Beyond Trees: Using Blue-Green Algae for Natural Carbon Capture and Sequestration

Forestation is an important climate action strategy, but more sophisticated — and potentially more efficient — nature-based alternatives are emerging. One of them involves an environmental two-for-one: capturing carbon by preventing destructive blue-green algae blooms.

Cyanobacteria and algae blooms

Blue-green algae is the common name for cyanobacteria, a type of water-dwelling bacteria that has plant-like photosynthetic abilities.

An over-abundance or “bloom” of cyanobacteria can wreck ecosystems and harm other living things. “A combination of environmental factors such as the presence of nutrients, warm temperatures, and lots of light encourage the natural increase in the numbers of cyanobacteria,” according to the National Oceanic and Atmospheric Administration. In higher concentrations, the toxins produced by some cyanobacteria can damage the liver, nerves, and skin of humans and other creatures, including pets and livestock as well as wildlife.

The U.S. Environmental Protection Agency notes that warmer temperatures and other climate impacts affect the frequency and severity of algae blooms. Blue-green algae blooms in particular are a frequent occurrence in all 50 U.S. states and elsewhere in the world. They mainly occur on inland waters, but they can also happen in the open ocean. 

Putting “bad” algae to good use 

On the plus side, cyanobacteria are emerging as a clean technology jack-of-all-trades, partly because they are fast-growing, voracious consumers of carbon dioxide. Researchers have tweaked cyanobacteria to produce renewable hydrogen and other biofuels, for example.

Cyanobacteria are also attracting attention for their ability to convert airborne carbon to a solid substance. They have been linked to deposits of the mineral carbonate, a salt of carbonic acid. The “biomineralization” process carried out by cyanobacteria was formerly thought to occur as a result of outside factors. However, 2014 research concluded that some strains are capable of producing carbonate on their own.

In 2020, researchers at the University of Colorado in Boulder put the biomineralization concept to work. They demonstrated that, under the right growing conditions, certain types of cyanobacteria can produce calcium carbonate, which happens to be the main ingredient in cement. The research team tested their method on a growing medium of sand and gelatin. As the cyanobacteria produced calcium carbonate, they mineralized the gelatin and bound the sand into a bio-manufactured brick.

Algae remediation and carbon offsets

Regardless of the potential use cases for cyanobacteria-produced carbonate, algae blooms must be treated and prevented in order to protect aquatic habitats and human health.

BlueGreen Water Technologies is among those developing algaecides that specifically tackle cyanobacteria. Its patented, EPA-approved formula triggers a natural “suicide” response in cyanobacteria, clearing the way for beneficial algae and other aquatic species to take over.

The treatment effectively converts a body of water into a carbon sink, with the dead cyanobacteria locked into sediment for potentially millions of years, according to BlueGreen.

This carbon-sequestering feature could help offset the cost of remediating blue-green algae blooms, if stakeholders could claim carbon credits for the operation. The challenge is to develop a methodology that produces a science-based estimate of the captured carbon.

Scientific verification for cyanobacteria remediation

In March, BlueGreen received approval from the Social Carbon Foundation for its carbon quantification methodology, under the proprietary name Net Blue. Social Carbon manages the trademarked greenhouse gas standard by the same name.

“Net Blue is the first deep water, nature-based climate solution for atmospheric carbon removal that is regulatory approved, scientifically validated and, now, verifiable by industry standards,” BlueGreen asserted in a March announcement. 

The company has been remediating cyanobacteria since 2019, for an estimated 3.3 million tons of carbon removal. With the Social Carbon standard in hand, BlueGreen can now market cyanobacteria remediation as a verifiable carbon offset.

According to BlueGreen CEO Eval Harel, the worldwide potential for cyanobacteria remediation offsets adds up to about 115 gigatons of carbon.

Natural vs. unnatural carbon capture

The emergence of verifiable cyanobacteria remediation credits should help meet the growing demand for carbon credits. The current demand for carbon credits already exceeds the supply, and BlueGreen projects a 15-fold increase in demand for carbon credits by 2030 and a 100-fold increase by 2050.

Cyanobacteria remediation could also help further undercut the case for carbon capture and storage (CCS). CCS has been promoted as an effective pathway for preventing greenhouse gas emissions from coal power plants and other industrial sources. However, the idea of capturing carbon and storing it in underground formations is rapidly losing currency.

BlueGreen offers a fast-acting, scalable carbon capture system that requires no infrastructure. The algaecide can be deployed swiftly to provide additional benefits for local businesses and recreational users, as well as restore biodiversity and protect public health.

In contrast, carbon capture and storage systems offer no such local add-on benefits, and their ability to scale up globally has yet to be proven. In particular, it is difficult to see how CCS infrastructure fits into the rapid decarbonization picture, due to its relatively high costs and long timeline for construction. Typically, CCS systems also require new pipelines to ship captured carbon from the source to a distant storage facility. That raises the threat of environmental impacts related to construction of the pipeline, as well as delays due to public opposition.

The U.S. already has one massive carbon capture failure under its belt, the FutureGen CCS project in Illinois. It kicked off in 2003 with support from the U.S. Department of Energy, intended to provide a showcase for technology to capture and store carbon from a coal power plant. The project was abandoned in 2015.

Since then, new alternatives have emerged in the field of carbon capture, utilization and storage systems (CCUS), which can convert captured carbon into new products that recycle or sequester it, at least temporarily. Recycled-carbon products also help reduce the need to draw virgin petrochemicals from underground.

Fuels, fabrics, perfumes and vodka are among the new recycled-carbon products coming to market, made from carbon collected at industrial sources or drawn from ambient air by CCUS facilities.

The International Energy Agency (IEA) expects CCUS activity to pick up considerably in the coming years, from just 35 systems in operation globally today to an estimated 200 in the pipeline by 2030. 

What about the trees?

Despite all the forthcoming activity, IEA does not foresee CCUS playing a leading role in the effort to achieve a net-zero economy.

“Nevertheless… CCUS deployment would remain substantially below what is required" for a net-zero scenario, IEA concluded in a 2022 report. The need remains for a broad expansion of swift, effective decarbonization pathways across the board.

The Social Carbon Foundation is among those working to steer the decarbonization conversation into a more holistic framework that can achieve global progress on a larger scale. Through its Social Carbon standard, the organization advocates for nature-based decarbonization pathways that, like BlueGreen, provide local benefits. The localized nature of this approach requires the standard to be flexible and take political and social elements into account.

“Projects using our standard go beyond carbon, embedding meaningful social, environmental and economic benefits to the projects and their local stakeholders,” Social Carbon's website reads. 

“The trademark communicates that emissions reductions result from efforts that benefit and improve living conditions for stakeholders involved in climate change projects, in ways that strengthen their welfare and civic consciousness without degrading their resources base,” it continues. 

That reference to resources appears to be a cautionary note against tree-planting programs that focus on commercial timber plantations as a carbon sequestration tool, to the detriment of local habitat. Scientists have also raised concerns about the pace and efficiency of carbon capture through forestation.

Planting trees is likely to continue to hold a place in the carbon market, but companies seeking to burnish their reputation with forestation will need to ensure that their projects adopt a holistic approach that supports local communities.