Algae Biofuel: Can Pond Scum Power the Planet?

Algae could be a lean, mean biodiesel machine. Or maybe not so lean. Algae’s oil is what makes it a great potential feedstock for biofuel. Feedstock is a material used to make biofuel. Biodiesel is an important type of biofuel. 

Biodiesel can be used instead of petroleum-based diesel fuel. It can also be blended with it. Biodiesel made from algae oil is called a Third Generation biofuel. For now, only a few refineries are making it. But it could become a major source of biofuel one day. 

Algae 101

Algae belong to a group of non-plant photosynthetic organisms. They make sugar and oxygen using water, carbon dioxide (CO₂) and energy from the Sun. Some algae, like seaweed, are large and multicellular. But many are microscopic and single-celled, like the green microalgae used for biodiesel production. The cells in green algae metabolize the sugar they produce into oil. This is a way to store energy. 

Did you know? 

Green algae can grow very quickly. Some species accumulate oil until the oil is more than half their mass! 

How biodiesel is made from algae

Plant and animal fats, including the oil in algae, have long organic molecules called triglycerides. 

The first step in making biodiesel is to extract the oil containing the triglycerides from the algae. There are two ways to do this. One is by mechanically pressing the algae, like you would press olives to make olive oil. The other way is by combining the algae with an organic solvent. 

Then, the triglycerides are converted into fatty acid methyl esters (FAMEs). This happens through a transesterification reaction. This same process can be used to derive FAMEs from canola oil or waste cooking grease. 

Energy 101|Algae-to-Fuels, U.S. Department of Energy (2:33 min)

Like biodiesel feedstock crops like canola, algae can be farmed. Farmed algae have the same requirements as the green algae that grow in ponds, swimming pools, and aquariums. They need water, sunlight, CO₂ and nutrients like nitrogen and phosphorus to grow. 

There are two main ways to farm algae:

• in outdoor ponds 
• in closed bioreactors

Outdoor open ponds look like big pools. They have moving water which circulates the algae. This way, all the algae get the same amount of exposure to sunlight. 

There are some disadvantages to using open pools. The water can evaporate quickly because they have large surface areas. They’re also at risk of getting contaminated by other algal species.

Closed bioreactors are closed, indoor environments where algae can grow. They come in a variety of shapes and styles. The advantage of these is that humans can carefully control the growing conditions. But they are much more expensive to build and maintain than open ponds.

What are some benefits of using algae to produce biodiesel?

There are a few benefits to using algae feedstock for biodiesel production, instead of crop feedstock like canola. They are:

1. Algae contain more oil in a smaller area than some other crops. Scientists aren’t sure how much more oil. But it could be two to ten times more.
2. Algae do not need farmland. This means that they do not compete with crops for high-quality agricultural land.
3. Algae could help improve air pollution. Algae need large amounts of CO₂ to support photosynthesis. Some of this CO₂ could come from things like industrial emissions. 
4. Algae need water, but it doesn’t have to be clean water. A research project run by NASA has shown that algae can grow in municipal wastewater in floating plastic bioreactor tubes. As the algae grows, it cleans the wastewater by extracting nutrients. The algae can then be used for biofuel production. 

Did you know? 

The Canadian Research Council has partnered with two companies, Pond Tech and St. Mary’s Cement, to build an algal biorefinery. The goal is for Pond Tech to use the waste products from St. Mary’s Cement to grow algae. In turn, that algae can produce biofuels!

What are some downsides of using algae to produce biodiesel?

There have also been concerns about the sustainability of algae biofuels. The main concerns are:

1. Growing algae in ponds takes a lot of water. Water evaporates from the pond surface. That means that more water needs to be added all the time. This is less of an issue in biorefineries because they are closed systems.
2. Bioreactors need a lot of energy to grow algae. The energy is used to circulate water, provide light and maintain the best temperature. This is less of an issue in outdoor ponds because light and thermal energy comes from the Sun. But energy is still needed in outdoor ponds to circulate water.
3. Biorefining is a slow process. Algae grow fast, but extracting and refining the oil they produce is slow. It is slower than other methods of producing biofuels. 
4. Algal biofuels may have a negative energy balance. In other words, algal biofuels may take more energy to produce than they provide!
5. Algal biofuel facilities are very expensive to build and operate. This means that algal biofuels may end up costing more than most people or businesses are willing to pay.

But some of the benefits of algal biofuel could help with these drawbacks. Things like capturing CO₂ from industrial waste and using nutrient-rich wastewater may help unlock algae’s full biofuel potential. 

Algae Biofuels beyond Biodiesel

There are other ways to harness energy from algae. For example, algae can be dried into ‘algae coal’ and burned with fossil coal in power plants. Algae can also be used to generate biogas. This technology uses bacteria to break down organic material like algae in anaerobic (no-oxygen) conditions. The bacteria produce methane biogas, which can be burned to generate electricity. 

Algae biofuels are not common yet. But if scientists can find a way to unlock their energy at a lower cost, the future looks green. And maybe a little slimy!