A new Lego tree house kit made with plant-based materials is the latest example of the toy industry’s growing mission to court millennial parents seeking out sustainable toys for their children.

Representatives for Denmark-based Lego say the kit is about much more than building an elaborate tree house and more about building towards the fulfillment of a company goal: to make Lego products entirely sustainable by 2030.

Nearly 200 of the tree house kit's pieces are made of plant-based materials, using Lego’s new polyethylene, which is produced from sustainably sourced sugar cane, making the set Lego's most environmentally friendly to date.

“We are already proud of Lego and its reputation as a durable toy that can be built and rebuilt time and again,” said Tim Brooks, vice president of environmental sustainability. "Now we want to see what we can do about sustainability. We’ve been on this journey for a while.”

“Millennial parents are more aware than previous generations of their impact on the environment,” said Jackie Breyer, editorial director of The Toy Book and The Toy Insider. “They feel the need to teach by example that they can make the world a better place. They are willing to pay more for sustainable quality toys than for cheaper toys that end up in a land fill.”

Retail analysts say sustainability-minded shoppers are a force to be reckoned with. According to data tracking firm Nielsen, environmentally conscious shoppers have grown sustainable product sales by nearly 20 percent since 2014. By 2021, consumers are expected to spend $150 billion on sustainable goods.

And a report published in May by The Toy Association and Prodigyworks notes that millennial parents want the toys and games their children play with to be more eco-friendly, and are actively seeking out biodegradable toys.

Major veteran players in the toy industry, including Hasbro and Mattel, are taking note.

Hasbro, the company behind Marvel action figures and Play-Doh, among other toys, has been working for the past several years on sustainability initiatives. Mattel, the company behind Barbie and Hot Wheels, has established sustainability goals, which include maximizing post-consumer recycled content, where possible.

Rachel Groton, a mom of five from Gloucester, Mass., says she’s among a growing number of moms putting her financial support behind toy companies that strive to be sustainable. When she shops for toys, she said she makes a conscious effort to seek out products that are not made of plastic.

“We try to do what we can by choosing sustainable toys for the kids,” said Groton. “They last longer, in my experiences, and they look better. The quality is much better than a cheap kind of plastic toy that breaks easily.”

Sustainable toys generally command a premium price, but Groton said she believes they are a good investment.

“The food my kids eat is something I’ve always paid attention to,” Groton told NBC News. “I thought, 'If I'm worried about what kids eat, why am I not paying attention to other products like toys?' Our kids are putting toys in their mouths.”

Toy companies are striving to not only make their toys more sustainable, but also their packaging. Lego plans to make all of its packaging sustainable by 2025, and said one of the environmentally friendly components of Lego is that the bricks can be reused for decades.

Many Lego shapes, particularly round shapes, can now be manufactured using sugar cane, Brooks said. But using entirely plant-based materials to mold its legendary bricks, he said, poses unique engineering challenges.

“The bricks have to be able to stick together. They have to be able to be broken apart without using special tools. We want the same shininess of the bricks. It can seem like quite a simple task, but it’s quite an engineering challenge, to make it so that the [sustainable] bricks can be fit together and taken apart without stretching or dissolving or things like that.”

Groton said she and moms in her circle of friends are gratified by the efforts of Lego and other toy manufacturers to pay attention to the values she and other parents hold when it comes to sustainability.

"This is how companies build brand loyalty, when they align with our core values," she said. "I’m more likely to purchase from a brand that has our same values when it comes to sustainability."