Six construction firms have been shortlisted for the contract to build Northern Ireland's first ever mechanical biological treatment facilities, in a deal worth up to £500m.

The arc21 recycling scheme, which provides the basis for the development, is led by of 11 of Northern Ireland's councils and aims to provide energy from waste.

Six bidders will now be invited to submit a "detailed and technically advanced" bid for the award.

Shortlisted companies are Covanta Energy Ltd; Greenstar Holdings Ltd / E.On Energy from Waste AG; Indaver / John Laing; SITA Holdings UK Ltd; The Shanks Wheelabrator Consortium; and Veolia ES Aurora Ltd

Expected to last between 25 and 40 years, the contract involves the development of two MBT plants, with a combined capacity of 400,000 tonnes-a-year, and an Energy-from-Waste facility with a capacity of up to 370,000 tonnes-a-year.

Hubert Nicholl, Chairman of arc21's joint committee, said: "We are continuing to make significant progress in our aim to deliver modern waste treatment facilities for the arc 21 region. We were very pleased with the response of the private sector to the original tender. We have invited six consortia to participate in the next stage of the procurement process.

"It is important that progress is made in the delivery of the arc 21 waste management plan in order that we can avoid potentially heavy fines from Europe, but also so that we can contribute to the diversity of sources necessary to satisfy our combined energy needs in the future," he added.

The tender process is expected to last until the middle of next year, with facilities predicted to be in operation by 2014.

(PR/JM)