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Are Coffee Filters Compostable? | Be Careful What You Compost

Are coffee filters compostable? Is a question that is asked a lot. The short answer is yes, generally speaking, most coffee filters are compostable. The bigger question is whether you should compost them as many contain bleaches and chemicals that you don’t necessarily want leaching into your compost pile.

Coffee filters are a common disposable kitchen item found in most kitchens that enjoy ground coffee as a stable drink for the day. They can me made from various materials and made too look more appealing to the consumer both of which influence compostability.

White coffee filter for compost

The most common coffee filter you will come across are white filters. Unfortunately, these are not naturally white in color and are generally made white through a chemical bleaching process.

This can involve chemicals such as epichlorohydrin which is know to be carcinogenic. Although this i probably more of a issue for drinkers, it is worth noting that this chemical is present is some bleached filters if looking to compost them.

The worst aspect of this is that these filters are bleached entirely for aesthetic reasons. There is no need to bleach the filter in terms of function or taste.

Can you still compost bleached coffee filters?

It is believed that bleached paper goods now are far safer than bleached paper products produced 20-30 years ago. However, it is always safer to use unbleached brown filters if you can find them, since you will be drinking your brewed coffee that has been strained through them.

Filters that are Cone-shaped are often a heat-sealed edge may include a synthetic substance on the edge. As with teabags, it is important to know what these substances are because some sealing agents contain polypropylene plastic. therefore be cautious if you use these filters in a humid environment. If you are worried, you might remove that portion of the waste before composting it instead. Consider using filters like as the Melitta brand, which are certified as biodegradable.

For most households, composting white coffee filters shouldn’t be too much of an issue. Although some chemicals will leech into your composting pile they are going to be small amounts.

If however, you are looking to compost larger quantities of used filters then you may not want to add them to your composting pile as the number of chemicals that leech could be more substantial. This probably only really applies to coffee establishments but if you saved up a few hundred used papers it might not be a good idea.

Are brown paper coffee filters compostable?

Brown coffee filters are just filters that haven’t been through the bleaching process. They are not brown but slightly off-white or lacking color.

Brown coffee filters are compostable and have advantages over white coffee filters. The difference is that brown coffee filters haven’t been chemically bleached. In terms of composting these wont leech chemicals into your composting while decomposing.

How long to breakdown coffee filters in compost?

Used coffee filter - How long to breakdown coffee filters in compost?

How long a coffee filter takes to decompose depend on a number of factors. What it is made of, the number of filters being composted and the composting method.

The majority of coffee filters are made of paper and paper decomposes in around 6 weeks. The actual length of time can vary a little, much depending on the thickness of the paper used in the coffee filter. 

It makes little difference as to whether the filter is white or brown (organic) both will take a similar amount of time to decompose.

Do cotton coffee filters take longer to decompose?

Cotton coffee filters have become common especially in more upmarket segments of the coffee buying public.

The good thing is that cotton is a 100% organic material made from a flax plant and as such will decompose. The length of time it takes though is longer than paper coffee filters. Cotton takes around five to six months to decompose. This, however, shouldn’t put you off as a lot of brown organic materials take around six months or more to decompose.

Do linen coffee filters take longer to decompose?

Linen coffee filters have also become popular. Like cotton, linen is also a 100% organic material and thus will decompose without any issues. Linen’s advantage, in terms of composting over cotton, is that linen can decompose in as little as three to four weeks. 

Speeding up the decomposition of coffee filters

The lengths of time discussed for paper, cotton and linen coffee filters is based on using a traditional cold composting process. These times can be accelerated if you instead employ a hot composting process. 

If using hot composting you can have finished compost in as little as four to five weeks. However, the process does take a little more active involvement in that you need to monitor the temperature of the composting pile and regulars turning every two to three days. The result is finished compost in just a few weeks.

How to compost your coffee filters?

This will come down to your chosen composting method. Coffee filters whether made from paper, cotton or linen are considered brown materials with high carbon content (see below table below).

The level of carbon is important in terms of the construction of your composting pile. Composting works because of the chemical reaction that takes place between the carbon and nitrogen components together with oxygen and moisture.

In regular cold composting where you would need a carbon to nitrogen ratio of around 30-35:1 (C/N). You would assess your brawn (carbon-rich) materials that you are going to use such as leaves weed chips cardboard etc. and add your coffee filters to these layers.

If on the other hand, you are using a hot composting process the carbon to nitrogen ratio changes and you need a higher nitrogen content, around 21-25:1 (C/N). With this process, you would cut the coffee filters for composting into small pieces. Unlike cold composting, where you initially layer the green and brown materials, you mix all the materials together.

If you are putting a coffee filter in the compost bin then again you’d probably want to cut it up into smaller pieces. With a compost bin the composting time will be affected by where you are using an aerobic or anaerobic (without much oxygen) process, the latter increasing the decomposition time.

Carbon to Nitrogen Ratio For Coffee Filter Materials

MaterialC/N Ratio
cotton[1] 45:1
Linen[2]82:1
Paper110:1

Summary | Are Coffee Filters Compostable

Generally speaking coffee filters are compostable. However, it is important to be aware that those that have crimped tops to hold their shapes or have seals could contain plastic in the adhesive agent.

In addition, composting large quantities of bleached coffee filters could also see unwelcome chemicals leech into the composting pile.

In short it is best to compost brown, cotton or linen filters although they have different decomposition rates they make good additions to your brown material.

Notes

[1] V.D. Tsatiris: Composting Cotton Mill Waste

[2] Mahmoud Elsayed: Anaerobic co‑digestion of linen