The possibility of converting hydrogen to methane and simultaneous upgrading of biogas was investigated in both batch tests and fully mixed biogas reactor, simultaneously fed with manure and hydrogen. Batch experiments showed that hydrogen could be converted to methane by hydrogenotrophic methanogenesis with conversion of more than 90% of the consumed hydrogen to methane. The hydrogen consumption rates were affected by both P(H₂) (hydrogen partial pressure) and mixing intensity. Inhibition of propionate and butyrate degradation by hydrogen (1 atm) was only observed under high mixing intensity (shaking speed 300 rpm). Continuous addition of hydrogen (flow rate of 28.6 mL/(L/h)) to an anaerobic reactor fed with manure, showed that more than 80% of the hydrogen was utilized. The propionate and butyrate level in the reactor was not significantly affected by the hydrogen addition. The methane production rate of the reactor with H₂ addition was 22% higher, compared to the control reactor only fed with manure. The CO₂ content in the produced biogas was only 15%, while it was 38% in the control reactor. However, the addition of hydrogen resulted in increase of pH (from 8.0 to 8.3) due to the consumption of bicarbonate, which subsequently caused slight inhibition of methanogenesis.

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A polymerase chain reaction (PCR) procedure was developed for analysis of viable Salmonella spp. in feed samples and scrapings from feed mills. The objective was to develop a cost‐effective, user‐friendly method that could be performed within ordinary working hours. A single pre‐enrichment was enough for most feed raw materials. However, scrapings and pellets required additional pre‐enrichment. The results indicate that inhibition of the PCR reaction was correlated with a pH value below 7.0 in the first pre‐enrichment. Results of the PCR procedure were in agreement with the established culture‐based Nordic Committee on Food Analysis method in spiked samples. The developed PCR procedure can be used as a routine analysis method for feed samples and samples from a Salmonella feed control program based on hazard analysis critical control point principles.