By Jennifer Fetter, Water Resources Educator, Daniel Ciolkosz, PE. Asst. Professor, Edward Johnstonbaugh, Renewables Educator, Olivia Mroczko, Graduate Assistant
Though it has been around since the times of ancient tribes, biochar is only recently becoming a popular topic of discussion among modern home gardeners, commercial farmers, land managers, and wastewater treatment operators.
Traced back to the Amazon basin, indigenous peoples created biochar from campfires, cooking fires, and other sources, mixing it into the ground to create more ideal, fertile soil for agriculture. To this day, that part of the world has some of the most carbon-rich soils across the globe.
Originating from the term “terra preta”, or dark earth, the use of biochar has been around for thousands of years.
What Is Biochar?
Biochar is a fine-grained, black charcoal material. It is different from traditional charcoal mostly in that it is generally designed for use as a soil amendment instead of as a fuel for heating or cooking.
When an organic material, like wood, is burnt, it gives off smoke that contains methane, carbon dioxide, and carbon monoxide gases. These gasses then typically released to the atmosphere.
During the process of creating biochar and charcoal, known as pyrolysis, the smoke given off is captured in a closed system.
That smoke is redirected back to the heat source to add more energy to the charcoal, or an alternative heat source then used as fuel for another process like generating energy. This reduces the amount of air emissions.
Biochar is produced in a controlled environment that leads to a cleaner end-product than traditional charcoal.
Biochar is also lighter weight and has a high surface area compared to charcoal, sometimes exceeding 400 square meters per gram.
If the biochar production process uses fast pyrolysis, a percentage of the gasses are converted to bio oil which can be further processed into other products.
What is Biochar Made From?
The material used as a source for producing biochar is a key point in what makes biochar a popular topic. Many low-value organic materials, often considered wastes, can be converted into this more valuable end-product.
Examples include nutshells and coconut shells, low-quality wood chips, agricultural crop residue, and even poultry manure.
Benefits of Biochar
Biochar has an extensive surface area, physical properties that make it readily able to bond with other substances, and a very-stable structure which makes it long-lasting.
These properties have led to the suggestion that biochar provides many agricultural benefits as well as many water quality benefits. These benefits include:
-- Increased moisture retention in soils
-- This is good for plant growth when there is limited rainfall
-- This is good for water quality because it reduces runoff
-- Increased nutrient retention in soils
-- This is good for plant growth in soils with poor nutrient content
-- This is good for water quality because it reduces nitrogen leaching into groundwater and runoff into surface water
-- Stable storage of carbon
-- It provides a way to sequester carbon from these various organic wastes instead of releasing the carbon into the atmosphere through traditional burning.
-- Very adsorbent surface with many functional groups
-- This means it can capture and filter pollutants out of water, including metals. For this reason, biochar has been successfully used in the wastewater treatment process as well.
Variations in Biochar Effectiveness
There are a lot of reasons why current studies of biochar effectiveness show inconsistent results. This is true for both its ability to benefit crop and garden growth as well its potential benefits to protecting water quality.
-- Variety of source materials - the biomass used, and how it is treated prior to use, can impact the biochar properties produced.
-- Variety of production processes - the speed and temperature that the biochar is produced can impact the end product properties as well
-- Variety of application rates - the amount of biochar used in amending the soil, type of initial soil, and residence time in the soil before measuring its benefits can all impact the results
What Does This Mean for You?
Biochar is fairly commonly available now in garden centers and agricultural supply stores. It may be a soil amendment you could try for enhancing your crops or backyard gardens or reducing your impacts on the environment.
At the very least, you will be helping put carbon back into the soils where it can reside for hundreds of years.
It may also be benefiting our local waterways, which are significantly impacted by nutrient pollution across the United States.
We will continue to follow the studies on biochar effectiveness and provide updates as they become available.
(Reprinted from the Penn State Extension Watershed Winds newsletter. Click Here to sign up for your own copy.)
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