Rehy­dra­tion of peaty soils – a gain for the farm?

For a long time, farmers across Europe have drained marsh­land to create arable land. But in the context of climate change, experts are concerned about the results of these efforts: Around half of the marsh­lands on the conti­nent are consid­ered damaged due to peat extrac­tion and dehy­dra­tion by the agri­cul­tural and forestry sector.

Given the climate crisis, opin­ions on marsh­lands are changing: Dehy­drated organic soils emit green­house gasses into the atmos­phere; approx­i­mately 220m tonnes of CO₂ equiv­a­lent every year in the EU alone. This means they are respon­sible for about 5% of total emis­sions. In contrast, undis­turbed marsh­lands store carbon.

However, so far only about half of EU member states have enshrined protec­tion of marsh­lands. And only a handful are offering support programmes to restore it. Germany’s Nationale Moorschutzs­trategie (National Strategy for the Protec­tion of Marsh­lands) is one of them.

How does marsh­land protect the climate?

Marsh­lands act as carbon sinks because of their high water levels. These ensure that there is hardly any oxygen in the soil and that dead plant mate­rial is not degraded by aerobic micro-organ­isms with resulting CO₂ emis­sions. Instead, the organic mate­rial is laid down and peat is created.

If marsh­land is dried out, oxygen enters the soil. Aerobic micro-organ­isms start to deplete the stores of organic mate­rials. As a result, carbon and nitrogen escape into the atmos­phere as climate-damaging CO₂ and N₂O (nitrous oxide). There­fore, climate activists are calling to protect intact marsh­land and restore damaged peat to create a long-term carbon sink. Dr Sabine Wich­mann of the Univer­sity of Greif­swald states: “The rehy­dra­tion of marsh­land offers a signif­i­cant oppor­tu­nity to do a lot on a very small foot­print.” She has been researching palu­di­cul­tures (plants that can tolerate high ground water levels) at the chair for General Economics and Land­scape Economics for years.

Creating value in marsh­lands – is that even possible?

So far, marsh­land had been consid­ered as mostly unus­able by farmers. The high water levels, from 0 to 10cm above the water table means that commonly-used methods of cultivation are pushed to their limits. This applies both to the crops that can be culti­vated here as well as the tech­nology used to achieve this. There are few farmers who would inde­pen­dently choose to rehy­drate their marsh­land to protect the climate.

Economic incen­tives are needed: Funding and added value via palu­di­cul­tures. In accor­dance with polit­ical goals, palu­di­cul­tures have been funded since 2023 as part of the EU’s Common Agri­cul­tural Policy. This makes it more inter­esting for farmers to think culti­vating peat­land.

Whoever wishes to culti­vate palu­di­cul­tures has to know the loca­tion well. Just like any other crop, palu­di­cul­tures have their own require­ments, for example, water avail­ability and nutrient contents. Bull­rush is partic­u­larly sensi­tive if the water level is too low, but wet grass­lands cope well with this. Common reed is depen­dent on changing water levels and requires ‘dry feet’, partic­u­larly in early summer. Peat moss only grows on acidic, nutrient-poor raised bog soils. However, nutrient-rich loca­tions are suit­able for reeds and bull­rushes.

Util­i­sa­tion of peat biomass

The most commonly culti­vated type of marsh­land is wet grass­land. However, usually the vege­ta­tion is mulched or cleared to ensure a minimal amount of cultivation and to receive the funding. In most cases, the feed value is too poor for further use. But the biomass could be used further, for example, to generate energy. The thermal power plant Malchin has been using low moor biomass since 2014 to generate local heat. However, most biogas plants still do not have the appro­priate tech­nology to use stalk mate­rial-based biomass.

According to Sabine, other uses are more inter­esting, for example, as medica­tion, insu­la­tion mate­rial, as a wood substi­tute, as substrate for agri­cul­tural use or for paper and card­board. Peat Moss, bull­rushes, reeds, willows or medi­c­inal plants like sundew show poten­tial for this purpose.

The first compa­nies are now turning peaty biomass into furni­ture compo­nents and insu­la­tion mate­rial. Zelfo, based in Schwedt, has devel­oped boards made from natural fibres obtained from palu­di­cul­tures to build furni­ture. In Lower Saxony, the peat plant Moorkultur Ramsloh uses peat moss grown on previous raised bog grass­lands in its substrates. Bull­rushes are used for building insu­la­tion boards by Typhat­e­chnik. Reeds, however, are not only used to cover roofs by the market leader Hiss Reet, for example, but also as acoustic room sound­proofing, para­sols and drinking straws.

Cultures with poten­tial

It remains to be seen whether the effort that goes into the cultivation of palu­di­cul­tures is worth it, both for the envi­ron­ment and finan­cially for the indi­vidual compa­nies. There is no clear-cut answer for this, as Sabine found out in her disser­ta­tion (2021). She inves­ti­gated the prof­itability of the most common palu­di­cul­tures. Some appeared quite promising, depending on the type of use.

For example, wet grass­land requires less of an upfront invest­ment, the water manage­ment is less complex and specialist cultivation tech­nology already exists. This is not the case for many other palu­di­cul­tures. The researcher assumes that wet grass­land will there­fore still make up the majority of rehy­drated land in the future.

Peat moss for orchid growing are currently obtained from Chile or New Zealand but they could also be manu­fac­tured in Germany. If the process can be opti­mised to produce good yields, this could be econom­i­cally viable. However, at current prices, replacing peat is currently not possible. Dr Wichman explains: “Peat is just too cheap.” Peat moss are only grown on approx­i­mately 25ha across Germany. It would need to be grown on 35,000ha to completely replace white peat with peat moss in horti­cul­tural substrates.

Native species for palu­di­cul­ture

Reed, used as a roof covering, is already econom­i­cally viable. “Prices have doubled over the past few years.” The local thatch market requires approx­i­mately 10,000ha – and German land only covers 1,000ha of this – a drop in the ocean, according to reed roofer and reed processor Ralf Betge.

When it comes to using reed in biomass boilers, the picture is slightly more nuanced than this: Here, the economic viability depends on whether it is possible to obtain agri­cul­ture funding for the reed stands, as well as machine util­i­sa­tion rate and yields.

Apart from estab­lished crops, other local species can also be devel­oped into palu­di­cul­tures. Some candi­dates are even suit­able for human consump­tion: Wild rice, cran­ber­ries and manna­grass, to name a few. The GMC has estab­lished a data­base of poten­tial palu­di­cul­tures. It contains hundreds of typical marsh­land plants and humidity-tolerant crops which were analysed for their poten­tial use.

Invest­ments neces­sary

Farmers who want to start growing palu­di­cul­tures have a chal­lenge in that there are no estab­lished markets for most of the crops. Further­more, they also require invest­ment: Into the rehy­dra­tion, the tech­nology and the further processing. “But if this conver­sion could be subsidised, there would be so many situ­a­tions in which palu­di­cul­tures would be viable and a real alter­na­tive to just giving up working the land,” says Sabine.

Those who wish to start rehy­drating their marsh­lands and are looking for expert advice can contact their Water and Soil Asso­ci­a­tions. These are estab­lished struc­tures respon­sible for water manage­ment in agri­cul­ture and should mediate between the different inter­ested parties. Sabine also advises farmers to explain the need for infor­ma­tion, so that agri­cul­tural advisers can get to grips with the issues of rehy­dra­tion and palu­di­cul­tures.

Ralf Betge stores the reed bundles in the newly-built shed so that they can be further processed later.

Ralf pulls each bunch by hand through a comb to remove grass and short stalks. This ‘’combing’ prevents imma­ture and short stalks from later drawing water onto the roof and trick­ling out.

The result is a clean reed bundle. Ralf does not know of any machines that achieve this high level of hand cleaning quality.

Ralf Betge ties the care­fully cleaned reed stalks together into bundles of equal size.

Reed made in Germany

Reed is a tradi­tional palu­di­cul­ture in Germany. Ralf Betge from Benz, on the island of Usedom, is a master of the old trade of reed harvesting, processing and thatching. The qual­i­fied agri­cul­tural machine fitter learnt the trade from his father. Until very recently, he processed about 20,000 bundles of reed on approx­i­mately 20ha. He is currently restruc­turing the company and in the 2023/2024 season, provided every­thing goes well, he wants to grow reeds about 70ha.

In the future, he wants to focus on the processing and leave the thatching to others. He wants to “supply local mate­rials for local roofs”. “That is what our trade stands for.” For this purpose, he built a new storage facility and leased addi­tional land.

The landowner had previ­ously culti­vated this land as wet grass­land. “They were pretty fed up of these areas because they had to keep on mowing them,” says Ralf. It is a real relief for the owner that the reed specialist now mows these areas for them. The reed belts are already consid­ered agri­cul­tural areas, which means Ralf does not need to bother with an appli­ca­tion for cultivation with the Envi­ron­mental Protec­tion Office. Further­more, he also doesn’t need to prepare the areas labo­ri­ously. If a reed belt is being used for the first time or is not harvested for one season, it must first be mowed and mulched to get rid off stalks from previous years, delaying the produc­tive harvest by a year.

How reed cultivation works

As soon as the reed has dried and matured, harvest can start. Until the 1990s, Ralf used a scythe to harvest it. Then he built himself a harvesting machine. To speed things up, he purchased a new harvester in 2017, but the machine was too heavy, and the ground pres­sure too high. Now he wants to construct a new harvester himself, along­side an auto­matic processing belt, similar to the ‘Minifix riet bind­ma­chine’ by the Dutch mechan­ical engi­neer Ale Stoker.

Until now, each bundle is ‘combed by hand, which means it is pulled through a comb to remove grasses and short stalks. This is far too slow and expen­sive for smaller compa­nies. Due to climate change, the optimal harvest time has shifted from December towards the end of the winter, and then Ralf has to work quickly because he is only allowed to harvest until February 28.