Ash from power plants suited for use as fertilizer in most cases


<div>Evira investigated in 2007 the suitability of ash from power plants for use as fertilizer, as well as the quality and the reuse applications of ash. 21 ash samples proved suited for fertilization of fields and 33 ash samples only for fertilization of forests. Evira banned 12 ash samples from use as fertilizer due to high levels of harmful metals. None of the ash samples were banned due to a high cadmium level alone.</div>

The project encompassed a total of 374 power plants, and 163 of these reported that ash was delivered from the plant for use as fertilizer. Inspections that included sampling of the ash were carried out in 40% of these plants. The ash samples were analysed and in 12 cases the use of the ash as fertilizer was banned because the analysis results showed excessive levels of harmful metals. Two bans were imposed due to unsuitable raw materials.

Harmful metals with regulatory limit values include arsenic, mercury, cadmium, chrome, copper, lead, nickel and zinc. Arsenic was the cause of the ban in six ash samples, cadmium in five samples, nickel in four samples, zinc in four samples, chrome in two samples and both copper and lead in one sample. 

The cadmium levels in ashes suited for fertilization of fields remained under the Finnish limit value of 2.5 mg/kg of dry matter, with levels varying from < 0.2mg/kg to 2.5 mg/kg. For ash used as forest fertilizer the limit value is 17.5 mg/kg.

Evira registers and controls heat power plants that produce ash for use as fertilizer. Evira can forbid the marketing or use of the ash if the ash does not meet the regulations. The producers, or the combustion plants, are liable to organise in-house control and responsible for the quality of the ash. The plants have the ash analysed at Evira or some other competent laboratory. When the ash is sold, it must always be accompanied by a product declaration that must not be more than a year old. The product declaration shall indicate the level of harmful metals in the ash, for example, and the intended application as either field or forest fertilizer.

Power plants that use only clean wood, peat or energy plants as raw material for energy can deliver ash for use as fertilizer. The raw material may, however, contain harmful metals originating from the felling area or the pH value of the soil. Ash contains phosphor and potassium, but no nitrogen. It also contains calcium and therefore decreases the acidity of the soil. This makes ash suitable for use as fertilizer in fields, including fields used for organic farming, as well as in green construction and particularly in bog forests.

Evira continues intensified control of ash from power plants also in 2008. The results will be utilised in the determination of the need for inspections based on risk-informed control.

For more information, please contact
Titta Pasanen, Senior Officer, Evira, tel. +358 (0)2077 25245



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