We are also exploring a variety of biomass conversion processes that could be used with non-food based feedstocks such as whole cellulosic biomass, algae feedstocks and cellulose-derived sugars. Algae can provide a diverse and highly desirable non-food source of the important renewable molecules that can be used to produce second generation biofuels. Some strains of algae can be optimized to produce bio-diesel precursors. Other algae strains can be optimized as a source of fermentable sugars, with compositions similar to those derived from corn kernels that are used to manufacture first generation biofuels like ethanol.
Today, ExxonMobil and SGI are carrying out a basic research program to develop advanced biofuels from algae.
Our objective is to develop advanced algae biofuels options and identify the best pathways to make these groundbreaking technologies available to consumers. The program builds off of the many insights we have obtained and the progress we have made since we announced our initial alliance with SGI in The team established a proof-of-concept approach that resulted in the algae doubling its lipid fraction of cellular carbon compared to the parent — while sustaining growth.
Photo — Synthetic Genomics' scientists use advanced cell engineering technologies. Algae has been regarded as a potential sustainable fuel option, but researchers have been hindered for the past decade in developing a strain that is high in oil content and grows quickly — two critical characteristics for scalable and cost-efficient oil production. Slower growth has been an adverse effect of previous attempts to increase algae oil production volume. Limiting availability of nutrients, such as nitrogen, is one way to increase oil production in algae, but it can also dramatically inhibit or even stop photosynthesis, stunting algae growth and ultimately the volume of oil produced.
The ability to sustain growth while increasing oil content is an important advance. Algae has other advantages over traditional biofuels because it can grow in salt water and thrive in harsh environmental conditions, therefore limiting stress on food and fresh water supplies. Oil from algae can also potentially be processed in conventional refineries, producing fuels no different from convenient, energy-dense diesel.
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Oil produced from algae also holds promise as a potential feedstock for chemical manufacturing. Since , ExxonMobil and Synthetic Genomics have been partners in researching and developing oil from algae to be used as a renewable, lower-emission alternative to traditional transportation fuels. Swarup said that while the breakthrough is an important step, the technology is still years from reaching the commercial market.
ExxonMobil and Colorado School of Mines have established a joint research collaboration — led by Mines Chemistry and Geochemistry Associate Professor Matthew Posewitz, who has been working in the algae field for 13 years — focused on developing fundamental new insights into photosynthetic processes and carbon fixation in algae. These new insights will provide better understandings of the scientific and technical challenges involved in producing biofuels from algae.
ExxonMobil has a joint algae biofuels research collaboration with Michigan State, which is focused on advancing the fundamental science of algal photosynthesis. The overall goal of the partnership is to improve the efficiency of photosynthesis in algae in order to increase biofuels production. ExxonMobil has established a joint research program on biomass upgrading processes with the University of Wisconsin. The program is led by Professor George Huber, a leading investigator and innovator in biomass conversion.
The program focuses on converting the initial products of biomass decomposition to more valuable final products. For instance, sugars or sugar-related compounds can be produced from biomass via primary decomposition processes such as fast pyrolysis or treatment with acid and enzymes. This program with Wisconsin is assessing catalytic reactions for transforming these sugars into hydrocarbon fuels, such as gasoline and diesel. We face some significant technical hurdles before biofuels production from algae will be possible at a significant commercial scale.
To overcome these challenges, we are working to answer some basic questions such as:. Reduction of light intensity related to wave length, cell concentration, photobioreactor geometry and distance of the light transmittance.
Algae for biofuels production
Light intensity in photobioreactor related to light way, cell concentration and light which emits by microalgae [ 56 ]. Supplement of CO 2 by bubbles is an important factor to be considered in designs. Injection of CO 2 bases on giving CO 2 to photobioreactor artificially. Researches show that rich ventilation of CO 2 provides CO 2 to algae, supports deooxygenation of suspension, to improve cycling provides mixing and limits the light inhibition [ ].
But high ventilation rate leads to higher cost that is why in large scale of microalgae production it is not recommended. These researches results for microalgae production necessary optimum aeration rate of CO 2 gas. Open and closed culture systems have advantages and disadvantages.
Construction and operation of open culture systems are cheaper and they are more resistant than closed reactors and have large production capacity [ ]. Ponds use more energy to homogenize to nutrients and to utilize the solar energy for growth their water level cannot be less than 15 cm [ 41 ].
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- 1 INTRODUCTION.
Ponds are exposing to air conditions because water temperature evaporation and illumination cannot be controlled. They produce large amounts of microalgae but they need larger areas than closed systems and they are open to other contaminations from the other microalgae and bacteria. Also when atmosphere has only 0. Photobioreactors are flexible systems, which can operate for biological and physiological characteristics of cultured microalgae.
It can be possible to produce microalgae, which cannot produce in ponds. Exchange of gas and contaminants between atmosphere and cultured cells in photobioreactor is limited or blocked by reactor walls [ 39 ].
Making oil from algae – towards more efficient biofuels | Research at Kobe
Depends on the shape and design, photobioreactors have more advantages than open ponds. Culture conditions and growth parameters can be controlled better, it prevents evaporation, reduces loss of CO 2, provides high microalgae density or cell concentration, high yield, creates more safe and preserved environment, prevents contamination. Despite the advantages, photobioreactors have problems to be solved.
Over heating, biological pollution, accumulation of oxygen, difficulty of scale-up, high cost of construction and operation and cell damage because of shear stress and degradation of material in photo phase are main problems in photobioreactors [ 39 ]. Comparing photobioreactors and open ponds is not easy because growth of algae related to al lot of different factors.
Three parameters are considered in algae production units for yield [ 41 ]:. Photobioreactors can be operated in batch or continuous process. There are a lot of advantages for using continuous bioreactors than batch bioreactors. Continuous bioreactors provide more control than batch bioreactors. Growth rates can be regulating in long time periods, can be saved and with variable dilution rates biomass concentration can be controlled.
With steady state continuous bioreactors results is more dependable, products can be easily produced and can be reached desired product quality.
Continuous reactions offer many opportunities for system research and analysis [ ]. But some type of bioreactors is not suitable for continuous process. For some productions, cell aggregation and wall growth can inhibit the steady state growth. Another problem is loss of original product strain in time. Mixtures viscosity and heterogenic nature make difficult for maintaining filamentous organisms.
Long growth periods increase the contamination risks [ 83 ]. There are several ways to harvest microalgae and dry them. Some main harvesting methods are sedimentation, flocculation and filtration. Sedimentation : When a particle moves continuously in a phase, the velocity is affected by two factors. First of them is increasing the velocity because the density gradient between particle and fluid create buoyant force.
At the end, buoyant force gets equal to dragging force and particle starts moving with a constant velocity. The same idea is applied to collect microalgae from the ponds. Gravity force is used for settling of suspended particles in fluid. This method is cheap and easy. However, the particles suspended in the fluid have to be incompressible. The problem with the Scenedesmus sp.
That is why sedimentation cannot be used for these types [ ]. For low value products, sedimentation might be used if it is improved with flocculation [ ]. Flocculation: is also used for harvesting microalgae. The general idea is microalgae carries negative charge on it and if the flocculants disappear the negative charge, algae starts coagulation. Filtration: This is one of the most competitive methods for the collection of algae.
There are different types of filtrations, for example, dead end, microfiltration, ultrafiltration, pressure filter and vacuum filter.
Mostly filtrations require the liquid media with algae to come through filtration. Filter can be fed until a thick layer of microalgae is collected on the screen. This method is very expensive for especially microalgae. The pore sizes of the filters are the most important part. If the pore size is bigger than algae you cannot collect it. In contrast, if the pore size is too small it might result in decrease of the flow rate and block the pores [ ].
There are a lot of methods for extraction of lipid from microalgae but the most common techniques are oil presses, liquid-liquid extraction solvent extraction , supercritical fluid extraction SFE and ultrasonic techniques. Oil presses are usually used for extracting of lipids from nuts and seeds. The same process and devices can be used for lipid extraction from microalgae. For the purpose of this process to be effective, firstly microalgae must be dried.
Presses use pressure for breaking cells and removing oil [ ]. Solvent extraction is more successful for extracting lipids from microalgae. In this method organic solvents such as hexane, acetone, and chloroform are added in the algae paste.