tuhka

Tuhka is the fine powder remaining after the combustion of organic material. In everyday Finnish usage it typically refers to ash from wood-burning and other biomass fuels, but scientifically the term also covers mineral and volcanic forms of ash. The composition depends on the source and can include silicates, carbonates, and metal oxides such as calcium, potassium and magnesium.

Volcanic ash is a natural form of tuhka produced by explosive eruptions. It consists of microscopic to fine-grained rock and mineral particles that can blanket landscapes, waterways and infrastructure. Fine ash poses health risks when inhaled, and can affect aircraft engines, machinery, water systems and visibility.

Wood ash is the most common domestic form. When derived from untreated biomass, it is alkaline and contains calcium carbonate and potassium carbonate, among other minerals. It is sometimes used as a soil amendment to raise pH and supply nutrients, but should be applied cautiously after soil testing. Excessive application can alter soil chemistry, and ash from painted, treated, or chemically contaminated wood should not be used in gardening or composting.

Handling and disposal: ashes should be stored in a metal or ceramic container with a tight lid and kept dry. They should be cooled before disposal and not dumped into flammable areas, waterways, or systems where the alkalinity could cause damage.