An Economic and Environmental Analysis of Slurry Separation

With increased pressure to redistribute animal manure in order to lower the environmental pressure from agriculture, it seems obvious to consider processing slurry into nutrient rich fractions which can easily be transported. In this paper, an overall analysis of four different separation technologies is presented. The four technologies are Decanter, Funki Manura 2000, Green Farm Energy and Staring. These technologies are all implemented on a full scale in Denmark. In this paper both the economic and environmental aspects are considered, looking at the entire chain from stable to the field. The total investments range from 50,000 to 4 million Euros and the total net costs are from 1 to 7 Euros per tonne for the four different technologies. One of the clear environmental benefits is a better utilisation of phosphorus, but using phytase in feeding is a cheaper first step when reducing phosphorus surplus. Improved nitrogen utilisation is only apparent with the Staring and Green Farm Energy concepts. The conclusion is that the Funki Manura 2000 system is too expensive and the Decanter system a fairly cheap way to reduce phosphorus levels, but other benefits are limited. Staring and Green Farm Energy show the greatest potential, but these systems have not been running long enough to validate the expected results included in this paper.Resource /Energy Economics and Policy,

Topology and shape optimization of induced-charge electro-osmotic micropumps

For a dielectric solid surrounded by an electrolyte and positioned inside an externally biased parallel-plate capacitor, we study numerically how the resulting induced-charge electro-osmotic (ICEO) flow depends on the topology and shape of the dielectric solid. In particular, we extend existing conventional electrokinetic models with an artificial design field to describe the transition from the liquid electrolyte to the solid dielectric. Using this design field, we have succeeded in applying the method of topology optimization to find system geometries with non-trivial topologies that maximize the net induced electro-osmotic flow rate through the electrolytic capacitor in the direction parallel to the capacitor plates. Once found, the performance of the topology optimized geometries has been validated by transferring them to conventional electrokinetic models not relying on the artificial design field. Our results show the importance of the topology and shape of the dielectric solid in ICEO systems and point to new designs of ICEO micropumps with significantly improved performance.Comment: 18 pages, latex IOP-style, 7 eps figure

Static elastic wall properties of the abdominal porcine aorta in vitro and in vivo

Objectives:To characterise possible differences in vascular mechanics between in vitro and in vivo settings.Design:Experimental animal study.Material:Segments of abdominal aorta from five 30kg pigs were studied in vitro and five porcine abdominal aortas were investigated in vivo.Methods:Vessel luminal cross-sectional area (CSA) was assessed in vitro and in vivo by measuring the electrical impedance of fluid inside a distensible balloon mounted on a catheter. Wall thickness was measured in vitro by means of 20 MHz A-mode ultrasound. The obtained values in vitro were used to calculate wall thickness in vivo.Results:The CSAs were larger in vitro than in vivo (p < 0.05). All segments showed stress-strain relations that accorded well with the exponential equation: Stress = a.exp(b.Strain). The y-axis intercepts (a) and the slope of the curves (b) were different in vitro and in vivo (p < 0.05). Differences were found between the aorta in vivo and in vitro regarding the circumferential stress-strain relations, i.e. the stiffest abdominal aorta was found in vivo.Conclusions:The differences in dimensions and wall stiffness may be attributed to the tethering to the surrounding tissues in vivo. Impedance planimetry combined with high frequency ultrasound is an accurate way of measuring segmental vascular elasticity in vivo

Longitudinal residual strain and stress-strain relationship in rat small intestine

BACKGROUND: To obtain a more detailed description of the stress-free state of the intestinal wall, longitudinal residual strain measurements are needed. Furthermore, data on longitudinal stress-strain relations in visceral organs are scarce. The present study aims to investigate the longitudinal residual strain and the longitudinal stress-strain relationship in the rat small intestine. METHODS: The longitudinal zero-stress state was obtained by cutting tissue strips parallel to the longitudinal axis of the intestine. The longitudinal residual stress was characterized by a bending angle (unit: degrees per unit length and positive when bending outwards). Residual strain was computed from the change in dimensions between the zero-stress state and the no-load state. Longitudinal stresses and strains were computed from stretch experiments in the distal ileum at luminal pressures ranging from 0–4 cmH(2)O. RESULTS: Large morphometric variations were found between the duodenum and ileum with the largest wall thickness and wall area in the duodenum and the largest inner circumference and luminal area in the distal ileum (p < 0.001). The bending angle did not differ between the duodenum and ileum (p > 0.5). The longitudinal residual strain was tensile at the serosal surface and compressive at the mucosal surface. Hence, the neutral axis was approximately in the mid-wall. The longitudinal residual strain and the bending angle was not uniform around the intestinal circumference and had the highest values on the mesenteric sides (p < 0.001). The stress-strain curves fitted well to the mono-exponential function with determination coefficients above 0.96. The α constant increased with the pressure, indicating the intestinal wall became stiffer in longitudinal direction when pressurized. CONCLUSION: Large longitudinal residual strains reside in the small intestine and showed circumferential variation. This indicates that the tissue is not uniform and cannot be treated as a homogenous material. The longitudinal stiffness of the intestinal wall increased with luminal pressure. Longitudinal residual strains must be taken into account in studies of gastrointestinal biomechanical properties

Rainforest conservation as a strategy of climate policy

Tropical forest conservation in developing countries has repeatedly been highlighted as a new element in international climate policy. However, no clear ideas yet exist as to what shape such a conservation strategy might take. In the present paper, we would like to make some observations to this end. It is shown how projects in order to reduce CO2-emissions resulting from deforestation and degradation (REDD) can be integrated into a system of tradable emission rights in an industrialised country and which requirements ought to be fulfilled. Instruments are emission credits and emission allowances. Driving actors interested in emission rights through forest projects may be private investors or the rainforest state itself. The efficiency of the system depends on a great extent on a binding reference path for the tolerable emissions from deforestation, which has been agreed upon and adhered to by the rainforest country by means of a forest law aimed at limiting deforestation. Our considerations lead us to conclude that the national baseline approach with an appropriate contribution by the rainforest country coupled with a decentralised system with private investors seems the most viable option. Since additional burdens are imposed on the rainforest country to some extent, a compromise could consist of agreeing on a moderate deforestation path, which is harmonised with the benefits from the forest projects. Combining both programmes (offset credits and emission allowances) is particularly attractive because all participants, and especially the industrialised country, benefit from it. The industrialised country can expand its climate conservation programme without any additional costs to a certain degree

Mechanisms and Evolution of Oxidative Sulfur Metabolism in Green Sulfur Bacteria

Green sulfur bacteria (GSB) constitute a closely related group of photoautotrophic and thiotrophic bacteria with limited phenotypic variation. They typically oxidize sulfide and thiosulfate to sulfate with sulfur globules as an intermediate. Based on genome sequence information from 15 strains, the distribution and phylogeny of enzymes involved in their oxidative sulfur metabolism was investigated. At least one homolog of sulfide:quinone oxidoreductase (SQR) is present in all strains. In all sulfur-oxidizing GSB strains except the earliest diverging Chloroherpeton thalassium, the sulfide oxidation product is further oxidized to sulfite by the dissimilatory sulfite reductase (DSR) system. This system consists of components horizontally acquired partly from sulfide-oxidizing and partly from sulfate-reducing bacteria. Depending on the strain, the sulfite is probably oxidized to sulfate by one of two different mechanisms that have different evolutionary origins: adenosine-5′-phosphosulfate reductase or polysulfide reductase-like complex 3. Thiosulfate utilization by the SOX system in GSB has apparently been acquired horizontally from Proteobacteria. SoxCD does not occur in GSB, and its function in sulfate formation in other bacteria has been replaced by the DSR system in GSB. Sequence analyses suggested that the conserved soxJXYZAKBW gene cluster was horizontally acquired by Chlorobium phaeovibrioides DSM 265 from the Chlorobaculum lineage and that this acquisition was mediated by a mobile genetic element. Thus, the last common ancestor of currently known GSB was probably photoautotrophic, hydrogenotrophic, and contained SQR but not DSR or SOX. In addition, the predominance of the Chlorobium–Chlorobaculum–Prosthecochloris lineage among cultured GSB could be due to the horizontally acquired DSR and SOX systems. Finally, based upon structural, biochemical, and phylogenetic analyses, a uniform nomenclature is suggested for sqr genes in prokaryotes