When a system like the Marshall Hydrothermal Recovery System is proposed, there is always a concern about the environmental consequences that its implementation might produce.
Hydrothermal vents are home to an amazing variety of organisms and animals that are found nowhere else on Earth. Since no sunlight ever penetrates to the depths involved, a wholly different process than the photosynthesis that was formerly believed to be the only life process is involved.
Called chemosynthesis, it's a process where the rich chemistry of the plumes, combined with the high temperatures, creates and sustains life. Extremophile organisms and animals live in temperatures hot enough to boil a lobster, and yet they flourish there. Below are some of the astounding organisms that thrive where no man could survive. The red color on the tubeworms comes from hemoglobin, the same substance we have in our own blood.
When the hydrothermal vents are capped and their flow is directed to the surface, all the organisms dependent on the system will inevitably die since they will be removed from the source that sustains them. There is no way to sugar-coat that fact. For that reason, it is recommended that unique life forms be transplanted to another nearby vent system where they can continue to thrive until nature intervenes.
In considering the environmental impact of the Marshall Hydrothermal Recovery System, it must be recognized that all the hydrothermal vents that now exist will close by natural processes at some point, and every organism supported by them will die. This is nature's way, and human intervention will not change it.
As one vent system closes, a new one will open at a previously frigid and barren point on the sea bed, and a new vent colony will evolve. This was demonstrated by researchers from Rutgers University who had found a vent system that subsequently was naturally closed by volcanic activity. Within nine years, there was an explosion of new life around new vents that opened, including some totally new species. It appears that life spontaneously regenerates around these structures.
By moving the unique species to other vent systems nearby to allow them to continue to thrive until nature finally closes them, the majority of environmental objections can surely be overcome, but it must be acknowledged that nothing mankind has ever done has zero environmental impact. Solar power puts many chemicals used in the manufacture of the panels into the environment, while wind power disrupts birds and migratory patterns. Damming of rivers for hydroelectric has many drawbacks even though it is considered a clean source of power, including flooding of habitats, algae buildup, and a host of other issues.
Our lifestyles and systems require huge amounts of electricity. The only fair way to evaluate the impact of this system is to compare it to what any competing system might produce, since our needs for energy will inexorably continue to increase. To create 20 GW of power would require 5 nuclear plants the size of the largest currently in use, the power station in Palo Verde, Arizona. There is no comparison in environmental impact of closing a few vents and the tons of long-term waste that nuclear would generate.
To create a similar amount of power from coal would
require about 40 plants, huge strip mines to provide the fuel, and
thousands of tons of CO2 would be emitted into the atmosphere. That
doesn't include all the emissions from loading, transporting, and
unloading the thousands of tons consumed by coal-fired plants.
When the renewable nature of even the vent life itself is taken into consideration, and when one realizes that only a tiny percentage of the world's vents are close enough to populated areas to ever even be considered for usage, it seems quite clear that the overall environmental impact would be negligible when compared to any other strategy.