Wood ash recycling

Wood ash recycling

Since industrialization really took off in the 1900s, coal and other fossil fuels has been used for heating and electricity generation for the industry. Polluting and acidifying sulfur emissions from industry for decades has increased the acidification of forest soil, the degradation of tree and animal living conditions.

Since the 1990s, environmental awareness has grown and less fossil fuels is used and the purification of gas emissions has become markedly better. Use of renewable fuels such as wood chips and pellets has increased, replacing the fossil, thus also affecting that the sulfur acidification and CO2 emissions have decreased. Unbelievably good for the environment. However the cars emissions and the acidifying effects of increased withdrawals from the forest is still there.

Now it has emerged a new problem that must be solved to save the forest and let it be a renewable fuel source. We need to compensate for the large amount of wood and harvest residues (branches and tops) that are removed from the forest. During bio-fuel harvesting and timber production, nutrients are removed from the forests. In the past, only the timber was harvested and branches and tops were left to decompose, much of the nutrients were re-circulated to the soil. In future forestry also stumps might be recovered from the forest. If we continue along this path the forest soils will be depleted of nutrients resulting in lowered production and increased soil acidification.

But if we return the nutrient rich ashes to the forest soil we can harvest wood and residues at the current rate and secure both a sustainable forestry and a high energy production simultaneously.

The recycling of ash from the combustion of biomass fuels have been shown to cause increased soil pH and nutrient concentrations. If you re-cycle the ashes, you return these nutrients to the forests,
and thus close the nutrient cycle and maintain a viable forest.

The Forestry Board recommends ash recycling. It assumes that the ash comes from combustion of pure wood pulp and not from demolition waste. Normally 3 tonnes of ashes are spread per hectare.

How does it work?
Ash producer and Askungen Vital AB signs a reciprocal agreement where we manage the entire chain from ash output until the ashes are out in the woods. The ash is taken from the thermal plant or sawmill to one of our storages.

The ashes needs to be stored for at least 3 months in order to harden. During this process the ash becomes less alkaline. When the ashes are hardened, they are crushed and sieved to a grain fraction that does not harm the trees at spreading and were the dissolution rate of the grains in the forest soil is optimal.

After consultation with the Forestry Board the appropriate stock is selected. The area are identified and the treatment method and the volume of material is determined.

The ash is loaded on swap cargo beds and transported out to the forests. The ash spreader will meet up with the swap cargo beds at the place were the ashes are unloaded, before driving further into the forest, where the truck fails to get through. Then we spread it with one of our spreading machines.

The landowner receive an analysis report on spread material. This is obtained before or after application. The National Board of Forestry has set recommendations for what the ashes must contain.

Result?
Pretty immediately, the upper part of the land will have an elevated pH, which reduces the toxic effect of hydrogen and aluminum on the tree roots. The administration of potassium and trace elements absorbes by the trees, which benefit the development and vitality.