The effect of acidogenic and methanogenic conditions on the availability and stability of carbon, nitrogen and phosphorus in a digestate

Acidification and drying of digestate are important post-treatment for, respectively, improving nutrient availability and hygiene. These approaches are expected to reduce digestate soil application mass and increase its value. This study compared eleven organic feedstocks under acidogenic and methanogenic conditions as a sustainable approach to improving phosphorus availablity, organic carbon and stabilising ammoniacal nitrogen of the resulting digestate under thermal drying. The result showed increases in phosphate concentration under acidogenic conditions and reduction in ammonium nitrogen after drying at 100 °C. The highest phosphate values of 3.2 ± 0.38 g/kg were achieved using whey permeate substrate while the effect of drying on ammonium nitrogen concentration was lowest for acidogenic bird seed fermentation with an ammonium loss of 59.7%. Both results were facilitated by high total volatile fatty acid concentration produced from available organic carbon which reached a maximum value of 5.71 ± 0.53 g/L, respectively. Increases in phosphate and ammonium nitrogen stability under acidogenic conditions was a consequence of lower pH, a condition synonymous with acidogenic only fermentation. The accumulated volatile fatty acid contributed to higher carbon to nitrogen ratio under acidogenic fermentation. Higher labile carbon to nitrogen ratio can trigger immobilization of ammonium nitrogen in the soil and this presents a case for subsequent experimentation into acidogenic digestate application in soil

Evaluation of some heavy metals bio-accumulation in meat and haemolymph of african landsnail (Archachatina Marginata Swainson)

The impact of captive rearing of snails (Archachatina marginata) on the bio-accumulation of some heavy metals (HMs) (Fe, Mn, Cu, Pb, Co, Ni, Cd and Cr) in the meat and haemolymph was evaluated in a two treatment trial (snails from the wild, (SW) and captive reared snails, (SC), each comprised of sixty snails of three replicates. Alldata collected (using standard analytical procedures) were subjected to ANOVA and significant means separated by Duncan Multiple Range Test. The trial revealed that the meat of SC had outstanding (P>0.05) Fe (22.30mg/kg) and Mn(4.79mg/kg), with no significant variation for DM, while the haemolymph recorded non-significant (P< 0.05) concentration for (Mn, Pb, Co, Ni, Cd and Cr). Its levels of Fe (3.50mg/kg) and Cu (2.06mg/kg) were however significantly (P>0.05) impacted by captive rearing. Generally the level of Cr in the meat and haemolymph were higher than 0.05mg/kg recommendation by WHO, hence snail meat and haemolymph must be consumed with caution and guidance

Effect of variation in temperature and relative humidity on the reproductive performance of grasscutters held in captivity

This study investigated the reproductive performance of grasscutter through oestrus, mating, parturition, abortion and litter size in establishing the success of this performance during the rainy season and dry season. Effects of the atmospheric temperature and relative humidity on the reproductive performance of grasscutter in captivity were duly observed. Twenty female grasscutters were used with ten males for mating and were subsequently individually caged to determine the outcome of male-female contact (i.e. mating, conception and parturition). The signs of mating were detected by observing the marks of climbing at the back of the female grasscutter (doe),observing the changes in the perineum of the female before and after mating, monitoring the changes in weight gained post-mating and presence of fetuses by abdominal palpation. Parturition was detected by monitoring the expectant mothers with successful mating signs and distended abdomens. Keywords: Grasscutter, reproductive performance, reproduction, parturition, mating

Co-fermentation of whey permeates and cattle slurry using a partitioned up-flow anaerobic digestion tank

Whey permeate and slurry are both from the dairy farm animals while whey is characterised with high acidity the slurry is mildly alkaline, and they are both biodegradable. In this study, a lab-scale partitioned up-flow anaerobic digestion tank was used to achieve a suitable feeding regime for co-fermenting whey permeate and slurry. The partitioned up-flow anaerobic digestion tank provided a stable treatment performance with over 95% of sugar reduction and a total volatile fatty acid concentration under 150 mg/L. The ripely ratio of the reactor was below 0.4 which suggest strong buffering stability. Biogas production surged with an increase in the feeding regime from 1:1 to 4:1 with a maximum value of 3.5 L/d. This was not the case for the methane content which continued to reduce as the feeding regime increased from 2:1 to 4:1. The feeding regime of 2:1 recorded the highest methane composition between 40 and 50% which suggests this is the best feeding regime for co-fermenting whey permeate and slurry using a partitioned up-flow anaerobic digestion tank

The effect of different C-N ratios on volatile fatty acid (VFAs) production from acidogenic fermentation of sucrose in continuous-stirred tank reactors

This study evaluates the production of volatile fatty acids (VFAs) from the acidogenic anaerobic digestion of sucrose in continuous-stirred tank reactors. A semi-continuously feed operational process was employed to observe the influence of different carbon–nitrogen ratios (C-N), from 5 to 100, on the volume and composition of VFA production. With a steady increase in VFA production, the C-N 5 assay attained the highest concentration with a VFA value of 26.08 g L−1 after 15 days of incubation, while on the 13th day of incubation, the maximum VFA concentration of 23.82 g L−1, 20.44 g L−1, 16.76 g L−1, 11.88 g L−1, and 11.60 g L−1 was attained in C-N 10, C-N 20, C-N 30, C-N 50, and C-N 70 assays respectively. Acetic acid and butyric acid were the principal VFAs observed in all the different C-N assays tested in this study. The mean values of acetic acid ranged from 64.58 to 79.12% for C-N increase between 5 and 100. On the other hand, C-N variations between 5 and 100 resulted in a significant decrease in butyric acid production from 30.33 to 13.93%. Volatile solid degradation and carbohydrate utilization rates decreased from 41.86 to 32.45% and 78.56 to 61.25% respectively as C-N ratios increased from 5 to 100. This aligns with the hypothesis that increasing the nitrogen content of substrate increases VFA production. Our findings provide new information regarding the C-N ratios for improved VFA production from acidogenic fermentation of sucrose