Paludiculture: peat formation and renewable resources from rewetted peatlands
by Wendelin Wichtmann & Hans Joosten
The last years have shown a worldwide increasing
demand for biomass. Next to the need for food to
satisfy the growing population and prosperity in
newly industrializing countries, the markets for
biogenic raw materials and biofuels are rapidly
expanding. On arable lands the cultivation of industry
and energy crops increasingly competes with
conventional food production. The shortage of
biomass can be observed in rising prices and in the
renewed interest to exploit unused land resources,
including unreclaimed lands (wilderness), abandoned
fields, and low productive areas. This trend creates a
new focus on peatlands, such as in the tropics where
oil palm and pulp plantations are expanding
The critical condition of mires in climatic regions that
are well-suited for crop cultivation (cf. the near
extinction of tropical peat domes and of percolation
mires in the temperate zone) necessitates a complete
ban of biomass cultivation on peatlands that have
remained largely untouched. Not only important
biodiversity values are at stake there, but biomass
production associated with peatland drainage is
highly counterproductive from a climate point of
view (see contribution of John Couwenberg in this
Newsletter). The credo with respect to (near-)natural
mires should be: “no new structures, no further
In the temperate zone, peatlands had just lost their
agricultural attractiveness. Difficult handling, low
productivity and progressive degradation under
intensive use prevented them to effectively compete
with the abundant and increasingly productive
mineral soils. In fact, immense areas of agriculturally
used peatland in Europe had been abandoned in the
last decade. Now the expansion of biomass
cultivation again throws an eye on these areas. We
increasingly observe in West-and Central Europe new
deep drainage of peatlands to enable cultivation of
‘renewable biofuel’ crops like maize (Zea mays) and
elephant grass (Miscanthus).
However, the quest for additional land resources for
biomass production can also work out positively for
peatland and climate conservation if it is combined
with the rewetting of drained peatlands. Drainage
(with associated subsidence and soil deterioration)
has largely degraded the agricultural value of their
soils, they have lost most of their biodiversity values,
and they belong globally to the largest greenhouse
gas emitters in existence. So, there is little to lose and
a lot to be gained. Rewetting drained peatlands will
substantially reduce the emission of greenhouse gases
(especially CO2 and N2O, Joosten & Augustin 2006).
It can additionally contribute to avoiding carbon
dioxide emissions when the rewetted peatlands are
used for the production of biomass to replace fossil
raw materials and fossil fuels.
This innovative alternative to drainage-based
peatland agri- and silviculture is called
‘paludiculture’: the sustainable production of
biomass on rewetted peatlands. In this paper we
present a short overview of our experiences with
paludiculture in Central Europe.
Paludiculture is the cultivation of biomass on wet and
rewetted peatlands. Ideally the peatlands should be so
wet that steady (long-term) peat accumulation is
maintained or re-installed. The basic principle of
paludiculture is to use only that part of net primary
production (NPP) that is not necessary for peat
formation (which is ca. 80-90% of NPP). In the
temperate, subtropical and tropical zones of the
world, i.e. those zones where high production is
possible, most mires by nature hold a vegetation of
which the aboveground parts can be harvested
without harming the peat sequestering capability. In
those areas natural peatlands are largely dominated
by cyperaceae, grasses, and trees, i.e. growth forms
that realize peat accumulation belowground by
ingrowing rootlets, roots, and rhizomes (‘replacement
peat’, Prager et al. 2006).
The quintessence of paludiculture is to cultivate plant
1. thrive under wet conditions,
2. produce biomass of sufficient quantity and quality,
3. contribute to peat formation.
With respect to the first criterion, it is interesting to
notice that almost all agriculture focuses on drylands
on which substantial tillage is applied. Peatland
agriculture simply replicates this mode of operation,
although draining and tilling is the most effective
way to enhance peat oxidation and to destroy the
peatland subsistence base. (The exception on the rule
is wet-rice, which provides more than one fifth of the
calories of the human global diet.)
Peat formation can be assessed by constructing
complete carbon balances over long periods (cf.
Roulet et al. 2007). As this is a complicated and
laborious job, the peat forming capability of specific
species is generally deduced from peat composition
(Succow & Joosten 2001). Macrofossil analysis
shows that peats may contain macro-remains of a
large diversity of plant species, but that only a limited
number of these species contribute substantially to
the bulk of peat accumulation. Much more species
will probably add to the unrecognizable humus
component of peat but organic geochemical research
into this aspect of peat formation is still in its infancy.
The plant biomass that can be cultivated after
rewetting is of varied quality and allows for
differentiated uses (Wichtmann et al. 2000).
IMCG NEWSLETTER 25
Successional plant-communities: The rewetting of
degraded fen peatlands often initiates luxurious
vegetation development. Depending on trophic state,
water regime, seed bank and other site conditions,
reed beds of Phalaris arundinacea,Glyceria maxima,
Phragmites, or Typha and more rarely sedges, but
also Salix cinerea scrubs establish. The selective
cultivation of site-adapted species (Cattail, Sedges,
Common Reed, Alder) can provide higher harvest
security than the utilisation of wild succession
communities (Wichtmann & Schäfer in press).
Table 1:Productivity of selected reeds and wetlands (after
Dominant species Productivity
t DW haí1 aí1
Common Reed (Phragmites australis) 3.6 - 43.5
Cattail (Typha latifolia) 4.8 - 22.1
Reed Canary Grass (Phalaris arundinacea) 3.5 - 22.5
Sweet Reedgrass (Glyceria maxima) 4.0 - 14.9
Lesser Pond-sedge (Carex acutiformis) 5.4 - 7.6
Great Pond-sedge (Carex riparia) 3.3 - 12.0
Fallow wet grassland
6.4 - 7.4
8.8 - 10.4
Reed (Phragmites australis) has a high potential for
biomass production (Table 1). After rewetting of
intensively used peatlands it develops by spontaneous
succession or can be established artificially
(Timmermann 1999). Even at planting densities of
less than one plant per square metre, it rapidly forms
closed beds (Timmermann 1999). Its ecotypes
display genetically fixed differences in habitat
demands and productivity (Kühl et al. 1997), which
through selection can guarantee high productivity. A
sustained harvest of 15 t · haí1 dry matter can be
achieved in combination with continuing peat
accumulation (Wichtmann 1999a).
Reed can be utilised both as an energy source and as
an industrial raw material. Traditionally harvest for
roofing material (fig. 1) takes place in winter.
Cultivation and application has been described by
Rodewald-Rudescu (1974), Wichtmann (1999b), and
Wichtmann et al. (2000).
Cattail (Typha latifolia, T. angustifolia) cultivation
may lead to dry-matter harvests of up to 40 t · haí1
(Wild et al. 2001). The industrial uses of cattail range
from insulating materials to lightweight construction
boards. The optimum water levels for cattail reed-
beds are 20 to 150 cm above the surface. Unlike
Common Reed, the cattails can germinate during
submergence, but fail to form peat. Whether it is
possible to establish permanent cattail stands by
means of planting has to be investigated in
Figure 1: Cultivation of thatching reed on fen peatland
in Roswarowo, Poland
Sedges can also be utilised both energetically and
industrially. Experiments in Northeastern Germany
resulted in a successful establishment of Carex
gracilis,C. acutiformis,C. paniculata,C. elata and
C. riparia (Roth 2000). A dry-matter production of
up to 12 t · haí1 can be expected (Table 1).
Alder (Alnus glutinosa) produces a valuable wood
that, beside as a fuel, is suitable for veneer, carpentry,
and the production of high-quality massive wood
furniture (Kropf 1985). An alder forest of average
productivity yields after 70 years about 550 solid
cubic metres of wood per ha (Lockow 1994). The
crucial factor for alder forestry is a water regime just
under the surface which enables a commercial wood
harvest combined with peat formation and a positive
climate impact (Schäfer & Joosten 2005, table 2).
Table 2:The effect on global warming potential of afforesting rewetted fens with black alder (Alnus
glutinosa) (after Schäfer & Joosten 2005)
Global Warming Potential (GWP: CO2 equivalents, kg ha-1 a-1)
Water level N2O CH4
(wood formation) 1 GWP total
5 cm over surface
10 cm under surface
1 negative numbers denote net uptake into the soil or wood and positive climate impact
Figure 2: Alder cultivation on fen peatland in NE
Reed canary grass (Phalaris arundinacea) dominated
stands developed by natural succession over large
areas in restoration projects in NE Germany, where
insufficient water was available for complete
rewetting. Under such humid to wet conditions peat
oxidation is retarded substantially or stopped
completely. Unlike normal agricultural use, harvest
can be done in winter as lower S, Cl, K
concentrations improve the combustion properties
(Mortensen 1998, Burvall & Hedman 1998).
Peatmoss (Sphagnum spp.) can be cultivated on
rewetted cutover peatlands and on agriculturally used
bog grasslands after rewetting. The product can
replace fossil peat in horticulture (Gaudig & Joosten
2002, Gaudig et al. 2007)
Figure 3: Experimental Sphagnum cultivation plot in
Biomass from rewetted peatlands (BRP) can be used
as an energy source in direct combustion, in biogas
plants, and for the production of liquid ‘sun fuels’.
Energy recovery from BRP depends on the site
conditions, especially on the hydrologic and trophic
situation. Because of lack of data, the combustion
suitability of BRP is often compared with that of
cereals and Miscanthus that have been cultivated on
mineral soils with heavy fertilization. These have
much higher ash contents, lower ash melting
temperatures and higher sulphur and chloride
concentrations in their exhaust fumes compared to
wood, which may cause slagging and corrosion in the
co-generation power plants. Biomass from peat soils,
however, normally has much lower contents of these
Comparison of Common Reed (from near brackish
water), Reed Canary Gras (from mineral soil) and
spruce wood (including bark) (table 3) shows that the
carbon content of these biofuels is comparable. The
ash content of the former two is about 10 times
higher than that of wood, probably because of the
mineral soil and near-brackish origin of these crops.
Table 3:Combustion related properties of different biomass crops. Values in % dry weight
(after Eder et al. 2004, Hartmann et al. 2003, Kastberg & Burvall 1998)
Common Reed Reed Canary Grass Spruce wood
Carbon content 46 – 47 45,4 49,8
Sulfur content 0.04 – 0.05 0.1 0.015
Nitrogen content 0.24 – 0.30 0.62 0.13
Chlorine content 0.2 0.05 0.005
Ash content 5.12 8.0 0.6
Min. heating value MJ/kg 17.5 16.9 19,5
IMCG NEWSLETTER 27
The ash melting temperature of the investigated
Common Reed (1420 °C) is higher than the value for
wood and Reed Canary Grass indicating that – in
contrast to other grasses and cereals – combustion
does not lead to technical problems (Eder et al. 2004,
Hofbauer et al. 2001).
If the harvested biomass is intended for energy
production the harvesting machines may be less
sophisticated and expensive than those for the
production of quality reed for roofing or other
industrial purposes (Wichtmann 1999b). Transport,
for instance, can proceed in big bales. Biomass-to-
liquid (BTL) plants, for example require unspecific
biomass with high carbon and low water contents
(less than 35 % of water). These requirements are
easily met by Reed Canary Grass and Common Reed
harvested in winter.
Depending on the price of energy the exploitation of
less productive stands becomes feasible, especially
when the climatic and other benefits are taken into
account and adequately remunerated.
An assessment for Northern Germany showed that
out of a total of 830,000 hectares of fen peatlands a
quarter could be managed for BRP-production
(Wichtmann 2003, Wichtmann & Schäfer 2005).
With yields of 10 tonnes per hectare and year, about
20 Million tonnes dry biomass would be available,
corresponding to the demand of 20 biomass-
combustion plants with 20 MW-capacity each (cf
Thrän & Kaltschmitt 2001).
Paludicultures will also harbor species that are not
directly aimed for. In normal agriculture such species
are called ‘weeds’ or ‘vermin’. In paludicultures
these will also include species that have become rare
and endangered because of the massive decline of
their natural wet-humid habitats. The re-
establishment of mire and mire-like conditions after
rewetting will provide new habitats for these species,
whereas biomass harvesting keeps the sites in a
suitable succession stage. A nice example is the
conservation of the globally threatened Aquatic
Warbler (Acrocephalus paludicola) in successfully
commercially used reedlands in Western-Poland (fig.
1, Tegetmeyer et al. 2007). In Sphagnum cultivation
plots we find interesting ‘weeds’ like Drosera and
other bogs plants.
From the viewpoint of species and habitat
conservation a rewetting of degraded peatlands and a
subsequent use for biomass cultivation generally is to
be preferred over keeping the areas in a drained and
Next to the global climatic benefits from rewetting
and the production of raw materials for industrial and
energy use, paludicultures have several additional
An improvement of regional landscape hydrology
because water is kept longer in the landscape
A mitigation of regional climatic change by
providing additional evapotranspiration cooling
The restoration of habitats for rare mire species and
A reduction of nutrient run-off (e.g. nitrogen) into
The prevention of peatland fires (very important in
the Chernobyl region where fires lead to re-
emission of radio-active substances)
The establishment of new land-use concepts with
minimal damage to the environment
A revitalisation of rural economies by combining
traditional land use with new ways of processing
The conservation of an open cultural landscape
An improved economic basis through (eco)tourism,
as paludicultures are generally more attractive than
An increase in energy political autarchy by local
Monetarisation of these values would significantly
enlarge the visibility of the economic benefits of
There are 80 million hectares of drained peatlands
worldwide that heavily contribute to the greenhouse
effect. Rewetting these peatlands will substantially
reduce global anthropogenic greenhouse gas
emissions. Additionally, this rewetting can contribute
to avoiding emissions by producing biomass for
industrial use and for the generation of energy. Given
a continuing rise in prices, the utilisation of biomass
is becoming more and more attractive and rewetted
peatlands may become as valuable as highly
productive arable lands. It is therefore advisable to
rewet as much peatland as possible, wherever the
hydrological conditions permit it.
Paludicultures are still in their infancy because agri-,
horti-, and silviculture have traditionally focused on
drained sites. Priority is to identify for every climatic
zone species suited for paludiculture and variants and
clones for optimal cultivation.
Paludicultures may be ideal as hydrological buffer
zones around pristine peatlands which themselves
should be strictly preserved wherever they have
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Wendelin Wichtmann: firstname.lastname@example.org
Hans Joosten: email@example.com