The majority of the solid waste produced by UPM is ash from bioenergy production. Over 95 percent of the ash is already used in construction work, cement and brick industry, or as fertiliser. For example, from the Jämsä river mills industrial area no ash has been taken to landfills since 2007. The new, stricter landfill tax that came into effect the same year in its part speeded up the search for new uses.
Ash is a difficult waste fraction because it’s created in large amounts: within UPM about 150 000 tonnes per year. Less than 50 000 tonnes of it is used as fertiliser, and the rest goes to construction work.
“At the moment too much ash that could be used as a fertiliser is used in construction work – partially because of the legal requirements for the composition and origin of the ash. In an ideal situation all suitable ash could be used as fertiliser. This would be good for the environment and for the circulation of nutrients, and would also be cost-efficient,” says Environmental Engineer Pekka Rantala. The composition of the ash, and the nutrients and possible heavy metal residues it contains vary by mill and by batch.
The composition of the ash and how it can be reused depend on what is being burned. There are more uses for pure wood ash than there are for ash that combines other forest industry by-products with wood.
Ash restores nutrients to the forest and builds the foundation for sturdy forest roads
The most nutritious ashes are taken from UPM mills to a company that manufactures forest fertilisers. The lime-rich ash is delivered to fields to improve the soil. The ash is turned into a fertiliser by an external partner, who works in co-operation with other companies in the forest industry as well.
“Using ash as a fertiliser is a good way to restore the nutrients that leave with the wood to the forest. The problem with fertilising forests has been the high price. Alternative means of spreading the fertiliser that are cheaper than using helicopters are being developed,” says Rantala.
There are also on-going discussions about the possibility of mixing ashes with other nutrient-rich components to create a fertiliser that has better resale value than pure ash.
Some of the ashes are recycled back into production. ELURIT, a product based on fly ash, is used in paper production in boiling and bleaching the pulp. Fly ash, which is a byproduct of burning bio waste, is also used to manufacture Cinerit mass, which is used in the building industry. Ash is also used in construction work and building forest roads. Here and there ash has been used in the foundations of walkways.
“When ash is mixed with wet soil, it creates a stable, hard foundation. In roadwork, ash-soil mixture can be used to substitute crushed stone. In some European countries, the government subsidises the use of industrial by-products in construction work, and we would welcome this type of actions also here in Finland. Additionally in Finland the environmental permit procedures have proven to be difficult and too strict even when using high-quality ash. Applying for permits is slow, and many projects have such tight schedules that the by-products cannot make them,” says Rantala.
The varying quality of the ash, and the geographically dispersed factories also make the cost-efficient collecting and refining of this waste fraction challenging.
“The Finnish government should also commit to the principles of circular economy to accomplish significant changes," Rantala concludes.
Main picture: Ash can be used to fertilise forests or fields.