Biochar

Biochar is a type of organic matter made by burning biomass material such as wood, plant matter, manure, or leaves slowly and stopping the burning process when the material reaches the charcoal stage. The charcoal stage occurs right before the material turns to ash. The burned material resembles charcoal that is used to start a fire. Biochar is used as an additive to enhance soil and help it retain carbon and other nutrients. It differs from regular charcoal, which is mostly used for fuel.

History

Biochar can be traced back thousands of years to the indigenous tribes that lived in the region of the Amazon River basin around 500 C.E. The tribes grew crops, such as cassava and corn, and fruit trees along the Amazon River. The soil they used contained charred plant matter (biochar) that kept it rich and fertile. Scientists, however, are unsure if the tribe members added the biochar deliberately because they knew of its properties or if it was accidentally added to the soil to get rid of unwanted matter. Some scientists believe a method called slash-and-char farming was used instead of slash-and-burn farming. The slash-and-char method created charcoal instead of ash. This charcoal was used in the soil.

The Europeans eventually arrived to colonize the lands near the Amazon River. They brought diseases with them that killed many indigenous people. The slash-and-char farming method was no longer used nor were the fields of charcoal.

During the twentieth century, large fields of black soil were discovered near the Amazon. This soil was called terra preta, which means "dark earth" in Portuguese. It was rich in plant nutrients, such as calcium, magnesium, nitrogen, and phosphorous. It remained fertile, despite the tropical climate and abundance of rainfall in the Amazon region. Scientists determined that terra preta was man-made and began to study its properties.

In addition to the region of the Amazon River basin, biochar was found to have been used in Japan for thousands of years. Its use only recently garnered attention again in the country, and scientists in Japan continue to study the benefits of biochar.

How Biochar Is Made

Biochar is made by burning organic material, such as wood, plant matter, manure, or leaves, using limited oxygen and at lower temperatures (less than 700 degrees Celsius or 1,300 degrees Fahrenheit). This low-temperature, controlled burn is called pyrolysis.

People can make biochar right in their own backyards. First, a trench should be dug for a planned garden. A pitchfork should be used to loosen the soil. Next, the organic matter to be burned—such as plant material or brush—should be placed in the trench and set on fire. The fire should start out hot but then the oxygen supply should be reduced to slow down the fire quickly.

Watching the smoke is the key to doing this correctly. White smoke at the start of the fire contains water vapor. When resins and sugars in the plant matter are burned, the smoke turns yellow. The smoke then gets thinner and turns a grayish-blue color. At this point, the oxygen supply to the burning material should be cut. This can be done by covering the fire with some soil. The fire should not be put out completely but left to smolder (burn slowly without flames). When the fire gets to the charcoal stage (right before the material turns to ash), it should be put out with water. Wood also can be burned in metal barrels to make charcoal by mostly the same process.

Biochar and the Environment

Biochar's main use is to improve and enrich soil, although its use has many benefits for the environment. Scientists discovered that the holes, or pores, in biochar act as houses for microbes, fungi, earthworms, and other creatures. These organisms help to increase the carbon content in the soil. Instead of the carbon from decomposing plant matter escaping into the atmosphere in the form of greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, the organisms in the biochar help to keep the carbon in the soil and mix the carbon throughout the layers of soil.

This process has the potential to lessen the amount of greenhouse gases entering the atmosphere, helping to reduce global warming. One ton of biochar in the soil can hold at least three tons of carbon. Biochar releases carbon ten to one hundred times slower than decomposing organic matter.

Biochar also helps soil retain more water. Most biochar does not add nutrients to soil. It helps to promote microbial growth in soil. This allows the soil to retain nutrients for plants. However, biochar made from bones and manure does add some nutrients to the soil. Using biochar reduces the need for fertilizer because it allows the soil to retain nutrients for longer amounts of time.

Much research is under way in the United States and other parts of the world to determine how biochar can be used to promote the growth of crops and reduce greenhouse gas emissions. While organic matter is needed to produce biochar, this can be gathered in ways other than cutting down forests and clearing fields. Organic matter such as crop residues, yard and food waste, and animal manure can be utilized to make biochar.

Bibliography

"Biochar Overview." Biochar Info. CarbonZero Project - Switzerland. Web. 15 Feb. 2016. http://www.biochar.info/biochar.biochar-overview.cfml

Cox, Jeff. "Biochar: An Ancient Soil Amendment Is New Again." Rodale's Organic Life. Rodale Inc. 10 May 2013. Web. 15 Feb. 2016. http://www.rodalesorganiclife.com/garden/biochar

"Introduction." Biochar.org. Biochar.org. Web. 15 Feb. 2016. http://www.biochar.org/joomla/index.php?option=com‗content&task=view&id=67&Itemid=7

Pleasant, Barbara. "Making Biochar to Improve Soil." Mother Earth News. Ogden Publications, Inc. Feb.–Mar. 2009. Web. 15 Feb. 2016. http://www.motherearthnews.com/organic-gardening/making-biochar-improve-soil-zmaz09fmzraw.aspx

"What Is Biochar?" International Biochar Initiative. International Biochar Initiative. Web. 15 Feb. 2016. http://www.biochar-international.org/biochar