You may think that once you’ve finished cooking on your charcoal grill it’s time to toss the ashes and partly burnt charcoal in the trash.
But what if I told you that this seemingly spent piece of carbon could have another life? That’s right, I’m talking about composting used charcoal.
While it may seem like an unlikely candidate for compost, charcoal actually may have something to offer even after its burning demise.
So can used charcoal be composted? For those that don’t feel like reading the whole article, here’s a quick answer:
Charcoal can go in a compost bin in moderate amounts as long as it doesn’t contain any chemical additives. Lump charcoal is generally considered safe to compost. Most charcoal briquettes should not be composted as they often contain chemicals that can leach into the soil and may be harmful to both your compost and the plants you eventually use the compost on.
Now that we got that quick answer out of the way, let’s take a closer look at what charcoal is and how it can be used in composting.
Table of Contents
- What Is Charcoal?
- Why Is Composting Beneficial?
- Lump Charcoal Is Usually Safe To Compost
- Avoid Composting Charcoal Briquettes
- Charcoal As a Fertilizer
- Final Thoughts
What Is Charcoal?
Charcoal is a common grilling fuel, but it’s also a bit of a mystery for some people. What exactly is it, and where does it come from? Lump charcoal is made from wood that has been burned in a low-oxygen environment. This process removes water and other volatile compounds from the wood, leaving behind a lightweight, carbon-rich material.
There are two main types of lump charcoal: hardwood and softwood.
- Hardwood charcoal is made from dense, slow-growing trees like oak and hickory. It Burns hot and produces little smoke, making it ideal for grilling.
- Softwood charcoal is made from lighter, faster-growing woods like pine and spruce. It burns less evenly than hardwood charcoal, but it’s also cheaper and easier to light.
No matter which type of charcoal you choose, it’s sure to add some flavor to your next cookout.
That’s lump charcoal. But there’s also the stuff called charcoal briquettes. These are made from a mix of materials and chemicals such as sawdust, coal dust, and other ingredients like borax, limestone, and starch.
The briquettes are formed into their characteristic shape under high pressure.
Why Is Composting Beneficial?
Composting is truly a magical process. It’s like taking your garbage and turning it into gold. Or, more accurately, turning it into compost, which is basically black gold for your garden. Composting is often seen as a chore, but it doesn’t have to be!
In fact, composting can be a fun and rewarding experience. Not to mention, it’s great for the environment. When done correctly, composting can help to reduce the amount of waste that ends up in landfills. It can also help to improve the quality of your soil, making it more fertile and productive. The nutrients in compost help promote plant growth, and the compost itself can help retain water in the soil, making it more drought-resistant.
And composting is easy! All you need is a compost bin or compost pile and some kitchen scraps. With a little bit of effort, you can make your own compost and help to make the world a better place.
Here’s how it works: composting is the process of breaking down organic matter, such as food scraps and leaves, into a nutrient-rich soil amendment. Composting requires two types of organic matters:
- nitrogen-rich material
- carbon-rich material
The nitrogen-rich materials are usually green and wet, like grass clippings or fruit and vegetable scraps from the kitchen. The carbon-rich materials are usually brown and dry, like dead leaves, dry twigs, or hay.
Charcoal is also considered brown material since it’s virtually all carbon. Charcoal also contains fairly high amounts of potassium and phosphorus, two important nutrients for plants.
Lump Charcoal Is Usually Safe To Compost
Lump charcoal is usually fine to add to a compost bin. As mentioned before, it’s made from wood that has been burned or pyrolyzed in a low-oxygen environment. So in theory, it should be eco-friendly.
Even though you can put partially burned charcoal and charcoal ashes into your compost bin, you shouldn’t add large quantities at once. Charcoal is alkaline and can raise the pH of your compost, making it less acidic. This can be detrimental to the microbes that help to break down the organic matter.
Also if you know that your soil is already alkaline by itself, you probably don’t want to make it even more alkaline by adding charcoal ashes to your compost. On the other hand, if your soil is too acidic, adding some charcoal to your compost could help to balance it out.
Before you dump the entire contents of your grill into your compost bin, it’s always a good idea to remove the big chunks of charcoal. You can either crush these pieces a bit so that they are easier to break down in the compost bin or you can reuse these bits of charcoal for your next barbecue. Furthermore, spread the ashes around in the compost, and don’t leave them in a single big pile.
Not all charcoal is made equal
One thing to keep in mind is that although most lump charcoal is OK to go in the compost bin, some manufacturers add additives even to their lump charcoal. So it’s always a good idea to check the labels before buying.
Anything that’s labeled as “match light”, “easy light”, or similar, most likely contains lighter fluid that you really don’t want in your compost.
Sometimes you have to check the material safety data sheet (MSDS) to find out what’s in the bag.
Important: If you plan on using the charcoal ashes and partially-burnt pieces of charcoal left over after your barbecue, don’t make the mistake of using lighter fluid to start the charcoal. Use an alternative way instead such as a chimney starter filled with paper or pieces of dry wood.
Avoid Composting Charcoal Briquettes
We’ve already established that charcoal and charcoal ash may be beneficial for your compost pile. Now, what about charcoal briquettes? After all, they are perhaps the most used type of fuel used for grilling. They’re made of organic materials, so they must be good for the compost pile and the environment, right?
Wrong. The main problem with charcoal briquettes is that they usually contain additives that can be harmful to the compost microbes and the plants that you’re trying to grow. So, in turn, the composted briquettes may be harmful to you if you eat the plants grown in compost contaminated with these chemicals.
The most common additive found in briquettes is the lighter fluid that is added to help start the fire. Although the fluid gets burned off during the grilling process, it can still leave harmful residues in the charcoal ash. Other additives may be present as well.
Are all charcoal briquettes bad for your compost?
Even though I may have sounded overly negative, there’s still hope for those who want to compost their charcoal briquettes.
The thing is that some eco-friendly briquettes may contain no harmful additives at all. These will be labeled as such and there’s a chance they may be compostable.
Again, you can check the MSDS to see if there’s anything potentially harmful in the briquettes. If in doubt, I would recommend contacting the customer service of the briquette company to ask about their product’s compostability. A good company should always be able to respond to its customers’ inquiries.
Charcoal As a Fertilizer
Not only can you compost charcoal, but you can also use it as a fertilizer or soil amender thanks to its high concentrations of potassium, phosphorus, and calcium.
These nutrients (especially potassium) are essential for plant growth, and they can help to improve the overall health of your garden.
Additionally, charcoal is alkaline, which can help to neutralize acidic soils.
To use charcoal as a fertilizer, simply scatter over freshly tilled soil and rake it in at the beginning of the growing season. It’s best to use charcoal ash or at least crush the larger pieces of charcoal. Depending on the type of soil at your disposal, about 5 pounds of ash can be scattered over an area of 100 square feet.
Just like with compost, keep the amount of charcoal used at bay. Otherwise, you are risking making your soil too alkaline. This can lead to the stunted growth of plants.
Avoid using charcoal as a fertilizer for plants that prefer acidic soil such as blueberries or rhododendrons.
Charcoal ash can also be used as mulch, again, keep the amount relatively low to not cause problems. Also, make sure to not apply the ash directly to the plants because that may cause burns.
So, can you compost charcoal? The answer is yes! In moderation, charcoal can be a great addition to your compost pile. Remember to avoid any charcoal that has been treated with chemicals, as these can leach into the soil and potentially harm your plants. Lump charcoal is generally safe to compost, while charcoal briquettes should be avoided unless you know for sure they are chemical-free.
Using charcoal ashes in your garden is certainly a better option than simply throwing them away.
Does that mean you won’t have to dump any charcoal ash in the trash can? Unfortunately, no, especially if you are an avid grill master. Even if you’re composting and using the charcoal ashes in your garden, there will probably still be some left because you can only use the charcoal in fairly small amounts.
Happy grilling and composting!
What is biochar?
Biochar is a substance similar to charcoal. It is made from biomass, such as tree trimmings, corn stalks, or coconut shells. Biochar is often used as a soil amendment because it can improve the soil’s fertility and water retention.
Can you compost Kingsford charcoal?
Kingsford charcoal briquettes contain ingredients that shouldn’t be added to your compost. It is specifically mentioned on their site to not put the Kingsford® and Kingsford® Match Light® briquettes in your compost.