By Kevin Stam

*Photo: Chokniti Khongchum/Shutterstock.com*

I. What is Algae?

Algae is a living organism found in our oceans wherever sunlight is available.

There are about 65,000 known species of algae on earth, and most have photosynthetic functions similar to plants: they absorb CO2 from their surroundings and release oxygen into the atmosphere. Photosynthesis from algae, also known as phytoplankton and seaweed, is responsible for 50% of all carbon dioxide absorption in the atmosphere. In fact, it’s been estimated that 30-50 billion tons of CO2 are absorbed by algae each year!

Astoundingly, algae have been a part of marine ecosystems for billions of years. However, in just a short period of time, humans have made use of algae in some of the most remarkable and innovative ways, including the development of nutrients, cosmetics, and industrial chemicals.

But what if algae could be used to fuel our cars, buses, trains, or even airplanes?

Not only are algae readily available, but some species of microalgae (microscopic algae) are rich in oils! In a world where human-grown algae could be used to harness biofuels at a commercial scale, humanity might be one step closer to reducing the effects of climate change on our future generations...

II. History of Algae Biofuel Research

The possibility of deriving oil and other lipids from algae was first documented before World War II by two European scientists Harder and Witsch (Figure 1). In fact, the topic itself only received heightened interest during the early 70s.

The Energy Crisis in 1973 prompted $25 Million research over 25 years to explore alternative sources of fuel, including algae-derived biofuels. During the Energy Crisis, the American oil supply was threatened by an embargo from OAPEC (The Organization of Arab Petroleum Exporting Countries) due to the US and other Western countries’ support of Israel. Following the embargo, the American government feared for its nation's own supply of petroleum, which led to a push for American energy independence and alternative fuel sources. So, in 1978, US President Jimmy Carter passed the Aquatic Species Program with the Department of Energy in response to the Energy Crisis. Research into the topic of biofuels derived from algae officially took off.

*First documented research into algae-research and oil extraction (Harder and Witsch) Photo: Wiley Online Library*

III. Some benefits in using algae for biofuels

Harnessing bio-energy from the oils found naturally in algae procures many benefits:

First off, algae are unlike its current plant-based alternatives for biofuels. Microalgae contain much higher oil content than conventional biofuel sources, including soybeans, palm oil, or corn. The oil content of microalgae is usually between 20 percent and 50 percent of its dry weight, while some strains can reach as high as 80 percent.

Secondly, algae produce biomass very rapidly, with some species doubling every 6-hours. In addition, microalgae grown for biofuels could occupy their own plot of land without interfering with current farming areas. Due to the high oil content in microalgae, growing these organisms would take up less surface area than traditional biofuel sources such as palm oil. These reasons explain why current genomic testing is critical in selecting the most oil-rich species to grow rapidly and efficiently.

Finally, algae are known to uptake nutrients efficiently. Its end product, algal biodiesel, is both biodegradable and non-toxic. Growing algae at a commercial scale could introduce major advantages for wastewater treatment, as algae are also known to absorb molecules such as nitrates, phosphates, sulfates, and carbon dioxide. This makes algae highly interesting in bioremediation for rivers, streams, and other municipal water bodies alongside energy production.

IV. The Open and Closed System: Algal harvesting

In reality, however, humans have a long way before producing algae-based biofuels at a commercial level. Testing today shows there many challenges lie ahead.

Regarding the harvesting of algae for biofuels, there are two major types of systems used: open systems and closed systems.

Open systems are large, often taking up the area of several football fields. They are shaped like a raceway track and are mixed along the track to keep the algae from settling at the bottom. On the other hand, closed systems, are much smaller and include glass chambers or vessels which are far more controlled in terms of light exposure. The closed system acts as a barrier to foreign contaminants.

Much research into scaling algae production has examined open systems due to their reduced reliance on human intervention, although it has been found that closed systems are more favorable for production (that is, more algae are produced).

An Open System (Raceway and paddle), photo: https://farm-energy.extension.org/ — An Open System (Raceway and paddle), *photo: https://farm-energy.extension.org/*

A closed-system (photobioreactor), photo: https://farm-energy.extension.org/ — A closed-system (photobioreactor), *photo: https://farm-energy.extension.org/*

IV. In Algal biofuel production, current processes are complex and costly

A quick look at the steps involved in biofuel production from algae makes a good case as to why today’s processes are too complex and too costly. As the diagram below illustrates, a great deal of electricity and water are necessary for biodiesel (biofuel) production. Put simply, today, there are no harmonized processes as to the ideal type of system or oil-extraction method. This is best reflected in the cost/liter of algae biodiesel, which ranges from $0.43 to $24.60. The range of these prices indicate that algae biodiesel is still far off from competing with traditional petroleum.

*Photo: Adapted from Clarens et al., 2011*

Researchers typically assess the efficiency of energy production in these systems with the EER or Energy Efficiency Ratio, the amount of energy produced from the system, and energy intake. A ratio much greater than one indicates a highly productive system, while less than one indicates a counter-productive system. The table below shows that, unfortunately, algae still ranks almost 1/4th as energy-efficient as palm-oil.

*Photo: https://www.mdpi.com/2076-3417/10/22/8181*

IV. Future directions for algal biofuels

Despite these challenges, researchers have not discarded biofuel production from algae as a viable option for our energy-sustainable future.

Many global research teams are still assessing how to bring costs down, either through process improvements or pairing innovations with biofuel production. As mentioned, one opportunity lies in pairing algal biofuel production with wastewater treatment around cities. By injecting wastewater into open algae systems, algal bioremediation could help municipalities reduce the expenses associated with traditional wastewater treatment. These expenses may include the cost of the chemicals used in the treatment process or the maintenance and operation costs needed to sustain wastewater plants themselves. Partnerships between bioenergy companies and wastewater treatment facilities could go a long way to make algae biofuels a more cost-effective option for end consumers in the future.

Another promising direction involves reusing and valorizing byproducts which are generated in the process of biofuel creation or as independently from algae. For example, a steady market for: household items, cosmetics, or even livestock feed derived from algae could offset the expenses involved in producing algae-based biofuels. This would likely lead to lowered costs for end consumers.

In conclusion, incorporating more sustainable fuel sources such as algae-based biofuels will likely evolve as a series of adjustments before becoming a widescale, popular option.

References

“Biofuels: The Promise of Algae.” BIO, Biotechnology Innovation Organization, archive.bio.org/articles/biofuels-promise-algae.

Bošnjaković, Mladen, and Nazaruddin Sinaga. “The Perspective of Large-Scale Production of Algae Biodiesel.” MDPI, Multidisciplinary Digital Publishing Institute, 18 Nov. 2020, www.mdpi.com/2076-3417/10/22/8181.

Farm-Energy. “Algae for Biofuel Production.” Farm Energy, 12 Apr. 2019, farm-energy.extension.org/algae-for-biofuel-production/.

Leaf, Arctic. “Von Witsch Archives.” Fuel Freedom Foundation, 21 May 2014, www.fuelfreedom.org/tag/von-witsch/.

Metting, F.B. 1996. Biodiversity and application of microalgae. Journal of Industrial Microbiology 17:477-489

Could Algae be the next Gasoline?