Methane and carbon dioxide emission in a two-phase olive oil mill sludge windrow pile during composting

The aim of this work was to make some preliminary evaluations on CO(2) and CH(4) emissions during composting of two-phase olive oil mill sludge (OOMS). OOMS, olive tree leaves (OTL) and shredded olive tree branches (OTB) were used as feedstock for Pile I and Pile II with a 1:1:1 and 1:1:2v/v ratio, respectively. Each pile was originally 1.2m high, 2.0m wide and approximately 15.0m long. Four 500 ml volume glass funnels were inverted and introduced in each pile, two in the core (buried 50-60 cm from the surface) and two near the surface under a thin 10-15 cm layer of the mixture. Thin (0.5 cm diameter) plastic, 80 cm long tubes were connected to the funnels. A mobile gas analyser (GA2000) was used to measure the composition (by volume) of O2, CO2 and CH4 on a daily basis. The funnels were removed prior to each turning and reinserted afterwards. From each pair of funnels (core and surface) of both piles, one was kept closed between samplings. Two way ANOVA was used to test differences between piles and among the tubes. Post hoc Tukey tests were also used to further investigate these differences. There was a significant difference (at p<0.001) in the two piles for all three gases. The average concentrations of O2, CO2 and CH4 in Pile I, from all four funnels was 16.86%, 3.89% and 0.25%, respectively, where for Pile II the average values were 18.07%, 2.38% and 0.04%, respectively. The presence of OOMS in larger amounts in Pile I (resulting in more intense decomposing phenomena), and the larger particle size of OTB in Pile II (resulting in increasing porosity) are the probable causes of these significant differences. Samples from open funnels presented lower, but not significantly lower, O2 composition (higher for CO2 and CH4) in comparison with closed funnels in both depths and both piles. Not significant were also the different mean gas compositions between core and surface funnels in the same pile.     

Optimum design of the entrance of a fishpond laterally to the main stream of an open channel

In this study, the optimum design of the entrance of a fishpond laterally to the main flow of an open channel was investigated numerically and experimentally. The flow characteristic measurements were realized with the PIV (particle image velocimetry) method. The mathematical simulations were based on the development of a two dimensional -mean in depthhydrodynamic model and a quasi three dimensional sediment transport model which includes processes of advection, diffusion, and settling of conservative suspended matter. The study was completed with the comparison of the final results of the mathematical models with the findings of the physical model revealing the hydrodynamic interaction and coupling between the main flow of the channel and the lateral reservoir—fishpond and leading to the optimum technical design of the system.     

Seasonality of Soil Erosion Under Mediterranean Conditions at the Alqueva Dam Watershed

The Alqueva reservoir created the largest artificial lake of Western Europe in 2010. Since then, the region has faced challenges due to land-use changes that may increase the risk of erosion and shorten the lifetime of the reservoir, increasing the need to promote land management sustainability. This paper investigates the aspect of seasonality of soil erosion using a comprehensive methodology that integrates the Revised Universal Soil Loss Equation (RUSLE) approach, geographic information systems, geostatistics, and remote-sensing. An experimental agro-silvo pastoral area (typical land-use) was used for the RUSLE factors update. The study confirmed the effect of seasonality on soil erosion rates under Mediterranean conditions. The highest rainfall erosivity values occurred during the autumn season (433.6 MJ mm ha^?1 h^?1), when vegetation cover is reduced after the long dry season. As a result, the autumn season showed the highest predicted erosion (9.9 t ha^?1), contributing 65 % of the total annual erosion. The predicted soil erosion for winter was low (1.1 t ha^?1) despite the high rainfall erosivity during that season (196.6 MJ mm ha^?1 h^?1). The predicted annual soil loss was 15.1 t ha^?1, and the sediment amount delivery was 4,314 × 10³ kg. Knowledge of seasonal variation would be essential to outline sustainable land management practices. This model will be integrated with World Overview of Conservation Approaches and Technologies methods to support decision-making in that watershed, and it will involve collaboration with both local people and governmental institutions.     

Particulates Generated from Combustion of Polymers (Plastics)

ABSTRACT

Yiannis A. Levendis is a professor in the Department of Mechanical, Industrial, and Manufacturing Engineering at Northeastern University. He holds a B.S. and an M.S. in mechanical engineering from the University of Michigan and a Ph.D. in environmental engineering from the California Institute of Technology. Brooke Shemwell is a graduate research assistant in the Department of Mechanical, Industrial, and Manufacturing Engineering at Northeastern University.

This is an experimental study on the characterization of particulate (soot) emissions from burning polymers. Emissions of polystyrene (PS), polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC) plastics were studied. Combustion took place in a laboratory-scale, electrically heated, drop-tube furnace at temperatures of 1300 and 1500 K, in air. The nominal bulk (global) equivalence ratio, φ, was varied in the range of 0.5-1.5, and the gas residence time in the nearly isothermal radiation zone of the furnace was ≈ 1 sec. The particulate emissions were size-classified at the exit of the furnace, using a multi-stage inertial particle impactor. Results showed that both the yields and the size distributions of the emitted soot were remarkably different for the five plastics burned. Soot yields increased with an increasing bulk equivalence ratio. Combustion of PS yielded the highest amounts of soot (most highly agglomerated), several times more than the rest of the polymers. More soot was emitted from PS at 1500 than at 1300 K. Substantial amounts of soot agglomerates were larger than 9 μm. At 1500 and 1300 K, 35 and 29% of the soot mass, respectively, was PM₂ (2 μm or smaller). Emissions from PE and PP were remarkably similar to each other. These polymers produced very low emissions at f< 0.5, but emissions increased drastically with f, and most of the soot was very fine (70-97% of the mass was PM₂, depending on f).

Emissions from the combustion of PMMA were comparatively low and were the least influenced by the bulk f, and 79–95% of the emissions were PM₂. Combustion of PVC yielded the lowest amounts of soot; moreover, only 13–34% of the mass was PM₂. On a comparative basis, at 1500 K, the following ranges of particulate yields were PM₂: 19–75 mg/g of PS, 8–36 mg/g of PE, 1.5–47 mg/g of PP, 11–20 mg/g of PMMA, and 2–8 mg/g of PVC, depending on f. These comparative results demonstrate that PS produces the highest amounts of fine particulates, followed by PP, PE, and PMMA, and then PVC. Burning these materials with excess oxygen drastically reduces the par-ticulate emissions of PE and PP, substantially reduces those of PS, and mildly reduces those of PMMA and PVC.     

An individual-oriented model for ecological risk assessment of wading birds

The contribution of certain contaminants to reproductive failure in many avian species has been an ongoing concern. Appropriate quantitative techniques have focused either on the individual organisms by providing explicit bioaccumulation dynamics or on whole ecosystems by looking at the fate of the contaminant but fail to make the necessary link via population dynamics of interacting individuals. We used the individual-oriented approach in an effort to quantify effects of chronic contaminant exposure on individual birds. This was made possible by the use of an object-oriented model, where individual birds are interacting objects, and their actions are implemented by passing to them appropriate messages. Using this modeling approach a breeding colony of Great Blue Herons (Ardea herodias) is simulated as an assemblage of interacting individuals whose daily actions (foraging, growth, feeding of the young) are simultaneously followed over short time intervals for a nesting season. Spatial distribution of the contaminants in prey resources is used on a cell by cell basis and their effects on certain behavior characteristics of adult birds (e.g. foraging efficiency, effects on flying efficiency, parental care) are taken into account. Results showed that sublethal effects could have a considerable effect on colony success. Appropriate selection of endpoints for risk assessment yields a variety of scenarios for colony success.     

Reducing surface water pollution through the assessment of the cost-effectiveness of BMPs at different spatial scales

Two kinds of agricultural Best Management Practices (BMPs) were examined with respect to cost-effectiveness (CE) in reducing sediment, nitrates-nitrogen (NO₃–N) and total phosphorus (TP) losses to surface waters of the Arachtos catchment in Western Greece. The establishment of filter strips at the edge of fields and a non-structural measure, namely fertilization reduction in alfalfa, combined with contour farming and zero-tillage in corn and reduction of animal numbers in pastureland, were evaluated. The Soil and Water Assessment Tool (SWAT) model was used as the non-point-source (NPS) estimator, while a simple economic component was developed estimating BMP implementation cost as the mean annual expenses needed to undertake and operate the practice for a 5-year period. After each BMP implementation, the ratio of their CE in reducing pollution was calculated for each Hydrologic Response Unit (HRU) separately, for each agricultural land use type entirely and for the whole catchment. The results at the HRU scale are presented comprehensively on a map, demonstrating the spatial differentiation of CE ratios across the catchment that enhances the identification of locations where each BMP is most advisable for implementation. Based on the analysis, a catchment management solution of affordable total cost would include the expensive measure of filter strips in corn and only in a small number of pastureland fields, in combination with the profitable measure of reducing fertilization to alfalfa fields. When examined for its impact on river loads at the outlet, the latter measure led to a 20 tn or 8% annual decrease of TP from the baseline with savings of 15€/kg of pollutant reduction. Filter strips in corn fields reduced annual sediments by 66 Ktn or 5%, NO₃–N by 71 tn or 9.5% and TP by 27 tn or 10%, with an additional cost of 3.1 €/tn, 3.3 €/kg and 8.1 €/kg of each pollutant respectively. The study concludes that considerable reductions of several pollutant types at the same time can be achieved, even at low total cost, by combining targeted BMP implementation strategies only in small parts of the catchment, also enabling policy makers to take local socio-economic constraints into consideration. The methodology and the results presented aim to facilitate decision making for a cost-effective management of diffuse pollution by enabling modelers and researchers to make rapid and reliable BMP cost estimations and thus being able to calculate their CE at the local level in order to identify the most suitable areas for their implementation.