When 16-year-old conservationist Jeffery Yu saw an elderly man trudging around a Beijing suburb collecting plastic bottles in the freezing cold, he thought it was bizarre.

As Yu and his fellow classmates were also collecting trash on the roadside, the elderly man motioned them over, directing their attention to the massive pile of plastic bottles he had piled up and told them he could return them for money.

The Singapore-born student and founder of Greenkeepers, a Beijing-based environmental project at International School Beijing (ISB), didn't realize it at the time, but he was witnessing for the first time what he now calls "small step environmentalism".

"If you want to make a big impact - you have to do it step by step, starting at the bottom," Yu told China Daily at the Global Sustainable Leaders Forum (GSLF), where he manned a booth for Greenkeepers.

He was the youngest of 600 budding environmental leaders to take the stage at GLSF, which celebrated the United Nations International Year of Youth by inviting more than 1,200 environmental businessmen, environmental leaders and entrepreneurs to the capital last weekend.

Yu started Greenkeepers in 2008, aged 14, with two older classmates to educate youth on the importance of environmental sustainability. "We're only high school and middle school students, we don't have special knowledge, we don't know how to make solar panels," he says.

"So we started small, planting the seed of knowledge and taking those small steps."

Since starting the organization, Yu and seven fellow students, including his 13-year-old sister Philipa, have worked within their community to spread the conservation message, including traveling throughout Beijing putting posters up in more than 60 restaurant bathrooms encouraging people to use fewer paper towels.

"The group impacts the whole community, influencing us to think about whether or not we recycle," says Lorraine Wick, assistant high school principal at ISB, where the group is based.

"They're holding us all accountable."

Yu was accompanied at the GLSF booth by two of the seven core Greenkeepers members, Philipa and 14-year-old Vivian Xiao.

Xiao says she is involved with Greenkeepers because she thinks environmental degradation is the biggest issue her generation faces.

So far, Xiao's sold mugs to community members to help halt the use of paper cups and raised money to buy trees to plant in the community.

"We're not as big as some of the other groups at the school, but we still get a lot done," Xiao says.

For Yu, the group's youngest members, such as Xiao, are vital to reach out to the lower grades.

He says in the future they hope to deliver their message to even younger students by creating one-day lesson plans about environmentalism, to teach in second and third grade classes.

Yu says though his focus has been on getting people to change their attitude toward the environment, being a part of Greenkeepers has changed him too.

"I grew with the organization. Before I was involved in Greenkeepers I was shy, but now, at conferences, I approach people to tell them about our cause and give speeches in front of big audiences," he says, adding that he hopes to one day become an environmental lawyer.

And as Yu continues to grow, he has high hopes the Greenkeepers will as well. Even though the project is in its infancy, Yu says he is eyeing international university campus locations to expand the small step efforts.

"I hope to take this project with me when I leave high school. Maybe one day we can become a part of the UN," he says.