Effects of anaerobic digestion and additives to effluent or cattle feed onodor and odorant concentrations

Odor intensity (5,437 observations), determined by human panelists (100 dif ferent panelists over the course of the experiment), and a number of chemic al odorant concentrations were determined for manure-related samples (326) obtained from effluents from conventional stirred-tank reactor (CSTR) and f ixed-film anaerobic digesters, effluents to which commercial additives or K MnO4 or H2O2 were added, and feces, urine, and mixed manure from cows fed a control or additive-containing diet. Mostly, samples were held in stoppere d, Erlenmeyer flasks for 3 d at room temperature before evaluation by panel ists and with chemical analyses, but shorter holding times also were tested . Anaerobic digestion reduced odor intensity linearly with increasing hydra ulic retention time (HRT) up to 20 d; fixed-film digestion with 1.5- or 2.3 -d HRT reduced odor intensity similarly to that observed with 10-d HRT in C STR. Addition of commercial products and chemicals altered some odorant con centrations (e.g., ammonia) but did not reduce odor intensity; some product s increased odor intensity. Addition of a commercial yeast-based product to a dairy cow diet had no detectable effect. The cow diet study showed that fresh urine and feces alone were less odorous than a mixed combination (man ure). Fresh manure was less odorous than manure held for 3 d. Total phenol was the odorant most highly correlated with odor intensity. Individual and total volatile fatty acids also contributed. Ammonia did not seem to be a m ajor contributor to odor in this data set.