Sustainable production and utilisation of cattail on fen sites in Lower Saxony

Background and Objective

The majority of the peatlands in Germany is drained for agriculture and forestry and thus responsible for a large share of the greenhouse gas (GHG) emissions from agriculturally used land. One option to reduce emissions is paludiculture, i.e., agriculture or forestry on rewetted peatlands. Ideally, re-wetting of currently drained peatlands with subsequent paludicultural use conserves the peat, but value chains are so far underdeveloped.

The project RoNNi is coordinated by the 3N Competence Centre Renewable Resources. The aim of the project is the transformation of drained agriculturally used fen soils to a climate friendly peat soil conserving wet cultivation by growing cattail. Therefore, in two model regions with different agricultural structures (Emsland and Cuxhaven) the large-scale quality-optimised production of cattail (Typha angustifolia and Typha latifolia) and the utilisation of the biomass as construction material and horticultural substrate (peat substitute) will be developed, demonstrated and prepared for commercialization.

The partial project of the Thünen-Institute addresses the greenhouse gas exchange and the water balance of the cattail paludiculture sites and of reference sites under intensive agricultural use. Therefore, we will provide insights on the mitigation of greenhouse gas emissions by paludicultures as well as on their water demand.

RoNNi is one of nine large projects of the PaludiNetz, which are funded either by the German Federal Ministry of Food and Agriculture or the German Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection. The goal of the projects is to grow paludicultures at a regular agricultural scale and to establish utilization chains.

Different paludiculture options are implemented: Sphagnum farming as an alternative to peat as growing media as well as wet grasslands, cattail and reed for building and insulation materials, paper and packages, and other uses. The implementation of all projects goes along with a scientific evaluation of the ecological and economic effects of paludiculture. The PaludiZentrale as part of the PaludiNet is responsible for overarching coordination and networking as well as for the harmonization of the methods and synthesis studies.

Approach

In our subproject of the project RoNNi, we aim at quantifying the greenhouse gas (GHG) balance for two cattail paludicultures and two reference sites for 7 years. For carbon dioxide and methane, we use the eddy-covariance method. Nitrous oxide and methane fluxes at the drained reference site will be measured manually with chambers.

Further, environmental parameters such as the peat water level and the nutrient contents of the peat as well as changes in surface heights are measured. As this is the first time to measure greenhouse gas exchange at cattail paludicultures using the eddy covariance method, results will not only quantify the mitigation potential, but also help to improve our understanding of the much discussed CH₄ emissions of cattail paludicultures.

Above-ground components of the water balance, i.e., the inflow and the discharge from the cattail sites, are measured, while groundwater inflow is determined by geohydrological modelling. Results will inform about the water demand of cattail paludicultures and will be used to calculate input and export of dissolved substances such as nutrients or dissolved organic carbon.