The Economic Value of Manganese Tailings to Marine Mining Development
Authors: Wiltshire John C. , Loudat Thomas A. 
Published: October 2008

Several Asian mining groups are interested in mining marine manganese deposits in the next century. Tailings disposal will be a major environmental issue for them. Several large landbased manganese mines would also like to improve tailings disposal practices. Work at the University of Hawaii hasshown that manganese tailings have useful properties and can be used in a variety of applications. These include: plastic andresin fillers, solid surface applications, rubber and asphalt fillers, fillers for coatings and as a coloring agent for concrete and brick. In addition, the manganese proved a useful soil additivefor agriculture and a ceramic component for glazes and glasses and possibly a weighting agent in drilling mud. These results suggest that sizable portions of the tailings could potentially be sold rather than disposed. Not only would thismake marine mining more environmentally attractive it would also makes it more economic. Four models were run of theeconomic differences imparted by tailings sales. When valued as an inert filler with no useful properties, selling portions of the tailings increased the internal rate of return of a mining operation from 23% to 28%. If sold as a more valuable commodity the profit increase would be even more dramatic. This economic study indicates that manganese should either be fully extracted in a marine mining operation or at least the fine grained tailings used in non-metallurgical applications rather than disposed.

Introduction

Traditionally mine tailings have been considered an economic Liability and a potential subject for environmental litigation. Mining of manganese nodules in the Pacific is currently planned by at least t':"o government mining groups 1,2. Mining of manganese crusts IS under active contemplation in the 200 mile exclusive economic zone around Johnston Island in the mid Pacific by several multinational corporations. These and other new seabed mining ventures will face opposition unless tailings can be well managed. The estimated expense of tailings disposal for these operations can be up to $10 million/ year. Even land based manganese producers typically pay more than $1 million per year to maintain tailings dams. The Chinese Ocean Minerals Research and Development Association (COMRA) has stated an intention to mine manganese nodules and possibly manganese crusts. In June 1997, they signed a cooperative agreement with the State of Hawaii (which was incorporated in the US-China National Scienceand Technology Agreement) for the joint investigation of issues related to this industry, including tailings utilization. Korean groups have also announced plans to continue their major mining development work with a view to mine nodulesaround the years 2010. BHP, an international mining giant, have been mining a manganese crust deposit on an island, uplifted from the seafloor and are interested in future deposits and management of the crust tailings.

Ongoing research at the University of Hawaii, working With manganese tailings is demonstrating that these tailings can m fact be used in a range of secondary industries. In particular, the project has had success looking at fine grained manganese tailings in the filler industries.