Biochar

Overview

Biochar is biological material that has been charred. Biochar is created when organic matter is pyrolized (baked, not burned) at high temperatures under low oxygen conditions. Unlike charcoal, which still
retains resins which can be burned, the process

of creating biochar drives off the resins and any remaining moisture until what remains is a highly stable form of carbon. Biochar is able to sequester

carbon for hundreds to thousands of years.

As the above photo shows, any number of dried organic materials can be charred.

When viewed under a microscope, biochar looks like a black sponge with numerous pores throughout. These pores provide versatility for the numerous ways in which biochar can be used. Among other applications, biochar can be used as a soil amendment, as a moisture-absorbing desiccant, as a filter for stormwater runoff or sewage, and to absorb odors and ammonia when added to livestock bedding—which can in turn, be used as fertilizer.

Production

There are multiple ways to produce biochar. When making small batches we use the barrel-in-barrel method—also known as TLUD (top lit updraft)—in which a 55-gallon internal barrel contains material to be charred. The outer barrel is filled with fuel, then a lid is placed on the inner barrel to restrict oxygen.

The outer barrel is open at the bottom for airflow, then lit from the top and covered with its own lid and chimney. The burning outer fuel generates enough heat to "bake" the internal contents, creating biochar.

Research Projects

Small Batch Processing

Using metal barrels to produce biochar has its drawbacks. For one thing, metal corrodes

and deteriorates over time. Metal is also a poor insulator for retaining heat, thus less efficient. We will be testing a different method for producing biochar using natural materials that have greater insulating properties and potentially greater durability. As a result, less fuel wood should be needed to generate the same amount of heat.

Volume Processing

We will also explore various options for biocharring large amounts of forest residue, where small batch processing is impractical.

Once biochar is produced and applied to test plots of new saplings, soil samples can be analyzed for fine root development, soil texture, water holding capacity, nutrient availability, and resilience against pests

and disease as compared to control plots without biochar.

Biochar Applications

There are numerous ways in which biochar can be used. The following are but three examples.

It is important to note that the intended use determines whether or not biochar is pre-treated with nutrients before use. The examples below specify when to treat, or not.

As a Soil Amendment

Freshly made biochar is not added to garden soil or fields

in its "raw" state. Rather, it is first combined with compost

or manure for three or more weeks to "inoculate" (or "charge") its pores with nutrients and microbes. The inoculated biochar is then crushed to increase surface area and added to the garden. Over time more soil microbes inhabit the pores within the biochar and continue to improve soil fertility year after year. The photo at right shows biochar added to holes in which we then transplanted strawberries.

Because biochar is so light weight and porous, it is useful for aerating compacted
clay soils and improving soil texture. Biochar's ability to retain moisture also helps
to mitigate the effect of dry spells and, during rainy weather it aids soil drainage. Also,
in contrast to compost which has to be continually replaced as it breaks down and plants
use up the nutrients, biochar has staying power; its carbon structure persists and is able
​to retain nutrients, keeping them available to plants.

As a Desiccant

Although untreated raw biochar is not added directly to soil, it is beneficial in its dry state as a desiccant to absorb moisture. This past fall we mixed raw biochar into a bag of rye grass seed to prevent it from becoming moldy over the winter. In the coming year, we will test its ability to aid in drying harvested plant material. We will also add biochar when storing produce such as potatoes and onions to minimize rotting.

Forestry Benefits

The U.S. Forest Service recognizes the ability of untreated (non-inoculated) raw biochar to:

• reduce excess biomass to reduce the risk of wildfire
• replace slash pile burning to limit smoke and emissions
• improve resilience against drought, insects, disease
• increase tree fine roots, improving nutrient acquisition
• remediate contaminated soils by immobilizing toxins
• create beneficial media to establish new seedlings
• increase soil organisms critical for decomposition
• improve soil texture and fertility
• sequester carbon below ground
• increase biodiversity
• filter water runoff
• retain water 

Other good sources of information include: