For Lauren Brois, favoring secondhand clothes and stretching out the last drops of shampoo with water is part of her personal mission to reduce waste and protect Mother Earth.

“Throwing away fabrics and clothes into the trash is contributing to pollution,” said Brois, 27, of Bedford in Westchester County. “I don’t buy clothes that I will wear only three times. Clothes must have a life, otherwise they are disposable.”

Her friend, graphic artist Joanna Levinger, 27, of Long Island City, said she does not use plastic bags, and brings her lunch to work instead of eating out using plastic containers, forks and knives.

“It makes me feel better that I am making less trash,” she said. “I donate my clothes. I carry a reusable water bottle and use water fountains.”

Brois said she hopes these and other environmental ideas will become “contagious” as Earth Day approaches on Saturday.

Leading up to Earth Day, the nonprofit Earth Day Initiative on Tuesday will be at Union Square Park with dozens of exhibits, including the latest models in electric and hybrid cars, a recycling collection drive for electronics and clothing, and an effort to enroll more consumers in green-energy programs.

John Oppermann, Earth Day Initiative’s executive director, said the more people sign up, the more motivated energy companies will be to develop wind and solar power.

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“Customers pay a few cents more but you are supplied with clean energy sources,” he said. “Collectively, individual actions can make a difference.”

Both Brois and Levinger said they earmark a portion of their electric bills toward developing wind and solar energy.

“Making a choice for clean energy is a message to big oil companies that people want wind and solar,” Levinger said.

Brois minored in environmental studies at the SUNY New Paltz, where she was the recycling coordinator. Now she works for Energize NY, which assists homeowners and businesses in making their homes and offices energy-efficient.

“I was always interested in preventing waste,” said Brois, who said she saves cardboard paper to make greeting cards and eats leftovers. “My grandparents grew up in the Depression. We were always trying to find a purpose for something instead of just throwing it out.”