MANGANESE NODULES
35
Environmental impacts
3.5
As with any mining activity, the main impacts of deep sea miner-
al extraction will involve removal or destruction of material, habi-
tat, and associated fauna. Where mineral extraction is planned to
occur, therefore, the practical management objective will not be
to preserve all the habitat and local animal communities, but to
ensure the impacts of exploitation do not jeopardize such conser-
vation objectives as maintaining biodiversity and ecosystem integ-
rity. Impacts on the social and economic status of human popu-
lations will also need to be considered and will be discussed in
Volume 2 of this series.
When evaluating the potential impacts of sea-floor mineral ex-
traction, there are two general categories to consider: those impacts
associated with normal operations, and those impacts associ-
ated with potential accidental events (which may or may not be
related to natural hazards). Each is dealt with separately below.
Impacts Associated with Normal Operations
As discussed in more detail in the following section on min-
ing manganese nodules, there are four key components to
deep sea-floor mineral extraction:
• disaggregating mineralized material from the sea-floor;
• transporting the material from the sea-floor to the surface;
• dewatering the material; and
• transporting the material to market.
Figure 20. Example of a sea-floor manganese nodule mining system and related sources of potential environmental impact.
Note
that while mineral processing (concentrating) is part of the minerals life cycle, it is not specific to deep sea minerals. Thus, here
we focus on issues related to deep sea mineral extraction and associated processes only. It should also be noted that an offshore,
vessel-based mineral processing facility is not currently considered viable.
Riser pipe
Return pipes
( ltered water)
Production
Support Vessel
Sediment
Subsurface plumes from return water
Sea oor production tool
Seabed pump
Nodule deposit
Barge/bulk
carrier
To concentrator
Ore transfer
Potential impacts from:
Lighting
Noise
Routine discharges (MARPOL)
Similar to shipping and exploration ships
Deposition
Potential impacts from:
Material and habitat removal
Plumes
Light
Noise / vibration
Top layer
Bottom layer
Depth of occurrence:
4 000 - 6 500 metres
Sources: personal communication with Samantha Smith, Nautilus Minerals; GRID-Arendal.
