Every pair of shoes people wear comes with a hidden environmental cost, from overconsumption, to the amount of annual shoe waste, to the microplastics woven in the cloth. All raise environmental concerns.

According to Unsustainable Magazine, people throw away over 300 million pairs of shoes every year, and about 95% of this waste ends up in landfills. Donating to or buying from places such as Goodwill or the Salvation Army is an option, but there can be some drawbacks. These can include developing foot issues from wearing worn-out footwear, and the spread of fungi and foot infections.

Beyond the waste of used shoes, physical footsteps also have a negative impact on the environment. The term “trampling,” meaning the compaction and abrasion caused by feet and shoes, is a key cause of loss of species in some environments. According the website Forests, a peer-reviewed scientific journal, a group of Chinese scientists examined the effect of human foot traffic in an urban forest park in Nanjing, China. They found that the pressure caused by humans not walking on marked paths had negative impacts on soil nutrition, microorganisms, and environment structure.

Scientists and material innovators have been searching for a solution to these issues since it’s not realistic to expect humans to stop walking. The OXMAN Lab has developed a new way of walking: on fully biodegradable footwear. These shoes absorb naturally into the earth, and leave no human footprint, meaning they don’t contribute to environmental harm. According to Positive News, these shoes are made completely with polyhydroxyalkanoates (PHAs), organic materials created with bacteria, which are then 3D printed to create the shoes.

These organically-made shoes are biologically recyclable and biodegradable, meaning they leave no microplastics behind. Scientists believe this innovation could change the trajectory of future environmental development.

Though, at this point, biodegradeable footwear is not an option for most Americans. So what can you do if you want to reduce shoe waste?

According to Soles4Souls, shoes that are thrown away often end up in landfills, where they can take 30 to 40 years to decompose. As a result, they offer these tips when choosing and recycling shoes:

• Choose athletic shoes and sneakers when possible, as they are easier to recycle than boots made of leather.

• Consider purchasing shoes made of materials which are easier to recycle, such as bamboo, recycled plastic, cotton, hemp, and cork.

• Purchase from retailers which have “take-back” programs which will recycle shoes for you.

For more information on how to recycle shoes, visit the Soles4Souls website.