Tuesday, June 19, 2012

Mine Remediation Protocol

I have begun Jared Diamond’s; Book on why societies collapse and am into his discussion regarding the trials and tribulations of the mining industry and the problems regarding cleaning up the damage often caused.  I wish to address this particular issue.

As already discussed at length in this blog we have a protocol that creates new soils, retains soluble chemicals within the soil horizon and outright eliminates the entire need for chemical fertilizers.  This is the inevitable future of agriculture however long it may take, as application needs years and possibly decades. Yet agriculture happens to work that way and decades is a practical time line.  From my perspective, agriculture is a solved problem (Thank the lord) that merely needs years of knowledge sharing to implement.  This is well begun and will progress apace below the radar for years to come.  At best, it could be sped up.

My argument is that the core technology can be used to properly sequester mine waste and tailings in an economic manner.

A typical mine is engineered much as follows:

1                    1,000,000 tons of mill feed 
2                    2 to 5,000,000 tons of mine waste to be placed on a waste pile.

The waste pile is engineered in place to normally allow escaping leachate to follow normal drainage down into the impoundment of the mill tailings pond.  This is significant because freshly broken rock will slowly weather and contained minerals, although quite obviously quite uneconomic to mill, will be released as soluble acids and salt and enter the underlying drainage.  This is the sensible approach and the only viable one that allows a waste tip to be ignored later unless there is a good economic reason to revisit it.

In the meantime the persistent leachate will escape into the impoundment pond that is already handling the mill effluent.  This is where we really have a problem.  Again fresh mineral collects in the pond along with those million tons of finely ground mill waste also including some more mineral finely divided.

These ponds are typically lined and clay is added to absorb the mineral as much as possible.  Ruptures and floods are no ones friend in this situation and a release sends a strong charge of soluble mineral downstream along with a charge of suspended talc like fines.  Clay does not help a lot either.

There are some methods available to partially neutralize the nasty chemicals but the result is typically partial and the most important one will delightfully but safely turn the river purple.

What I suspect will work is to produce coarse biochar from sawdust which should be readily available in sufficient amounts to produce the tonnages desired.  I would then blend the mill tailings and the biochar on perhaps a ten to one ratio of tailings to biochar along with a little cement to coagulate the mix and allow it all to set up in the tailings pond.  The carbon will progressively absorb any free ions and any leachate arriving from upstream will percolate into the now solid but porous bed and also be absorbed.  It should be possible to capture any and all free ions forever.  It will not prevent minor release from floods but that by its very nature would be hugely diluted.

After a few years of all this we should have some pretty happy trees growing through the former tailings pond.

I also suspect that this method needs to be tested on the Tar Sand tailings ponds also although the chemistry is quite a lot different and I am not initially optimistic here but we could be pleasantly surprised because we do not have the fines here.

All mine solutions will still face some issues but this approach promises to reduce them to minor issues such as unidentified fault drainage and the like.  It is geology after all.

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