Disposing of BBQ coals and ashes safely
July 25, 2019
If you use a charcoal BBQ, disposing of the ash can be a headache.
Nobody wants a bin fire outside their home. Likewise, it’s sensible to avoid setting fire to the waste collection vehicle that serves your area. However, with a bit of planning your used ashes can be of benefit to your garden, or at least can be disposed of safely and with minimal waste.
Before you cook:
- Avoid a disposable barbecues if possible – As with many single use product they offer convenience but at the cost of the planet. Disposable barbecues can’t be recycled and manufacturers also recommend that they aren’t reused / refilled with fresh coal either.
- Use a good quality untreated charcoal on your grill. Ash from untreated charcoal can be used in your garden. Treated (typically sold as ‘easy to light’) charcoal ashes can be toxic and shouldn’t be used in the garden. The ash from treated charcoal will need to be disposed of in your residual waste bin (i.e. sent to landfill).
- Use the minimum amount of charcoal possible. Always follow any manufacturers instructions that came with your BBQ, but typically a 2 inch / 5cm layer of charcoal in the bottom of your grill is more than enough.
- Keep a bucket of water or sand nearby while cooking – just in case you need to put out the BBQ quickly.
What to do with used charcoal (Ashes)
If you have a BBQ grill with a lid and vents close them when you have finished cooking to starve the coals of oxygen. Doing so also reduces the chance of a coal or ember escaping while you wait for the coals to extinguish. Starving the coals of oxygen increases the chance of leaving unused charcoal in the bottom of your grill which can be used the next time you cook. If you try this, make sure you remove as much of the ash as possible from the leftover charcoal. Keep the leftover / partially burnt charcoal in the bottom of the grill dry until you are ready to reuse it. When you are ready to cook again spread a layer of fresh charcoal on top and use as normal.
If you don’t have a lid or vents or you are using a disposable barbecue either let it burn out (this can take several hours) or extinguish it using sand or water. Keep in mind that unused coals that have been soaked in water will be extremely difficult to relight / reuse so you may be better off disposing of them rather than trying to reuse.
If you do extinguish your BBQ, please let everything cool down before you attempt to move it or dispose of it. You can still be burned by hot water or sand. Smoldering coals and hot ashes can also set fire to items in your bin, or in a waste collection vehicle.
If you don’t have a use for your ashes (see below) these should also be placed in the residual waste bin. Make sure they are completely cold before moving them. If you use something to transport the ashes to the bin – please make the effort to use something reusable, or if you are going to throw your ashes away in a container or bag please use a non-recyclable item.
Uses for BBQ ash in your garden / allotment
- Fertiliser: Ash from additive-free wood charcoal contains a lot of potash (potassium carbonate) which is nutritious for many plants. Potash can change the pH of your soil making it more alkaline, so be cautious with its use. Don’t use charcoal ash with acid-loving plants (e.g. azaleas and hydrangeas). Newly planted seedlings and seeds don’t like potash either.
- Deter Pests: Some gardeners use charcoal ash as part of a home made pest deterrent spray. Mix about 30g of ash and 30g of calcium hydroxide (also called: slaked lime, hydrated lime, caustic lime, and builders’ lime) to 4 litres of water. Spray the mixture around the plants you want to protect.
Uses for unused charcoal
If you have a bag of unused charcoal sitting round that you aren’t going to barbecue with, disposing of it in the bin is your last resort. It can also be used to:
- Reduce Odors: Unused charcoal is great at absorbing odours. Place a handful of charcoal in a cloth bag (or a clean sock) and keep it in your fridge or freezer to absorb food smells. It should also work with stinky shoes and trainers.
- Compost It: Adding the odd piece of unused charcoal to your compost heap will add carbon, which is vital to the composting process (charcoal is a ‘brown’ material. However, don’t be tempted to add more than a handful to your compost bin at a time. Any charcoal that ends up in your soil undecomposed can act to restrict the growth of your plants. In fact, powdered charcoal can be used to suppress the growth of weeds.
- Make cut flowers last longer: Apparently adding one small piece of charcoal to the water of cut flowers can make them last longer.