I hear about the benefits of biochar. What’s the difference between charcoal and biochar? Which is the blackened wood left unburnt in my wood stove?
Question:
I hear about the benefits of biochar. What’s the difference between charcoal and biochar? Which is the blackened wood left unburnt in my wood stove?
Answer:
Thank you for reaching out to the UMaine Cooperative Extension with your question.
Biochar and charcoal are similar, in that they are both produced from organic material combusting at a high temperature without oxygen. However, charcoal is primarily from hardwood products, whereas biochar can be made from agricultural waste, forestry by-products, and other kinds of plant-based mass, and at a higher temperature. The two substances wind up having very different chemical properties, with charcoal working well for fuel and biochar offering a good soil amendment in some situations. In the garden, biochar is often used to improve poor soils–it offers good porosity (which improves soil texture), pH-raising characteristics, and importantly a boost to what is known as Cation Exchange Capacity (CEC), which in soil science terms is a measurement of how well soil binds to nutrients that come in. A low CEC soil would let most nutrients leech through when irrigated, whereas a very high CEC soil might bind so strongly to nutrients that plants can’t access them. In a nutrient-poor soil, biochar can be a fantastic addition, in an already good CEC soil it could theoretically complicate nutrient acquisition.
If you have a nice fertile home garden soil and haven’t had any major issues with it, biochar is unlikely to do very much for you, and isn’t an amendment I recommend in most cases, even if a soil test shows a deficiency. There are usually better options for garden improvement. If you are trying to renovate a very poor soil site, however, it’s a good option for helping condition that soil from the start.
Happy gardening.