14th Ramiran International Conference, Lisboa 12-15th September 2010
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0237
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Modelling ammonia emissions after field application of biogas slurries
Andreas Pacholski
, Dirk Gericke, Ni Kang, Quakernack Robert, Kage Henning
Christian-Albrechts-University at Kiel, Institute of Crop Science and Plant Breeding,
Agronomy
and Crop Science, Kiel, Germany
In Germany
, the production of biogas from energy cropping systems has been in the focus of the
national bio-energy strategy for the reduction of greenhouse gas emissions since the year 20004.
Their greenhouse gas saving benefit can be strongly decreased by other adverse environmental
ef
fects induced by biogas systems as greenhouse gas and ammonia emissions.
Ammonia
emissions which are unavoidable as biogas slurries have to be re-transferred to the field as N-
fertilizers, contribute indirectly to greenhouse gas emissions. In addition ammonia emissions are
the main source of eutrophicating and acidifying compounds deposited on natural and semi-
natural ecosystems.
There is thus an urgent need to quantify NH3 emissions from biogas
production systems. For scenario and regionalisation simulations, model approaches for NH3
emissions after field applications of biogas slurries are of particular interest.
Model development was carried out on the basis of intensive ammonia loss field measurements
carried out in the years 2007-2009 in biogas cropping systems grown in Northern Germany
.
Altogether 18 experimental campaigns including the simultaneous measurement of several
animal and biogas slurries were carried out in multiple plot field experiments using dif
ferent N-
fertilization levels. For the determination of NH3 emissions micrometeorological as well as plot
based measurement approaches were used and subsequently cross- checked.
Several new dynamic and empirical model approaches were tested which can be applied for the
calculation of NH3 losses after field application of biogas and animal slurries to energy crops. In
addition to the well known principles for calculation of ammonia losses based on temperature, pH
and soil water relationships new algorithms were implemented to account for the ef
fects of slurry
incorporation, crop type, canopy structure and precipitation on NH3 emissions. Model results
showed a good agreement with measured data with respect to both simulated ammonia loss
dynamics as well absolute final losses.
As compared to validation data the models show a
quantitative accuracy of cumulated NH3 losses in between 1 - 2 kg N ha-1 which is in the range
of the measurement accuracy of commonly used measurement methods.