Lego, as part of its ongoing effort to become a greener toy company, is launching a pilot program to make it easier to donate unwanted Lego bricks.   The toy maker today is unveiling Lego Replay, a program that will provides free shipping labels for donations. Lego will arrange for the bricks to be cleaned, sorted and delivered to classroom and after-school programs for needy kids.   The program, which is being tested in the United States, is in response to comments from consumers who said they wanted an earth-friendly reuse for old bricks, said Tim Brooks, Lego’s vice president of environmental responsibility, in an interview.   “We saw people really wanted to donate their bricks, but one of the things they said was, if we give you our bricks, from the environmental perspective, we don’t want you to grind them up and make outdoor furniture or something else from them,” Brooks said.   Being seen as environmentally responsible is a top priority for toy makers today because millennial parents have made it clear it matters to them. Hasbro, Mattel and Lego, the three largest toy manufacturers, all have announced plans to reduce their packaging and environmental impact.   Hasbro in August said it will phase out all plastic packaging by the end of 2022.   Small toy manufacturers are also undertaking sustainability initiatives.   California-based Green Toys makes toys out of recycled milk jugs and other recycled consumer plastics.   Hong Kong-based Zuru, which makes the water balloon toy, Bunch O Balloons, has a partnership with recycling company TerraCycle to recycle balloon pieces, packaging, and other plastic waste.   There is growing support on the part of parents and toy manufacturers for sustainability measures, Alan Kaufman, Toy Industry Association senior vice president for technical affairs, said. Millennial parents increasingly are showing that environmental concerns influence how they spend their money.   “I think we’re very quickly approaching a tipping point where consumer demand is going to drive some of these initiatives forward,” Kaufman said. Lego has taken on perhaps the most challenging goal of the Big Three toy makers, promising to make all of its products, including the iconic plastic bricks, out of sustainable materials by 2030.   Finding a replacement for the petroleum-based plastic Lego has been using to make bricks won’t be easy. It needs to come up with a sustainable substitute that matches the current formula’s durability and can accommodate the precision molding needed to produce bricks that snap together easily and stay connected.   Lego has begun making some of its accessories from bio-based plastic made from sugar cane, but is still testing solutions for the classic building brick.   Parents, according to Lego research, don’t like seeing unwanted bricks go unused.   Old bricks, Brooks said, typically get passed down to children and grandchildren or donated to neighborhood groups. But Lego still gets good number of letters and emails from people asking how they can recycle or donate unneeded bricks, he said.   The Replay program ties into the “sharing economy” trend favored by millennials. A report by the Toy Industry Association in May recommended that toy companies sponsor toy exchanges to appeal to millennial parents, in addition to making the toys out of more sustainable materials.   Under the program, people who want to donate bricks can print out a free shipping label available on Lego.com. or through a link on the website of its recycling partner, Give Back Box. The bricks will be sent to Lego’s partner, Give Back Box, a charity that handles similar donation programs, where they will be cleaned, inspected, sorted and repackaged for delivery to Teach for America classrooms around the country, and to the Boys & Girls Clubs of Boston.   Lego worked on the Replay pilot for three years before launching it, Brooks said, because the company wanted to make sure it had the right partners and controls in place. “We wanted to maintain the quality and safety that Lego is known for even in a used product,” he said.   Teach for America classrooms and the Boys & Girls Clubs of Boston will receive their first sets of bricks starting next month. The pilot program will run through spring of next year, and depending on the response, may be expanded to other countries.   The bricks will be a welcome addition to the low-income schools where Teach for America recruits work, said Lida Jennings, executive director of Teach for America, Los Angeles.   In Los Angeles, Teach for America is in the highest-need schools, where family incomes are well below the poverty level, and the children don’t have access to Legos, either at home or in the classroom.   Jennings said the bricks will be used for everything from simple addition and subtraction and counting exercises in math classes to engineering and physics concepts such as “how big does the base have to be to support the height of the tower,” or robotics.   “They’re going to be used in many, many ways,” she said. “And Lego bricks transcend generations so teachers are going to know what they are and how to use them, just like kids are going to be able to automatically know how to jump in and understand them,” Jennings said.   Brooks said it is hard to predict what the response will be to the Replay pilot. The company has done projections and believes it is prepared to to handle as many bricks as are donated.   “We hope it’s a good steady stream,” he said. “There are already lots of different options for people to donate or sell or pass on their bricks to others already. This is just another option.”