What Is the Carbon Footprint of Algae Fuel? A Life-Cycle Assessment 

What Is the Carbon Footprint of Algae Fuel? A Life-Cycle Assessment 

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Grace Smoot

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You probably know that trees are important in the fight against climate change. But did you know that algae are also important, and on a much larger scale? Algae can even be used to produce sustainable transportation fuels that emit less greenhouse gas emissions upon combustion. So, we had to ask: What is the carbon footprint of algae fuel?

On a life-cycle basis, algae fuel has a low carbon footprint. It’s CO2 emissions are comparable to biodiesel, which emits 5.87 pounds (2,661 grams) of CO2 upon combustion and 404 grams of CO2 when driving one mile. Algae fuel has various environmental benefits and combats climate change. 

Keep reading to learn about the overall carbon footprint of algae fuel, its carbon footprint throughout its life-cycle, and how environmentally friendly it is.

Here’s What the Carbon Footprint of Algae Fuel Is

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the GHG emissions associated with consumption, but also includes other emissions such as methane (CH4), nitrous oxide, and chlorofluorocarbons.

Carbon footprint: the amount of greenhouse gases and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home, driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills).

Algae fuel, also known as algal biofuel, is a type of biofuel that is produced from algae.

Algae fuel, algal biofuel, or algal oil: an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils”

Wikipedia

Algae are organisms capable of existing in both marine (saltwater) and freshwater environments. They are the food base for almost all aquatic life and are sources of food, crude oil, and pharmaceutical/industrial products for humans. 

They are typically photosynthetic, meaning they use the sun’s energy, water (H2O), and carbon dioxide (CO2) to create energy and biomass. They also release massive amounts of oxygen (O2) into the atmosphere during this process. The two classifications of algae are macroalgae (multicellular) and microalgae (unicellular). Common varieties of algae include green, red, brown, and blue-green (cyanobacteria). 

Algae can be used to produce biofuel, which is any liquid fuel derived from biomass. The two most common biofuels used for transportation are ethanol and biodiesel, which are commonly blended with petroleum fuels (gasoline and diesel fuel). Microalgae and cyanobacteria can be used to make biofuels, specifically biodiesel. 

Biofuel: a fuel (such as wood or ethanol) composed of or produced from biological raw materials”

Merriam-Webster Dictionary

Biomass is renewable organic material from plants and animals that can be used to produce a wide range of products including energy, everyday products that contain plastics, and fuel. This is what the algae create during the photosynthetic process.

Biomass: natural materials from living or recently dead plants, trees and animals, used as fuel and in industrial production, especially in the generation of electricity”

Oxford Dictionary

Algae fuel is considered third-generation biofuel, with sugar cane and corn being the first and vegetable and animal waste streams being the second-generations. Through photosynthesis, algae produce biomass that contains carbohydrates, proteins, and lipids. 

The three main pathways to produce biofuels from algae are:

  1. Vegetable oil: These oils can either be esterized to produce biodiesel or are further refined into various biofuels including renewable diesel and jet fuel.
  1. Carbohydrates: These sugars can be fermented to make ethanol and butanol
  1. Biomass: Cellulosic material can be used for pyrolysis oil or combined heat and power generation.

Producing biodiesel from algae is the most common pathway because algae produce triglycerol during photosynthesis, which is the right kind of oil required to make biodiesel. Although the CO2 emission values for algae fuel are not well known, the numbers for biodiesel – which is largely produced with algaes biomass – have been established. And we can use these numbers to get an emissions approximation for algae fuel.

Burning of algae fuel  Carbon footprint
Burning one gallon 2,661 grams of CO2 emitted
Driving one mile (on average) 404 grams of CO2 emitted
Per million British thermal units (Btu) 162.8 pounds of CO2 emitted

Global biofuel production in 2019 was 156 billion liters (bl), and this number is expected to increase to 165 bl in 2025. 

Illustration of lobal biofuel production in 2019 and forecast to 2025
International Energy Agency: Global biofuel production in 2019 and forecast to 2025

Oil (including gasoline and diesel fuel) is the world’s primary fuel source for transportation. But since the turn of the century, there has been a push towards cleaner-burning transportation fuels with fewer negative effects on the environment. Although algae fuel does not currently occupy a large space in the fuel market, the market for algae fuel is expected to increase from $6.8 billion (b) to $11.4 b by the year 2027.

To understand the total carbon footprint of algae fuel, we must assess its life-cycle and each stage’s carbon footprint. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials. Over the years, companies have strategically used LCA to research and create more sustainable products. So, let’s have a look at the LCA of algae fuel!

The life-cycle stages of algae fuel  Each stage’s carbon footprint
Building of algae fuel farm CO2 emissions from building the components of the algal farm
Extracting of algae fuel  CO2 emissions from either the transesterification or fermentation process
Transportation of algae fuel  CO2 emissions from transporting algae fuel by barges, tankers, pipelines, trucks, and railroads across distances
Building back of algae fuel farm CO2 emissions from utilizing construction equipment to demolish the algal farm systems and construct new infrastructure in the old system’s place

The total carbon footprint of algae fuel would equal the carbon footprint from building + the carbon footprint from extracting + the carbon footprint from transportation + the carbon footprint from building back.

What Is the Carbon Footprint of Building an Algae Fuel Farm

Algal fuel farms typically use one of two design models:

  1. Open pond: Designed in a raceway configuration, these ponds are approximately 1 foot deep and have a paddlewheel that paddlewheel, and the resulting algal broth is harvested behind the paddle wheel.
  1. Photobioreactor: These systems consist of 10-centimeter diameter, transparent tubes. The algal broth is circulated through a pump to the tubes where it is exposed to light for photosynthesis before it is returned to a reservoir. Algae harvest occurs after the solar collection tubes. 

Open ponds cost less to build and operate compared to photobioreactors, but they also have high levels of evaporation due to them being open-air, and they face problems concerning contamination with other algal species. 

Photobioreactors do not face evaporation or contamination issues and can produce higher biomass concentrations, but they are also more expensive to build/operate and require close monitoring of CO2 and O2. Photosynthesis produces O2, and O2 is toxic to algae at high levels. Degassing zones, areas where the algal broth is bubbled with air to remove excess O2, are necessary in this case. Photosynthesis also requires CO2, so this must be fed into the system to support optimal algae growth. 

Depending on which system is used, algae fuel farms may have many components, and constructing these components requires machinery that emits CO2. Paddlewheels, baffles, pumps, tubes, and degassing columns are all components with a carbon footprint. 

What Is the Carbon Footprint of Extracting Algae Fuel  

After it is grown in either an open pond or photobioreactor system, the algae is harvested from the algal broth via gravity settlement or centrifuge. The extraction process that follows is different depending on whether predominantly oil or carbohydrates are being used to produce biofuel. 

Vegetable oil from the algae is removed via solvent extraction and is converted to ethanol via biological conversion, specifically the process of fermentation. Fermentation converts sugars (glucose, fructose, sucrose) into ethanol and produces CO2 as a byproduct.

Carbohydrates from the algae are extracted and converted to biodiesel via chemical conversion, specifically the process of transesterification. In this process, vegetable oil, animal fat, and grease are converted into fatty acid methyl esters (FAME), producing biodiesel. 

What Is the Carbon Footprint of Transportation of Algae Fuel  

The global market for algae fuel is not well established because not many countries are currently producing it. But algae fuel is a type of biofuel – and the biofuel market is well established. So let’s have a look at this one to get approximate numbers for the algae fuel market.

The six largest biofuel-producing countries (amount per year) in the world are: 

  1. United States – 374 billion kilowatt-hours (bKWh)
  2. Brazil – 245 bKWh
  3. Indonesia – 78 bKWh
  4. Germany – 40 bKWh
  5. China – 39 bKWh
  6. Thailand – 27 bKWh

Calculating the carbon footprint of algae fuel transportation would involve knowing where the algae fuel is produced, where it is being consumed, and the distance between the two. Transporting biofuel  from the US to Brazil, for example, is an approximate 6,790 kilometer (km) (4,219 miles) transportation distance. Transporting biodiesel from the world’s largest biodiesel refinery, the Neste Singapore Refinery, to the US is a 15,299 kilometer (km) (9,500 miles) transportation distance. The carbon footprint of transportation for these circumstances would be high because it is a long distance that would require multiple modes of transportation. 

On the flip side, if algae fuel is produced in one country and is consumed in that same country, the transportation distance is much shorter and would require fewer modes of transportation, leading to a lower carbon footprint for this stage. 

What Is the Carbon Footprint of Building Back Algae Fuel  

Because algae fuel technology is relatively new and not currently operational on the commercial level, there is not much historical data on its life expectancy. CO2 emissions at this stage would occur when utilizing construction equipment to demolish the open pond/photobioreactor systems and constructing new buildings in the old algal farms’ place.

What Role Does Algae Fuel Play in Combating Climate Change

The transesterification of algae into algae fuel can potentially reduce GHG emissions by 60% when compared to petroleum diesel fuel. 

Climate Change: changes in the world’s weather, in particular the fact that it is believed to be getting warmer as a result of human activity increasing the level of carbon dioxide in the atmosphere”

Cambridge Dictionary

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 36 billion tons (bt) of CO2 are emitted from burning fossil fuels. The carbon found in fossil fuels reacts with oxygen in the air to produce CO2 which warms the earth by acting as a heating blanket.

Reduced CO2 emissions from algae fuel combat climate change in the following ways:

  • Melting of sea ice: Since 1979 arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 
  • Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.
  • Ocean acidification: The ocean absorbs 30% of the CO2 released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

Climate change results in global warming, when CO2 and other air pollutants absorb sunlight and solar radiation in the atmosphere, thereby trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). Between 1880-1980 the global temperature rose by 0.07C every 10 years. This rate has more than doubled since 1981, with a current global annual temperature rise of 0.18C, or 0.32F, for every 10 years. 

Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must limit global warming to 1.5C by 2040

The more we reduce CO2 emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

How Environmentally Friendly Is Algae Fuel  

Algal fuel comes with lower levels of GHG emissions compared to petroleum-based fuels. 

Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

Both the environmental benefits and drawbacks of algae fuel must be taken into consideration when discussing the issue of climate change.

What Are the Environmental Benefits of Algae Fuel  

There are many environmental benefits of algae fuel, including:

  1. Climate change mitigation: Because algae can grow faster and cover more surface area, it can be up to 400 times more efficient than trees at removing CO2 from the atmosphere when used in conjunction with bioreactors. 
  1. Air quality improvement: Algae fuel combustion does not produce sulfur oxides and produces less carbon monoxide than petroleum-based fuels. 
  1. Water conservation: Algae can be grown in both wastewater and saltwater, which reduces the demand and competition for limited freshwater supplies. 
  1. Carbon bsorption and ixation: Carbon released into the atmosphere when algae is combusted can be absorbed by the algae when it is growing. Algae comprise less than 2% of global carbon, yet they can absorb and fix up to 50% of atmospheric CO2, which equates to between 30 and 50 billion metric tons per year). They also produce 50% of global O2 through photosynthesis.
  1. Minimal land use impacts: A major drawback for land-based biofuel sources is the deforestation resulting from the large amount of land needed to grow and sustain the biomass material. Deforestation occurs at roughly 10 million hectares (~ 25 million acres) per year. Because algae can be grown using salt or brackish water instead of on land, it does not displace farmland needed to grow crops and does not cause deforestation. 
  1. High energy generation potential: Algae have the potential to generate a minimum of 30 times more energy when compared to the land-based crops currently used to produce biofuels. In one year, algae can produce as many as 5,000 biofuel gallons from a single acre.

What Are the Environmental Drawbacks of Algae Fuel 

One environmental drawback associated with algae fuel is electricity usage. Growing algae requires a large amount of energy to pump the water and stur the algal broth, and this energy is primarily generated from fossil fuels. Fossil fuel combustion releases toxic chemicals, heavy metals, CO2, and contributes directly to global warming. Also, algae need to be fertilized with nitrogen and phosphorus as they grow, the production and application of which generates emissions. 

What Are the Other Drawbacks of Algae Fuel 

The overall main challenge surrounding algae fuel is the economics. Crop protection, water and nutrient management, ecosystem design, light optimization, temperature management, and seasonal succession are all expensive components that come with maintaining an algae fuel farm. Because it is expensive to grow, harvest, collect, and transport algae, algae fuel has not yet gained significant traction in the commercial market. In order to make algae fuel more cost competitive with petroleum-based fuels, further research and development is necessary.

Final Thoughts

Because algae can grow quickly, absorb more CO2 than land-based biomass, and contribute to the avoidance of fossil-fuel combustion, it has promise as an alternative fuel to petroleum-based fuel. It has a low carbon footprint across its building, extraction, transportation, and building back stages. Besides combating climate change, it also improves air quality, conserves water, and has less of a negative effect on the environment than land-based biofuel sources.

Overall, algae fuel is a more sustainable alternative to petroleum based fuels, but it is not yet cost-competitive. More research and development is needed to make algae fuel a major player in the global biofuel market.

Stay impactful,

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Grace Smoot

Grace loves to research and write about all things related to climate action and sustainability. She holds a Bachelor’s of Science degree in Environmental Biology and works as an Environmental Survey Technician. Outside of work, she loves to work out, play soccer, and take her dog for long walks.

Did you know that the internet is a huge polluter of the environment? But fortunately not this site. This site is powered by renewable energy and all hosting-related CO2 emissions are offset by three times as many renewable energy certificates. Find out all about it here.

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