Are ashes from the barbecue grill safe to apply to your lawn?

Simple answer, yes. The composition of wood ash is influenced by the type of wood that has been burned. Also the conditions of the combustion affect the composition and amount of the residue ash, thus higher temperature will reduce ash yield. Basic charcoal is produced from wood. For a long time wood ash has been used in agricultural soil applications as it recycles nutrients back to the land. Wood ash has some value as a fertilizer, but does not contain nitrogen. Because of the presence of calcium carbonate it acts as a liming agent and will deacidify the soil increasing its pH