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Essays - June 2012

ALGAL BIOFUELS PART I - WHO YOU CALLIN' POND SCUM?

     Back in 2008, when gasoline prices first crested the four dollar mark, the summer essay series focused on petroleum and alternative fuels such as ethanol, natural gas and hydrogen. This year's series will open with a look at an alternative fuel with an intricate tie to water - fuel made from algae, or algal biofuel.

     When most people hear the word "algae" they probably think of seaweed, and the thought of putting seaweed in a gas tank may seem like a crazy notion. But seaweed is only one type of algae, generally referred to as macroalgae, and it is not the primary focus of most research and development in algal biofuels. A majority of current research and development in the field concerns microalgae, microscopic, photosynthetic organisms which live in saline or freshwater environments. (n1) These algae produce lipids (oils) which can comprise as much as 60 percent of their biomass. (n2). However, it is perhaps easier to visualize these microscopic organisms through the oily sheen which often sits atop a body of water in which algae are growing -- what some might refer to as "pond scum."

     It is algae's natural oil, which after being extracted and refined, is being turned into one of the nation's newest types of biofuel. The idea of fuel from algae is not a new one, but it is only now that the possibility is beginning to emerge for a viable and sustainable algal biofuels industry. If you'd like to test what you think you might know about algae-based biofuel before continuing, click on the link below to try out a 20-question quiz.

CLICK HERE TO TAKE THE ALGAL BIOFUELS QUIZ!

Carbohydrates vs. Lipids, Ethanol vs. Biodiesel

     Photosynthetic plants, the basis for most biofuels, use the sun's light, water and carbon dioxide (CO2) to produce carboyhdrates (sugars/starch), oxygen and the molecule called ATP. The starch/sugar in corn or sugar cane, for example, is converted into ethanol through the process of fermentation. Many types of algae, however, contain lipids (oils) which can comprise as much as 60% of their biomass. These lipids are converted to biodiesel by a process called transesterification. Though the chemical processes will not be discussed here, the chart below will give the reader an idea of the types of bioenergy products which can be derived from algae. As stated above, however, it is the ability of microscopic microalgae to produce natural oils which has captured attention as a potential source of biofuel.

Source: Darzins, Al, DOE Algal Biofuels Workshop, Recent and Current Research and Roadmapping Activities: Overview. U.S. Department of Energy, National Renewable Energy Laboratory, Algal Biofuels Technology Roadmap Workshop, December 9, 2008.

     So why even attempt to create biodiesel from algae when ethanol is already the most widely-used biofuel in the world? As a fuel or fuel additive, ethanol has both drawbacks and advantages. In general, the disadvantages of ethanol include the fact that it is lower in energy content per gallon than gasoline, is not shipped by pipeline since it readily mixes with any water which might seep into the the system, is corrosive and in blends greater than about 10% must be used in specially equipped vehicles, and especially in the case of corn ethanol, "is constrained by arable land availability. Competition with food production for land [can] drive possible increases in both ethanol and food prices," (n3) as happened in the U.S. between 2000 and 2008.

     In the U.S., most of the ethanol produced is made from corn. In 2008-2009, corn usage for ethanol was 30% of the overall U.S. crop, up from 23% in 2007-2008 and 11% in 2002-2004. (n4) In the period from 1997 - 2007, annual fuel ethanol production in this country rose from about 1.3 billion gallons to 6.5 billion gallons. (n5) This was due in part to both its inclusion as an oxygenate and MTBE substitute in gasoline as well as a legislated mandate for its use through the Renewable Fuels Standard (RFS).

     The nation's Renewable Fuels Standard (RFS) first became law as part of the Energy Policy Act of 2005, or EPAct. The RFS required increasing volumes of renewable fuel be blended into gasoline in the continental U.S. beginning in 2006. RFS provisions were amended in the Energy Independence and Security Act of 2007 (EISA). According to the provisions of the 2007 law, the amount of renewable fuels required to be blended with gasoline is set to rise from four billion gallons in 2006 to 36 billion gallons annually in 2022. (n6)

     Provisions in the Act distinguish between "conventional biofuel," which is defined as renewable fuel that is ethanol derived from corn (starch), and "advanced biofuel." Advanced biofuel is defined in the 2007 Act as "renewable fuel, other than ethanol derived from corn starch, that has lifecyle greenhouse gas emissions . . . that are at least 50 percent less than baseline lifecycle greenhouse gas emissions. . ." [This] includes ethanol derived from cellulose, hemicellulose or lignin, ethanol derived from sugar or starch (other than corn starch), ethanol derived from waste material including crop residue, other vegetative waste material, animal waste, and food waste and yard waste, [specific types of] planted crops and crop residue . . . and planted trees and tree residue . . ., animal waste material and animal byproducts, slash and pre-commercial thinnings that are from non-federal forestlands . . ., biomass obtained from the immediate vicinity of buildings and other areas . . . at risk of wildfire, . . . separated yard waste or food waste" . . . AND ALGAE. (n7)

     Recognizing both the importance of corn in the nation's food supply and constraints on arable land on which corn can be grown, "even proponents of corn ethanol say that its production levels cannot go much higher than around 15 billion gallons a year." (n8) The amount of conventional (corn) ethanol included in RFS provisions is set to increase gradually to 15 billion gallons per year in 2015, but then is capped at that level annually through the end of the mandated period in 2022. Advanced and cellulosic biofuels are projected to make up the difference in mandated amounts of renewable fuels to be used under the RFS, going from about 2 billion gallons this year to 21 billion gallons in 2022, of which 16 billion gallons must come from cellulosic ethanol. (Cellulose, the main component of plant walls and the most common organic compound on earth, is more difficult to break down than starch and convert to ethanol. However, materials previously "regarded as wastes that required disposal, as well as corn stalks, rice straw, sorghum stalks and wood chips or "energy crops" such as fast-growing trees and grasses, [are now being used as] feedstocks. Cellulosic ethanol . . . ultimately will exponentially expand total ethanol supplies." (n9 ) (You can read more about cellulosic ethanol and ethanol from sugar cane in the 2008 Part III essay).The RFS provisions are outlined in the chart below.

An Old Idea Revisited

     "The study of microalgae represents an area of high risk and high gains . . . Put quite simply, microalgae are remarkable and efficient biological factories capable of taking a waste (zero-energy) form of carbon (C02) and converting it into a high density liquid form of energy (natural oil)."

From "A Look Back at the U.S. Department of Energy's Aquatic Species Program - Biodiesel from Algae," pp. 2 - 3 (n10)

     Interest in algal biofuel doesn't exist only because of its inclusion as an advanced biofuel under the RFS provisions. The notion of using algae as a feedstock for the production of biofuels was first proposed in the 1950s, but the idea was not pursued in depth in the U.S. until the energy crisis of the 1970s. In 1978, then-president Jimmy Carter established the Solar Energy Research Institute (SERI) in Golden, Colorado. The primary purpose of SERI was to examine all potential uses of solar energy, including the use of photosynthetic plants for fuel production. One research area within the SERI was known as the Aquatic Species Program (ASP), and ASP research focused on the use of aquatic plants as sources of energy, particularly species growing in environments unsuitable for crop production. (n11) Though the initial focus of the program was the production of hydrogen from algae, the focus shifted in the 1980s to the production of biodiesel from microalgae, and research continued until funding for the program was eliminated in 1996 during the Clinton Administration. During the 18 years of the ASP's existence, researchers collected and studied thousands of types of microalgae, eventually narrowing the collection to about 300 organisms suitable for biofuel production. The collection of these samples was transferred to the University of Hawaii following the end of the program (where it still remains). In 1998 the above-referenced report was compiled to bring closure to the Aquatic Species Program and summarize the work done over its last 16 years of existence. (You can find the full report online at www.nrel.gov/docs/legosti/fy98/24190.pdf.)

     In the years following the closure of the ASP, research on algal biofuels continued in some locations, though at a much reduced pace and funding level (the Department of Energy under the Clinton Administration had chosen a strategy of more narrowly focusing its limited resources primarily on the development of bioethanol (n12)). Still, interest in algae as a source of biofuels never fully waned (for reasons to be discussed below), and in December of 2008 the U.S. Department of Energy sponsored the National Algal Biofuels Workshop held in Maryland. The outcome of the Workshop was the National Algal Biofuels Technology Roadmap, which was published in May 2010. The document presents information from scientific, economic and policy perspectives to support and guide R&D investment in algal biofuels and identify challenges to be overcome for algal biomass to be used in the production of economically viable biofuels. The Roadmap can be found online at www1.eere.energy.gov/biomass/pdfs/algal_biofuels_roadmap.pdf.

Photo Credit: "Microalgae cultured in southwestern deserts that produce lipids for conversion to biodiesel fuel." Paul Roessler, DOE/NREL, Golden, Colorado. NREL Photographic Information eXchange (PIX) number 01726.

Algae: Why the Attraction?

     If you clicked the link above and took the algal biofuels quiz, then you had a preview of some of the characteristics which have made algae an attractive prospect as a biofuel and which have captured the attention of scientists and investors alike. While the technology for producing and using biodiesel has been know for more than half a century, (n13) in the U.S. biodiesel "is produced mainly from soybeans. Other sources of commercial biodiesel include canola oil, animal fat, palm oil, corn oil, waste cooking oil and jatropha. (n14) [Jatropha is a genus of plants/shrubs which produce oil-rich seeds.] A comparison of oil yields from certain feedstocks as compared to algae is included below.

     Though the figures for algae are based primarily on estimated yields from experimental data, there is no question that many species of algae are exceedingly rich in oil and can grow rapidly, often doubling their biomass within 24 hours. (n15) Other advantages of algae which make them attractive as a feedstock for biofuel include:

• High biomass yields per acre of cultivation

• Minimal competition with land/nutrients associated with conventional agriculture

• The ability to grow in a wide variety of water sources, including waste water, produced water and saline water, thereby reducing the need for freshwater supplies (and opening up the possibility for coupling with wastewater treatment facilities)

• Use of carbon dioxide for growth, making possible carbon recycling from emissions from sources like power plants and industrial sites. (It has been estimated that 100 tonnes of algal biomass can sequester [use for growth] 183 tonnes of carbon dioxide (n16))

• Compatibility with the integrated production of both fuels and co-products within biorefineries (n17)

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