There are two primary foam types derived from the polyurethane family; polyester and polyether. Polyurethane was originally synthesised as a substitute for natural rubber in World War II. Polyester polyurethanes are more readily degraded by microbial action than polyether polyurethanes. 

Polyurethane foam can be both thermoplastic and thermosetting. It comes in rigid or flexible form. Exposure to UV light can cause discolouration in both polyester and polyether foams. Another serious drawback is that flexible polyurethane foams are easily ignited.  

Although obtaining polyurethane foam produces a very small amount of CO2 emissions, it is made by combining two types of liquid chemicals both of which come from crude oil distillation. It also poses some serious health risks: vapors and aerosols released during and after mixing the two chemicals up to the time the polyurethane is cured can cause asthma, lung damage, other respiratory and breathing problems, skin and eye irritation, and cancer. Besides, these chemicals are toxic for animals and can cause soil and water pollution.  

Polyurethane foam is not readily biodegradable. It can be recycled. However, no current recycling options can provide a high-quality, reusable, and consistent end product. That is why most of polyurethane foams end up in landfills. Just around a third of polyurethane foams are recycled.  

A more sustainable alternative would be latex foam which is renewable, biodegradable, and free of harmful chemicals.