Charcoal & Ash Hazardous Waste Hot Coals Are a Fire Hazard Allow coals and ash to cool for 48 hours, or pour water onto them and stir carefully to speed up the process. Do not attempt to dispose of them until they have fully cooled. Dispose of Ash Carefully Once ashes have fully cooled, wrap them in aluminum foil or place them in a small metal container, such as a coffee can, and dispose of them in an outdoor trash. Do not place them near anything that could catch fire. Throw the Bag Away Most charcoal bags are paper lined with plastic. Recycling facilities cannot separate the two materials, so you must throw bags in the garbage. Ways to Reduce Grill With Propane Instead Propane grills are a more eco-friendly option than charcoal grills. Ways to Reuse Used Charcoal Is Fertilizer If your used charcoal is additive-free, you can use it to fertilize plants. It is alkaline and contains the nutrient potash. Avoid using it with plants that require more acidity (e.g., hydrangeas and azaleas), as well as new seedlings. Repurpose Unused Charcoal Around the House If your unused charcoal is additive-free, use it to neutralize odors, prevent metal from rusting, or balance nutrients in potted plants, garden beds and compost piles. For more inspiration, check out these ideas from This Old House.