Whole-crop cereal silage represents an important component of ruminant diets and is used as a substrate for biogas production. Due to the scarcity of data on whole-crop rye (Secale cereale L., WCR), our study aimed to evaluate the effects of a range of biological and chemical additives of different compositions on the fermentation and aerobic stability of silage made from this species. In addition, the production of various volatile organic compounds (VOCs), which potentially contribute to greenhouse gas emissions, was monitored. Regardless of additive treatment, all WCR silages were well fermented as reflected by the complete absence of butyric acid. Inoculants containing Lactobacillus buchneri and chemical additives reduced dry matter (DM) losses during fermentation for 53 days (p < 0.001), which were closely related with the concentration of ethanol upon silo opening (R² = 0.88, p < 0.001). Silage treated with Lactobacillus buchneri, alone or in combination with a homofermentative strain, had the lowest yeast count (p < 0.001) and, simultaneously, the highest aerobic stability (p < 0.001). Chemical additives outperformed all other additives by largely restricting the formation of ethyl esters of lactic and acetic acids (p < 0.001). The concentration of ethanol strongly correlated with those of ethyl lactate (R² = 0.94, p < 0.001), ethyl acetate (R² = 0.85, p < 0.001), and total ethyl esters (R² = 0.94, p < 0.001). The use of a simple linear regression model exclusively based on the ethanol content proved useful to predict the concentration of total ethyl esters in WCR silage (R² = 0.93, p < 0.001).

The use of human excreta in the context of the circular economy has the potential to recycle nutrients, save water and energy, and sequester carbon. However, the risk of pathogen contamination of soil and crops, particularly from land application of solid human excreta (feces), is a realistic scenario. In our study we investigated a double thermophilically treated and quality assured compost (Hygienized Human Feces Compost). We used indicator organisms for fecal contamination to monitor the risk of pathogen contamination of the soil after application of human feces compost. Indicator organisms were Escherichia coli, Salmonella spp., Enterococcus spp. and Clostridium perfringens. One pot experiment under semi-controlled conditions and three on-farm experiments were conducted on loamy sand and sand soils. The experimental period ranged from 58 to 1123 days. The levels of fecal indicator organisms in soil show a consistent pattern across all experiments. E. coli, Salmonella spp. and Enterococcus spp. were not detected in any of the soil samples. C. perfringens was found in concentrations ranging from <10 to 10³ CFU g^-1 FM. However, there was no evidence of a systematic increase in the soil concentrations of C. perfringens following human feces compost application. In different years and under different experimental conditions, we were not able to detect any increase in the concentration of indicator organisms for fecal contamination in our experiments. We therefore assume that sandy soils might be generally suitable for application of quality-assured fertilizers from human excreta.