Are sponges biodegradable? Can they be composted?

  • Date: May 13, 2022

Sponges are one of the most popular cleaning items – from the kitchen countertops to our cars. Although not quite as bad as single-use products, they do need changed fairly regularly. This leads to a lot of waste which, unfortunately, often ends up in landfill. Rather than throw them in the trash, what are the other alternatives? Are sponges biodegradable and can they be composted?

What are sponges made of?

When determining if an item is biodegradable or not, it is useful to know what it is made from. Sponges come in a few different forms. The main types are: natural (such as sea sponges and loofah/luffas), cellulose and plastic-based (such as polyurethane). Each bring their own advantages, price point and eco-friendly credentials.

So, are sponges biodegradable?

Biodegradable items can be broken down naturally by micro-organisms such as bacteria. Out of the three main types of sponge, the cellulose (made from wood pulp) and natural varieties can biodegrade. They can, essentially, return to nature. The process can take about a year. Polyurethane sponges, like other plastics, will not biodegrade – they will simply break into smaller pieces over time, causing havoc in the environment.

As with all biodegradable items, optimal conditions are vital. Landfill is not just a massive compost pile like people sometimes imagine. Poor airflow and moisture levels make the breakdown process significantly slower than breakdown figures quoted. Keep this in mind when you throw any biodegradable item in the trash – it may still be around for a much longer time than you’d expect!

Are sponges compostable?

Composting is growing in popularity. It is a great way to dispose of organic waste whilst creating some free, nutrient-rich fertilizer for your garden. What’s not to like? Many people think that any biodegradable item can be composted – this is not the case, unfortunately. The terms ‘biodegradable’ and ‘compostable’ are not the same. However, if a biodegradable item is not with laden chemicals that could contaminate the final product it is, generally, suitable. Cellulose and natural sponges fit the bill. Unsurprisingly, polyurethane sponges can not be composted – they would remain in the pile indefinitely.

As you might know – composting materials fall into two categories. ‘Green’ materials refer to items that are rich in nitrogen such as coffee grounds. ‘Browns’ are rich in carbon and include items such as cardboard.  Sponges fall into the carbon-rich/’browns’ category. It is important to ensure you have an adequate mixture of both ‘browns’ and ‘greens’ in your compost pile. Too much carbon-rich material can mean a dry pile, too many ‘greens’ can result in a sludgy, smelly mess! As with all composting, a bit of trial-and-error is required, but you won’t go far wrong with a 1:1 ratio. Monitor it and adjust as you go. 

If you take the correct steps to make sure your compost pile is healthy, you should find composting sponge a really simple process. However, if you are new to composting, we have answered some of the most common newbie questions here to help you on your way.

Things to consider when composting sponges…

As far as composting goes, sponges are on the easier end of the scale. Like other items, it helps if they are cut into small pieces before being added. Although not absolutely necessary, it will speed up the process. Smaller pieces can also be mixed throughout the pile spreading the benefit of its moisture wicking properties. You should also remove any plastic components of the sponge before throwing it in the compost. The rough green layer on some kitchen sponges is usually made from nylon or polyester – since these are both plastic-based, they should not be added.

You should also err on the side of caution if you have been using particularly harsh cleaning chemicals on your sponge. Chemicals can contaminate the compost pile and, ultimately, your garden when used as fertilizer. Some gardeners prefer to use the fertilizer on non-edible plants in this case. As ever, it’s your call – don’t ever add anything you feel uncomfortable with, sponge-related or otherwise.

The bottom line

Composting your used sponges is a great way to reduce your household waste, especially since we go through so many of the things! Out of the main types of sponge available, cellulose and natural sponges (such as sea sponges) are the only types that are biodegradable and suitable for compost. As far as composting goes, sponges are fairly straightforward – just cut them up and mix them in. Voila.