Is Sawdust Good For Compost? (And Is It Biodegradable?)

Every June 5th, the world marks World Environment Day, a day set aside to encourage worldwide awareness and action to protect the environment. One way of protecting the environment is by planting more trees, replacing the billions that have been felled in search of firewood, timber, and land for grazing or agriculture.

Cutting down trees results in sawdust, a waste product of woodworking. Some communities, however, use the sawdust for other purposes such as for particleboards, serving as mulch, or as fuel. Besides all these uses, can sawdust be used in the composting process? This article discusses the use of sawdust in compost.

Can You Compost Sawdust?

Of course, sawdust is compostable. In fact, it is one of the most preferable additions to compost. Sawdust comes from trees, a plant, which is very much compostable. And yes, any type of sawdust is compostable, meaning it does not matter what kind of wood your sawdust is from.

Sawdust from all types of trees, be they soft or hard, can be used in your compost pile. For composting purposes, sawdust is considered a “brown” composting material. It is therefore used to add carbon to the mix as well as to balance the nitrogen from the “green” composting materials, like greens and food wastes.

Composting sawdust is an excellent way to reclaim some value from what would otherwise be a waste product. Composting sawdust, as well as any other organic material, can be considered a hobby, one aimed at feeding the garden and crops, of course with healthy compost.

When it comes to composting sawdust, you will want to treat it just as you would dry leaves. This means that you have to add the sawdust in an approximately 4:1 ratio of brown to green materials.

Sawdust makes a perfect amendment for your compost pile, as it adds a filler that is somewhat absorptive and will pick up water from rain and juices from the green material, helping along in the composting process.

As already mentioned, sawdust from any type of tree is compostable. However, be very careful and mindful about composting sawdust from chemically treated woods. For these cases, you have to take a few extra steps to ensure that these chemicals work their way out of the compost before you use it in your vegetable garden.

The best way to do this is to douse your compost pile with water a few extra times during the summer. This, along with normal rainfall, should leech any harmful chemicals out of your compost pile and will dilute the chemicals being leeched out to levels that will not harm the surrounding area.

Also avoid using sawdust from walnut wood and similar juglans, as their natural herbicide will kill many common garden plants like tomatoes. While in the composting bin, prepare both the sawdust and other green material to go along with it. They can both be added directly to the compost pile, provided you have the correct ratios.

Ideally, the outermost layer of your compost pile should be completely composed of carbon-rich materials, like sawdust. As such and to achieve this, add the green materials first, and then spread sawdust on top of them.

Also, aerate the compost pile, to provide the aerobic bacteria with a continual supply of oxygen to break down your compost. This is especially important when adding large amounts of sawdust to your compost pile.

Finally, do not forget to adjust the moisture levels of the compost pile. The beneficial microorganisms that aid in decomposition need moisture to proceed, meaning you have to check the moisture content of your compost pile any time you add new materials.

Ideally, a handful of compost should feel like a wrung-out sponge and adding water after introducing sawdust is especially important for two major reasons. First, sawdust is hygroscopic, meaning that it will tend to absorb a high amount of water.

As such, if it is added dry to a compost pile, it will pull moisture away from your existing compost and dry all those materials out. Secondly, sawdust poses the risk of flying away in windy weather, a risk that can be mitigated by dampening the sawdust with water.

Is Sawdust Biodegradable?

Yes, sawdust is biodegradable, recyclable and compostable. Pure wood materials like sawdust and wood shavings are super-high in carbon, and their carbon will absorb all of the plant-feeding nitrogen in your soil in its quest to decompose.

If you are trying to control the decomposition process by allowing the sawdust to decompose inside a composting bin, be sure to add enough nitrogen-rich wastes like green leaves, fresh grass clippings and other kitchen scraps. For the sawdust to fully biodegrade, make sure you rotate the composting bin or tumbler for aeration.

Doing this, encourages bacterial growth and activity inside the composting bin, a process that will aid in the quicker decomposition of sawdust. Also, and most importantly, moisten the mixture. Sawdust is highly absorbent and can absorb all the moisture inside the composting bin pretty quickly.

As such, moisten the mixture regularly, but do not make it overly wet, as this slows down the decomposition process. Also, to be on the safer side, try adding the sawdust in moderation, not only for the moisture levels but also to help control the carbon to nitrogen ratio.

How Long Does it Take to Compost Sawdust?

The duration taken for sawdust to fully decompose is dependent on several factors. However, under all the perfect conditions, sawdust can fully be composted within 6 months.

These conditions assume that, first, you have the proper ratio of carbon to nitrogen in the compost pile. Greens, like grass clippings and kitchen wastes, have to go along with the browns, like sawdust.

Secondly, the assumption is that the proper moisture level in the compost pile is maintained. The pile should not be too wet and neither should it be too dry. You also ought to be turning the compost pile regularly to aerate it. This also encourages bacterial growth and activity inside the composting bin.

There is also the possibility that sawdust can take years to fully decompose. Research by the University of Arkansas Extension, composting sawdust can take several years in some cases, primarily because sawdust is so carbon-rich or, so nitrogen-poor.

According to the research, anything that has a C:N (carbon to nitrogen) ratio that is too high, expects to decay after a long time. In fact, they give the example of sawdust, arguing that it can take years to decay, given that the C:N (carbon to nitrogen) ratio can be as high as 200:1 or even 500:1.

To help speed up the process as well as produce the compost in less time, try adding more greens such as grass clippings or vegetable scraps. Regardless, you have to experiment to find the right combination for your compost pile

Is Sawdust Good For the Soil?

It depends! Pure uncomposted sawdust, by itself, is bad for the soil, primarily because it contains too much carbon and not enough nitrogen. As a result, the carbon in sawdust ties up the nitrogen in the soil as it decomposes, making the nitrogen in the soil unavailable for plants.

The lack of nitrogen in the soil, as a result, can last anywhere from several months to several years, making the soil poor for other crops. If you have already added sawdust to your soil, you can counter the problem by adding finished compost to your soil. The nitrogen in the compost will offset some of the carbon in the sawdust.

In turn, the bacteria in the compost will speed up the process of decomposing the sawdust. This also means that composted sawdust is excellent for the soil, as not only is it a positive addition to the soil and the plants, but it also balances the levels of nitrogen in the soil, unlike uncomposted sawdust.

Is Sawdust Good For Plants?

The answer to this also depends on whether the sawdust is composted or not. Pure uncomposted sawdust is not good for the soil, and neither is it good for plants. It should not be used as fertilizer, because it does not contain a significant amount of nitrogen.

Additionally, it contains insufficient amounts of phosphorous and potassium, nutrients that would be beneficial to the plants. Plants need nitrogen in large amounts for proper growth, the lack of which results in chlorosis or yellow leaves, stunted growth, and other problems in plants.

On the other hand, composted sawdust contains the nitrogen, potassium and phosphorous required by plants for healthy growth and development. Therefore, if you have to use sawdust on your plants, let it be composted first. It, can, however, be used before being composted, in mulching only.

However, apply a thin layer as the sawdust will form a ‘crust’, prone to compaction, and might deny the plant access to nitrogen and other nutrients. If it is composted, it can also be used as mulch without too much worry.

Pure uncomposted sawdust can only work well if used directly or in a mixture of materials as a growing medium for edible mushrooms and fungi. The mushrooms that grow on wood tend to prefer different parts of it.

Most culinary mushrooms are what are called “white rot” fungi, meaning they consume the, usually brown, lignin in the wood and leave the mostly white cellulose. If you are growing mushrooms outdoors, such as in an old tree stump, you can use sawdust plugs to inoculate the new site with spores.

Packed sawdust can also be good for preventing air and water from penetrating in either direction in acid-loving plants like blueberries and rhododendrons. Also, sawdust can help suppress weeds, given that it will deprive these weeds of the necessary water for growth. However, be sure not to kill your plants in the process, all in the name of taming weeds.

Do Worms Eat Sawdust?

Yes, worms eat sawdust. In fact, you can add sawdust to vermicompost, like you would other organic materials. However, this should be done in moderation. Although worms will eat almost anything, dry products like stems or sawdust will take a significantly longer time to be decomposed.

This is because they must work extra hard to break down the sawdust, and the moisture levels of the worm bin continue becoming unbalanced. As such, when adding sawdust to a worm bin, add equal parts food scraps and moistened sawdust.

Adding too much sawdust at once, will sap the moisture from a worm bin and make the contents difficult to break down. Moisten these items before adding them to the bin.

Also, be very careful about the sawdust you are adding to the bin. Feeding treated sawdust to your worms can have harmful effects. As such, source your wood from credible sources, so that the sawdust is free from contamination.


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About Rinkesh

A true environmentalist by heart ❤️. Founded Conserve Energy Future with the sole motto of providing helpful information related to our rapidly depleting environment. Unless you strongly believe in Elon Musk‘s idea of making Mars as another habitable planet, do remember that there really is no 'Planet B' in this whole universe.