LONDON (Reuters) - Heathrow [FGPTOW.UL], Europe's busiest airport, will try to convince a Parliamentary committee on Wednesday that it can still meet environmental standards if it expands.
The airport has been campaigning for years to be allowed to add a third runway because it is operating at full capacity. But it faces opposition from some politicians, local residents and environmental groups.
A government-appointed Airports Commission named Heathrow as the preferred site for a London airport expansion in July, and Prime Minister David Cameron has said he will decide by the end of the year whether a new 23 billion-pound ($35 billion) runway should be built there.
Reassurances that the site can meet environmental standards could help provide political cover for the final decision.
Members of parliament on Britain's Environmental Audit Committee will hear evidence on a bigger Heathrow's carbon emissions, air quality and noise levels, from Heathrow's chief executive, John Holland-Kaye; its sustainability and environment director, Matt Gorman; and Howard Davies, former chairman of the Airports Commission.
The Commission's support for Heathrow was conditional on further restrictions to night flights, introducing a noise levy and a legal commitment on air quality. The conditions were attempt to win over critics, who battled to get a previous expansion plan scrapped five years ago.
The Heathrow executives will outline the steps the airport is taking. Among the steps being taken is a 20 million-pound investment in plug-in electric air conditioners at gates to cool the planes, so they don't need to use engines on stand and emit extra pollution.
"Improved air quality around Heathrow is not negotiable. We've made clear that Heathrow is already playing its part in tackling emissions around the airport - we've reduced them by 16 percent over a five-year period, and that will continue," Gorman said in an interview.
A trial is also underway for aircraft to approach Heathrow's two runways at a steeper angle to help reduce noise, one of the biggest concerns for residents of west London, who live under the flight paths Gorman said.
On the outskirts of Heathrow's vast patchwork site of tarmac and concrete, the airport has also set up a giant reed bed to allow it to purify run-off water polluted with de-icer.
The airport is stepping up plans to use more electric vehicles within the airport, Gorman said. It is also set to benefit from improved rail connections when London's new east to west rail link, Crossrail, opens in 2018. That should reduce emissions from people travelling there by car.
Hidden under one of its terminals, Heathrow has an empty rail station structure, to help boost arrivals at the airport via public transport from their current level of over 40 percent, should additional rail expansion be allowed in future.
However, the campaign group Stop Heathrow Expansion remains opposed to the plans for Heathrow. It says the airport "is the only major UK airport where air pollution levels remains stubbornly above EU legal limits.
According to their website, the campaigners favour expanding at Gatwick, Britain's second-busiest airport. The Commission decided against Gatwick, but the airport says the Commission's environmental analysis on Heathrow was flawed.
Heathrow's largest shareholder is Spanish infrastructure firm Ferrovial. Other partners include Qatar Holding, China Investment Corp and the Government of Singapore Investment Corp.
Reporting by Sarah Young, editing by Larry King