AgCert, the AIM-listed company which trades greenhouse gas credits, lost almost half its value yesterday after disclosing it would not meet certain revenue targets and announcing that its chief executive was departing.

The company's stock closed at £1.20 (€1.78) per share, down almost 48 per cent on its opening price.

Finance director Paul D'Alton said the company had reviewed its performance and found that there would be some delay in completing some of its projects. However, he said the fundamental nature of the business remained sound.

"This is a question of timing. We will deliver on our revenue targets, but there will be a delay in doing so," he said.

AgCert said chief executive Alan Tank would be leaving immediately, with director Bill Haskell standing in for an interim period. The reasons for the departure were not given.

AgCert modifies animal waste, removing the methane using what it calls "biodigestion" technology.

For doing this, AgCert acquires emission reduction credits, known as offsets, which it can sell to major producers of carbon like the ESB.

The company is installing its technology on several farms in Brazil and Mexico. However, it has taken more time and proved more costly to install the technology than the directors originally thought, the company said.

The size of the farms the technology is being used on have also turned out to be smaller.

"The company commenced construction on farms smaller than the standard 1,000 sow equivalent target, leading to higher average capital expenditure cost per offset," said a statement.

Based on these factors, the company issued a profit warning saying that "as result of these factors, there has been a significantly slower rate of inventory accumulation than expected.

"This, coupled with a slower than expected regulatory process, means that revenues for 2005 and 2006 will be significantly below expectations, with consequent implications for net income and cash flow.

"Therefore, the directors believe there will be a delay, of the order of nine to 12 months, in achieving the inventory and sales targets anticipated for 2005 and 2006."

The company is based in Ireland and includes a number of high-profile non-executive directors, including the former EU agriculture commissioner Dr Franz Fischler.