Deep Sea Minerals - Vol 2 - Manganese Nodules
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.
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.
When evaluating the potential impacts of sea-floor mineral ex- traction, there are two general categories to consider: those impacts
Ore transfer
Potential impacts from: Lighting Noise Routine discharges (MARPOL) Similar to shipping and exploration ships
Production Support Vessel
Barge/bulk carrier
To concentrator
Return pipes ( ltered water)
Riser pipe
Top layer
Depth of occurrence: 4 000 - 6 500 metres
Potential impacts from: Material and habitat removal Plumes Light Noise / vibration
Subsurface plumes from return water
Seabed pump
Deposition
Sea oor production tool
Nodule deposit
Bottom layer
Sediment
Sources: personal communication with Samantha Smith, Nautilus Minerals; GRID-Arendal.
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.
MANGANESE NODULES 35
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