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Algae Fuel: Expert Q&A

On August 28, 2009, Kris Niyogi answered selected viewer questions about algae, biofuel, and more.


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Q: Are algae plants or something else? Theodore, Cleveland, Ohio

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Kris Niyogi: Algae are a very diverse group of organisms that are a bit difficult to define. Historically, they have often been grouped together with plants, but only one group of algae, the green algae, are very closely related to plants. Many algae, such as kelps and diatoms, are just about as distantly related to plants as humans are.

In a broad sense, algae can be defined as simple photosynthetic organisms that use sunlight to convert water and carbon dioxide into sugars and oxygen. This definition includes cyanobacteria, formerly known as "blue-green algae", which were the first algae to evolve more than 2 billion years ago, but it excludes plants, which generally have more complex organs and reproductive structures.

Q: Besides producing oil, what other hidden talents do algae have? Jessica D, Los Angeles, California

Niyogi: Algae are incredibly important to our global ecology and biogeochemistry. More than two billion years ago, the production of oxygen by cyanobacterial photosynthesis dramatically changed the Earth's atmosphere and enabled the evolution and diversification of complex organisms that breathe oxygen (like us!). Although they are not as conspicuous as plants in our everyday lives, algae in the ocean (phytoplankton) currently do about as much photosynthesis each year as all the plants on land. Some of these phytoplankton end up sinking to the bottom of the ocean, taking carbon with them. So without algae, the carbon dioxide concentration in the atmosphere would be even higher than it already is.

Many algae are involved in symbiotic relationships with other organisms. For example, corals and sea anemones involve symbiosis between Cnidarian animals and single-celled dinoflagellate algae. Coral bleaching represents the loss of the algae and their pigments! Another example would be lichens, which are symbioses between fungi and algae.

Besides oil, algae produce a wide variety of important bioproducts including vitamins, nutraceuticals, pigments, and food additives such as carrageenans.

Q: What is the amount of electricity needed to produce the algae diesel (i.e. ratio energy in/out)? Thanks! Cassi G, Anaheim, California

Niyogi: This is an important question to ask for any type of alternative energy. Inevitably, there are going to be energy inputs that are necessary to produce a fuel from algae, just as there are for other biofuels, such as corn ethanol.

For algae, energy will be needed to build the ponds or photobioreactors, to mix the water and provide carbon dioxide and other nutrients, to harvest and concentrate the algal cells from large volumes of water, and to make and transport the biodiesel product. Because many of these technologies are still at a relatively early stage of development, I don't think there is a clear answer yet for algae. A lot of engineers are hard at work trying to minimize the energy inputs and maximize the net energy output.

Q: What are the possible negative effects on the economy and environment that might arise from switching to the production and use of algae fuels? Anonymous

Q: How sustainable are algae-produced biofuels? (What is their long-term maintenance and environmental impact?) Rebekah D, Monroe, Georgia

Niyogi: Although algae appear to have a lot of advantages in terms of land and water use, it is essential to analyze the sustainability, environmental impacts, and possible unintended consequences of large-scale algal biofuel production. Algae potentially could be grown in ponds on marginal land with saltwater, but there will still be a need for some freshwater (for example, to replace water lost to evaporation). How will this impact other demands for freshwater in marginal environments?

In terms of the long-term stability of algal cultures, it is likely that pests, pathogens, and "weeds" could be problems, as they are for agricultural plants. There is still a lot to learn about the basic biology of algae. So at this point I don't think anyone really knows the answer to this question. However, it is clear that it needs to be addressed alongside the development of the algal biofuel industry, similar to the situation for other biofuels.

Q: What is different from algae and corn in creating gas? Chris

Q: Your wonderful slide show compared the yields from algae to soybeans. How does algae compare with corn? Jackson Coleman, Wichita, Kansas

Niyogi: Corn is not considered to be a major oil crop—it produces around 18 gallons of oil per acre per year, which is less than half as much as soybeans. The yield of oil from algae still needs to be demonstrated on a large scale, but assuming an optimistic but not unrealistic annual yield of 4,000 gallons of oil per acre, it is clear that algae could be a couple hundred times more productive than corn.

Comparing algal oil to corn ethanol, algae would be around ten times more productive in terms of fuel energy.

As mentioned in the NOVA segment, it's also important to note that the use of corn for energy competes with its use as a food crop, whereas this is not an issue for algae.

Q: How does algae fuel compare to other renewable energy sources, such as solar or wind energy, in terms of land usage and efficiency? Manojit Nandi, Texas

Niyogi: Algal photosynthesis is essentially a type of solar energy, because the cells are converting the energy of sunlight and carbon dioxide into stored energy in the form of oil. Assuming 4,000 gallons of algal oil per acre per year, the overall efficiency of algal oil production (energy in the oil divided by the total energy in the incident sunlight) would be around two percent on a full solar spectrum basis. This is lower than the efficiency of electricity production by typical photovoltaic solar cells, so photovoltaics would generate more energy per land area. However, algae are producing a liquid fuel, whereas photovoltaics (or wind turbines) are producing electricity.

I think that we will continue to need both types of energy in the future. Even if all cars ran on electricity, we would still need an energy-dense liquid transportation fuel for trucks, trains, and airplanes.

Q: In the show segment, I believe the algae "factory" promoter said that UV from sunlight is deleterious to algae? Isn't that part of their natural process? Jackson Coleman, Wichita, Kansas

Niyogi: UV light can be harmful to algae, but they have evolved mechanisms to protect themselves and to repair any damage that occurs. For example, many algae produce screening pigments that absorb UV light.

Q: Without a doubt algae has rapid growth and very decent lipid production (compared to terrestrial plants), but isn't the big problem how to cost effectively separate the lipids, plant material (cell walls) and the growth medium (nutrient water)? Are solutions on the horizon? Seth Mulligan, New York

Niyogi: Yes, this is one of the major challenges that needs to be overcome in order to make algal biofuels commercially viable. Harvesting algae from huge volumes of water is very different from harvesting a land-based crop plant, but there are a number of possible solutions to the problem that are being investigated. Some of the proven approaches include filtration, flocculation, and flotation, depending on the specific species of algae being grown. Minimizing the cost and energy input is a critical factor.

Other possibilities in relatively early stages of research include "milking" the oil from algae by extraction methods that don't kill the cells, engineering algae to secrete the oil directly into the culture, or somehow getting the cells to break open and release the oil on demand.

Q: If algae is easy to farm and doesn't compete with food crops like corn-based ethanol does, what's stopping it from playing a larger role in the biofuels market today? Jeanette

Niyogi: Algae-based biofuels are considered to be second-generation (or "next-generation") biofuels, compared to corn ethanol and plant-based biodiesel. The technology for large-scale production of algae is still at a relatively early stage of development, so more work and scale-up is needed to demonstrate that a biofuel can be produced economically and in large amounts from algae. This might happen in the next couple years, at which point I think there will be a lot more interest and funding available to help push algal biofuels to market.

Q: Hi Dr. Niyogi:
Are algae good for other things (food, cosmetics, plastics)? If we harness algae could we potentially then have a fuel source where the byproduct is used in other ways? Mary

Niyogi: Scientists are investigating all sorts of potential "co-products" from algae. For a company, having a valuable co-product with a big market could help make algal biofuels more economically viable. After extracting the oil from algae, around half of the biomass will be leftover.

Several high-value products are already made from algae, such as vitamins (which are used in nutraceuticals), long-chain polyunsaturated fatty acids (which are added to infant formula), and pigments (which are used in cosmetics or fed to farmed salmon). But the markets for these products are relatively small compared to the energy market. Algal biomass can be high in protein, so it could be used as animal feed. Alternatively, the leftover biomass could be subjected to a process called anaerobic digestion to produce methane ("biogas") as an additional form of energy.

Q: It is frustrating that a fuel source that seems much more 'green' (no pun intended) than other biofuels is taking so long to catch on. Why is progress so slow? Is there a way to make it faster? I would like to start filling my gas tank with algae fuel asap! Naomi, Portland, Maine

Niyogi: I share your frustration! Part of the problem has been a historical lack of funding for research on algae. Besides a relatively low level of research funding for individual university labs over the years, there was a reasonably big effort called the Aquatic Species Program at the Department of Energy's National Renewable Energy Lab in the 1980's and early 1990's. Unfortunately, this project was discontinued in 1996, but you can read about their results in their close-out report (

The good news is that algae are starting to get a lot more attention these days, even from big oil companies that are now putting tens and even hundreds of millions of dollars into algal biofuel research. The Department of Energy sponsored an Algal Biofuels Technology Roadmap workshop last year to discuss the basic research that is needed to demonstrate whether or not algal biofuels can be commercially viable. The official report from the workshop will be out soon, and new research funding will hopefully will lead to faster progress.

Q: Hi Mr. Niyogi:

I was wondering—since we genetically modify our food so much, is there any potential in genetically modifying algae or other non-food plants so that they produce more oil, or are easier to extract the oil from? Is that anything that scientists have considered? Karl Banks, Atlanta, Georgia

Niyogi: Yes, this is definitely possible. Improvements in the productivity of biomass and oil from algae will almost certainly be necessary to minimize land use and make algal biofuels commercially viable. A lot of scientists are working on modifying algae using traditional plant breeding methods as well as the latest molecular biology techniques such as synthetic biology. Some of the biological factors that could be improved include the efficiency of photosynthesis, temperature tolerance, cell wall composition, and oil biosynthesis pathways.

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