Why Biochar?

There is no question that climate change is a major issue for the world today. Global average temperatures have increased 0.8 °C (1.4 °F) in the past 100 years. This change in temperature has already reduced ice coverage and caused significant sea level rise, and is projected to cause further reduction in arctic sea ice, higher sea levels, destruction of sensitive habitats, especially in coastal areas, and extinction of many species. One of the root causes of climate change is the global increase in carbon dioxide. This greenhouse gas has been produced by humans on a large scale since the industrial revolution, raising the average CO₂ concentration from 280 ppm to 400 ppm. While many people agree that it is necessary to reduce the amount of CO₂ in the atmosphere, there is debate about how to go about removing and storing it. One of the newer ideas is to sequester carbon by converting biomass, such as wood, into biochar, which is stable enough to store for long periods of time. This would effectively offset the atmospheric CO₂ concentration by removing the carbon from the carbon cycle. Storing carbon as biochar is currently the most practical option for implementation on a large scale, because it does not require advanced technology, the resulting carbon has other uses including use as a soil improvement, and the carbon will remain stable for long periods of time.

Several other ideas have been proposed to reduce net global CO₂ emissions. The most accepted ones all involve removing the CO₂ directly and storing it. Commonly proposed ideas for storing it include injecting it into dry oil wells, injecting it into saline aquifers or dissolving it into the deep ocean. In fact recently, the US government has proposed a plan to require coal power plants to remove the CO₂ and sell it to oil companies to inject into the ground. Proponents argue that it is the most convenient way to store the CO₂, as the oil wells are already there, and the CO₂ is unlikely to escape. They also suggest that companies would be able to profit from this as oil companies would be able to purchase CO₂ and inject it into oil wells, which would force out more oil. Supporters of dissolving CO₂ in aquifers insist that saline aquifers are useless otherwise, and CO₂ is unlikely to escape because saline aquifers have existed for thousands of years. Others believe that ocean storage is the best option because it could store a much larger volume than other ideas, and would be cheap because it would not require drilling.

Unlike several other proposed methods of lowering CO₂ levels, the use of biochar does not require advanced technology. Separating biochar from organic material only requires that the material be heated without any oxidizing gasses. Unlike other proposed ideas, which require new and/or complex ideas to scrub CO₂ from the air, biochar utilizes the existing abilities of trees and other plants, and uses technology that is already proven and very well understood. It also doesn’t require any complex technology to store. Since biochar is stable on its own for 1000 years or more, it does not require advanced or expensive technology to store. It can simply sit and provide a long term carbon sink, unlike other technologies which capture CO₂ directly and require immense effort to store.

Most other ideas for reducing CO₂ suggest that the CO₂ be injected into geological formations such as empty oil or gas fields or underground saline aquifers, or injected into the deep ocean where the water pressure would keep the gas in solution.  Storing it in oil fields is relatively easy and the cost would be offset by the oil that would be forced out by the CO₂, but burning the resulting oil would offset a large amount of the carbon stored, and oil fields have a very limited capacity. Saline aquifers are not very well studied so the risks are largely unknown, but the costs would be high as this would require drilling deep underground. Storing CO₂ in the deep ocean contributes to ocean acidification. Using biochar is a much more practical alternative because it uses simple, cheap technology, and can be stored with little to no cost or effort.

In addition to its ability to reduce atmospheric CO₂, biochar has other benefits including use as a soil improvement and production of bio-oil as a byproduct, unlike other methods of storing carbon which provide no additional benefit. Biochar can help increase the fertility of soil by preventing nutrient loss and reducing the need for nitrogen-based fertilizers, which are expensive and harmful to the environment. Biochar also absorbs other harmful greenhouse gasses, such as methane and nitrogen dioxide, as well as contaminants such as pesticides and metals, which would otherwise be absorbed by plants. Additionally, biochar also reduces irrigation requirements by increasing the water retention of the soil. Finally, the creation of biochar produces flammable gasses and oils that could be used to power the creation of more biochar or could be refined into fuel for use in heating or transportation. Biochar not only provides the main benefit of offsetting  atmospheric CO₂, it reduces additional greenhouse gas emissions, reduces the need for fertilizer and irrigation, both of which are damaging to the environment, makes crops healthier by reducing contaminants, and opens up the use of degraded of infertile soil that would otherwise be useless.

Biochar is nearly certain to be stable and safe for long periods of time. Biochar is very stable in nature and can remain in soil for thousands of years. Additionally it cannot release large amounts of carbon at once unless it is burned. Other methods are not nearly as reliable.

Deep ocean storage is the least reliable as the carbon will be released when it moves closer to the surface and the pressure decreases. Additionally it is possible that natural processes could trigger a massive release of carbon, which would not only reverse the effects of storing the carbon, but would also have the potential to kill people by asphyxiation.

Storing CO₂ in saline aquifers could allow it to escape easily if the aquifers connect to surface water or oceans. Since most saline aquifers are not well studied, the amount of time it would take for carbon to escape is unknown and would likely vary significantly between aquifers. This means that each aquifer would need to be studied in detail in order to determine suitability.

Storage in dry oil wells would probably be stable for long periods of time, but there is still a possibility that CO₂ could escape through geological features. Additionally, the CO₂ would be released suddenly if the well were opened accidentally or by a natural disaster such as an earthquake.

While biochar would not actually sequester any CO₂, it would effectively reduce net CO₂ emissions by preventing the carbon in biomass from being released as CO₂ when it rots or burns. This method would be able to offset the CO₂ production of a power plant much more easily and cheaply than by storing the CO₂ itself. A 600 MW coal power plant produces 3.5 million tons of CO₂ per year. In order to offset this, 2-4 million tons of biomass would need to be turned into about 1 million tons of biochar. Additionally, this would not require any energy input because the bio-oil and gas output contains more than enough energy to produce biochar, unlike carbon capture, which can use up to 20-25% of a power plant’s total output.

This evidence shows that biochar is a practical method of offsetting atmospheric CO₂ because it is the most cost-effective, has additional environmental benefits, and is known to be stable for long periods of time.  Because of this, I would recommend a pilot of this process on the scale of a small power plant. The operating costs would be low, similar to the costs of running a charcoal plant, unlike the plant built recently in Mississippi that uses direct capture and storage in oil wells and cost 4.7 billion.