By: Camryn Fujita
A Factory Smokestack in New Jersey
Source: UN Photographer John Isaac
One of the most diverse and talked-about strategies to combat the effects of climate change is utilizing an affordable and realistic method to capture and store carbon emissions until we can shift our industries and livelihoods to rely on a more sustainable source of energy than fossil fuels. Carbon sequestration is the natural and deliberate process of securing carbon dioxide in a stable form (solid or dissolved) to prevent it from entering the atmosphere and contributing to warming and the greenhouse gas effect. The principal greenhouse gases that trap heat in the atmosphere include water vapor, nitrous oxide, methane, and fluorinated gases. However, it is carbon dioxide from burning fossil fuels for transportation, that consistently makes up the largest percentage of greenhouse gas emissions. In 2019, the U.S. Energy Information Administration estimated that about 63% of electricity generation came from fossil fuels (i.e. coal, natural gas, petroleum, and others). Furthermore, the United States has one of the highest carbon emissions per capita and is therefore consistently responsible for the second highest total carbon emissions in the world, after China.
Before industrialization, carbon “sinks” in the natural world: forests, oceans, and soil, sequestered and released atmospheric levels of carbon dioxide at a level rate. Many may be surprised to learn that today, oceans actually sequester about 25% of carbon dioxide emitted by humans due to biological processes of aquatic animals and plants. Increasing carbon emissions, however, are placing a strain on this natural carbon sink. Studies suggest that colder and more nutrient rich areas of the world’s oceans act as greater carbon sinks, therefore water near the poles and waters that host lots of plant and animal life may be absorbing a disproportionate amount of carbon, thereby altering the acidity of the water and disrupting fragile ecosystems. Another lesser known carbon sink is the Earth’s soil. Natural processes of photosynthesis and decomposition regulate the carbon absorption and release in soil. Soil carbon levels indicate the amount of organic matter in soil, encouraging greater carbon fixation and therefore encouraging plant growth. Finally, the most commonly known carbon sink is our planet’s forests. Trees are often cited as one of the best and cheapest ways to mitigate humanity’s carbon footprint, especially in urban areas. The natural process of photosynthesis means that plants capture and utilize atmospheric carbon dioxide to create glucose (sugars) necessary for growth. The value of Earth’s forests in storing carbon is well documented. Today, 25% of global carbon emissions are captured by forests, grasslands and rangelands. Carbon dioxide is released back into the atmosphere and soil when vegetation dies and decomposes. Maintaining and protecting forests is important because irresponsible deforestation and frequent forest fires can transform the carbon sink into a carbon source.
Advances in technology have allowed scientists to develop man made methods of sequestering carbon. Geological carbon sequestration is the strategy of capturing and liquidizing carbon emissions from industrial facilities, and then injecting it into permeable geologic formations deep underground, and then covering the sequestered carbon with impermeable rock to be stored for a long period of time. Other strategies being explored include developing direct air capture (DAC) technology, engineering molecules capable of capturing carbon from the air, and technology that sequesters carbon and combines it with hydrogen gas at extremely high temperatures to create graphene production.
The big question is, can carbon sequestration, alone, reverse the course of climate change and temper the unchecked growth of human emissions? The answer is no. The U.S. Climate Change Science Program (CCSP) estimated that emissions over the next century may have to be reduced by 75% in order to maintain emissions levels at an environmentally healthy level. The conclusion they drew is that “carbon sequestration is necessary but insufficient to control atmospheric CO2.” Keeping carbon emissions at a reasonable level will require a complete overhaul in the world’s energy infrastructure, drastic shifts to the type of fuels on which our society relies, and intense carbon management.
Nonetheless, scientists have continued to explore avenues for maximizing Earth’s natural carbon sinks. For example, over the years, scientists have found that soil has been losing significant amounts of its carbon stock due to overgrazing and overfarming. When soil is exposed to the air it oxidizes and burns the soil carbon into carbon dioxide. Without soil organic carbon, soil becomes dirt: useless in agriculture and susceptible to erosion. Accelerating the carbonate forming process by adding silicates to the soil enhances the ability of soil organic matter to store carbon for several decades and of carbonates to store carbon for more than 70,000 years. Conscious carbon farming practices include greater emphasis on composting, using “conservation tillage” methods, and diverse crop rotations, and more to ensure that soil remains carbon-rich.
There has been some debate over and experimentation with various afforestation and reforestation strategies to maximize the carbon sink that is our Earth’s forests. Many scientists believe that the preservation of existing forests is an essential tool in addressing climate change. However, some wonder how effective and realistic massive afforestation, or planting trees to create a forest where there was previously no tree cover, could be. In 2019, “The global tree restoration potential” by Swiss scientist Jean-Francois Bastin suggests that the Earth’s ecosystems could support an additional 900 million hectares of continuous forest and argues for “global tree restoration as one of the most effective carbon drawdown solutions to date.”
Some scientists believe that resources would be better used if they were on maintaining and protecting existing forests and introducing limits to carbon emissions instead, raising an interesting schism in the conversation about carbon sequestration and climate change mitigation. Some scientists caution that planting billions of acres of trees sounds like a great idea in theory, but an implementation of such a project requires much more careful planning and thought than may seem necessary on surface level. Some questions these scientists believe should be considered are: “How long will this approach take to make a dent in atmospheric carbon concentrations? Can grasslands and savanna ecosystems sustain increased tree cover? How might converting non-forest land to forests compete with food production? How much time, money and resources will it take to implement a global forest restoration of this magnitude? How do the costs of adopting such a climate mitigation strategy stack up against its potential benefits?” Others only see the usefulness in massive afforestation, if the problem of rapid deforestation is addressed first.
The caution advised for massive afforestation projects shows that large tree-planting projects require strategic planning, and must have long-term support in order to be successful. The scientific debate over where resources are best put to use in the fight against climate change also highlights the urgency of the crisis and the importance of including a wide range of climate scientists and ecologists in policy decision-making. Learning about carbon sequestration strategies and relevant debates in the scientific realm allows the public to understand that unfortunately, as much as we would like it to be an easy fix, addressing climate change seriously will take much more than planting a bunch of trees.