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• DiversE: Energy Use of Grass Biomass from the Ljubljana Marsh – Economic Perspective and Regulatory Framework

DiversE: Energy Use of Grass Biomass from the Ljubljana Marsh – Economic Perspective and Regulatory Framework

• 1. 4. 2026

At the second Slovenian Focus Lab event of the DiversE project, stakeholders discussed the possibilities for the sustainable use of biomass from late mowing in the Ljubljana Marsh. The discussion focused on economic and regulatory aspects of energy use, as well as alternative material uses. It highlighted the need for clear business models, an appropriate regulatory framework, and stronger cooperation among key actors.

 

The second Slovenian Focus Lab event, organized within the pilot activities of the DiversE project by the Public Institute Landscape Park Ljubljana Marsh (JZ KPLB) and the Regional Development Agency of the Ljubljana Urban Region (RRA LUR), took place on 24 March 2026 at the Technology Park in a hybrid format. This format proved effective in engaging a broader range of stakeholders.

The use of open dialogue approaches and tools (the Open Dialogue Toolkit), developed and tested by DiversE project partners, enabled active participation, exchange of views, and structured discussion among participants.

Participants included representatives of several protected areas – Ljubljana Marsh Landscape Park, Radensko Polje Landscape Park, Notranjska Regional Park, and Kozjansko Regional Park. Experts from research institutions (National Institute of Chemistry, Faculty of Mechanical Engineering), representatives of Local Action Groups (LAGs), a farmer representative from the Ljubljana Marsh, representatives of the Chamber of Agriculture and Forestry, the Chamber of Commerce, and energy companies also took part.

The meeting continued discussions on sustainable management and use of grass biomass resulting from the conservation measure of late mowing. The first event in February 2026 presented preliminary biomass analysis results (chemical composition, moisture content, calorific value, etc.) and stakeholder experiences. The second event focused on the economic and regulatory aspects of the business plan for energy use of biomass from late mowing. Potential material uses (e.g. biochar) were also presented.

Economic aspects of energy use

The discussion focused on the techno-economic feasibility of using grass biomass as a local bioenergy source. Its utilization requires a comprehensive approach, including technology, logistics, and investment planning.

It was emphasized that combustion of such biomass is complex and requires an organized system for collection, transport, drying, storage, and appropriate combustion technology.

Technical challenges include higher ash content, particle emissions, slagging, and corrosion. Therefore, appropriate boiler design and flue gas cleaning systems are essential. Establishing such a system requires significant upfront investment.

A larger available biomass supply would improve economic performance by shortening the payback period but would also increase heat production. A key challenge is therefore finding consumers for excess heat, for example through district heating systems.

Heat price significantly affects the payback period, and ensuring a stable heat demand throughout operation is crucial. The location of the heating system is therefore critical, particularly in relation to potential heat consumers.

The next step is to further develop the project by obtaining concrete technological offers and engaging municipalities or local communities as potential heat consumers and investors.

Legal and regulatory framework

An important part of the discussion addressed regulatory aspects. The planned heating system would likely exceed the threshold for small combustion plants (<500 kW).

Grass biomass is not explicitly defined in legislation but is indirectly covered under broader biomass categories, leaving some legal and implementation uncertainties. These should be clarified in cooperation with competent authorities at the project level.

Emissions from grass biomass are generally higher than from woody biomass, particularly regarding particulate matter, requiring additional measures such as particle removal systems.

There is also a lack of detailed regulations regarding ash management. The absence of end-of-waste criteria creates legal uncertainty for its use. Good practices from other countries (e.g. Germany) demonstrate possible solutions.

According to the Environmental Protection Act (ZVO-2), waste ceases to be waste when it is properly treated and meets four key conditions: it has a clear use, there is a market or internal use, it meets technical requirements, and it poses no risk to human health or the environment.

For ash from grass biomass combustion, the first three conditions are generally met, while uncertainties remain regarding proof of safety. Although current analyses (e.g. heavy metals) indicate low risk, further research is needed.

Material use and conclusions

Analysis of biochar from grass biomass showed comparable or even better physico-chemical properties than typical grassland biochar, including high carbonization levels, good energy value (~30 MJ/kg), and low heavy metal content.

These characteristics indicate efficient thermal conversion, good soil stability, and potential for long-term CO₂ sequestration. Additional properties, such as water retention and suitable pH, confirm its suitability for soil improvement.

Grass biomass contains significant amounts of cellulose, hemicellulose, and lignin, supporting its potential for sustainable value chains.

A combination of different biomass uses appears most appropriate, with energy use remaining an important option. Efficient economics will depend on stakeholder cooperation, continued pilot testing, and the development of clear business models.

Planning must comply with EU sustainability requirements, particularly Directive (EU) 2023/2413, which defines conditions for sustainable biomass use and emission limits.

A key outcome of both Focus Lab events was the initiative to establish an expert working group to conduct an in-depth analysis of biomass use potential in Slovenia and develop economically viable business models.

JZ KPLB, as the main initiator, will coordinate further steps in establishing and operating this expert working group.

Summarized by expert Jasna Možina (JZ KPLB)