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The Use of Algae to Reduce CO2 Emissions

In the urgent quest to combat climate change and reduce greenhouse gas emissions, scientists and researchers are turning to nature for solutions. One of the most promising answers lies within the world of algae. Often overlooked, these simple aquatic organisms possess remarkable capabilities to sequester carbon dioxide and play a crucial role in the fight against global warming.

In this article, I will explore how algae can be harnessed as a powerful tool to capture carbon and address the climate crisis.


Algae Biofuels: A Carbon-Neutral Alternative

One of the most significant applications of algae in reducing CO2 emissions lies in the production of biofuels. Algae-based biofuels, also known as “green crude,” have gained traction as a potential carbon-neutral alternative to fossil fuels. When algae are cultivated for biofuel production, they absorb carbon dioxide from the atmosphere during photosynthesis, converting it into organic matter. This process sequesters CO2, effectively reducing its presence in the atmosphere.

Photosynthesis is considered one of the most sustainable strategies for capturing and storing CO2 from the atmosphere, with several studies indicating that microalgae have exhibited maximum carbon-fixing capabilities, being able to capture around 100 Gt of CO2 into biomass annually.

Furthermore, when algae-based biofuels are combusted, the carbon dioxide released is equivalent to the amount that was previously sequestered during their growth. As a result, algae biofuels have the potential to be carbon-neutral, offering a sustainable and eco-friendly energy source that does not contribute to the net increase of greenhouse gases in the atmosphere.

Algae’s carbon capture capabilities extend beyond natural ecosystems. Various industries, such as wastewater treatment plants and biogas facilities, can benefit from utilising algae to capture carbon dioxide from their processes. Algae provide an eco-friendly and cost-effective solution for recycling CO2 emissions, as they require minimal resources and produce valuable biomass, which can find application in various sectors.

While the process itself still burns carbon in transporting and using the fuel produced, the algae oil production process is considered much more energy-efficient than traditional oil production. The ability to sustain growth while increasing oil content is an important advance. Algae has other advantages over traditional biofuels because it can be cultivated and rapidly grow in salt water, wastewater or wasteland and thrive in harsh environmental conditions, therefore limiting stress on food and fresh water supplies.


Carbon Capture with Algae Bioreactors

Algae bioreactors present another innovative approach to reducing CO2 emissions. These systems use algae to capture and convert carbon dioxide from industrial processes, power plants, or other emission sources. The bioreactors provide a controlled environment for algae growth, ensuring optimal conditions for photosynthesis and CO2 sequestration. New technologies aim to capture emissions from power plants and pipe them into algae ponds, in a twist on carbon sequestration.

Algae bioreactors can be placed near CO2-emitting facilities, allowing direct capture of the greenhouse gas before it enters the atmosphere. By combining these bioreactors with industry, we can reduce carbon emissions and make useful biomass or biofuels.

What is more, when used in bioreactors, algae are 400 times more efficient than a tree at removing CO2 from the atmosphere. In addition, algae can consume more carbon dioxide than trees because they can cover more surface area and grow faster while producing more biomass in a limited space.


Algae Carbon Sequestration in Aquatic Environments

Algae play a crucial role in the carbon sequestration process within aquatic environments such as oceans, lakes, and wetlands. Marine algae, also known as phytoplankton, perform photosynthesis and absorb significant amounts of CO2 from the surface waters. When these phytoplankton die or are consumed by other organisms, some of the carbon they contain sinks to the ocean floor, becoming sequestered in marine sediments for long periods.

Southern Cross University PhD candidate Mona Andskog and researchers at the Max Planck Institute for Marine Microbiology in Germany found that fucoidan, a compound in algal mucus, is particularly responsible for this carbon removal. Using the results from this study, brown algae, often called seaweed could be sequestering 550 million tons of carbon dioxide removed from the air every year into algal mucus. This equates to almost the amount of Germany’s entire annual greenhouse gas emissions – and more than Australia’s annual greenhouse gas emissions.


Algae, Hydrogen and Biohydrogen

Besides being easy to grow and handle, algae also produce another fuel: hydrogen. Algae can be unicellular or as large as a tree, like the giant sea kelp and they are typically photosynthetic, meaning they need carbon dioxide and sunlight to grow. Like most plants, many algae produce oxygen during the daylight and at night they consume oxygen, but usually much less than was produced during the daylight. Single-cell organisms need haemoglobin to survive in an oxygen-free environment. When green algae run out of air or “can’t breathe,” they get rid of excess energy through the production of hydrogen. 

Algae produce hydrogen under certain conditions. In 2000 it was discovered that if C. reinhardtii algae are deprived of sulfur they will switch from the production of oxygen, as in normal photosynthesis, to the production of hydrogen. The biological hydrogen production with algae is a method of photobiological water splitting that is done in a closed photobioreactor based on the production of hydrogen as a solar fuel by algae. Microalgae like cyanobacteria and green algae can produce biohydrogen after the derivation of their photosynthetic metabolism. Besides, microalgae can also be used as feedstock for biohydrogen production by microbial dark fermentation. Biohydrogen from microalgae is renewable.

Algae make a small amount of hydrogen naturally during photosynthesis, but Anastasios Melis, a plant- and microbial biology professor at the University of California, Berkeley, believes that genetically engineered versions of the tiny green organisms have a good shot at being a viable source for hydrogen. But mercantile production of microalgae biofuels considering bio-hydrogen is still not practicable because of low biomass concentration and costly down streaming processes. The process is still at least five years from being used for hydrogen generation.

Researchers will first have to increase the algae’s capacity to produce hydrogen. During normal photosynthesis, algae focus on using the sun’s energy to convert carbon dioxide and water into glucose, releasing oxygen in the process. Only about 3 to 5 percent of photosynthesis leads to hydrogen. Melis estimates that, if the entire capacity of the photosynthesis of the algae could be directed toward hydrogen production, 80 kilograms of hydrogen could be produced commercially per acre per day.


Advantages and Drawbacks of Using Algae as a Biofuel

As with all positives and because nothing is perfect, algae as a biofuel also presents several challenges that need to be taken into account and make wise decisions to ensure we have a positive impact on the environment and our planet before implementing these new fuel alternatives, such as:

  • Requires large amounts of space and water to be productive.
  • Algal biofuel production takes a long time to create biofuels we can use.
  • Has high production costs using current technologies.
  • It has regional suitability issues.Algae biofuels have a shorter life than conventional fuels.
  • Requires significant fertiliser use.
  • It can deplete non-renewable resources, such as phosphorus.
  • Algae fuels may not be suitable for all transportation needs.
  • It may create variations in the quality of the biofuels reaching the market.
  • It would have the same issues we see in monoculture (risk of pests, impact on quality, limiting diversity).


While these are considerable challenges, there are also many positive highlights for the use of algae as biofuel, including:

  • It is abundantly available even without commercial processing.
  • Uses large volumes of carbon dioxide.
  • Has the potential to produce high energy content.
  • Would work with our current system of fuels.
  • Can produce numerous byproducts, just like petroleum hydrocarbons.
  • It is a renewable resource.
  • Bio-based fuel offers carbon-neutral combustion.
  • It is extremely productive when considering the overall supply chain process.
  • Many algal species are bio-fixers for the reduction of greenhouse gas emissions.
  • It is a crop that we can grow fast and with high levels of efficiency.


In the pursuit of a sustainable future, algae emerge as a powerful ally in the battle to reduce CO2 emissions. Their versatility, efficiency, and ability to sequester carbon dioxide through various mechanisms make them a crucial component of global efforts to combat climate change.

As we face the escalating challenges of climate change and greenhouse gas emissions, unlocking the full potential of algae could prove vital in our efforts to preserve the planet for future generations. By continuing to research, innovate, and implement sustainable practices, we can harness the power of these humble organisms and create a brighter, more sustainable future for all.


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About the Author:

Andreea has been recruiting permanent and contract opportunities Australia-wide for the past 3 years, covering the full life cycle of projects in Solar, Wind, and occasionally BESS.
Read more about Andreea Olariu.

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