Indonesia’s state tin miner PT Timah Tbk is to increase the supply of tin ore from its offshore mines to 70% to overcome the environmental challenges posed by onshore mining.

Conservation and competition from illegal mining have reduced tin mining in the Bangka-Belitung islands, Indonesia’s main source of tin.

Last year the company’s refined tin production dropped 8% to 45,086t due to reduced production from onshore mines.

It produced 37,701t of tin ore in 2009, nearly 50% of which came from offshore mining.

Timah, the world’s largest integrated tin-miner, said it was planning to increase its number of cutter suction dredges by end of 2010 to boost production from its offshore mines.

The tin industry in Bangka-Belitung, off Sumatra, has seen reduced production in the past four years due to weak prices, a police crackdown on illegal mining and the depletion of easily mined onshore reserves.