At-Sea Discharge Of Ocean Mining Process Rejects An Alternative To Land Disposal
Authors: Morgan C.L. , Lovorn F.T. 
Published: October 2008

The prospect of an ocean mining operation discharging processing wastes into the deep North Pacific Ocean raises several important environmental concerns. Mineral processing reject material frequently evokes the image of toxic metals and destroyed eco-systems, and the North Pacific is usually characterized as one of the most pristine, unpolluted bodies of water on the planet. The impact of these first impressions on government, academic, and private environmental interests is formidable, and requires that any potentially damaging aspects of every ocean mining system be thoroughly investigated.

To this end, we use a rigorous approach in our environmental impact program at the Ocean Minerals Company, and carefully evaluate potential impacts of ocean discharge even when most of the evidence suggests that significant impacts do not occur. This worst case" approach is similar to that which has been adopted by most principal investigators in the DOMES program.

During the last several years this in house project has focused upon a number of topics which we feel will compliment those covered by the government programs or which are peculiar to the OMCO system. These include:Baseline measurement of metal values in the oceans.Determination of the settling rates and solid/liquid composition of various mixtures of seawater and reject materials.Comparison of the effects of land-based discharge with the effects of at-sea discharge.Design of a long term environmental monitoring system.

To date, these studies indicate that at sea discharge may cause an insignificant amount of environmental damage and is in many ways preferable to land discharge.

INTRODUCTION

In a recent study conducted by the Army Corps of Engineers1 the subject of open ocean disposal of dredged material is compared to land disposal in general terms. The report discusses two arguments against ocean dumping: The expense of hauling dredged materials to dumping sites in the open ocean is generally prohibitive, andThe environmental impacts of such activities are not easily assessed because of our poor knowledge of deep ocean eco-systems.

In addition, the government report presents two arguments in favor of ocean dumping:During the last two decades, Americans have been progressively using up this nation's coastal lands with urban and agricultural developments. Sites which are suitable for disposal of dredged materials are becoming scarce, while the need for dredging continues to grow.It is well documented that, biologically coastal areas are the most productive on earth, while the deep ocean regions are the least productive.

Thus, disposal of dredge spoils in the deep ocean is potentially far less disruptive for natural eco-systems than coastal or land disposal.

An ocean mining industry will encounter similar problems to those presently facing the Corps of Engineers. Sites with an ocean access will be required for land-based processing plants, since the cost of transporting the deep-sea manganese nodules inland for any great distance may make the venture uneconomic.