Coal resources: Lignite resources

The NZCRS successfully proved the existence of large tonnages of potentially opencastable lignite, but information was available on mining feasibility and cost, nor the feasibility and cost of converting the huge resources into liquid fuels. The Liquid Fuels Trust Board (LFTB) had a brief to show how to reduce imports of transport fuels, and examined the South Island lignites as an option. Mining feasibility studies were carried out in conjunction with geotechnical, hydrological and environmental investigations.

In-ground lignites resources of almost 12 billion tonnes were established. The LFTB mining studies confirmed the feasibility of mining South Island lignites by bucket wheel excavators at annual production levels up to 20 Mt. All nine lignite deposits of the Eastern Southland and Central Otago lignite resources were judged to be technically mineable, but would only be economic if conducted on a large scale. Over 7 billion tonnes were assessed as being economically recoverable.

The discovery of such huge quantities of potentially opencastable resources had significant ramifications for energy planning at the time, giving some confidence that a large energy backstop to Maui gas was available in the event that the 'Energy Crisis' of the 1970s deteriorated to the extent that the country was deprived of liquid fuels imports. The South Island lignites are an important long-term strategic energy resource for New Zealand.

Key references

Anon. 1982. South Island Lignites Preliminary Mining Assessments Final Report. Report prepared for New Zealand Liquid Fuels Trust Board.

Anon. 1983. New Zealand Coal Resources Survey, Kaitangata Coalfield. Preliminary geotechnical assessment. Unpublished report by Worley Consultants Ltd for Mines Division, Ministry of Energy.

Anon. 1984. Kaitangata Coalfield, New Zealand: Interim mining assessment. Unpublished report by Otto Gold and Applied Geology Associates for Resource Management and Mining, Ministry of Energy.

Anon 1989. Kaitangata sector preliminary mining feasability study. Unpublished report for Ministry of Energy.