Benedict XVI reconfirmed his reputation as the 'green pope' on Wednesday when the Vatican inaugurated its first solar power energy system.
Some 2,400 solar panels have been installed on the roof of the Paul VI auditorium, which is used for papal audiences in the winter and during bad weather the rest of the year.
The official Vatican newspaper, Osservatore Romano, said the panels will generate around 300 megawatt hours of 'clean' energy each year which will go towards providing lighting, heat and air conditioning for the auditorium and several surrounding buildings.
The system will also cut down on the Vatican's annual carbon dioxide emissions by 225,000 kg and save the equivalent of 80 tonnes of oil, the newspaper said.
Built in 1969, the auditorium is one of the Vatican's more modern buildings and can seat around 6,300 people.
The dark solar panels supplied by German company SolarWorld have replaced the old concrete tiles on the auditorium's 5,000-square-metre roof, but are almost invisible from the ground.
Environmentalists have praised Pope Benedict for repeatedly seeking to focus world attention on environmental problems.
Although the Vatican was not asked to sign the Kyoto Protocol, it has pledged to cover 20% of its energy needs with renewable sources by 2020 - roughly in line with the European Union's climate change recommendations.
In a symbolic gesture last year the pontiff accepted an offer from a Hungarian company to plant a 15-hectare forest which would offset all the carbon dioxide emissions produced by the 44-hectare Vatican City in 2007.
