The second condition is that wood ash itself may only be used in composts to a limited degree—around 1 cup per foot of compost—as large amounts of wood result in a loss of nitrogen in the soil. As with wood ash, only use a similar cupful of ash for each foot of compost. So long as you don’t barbeque every day, however, charcoal BBQ ash is perfectly safe to put into your compost pile or bin.
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