It reduces emissions from slurry of the powerful
greenhouse gas methane – and the effect persists even after several months of
storage. However, the results also indicate that acidification can increase the
risk of problems with odour. Trials carried out
expected acidification to not only reduce ammonia emission, but also to inhibit
methane-producing bacteria. We have carried out some trials which showed that
this was indeed the case”, explains Søren O. Petersen from the Department of
Agroecology and Environment at the Faculty of Agricultural Sciences.
As a greenhouse gas methane is more than 20 times as
powerful as carbon dioxide. Emissions of methane from animal manure account for
almost 10 percent of total greenhouse gas emissions from Danish
”That is why treatment
techniques that reduce methane emissions during storage are interesting”, says
Søren O. Petersen.
Methane emissions measured
scientists measured methane emissions from cattle slurry with and without
acidification during three months of storage. The slurry was either untreated or
treated with various sulphur sources. While the untreated slurry emitted methane
during the whole 100-day period, the emission from slurry treated with sulphuric
acid was reduced by 90 percent.
There is, however, a downside to the
good news: the risk of increasing smell.
The turnover of sulphur in the
slurry can lead to production of several extremely pungent organic sulphur
compounds. Bacteria such as methane-producing bacteria would normally break them
down quickly. However, if acidification or other mechanisms inhibit these
bacteria, then the odorous compounds can accumulate in the slurry, escape to the
atmosphere and be unpleasant for the environment.
Scientists from several departments at
the Faculty of Agricultural Sciences are collaborating on charting the processes
in the acidified slurry. Understanding the regulation of degradation pathways
can perhaps help pave the way for new technical solutions.
”If we are to
take advantage of the beneficial effect of acidification on ammonia and methane
without risking increased problems with smell, then we need to understand the
microbiological metabolic pathways”, says Søren O. Petersen.
of the current study will be published in 2009.
• Faculty of
Agricultural Sciences at Aarhus University
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