Biochar can be defined simply as char (charcoal) used in agricultural purposes. It can be produced from any type of biomass, such as agricultural and forestry waste, including wood and manure. Biochar is manufactured in a process called 'Pyrolysis', heating the biomass feedstock in an oxygen deprived environment.
Syngas, a small fraction of the gas, and excess heat are byproducts of the pyrolysis process.. The remainder can be used as a carbon neutral source of energy for electricity, heating, and fuels. Once the reaction is started, it is largely self-sustaining, requiring no additional input of energy.
Once it is produced, biochar is spread on agricultural fields and incorporated into the top layer of soil. Biochar has many agricultural benefits.
Carbon is the most important element of soil fertility. When organic matter is added to soil to increase carbon levels, most of it rapidly decomposes to carbon dioxide and escapes into the atmosphere. Only a very small percentage eventually becomes stable humic matter.
Industrial agricultural practices decrease levels of humic matter in soils. Most agricultural soils are now severely degraded. Biochar provides a stable backbone of carbon that can increase the fertility of soils on a permanent, growing basis.
Adding biochar is a much more efficient way to increase soil carbon levels and fertility. All of the carbon is immediately accesssible to increase fertility, nearly none of the stable carbon added to agricultural soil decomposes, and biochar has a huge internal surface area because of it’s highly porous structure.
At large scale, the hydrogen and carbon present in the syngas (a byproduct of producing biochar) can be recombined to create hydrocarbons, a liquid fuel commonly known as diesel. There are also innovative technologies where the syngas is pumped through a vat of specialized bacteria and the end product is ethanol produced at ideal Energy Returned over Energy Invested ratios.
The syngas and excess heat can also be used to drive standard off the shelf turbines to generate electricity. The power can be used on farm or sold back to the grid. It can also be used to power several innovative flex fuel steam engines to drive irrigation pumps for instance. One of the simplest applications may simply be for space heating, to heat chicken sheds for instance.
The production of biochar has the potential to both save money in energy costs and offset fossil fuel use. And unlike any other form of bioenergy, the more energy is produced with biochar, the more carbon is removed from the atmosphere.
Worldwide, plants absorb 60 billion tonnes of carbon from the atmosphere every year and use it to create carbohydrates and more complex structural molecules. Sustainable carbon recycling leverages this natural capacity to absorb carbon. When biochar is created from plant matter, the carbon in plant structures is stabilized so it does not decompose and return to the atmosphere as CO2. The resulting safe and relatively permanent sequestration of carbon is the key way that biochar helps to mitigate climate change. But there are other synergistic effects that happen as biochar is added to agricultural soils.
As soil health and thus agricultural yields increase, more carbon is absorbed from the atmosphere. Increased agricultural yields from healthy soils decrease the pressure to utilize carbon-intensive agrochemicals. Higher yields also decrease pressures to obtain more farmland, preventing carbon emissions from deforestation and other forms of land use change.
Biochar has also been demonstrated to decrease nitrous oxide and methane emissions from soils in certain cases. Both of these gases have a much more powerful warming effect in the atmosphere than CO2.
Both tangible and intangible benefits, which include the potential for multiple profit streams, arise when we begin to recycle carbon with biochar.
When biochar is created from waste biomass streams and incorporated into agricultural soils, about half of the carbon in the plant matter becomes immediately stabilized in a form that will not easily oxidize to carbon dioxide and return to the atmosphere. This is the first carbon recycling step.
The second step occurs when the other half of the carbon, released as pyrolysis gases, is used to displace fossil fuel use. That carbon is oxidized to produce energy and heat and liberated to the atmosphere.
The third carbon recycling step occurs because biochar very often increases agricultural productivity. As a result, plants produce both more above ground and below ground biomass in their root systems. As a result, the increase in productivity absorbs more carbon from the atmosphere and a portion of that is transferred to the soil as increased organic carbon.
Agriculture and forestry operations produce a variety of biomass waste streams that need to be disposed of. Because the biomass does not have sufficient value, producers use the cheapest way available to them to deal with it, burning it, or leaving it to decompose in large heaps, as in the case of manure.
Biochar holds the potential to convert the financial liabilities of dealing with agricultural and forestry waste into a valuable profit stream when it is used to increase soil fertility and generate bioenergy. The intangible benefits are also substantial, and in certain circumstances these may become tangible as well. Methane and carbon emissions are avoided, while carbon is sequestered on a semi-permanent basis. The health risks posed by biomass burning and groundwater contamination are mitigated as a consequence of profitable activity.