Various researchers are suggesting biochar treatment for soil, contaminated with heavy metals. Biochar got the ability to adsorb heavy metals and make it unavailable for plant. But for how long biochar can hold heavy metals?
How someone will come to know that a soil need biochar treatment?
Dr. Nafees
Important practical question indeed.
Using a biochar treatment, is a matter of choice made by the researcher or owner of the land. There is no test to decide biochar is needed or not. For example a soil needs nitrogen. The choice is yours to use uread, or other forms of N fertilizers. The same is true for biochar. It is a soil amendment that have been shown to be effective in soils contaminated with heavy metals, for plant growth. Other sources of organic matter, such as manure and compost have similar benefits. But the choice is yours that in the case of heavy metal contaminated soils to use biochar or other treatments.
best wishes
One of the very interesting properties of biochar is its resistance to degradation in short times. For example manure can be decomposed within 2-3 years in the soil, but biochar may last for 100s of years. In fact, the scientists first found biochar in Terra preta soil of Amazon, which dates back in to ancient history (more than a thousand years ago). These ancient soil are still more fertile than the unamended soils around them.
So, the fact is that biochar will stay in the soil for a long time, and most probably, it is a one time application in our life time. Until next generations decide to add to it or not. But, it is not exactly known that how long the useful properties of biochar (such as heavy metal absorption) can last. Because, over time the free absorption sites in biochar may become saturated by heavy metals and at that time loose its efficiency. But I have not seen any long term experiments or study on the longetivity of biochar efficiency.
So, we could say that depending on the raw feedstock and pyrolysis conditions, the free adsorption sites in biochar produced will be more or less. The more of the free sites, the longer the effectiveness in the soil. Also, the finer the biochar particles applied to the soil, the longer they maintain their usefulness.
Best wishes and good luck.
Nice responses from Farhad....
How biochar treatment to soil will demotivate plants to accumulate heavy metals , unless heavy metal accumulating plants ( bioaccumulators) are tested in such contaminated soils....There is no doubt about the recalcitrance of the biochar , regardless of nature of feedstocks used...
Dr. Nafees
This is closely related to the stability of biochar in soils.Dr. Xinde Cao (Shanghai Jiao Tong University ), he foucs on biochar and its application. Some his papers, such as " The interfacial behavior between biochar and soil minerals and its effect on biochar stability" , may solve your questions.
Just see these papers
Zhang et al. 2013. Environ Sci Pollut. Res DOI 10.1007/s11356-013-1659-0
Liu et al. 2017. Scientific Reports doi:10.1038/s41598-017-09446-0
Patra et al. 2017. Int. J. Res. Biosciences, 6(1), 1-7.
Thank you Desouza Blaise. If possible, kindly share the link of the above papers.
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