Review of Understanding of Continuous Line Bucket System for Deep Seabed Mining
Authors: Masuda Y. , Cruickshank Michael J. 
Published: October 2008

The continuous line bucket (CLB) system has been improved by combining the techniques-of the Turning CLB and Hydrodynamic Separation. The cost of mining nodules from 5,000 m water depth at a rate of 1,000 tons/day is estimated to be $77, which is favorably competitive with the cost of mining by hydraulic systems. Processing of nodules using a sulphuric acid leach is costed at $1 12lt. The value of one ton of processed high grade nodules is estimated to be $319 for a 4 metal operation.. Compared to other mining methods such as suction pump mining and single trawl mining, the CLB is superior in its mechanical simplicity and low power requirement. Its use for the mining of crust and placer deposits also appears feasible

Introduction

Since its conception in 1968 by Yoshio Masuda, the continuous line bucket(CLB) system for deep sea mining, has undergone a number of sea trials. Of prime importance were the tests off Hawaii in 1972 conducted by an international group under the direction of Dr John Mero from the 16,000 ton vessel Kyokuyou Maru No2 (Figures 1 & 2). The second tests were done off Ogasawara Islands in 1975 by a Japanese group which successfully employed the Hydro-dynamic CLB in 4,000 m.(Figures 3,4 & 5). A third series of tests were carried out near Japan in 1987 by Japan Resources Association to successfully test the Turning CLB

Rich deposits of metalliferous nodules have been found on the deep sea- in the Pacific at depths of 5,000 m. in the Clarion- Clipperton Fracture Zone, and the Exclusive Economic Zone of the Cook Islands and in the mid-Indian Ocean. Rich deposits of metalliferous crusts have been found on sea-mounts near Minami-Torishima Island (Japan), Johnston Island (USA), and the Republic of the Marshall Islands.

The nodules and crusts are important for their content of critical metals including cobalt, nickel, copper, and manganese. In recent years political instabilities in African, and other metal producing countries have resulted in shortages and price escalations of these metals, particularly cobalt. Placer deposits of gold, diamonds, tin, titanium and other minerals are common in coastal areas throughout the world and consideration is being given to the use of the Continuous Line Bucket (CLB) system as an option for recovery of these deposits.

The three general methods available for nodules or crust recovery from the deep oceans are hydraulic systems with active or passive miners, autonomous vehicle systems, or mechanical bucket lines such as the continuous line bucket(CLB) and the single trawl miner. In general, the hydraulic systems have beenwell tested, are efficient but expensive, and limited by economies of scale to production operation of at least 1 million t/yr resulting in total investments for mining and processing of over $1 billion; the autonomous vehicles are in a preliminary stage of development, will certainly be expensive, and are not well modeled at this time; the CLB which has been tested at sea under various conditions, is very adaptable, mechanically simple, low cost and not constrained by scale to a large initial production.