Paludicultures for fen soils in Bavaria - establishment, climate relevance & environmental effects, utilization possibilities and economic efficiency (MOORuse).

Agricultural drainage and intensification has led to peatlands in Europe becoming "hot spots" for greenhouse gas emissions. In this context, conventional peatland use contributes about 4.9% of total national emissions. In addition to the emission of climate-damaging gases, the drainage and agricultural use of peatlands leads to the loss of site-typical biodiversity, the loss of the water retention function, and the pollution of groundwater and surface water.

Numerous research projects have shown that the rewetting and extensification of degraded peatlands is the only efficient measure for permanent climate and species protection. Since this is often accompanied by a restriction of use or abandonment of the areas, there is mostly only a low acceptance among landowners to implement renaturation measures. In contrast to the classic renaturation of peatlands, paludiculture offers alternative uses that are gentle on the peatlands and adapted to the location, which are combined with partial or complete rewetting. In addition to the production of Renewable Resources, natural ecosystem functions can be restored. In addition, it is assumed that paludiculture can lead to a significant reduction in greenhouse gas emissions due to the naturally high groundwater levels and thus contribute significantly to climate protection.

Managed peatlands are the largest sources of carbon in the landscape. Complete renaturation would be most beneficial for climate, biodiversity and water retention. However, this comes at the expense of utilization requirements and is therefore not feasible across the board.

Overarching question

• . How can we reduce the environmental impacts of current management and still develop productive wet use on peatlands?

Subquestions

• Establishment: which methods are suitable for establishment and how good is it to bring paludiculture (wet management) into operational use on the land?
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• Environmental impacts: How do different paludicultures at different water levels affect climate relevance and biodiversity?
• Reutilization: What are the material or thermal utilization possibilities of different paludicultures?
• Can paludiculture be integrated into Agriculture in an economically viable way? What regional value chains are possible?
• Can the results obtained be transferred to other locations?

The aim of the research project is to develop new sustainable uses for fens that take into account and promote ecological functions (biodiversity, water balance regulation, etc.), prevent the progressive mineralization of the existing peat body (largely climate-neutral greenhouse gas balance), are economically viable and can be integrated into regional value chains. The project is divided into four main modules, each of which addresses different sub-questions.

A major focus of the research project is the development of a guideline for the successful establishment of cattails, reeds, reed canary grass and various tall sedges. Since, from an economic point of view, only seeding is likely to be suitable for large-scale establishment, seed collection from autochthonous planting material in the Freisinger Moos will be tested in addition to various seed strengths. Since some species are known to reproduce poorly generatively, vegetative propagation and establishment by planting will also be tested in parallel and examined with regard to their economic viability. As with the seed variant, different planting associations will also be tested for planting. In addition, the influence of the groundwater level on the establishment success as well as the biomass development will be investigated. The establishment trials will be carried out exclusively in the Freisinger Moos test area. Based on the results obtained, the best establishment strategies depending on the plant species will be transferred to the two other test areas (Swabian and Bavarian Danube Moss) in order to establish large-scale demonstration plots there on an Agriculture scale.

In Freisinger Moos, four different paludiculture plants (cattail, common reed, reed canary grass, tall sedges) are investigated with respect to their climate effectiveness along a water level gradient in large-scale sheet pile basins on a previously intensively managed grassland. For this purpose, fluxes of CO₂, CH₄, and N₂O are recorded at 2 - 4 day intervals using an automated measuring device and greenhouse gas balances as well as carbon balances are calculated by empirical modeling.

The overall carbon balance thereby provides information on whether the corresponding paludiculture or peatland body is losing net carbon, is neutral, or possibly even represents a sink. In contrast to the C-balance, the greenhouse gas balance provides information on the extent to which the system has a climate-warming, climate-neutral or even climate-cooling effect. Due to a very precise groundwater control and the automated measurement technique, it is expected that already existing trace gas exchange models can be substantially improved and thus a significant reduction in model uncertainties can be achieved. The optimized trace gas models will subsequently be validated in the Donaumoos test areas.

In addition to the climate impact, the change in biodiversity will also be investigated in Module 2. The aim is to make the nature conservation value of the change in use assessable in terms of floristic and faunistic biodiversity. For this purpose, regular vegetation surveys will be carried out and similarities and differences in vegetation development and their controlling factors in the different variants will be identified on the basis of environmental variables (e.g. water level, peat thickness, nutrient supply, etc.) using classification, ordination methods and cluster analyses. In addition, for the assessment of the effects on faunistic biodiversity, territorial mapping of avifauna as well as of grasshoppers will be carried out.

In addition to testing classic recovery routes (incineration or biogas), new, innovative recovery options (e.g. peat substitutes, insulation, biogenic polymers) for the resulting biomass are also being tested or developed.

Thermal utilization

Fuel analysis will be performed on different pellet fuels as well as chaff batches produced from the paludiculture biomass. Firing tests will be used to investigate efficiency, ash properties (including agglomeration, caking, residual carbon), limited and unlimited flue gas components (CO, C_org, NO_x, O₂, SO₂, HCl, CH₄, and dust), and the need for secondary flue gas treatment.

Biogas utilization

Key parameters to assess the suitability of a substrate for use in a biogas plant are the specific biogas or methane yield (LN/kg oTM) and the biogas or methane yield per area (m³/ha). In the sub-module, the specific biogas and methane yields of different paludiculture species are determined as a function of cutting time and different substrate treatments, and experiments are conducted on the long-term behavior and process stability of the specific gas yields and qualities of the individual paludicultures.

Peat substitutes

To determine the suitability of harvested paludiculture as a peat substitute, different treatment processes (mechanical treatment by shredding, composting of the shredded and defibered chaff, charring of the shredded chaff by hydrothermal carbonization (HTC) and by pyrolysis are compared. Both untreated chaff (primary utilization) and solid residues from biogas production (cascade utilization) are assumed.

Biogenic polymers

The aim of this part of the project is to develop a natural fiber composite material with Typha and sedge fibers. For this purpose, raw fibers are prepared by targeted grinding to such an extent that they are suitable for compounding with bioplastics. A granulate produced from this should allow continuous extrusion as a strand and injection molding into molded parts.

Insulation and construction materials

In the sub-module, the leaf mass of the bulrush is used to produce insulating panels that can additionally perform static functions. Different organic adhesives will be tested with regard to their effect on thermal conductivity, building physics parameters, and fire protection and acoustic properties.

The aim of using paludiculture is to restore the ecological services of natural peatlands as far as possible while maintaining the agricultural production function of former drained peatland sites. The evaluation of the economic viability of the use of the four paludicultures studied in the project will therefore be guided by the"restoration cost method". In addition, the non-use values - but also non-monetizable consequences of the restoration of peatlands by means of the studied paludicultures - have to be surveyed at the level of the individual farm. To this end, this module will first examine the potential uses of all four paludiculture plant species worked on in the project in terms of their individual farm economics.

In doing so, it will first be analyzed for the study sites which crops would be taken out of production from the previous use by paludiculture and which monetarily assessable income changes would be associated with this. However, new income contributions from paludiculture can be obtained as full or partial compensation. Here, we need to clarify which of the four paludiculture crops studied can serve as full or partial substitutes for crops previously grown on the same sites, and what impacts on income contributions from agriculture can be derived for each site.

If none of the four paludiculture crops investigated can be considered as a substitute in the previous farm organization for individual previous uses of peatland sites, the question must be clarified as to which investments/farm conversions would be necessary so that the best possible paludiculture in terms of its income contribution site-specifically could be used for a new farm orientation. Furthermore, it is necessary to quantify the economic impacts by means of suitable welfare measures. For this purpose, economic evaluations of ecological services provided by paludiculture as well as conventional land management are carried out. Subsequently, the obtained results of the individual test plots will be examined for their transferability and regional options for action will be estimated.