Download PDF Presentation Ash utilisation
Since its foundation one of BIOS’ main focuses has been on the sustainable utilisation of biomass ashes and the consequent development and improvement of ash utilisation processes. The comprehensive Know-How and experience gained guarantees a successful execution of R&D and engineering projects in this field.
BIOS is a competent partner for the management and execution of R&D projects regarding biomass ash utilisation and the planning and realisation of biomass ash utilisation concepts.
Fields of activity
BIOS offers the following services related to ash utilisation:
BIOS provides services related to ash utilisation for the following clients / customers:
In Austria the energetic utilisation of woody biomass in heating and combined heat and power plants increased by about 39% from 2005 to 2015 (source: Statistik Austria). The same is true for other European countries like Germany, Italy or Scandinavia. The promotion of energy production from biomass has also led to a strong increase in the amount of combustion residues, i.e. ashes. Therefore, increasing importance is attached to a sustainable and cost efficient utilization of wood ashes and other biomass ashes.
At present, a large fraction of the biomass ashes produced is disposed of in landfills. Considering the fact that biomass ashes are a valuable secondary raw material for fertilizing and soil improving measures as well as soil stabilization the current situation is far from satisfying.
According to a report of the Environment Agency Austria (Umweltbundesamt) from 2016 (Biomass ash mass flows in Austria) the thermal utilisation of biomass resulted in 133,000 tons of ash (excluding small-scale applications) in Austria in 2013. Almost 50% (58,300 tons) of the ash were disposed of in landfills in 2013. In Austria disposal costs range from 60 to 100 €/t on average, but up to 200 €/t are possible in worst case. Accordingly, the annual costs for ash disposal are significant. An increased utilisation of biomass ash is therefore of high interest both for the economy and the closing of the mineral cycle.
Biomass ash – a valuable secondary raw material
Ash from natural solid biomass fuels contains valuable plant nutrients such as K, P, Mg and Ca. Thus, their application on agricultural or forest soils can significantly contribute a closure of the mineral cycle. The rather high content of Ca in wood ashes (between 20 and 35 wt%, dry basis) facilitates a utilization as a binding agent for soil stabilization (similar to burnt lime).
However, biomass ashes also contain significant amounts of heavy metals, which have to be considered for the utilisation strategy applied. Therefore, only the fractions rich in nutrients or other valuable components and poor in heavy metals (bottom ash and coarse fly ash) shall be used for fertilizing, soil improvement or soil stabilization purposes. The fraction rich in heavy metals and rather poor in nutrients or other valuable components have to be disposed of. The distribution of nutrients, other valuable components and heavy metals over the individual ash fractions depends on the type of combustion technology applied:
Considering the points listed above, bottom ash and coarse fly ash from grate furnaces as well as fly ash from fluidised bed furnaces (and under certain circumstances also bottom ash) are the fractions most suitable for further utilisation.
Current status of biomass ash utilisation in Austria
The ash utilisation strategies currently possible in Austria are described briefly below. For a general overview of biomass utilisation in Europe see Download #003: Possibilities of Ash Utilisation from Biomass Combustion Plants
Application of ashes on agricultural and/or forest land:
The basis for the utilisation of biomass ashes on agricultural and/or forest land is, besides the Waste management law and its ordinances (waste monitoring ordinance and waste balance ordinance) together with the federals state laws for soil protection; the Guideline for the proper utilisation of biomass ashes on agricultural and forest soils (Biomass ash guideline, in German “Richtlinie für den sachgerechten Einsatz von Pflanzenaschen zur Verwertung auf land- und forstwirtschaftlich genutzten Flächen”), which entered into force as from 01.01.2011. According to this guideline, the application of biomass ashes is allowed under the following framework conditions:
The application of ashes on agricultural or forest land requires an appropriate ash treatment in order to meet the requirements of the ash application process intended by the end user. The following tasks have to be considered prior to the application (for ash utilisation in Austria):
Utilisation as an additive in composting
The basis for the utilisation of biomass ashes as an additive in composting is, besides the Waste management law and its ordinances (waste monitoring ordinance and waste balance ordinance), the composting ordinance, which entered into force as from 2001. According to the composting ordinance, the utilisation of biomass ashes is allowed under the following framework conditions:
Indirect ash application via composting features some advantages compared to a direct application of ash to agricultural and forest land:
Research results from the FFG industry project (see section FFG collective research project „ Development of innovative processes for wood ash recycling“) show that additions of up to 8 wt% (wet basis) are ecologically sensible.
As of 2020, an amendment to the Compost Ordinance is in progress. At EU level, the inclusion of ash, biochar and struvite (a phosphate-containing mineral recovered from wastewater) as permitted starting materials for the production of fertilizers (for details see section Registration as a fertiliser below) in the EU Fertilizer Product Ordinance (FPR) is currently being discussed. The inclusion of these secondary raw materials as starting materials for fertilizers could be decided in 2021. These changes would then also have to be taken into account in an amendment to the Compost Ordinance.
Registration as a fertiliser
Since the latest amendment of the Austrian fertiliser law in April 2017, combustion residues (i.e. ashes) may be used as fertilisers or additives to fertilisers, if the regulations of the fertiliser law and its related ordinances are met. The application for approval can be filed by the producer of the ash itself (if an individual ash fraction shall be approved) or by any fertiliser producer (if the ash fraction is used as a raw material for fertiliser production).
During the approval procedure the chemical properties of the ash (heavy metals, nutrients, total organic carbon, organic harmful substances) and the source of the ash (only ash from chemically untreated biomass is allowed) are checked. Ashes which meet the limiting values of the biomass ash guideline may also be eligible for approval as a fertiliser. Additionally, at least one primary (N, K, P) or secondary nutrient (Ca, Mg, Na, S) must be contained in relevant amounts. The minimum contents of nutrients defined in the approval and the limiting values of harmful substances defined in the fertiliser law must be kept at all times by the approved ash fraction.
The main advantage of the registration of an ash fraction as a fertiliser is the fact that this fraction is no longer considered as a waste. This facilitates the utilisation, since farmers and forest owners that use the approved ash are exempt from the reporting and recording duties that are required for any kind of waste utilisation.
On July 16, 2019, the new EU fertilizer regulation ((EU) 2019/1009) came into force (national implementation by July 16, 2022). On the basis of the regulation, the Commission can include biomass ash and other potential raw materials (e.g. struvite, a phosphate-containing mineral recovered from wastewater, or biochar) as permitted raw materials for fertilizers (listed in Annex II of the regulation) within the framework of delegated acts. The delegated acts for biomass ash, struvite and biochar were presented to the fertilizer expert group in the Commission in autumn 2019. There is currently a discussion about the inclusion of these raw materials as permitted starting materials for the production of fertilizers in the EU Fertilizer Product Ordinance (FPR). The inclusion of these secondary raw materials as starting materials for fertilizers at EU level could be decided in 2021
Utilisation as an additive in the cement industry
The basis for the utilisation of biomass ashes as an additive in the cement industry is, besides the Waste management law and its ordinances (waste monitoring ordinance and waste balance ordinance), the plant approvals of the individual cement factories. The framework conditions for the utilisation of biomass ashes depend on the conditions defined in the plant approval and may differ between different cement factories.
To some extent, the existing utilisation strategies are used, but still almost 50 wt% of the biomass ashes generated annually in Austria are landfilled. Moreover, interesting new utilisation options (utilisation as a building material for forest streets, utilisation as a binding agent for soil stabilisation) exist, that are currently not executed in Austria. This is due to the fact that not all ecological, logistic, technical, and economic aspects have been covered and investigated yet and that sufficient legislation is still lacking to a large extent.
In order to tackle these deficits, BIOS initiated a R&D project, funded by the Austrian Research Promotion Agency (FFG), with the goal to optimise existing biomass ash utilisation strategies and to research and develop new utilisations options. The main facts and findings of this project are presented below.
FFG collective research project „ Development of innovative processes for wood ash recycling“
The FFG collective research project was initiated by BIOS in cooperation with the trade association of the Austrian wood processing industry (FHP, platform for forest, timber and paper). The project consortium included renowned scientific partners and partners from different industry sectors.
Main facts of the project:
The project aimed for the following overall goals:
One main goal of the project was the development, evaluation and assessment of new and practicable recycling processes for wood ashes. In this regard the project focused on the evaluation as well as the techno-economic and environmental assessment of the utilization of wood ashes on short-rotation-coppice fields and as a binder in forest and conventional road construction. These new recycling processes show great potential but have not been investigated yet in detail in Austria.
Beside new innovative processes for wood ash utilization also already established recycling processes like the utilization of wood ashes as an additive in composting or the application on forest soils were investigated in detail.
In summary, the results of this project reveal that the utilisation of wood ashes in agriculture and forestry or in forest and conventional road construction for soil stabilization is technically and economically feasible and under consideration of the defined framework conditions also environmentally safe. As a conclusion, the preconditions for the increased utilization of wood ashes in Austria are given. If all possible utilization potentials are used up to 800,000 t of wood ash could be recycled every year, which exceeds the annual amount of wood ashes in Austria (some 133,000 t in 2013 according to the Report of the Environment Agency Austria 2016) several times. To increase the recycling of wood ashes significantly, a scientifically verified and uniform approach for the newly developed utilization options (forest and conventional road construction for soil stabilisation) has to be defined and existing legal guidelines like the Austrian Compost Ordinance have to be adapted accordingly.
In addition, FACT SHEETS have been prepared for relevant areas of the utilisation of wood ashes, which summarise the relevant Q&A for owners of biomass combustion and CHP plants and potential end users of the ash alike.
The final scientific report can be obtained directly from the Austrian Wood Industry Association (Requests to Dipl.-Ing. (FH) Rainer Handl via firstname.lastname@example.org).
Based on the results of the project a guideline for the proper utilization of wood ashes in forest and conventional road construction for soil stabilisation, which includes all relevant technical, economic and environmental framework conditions is under preparation. The main goal is the definition of a standardized approach for operators of biomass heating and combined heat and power plants as well as for users of the biomass ash, which is accepted by the relevant authorities. This way a short approval process shall be achieved and ashes that are used as building material or binding agents shall be considered as raw materials rather than waste.