Sky-high commodities prices are set to come down to earth, says a new report by trade credit insurance company Atradius Group.

Although low supply and growing demand from emerging economies could keep prices high for such materials as tin and nickel, the report says aluminum, lead, zinc and other commodities are likely to become less expensive in 2009.

“Though the run-up in commodities prices has been sharp and severe, demand has traditionally been cyclical depending on demand for the products in which they are found,” said Isidoro Unda, CEO of Atradius, in a statement.

Such factors as a looming U.S. recession, slowing growth in Europe, falling oil prices and tightening credit conditions are likely to produce some relief in prices of some raw materials, he said.

Unda warned, though, that lower prices could take time: “These changes, however, are generally slow to take hold.”

But the report notes other predictions that contrast this view.

“We are in a bull market for all types of commodities, and this can go on for another 10–15 years,” said commodities expert and investor James Rogers in the report. “There has been a lack of investment in productive capacity for many years, and now the world is starting to pay for that.”

Still, the Industrial Raw Materials index, published by the Economist Intelligence Unit, predicts that after strong growth in early 2008, the markets for many industrial raw materials will cool in the second half of the year. It predicts average price growth of just 1.1% for 2008 as a whole, while average prices for base metals are expected to fall by 1.5%. In 2009, the EIU expects a downward tend in overall IRM prices.