Competition,defense and games between plants

Summary Coexistence of defended and undefended plants may be maintained by herbivory. In the present paper this phenomenon is analyzed by means of evolutionary game theory. The plants in the model play either a defensive or a non-defensive strategy and they interact indirectly: when a plant is grazed its competitive ability decreases, because of this a neighboring plant makes a profit. The solution to the game leads to three qualitatively different cases depending on whether the profit is equal for the two strategies, defended and undefended, or if the profit is higher for one type than for the other. When the results are applied to intea-specific interactions, the model predicts that polymorphic populations should be expected only under certain specific conditions. When the results are applied to inter-specific interactions, the model predicts either stable coexistence, i.e., increased diversity, or a paradoxical situation without increased diversity.Offprint requests to: M. Augner     

Avoiding CO2 capture effort and cost for negative CO2 emissions using industrial waste in chemical-looping combustion/gasification of biomass

Chemical-looping combustion (CLC) is a combustion process with inherent separation of carbon dioxide (CO₂), which is achieved by oxidizing the fuel with a solid oxygen carrier rather than with air. As fuel and combustion air are never mixed, no gas separation is necessary and, consequently, there is no direct cost or energy penalty for the separation of gases. The most common form of design of chemical-looping combustion systems uses circulating fluidized beds, which is an established and widely spread technology. Experiments were conducted in two different laboratory-scale CLC reactors with continuous fuel feeding and nominal fuel inputs of 300 W_th and 10 kW_th, respectively. As an oxygen carrier material, ground steel converter slag from the Linz–Donawitz process was used. This material is the second largest flow in an integrated steel mill and it is available in huge quantities, for which there is currently limited demand. Steel converter slag consists mainly of oxides of calcium (Ca), magnesium (Mg), iron (Fe), silicon (Si), and manganese (Mn). In the 300 W unit, chemical-looping combustion experiments were conducted with model fuels syngas (50 vol% hydrogen (H₂) in carbon monoxide (CO)) and methane (CH₄) at varied reactor temperature, fuel input, and oxygen-carrier circulation. Further, the ability of the oxygen-carrier material to release oxygen to the gas phase was investigated. In the 10 kW unit, the fuels used for combustion tests were steam-exploded pellets and wood char. The purpose of these experiments was to study more realistic biomass fuels and to assess the lifetime of the slag when employed as oxygen carrier. In addition, chemical-looping gasification was investigated in the 10 kW unit using both steam-exploded pellets and regular wood pellets as fuels. In the 300 W unit, up to 99.9% of syngas conversion was achieved at 280 kg/MW_th and 900 °C, while the highest conversion achieved with methane was 60% at 280 kg/MW_th and 950 °C. The material’s ability to release oxygen to the gas phase, i.e., CLOU property, was developed during the initial hours with fuel operation and the activated material released 1–2 vol% of O₂ into a flow of argon between 850 and 950 °C. The material’s initial low density decreased somewhat during CLC operation. In the 10 kW, CO₂ yields of 75–82% were achieved with all three fuels tested in CLC conditions, while carbon leakage was very low in most cases, i.e., below 1%. With wood char as fuel, at a fuel input of 1.8 kW_th, a CO₂ yield of 92% could be achieved. The carbon fraction of C₂-species was usually below 2.5% and no C₃-species were detected. During chemical-looping gasification investigation a raw gas was produced that contained mostly H₂. The oxygen carrier lifetime was estimated to be about 110–170 h. However, due to its high availability and potentially low cost, this type of slag could be suitable for large-scale operation. The study also includes a discussion on the potential advantages of this technology over other technologies available for Bio-Energy Carbon Capture and Storage, BECCS. Furthermore, the paper calls for the use of adequate policy instruments to foster the development of this kind of technologies, with great potential for cost reduction but presently without commercial application because of lack of incentives.

     

Re-cycling of remediated soil in Sweden: An environmental advantage?

The disposal of soil material after ex situ treatment of contaminated soil is an issue of growing concern. The handling and use of this material are surrounded by numerous regulatory, economic, technical and societal aspects that complicate or hinder re-cycling. As a consequence, the lack of means of recovery can in the long-term bias the whole remedial process. In addition, it can affect the competition between various treatment options such as ex situ, and in situ techniques and landfilling. At the same time the materials must not have any negative environmental impacts, and their usage must be compatible with existing risk assessment and management frameworks regarding contaminated land. Other concerns such as a possible distinction against “lightly” contaminated materials, waste status and public acceptance add to the complexity. This paper focuses on Swedish conditions, but does also provide an outlook concerning EU regulation. A summary of leaching and batch tests employed for re-use of soil and waste is presented as well as an overview of the eco-toxicological aspects of treated materials. The main conclusion is that re-cycling of treated soil is desirable from numerous aspects, but has to go along an adequate risk assessment.     

A case study on raw material blending for the recycling of ferrous wastes in a blast furnace

The utilisation of ferrous wastes in a blast furnace is a well established recycling process to cope with the enormous amounts of ferrous residues in the iron and steel industry. The further input flows of this process, that is especially coke and fluxes, as well as its output flows, that is pig iron and by-products, are highly dependent on the blending of the ferrous wastes while they differ highly in the revenues gained for the treatment and their chemical composition. So far, no planning approach exists for the blending of the residues on the operational planning level that models the dependency of the costs and revenues on the raw material blend and the thermodynamic reactions in the recycling processes adequately. Therefore we present an approach for this operational production planning problem focusing on an integration of such a sufficiently detailed modelling of the underlying metallurgical processes into the planning model. The basis of our approach is a thermodynamic simulation of the processes. From this simulation we derive linear input-output functions for the relevant material and energy flows by using multiple linear regression. These input–output functions form the core of our blending model developed for the planning task. The model is implemented as an integrated decision support system. Exemplary application results are given. These results validate the approach and show that ecological the economic optimisation leads also to results which are advantageous in terms of resource efficiency and emission reduction. Though developed for a specific recycling process, the methodology can be transferred to other metallurgical (recycling) processes, as well as other parts of the process industries, and is therefore of high relevance.     

History of Fly Ash Collection at the South Charleston Plant Union Carbide Corporation—Chemicals Division

This report summarizes the installation and operation of fly ash collection and disposal equipment at the South Charleston Plant and includes installation costs, replacement costs based on present-day cost factors, as well as performance data, and maintenance and operating costs.     

Teratogenicity of bifenox and nitrofen in rodents

Abstract

The teratogenicity of the diphenyl ether herbicide bifenox [2,4‐dichlorophenyl 3'‐carboxymethyl‐4'‐nitrophenyl ether] was compared to that of nitrofen [2,4‐dichlorophenyl 4'‐nitrophenyl ether] in rats and in mice. Neither compound increased prenatal mortality in mice. Because nitrofen causes both malformations that are compatible with survival to weaning and a high incidence of perinatal (but not of fetal) mortality, emphasis was placed on postnatal parameters of bifenox toxicity. In rats, bifenox caused a low incidence of “bloody tears”;, but it did not decrease survival to term or to weaning in rats or mice, and did not reduce Harderian gland weight in mice. Because the weight of the Harderian glands is a more objective measure of their status than is the presence of an eye discharge, it is concluded that bifenox is not teratogenic at the levels administered. Nitrofen decreased litter size, pup weight, and Harderian gland weight in mice.