But a company called Terracycle is on a crusade to reduce waste from all the summer picnics, sports events and all-out parties that produce the hundreds of cups, wrappers, straws, bags, bottles, cans and plastic utensils that take a toll on the environment. They call their waste-reducing and collecting efforts brigades, and you can learn how to take part at www.terracycle.net. “One key aspect of not being wasteful is only using what you need,” said Megan Yarnall, senior publicist for the New Jersey-based organization. “Afterward, people can look at what they have and investigate how they can re-use it.”