I’d especially like to ping the good ag-tech folks here, to see if an idea I have is worth pursuing, and to see if anyone might be interested in rising to this challenge. Especially since this issue is prevalent in Latin America, which is well represented in GOSH.
In artisanal mining of gold, typically the soil is excavated with water jets, and the gold particles removed from the washings using liquid mercury. The resultant amalgam is then burned to vaporise the mercury and to recover the gold.
In this process, not only is the toxic mercury released into the environment, the land is also denuded.
One way to tackle both issues is to plant water hyacinth or similar water plant in the ponds that collect residual water. The plant bioaccumulates the mercury, and is then harvested and turned into biochar in a specially designed retort which collects the mercury which is then recovered and sold to the government at a better-than-market price. This funds the process at least partially.
The biochar, now free from mercury, is mixed into the soil to reduce further land erosion. Depending on the retort design, it may be possible to collect the mercury-free producer gas to power the retort itself, or for other purposes.
There are a few things I’m not sure about. I don’t think a large retort (imagine a furnace for making charcoal) exists that can do the job, so may need to be custom designed. Also, I don’t know if non-woody plants make decent biochar. It may come down to selecting the correct species that will both bioaccumulate as well as produce decent char.
I’d be interested in all y’all’s thoughts.