Soft Ocean Mining
Authors: Amann H. , Oebius H.U. , Gehbauer F. , Schwarz W. , Weber R. 
Published: October 2008

Environmental protection as a basic requirement for all industrial activities is becoming a global principle. This is a particular must in future ocean mining, where a unique chance exists to implement environmentally acceptable methods and controls from the beginning. Bearing this in mind, the German Ministry for Research and Technology is sponsoring a research and development program in industry and universities to develop environmentally acceptable methods. This article gives an account of these new requirements, describes some solutions and outlines future plans. It concentrates on the environmental design and operation of the "self-propelled, hybrid collector", the most crucial new subsystem in future ocean mining.

1. Introduction: needs for environmental protection and research

The deep sea floor, at an average waterdepth of 4000-5000 m, covers about one half of the surface of the earth - the blue planet, as it is seen from space the ocean planet. The deep sea floor is one of the largest global phase boundaries and by this very fact an important interface for many environmental processes of global dimensions. Some examples: The world's climate and CO2 regimes are influenced by processes on and in the deep sea bed. A novel geochemical hypothesis stipulates e.g. that both the CO2 content in the biosphere and warm-cold climate changes are controlled by processes on the deep sea floor in general and by manganese concretions in particular, lit (1). Life on and in the uppermost layers of the deep sea floor is much more diverse than was thought until recently, although very little is known on the interdependence of the ecosystem. The benthic fauna plays an important role in the metabolism of substances and sedimentation from and between the hydrosphere and the geosphere, fig. (1). Care and protection are necessary as the phase boundary "deep sea floor" evidently constitutes a vitally important and delicate ecosystem. Due to the complete absence of light, the cold temperatures and a comparatively scarce food supply, we must assume that deep sea life is not very dynamic. Changes occur slowly. Perturbations and damage can only be overcome slowly.

2. Ecological design principles

Soft ocean mining therefore requires systems which collect deep sea floor minerals, and manganese nodules in particular, in such a way that the character and functions of the phase boundary are protected. This could result in all efforts to eventually mine and utilize deep sea floor minerals being abandoned. This alternative need be adopted only if technology is not able to develop and apply environmentally acceptable mining methods. We strongly predict, however, that ingeniosity and experience will eventually result in safe and low cost ocean mining.

Control is one of the main design guidelines. Uncontrolled dredging, as it was done with the continuous line bucket system, plows deeply and destroys the deep sea floor and is thus more hazardous than active, self propelled and hence controllable systems. The teleguided, self-propelled collector can move on contour lines on the deep sea floor, fig. (2).