All of these use cases will have varying levels of carbon capture, and of course how the algae is grown will also impact the total level of carbon capture (energy source, equipment used, etc). Take a look at some of the use cases which have the longest duration of carbon capture when it comes to algae.
Carbon Storage Methods with Algae
BioChar is essentially charcoal produced from plant matter. Algae can be turned into biochar by slowly heating the harvested mass for extended periods of time in a low oxygen environment. Moisture and other compounds are released from the algal biomass and carbon dioxide is left behind. BioChar can last for decades (up to 10,000 years in soil), but is very energy or material intensive to make. Of course, the emissions from the production process can be offset if using solar, wind, hydro, or nuclear energy to produce it. Biochar can be stored in soil or abandoned caves to create high permanence for carbon credits.
BioFuels are high energy liquids developed from plants and biomass. A relatively common biofuel is ethanol, which is typically blended with unleaded gasoline and used in vehicles. Since algae has a high level of carbohydrates and fats, biofuels such as ethanol and butanol can be produced through fermentation or chemical synthesizing. Biofuels can be stored in tanks, reservoirs, and used in vehicles to create a carbon neutral fuel (grow algae to capture carbon, use it in vehicles). It is much more economically viable to use any algal biofuel for power than to store it as a carbon credit, so while it could have high permanence, it wouldn’t be the most optimal choice for storage.
According to a study from Princeton University, concrete production amounts to 8% of total global carbon dioxide emissions. According to another study published in Nature, concrete production uses a total of 9% of the world’s total water supply - most of which is potable freshwater. Concrete, if installed properly, can last between 20-50 years and if algae water is used to produce that concrete it could serve as a great source of carbon storage. Recycled concrete can be used to create aggregates or fresh concrete, so even older material can still maintain some level of carbon capture.
Reservoirs are another simple way of storing carbon capture with algae. A reservoir is anything capable of holding large amounts of liquid (preferably water). There are reservoirs everywhere. Wastewater treatment facilities, retention ponds, septic tanks, sewage lines, old oil wells, emptied aquifers, and hazardous underground caverns. Since the algal cells are trapped underground they cannot release carbon dioxide and it leads to a relatively high level of carbon storage.
Fertilizer and Soil Storage
Soil carbon storage has acquired huge interest in recent years for carbon credits. By utilizing regenerative farming techniques, farmers can ensure that carbon dioxide captured by plants and the soil itself remains there. Off gassing, the process of carbon dioxide leaking out from the soil, is low risk if the soil is not tilled seasonally. Estimates for total CO2 emissions by agricultural activities range from 9% to 35%. By improving agricultural practices through the use of natural algae fertilizers and regenerative farming techniques, it’s possible to lower those emissions while making farms carbon sinks over the long term. The permanence of soil based carbon credits are between 10-100 years.
Conclusion & Summary
Algae are multi-use aquatic plants that are excellent at capturing and storing carbon. Their fast growth, limited needs, and extensive range in growth environments make them an excellent contender for a powerful method of carbon capture. While many industries have not yet begun interfacing with algae for their development purposes, Algaeo believes interest will only grow over the next few years. Estimates for carbon credit pricing show that higher demand growth within the next decade will spur more interest in alternative carbon credit sources outside of agroforestry. Algae can very easily supplement several industries while providing them carbon removal benefits.