strategy to address climate change, but it can serve as one part of a
multipronged approach to mitigating climate change.
We present two classroom experiments that investigate the effect
of biochar on soils and plants. We align these activities with NGSS by
integrating disciplinary core ideas, science practices, and crosscutting
concepts. The activities’ objectives are to
• gain an appreciation for soils as an important natural resource;
• explore issues in soils and agriculture and examine biochar as a
• manipulate soil properties and biochar amendment to investigate impacts on soils and plants; and
• conduct an experiment, collect and analyze data, and engage in
scientific inquiry to interpret real-world data.
Properties of Biochar
Biochar is produced by breaking down organic matter under high
heat ( 250–700°C) and limited oxygen (Lehmann & Joseph, 2015).
Biochar is often a coproduct of bioenergy derived from naturally
renewable organic matter sources, including agricultural products
such as crop and animal wastes and nonagricultural products such
as woody biomass and algae (Table 1). The physical and chemical
properties of biochar vary depending on its source and how it is pro-
duced. Different sources and production temperatures yield biochars
with different surface areas, pore sizes, pH values, and carbon con-
tents. Biochar surface area is a function of pore size, with smaller pore
size resulting in higher surface area. Pore size, and thus surface area, is
controlled by the temperature at which biochars are produced (Leh-
mann & Joseph, 2015). As a consequence of this variability, not all
biochars interact with the environment in the same way. Students
can draw on their understanding of the variable properties of biochar
to explain their own experimental results.
Biochar is easy to obtain from garden stores or online (https://
www.biochar-international.org). Teachers should read the material safety data sheet provided by biochar producers and handle
biochar appropriately. Dust inhalation is an important but manageable safety concern. We recommend purchasing pelletized biochar products or products with >3 mm particle size. To minimize
dust, take care when opening a bag of biochar as dust may accumulate during transport. Wear facemasks and gloves when handling raw biochar. Spraying or adding small amounts of water
to biochar can reduce dust. Students can observe large pellets of
biochar under the microscope and handle the materials after the
biochar has been added to soils.
Figure 3. The natural carbon cycle (left) compared with the biochar carbon cycle (right). In the natural carbon cycle, carbon
withdrawn from the atmosphere through photosynthesis is balanced by carbon released to the atmosphere through respiration.
In the biochar carbon cycle, a portion of the carbon withdrawn via photosynthesis is used for bioenergy production, which results
in a biochar coproduct that can be sequestered in soils. (Credit: redrawn and adapted from Lehmann, 2007)