The University of Hawaii has undertaken a project over the course of five years to assess the environmental implications of using the tailings from the land based processing plant of a manganese nodule or manganese crust mining operation in specialty agriculture. As a generalization, the potential for tailings utilization in the area of agriculture is enormous. Many areas of the world have mineral poor or mineral depleted soil. In Hawaii, there are thousands of hectares of land covered with barren lava flows. Manganese tailings are mineral rich; Hawaiian soil is mineral poor. Project work has aimed at characterizing tailings from several potential processing routes and developing a tailings/soil mix which has good growing characteristics. The results of our experiments with 17 different commercial and semi-commercial tropical plant species and manganese tailings/soil mixes suggest that about 20% tailings to soil mix is optimal. At this level, plant growth for most of the 17 test species was stimulated, in one case achieving double growth rates in comparison with the controls.
With growing world population and a rapidly rising global sense of sustainable development and environmental consciousness, there is rising pressure on the mining industry to handle its waste in much superior ways than have been traditional. The marine mining industry is a two billion dollar a year industry currently focused on offshore diamonds, gold, tin, heavy minerals, sand and gravel (Wiltshire, 2001). Manganese nodules were a major mining industry focus in the U.S. in the 1970"s, followed by a large government program focused on manganese crusts in the 1980"s. This work has been taken up by very active deepsea mining groups in Japan, China and Korea. These groups are likely to begin mining in the deepsea within the next several decades (Loudat et ai, 1994; 1995).
