With all the existing and proposed mines in the central Cariboo Chilcotin, mine reclamation is certainly a topic worth paying attention to. A recent 2019 publication, “Biochar for Mine-land Reclamation” by authors A. Lppolito, LiqianqCui, J.M. Novak and Mark G. Johnson, contains 43 technology publications and 1,482 citations. This publication contains the most recent biochar research findings throughout the world. Since biochar has been considered as an emerging panacea for rehabilitating mine waste-affected soils, it is important to explore how it can be used in the future.
One of the first things to note is the cautious language in this scientific report. These disturbed soils are very complex, and there is no simple solution for the wide variety of abandoned sites (estimated to be in the hundreds of thousands globally), with many mines capable of generating acidity, increasing metal solubility and degrading environmental quality.
”Biochar may play a role in alleviating acidity and heavy metal contamination by increasing soil pH and increasing binding sites for chemical reactions to occur. Specifically, biochar can sequester heavy metals through various reactions, including precipitation or bound to organic and inorganic phases. Subsequently, plant growth conditions may be improved and abandoned mine site reclamation may become successful via biochar application.”
It is important to identify the heavy metals of concern (e.g. cadmium, copper, lead and zinc) and the correct biochar application rate for their sequestration.
Furthermore, understanding the potential for biochar-induced chemical reactions to occur, or lack thereof, prior to biochar land application, may save time and money during mine land reclamation. Several examples were presented whereby biochar use did not affect soil heavy metal reductions, suggesting that caution exists in terms of haphazardly using any type of biochar for remediation purposes. Over half a million abandoned mines exist globally. The number of mines varies considerably by country, with Germany at a low of 100, Australia at 50,000, the United States with 500,000 and Canada with 13,000.
My conclusion from this research is that Canada and B.C. in particular are in a good position to make use of the thousands of tons of residual logging material that is burned every year and make biochar to treat existing and future mine wastelands throughout the country and the world. More research is needed in the most efficient ways to make biochar, which is non-polluting, effective and of the right quality for use in mine reclamation and improvement of poor-quality forest and agriculture soils. A lot of the research described above is from small plot trials, which use a conservative amount of biochar, but when it comes to actually applying it over the entire contaminated ground, a lot of good-quality and affordable biochar will be needed. After reading an article about the toxic properties of the large settling ponds in the tar sands of Alberta, I would assume biochar could also be considered for rehabilitation there as well.
Our agriculture and forest industries could be one of the world leaders in the production and use of biochar. Up till now, our residual carbon sources have been considered a fire hazard and a nuisance rather than an asset, and by burning them onsite, we have added more carbon dioxide to the atmosphere and missed the opportunity for carbon sequestration. That approach has to change.
Jim Hilton is a professional agrologist and forester who has lived and worked in the Cariboo-Chilcotin for 40 years. Now retired, he volunteers with community forests organizations.