The benchmarking started with Johan Palm giving an overview about the whole project. It turned out, that in Latvia, a large amount of DH is produced by natural gas, whereas Sweden builds also some Liquid Natural Gas terminals to meet the energy needs for south Sweden, but views wood fuels as more compatible at the moment.
According to Hillevi Erikson, using ash as the only fertilizer is a bit problematic at the moment as with ash you don’t bring back nitrogen to the forest. Therefore there is a loss of nitrogen in the life cycle. The ash has a too high Bromide concentration in some cases as well.
Eva Ring, Researcher in SkogForsk. said that research has shown that the ash does not affect the soil in such a big amount as thought. The rain water, that comes in contact with ash does not reach the the water bodies of rivers and lakes directly, it flows through the soil. No extended effect period on tree growth. The soil acts as a filter for the water.
Katri Ots from the EULS gave an overview about the forestation of cut-away peat lands and about the effect of wood ash as fertilizer. The results of a research of Tartu boiler house wood ash are shown in the diagram above.
The Linneaus University, that is located in Växjo was represented by Tommy Claesson. He made a presentation about ash samples that have 60% unburned content; therefore it is cycled several times through the furnace. 60% sludge and 40% dry ash makes a nice product as fertilizer. Potassium has a low content in this material, sodium has a high content.
Before the benchmarking group was taken to the ash storage site for getting a practical view of the recycling process, Lars Strand showed the practical issues in ash spreading while Karina Pedersen presented the economical side.
Why making an energy plan?
In Sweden, It is obligatory to make an energy plan for the region, thereby giving a good input for related energy decisions. E.g. in Växjö, small scale energy applications are promoted to show to visitors that their city is innovative and it’s planning policy is “green”. The main problem yet to solve in becoming a CO2 free community is the transport. At the moment the main renewable transport fuel is ethanol.
On the second day of the benchmarking, field visits to the ash recycling sites were made.
The spreading of ash in practice was shown in the forest of Per Gyllensvärd. The equipment shown in the picture above is used for ash spreading in the summer time and for transporting wood in the winter time, thereby reducing the payback time. The spreading process is controlled by a computer that in order to ensure an even spreading of the ash. In the woods, a 20 m radius can be covered, whereas in the in a field a radius of 50 m is possible.
Swedish rural affairs minister: Forest gives an important share of the swedish export and its also important for recreational activities. Sweden had an forestry based heating energy system hundred jears ago. Then it got to more imported fossil fuels.
Since 1990 the co emission has decreased and in the meantime the economi has increased by 51%. The first swedish forest act from 1903 was concentrated on reforestation. The wood resource of Sweden is more than doubled in the years 1920-2000
After meeting the Swedish Minister of Rural Affairs, final conclusions of the event were made:
Steps for ash recycling are:
- Estimating the limits for the ash concentration and heavy metals
- Researching about the long-term influence, testing the theories
- The swedes learned that the granulation of ash is unneccessary
Alo Allik & Jaanus Uiga