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The energy potential of straw

October 23, 2013, Leipzig, Germany - Straw from agriculture could play an important role in the future energy mix for Germany. Up until now it has been underutilized as a biomass residue and waste material.


October 23, 2013
By Helmholtz Centre for Environmental Research

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October 23, 2013, Leipzig, Germany – Straw from agriculture
could play an important role in the future energy mix for Germany. Up until now
it has been underutilized as a biomass residue and waste material. These were
the conclusions of a study conducted by the TLL (Thueringian regional institute
for agriculture), the DBFZ (German biomass research center) and the Helmholtz
Center for Environmental Research (UFZ). According to them, from a total of 30
million tons of cereal straw produced annually in Germany, between 8 and 13
million tons of it could be used sustainably for energy or fuel production.
This potential could for example provide 1.7 to 2.8 million average households
with electricity and at the same time 2.8 to 4.5 million households with
heating. These results highlight the potential contribution of straw to
renewable sources of energy, scientists state in the peer-reviewed scientific
journal Applied Energy.

For their respective study, scientists analyzed the
development of residual substances resulting from German agriculture.
Accounting for 58 per cent, straw can be regarded as the most important
resource, and yet so far it has hardly been used for energy production. From
1950 to 2000 there was a noticeable rise in the cultivation of winter wheat,
rye and winter barley in Germany, which then remained relatively constant. To
remove any bias from weather fluctuations, the average values were taken from
1999, 2003 and 2007. On average, approx. 30 megatons of cereal straw per year
were produced in these years. Due to the fact that not all parts of the straw
can be used and the fact that straw also plays an important role as bedding in
livestock farming, only about half of these 30 megatons are actually available in
the end.

Sustainable use

It must be taken into consideration that cereal straw plays
an important role in the humus balance of soils. For this reason some of the
straw must be left scattered on the agricultural land to prevent nutrients from
being permanently extracted from the soil. To calculate the humus balance of
soils, the team of scientists tested three different methods of calculation.
Depending upon the method of calculation used, 8, 10 or 13 megatons of straw
can be used sustainably every year for energy production – i.e. without causing
any disadvantages to the soils or other forms of utilization. "To our
knowledge this is the first time that a study like this has been conducted for
an EU country, demonstrating the potential of straw for a truly sustainable
energy use, while taking into account the humus balance", stresses Prof.
Daniela Thraen, scientist at the DBFZ and the UFZ.

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Greenhouse gas
balances depend on utilization forms

It can thus be said that straw can contribute to the future
energy mix. The degree to which it will contribute to greenhouse gas reduction
however will depend on how the straw is used. A reduction compared to fossil
fuels can be somewhere between 73 and 92 percent when using straw for the
generation of heat, combined heat and power generation or as second-generation
biofuel production. The different greenhouse gas balances cast a differentiated
light on the EU´s goal of covering ten percent of transportation sector's
energy use by using biofuels. Once again the study emphasizes how the use of
bioenergy needs to take into account various factors. Given the conditions
prevalent in Germany, the use of straw in combined heat and power generation
would be best for the climate. "Straw should therefore primarily be used in
larger district heating stations and/or combined heat and power stations, but
technology must be developed for an environmentally-friendly utilization",
stresses Dr. Armin Vetter from TLL, who has been operating a straw-fuelled
power station for 17 years.

Role model Denmark

According to the summary of the new study, straw-based
energy applications should be developed in Germany in particular in those
regions with favourable conditions and appropriate power plants. Even if we
wouldn't be spinning straw into gold in the foreseeable future, it would still
make an important contribution to the energy turnaround. Looking across the
border shows us what is feasible when the course is optimally set: currently
Denmark is still considered to be the world leader in straw-based energy
applications. Fifteen years ago a master plan was introduced there, ensuring in
the meantime in Germany´s northern neighbouring country that over five billion
kilowatt hours of energy per year is generated from straw.

 


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