IT cost £41.5million, was built by the same contractor as the guided bus ... and is broken.

The Mechanical Biological Treatment (MBT) plant, which forms part of AmeyCespa's Waterbeach complex, is meant to handles 2,200 tonnes a week of Cambridgeshire's rubbish, but has been out of action since last month.

The plant should save Cambridgeshire County Council, which is responsible for rubbish and recycling after is has been collected by district councils, around £60,000 a week in landfill costs.

But since September 18, when a 105ft steel beam broke, sending a giant wheel spinning out of control, the plant has been closed and the county's waste is being sent to landfill instead.

A company spokesman said the machine broke at the end of a shift when only two staff was on site.

The spokesman said: "The MBT has suffered a mechanical failure within its compost hall equipment and, as a result, waste which would ordinarily have been treated in the MBT is currently being land filled.

"Resolving the MBT suspension is a key priority for AmeyCespa and a thorough investigation has begun.

"In the meantime, we would like to reassure Cambridgeshire residents that their waste collections will continue as normal."

A report to identify the cause of the problem is expected at the end of the month.

AmeyCespa won a Cambridgeshire £731million, 28-year waste processing and recycling contract through a Private Finance Initiative (PFI) project.

The centrepiece of the contract has always been the MPB plant, but the company also provided two new waste transfer stations at Alconbury and March which manage the operations of the nine household waste recycling centres in Cambridgeshire as part of the PFI contract.

Councillor Matthew Shuter, the county council's cabinet member for waste, said: "We are working to keep the costs to an absolute minimum.

"The contract we have is very robust and protects us and the taxpayer."

The MBT was built by BAM Nuttall, which also built the Cambridgeshire guided busway, and is carrying out its own investigation into the problem.