07/09/2007 at 02:00 PM EDT
Rock star Dave Matthews's infant son, August, is getting an early lesson in environmental protection: He wears reusable cloth diapers rather than the disposable kind.
"We use cloth diapers for our new baby because I think diapers might be the No. 3 piece of garbage [in terms of environmental damage]," Matthews said at a Live Earth press conference on Saturday. "So, if you have a little cloth diaper service nearby, that's good."
August Oliver Matthews is the third child for the musician and his wife, Ashley Harper. He was born at the family's home in Seattle on June 19. August has fraternal twin sisters Stella Busina and Grace Anne, who are 5 years old.
"August Oliver joins his two twin sisters, and the entire family is doing well!" Matthews' rep said in a statement.
The couple had confirmed the pregnancy
to PEOPLE in February.
Asked at the press conference on Saturday whether he had arranged a play date with close friend Julia Roberts
, who recently had her third baby,
Henry, Matthews replied, "We've got outfits that we've exchanged."
Matthews and his band performed on Saturday at Giants Stadium in New Jersey as part of the worldwide Live Earth event, aimed at combating global warming. He spoke to the press about his commitment to the environment – a commitment that seems to have only strengthened since becoming a father.
"It's been things accumulating over the years that sort of make you worry about what kind of world we are leaving for our grandchildren and how we face them," he said. "If you imagine in 50 years how you face your children, if you can't at least say, 'Well, we tried to turn the world around.' It's, I think, an effort we should make, and the evidence is growing."
Reporting by BETHANY LYE