Swine livestock farms represent potential sources of emissions
of gaseous compounds and odors in relation to slurry management,
manure treatment, and particularly, storage. Electrolytic
treatments of slurries were proposed to solve this pressing problem.
Electrolytic treatment consists of the passage of a low electric
current through the liquid phase of swine manure in storage basins
determined by two or more electrodes with alternated polarisation.
We investigated the mechanisms of odour reduction and evaluated
the effects of current intensity and of anodically dissolved copper
(Cu2+) ions. Fresh swine slurry was subject to electrolytic treatment
in a bench top experiment, at 25 mA and 75 mA for 32 days
with either copper or graphite electrodes. Emissions of methane,
hydrogen sulphide, and volatile fatty acids were measured. Effects
of copper addition to fresh swine slurry were also monitored in a
bench top scale trial. Reduction of emissions was found to be due
to both current passage and copper dissolution. Reduction of foul
emissions in graphite electrodes assays resulted lower than in copper
electrodes assays, although the direct additions of Cu2+ ions
had a much larger effect than could be predicted from the results
of electrolytic treatments with copper electrodes, probably due to
the greater uniformity in distribution in swine manure. A simple
empiric odour threshold value normalised index, odour offensiveness
index of slurries, was found to be effective in differentiating
treatments.
