Biochar is produced via pyrolysis which means heating organic matter such as wood or waste to a temperature of 350°C to 700°C in the absence of air. Not all biochar’s are equal and not surprisingly reports warning of potential hazards have been raised. Biochar produced from waste wood products or wood chips in manner similar to charcoal if grown organically will not contain the same contaminants and like activated carbon has many environmental applications. With the loss of soil carbon biochar offers a long-term solution for sequestration with reports of biochar from 7000 years ago in the Amazonian region. You can read more about this here.
https://www.nature.com/articles/s41467-020-20184-2: The Power of Biochar?It is hoped that properly made biochar can be used to solve nutrient overload by adsorbing the excess nitrogen and phosphorous which has caused eutrophication of fresh water bodies such as Lough Neagh in Northern Ireland.
Impression of a Eutrophied Lake
Biochar has been shown to reduce runoff into fresh water bodies and can help stabilise soil erosion by improving soil structure and retaining nutrients longer so even non organic farmers would benefit with reduced crop fertilser applications required each year. Again don’t just take my word for it, see the link to the article in Nature below