Deep Sea Nodule Mining

 

There are many areas in the deep deep ocean where the bottom is covered with mineral nodules. Some of the minerals in the nodules are ones that we need for the transition away from fossil fuels.  Ways are being developed to mine these minerals. 

 

Sept 2022. - Note that a new type of battery has been developed using no Co or Ni and using a Li, Fe P04, Mn chemistry.  It is reported to be  superior to other Li batteries  in terms of its longevity.  Ocean bottom nodules are rich in Mn, Co, Cu, Ti and Ni and have high concentrations of Fe.  Personally, I would sacrifice a little energy density in my EV battery for an increase in the longevity of the battery.  This latest version of a Li battery can be fully charged and fully discharged with no added fade and if  not in use for long periods of time must be periodically charged.  50% is ideal for storage.

 

Note also that recycling technology for batteries is getting better and better.  This will eventually decrease the need for new mining.  However at present a lot of newly mined minerals are needed.

 

So far, the method of choice seems to be to lower a crawler down to the sea bottom that breaks the nodules into smaller pieces which are then sucked to the surface.  Along with the nodules comes quite a bit of bottom-water* and non-nodule particulates.  The crawlers raise plumes of this particulate material which can settle over unmined areas and smother the organisms there.  It consists of a little mineral matter and of the 'organic snow' that has accumulated over the eons. 

 *Which turns out to be potentially quite important

 

We seem to be conflating* deep sea nodule mining with bottom trawling.  They are quite different.  As is often the case, the devil is in the detail.  How you do something is often more important than the fact that you are doing it.

*Conflate - modern use "confusing one thing for another, whether they be similar or not"

 

 With bottom trawling for fish, clams and prawns, the same area is dragged again and again, never allowing the bottom fauna to recover.  In addition every square centimeter is dragged, eliminating untouched areas  that could re-colonize the dragged areas.

 

 With deep sea mining, the area can only be mined once.  When an area has been mined it will be many, many thousand of years before nodules will be found there in sufficient concentrations to mine again.  (And with our ever increasing output of green house gasses, year by year, we may well not be around then)

But as I said at the outset, the devil is in the detail.  For instance:

 

     We can legislate and enforce, that only a defined percent of the sea bed can be mined.  The nodule rich areas are so vast that this should not be a problem.  Companies that are not complying loose their license to mine.  This way, untouched areas can be left to re-colonize the mined areas.  Possibly even better, we could mine alternate strips.

 

     We must design the crawlers so that the dust they raise on the sea bed is confined and sucked to the surface.  This is to avoid smothering adjacent un-mined areas.  If this material is discharged at the surface it will be dispersed far and wide by currents which go different directions at various depths and will be diluted.  By the time this fine material reaches the bottom, if it ever does#, it should be very little more than the background level of sedimentation.    As an added measure we could  spray the bottom water over the surface of the ocean to start the dispersion*.

# Passive filter feeders in the photic zone will likely take up this source of organic material. The population of such filter feeders will increase in an area where this new source of  material is available.  This would likely form the foundation for a food web.

*Bottom water will be denser than surface water so if released in a solid stream, will likely plunge downward.  Spraying it on the surface will facilitate the mixing with surface water in the photic  zone, allowing time for filter feeders to take up the particulate material and for phytoplankton to utilize dissolved nutrients in the bottom water.  The ocean surface above areas with nodules tend to be ocean deserts with respect to nutrients.  A nodule mining operation will likely  become a biological oasis in this desert.

 

And there may be a couple of benefits on the sea floor:

 

     A climax ecology is somewhat boring.  A certain level of disruption (a tree falls in the jungle) increases biodiversity by allowing pioneer species to  flourish.  Mined-out areas, as long as they are limited in terms of the percent of an area that is mined, are ripe for colonization by pioneer species followed by a sequence, that eventually leads back to a climax ecology.  The question is not whether to mine or not mine but rather what percent to mine and how much to leave.

 

     Bottom water, (as is well known from areas where natural up-welling occurs), powers massive productivity.  A good example is the area off the coast of Peru where up-welling occurs during the la-Nina and El-Nino-neutral years.  It is one of the most productive areas of ocean in the world.   The bottom water, from nodule mining, discharged into the photic zone with its dissolved nutrients and fine organic dust will likely have the same effect as a fecal plume from a whale.  As mentioned, the discharge water could be sprayed across the surface of the ocean to begin the mixing and not have this water plunge back down into the abyss. 

 

As I said at the outset, the devil is in the detail.  Instead of thinking 'bottom trawling' when we hear 'nodule mining' we should look at the detail and the opportunities and ways of benefiting from the nodule mining.  It would likely be  too expensive to pump water and sediment from the deep ocean just to stimulate a plankton bloom in mid ocean deserts and to reap the  benefits that would follow from this.  It is a different story if we can catch a ride on a commercial operation that gets its finance from the sale of nodules to create an oasis in the ocean desert.

I would think that an initial experiment would be to suck up bottom water with the fine particulate material from the abyss and spray it on to the surface of the ocean for  a month or two to see what develops.  This should be done from a surface ship that can maintain its geographical position.  The surface of the ocean is always moving so the surface water will be flowing past a stationary ship.  The bottom material will not be discharged into the same water but into a moving stream.  Samples should then be taken along the discharge stream to see what develops. I bet it will be a succession starting with phytoplankton and small filter feeders and ending with fish and even marine mammals.

Note:  I just learned from this video that the bottom is rich in worms which cycle the snow of organic material which is constantly falling through the water and these worms form the bases of a rich food web.  They would likely be sucked up along with the nutrient rich deep ocean water.  On one hand, it is important that we have a mining system that mines alternate strips, leaving strips untouched.  On the other hand, this rich souce of food, sucked up to the surface will soon be utilized by surface marine life in what is at present a marine desert in terms of available food.  Island countries in the Pacific could find a rich surface fisheries resulting from the mining of these nodules which develops downstream from the surface ship.  It is vital that the 'hurricane' of  dust they raise is confined and sucked to the surface and not allowed to smother the un-mined strips.