Biochar’s original claim to fame is its use as a soil amendment, inspired by Amazonian dark earths (Terra Preta). However, raw biochar itself The applications listed here are some of the agricultural applications of biochar:
When biochar is added to a compostable mixture and permitted to go through composting, the resulting compost is known as co-composted biochar. Co-composted biochar is a potent enhancer of soil fertility, with long term effects such as improving the nutrient retention and exchange capacity of agricultural soils and improving the resilience and activity of the soil microbiome. Water permeability and retention are improved by the addition of co-composted biochar as well.
An alternative to composting biochar as a means of preparing the biochar for use in soil is to feed it to cows. Since cows chew their cud, the biochar ends up being ground up very finely while being mixed with the grasses and seeds previously eaten by the cow. In the course of passing through the cow’s four stomachs and nearly 100 feet of intestine, the biochar becomes fully loaded with microbes and mucilage, making it immediately ready for use in soil. This practice was pioneered by Doug Pow, an Australian cattle rancher. See his success with this technique of biochar usage here.
Biochar can be used as a nutrient delivery substrate much like how clay balls and rock wool are used in hydroponic farming. Biochar has superior nutrient retention and exchange qualities, making it well suited for use in engineered growing environments such as in hydroponic and aeroponic farming.
Mulch material used as ground cover ends up decomposing over time, contributing to soil organic matter like compost that is made in-situ over a longer period of time compared to being made in a compost pile. When mulch materials are enhanced with biochar, the resulting mulch is a sort of co-composted biochar made in-situ. This may be a good way to gradually introduce biochar into soil where a well managed dedicated composting pile might not be possible.
When added to animal bedding, biochar has two desirable effects:
Biochar is highly porous, and facilitates microbial electron transfers, which is a soil ecosystem service that the soil microbiome benefits from. For this reason, various soil fertility treatments that involve the introduction of selected microbes and fungi can benefit from using biochar as a delivery medium for their selected organisms. For example, biochar inoculated with mycorrhizal fungi can be used to inoculate soil with the fungi
Biochar that is produced using a gasification-derived process is particularly well suited for use as a filtration medium because the reduction reactions that comprise one of the stages of gasification perforates the char at the microscopic scale, vastly increasing its surface area and adsorptivity.
Biochar can be stuffed into filtration socks to serve as a cost-effective first line of defense against pollutants in stormwater washing into broader bodies of water such as rivers, lakes, and the ocean. A broad range of pollutants, ranging from heavy metals to motor oil can be substantially abated by forcing stormwater to percolate through filtration socks stuffed with biochar.
Farm irrigation and rain runoff is notorious for being polluted with dissolved fertilizers. These dissolved fertilizers trigger algae blooms in ponds, lakes, and rivers, which can devastate aquatic ecosystems. Biochar used in drainage ditches, trenches, and holding ponds can cost-effectively abate this type of pollution by binding to and filtering out these pollutants.
As a source of structured carbon, biochar has some intriguing properties that are being explored by researchers in cutting edge material science.
Biochar could be used as an additive to concrete to increase the carbon embodied in the concrete while reducing its weight and its thermal conductivity, which is useful for material use and energy efficiency. Depending on the qualities of the biochar, the addition of small percentages of milled biochar may even increase the strength of the concrete.
Biochar is being explored as a feedstock material for producing graphene using biologically sourced carbon. Graphene has myriad applications, but conventional graphene has is carbon sourced from fossil sources. If biochar proves to be a suitable alternative, it could reduce if not eliminate the dependence on petroleum-sourced carbon for the production of graphene, making graphene products carbon-negative.