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- What is Switchgrass?
- Why this Project?
- What were the main Objectives of
this Project?
- What are the general Conclusions
of this Project?
- What are specific Conclusions
of this Project?
- Who funded this Project?
- Who participated in this
Project?
Switchgrass is a native of North America where it occurs
naturally from 55ยบ N latitude to deep into Mexico, mostly as a prairie grass. In
North America it has long been used for soil conservation and as a fodder crop.
Both in America and Europe it can be found as an ornamental plant. The grass is
also found in South America and Africa where it is used as a forage crop.
Switchgrass is a perennial C4 grass propagated by seed that can be established
at low cost and risc and requires very low inputs while giving high biomass
yields even on marginal soils. Since the early 1990s the crop has been developed
as a model herbaceous energy crop for ethanol and electricity production in the
USA and in Canada and it is also being considered as a paper pulp production
feedstock.
There is an increasing interest in Europe in biomass crops as a
source for renewable CO2-neutral energy, fuels, and chemicals and as a fibre
source for the production of paper and other renewable materials. Many different
plants are being considered for this purpose. For example trees such as willow,
eucalyptus and poplar and annual crops such as hemp. Switchgrass (Panicum
virgatum L.) is one of the perennial rhizomatous grasses being developed for the
purpose of biomass production. Since the early 1990s the crop has been developed
as a model herbaceous energy crop for ethanol and electricity production in the
USA and in Canada and it is also being considered as a paper pulp production
feedstock. In this project a broad range of factors were investigated that
determine the suitability of switchgrass as a lignocellulosic C4 biomass crop in
Europe. The most important agronomic aspects like variety choice, nitrogen
response, yield development, and establishment were evaluated together with
specific energy and fibre applications. Information from literature, from small
experiments conducted in Europe, and results from ongoing research on other
perennial rhizomatous grasses served as a starting point for the project.
The GENERAL OBJECTIVE of this project was to evaluate
switchgrass as a promising cost effective energy crop that will add to
agricultural diversification in Europe and to generate sufficient data to be
able to initiate large scale production trials and facilitate further
development of switchgrass in Europe. Specific objectives were: (1) to identify
existing switchgrass varieties that are adapted to specific geographical regions
of Europe, (2) to determinate the potential dry matter production of switchgrass
in small production plots, (3) to determine nitrogen fertiliser requirement of
switchgrass, (4) to collect physiological data on switchgrass to explain biomass
production and quality, (5) to identify best seed establishment methods
under European conditions, (6). to evaluate winter hardiness of
switchgrass under European conditions, (7). to develop a pilot model for
switchgrass biomass production, (8) to determine the suitability of switchgrass
for various thermal conversion processes (pyrolysis, gasification and
combustion, (9) to evaluate switchgrass fibre quality, (10) to evaluate economic
and environmental aspects of the use of switchgrass as an energy crop, a fibre
crop, and a combined energy/fibre crop, (11) to compare switchgrass to other
energy and fibre crops.
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Switchgrass can be grown successfully in Europe. It can be
used to produce inexpensive biomass under low input conditions and at a low
environmental impact.
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Switchgrass biomass can be used for thermal conversion to
electricity and heat. It also has potential as a fibre source for paper pulp
production where it can replace hardwood, or as a feedstock for lignocellulose
for bioethanol production. Other promising applications of switchgrass
fibre include as re-inforcing and filling agent in thermoplastic materials.
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It is necessary to gain further experience with switchgrass
under large field conditions and over a longer period of time. In addition,
switchgrass performance could increase significantly through breeding and
optimisation of agronomic parameters such as timeliness of seeding, row
spacing, nutrient requirements, etc.
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Information on applications of switchgrass for energy and
fibre uses could be expanded much further.
Are there existing varieties that are
adapted to specific geographical regions of Europe? It is possible to
find switchgrass varieties that are adapted to most regions of Europe. The
latitude of origin of a variety is the most important aspect determining the
area of adaptation of a variety. Generally the use of varieties originating at
southern latitudes (Southern USA vs Northern USA and Canada) can increase DM
yields but (in NW Europe) it will also increase the chance of establishment
failures in the first year and a decline in yields over time. Furthermore the
quality of the biomass will be reduced (high moisture and nutrient content) if
the variety does not mature in the fall. The best variety for a given latitude
or geographical area will be a compromise between yield, quality and winter
survival. From the current data on switchgrass grown in Europe it appears that
switchgrass may be grown further north than in North America. Specific
recommendations for using varieties are given in Chapter 5 and 10.
What is the potential dry matter production of switchgrass
in small production plots? In the current project yields of up to
18 tonnes dry matter/ha were found in NW Europe and up to 25 tonnes dry
matter/ha were found in Southern Europe. Under practical conditions these yields
may be lower as field plot yields are often higher than practical yields.
Accurate estimates will have to be obtained on large filed experiments over
longer periods of time. Another aspect is the time it takes for a switchgrass
stand to raech maximum yield potential. At most experimental sites yields
increased from year to year and may have increased even more in following years.
What is the nitrogen fertiliser requirement of
switchgrass? Nitrogen fertiliser requirements were generally found to be
low as the crop failed to show yield response to fertiliser applications at 4
out of 5 experimental sites. The current research shows that between 0 to 50 kg
N/ha/year is adequate for NW European sites while at higher productive sites in
southern Europe 50 to 100 kg N/ha/year should be adequate. More specific
recommendations for quantity of nutrients cannot be made because this will also
depend on the fertility status of the site.
What determines the yield and biomass quality of
switchgrass? Yield and quality of switchgrass are determined by a range
of factors of which the origin of the variety is probably the most important
(see discussion in Chapter 5).
Which seed establishment methods for European conditions are recommended?
Seed establishment makes switchgrass a very attractive biomass crop since it is
inexpensive and reduces financial risks. Experiments have shown that no-till
establishment methods are suitable for switchgrass, (see Chapter 6 for details).
Spring establishment dates and seeding rates were tesed indicating that as low
as 200 Pure live seeds per square meter can be sufficient for establishing a
good stand. Further development of establishment methods for specific regions
and soil conditions (slopes) is possible to decrease establishment risk and
cost.
Which factors determine winter survival for switchgrass
varieties? Winter survival is mainly determined by the length of the
growing season of switchgrass. If a variety fails to mature sufficiently when
winter sets in severe winterdamage to the stand will occur. This is especially
the case in the establishment year. Therefore late maturing varieties which
originate at southern latitudes should not be used at sites too far north (see
Chapter 5 for details).
For what types of thermal conversion systems is
switchgrass biomass suited. Switchgrass biomass has been tested for
thermal conversion (for details see Chapter 7). Many different factors determine
suistablity for thermal conversions. Based on the contents of alkaline metals
and chlorine, two of the most important factors determining suitability for
thermal conversion, it is expected that switchgrass biomass is better suitable
for thermal conversion than (wheat) straw and worse than wood.
For which non-energy applications can switchgras fibres be
used? Switchgrass has been evaluated for paper pulp production and as a
reinforcing fibre in polypropylene composites (for details see Chapter 8). It
was concluded that switchgrass could replace a part of the hardwood pulps in
printing and writing papers. Due to its high bulk it will especially be suitable
for bulky printing papers. Mechanical pulping of switchgrass needs far less
energy than mechanical pulping of aspen or other woods. The high productivity
under low input conditions results in low cost per tonne of biomass making
switchgrass a potentially cost effective replacement for hardwood pulps in
printing and other paper types. The low price and the relatively good mechanical
characteristics should make switchgrass an attractive fibre for filling and
stiffening in thermoplastic composites. Further improvement of composite
mechanical properties by improved pulping should be possible. The potential
ethanol production yield when switchgrass is used as feedstock in a
lignocellulose to ethanol system was calculated to be 262 kg ethanol/tonne dry
matter. This yield is comparable to the theoretical ethanol yield from hard wood
like willow.
Which conclusions can be drawn from economical and
ecological analysis of switchgrass production and utilisation? The data
was limited to 3 years while the typical (economic) life span of a switchgrass
stand is expected to be 10 to 15 years. Furthermore only small plot experimental
data was available. Based on extrapolation of this data and available literature
some conclusions can be drawn. The cost prices for switchgrass for the different
countries mentioned above varied between 24 and 62 Euro per tonne DM. Not taking
into account the land costs. In general environmental parameters that affect
Miscanthus are similar to those mentioned for switchgrass. With Miscanthus
requiring more input in establishment than switchgrass because Miscanthus is
propagated by rhizomes and switchgrass by seed. In order to make better
comparisons in the future there is need for scaling up production field trials
to determine actual commercial biomass yields and costs for switchgrass and
other perennial grasses like Miscanthus.
This research has been partially funded by the European
Community (DGVI) under the FAIR program (FAIR 5-CT97-3701) and by ETSU, UK. The
information contained on this website does not necessarily reflect the European
Commissions views or anticipate in any way its future policy in this area.
A number of research organisations from
different EU countries participated in this research project. Please turn to the
contact persons section of
this website for more details.
Wolter Elbersen, Rob Bakker, Wageningen UR,
Agrotechnology & Food Innovations bv, the
Netherlands.
Revised: 01/10/03.
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