Minimising the regeneration heat duty of post-combustion CO2 capture by wet chemical absorption: The misguided focus on low heat of absorption solvents

An ideal solvent for CO₂ capture by chemical absorption has to meet a number of requirements, such as high CO₂ capacity, high rate of reaction, low costs, low corrosive behaviour, low degradation and low vapour pressure; above all, it has to show a low regeneration heat duty. This heat can be approximated as the sum of three terms: the sensible heat to raise the solvent from absorber to desorber temperature, the heat of evaporation required to produce the stripping steam in the reboiler, and the heat necessary to desorb the CO₂ from the solution (heat of absorption).Many solvent screening studies focus almost exclusively on solvents that show a low heat of absorption. In these studies, the strong dependence of the three contributors to the overall regeneration heat duty on the chosen process parameters and on one another are often neglected.This work explains why the focus on solvents with a low heat of absorption, without considering the overall process, is not sufficient in quantifying the energy performance of alternative solvents. By using thermodynamic interrelations and underpinned by process simulations it is shown that operating parameters of the process, in particular the desorber pressure, must be taken into consideration in the evaluation of new solvents.     

PREDICTING INFLUENCES OF URBAN DEVELOPMENT ON THERMAL HABITAT IN A WARM WATER STREAM1

ABSTRACT: Watershed and aquatic ecosystem management requires methods to predict and understand thermal impacts on stream habitat from urbanization. This study evaluates thermal effects of projected urbanization using a modeling framework and considers the biological implications to the fish community. The Stream Network Temperature Model (SNTEMP) was used in combination with the Hydrologic Simulation Program Fortran (HSPF) to assess changes in stream thermal habitat under altered stream‐ flow, shade, and channel width associated with low, medium, and high density urban developments in the Back Creek watershed (Roanoke County, Virginia). Flow alteration by the high density development scenario alone caused minimal heating of mean daily summer base flow (mean +0.1°C). However, when flow changes were modeled concurrently with reduced shade and increased channel width, mean daily temperature increased 1°C. Maximum daily temperatures exceeding the state standard (31°C) increased from 1.1 to 7.6 percent of the time using summer 2000 climatic conditions. Model results suggest that additional urban development will alter stream temperature, potentially limiting thermal habitat and shifting the fish community structure from intolerant to tolerant fish species in Back Creek. More research is needed on the sub‐lethal or chronic effects of increased stream temperature regimes on fish, particularly for those species already living in habitats near their upper limits.     

Relationship between the position preference and nutritional state of individuals in schools of juvenile roach (Rutilus rutilus)

Summary Position preferences of well-fed and food-deprived juvenile roach were investigated in schools of 2 and 4 fish in the laboratory. Food-deprived fish appeared significantly more often in the front position than their well-fed conspecifics. For fish at the same hunger level, individuals at the front of the school had the highest feeding rate. These results represent the first evidence for a relationship between the nutritional state of individual fish and their positions in a school and suggest a functional advantage of the preference. Offprint requests to: J. Krause at the present address     

Basiswissen Umwelttechnik Wasser, Luft, Abfall, L?rm, Umweltrecht Hrsg: Bank, Matthias

Ohne Zusammenfassung     

Evaluating recycling fertilizers for tomato cultivation in hydroponics,and their impact on greenhouse gas emissions

Soilless culture systems offer an environmentally friendly and resource-efficient alternative to traditional cultivation systems fitting within the scheme of a circular economy. The objective of this research was to examine the sustainable integration of recycling fertilizers in hydroponic cultivation—creating a nutrient cycling concept for horticultural cultivation. Using the nutrient film technique (NFT), three recycling-based fertilizer variants were tested against standard synthetic mineral fertilization as the control, with 11 tomato plants (Solanum lycopersicum L. cv. Pannovy) per replicate (n = 4) and treatment: two nitrified urine-based fertilizers differing in ammonium/nitrate ratio (NH₄⁺:NO₃^?), namely (1) “Aurin” (AUR) and (2) “Crop” (CRO); as well as (3) an organo-mineral mixture of struvite and vinasse (S+V); and (4) a control (NPK). The closed chamber method was adapted for gas fluxes (N₂O, CH₄, and CO₂) from the root zone. There was no indication in differences of the total shoot biomass fresh matter and uptake of N, P and K between recycling fertilizers and the control. Marketable fruit yield was comparable between NPK, CRO and S+V, whereas lower yields occurred in AUR. The higher NH₄⁺:NO₃^? of AUR was associated with an increased susceptibility of blossom-end-rot, likely due to reduced uptake and translocation of Ca. Highest sugar concentration was found in S+V, which may have been influenced by the presence of organic acids in vinasse. N₂O emissions were highest in S+V, which corresponded to our hypothesis that N₂O emissions positively correlate with organic-C input by the fertilizer amendments. Remaining treatments showed barely detectable GHG emissions. A nitrified urine with a low NH₄⁺:NO₃^– (e.g., CRO) has a high potential as recycling fertilizer in NFT systems for tomato cultivation, and S+V proved to supply sufficient P and K for adequate growth and yield. Alternative cultivation strategies may complement the composition of AUR.

     

Resource allocation and population genetics of the bay scallop,Argopecten irradians irradians: effects of age and allozyme heterozygosity on reproductive output

The relationships among multiple-locus heterozygosity, age, reproduction and growth were examined over the ca. 2-yr lifespan of a cohort of northern bay scallops, Argopecten irradians irradians (Lamarck), from the Niantic River estuary, Connecticut, USA. Electrophoretic analyses revealed a relatively low proportion of polymorphic loci (=0.35) and low level of heterozygote deficiency ( D. across 6 loci=-0.05) in this population. Allele frequency distributions showed a high degree of temporal stability within and among cohorts. No significant correlation was found between multiple-locus heterozygosity and either somatic or reproductive growth. Our results lend support to the postulated linkage between low heterozygote deficit and lack of a heterozygosity/growth association in marine bivalves, and in the pectinid group in particular. Partial reproductive senility occurs in these scallops in their second year of life. Somatic tissue weight increased exponentially with increasing shell height, whereas pre-spawning gonad mass attained asymptotic values in 2-yr-old scallops. Thus, weight-specific reproductive effort was significantly lower in second- than first-year scallops (24 and 33% respectively). This pattern could be generated if high individual reproductive effort in the first year were correlated with accelerated (early) post-reproductive senescence. This kind of resource allocation, in which somatic growth is given precedence over reproductive growth in older individuals, has been previously reported in only one other bivalve, a pectinid (Chlamys islandica), in which the decline in reproductive effort occurs only after the scallops reach an age of ca. 20 yr.     

Feather-like development of Triassic diapsid skin appendages

Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama's appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.