Biochar is a relatively new (or really old) organic amendment for soil. The discovery that lead to the production of Biochar for use in horticulture and agriculture was based on the finding of Black Carbon as a major soil component in some unusually productive ancient soils in the Amazon called Terra Preta. Biochar helps to mimic these ancient soils and is created by burning plant material using pyrolysis (burning from the top down with a limited oxygen supply). The resulting material is very different to the products created by burning wood in an open fire, due to the limited oxygen used during this process (even though Biochar can be found naturally occurring in soils where there has been previous forest fires). Pyrolysis produces a charcoal that maintains the plants cell structure and integrity, creating a highly porous, carbon-rich material, that not only acts as a sponge for water and nutrients, but also a catalyst to promote healthy soils. Now, burning something to make a soil amendment sounds bad for the environment, and it can be, but it all depends on the material used to create Biochar, and it has been seen as a way of closing the loop on agriculture production by converting 100% botanical waste, like nut shells, rice husks and other botanical biproducts that would otherwise be sent to landfill (consuming valuable space, and creating gases such as methane) into this beneficial agricultural supplement. The benefits: Biochar has a honeycomb like structure that helps to trap moisture and nutrients in the soil and creates a hospitable environment for microbes. This highly porous form of charcoal also improves soil structure (in both clay and sandy soils) and the water holding capacity of soils and potting mixes. “Biochar is capable of holding 4 times its volume in water,” says Trevor Barrows from Charman Biochar. “It is this ability to hold moisture and trap it in the soil and potting mix which means that you can use much less water, and get much better plant growth.” The honeycomb structure also allows microbes to live and breed in the protective cells, using this as a base while feeding on decomposing material. This increased microbial activity helps to make more nutrients available to the plant, and improve overall soil structure. The honeycomb cells trap nutrients near the plant roots, along with moisture, leading to improved plant growth. According to Dr Mae-Wan Ho, the soil’s depth of Terra Preta in the Amazon can reach 2 metres in some areas, and can regenerate itself at the rate of about 1 cm a year! The addition of Biochar to normal garden soils hopes to replicate this phenomenon. This may or may not be possible, but at worst, botanical waste is being turned in to something that helps to safely return organic residues to our earth while improving water conservation, plant growth and soil health, instead of contributing to landfill and greenhouse gas emissions. HOW TO APPLY BIOCHAR Biochar is easy to apply in new and established garden. * New: incorporate into soils at planting. * Established: spread one litre per square meter and lightly rake before applying mulch. * Potting mix: incorporate into potting mix prior to planting. * Compost heaps: add as an alternative layer in your compost heap.