It took 15 years to build, cost £4bn, and outraged the green lobby. Welcome to Terminal 5

It may have taken 15 years to complete, been fought every inch of the way by opponents at Britain's longest-running planning inquiry and cost £4.2bn to build, but yesterday, finally, Heathrow Terminal 5 was officially opened by the Queen.

Although it will be another two weeks before passengers, who have endured years of queues and delays at the west London airport, experience the new facilities, its owner, BAA, declared a new beginning for Heathrow.

Environmentalists have long argued that the new terminal building, which will handle 30 million passengers a year, is little more than a "Trojan horse" for further development. There are mounting concerns among local people and green campaigners that the Government is poised to rubber-stamp the building of a third runway – and sixth terminal – vastly increasing the airport's capacity.

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But yesterday the aviation industry, the Government and the Queen were keen to emphasise the sheer scale of the structure – designed by the architect Richard Rogers – and to promote the building as a symbol of renewed national confidence and openness.

Amid heightened security after three alerts at the airport in recent weeks, the Queen described the new terminal as the "21st century gateway to Britain and for us to the rest of the world".

She added: "It provides an encouraging illustration of what can be achieved through working in partnership and it says a good deal about how the essential considerations of passenger comfort, effective security and quality of service can be combined with the ever more important requirement of environmental responsibility."

Her optimistic message was echoed by the BAA chairman, Sir Nigel Rudd, who said: "It is, by any standard a triumph of ambition, commitment and collaboration. It will breathe new life into Heathrow, allowing us to continue our transformation of the rest of the airport and will put Heathrow and BAA back where they belong – at the leading edge of global travel."

Among those introduced to the Queen and the Duke of Edinburgh as they toured the building were Peter Burkhill and John Coward, the pilot and co-pilot of flight BA038 who steered a Boeing 777 plane to safety after it lost power as it came into land from Beijing in January.

Ruth Kelly, the Transport Secretary, was also among the 800 guests who were given a sneak preview of the building's hi-tech check-in facilities and 112 retail concessions including Harrods, Gucci, Prada and Gordon Ramsay's first airport restaurant.

However, while environmentalists conceded yesterday that the new terminal would not in itself add to aviation's mounting contribution to the world's carbon emission total, they fear it heralds further expansion in the industry.

There is also concern that the terminal will handle flights to destinations such as Manchester, Newcastle and Scottish airports – journeys that could easily be made by train. Nick Ferriday of the Aviation Environment Federation said: "Terminal 5 was a Trojan horse for the third runway which the Government appears determined to push through.

"This was vehemently denied by everybody at the inquiry and now it is coming about. T5 is as big as the other terminals put together and you wouldn't want to increase terminal space without the new runway – the figures did not stack up."

But BA, which has exclusive use of the new structure – the largest free-standing building of its kind in the UK – and BAA, insist they have done everything within their power to reduce the impact on the environment. The building was designed to maximise the use of natural light, cutting unnecessary power use, while rainwater from the roof surface area is to be recycled and drinking water pumped from a local borehole.

Excess energy from an on-site combined heat and power unit is to be piped under the building, supplying up to 85 per cent of its heating needs and cutting 11,000 tonnes of carbon emissions per year.