Sustainable Insole Materials: Bio-Based vs. Recycled Foams

What Footwear Designers Need to Know

Adding sustainability into your footwear can be done in different ways – maybe you want an outsole made with eco-friendly rubber, an upper made from recycled materials, or a manufacturing process that cuts energy use and CO2 emissions. Another way to add sustainability into your footwear is by considering insoles made from sustainable materials. 

Bio-based foams and recycled foams are making insoles more eco-friendly than in the past, and each option has different benefits and features, so you can decide what makes the most sense for your specific line of footwear. The most important thing to remember is that not all “sustainable” foams are created equal, and you should consider the source, certifications, and performance of your bio-based or recycled foam selection before deciding if it fits into your company’s sustainability goals.

Understanding Bio-Based Foams: What Are They?

Bio-based foams are made by replacing a percentage of traditional petroleum-derived ingredients with renewable, plant-based compounds. For example, INSITE’s bio-based open cell foams incorporate natural compounds derived from sustainable sources such as US-grown dent corn and EU beet sugar.

Bio-based foams have numerous benefits that not only make them an ideal material for insoles, but help support your company’s brand values and consumer priorities.

• Help Lower Carbon Footprints: Substituting renewable inputs reduces reliance on fossil fuels.
• Leverage Renewable Resources: Unlike finite fossil fuels, bio-based foams are made from abundant, fast-growing feedstocks like industrial field corn. 
• Carry Sustainability Certifications: Many bio-based foams qualify for third-party standards that validate measurable sustainability claims and resonate with eco-conscious consumers.
• Reduce the Waste Stream: Some bio-based foams can be recycled or are able to biodegrade, offering a more sustainable end-of-life solution than other non-biodegradable materials that can take hundreds or even thousands of years to decompose. 

Further, many bio-based foams offer enhanced comfort and performance due to the higher tensile strength, tear strength, and elongation of plant-based polyurethane material. These features contribute to a more responsive feel, providing excellent cushioning, shock absorption, and resilience.

And because bio-based foams can be more lightweight and durable than traditional foam formulations, they’re more prone to maintain their cushioning properties over time without breaking down or compressing. 

Understanding Recycled Foams: What Are They?

Recycled foams are made by incorporating post-industrial or post-consumer waste (such as leftover foam scrap or rubber) back into the material mix. Many brands are incorporating recycled materials into their products, and insole foam is another excellent way to capitalize on recycled materials and increase sustainability benefits.

Recycled insole foams offer several key benefits that, like bio-based foams, support a company’s sustainability goals and consumer demands for greater eco-consciousness in product design and development. 

• Divert Waste from Landfills: The nature of recycling keeps waste out of landfills and reuses it, which is important when it comes to insoles as traditional foams can take hundreds or thousands of years to break down in a landfill. Recycled foams help decrease landfill waste over time and reduce toxic emissions and microplastic pollutants created as foam materials decompose.
• Lower the Demand for Raw Materials: Increased use of foams made from recycled materials helps offset the demand for raw virgin petroleum, the production of which has been highly criticized for its negative environmental and public health impacts from pollutants released during oil extraction, refining, transport, and combustion.
• Carry Sustainability Certifications: Many recycled foams qualify for Global Recycled Standard (GRS) certification, which is an important way to validate the benefit and impact of your footwear insoles on the environment.

Recycling offers a clear environmental story and carries some compelling performance benefits as well.

High-quality recycled foam can offer similar performance as conventional insoles, with comparable cushioning and rebound over time. Plus, recycled foams can generally maintain the benefits of an open-cell foam structure like greater moisture management and breathability for a drier wear experience. 

Coupled with lightweight comfort – another benefit of the open-cell structure – recycled insole foam can enhance overall comfort while providing exceptional cushioning and support. 

However, there is a caveat to all these great benefits. Higher percentages of recycled content can sometimes compromise consistency, feel, and durability, so there needs to be a balance of recycled content and other foam material to ensure the best combination of comfort, performance, and support.

Performance: Where Bio-Based Foam Stands Apart

Because footwear in general contributes to the waste stream, offering excellent comfort, performance, and support ultimately keeps shoes on feet and out of landfills (at least for a little while).  

Here, bio-based foams have a distinct advantage when it comes to enhancing the wearer’s experience. Let’s recap the primary performance advantages of bio-based foams:

Recycled foams, while sustainable in concept, can introduce variability. Designers may find themselves balancing eco-claims against the consumer experience.

At INSITE, we use responsibly-sourced plant-based materials in many of our PU foams, supporting regenerative farming practices and helping reduce greenhouse gas and non-renewable energy through the use of Susterra® Bio-PDO™ to replace a percentage of petroleum-based BDO. 

Some of our other sustainable practices include using solution-dyed textiles and poured PU, but you can learn more about all of it on our website.

Carbon Impact and Consumer Priorities

Shoe brands are constantly working to demonstrate measurable progress toward lowering carbon emissions beyond just recycled content percentages.

Bio-based foams directly reduce carbon footprint by replacing petroleum with renewable alternatives.

Recycled foams reduce waste but often still rely heavily on petroleum inputs for core performance; although, brands are slowly working toward using greater percentages of recycled materials without impacting performance. 

For brands looking to tell a strong carbon story, bio-based formulations provide clearer, science-backed impact reductions.

How Do You Know Whether to Use Bio-Based or Recycled Foams?

Bio-based and recycled materials each play specific roles in footwear design. Bio-based foams are ideal for performance categories, such as running, training, and hiking, and are a great choice for brands focused on measurable carbon reduction. When cushioning, energy return, and durability are top priorities, bio-based foams are an excellent choice. 

Recycled foams are often used in lifestyle or price-sensitive footwear categories where sustainability messaging is important but peak performance is not as critical. 

INSITE’s bio-based open cell foams strike the balance footwear brands are seeking: sustainable sourcing plus enhanced performance. By engineering renewable compounds directly into the foam structure, we help brands lower their carbon footprint while delivering the comfort and support consumers expect — right out of the box.

For footwear designers, that means you don’t have to choose between sustainability and performance. You can deliver both. Sustainable materials are reshaping footwear, but the right choice depends on your category, your consumer preferences, and performance goals. Recycled foams help reduce waste, but bio-based foams—like those offered by INSITE—are driving the next evolution: lowering carbon impact while raising the bar on comfort and durability.