Hands in compost5 Reasons why fire ash is bad for compost

Composting is an incredible way to reduce waste and create nutrient-rich soil for gardening. However, not everything can be added to a compost pile, and ash is one of them. While you may think that ash is a natural and harmless addition to your compost bin, it can do more harm than good. In this blog post, we’ll explore the reasons why ash is not suitable for compost and how it can negatively affect our compost.

1. High pH levels

Ash is highly alkaline and can raise the pH level of your compost to an unhealthy level. The ideal pH level for compost is between 6 and 7. If the pH level is too high, the beneficial microbes that break down the organic matter will become dormant, and the composting process will slow down. Additionally, plants prefer a slightly acidic soil pH level, and high pH levels can cause nutrient deficiencies in plants.

2. Heavy metals

Ash contains heavy metals like lead, cadmium, and arsenic, which can be toxic to plants and the environment. While wood ash contains fewer heavy metals compared to coal, charcoal, or briquettes, it is still not safe for composting. Composting with fire ash can result in the accumulation of these heavy metals in the soil, and they can leach into the soil – not nice.

3. Fire ash is bad for compost as it contains salt

Fire ash is also rich in salt, which can be harmful to many plants. Salt can burn the roots of plants and prevent them from absorbing water and nutrients. Composting with fire ash can increase the salt content of your compost, which can negatively impact the growth and productivity of your plants.

4. Contamination

Fire ash is known to contain small pieces of plastic, glass, or metal that can contaminate the compost. While you may think that these objects will decompose eventually, they can take several years to break down. The plastic or glass can also release toxins into the soil, making your compost unsuitable for use. It is best to avoid adding fire ash to your compost bin to prevent contamination and ensure that your compost is of high quality.


In summary, adding fire ash to your compost bin may seem like a natural addition, but it is not. Fire ash can affect the quality of your compost and negatively impact your plants and the environment. Instead, consider adding other organic matter like food scraps, shredded leaves, and grass clippings to create a nutrient-rich compost that is safe for use. By avoiding the use of fire ash in your compost pile, you can maintain the health of your soil and enjoy the benefits of a thriving garden.