Biochar Overview

Biochar can be defined as a charcoal produced for some biological purpose, generally to improve soil fertility or animal feed. It it created using a process known as pyrolysis, heating biomass in a low oxygen environment. Once the pyrolysis reaction has begun, it can be largely self-sustaining if the process is well designed, requiring no outside energy input. Byproducts of the process include syngas (H2 + CO), minor quantities of methane (CH4), tars, organic acids, pyroligneous acid (wood vinegar) and excess heat.

Soil Fertility

Once it is produced, biochar can be incorporated in soil or potting medium for example. Biochar has a number of agricultural benefits. It increases crop yields, sometimes substantially if the soil is in poor condition. It helps to prevent fertilizer runoff and leeching, allowing the use of less fertilizers and diminishing agricultural pollution to the surrounding environment. It retains some moisture, possibly helping plants through periods of drought more easily. Most importantly, it replenishes exhausted or marginal soils with organic carbon and fosters the growth of soil microbes essential for nutrient absorption.

Environmental Benefits

Studies have demonstrated that particularly in certain soil conditions, for instance if clay and calcium is present such as in Terra Preta soils, the carbon in biochar remains stable for millenia, providing a simple, sustainable means to sequester historic carbon emissions that is technologically feasible in developed or developing countries alike. The syngas and excess heat can be used directly or employed to generate a secondary source of energy.

Healthy Livestock

Biochar can also be added to animal feed to improve the health and productivity of livestock. Biochar helps ensure the proper functionality of the gastrointestinal tract, particularly when animals consume feed that may contain herbicides or pesticides. Concentrating livestock in pens or poultry barns greatly increases the likelihood of bacterial infections. Supplementing feed with charcoal is a practice that has been used and studied for at least 100 years. Farmers old enough to be around when charcoal was produced in open heaps tell stories from their youth of how cows would congregate around the residue from such pits to eat pieces of char left behind.

Antimicrobial resistance (AMR) is one of the world’s most pressing health issues. Resistant strains are becoming more common, and increasingly difficult to combat with known antibiotics. At current trends, more people will die of uncontrollable bacterial infections than any other cause in the near future. The wholesale use of antibiotics in animal feed and water, particularly for chickens and pigs, contributes significantly to this problem. Hence, regulatory agencies have begun to ban this practice, and alternatives are urgently needed. Research has shown that biochar can be an effective, economical means of suppressing pathogenic intestinal bacteral loads in animals, outperforming antibiotics in some studies.

In addition, the use of biochar mixed into poultry bedding significantly reduces concentrations of air-borne ammonia in poultry barns. Ammonia causes a variety of health issues for poultry, including respiratory and eye diseases. When the weather is warm enough, poultry farmers use giant fans to force sufficient air circulation to get rid of the ammonia, but in colder weather when barns must be heated, ensuring sufficient air circulation can be problematic. Used poultry bedding can be composted, and the biochar cascaded into use as a soil amendment.

Urban Trees and Landscapes

Trees are vital to cities and towns. Neighborhoods with healthy trees have less crime, more employment and business activity, cleaner air, and their human inhabitants are happier and more productive. However, maintaining a healthy population of trees in a city is easier said than done.

The first problem is that they are often planted in compacted debris left over from construction. Perhaps a small planting hole is dug for the sapling and filled with topsoil, but as the tree tries to grow, its roots cannot grow and/or have no access to the minerals it needs. It is common for heavy construction machinery to drive over the potential root zones of urban trees.

A further problem is that tree roots are often situated under sidewalks, streets and parking lots, with only a relatively small opening around the trunk to allow rainwater to penetrate to the roots. Hence urban trees are typically starved of both nutrients and water, with little space for their root systems.

The City of Stockholm has developed an innovative project whereby large planting / drainage pits are created around their trees. These pits are filled with layers of stone and biochar. Each pit has its own stormwater drain. The creation of these biochar pits is expensive, but the cost is more than paid for by the money the city saves from being able to signficantly reduce its stormwater processing capacity. The trees planted in biochar are vibrantly healthy.

All open parks with grass are being re-landscaped with a mix of biochar, small pebbles and some compost. The grass remains healthy because the biochar-pebble "soil" can't be compressed. Well trodden paths remain green. And heavy vehicles do not leave a destructive imprint, even if the biochar-pebble substrate is soaked with rainwater.

Biomass Waste Streams

Biomass waste is often costly to deal with, and regulation increasingly demands that it be dealt with properly. Biochar production offers an opportunity to transform a cost into revenue. Here are a few examples.

Sawmills and forestry operations have a large amount of wood to dispose of, including rounded slabs, branches, shavings and sawdust. When piles of these residues accumulate, fires can spontaneously ignite from the microbiological heat generated within the pile. These fires can burn for months and cost hundreds of thousands to millions of dollars to put out. A co-located biochar production plant can generate biochar and wood vinegar for sale while providing heat for the mill's lumber drying kilns.

Wherever livestock is concentrated, manure accumulates. Animal manure causes nitrate and phosphate groundwater contamination, even if it is spread on surrounding fields as a bio-fertilizer, and farmers are increasingly required by regulation to prevent this from occurring. A co-located production plant can transform the manure to a nutrient rich biochar where the minerals are bound to the OH functional group lattice provided by the char, while simultaneously providing heat for the poultry barns or other farm infrastructure.

Processors of nuts such as almonds, walnuts, peanuts, macademia and coconut can transform the shell waste stream into both biochar and activated carbon. Fruit orchards, coffee and cacao plantations have annual tree trimming residue, husks and old uprooted trees that can be transformed to biochar. Since orchards are all high value agriculture and many tend to be located in regions with marginal soils, the biochar and wood vinegar produced is likely to be used in these orchards rather than sold.

Effect of Biochar on Soil Fertility

Below are a series of photos demonstrating the effect of biochar on soil fertility. They were taken during the International Biochar Initiative Conference held in Terrigal, Australia from April 29 to May 2, 2007. The test plots shown in the photographs compare the following parameters in 2 replications, labeled a and b, after 10 weeks:

1. Plain soil
2. Soil + NPK (Nitrogen, Phosphorous, and Potassium fertilizer)
3. Soil + Biochar
4. Soil + NPK + Biochar

The application rate of biochar on the test plots 3 and 4 shown below is 50 tons per hectare. While that high an application rate is unaffordable at commercial scale for corn, this early experiment demonstrated biochar's potential to have a significant effect on soil fertility and plant growth. Financial viability can be achieved by some combination of targeting high value crops or scenarios, optimizing the biochar production and application technique, cascading use, such as an animal feed supplement that becomes part of a manure compost, and innovation, such as the Stockholm biochar tree pits financed by serving as a distributed water filtration system.

Similar effects are seen in a variety of soils and locations throughout the world.