OK, so suppose that we were to do as I suggested and bring ocean water inland to mitigate sea level rises, then evaporating it to generate power and create fresh water. This would serve the purpose of cooling the continental interior, bringing water inland to substitute for the degradation of the natural conveyor, and generate power without burning carbon.
We understand the technology, and it is not without its problems
Laurene Veale, MIT Technology Review:
[The basic issue is that there is very little freshwater]
The two main desalination processes are Multistage Flash (MSF) distillation and Reverse Osmosis (RO)
A more radical solution [than reverse osmosis] is solar-powered desalination, now being deployed in Tunisia, Abu Dhabi, Kuwait and Saudi Arabia with Jordan and Morocco announcing their intention to desalinate water with renewable energy.
However solar or wind power will not resolve a major environmental challenge posed by desalination: brine, the highly saline slush created from the desalination process. For every litre of freshwater, a litre of brine is produced. “When desalination is done inland, far from the coastline, dealing with the brine is a problem. You cannot dump it in the sea, and the only solution it to dump in the ground, but this contributes to increasing the salinity of the groundwater, which is destructive for the environment” explains Arafat.
Discharging the brine back into the sea is harshly criticised by marine biologists, who deplore its destructive impact on the marine environment. The high salinity and the high temperature of the brine can destroy marine flora and micro-organisms which in turn affects the entire marine food chain in the area.
One of the solutions proposed by Arafat is to crystallise the brine to make salt…
Now, this isn’t the last word.
1. Reverse osmosis also can cause damage to marine systems. One solution is to distribute the high-salinity effluent over a large area.
2. It’s not impossible, as the article implies for desalination to be done far from the sea. There’s just an associated energy cost.
3. The problem for marine systems is not just with output. It’s with input as well. One doesn’t want to sweep up plants and small animals with the intake feed. And then there’s the point that effluent can alter the temperature of the effluent and damage marine systems that way.
4. The problem of contaminating groundwater is real, and has to be dealt with.
But these are not impossibilities. They are simply technical problems to be overcome. For example, one could consider using the high brine effluent to grow brine tolerant plants. Here’s an ARAMCO document by Luis Lujan Rodriguez on desalination:
Desalination discharges have been shown to represent detectable environmental effects in seagrass habitats, phytoplankton, invertebrate and fish communities in areas near the discharge sites. Some species show that an increase in salinity of only 1-2 parts per thousand (ppt) can affect highly sensitive seagrasses. Salinities of 40-45 ppt increase the mortality in exposed plants, and epifaunal mysids and echinoderms. Other marine animal species may also be affected as some species of worms have been observed to become more dominant whereas others decreased in diversity up to a distance of 400 m from a discharge point. Reductions in the abundance of plankton, sessile invertebrates, and echinoderms can also be related to the discharge of brines especially when the copper concentration was high.
In addition to diluting the salt with other wastewater, this document suggests extracting valuable (e.g. precious metal) and toxic (e.g. copper)salts from the effluent, and converting the salt using CO2 into sodium bicarbonate (which additionally sequesters carbon).
But this is far from exhaustive. One could, for example, use brine tolerant plankton (or other aquatic life) to concentrate the salt, then release the organisms back into the environment. One simple example: grow algae or seaweed, then use them as human or animal food. In the case of plankton, one could release them into the sea to help restore the damage we have already caused to the ocean.
The point is that we haven’t even really thought about the issue. When we do, we will think of solutions. But our immediate problem is that global warming will radically damage our productive industrial plant, trigger conflicts, and reduce agricultural productivity due to interior continental warming. We do need to cut carbon emissions. But that’s not going to happen overnight. We need to use all our brainpower as a species.
Added, from Phoenix Woman’s link (Tina Casey, Clean Technica), on the recovery of valuable minerals from saline water:
Here’s how it works on the agricultural drainage water of Central Valley, which is typically discarded as an unsuable byproduct of irrigation. The salinity level for drainage water in that region can range higher than the content of seawater.
Phase 2 is where the rubber will hit the road in terms of resource recovery. Due for completion this fall, phase 2 is expected to demonstrate that resource recovery can from the brine can be managed with minimal environmental impacts, if any.
The recoverable products include gypsum and calcium compounds that are widely used in the building industry for drywall, plaster, and cement.
Also present in the brine from this particular drainage area are magnesium salts, which are used in the medical industry, selenium (a health supplement), nitrates (fertilizer), and boron, best known for its use in bleach and pyrotechnics among many other uses.
Boron is also coming into its own in high-efficiency electronics and cutting edge solar technology, and for the record, selenium is also used in electronics as well as glass making, so altogether the region could be looking at a new high-value, job-creating industry in tandem with its agriculture base.