The Environmental Impact of Deep Sea Mining
Authors: Amann, Hans , Beiersdorf Helmut 
Published: October 2008

Deep sea mining of polymetallic nodules will have an environmental impact. Since the interdependencies within the ecosystem in the areas in which mining will take place are not fully understood, the quantitative extent to which this ecosystem will be disturbed cannot be predicted yet. The 20 to 30 years before deep sea mining will commence should be used for ecologic studies and a pre-industrial large-scale pilot mining operation in order to assess the potential impact of a full scale mining operation. Such a pilot operation could be organized and performed as an international research and development venture. Methods should be developed which allow a complete monitoring of potentially harmful processes during and after the mining operation. Research should focus on oceanographic conditions, a full assessment of life forms and their interdependencies and the role of nodules in global change, in particular on the carbon dioxide and oxygen budgets in the ocean and the atmosphere. Laws and regulations on the protection of the environment can be improved accordingly. The analysis on the environmental impact of deep sea mining was based on the present state of knowledge. It was carried out by THETIS Technologies GmbH, Hannover, under contract of Bundesanstalt fur Geowissenschaften und Rohstoffe, Hannover, FRG.

Introduction: Polymetallic Nodules and their Natural Environment

Polymetallic nodule deposits on the deep sea floor occur at an average water depth of 4000-6000 m in many parts of the World oceans. They are economically most interesting in the Clarion-Clipperton Zone, the Nodule Belt. In this area between Hawaii and Mexico, about 5 million km2 in size, some 30 billion tons of nodules have been estimated to occur, of which about 5–10 billion tons could eventually be exploited. They show good to very good metal assays: up to 30% manganese, 10% iron, 1.5% nickel, 1.2% copper, 0.2% cobalt and varying amounts of other elements. The potato-shaped nodules cover large parts of the deep sea floor. Abundance ranges between 5 and 25 kg/m2, and occasionally up to 35 kg/m2, but some areas have no nodules at all. These vast and potentially rich ore reserves have attracted individuals, companies and governments to obtain ownership and regulate use. The concept of the "common heritage of mankind" was designed and implemented in the United Nations Convention on the Law of the Sea (1982). Following this convention and a number of reciprocating states agreements, the Pacific Nodule Belt was divided into various concession areas to explore and eventually mine polymetallic nodules.

Test mining during the late seventies and early eighties had demonstrated the basic proof of various concepts of deep sea mining. Further developments during the eighties have improved subsystems, especially the collector, with a view toward better control, efficiency, reliability and, last but not least, protection of the deep sea environment. The latter subject had played only a minor role during the early phases of nodule mining research and development, but has gained increasing attention ever since.