Figure 3. Aquaculture Sites in Northern Ireland (Defra, 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 much 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.
In addition, an idea of IMTA concept actually can use with both saltwater fish aquaculture and freshwater fish aquaculture. It appears in figure 1 that mainly aquaculture in England and Wales have been flavor with freshwater fish aquaculture than seawater fish aquaculture. Considering freshwater fish, it also has potential to adapt with IMTA and can produce more macroalgae as it may be an optional choice to get more macroalgae production as much as possible. Even though, this report is focused on marine macroalgae production in the UK, if there is a change to pursue more macroalgae production by adapting IMTA concept with freshwater fish aquaculture in the UK. It would be better for the future of macroalgae-derived biofuel to have many chances to derive as much as possible. To estimate the macroalgae production potentially from freshwater fish aquaculture in the UK, assuming all the conversion and nitrogen absorption are same as saltwater fish aquaculture. From Facts & figures sheet by the marine Socio-Economics Project (MSEP), showed that freshwater fish productions in 2012 are accounted for 11,276 tonnes (Williams, 2014) and 97% of total freshwater fish productions are rainbow trout. With the same condition and calculation as saltwater fish aquaculture, the maximum macroalgae production by adapting IMTA concept in all freshwater fish aquaculture in the UK, then they will able to produce 819,271 tonnes of macroalgae. Comparing to macroalgae production by adapting IMTA system with saltwater fish productions, the production from IMTA with freshwater fish aquaculute are much lower due to the freshwater fish productions are not major market in the UK. Additionally, it is well known that Scotland is dominated by saltwater fish aquacultures and massive salmon productions are commonly exported to the USA. The salmon markets are increasing every year (Department for Environment Food & Rural Affairs, 2015). In contrast, English finfish aquaculture has not developed as same level as Scottish. Moreover, trout farms in the UK have no major centre or hub and the salmon farming in England is really small due to focusing on specialist hatcheries rather than food producers (Williams, 2014).
3.3.2 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).
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).
Figure 4. The concept of multi-use installations for offshore wind and seaweed
(Burg et al., 2013)
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.
However, there are no public authorities at national level and no plans by the national government have decided to realise MUP in the Baltic Sea, Atlantic Ocean and Mediterranean Sea. While MERMAID project has brought wind energy sector and aquaculture sector together in order to learn and discuss MUP (Stuiver et al., 2016). Various government agencies have been associated in the process as well, but there still is much hesitancy to invest in MUP. Due to the oscillation of the offshore wind sector to invest MUP, the Dutch government is exploring risks and opportunities to prepare for potential legal regulations such as opening up wind farm areas for co-use (Stuiver et al., 2016). For instance, there is MUP case at North Sea site that represented in EWEA Offshore 2015 in Copenhagen. It is estimated of 1,000 MW offshore wind farm, consists of 100 units of 10 MW wind turbine. The design layout shows in figure 5 and the estimation of the annual salmon production is predicted to be 60,000 to 70,000 tons and accounts for 73-85% of electricity yield for this case (Yttervik, et al., 2015).
Figure 5. Layout of MUP case at North Sea site (Yttervik, et al., 2015).
To estimate the macroalgae production in the UK by the multi-use offshore platform (MUP), regarding to the previous estimation by Yttervik et al., 1,000 MW installations of offshore wind turbines can produce 60,000-70,000 tonnes annually. Since there are 5,053 MW installed in the UK with 1452 turbines (Wikipedia, 2016: the Wind Power, 2016), which can theoretically produce 353,710 tonnes of salmons per annum by MUP concept. This can be estimated the macroalgae production by using calculation as same as IMTA concept, which assume that salmon release waste material, consists of nitrogen and phosphorus. Then the maximum macroalgae production can produce in the UK by integration of offshore wind farm is approximately 25,699,242 tonnes per annum. However, there was a study that showed the difficult operation of fish aquaculture in the North Sea during each season and the relative shallowness of the southern North Sea does not allow fish cages to be submerged due to the compensation for temperature conditions (Jansen et al., 2016). There are also argument about the placing fish cages within the offshore wind farm might cause conflict within the operation and maintenance and also conflicts between the offshore wind turbines operation and aquaculture farms during their installation (Yttervik et al., 2015). Even though the maximum production potential is massive, there will face lots of issues, as it is very sensitive with environmental impacts, operations, infrastructures and its regulations. Nevertheless, the integration of offshore wind farms with aquaculture activities need more investigation in order to prove that it is reliability for technical and economic feasibility. To attract investors, it is current uncertain due to a level of development and it requires considerable strategies to make it happen for commercial scale. It still needs more researches and analysis to be done and proved. This case study presents promising example of future innovative multi-use offshore wind farms with aquaculture.
To conclude, there are many ways to harvest and cultivate macroalgae, although for this study will only count the macroalgae production from wild macroalgal harvesting and the Integrated Multi-Tropic Aquaculture (IMTA) concept, accounting for 11,486,995 tonnes annually as a maximum production potential. The macroalgae productions from integration of multi-use offshore platform (MUP) and IMTA concept with freshwater fish aquaculture will not be considered in this project. The integration of MUP needs more development, since it is designed to locate in offshore wind farm area, which is difficult to access. Comparing IMTA concept and MUP concepts, it is appeared that IMTA is more capable to achieve and adapt to the UK culture even though there are lots of offshore wind farms in the UK. Additionally, there are lots of successful of IMTA concepts in many countries since this concept is one of a traditional aquaculture system in Asian countries like China, Korean and Japan. Although there are a few pilot studies in the UK, it will increase due to its benefits compare to mono-aquaculture. The integration of MUP is quite new to the market and still under development, even though there are some supports by European Union due to MUP concept provides opportunities for more effective use in marine areas and also provides environmentally solutions to take advantages by offshore wind farm areas. The MUP technologies were seen as a challenge, but there are lots of issues that need to clarify and it is currently not attract investors that much, so it need more time to create solutions in order to solve difficulties with development and implementation of MUP (Stuiver et al., 2015). Moreover, the macroalgae production from fresh fish aquaculture is not considered in this project due to the fish farming conditions are difference, even though some macroalgae can be cultivated in freshwater, but macroalgae are more likely to grow well under marine environmental condition. In calculation amount of macroalgae production by IMTA concept between saltwater fish aquaculture and freshwater fish aquaculture, estimated productions are too different, since the production of freshwater fish is not the major aquaculture and they do not have hub in the UK, otherwise the saltwater fish aquaculture like salmon is the major production in the UK. It is more likely to adapt IMTA concept to saltwater fish aquaculture, since they have been many pilot cases in the UK, but there is none of IMTA concept with freshwater fish aquaculture yet.
4. 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 & MaÅ™Ãk, 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 produce a significant contribution towards the demand for next generation biofuels. Biotanol (C_4 H_10 O) or butyl alcohol 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. Biobutanol is similar to ethanol and can be made from the same kind of raw materials like sugar, starch or lignocellulosic. 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 maximum biobutanol production can potentially produce in the UK.
4.1 Biobutanol production by 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. Biobutanol is generally produced by the fermentation of carbohydrates in a process known as ABE fermentation. Currently, many researchers are interesting in biobutanol production from biomass, which has led to the re-experimentation of ABE fermentation again (Ezeji et al., 2007) due to this type of fermentation had been decline since around 1950s by raising of substrate costs and the availability of low-priced feedstock, which was for petrochemical industry (Du ̈rre, 1998). However, the current situation has been changed. Fossil fuels will not last longer and petroleum prices are recently not cheap as the past and an effort towards the increasing for production of butanol from biomass had steadily been progressing (Jang et al., 2012). ABE fermentation is usually limited to Clostridium species and Clostridium acetobutylicum represents the model microorganism for biobutanol production (Cheng et al., 2014). Interestingly, there is a data, demonstrate by the Department of Energy (DOE) Joint Genome Institute that not only Clostridium acetobutylicum is the most effective as a commercial valuable bacterium for ABE fermentation, but recently one of Clostridium spp. called Clostridium Beijerinckii also has the potential for utilization of a wide variety of carbohydrates (Chukwuemeka Ezeji, et al., 2007). Clostridium species are essentially known to have ability to utilise sugar contents, including pentose and hexose, CO_2,H_(2 ) and CO (Jang et al., 2012). In other words, Clostridium spp. encourage to breakdown polymeric carbohydrates into monomeric carbohydrates, although only some Clostridium spp. that are able to produce acetone, butanol and ethanol (ABE) by anaerobic fermentation (Wal et al., 2012) . Recently, the solventogenic clostridia have earned lots of attention due to their ability to produce industrially relate to chemicals such as acetone, butanol, ethanol and others (Chukwuemeka Ezeji, et al., 2007). Macroalgae are consisted of a mix of different sugar contents, these microorganisms then are expected to efficiently convert most of sugar contents into an ABE mixture, which are acetate butanol and ethanol (Wal et al., 2012). 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 is 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). The increasing for biofuels yield needs to be improved. In other words, hydrolysis of macroalgae undoubting helps to extract sugar contents easily but this process still need to increase degradability due to economic aspect.
The biorefinery concept of biobutanol production from macroalgae is concluded in figure 6. These processes are primary steps to produce biobutanol, which is represented by researchers in Netherlands. The experiment was done for a biorefinery of Saccharina latissima. Even though Saccharina latissima is not the major type of wild marcroalgae in the UK, both Saccharina latissima and Laminaria hyperborea are brown algae and they have similarly contents. Then, the vision of a biorefinery for Saccharina latissima by Lopez-Contreras et al. (2013) would be considered as typical process for this project. The scheme of processing steps are described by Lopez-Contreras et al. (2013) explains in the following:
The first step starts with a chopping and pressing step. The purpose of step is to separate mannitol from the fraction of macroalgae carbohydrates. In other words, this step is to split solid and liquid that remaining from chopping and pressing step.
Then pressing stages of fresh macroalgae, press cake and press juice are in this stage, but do it separately. The press cake is for extract laminarin and fucoidan from solid material remaining into liquid. This stage is defrosted and milled under liquid N_2 to obtain small piece. The press juice is to extract dissolved substances, mannitol by centrifuges macroalgae to remove impurities and then subsequently evaporated in order to make macroalgae drying. Interestingly, pressing juice could possibly obtain 71% of the mannitol present in the press juice (Lopez-Contreras et al., 2013)
The hydrolysis stage is to hydrolysed under mild acidic conditions to obtain for fermentable sugar origination from laminarin and fucoidan.
The products of sugar content, mannitol, laminarin and fucoidan can be converted by ABE fermentation to produce acetone,butanol and ethanol (ABE).
Figure 6. Biorefinery design of processing steps described in this study, adapted from Lopez-Contreras et al. (2013).
The result of experiment by Lopez-Contreras et al. appeared that Clostridium acetobutylicum in fermentation of glucose and mannitol mixing produce 1.1 g/L of ABE, while on culture on 20 g/L of glucose the ABE was 3.4 g/L. In comparison, another species of microorganism called Clostridium beijerinckii in fermentation of glucose and mannitol mixing can produce up to 6.6 g/L of ABE after 163 hours of cultivation, while on culture on 20 g/L of glucose as carbon source this strain produce 7.8 g/L of ABE. They concluded that the difference in fermentation performance due to the properties of the feedstock and typical of bacteria strains. They also indicated that not all sugars were comsumed during fermentation (Lopez-Contreras et al., 2013). Since Clostridium acetobutylicum is well known as the most well-studies and widely in used, even though Clostridium beijerinckii has been used due to its good in results. It seems that Clostridium beijerinckii is more likely to ferment sugar better than Clostridium acetobutylicum, regards to the results of ABE.
In comparison, the study by Huesemann et al. (2011) was also investigated macroalgae, especially brown algae. The study was about the potential for biochemical conversion by Clostridium acetobutylicm to produce butanol and others. Their experiment was investigated as for Saccharina spp., which is the same specie in Lopez-Contreras et al. experiment. Their experiments were under 6 different conditions to study the fermentation of individual substrate, including glucose and mannitol at low concentration and high concentration, glucose and mannitol mixing and brown algae extract of glucose, mannitol and laminarin. The maximum concentration of butanol from their investigated was 7.5 g/L. This maximum concentration of butanol was done by 140 hours fermented guclose and mannitol with 35.1 g/L and 32.5 g/L, respectively. The biobutanol yield in this experiment is equal to 0.12 g biobutanol/g sugar. Comparing to other 5 experimental results in biobutanol yields, this 0.12 g biobutanol/g sugar, they remarked that this yield is being the most comparable in the fermentation of mannitol or mannitol and glucose mixing. They are stated that free glucose, laminarin-derived glucose and mannitol were major macroalgal fermentation substrates. However, Clostridium spp. is able to produce products from many carbon substrates, including acetone, butanol, ethanol and others during fermentation, but it is not able to use all of carbohydrates that present in macroalgae.
Furthermore, the study by Wal et al. (2012) was investigated the production of acetone, butanol and ethanol, but using green macroalge, Ulva lactuca instead of brown algae like both previous studies. In this case, they used two of the best-characterised ABE-producing strains, which are Clostridium acetobutylicum and Clostridium beijerinckii. Since green algae have a few different biochemical compositions to brown algae, the difference is only type of sugars. In green algae, major sugar contents are Glucose, Xylose and Rhamnose. One of significant result was Ulva lactuca with Clostridium acetobutylicum able to produce ABE up to 18.1 g/L under hydrolysate supplemented with glucose and xylose condition, especially 11.4 g/L of biobutanol production. They stated that mostly because of glucose fermentation, which was available 54.3 g/L at the beginning of fermented process. In comparison, Ulva lactuca with Clostridium beijerinckii are able to produce only 9.2 g/L of ABE or 6.8 g/L of biobutanol under the same condition. Additionally, the ABE yield is approximately 0.3 g ABE/g sugar, or 0.18 g biobutanol/g sugar.
Overall, there are similarly results from those experiments as can be seen as ABE yield or biobutanol yield. For the study by Huesemann et al. (2011), they predicated that the most comparable of biobutanol yield is 0.12 g biobutanol/g sugar and the study by Wal et al. (2012) showed that the biobutanol yield from their experiments are around 0.18 g biobutanol/g sugar, which are quite similar to the result by Huesemann et al. (2011). Although their study used different species of macroalgae, brown algae and green algae. The species of macroalgae do not seem to significantly affect the final of biobutanol yield, since the end of the process Clostridium spp. will be able to utilise sugars. Even though some species will not be able to utilise all of sugars that indicate in macroalgae.
4.2 The estimation of biobutanol production potential in the UK derived from macroalgae
Currently, biobutanol is the preferable solvent due to the highest price in the chemical market. The commercial solvent titres peak at approximately 20 g/L of ABE with 60 g/L of substrate. The ABE yield around 0.35 g ABE/ g sugar or 0.21 g biobutanol/ g sugar (Green, 2011). This commercial concentration and yield did not use macroalgae as feedstock at the first place. Although, the attraction put researcher efforts to use abundant of carbohydrates, that are available in macroalgae for the production of biobutanol. There are studies by many researchers showed the biobutanol production yields from macroalgae derived. For instance, the study by Huesemann et al. (2011) demonstrate the biobutanol production yield of about 0.18 g biobutanol/g sugar and also the study by Ellis et al. (2011) stated their highest ABE production yield of 0.311 g ABE/g sugar or 0.249 g biobutanol/ g sugar. This yield was their highest yield throughout their study after all. Considering the biobutanol production yield to estimate the biobutanol production from macroalgae, it appears the similarly yields as explained previously. The recent technology and wide range of Clostridium spp. can able to utilise sugar contents in macroalgae in highest yield of approximately 0.20 g biobutanol/ g sugar. To estimate the biobutanol production potential in the UK by using macroalgae, assuming biobutanol production yield from macroalgae is 0.20 g biobutanol/g sugar. Since the estimation of macroalgae production potentially can produce in the UK is around 11,486,995 tonnes annually. The majority of macroalgae in the UK are brown macroalgae then in this case assuming the macroalgae production are brown algae in order to find the amount of carbohydrates that available to convert into biobutanol production throughout ABE fermentation. The potential of macroalgae to produce biobutanol can be calculated based on the assumption. For instance, referring to Lopez-Contreras et al. (2013) as based assumption of brown macroalgae. If dry weight carbohydrate content is 66.3 %, then it is estimated that there is a 90% conversion ratio to biobutanol. By fermenting 1 g of sugar, can obtain 0.2 g of biobutanol. One kg dry weight macroalgae biomass therefore corresponds to approximately 0.119 kg or 0.119 L biobutanol. Since the moisture content in macroalgae is about 80%, then dry weight of macroalgae production potential in the UK will be around 2,297,399 tonnes per annum. The maximum potentially biobutanol production in the UK under the estimation is approximately 273,390 L per annum. In 2014/15, UK bioethanol consumption placed at approximately 800 million litres, which accounts for 4.6% of all petro sales by volume (UKPIA, 2015). Comparing the estimated biobutanol production to the bioethanol consumption in the UK in 2014/15, the production potential does not seem to be a significant figure. In other words, the amount of biobutanol production from macroalgae production in this study will not be enough to substitute biofuel used presently in the UK.
However, this is a primarily estimation with present technology and conversion by ABE fermentation. It is required more to develop the biochemical conversion, since the current microorganisms would not be able to utilise all carbohydrates that present in macroalgae and the current pretreatment could not break down all polysaccharides into monomers (Ghadiryanfar et al., 2014) before fermentation. It is a challenge to increasing the efficiency of conversion into biobutanol. If this challenge is succeed, the production of biobutanol from macroalgae production may be noticed and realised as one the effective alternative biofuel that can be used to supply instead of fossil fuels.