Biocharmed: is biochar living up to its expectations?
Many modern practices in agriculture are inherently unsustainable. Over the last 10,000 years, intensive farming has caused many cultivated soils to lose up to 70% of their original organic carbon. Common farming techniques like monocropping and excessive tillage have contributed to soil loss and erosion; currently, farms in the US are losing twice as much topsoil to erosion per year as the Great Plains lost in a typical year at the height of the 1930s Dust Bowl
As the quality of soil decreases, a farmer’s dependence on agrochemicals and fertilizers must increase. However, because the lower quality soils do not retain moisture or nutrients as well, these chemicals and petroleum based fertilizers enter waterways as runoff. The more work that must be put into preparing land for growing, the more fossil fuels must be used to complete the tasks — as it is, the carbon dioxide output of industrial agriculture in the US makes up 10% of out overall greenhouse gas emissions. As climate change worsens, this sector will have to look more closely at how to continue improving their practices while also cutting back on their greenhouse gas emissions.
Between the warming climate and the loss of soil quality, the challenges that face modern farming today may seem insurmountable, but humans have been coming up with innovative and effective solutions to grow more food for many thousands of years. What if there was a tool that could both remove carbon dioxide from the atmosphere while improving the quality of soils?
The study of soils in the Amazonian region of Brazil has revealed that charcoal, added to the poor soil in that area thousands of years ago, still positively impacts the quality and productivity of that same soil today. Terra preta, Portuguese for “black earth”, was created intentionally by indigenous people who incorporated wood charcoal and other organic matter into the top layer of earth.
As a result, the carbon content of the soils increased, making the land more productive for growing crops. Healthy soil is characterized by a high carbon level, which creates a porous and spongy texture that allows water to be absorbed and nutrients to be stored. Terra preta soils have three times more soil organic matter, nitrogen, and phosphorus, and 70 times more charcoal than the adjacent, non-amended soils of the Amazon region. Biochar is a type of charcoal that can have the same significant impact on soil health and productivity, while also acting as a more effective natural carbon sink.
Biochar is a member of the black carbon family with activated charcoal and others. It can take on a variety of characteristics depending on how it is made and what was used to make it. Biochar is created using a process called pyrolysis, during which the material is burned in a minimal oxygen environment. Typically, it is made of organic waste products, materials like woodchips or agricultural byproducts (nut shells, straw, animal manure).
The process of pyrolyzing the materials creates a solid residue that resembles charcoal, as well as biofuel as a byproduct. The oil and gas created can be used as an input to create more biochar, which means that the process is self sustaining. The ratio of biochar to biofuel depends on the process; burning the materials faster produces more oil and synthetic gas, while a slower burn time creates more biochar
The biochar itself does not absorb carbon after it is produced. It is a chemically stable form of carbon that keeps it solid instead of in gas form as carbon dioxide. Because of the way the stock is burned (pyrolysis), the biochar keeps a high amount of its original carbon, which can then be added to soils as an amendment or buried in order to remove it from the carbon cycle. For example, plants can absorb one ton of carbon dioxide, but as the plants die, their waste usually decomposes, returning that one ton of carbon to the carbon cycle. If the plants are instead burned using pyrolysis, more carbon stays in a solid form as biochar, which then can be “put away” underground. It also has the ability to enhance the carbon storage potential of soils, as plants can deepen their roots and more life can be sustained underground. And because the creation of biochar is self sustaining, the maximum amount of carbon can be stabilized and stored away if the optimum materials and process is used.
There are uses and benefits of utilizing biochar beyond sequestering carbon and improving soil quality in order to produce more food. The application of biochar has also been reported to reduce a considerable amount of methane and nitrous oxide emission from the agricultural — two potent greenhouse gasses. It can also be used to scrub heavy metals from soils, industrial emissions, and wastewater.
Using biochar as a way to take carbon out of the atmosphere has the critique that soils can only hold a finite amount of carbon; it is not the “silver bullet” to solving climate change. Because there is not just one type of biochar, there is only a primary understanding of the characteristics and capabilities of each type made from different stocks and with different techniques. If the soils are disturbed in the wrong way after the application of biochar, then the soil could release carbon — therefore, appropriate soil management would need to continue indefinitely. These factors, as well as the cost and challenge of monitoring and verifying the amount of carbon being removed from the atmosphere, makes using biochar for large scale sequestration projects a risk.
The technicalities and logistics of burning and burying huge amounts of organic waste are daunting, making it an economically poor choice for the time being. However, there seem to be a growing number of small scale biochar producers that are finding success. Later on, the large scale adoption of biochar could make it worth money in carbon trading schemes, creating incentive for companies to purchase biochar to offset their own emissions. This would lead to the displacement of crops or even forests for the creation of biochar, which is a huge problem in itself. But right now, the price of using biochar as a general soil amendment for farmers is not worth the economic benefit or risk in the United States. Currently, farmers in China have the added benefit of using biochar to reduce pollution and contaminants such as cadmium; similarly, the economic cost of low quality soil will only increase in the US as well.
A great deal of research must be undertaken to better understand the kinds of social, economic, and ecological impacts using biochar on a large scale could have. Currently, there is exciting research on the kind of impact it has on relationships between plants and nitrogen-fixing bacteria, as well as other soil microbial life. Studies are also underway to create a database that documents how the materials used to create biochar at what temperature can impact its behavior in soil. Its use as a tool in sustainable production systems and climate smart agriculture is being further examined as well.
Biochar use is being explored as a tool beyond solving agricultural problems as well. By adding it to cement mortar, not only is the emission impact of the material somewhat mitigated, it can make the material stronger and more durable. Its usefulness in scrubbing mercury from power plant emissions is documented, as well as its potential to create more effective carbon sinks in urban areas by adding biochar to city soils.
It seems like biochar had a glowing moment in the spotlight a few years ago, and has since fallen out the public eye and possibly even the public favor. There still exists a great deal of potential, though, and the challenges and shortcomings of its use are becoming better understood. Current research may eventually lead to the development of biochar usage standards, and eventually the creation of application and carbon sequestration tracking technologies. The widespread use of biochar may need to initially be encouraged by government and economic incentives, but the demonstrated benefits of biochar’s use seem to be maintaining its promise for the future.
