Long-term evaluation of activated carbon as an adsorbent for biogas desulfurization.

In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. Biogas containing 932-2,350 ppm of H2S was collected from an anaerobic digester to treat the wastewater from a dairy farm with about 200 cows. An adsorption test was performed by introducing the biogas to a column that was packed with approximately 50 L of commercial GAC. The operation ceased if the effluent gas had an H2S concentration of over 100 ppm. The GAC was replaced by a given weight of new GAC in a subsequent test. According to the results, for H2S concentrations in the range of 932-1,560 ppm (average±SD = 1,260 ± 256 ppm), 1 kg of the GAC yielded biogas treatment capacities of 568 ± 112 m3 and H2S adsorption capacities of 979 ± 235 g. For the higher influent H2S concentrations of 2,110 ± 219 ppm, the biogas treatment and H2S-adsorption capacities decreased to 229 ± 18 m3 and 668 ± 47 g, respectively. An estimation indicated a requisite cost of US$16.5 for the purification of 1,000 m3 of biogas containing 2,110 ppm of H2S. This cost is approximately 5% of US$330, the value of 1,000 m3 of biogas. IMPLICATIONS: Biogas generated from anaerobic digesters of animal manure and municipal wastewater sludge contains hydrogen sulfide which must be removed before it can be combusted in electricity-generation engines. This study demonstrated that commercial activated carbon adsorption can be an economical and effective approach for removing hydrogen sulfide from biogas. In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. The biogas containing 932-2,350 ppm of H2S was collected from an anaerobic digester for treating wastewater collected from a 200 dairy farm. The adsorption test was performed by introducing the biogas to a PVC column packed with a commercial GAC of around 50 L. Operation ceased if the effluent gas had an H2S concentration of over 100 ppm. A given weight of the new GAC was replaced for a successive test.

Feasibility assessment of a tunnel-ventilated, water-padded barn on alleviation of heat stress for lactating Holstein cows in a humid area.

The use of evaporative cooling for mitigating heat stress in lactating cows in humid areas is controversial. In Taiwan, Holstein cow performance is significantly restricted by hot and humid weather. This study investigated the efficacy of using a tunnel-ventilated, water-padded freestall (TP) barn for reducing heat stress in lactating cows. From August to October 2006, 36 cows allocated in a 3×3 Latin square were raised in 3 barn cooling treatments: a conventional freestall barn with fans and sprinklers in the feed line (Fan+SP, control), a TP barn, and a TP barn with sprinkler cooling (TP+SP). Daytime air speeds in the 3 barns were 1.23, 2.38, and 2.06 m/s, respectively. Both TP barns were more efficient than the control in reducing the daytime temperature and temperature-humidity index. The barn temperature was <26°C for an extra 4.2h per day, but the relative humidity was >96% in both TP barns. Cows in both TP barns had higher respiration rates and skin temperatures at 0300 h than cows in the Fan+SP barn. The TP environment increased the cows' serum cholesterol level and the activities of alkaline phosphatase and alanine aminotransferase, but blood partial pressure of CO(2) was not affected. Vaginal temperature was persistently high in cows in the TP barn; in the 2 SP barns, it decreased 0.4 to 0.6°C following sprinkling and milking. The intake activity and rumen digestion of cows raised in the 3 environments were similar. Cows in both TP barns ingested more dry matter. Cows in the TP+SP barn tended to produce more milk than those in the Fan+SP barn (25.4 vs. 24.7 kg). Although heat stress was not completely alleviated in these 3 barns, the TP+SP treatment resolved the negative effect of a previous TP barn built in 2004 on intake and milk yield by increasing air speed and using sprinkler cooling. Thus, it is expected that TP+SP barns will be beneficial in regions with high humidity. Adequate air speed and sprinkler cooling are likely to be key factors for further study.

Prostaglandin F2 alpha receptors in the early bovine corpus luteum.

Since the early CL (< or = 4 days after ovulation) does not regress after injection of PGF2 alpha, this study was designed to determine whether number or affinity of PGF2 alpha receptors was lower in the early as compared with the midstage CL. Heifers were randomly assigned to have ovaries removed on Day 2, 4, 6, or 10 (n = 4 heifers per day; Day 0 = day of ovulation). Plasma progesterone concentrations and the weight and size of the CL increased from Day 2 to 6, indicating normal CL development. Plasma membranes from individual CL were evaluated for PGF2 alpha receptor concentration and affinity by Scatchard analysis. CL from each of the 4 days of the estrous cycle were not different with respect to PGF2 alpha receptor concentration (number per microgram of plasma membrane protein) and affinity. To examine tissue specificity, PGF2 alpha binding was evaluated in 12 organs or tissues. High-affinity PGF2 alpha receptors were found in the CL and adrenal medulla but not in granulosa cells or other tissues. In conclusion, a single class of high-affinity PGF2 alpha receptors was present within the bovine CL by 2 days after ovulation; therefore the reported lack of responsiveness to PGF2 alpha in the early CL was not attributable to a deficiency of high-affinity PGF2 alpha receptors.