There is a school of thought that we won’t be able to slow down human carbon emissions fast enough to prevent the worst effects of climate change. A combination of reforestation and sequestration machines could help pull the atmospheric carbon dioxide ppm concentration down. Is large-scale carbon capture a difference-maker?

To define a key concept, Daniel M. Alongi writes: “Carbon sequestration is a term used to describe the acquisition and storage of carbon. It refers most often in relation to the ability of ecosystems to reduce the impact of increasing carbon dioxide concentrations in the atmosphere.” 

As humans have expanded globally, more carbon storage forests have been cleared to make room for homes, industry and agriculture. There will always be competition for the real estate needed for large carbon sinks. It might be beneficial to look for lands to reforest that aren’t as desirable for building development.

Natural carbon capture

Alongi’s paper — “Carbon sequestration in mangrove forests” (https://bit.ly/3k09HfR) — describes how mangrove forests specifically are excellent at capturing carbon. Mangrove ecosystems (trees and shrubs in coastal intertidal zones) can store at least double the carbon than boreal, temperate or tropical ecosystems. 

They grow in the water along subtropical and tropical coastlines, which are generally used for agriculture, except shrimp farming. In a sense, they are more likely to be out of the way of human development.

Coastal mangrove forests also prevent erosion, wind and reduce wave height by as much as two-thirds. The Mangrove Action Project called them “nature’s shock absorbers.” Beyond the carbon capture benefits, mangroves protect from other natural disasters. The downside is that there isn’t endless coastline to recover with mangroves. The bigger fight will be to preserve the mangroves that exist today and reclaim areas, when possible. 

Another natural carbon capture option could scale better — seaweed. 

"Seaweed can play a huge role in fighting climate change by absorbing carbon emissions, regenerating marine ecosystems, creating biofuel and renewable plastics as well as generating marine protein,” states author Melissa Godin in Time magazine. 

Like mangrove forests, seaweed forests don’t need fertilizer or irrigation. Unlike mangroves, they can be farmed in deeper, colder water. The many varieties of seaweed also can be grown in some rivers and lakes.

A significant benefit of seaweed is that it can be harvested and used for a variety of products. The National Oceanic and Atmospheric Administration notes that seaweed is full of vitamins for food; contains anti-inflammatory agents; and includes emulsifiers for things such as toothpaste, cosmetics and even your McDonald’s shake. Carrageenan is one of the ingredients in a McDonald's shake, derived from a seaweed to help thicken milk and ice cream products.

Both mangrove forests and seaweed forests have many upsides but need a specific shallow sea environment. If we could develop something that didn’t need a particular amount of rain, nutrients or soil, more undesirable lands could be reused for carbon capture. Depending on the region, mechanical carbon removal may be the best bet.

Mechanical carbon removal

What about “mechanical trees”? 

 “A forest of 1,200 mechanical ‘trees,’ designed by Silicon Kingdom Holdings and Arizona State University scientists, is poised to pull more carbon dioxide out of the air than any human-made endeavor before it,” explains a Popular Science article on engineering innovations. “Instead of wood, these metal columns (the specific material remains under wraps) use discs made of sorbent, which can absorb three times its weight in carbon dioxide as the wind blows through it.” 

The devices rely on natural wind, so mechanical fans aren’t required to force air over the discs.

The pilot project that Silicon Kingdom Holdings is installing in California claims to be able to remove 1,844 American households’ worth of carbon emissions per year. Reuters adds that SKH claims this process would cost about $100 per ton of carbon captured. This is interesting because the captured high-concentration carbon could be used for things such as fire extinguishers, which use $100 to $200 liquid CO₂ from traditional sources.

Mechanical trees could scale well. If the technology proves out at larger scales, a Physics Today article claims: “A forest of artificial trees capable of capturing as much CO₂ as the Amazon rain forest would be 500 times smaller than the natural version.” While it doesn’t mean we should tear down the Amazon, mechanical trees could be an excellent way to repurpose brownfield sites or other undesirable lands.

Reduce waste to curb climate change

The solution to curbing the worst effects of climate change won’t come in a box. We need a shift away from waste. We will benefit from bringing CO₂ levels down with plants or machines, but the best bet is just to stop using energy poorly.

 Even if every individual on Earth could soak up every ton of carbon they were responsible for in a year, it wouldn’t be a zero-sum game. In some ways, relying on carbon capture is like getting a bigger bucket to bail out a canoe full of holes. The best long-term solution is to fix the holes so less water spills through.

Is pulling existing atmospheric CO₂ back down to Earth enough to stop climate change? No. 

The European Academies Science Advisory Council writes in a 2018 report: “The limited potential for carbon dioxide removal underlines the need to strive as hard as possible to mitigate emissions (through energy efficiency and energy saving by technical and regulatory measures, rapid deployment of renewable energies, land use management, reducing emissions of other greenhouse gases, etc.) to make any need for negative emission technologies more manageable.”

Carbon sequestration technology is definitely worth developing, but it won’t fix everything. The best bet is to look for ways to make the plumbing and heating projects in your scope of work more efficient. If you have some additional free time, plant a forest of kelp and harvest it for milkshake filler.

For additional information, visit these sites:

• Mangrove Action Project video, https://bit.ly/33WrZsH

• Time, “The Ocean Farmers Trying to Save the World with Seaweed,” https://bit.ly/3nURkei

• Popular Science, “The most important engineering innovations of 2019,” https://bit.ly/2GZOuUT

• Reuters, “Do ‘mechanical trees’ offer the cure for climate change?” https://reut.rs/3lGXVqW

• Physics Today, “Negative Carbon Dioxide Emissions,” https://bit.ly/33WXKBK

• National Ocean Service, “What is seaweed?” https://bit.ly/31avb1U

• European Academies Science Advisory Council, “Negative emission technologies: What role in meeting Paris Agreement targets?” https://bit.ly/33ZCNq4