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Wood ash
recycling, Why?
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 rökgasutsläppen 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
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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 (see description of our machines on
the side "our 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.
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