Many companies are currently engaged in algae-based biofuel research, but players with large-scale production abilities are still few. According to a recent article (Jacquot, 2009), the leading companies in this field are Algenol Biofuels, Sapphire Energy, Seambiotic, Solazyme, and Solix BioSystems (ordered alphabetically). Mass cultivation to offer algae biomass as starting materials is critical to these algae-based biofuel companies. Based on the information on the Websites of these five leading companies, they all developed their proprietary and spe­cialized cultivation methods (see Table 2.3), including photobioreactor systems, open pond systems, and fermentation systems.

Algenol developed a technology, known as Direct to Ethanol®, to produce ethanol from cyanobacteria. Two central components in this technology are gene-modified cyanobacteria and a flexible plastic-film photobioreactor. The genetically modified cyanobacteria can overexpress fermentation pathway enzymes and enhance the ethanol production (see Figure 2.5). The photobioreactors Agenol uses are constructed of flexible plastic film. Each photobioreactor consists of ports for ethanol collection and the introduction of CO2 and nutrients, a mixing system, and ethanol collection rails (see Figure 2.6). Therefore, Algenol claims that they produce biofuel directly from the algae without killing or harvesting the creatures.

Solix also uses photobioreactors to cultivate algae, and they have named their system the Lumian Algae Growth System (AGS ). The AGS system comprises a network of thin panels held in a shallow water bath. The commercialized AGS system is the Lumian AGS4000, which is a 4,000-liter cultivation system with 20 200-liter Lumian panels held in a 12 x 60-foot water — filled system (see Figure 2.7). Furthermore, this system is integrated with a support system for

Company Founded Name Time Location Biofuel Type Technology Cultivation Equipments Market
Algenol 2006 Biofuels	Algenol’s patented technology (known as Direct to Ethanol® Technology) enables the production of ethanol for less than $1.00 per gallon and targets commercial production of 6,000 gallons of ethanol per acre per year. Algenol selects cyanobacteria strains and enhances their ability to produce ethanol by overexpressing fermentation pathway enzymes, allowing each cell to channel carbon into ethanol production. Algenol uses a proprietary photobioreactor system to cultivate cyanobacteria and collect ethanol. The method involves a marine strain of algae and therefore can use seawater. It also has the added benefits of consuming carbon dioxide from industrial sources and not using farmland.	Algenol’s proprietary flexible plastic film photobioreactor (PBR). Capital costs to construct its patented facility will range between $4.00 and $6.00 per annual gallon of capacity. A pilot-scale integrated biorefinery in Florida on 36 acres was broken ground in 2011.	Algenol intends to produce 1 billion gallons annually by 2012. The company says its production costs will be less than $1.00 per gallon (sale for $3.00 per gallon). Algenol’s goal is 20 billion gallons per year of low — cost ethanol by 2030.
Florida, USA Ethanol
Sapphire 2007 Energy	Headquarters in San Diego, USA; green crude farm in New Mexico, USA	A liquid that has the same composition as crude oil	Sapphire produces "green crude," a liquid that has the same composition as crude oil. The company has shown that its fuel can be used in	The company uses open ponds, raceway. The test site in Las Cruces, NM, at 22 acres, has more than 70 active ponds, varying in size from	The first phase of Sapphire’s Green Crude Farm was operational in August 2012. When completed, the facility will produce 1.5 million

Company Founded Name Time Location Biofuel Type Technology Cultivation Equipments Market
two commercial flights (Continental and JAL airlines) and a cross­country road trip (Algaeus).	14-foot test ponds to 300- foot, 1-million-liter production ponds. The green crude farm located in Columbus, NM, will have 300 cultivated acres.	gallons per year of crude oil and consist of approximately 300 acres of algae cultivation ponds and processing facilities. The plan is to make 1 million gallons of diesel and jet fuel per year by 2011, 100 million gallons by 2018, and 1 billion gallons per year by 2025. Seambiotic’s Algae Plant in China was finished in late 2011 with raceway ponds on approximately 10 hectares. Seambiotic believes that this plant is able to produce enough algae biomass to convert into fuel at prices competitive with traditional fuel by 2012.
Biodiesel and bioethanol	Seambiotic grows microalgal cultures in open ponds using flue gases such as carbon dioxide and nitrogen from a nearby coal plant as feedstocks. The 1,000-square-meter facility produces roughly 23,000 grams of algae per day. Three tons of algal biomass would yield around 100 to 200 gallons of biofuel.
Seambiotic 2003	Israel	Open ponds, raceway.
South San Francisco, USA	Solazyme’s proprietary microalgae are heterotrophic, grow in the dark in fermenters, and are fed plant sugars.	Standard industrial fermentation equipment.	In 2010, Solazyme delivered over 80,000 liters of algal-derived biodiesel and jet fuel to the U. S. Navy. Subsequently, Solazyme was awarded another contract with the U. S. Department of Defense for production of up to 550,000 additional
Biodiesel
Solazyme 2003

Company Founded Name Time Location Biofuel Type Technology Cultivation Equipments Market
liters of naval distillate fuel. Solazyme went public (IPO) in 2011 at $18 per share and raised $198 million in the process. In 2012, Solazyme expected to archive a 2-million-liter annual capacity. Solix’s demonstration facility performed at over 3,000 gallons of algae oil per acre per year in 2010.
Solix 2006 Colorado, Biodiesel BioSystems USA	Solix uses a proprietary closed photobioreactor system and claims that the system can produce up to seven times as much biomass as open-pond systems. The algal oil is extracted through the use of chemical solvents such as benzene or ether. Solix is also collaborating with the Los Alamos National Laboratory to use its acoustic-focusing technology to concentrate algal cells into a dense mixture by blasting them with sound waves. Oil can then be extracted from the mixture by squeezing it out; this makes the extraction process much easier and cheaper, obviating the need for chemical solvents.	Photobioreactor system includes Solix’s proprietary Lumian panels, Solix Lumian Algae Growth System (AGS™). Solix’s demonstration plant has three algae cultivation basins totaling 3/4 of an acre (0.3 hectares). The plant has over 150,000 liters of algae under cultivation.

FIGURE 2.5 The process of Algenol’s Direct to Ethanol® technology (www. algenolbiofuels. com/media/media- gallery).

media preparation, harvesting, reinjection, and system cleaning. Before 2009, the introduction of the Lumian AGS system especially mentioned the vertical orientation of panels that can provide "extended surface area." However, according to the pictures on Solix’s Website, the panels now are horizontally arranged. The AGS panels contain tubes that deliver CO2 as a carbon source and deliver air to remove oxygen (a byproduct of photosynthesis). According to an article of the IOP Conference Series in 2009 (Willson, 2009), the marginal cost of large-scale production using the AGS system was approximately $1/liter ($150/barrel), with a defined path of reducing the production cost by half over the next two to three years.

Sapphire and Seambiotic both choose raceway open ponds to cultivate their algae. Sapphire releases very little technology information about its process: "We grow the algae in open ponds with only sunlight, CO2, and nonpotable saltwater in deserts" (see Figure 2.8a). Seambiotic also grows microalgal cultures in raceway open ponds using flue gases carbon dioxide and nitrogen from a nearby coal plant as the feedstock (see Figure 2.8b). Seambiotic has carried out an R&D pilot study comprising about a 1,000-meter square of ponds in an Israel power plant to use the flue gas to cultivate algae. Both companies emphasize the low cost of using open ponds and choose marine algae strains to reduce biotic contamination.

Solazyme’s algal cultivation method is much different from those of the previously men­tioned companies. Solazyme uses large fermentation tanks to incubate algae in the dark and feed them plant sugars. This platform makes the feedstock more flexible, and it is able to use

2.5

COMMERCIAL MICROALGAE CULTIVATION SYSTEMS FOR BIOFUEL PRODUCTION

FIGURE 2.6 The flexible plastic film photobioreactors used by Algenol; A) the structural diagram, B) the appear­ance (www. algenolbiofuels. com/media/media-gallery).

low-cost sugars, varying from sugarcane to corn stover, woody biomass, switchgrass, and other cellulosic materials. By this heterotrophic incubation, algae can accumulate more oil in cells. According to data shown on Solazyme’s Website, the oil content in the company’s algae cells is in excess of 80% (see Figure 2.9). Considering that the average wild alga yields only 5-10% oil content, this enhanced yield is very critical to lowering the production cost of biofuels.

The Solix Lumian AGS4000 system (www. solixbiofuels. com/content/products/lumian-ags4000).

FIGURE 2.8 (a) Sapphire’s green crude farm with raceway open ponds (www. sapphireenergy. com/rendition. medium/images/multimedia/green%20crude%20farm%20ponds. jpg). (b) Seambiotic’s pilot plant (www. seambiotic. com/uploads/Seambiotic%20Ltd.%20-%20Algae%20Pilot%20Plant%20white%20paper. pdf).

2.6

CONCLUSIONS

FIGURE 2.9 Solazyme’s heterotrophic algae cultivation platform (http://solazyme. com/technology).

2.3 CONCLUSIONS

Production of biofuels and other products from microalgae requires a massive amount of microalgae biomass. Effective cultivation technology for large-scale microalgae biomass pro­duction is of great importance in the commercialization of the microalgae-based industry. The growth of microalgae is greatly influenced by environmental conditions, such as light supply, temperature, CO2 supply, and so on. Therefore, an appropriate operating condition to create optimal conditions should be applied for microalgae cultivation. Moreover, the design and configuration of cultivation systems and photobioreactors also play a pivotal role in the mass production of microalgae biomass.

Toward that end, various open and closed cultivation systems have their own pros and cons. In general, closed systems provide better stability and cultivation efficiency, whereas open systems are much cheaper and easier to scale up. As a result, selection of a suitable cul­tivation system is highly dependent on the characteristics of the target microalgae species as well as the climate and environmental conditions of the cultivation site. In addition, since out­door cultivation of microalgae is inevitable for commercial applications, people need to cope with the challenges and limitations arising from the natural environment, such as the avail­ability of sunlight, the limitation of CO2 and nutrient sources, and variations in ambient tem­peratures. Furthermore, a cost and life-cycle analysis should be performed on the developed process to assess economic feasibility as well as environmental impacts.