethanol and biobutanol, it is demonstrated that the LHV of biobutanol is more similar to LHV of gasoline. The LHV of gasoline is 32.3 MJ/L and the LHV of biobutanol is 27.8 MJ/L, or nearly 90% of energy density of gasoline whereas the LHV of bioethanol is 21.3 MJ/L which is only 66% of energy density of gasoline or 34% loss in energy density (Swana et al., 2011). It is obviously that biobutanol is a promising biofuel over bioethanol, which has demonstrated several advantages and cover some bioethanol’s’ drawbacks. It is reported that biobutanol as biofuel has already been use in 2005 by David Ramsey. However, there was an announcement in 2011 that the first commercial biobutanol plant with 420 million litres capacity will be built in Saltend, UK by Butamax (Köpke , Noack & Dürre, 2011). In 2012, Butamax made their public demonstration debut of their biobutanol at the 2012 Olympic Games in London with 24% biobutanol blended into gasoline and also provided fuel containing biobutanol to a fleet of over 5,000 automobiles around the games (Butamax, 2016) It was a huge successful to the public that biobutanol will be the next generation of biofuels.
1.4 Aim and objectives
The aim of this project is to critically assess the biobutanol production in the UK, which only focuses on macroalgae-derived biofuel as it is predicted to become an attractive, economic and sustainable fuel in the near future.
To achieve this aim, the following objectives were identified:
1) To identify the suitable macroalage species for the climate of the UK.
2) To identify the effective biochemical compounds of suitable macroalgae in the UK for biobutanol production.
3) To evaluate the maximum quantity of macroalgae production in the UK by integrated aquaculture concepts.
4) To estimate biobutanol production from macroalgae can produce in the UK.
5) To evaluate the environment impact and energy cost.
This project involves intensive data gathering, analysis and evaluation work, which are based on previous works and studies. It covers and focuses on biobutanol and macroalgae in order to achieve aim of the project.
2. Macroalgae production in the UK
2.1 Wild macroalgae production in the UK
Macroalgae are mainly used for cosmetics, food, animal feed and fertilizer. The majority of macroalgae is currently cultivated in China, where is over 4 million tonnes of only one specie was produced in 2005 (James, 2010) Although, there are fairly small scale cultivations of macroalgae in the UK. Since there are massive available coastlines in the UK, where are suitable locations for wild macroalgae resources. It is found out that the majority of macroalgae is mainly in Scotland and they are in brown macroalgae species due to the UK temperature waters. Moreover, the major macroalgae in the UK are categorised into 2 types, including Laminaria hyperborea and Ascophyllum nodosum. It is reported by the Crown Estate that there are many extensively surveyed by various authors since 1950s and the estimations are significantly difference. However the Institute of Seaweed Research of the Scottish Association (SSRA) was concerned with accuracy of data collection, then they combined data with various authors and got realistic amount, which is show in the table 1.
Table 1. Substantial quantities of Laminaria hyperborea in areas of Scotland by SSRA (Wilkinson, 1995).
Locations Substantial Quantities (tonnes) Area
(Hectares) Length of coastlines (km)
Shetland 619,760 22,680 1,126.3
Orkney 1,219,200 22,680 804.5
Outer Hebrides 711,200 16,605 136.8
Enard Bay 123,952 9,720 257.4
Skye 304,800 7,290 354.0
The reserved estimation of Laminaria hyperborean itself in significant locations is almost 3 million tonnes. However, it can be annually harvested only 6,000 wet tonnes. Furthermore, Ascophyllum nodosum has been expected to have reserves of 110,000 tonnes, but it is predicted to harvest annually at a sustainable rate of 37,000 tonnes (Lewis et al., 2011)
Figure 1: The map shows main locations of wild macroalgae in the UK.
(Lewis et al., 2011)
At this point will be considered on both major types of macroalgae since they are suitable for the UK climate. In order to evaluate the biobutanol production in the UK, there need to identify the effective biochemical compounds in macroalgae.
2.2 Effective biochemical of macroalgae
Generally, biobutanol can be produced by ABE fermentation, which is the anaerobic conversion of carbohydrates by family of Clostridium into acetone, butanol and ethanol (Milledge et al., 2014). Macroalgae have a variety of carbohydrates depending on their species (Jung et al., 2012). Since the majority of macroalgae in the UK are brown algae then the information will focus on carbohydrate composition of brown algae shows in Table 2. Regarding to carbohydrate composition of brown algae in Table 2, there are many types of carbohydrate composition in brown algae. However, brown algae are rich in alginate and contain large amount of laminarin. They also consist of mannitol and few standard sugars (Chen et al., 2014). The various carbohydrates appear in macroalgae presents the high number of various carbohydrates and some of them are easy to convert into sugars, especially mannitol and lammarin (Boonstra, 2014).
Table 2. Carbohydrate composition of macroalgae (Jung et al., 2012).
Green algae Red algae Brown algae
Polysaccharide Polysaccharide Polysaccharide
Mannan Carrageenan Laminarin
Ulvan Agar Mannitol
Starch Cellulose Alginate
Cellulose Lignin Flucoidin
Monosaccharide Monosaccharide Monosaccharide
Glucose Glucose Glucose
Mannose Galactose Cellulose
Xylose Agarose Galactose
Uronic acid Fucose
Glucuronic acid Xylose
In this case, will only consider two types of macroalgae, including Laminaria hyperborea and Ascophyllum nodosum because they predominate in the UK temperature water (Lewis et al., 2011). The important chemical contents for derive biofuels by ABE fermentation are alginate, mannitol and laminarin due to sugar content in each biochemical type (Lewis et al., 2011). These can be explained in the following:
• The alginate is a polymer of a chain of repeating sugar units or also called carbohydrate, which are including mannuronic acid (M) and gluuronic acid (G) (Wilkinson, 1995).
• Mannitol, also known as manna sugar, is a white crystalline solid that taste sweet like sucrose (Wikipedia, 2016).
• Laminarin is a storage glucan that only found in brown macroalgae, generally a linear polymer of glucose (Wikipedia, 2016).
These three chemical types are the effective components of brown macroalgae for biobutanol production.
Table 3. Typical chemical composition of brown algae (dry weight %) (Lewis et al., 2011).
Chemical type Laminaria Hyperborea Ascophyllum nodosum
Alginate 17 – 34 24 – 29
Mannitol 2 – 6 7 – 10
Laminarin 0 – 30 1 – 7
Fucoidan 2 – 4 4 – 10
Ash (minerals) 16 – 37 18 – 24
Crude protein 4 – 14 5 – 10
Crude fibre 10 5
Comparing both Laminaria hyperborea and Ascophyllum nodosum, found out that Laminaria hyperborean is effective more than Ascophyllum nodosum due to the result from extract experiment. Initially, laminarin and mannitol are easy to convert to sugar and there are many types of conversion. However, there was an investigation of brown algae extraction by Kadam et al (2015). Two types of brown algae were investigated by ultrasound extraction medthod. The result of laminarin extraction showed that Laminaria hyperborea were having a higher level of laminarin compared to Ascophyllum nodosum. Yield of laminarin for Laminaria hyperborea extraction was 36.97%, whereas yield of Ascophyllum nodosum was 15.02% (Kadam et al., 2015). Moreover, the anaerobic batch degradation between Ascophyllum nodosum and Laminaria hyperborea were investigated under the same anaerobic batch conditions, which were at 35°C and pH7 by Horn (2000). The result of high concentrations of polyphenols were appear in the batch fermentation, and it was clear that Ascophyllum nodosum has higher concentration of polyphenols than Laminaria hyperborean. The polyphenols concentration resulted in an interception of microbial community, which is effected bacteria performance in the fermentation. Therefore, Laminaria hyperborea is a much better substrate for anaerobic batch degradation than Ascophyllum nodosum due to the lower polyphenols concentration in Laminaria hyperborean (Horn, 2000).
However, there is another investigation of macroalgae, which is optimised the production of mono sugars, including glucose, galactose, mannitol and rhamnose by Jang et al. (2010). The investigation was done by acid hydrolysis as a method with raw materials of macroalgae, including Laminaria japonica (brown algae), Ulva pertusa (green algae) and Gelidium amansii (red algae). Based on the result, it was found that they are good sources for commercial production of mono sugars (Jang et al., 2010). The conversion ratio of biomass to sugar of Laminaria japonica, Ulva pertusa and Gelidium amansii are shown in table 4.
Table 4. The main mono-sugar composition of macroalgae hydrolysateds (adapted from Jang et al., 2010).
Parameters Ulva pertusa
(Green algae) Laminaria japonica
(Brown algae) Gelidium amansii (Red algae)
Mono-sugar Rhamnose Glucose Mannitol Galactose Glucose
Conversion ratio of biomass to sugar (% yield)
Although they are good sources for production of mono-sugars, but brown algae is found in the lowest sugar composition comparing to other algae species. Since the majority of wild macroalgae in the UK is brown algae, which is predicted to be the suitable macroalgae for this project. After the result from Jang et al. (2010), it seems that brown algae might not be the most effective macroalgae for the biobutanol production in the UK. However, this is the primary result from acid hydrolysis method only and the sugar yields of macroalgae are not much difference. In addition, the carbohydrate content in macroalgae sometimes changes seasonally and also depends on the algal growth development (Suutari et al., 2015). For example, brown algae are rich in carbohydrates, consisting of alginate, laminarin and mannitol. It has been reported that the highest carbohydrate content of brown algae is occurred in summer (Schiener, Black & Sranley, 2014) due to the photosynthesis activities increases as available of sunlight in summer. Thus, harvesting macroalgae in the appropriate seasons affect the biochemical composition of the macroalgae and also affect the quality of the macroalgal biomass as substrate for microbial production processes (Kraan, 2010).
2.3 Macroalgae production by integrated concepts
Increasing the macroalgae production by cultivate macroalgae in large scale farms may appear ecological issues. Marcoalgae culture is an extensive system, which depends on a natural nutrient supply. The reliance on natural nutrient supply could deplete coastal waters of nutrients (Phillips, 1990). According to macroalgae farms of scale required would probably not be viable in sea lochs for reasons of nutrient supply and water exchange would be unacceptable as negative environmental impact (James, 2010). The integrated concepts of macroalgae cultivation were introduced regarding the potential to develop macroalgal culture alongside other marine development. For example the adaption of macroalgae cultivation in salmon farms, which is called the Integrated Multitropic Aquaculture (IMTA) concept (Cross & Pearce, 2012) and the adaption of macroalgae cultivation is potentially toward offshore wind farms (Buck, 2009). However, the infrastructure of IMTA concept is still under development in the UK and only in particular countries that already in commercial scale. In following are explained these integrated concepts in details and estimated the maximum macroalgae production for the future with integrated concepts.
2.3.1 The Integrated Multi-Tropic Aquaculture (IMTA) concept
Aquaculture in the UK primarily consists of monoculture units, with emphasis on salmonids and mussels (Barrington et al., 2009). Recently, researchers at the Scottish Association for Marine Science (SAMS), in Oban, have been studying on integrated system as a pilot project to investigating the potential for IMTA along Scottish coastline. The IMTA concept is a form of polyculture that seeks to optimize the energy use within an aquaculture system (James, 2010). Due to many aquaculture systems tend to require huge amount of inputs and then emitting massive amount of waste, so IMTA concept has its goal to make outputs from aquaculture as low as possible. It has been promoted as sustainable and practical alternative to cage aquaculture that could assist to achieve the extension potential of aquaculture (Troell et al., 2003). In the UK, finfish aquaculture is generally conducted near shore and also creating nitrate-rich waste that expands in the local coastal environment. The IMTA can moderate the negative incidences of dissolved nutrients emitting from fish farms by harvesting species those nutrients grown at next sites (Hadley et al., 2015). In other words, it allows one species wastes to be retake as food for other species in the system that has benefits of reduced pollution and increased productivity. Fish farming typically release amount of carbon (C), nitrogen (N) and phosphorus (P) waste into two forms, particulate waste and dissolved waste. The IMTA concept is very flexible and may consist of several species combination, however the example of IMTA concept shows in figure1.
Figure 1. Conceptual diagram of the Integrated Multi-Trophic Aquaculture (IMTA) operation (Barrington et al., 2009).
In the IMTA system, the waste material from finfish aquaculture, consisting of particulate organic nitrogen (PON), particulate organic carbon (POC), particulate organic phosphorus (POP), dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) (Wang et al., 2012). Regarding to figure 1, when fish farming releases waste material, shellfish will absorb particulate waste (PON, POC and POP) and macroalgae will absorb dissolved inorganic nutrients (DIN, DIP). In this project is focusing on only macroalgae as only biofilter component of the IMTA systems that will recap dissolved inorganic waste from fish farming. Moreover, macroalgae can help to maintain clean water quality, which will likely become the new standard for aquaculture as demand continues to rise and the need for environmentally safe practices increases (Schreiber, 2015).
Generally, fish farming is appeared to release approximately 62% of nitrogen, 70% of Carbon and 70% of phosphorus (Wang et al., 2012) in the fish feed that is lost into the environment and also can have negative environmental impacts if appear in high concentrations. Unfortunately, this project is only focused on macroalgae production by cultivate in IMTA systems. In this case, DIN and DIP are only nutrients for macroalgae cultivation due to seaweed cultivation has results in DIN and DIP that can be recaptured to supply oxygen for cultivation on coastal fish farms (Kitadai Y. & Kadowaki S., 2007). There was also a result of DIN concentrations experiment shows that growth increased with increasing DIN concentration (Teichberg, M. et al., 2009). Since macroalgae only uptake DIN and DIP from total release, accounting for 45% of feed N and 18% of feed P (Wang et al., 2012). In other word, the total waste release from fish farming, only 45% of total feed N and 18% of total feed P available for macroalgae to recapture in order to cultivate.
According to aquaculture in the UK, Scotland is certainly the major areas in the production of farmed Atlantic salmon with over 95% of total salmon production in the UK (Department for Environment Food & Rural Affairs, 2015), which dominates the UK finfish production. The map at figure 1, 2 and 3 shows locations of aquaculture sites in the UK. It is obviously that Scotland has the most locations site of aquaculture sites for seawater fish and shellfish. England and Wales are favored of freshwater fish farming, whereas Northern Ireland appears to have a few locations of aquacultures sites.
To estimate the maximum macroalgae production from IMTA concept in the UK, assuming IMTA is adapted into all marine finfish aquaculture in the UK due to macroalgae, Laminaria Hyperborea can only cultivate in seawater. The seawater fish aquaculture in the UK is dominated by most production around the Scottish coast as show in figure 2, with the total production of 158,018 tonnes in 2011 (Williams, 2014). Additionally, the salmon farm industry in England is very small and is also focused on specialist hatcheries rather than food.
Figure 1. Aquaculture Sites in England and Wales
(Department for Environment Food & Rural Affairs, 2015)
Figure 2. Aquaculture Sites in Scotland
(Department for Environment Food & Rural Affairs, 2015)
Figure 3. Aquaculture Sites in Northern Ireland
(Department for Environment Food & Rural Affairs, 2015)
The estimation of maximum macroalgae production is calculated by converting from available of total marine fish production. To produce 158,018 tonnes of marine fish, with feed conversion ratio of 1.25:1 (Jackson, 2012), require 197,522.5 tonnes of feed. Therefore, DIN and DIP release are accounted for 45% of total release N and 18% of total release P. The available of DIN is approximately 55,109 tonnes and DIP is about 24,888 tonnes. The macroalgae productivity can be found by calculate with brown macroalgae yield. However, yields from scaled-up experiences are lacking, especially from Europe, so in this project will use a yield 120 tonnes wet weight of Saccharina Latissima per hectare per year and a value of 15% dry weight (Holdt & Edwards, 2014) since there is only available yield of brown macroalgae. The yields of 120 tonnes wet weight will be assimilate 576 kg N with 3.2% N dry weight (Holdt & Edwards, 2014). The macroalgae production of this yield is approximately 11,480,995 tonnes. In addition, the amount of maximum macroalgae production with 11,480,995 tonnes is done by assuming 100% of nitrogen absorption during macroalgae cultivation.
In comparison, the calculation by James (2010) suggests that 40.3 tonnes of nitrogen will go into environment per 1,000 tonnes of salmon produced and assuming that the nitrogen is between 1% and 2% of dry weight of seaweed with 90% of water content. This could equal to 40,300 tonnes of wet seaweed per 1,000 tonnes of salmon produced (James, 2010). The maximum macroalgae production, which calculated by James concepts, is equal to 6,368,125.4 tonnes. Since there are two amounting different of maximum production, which is accounted for 55.4% difference. It is certainly that the amounts of nitrogen concentrations are difference, which may cause the different output. Since the estimation of macroalgae in report by James (2010) did not put the detail of macroalgae species, which could be red, green or brown algae, so the biochemical will be different and the performance of nitrogen absorption would be different also. In other words, it is obviously that the availability and efficiency of recapture of nitrogen would, in the middle of other things affect final yields.
2.3.2 The integration of offshore seaweed production
Offshore development has been raising attention to many countries, especially in regards to renewable energy sources (Allard, 2009). Offshore aquaculture activities are highlighted as one of the areas, where further growth is possible (Jansen et al., 2016). The use of wind turbines as structures on macroalgae cultivation, likely offer essential benefits. The preliminary advantage of macroalgae offshore cultivation is that there is less competition for agricultural land. However, there is relatively little research into offshore cultivation due to the technical challenges and cost effective. The development of aquaculture facilities in conjunction with offshore wind farms by using wind turbines as structures for seaweed cultivation offer its benefits (Saeid & Chojnacka, 2015). Additionally, the concept of using offshore wind farms for aquaculture is promising, although algae cultivation with economics for this approach needs further investigation (Carlsson et al., 2007).
Figure 4. The concept of multi-use installations for offshore wind and seaweed
(Burg et al., 2013)
According to a report from Sustainable Energy Ireland (SEI) marks that it is currently not known the level of salinity, turbidity and other conditions surrounding wind farms would be able to support algae cultivation as effective production (Roberts, 2012), so this requires further research to prove if it is possible and can be commercial. The idea of offshore wind farm combined with mussel farming and macroalgae cultivation could accelerate the development due to cost sharing (Kapetsky, Manjarrez & Jenness, 2013). In other words, as long as offshore wind farms require frequent visits for maintenance and monitoring. It might possible to schedule routine maintenance of the wind farm alongside maintenance of integrated aquaculture. It is an advantage for other to use marine areas as integrated aquaculture. A figure 4 shows the concept of offshore wind farm cultivation as an idea that offers potential cultivation for the future. Remarkably, the experts interviewed also represented that this concept was deserving of further investigation (Roberts, 2012).
Furthermore, there are a few case studies within this kind of concept by EU-funded research project, known as Innovative Multi-purpose offshore platforms: Planing, design and operation (MERMAID). They are developing the next generation of offshore platforms and also developing a Multi-use offshore platform (MUP), purpose to integrate energy extraction with aquaculture activities (Yttervik, et al., 2015). The project will planning and design MUP to proficiency use ocean space in order to exploiting renewable energy and aquaculture (MERMAID, 2014). Initially, MERMAID has four different infrastructures on sites, including the Baltic Sea site, the transboundary area of the North Sea site, the Atlantic Ocean site and the Mediterranean Sea site (offshore WIND staff, 2014). All sites have four different environmental conditions, which are focused on specific challenges as following:
• The Baltic Sea site is focused on a typical estuarine area between fresh water and marine water.
• The North Sea site is focused on a typical active morphology.
• The Atlantic Ocean site is focused on a typical open deep-water site.
• The Mediterranean Sea site is focused on a typical sheltered deep-water site.
3. The feasibility of biobutanol production in the UK
It is primarily accepted that fossil sources for our energy supply will gradually replace by renewable substrates (Zverlov et al., 2006), especially alternative fuel for transport sector due to rapidly increasing of fuel demands. Biofuels have become an integral part of everyday life in recent society and bioethanol is also a common part of gasoline production. Even though there is presently limited quantities, the intensive pressure on replacing fossil with this biofuels are constantly increasing (Hönig, Kotek & Mařík, 2014). Beside bioethanol production potential as one of capable biofuels, the attempting to other liquid biofuels such as biobutanol as it has benefits that can cover some bioethanol drawbacks. It is also a preferable biofuel and, in longer term, can priduce a significant contribution towards the demand for next generation biofuels. Butanol is a four-carbon alcohol, which occurs in four isomeric structures, from a strighr-chain primary alcohol to a branched-chain tertiary alcohol (Atsumi et al., 2008). Butanol is mainly produced via chemical synthesis and used as a solvent and as a fuel, which are usually also called biobutanol when produced biologically. Since macroalgae are abundant of sugar contents, which are suitable for alcohol fermentation in order to produce biobutanol. In this project will focus on biobutanol production from macroalgae throughout the ABE fermentation and demonstrate the biobutanol production can potentially produce in the UK.
3.1 Biobutanol production from fermentation of macroalgal biomass
Essentially, macroalgae contain higher water content than terrestrial biomass, approximately 80-85% (Kraan, 2010) and also consist of high level of carbohydrates, which are the important biochemical composition for biobutanol production processes. In order to produce biobutanol production as liquid fuel is completed by ABE fermentation. ABE fermentation is usually limited to Clostridium species and Clostridium acetobutylicum represents the model microorganism for biobutanol production (Cheng et al., 2014). Generally, acetate, butanol and ethanol productions from ABE fermentation are in the ratio 3:6:1. It is demonstrated that biobutanol is usually produced the most during ABE fermentation. However, there are prior processes that need to be done before ABE fermentation that are pretreatment of macroalgal biomass, which is hydrolysis of the polysaccharides of macroalgal biomass. As explained in the previous chapter that brown macroalgae are carbohydrate-rich, consisting of laminarin, mannitol and alginate. Therefore, laminarin and mannitol can easily be extracted from milled brown algae for bioconversion (Song et al., 2014), even though
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