MBM fuel feeding system design and evaluation for FBG pilot plant

A biomass fuel feeding system has been designed, constructed and evaluated for a fluidized bed gasifier (FBG) pilot plant at the University of Saskatchewan (Saskatoon, SK, Canada). The system was designed for meat and bone meal (MBM) to be injected into the gasifier at a mass flow-rate range of 1-5 g/s. The designed system consists of two stages of screw conveyors, including a metering stage which controlled the flow-rate of fuel, a rotary airlock and an injection conveyor stage, which delivered that fuel at a consistent rate to the FBG. The rotary airlock which was placed between these conveyors, proved unable to maintain a pressure seal, thus the entire conveying system was sealed and pressurized. A pneumatic injection nozzle was also fabricated, tested and fitted to the end of the injection conveyor for direct injection and dispersal into the fluidized bed. The 150 mm metering screw conveyor was shown to effectively control the mass output rate of the system, across a fuel output range of 1-25 g/s, while the addition of the 50mm injection screw conveyor reduced the irregularity (error) of the system output rate from 47% to 15%. Although material plugging was found to be an issue in the inlet hopper to the injection conveyor, the addition of air sparging ports and a system to pulse air into those ports was found to successfully eliminate this issue. The addition of the pneumatic injection nozzle reduced the output irregularity further to 13%, with an air supply of 50 slpm as the minimum air supply to drive this injector. After commissioning of this final system to the FBG reactor, the injection nozzle was found to plug with char however, and was subsequently removed from the system. Final operation of the reactor continues satisfactorily with the two screw conveyors operating at matching pressure with the fluidized bed, with the output rate of the system estimated based on system characteristic equations, and confirmed by static weight measurements made before and after testing. The error rate by this method is reported to be approximately 10%, which is slightly better than the estimated error rate of 15% for the conveyor system. The reliability of this measurement prediction method relies upon the relative consistency of the physical properties of MBM with respect to its bulk density and feeding characteristics.     

The solar transformity of petroleum fuels

Petroleum fuels are the primary energy basis for transportation and industry. They are almost always an important input to the economic and social activities of humanity. Emergy analyses require accurate estimates with specified uncertainty for the transformities of major energy and material inputs to economic and environmental systems. In this study, the oil refining processes in Italy and the United States were examined to estimate the transformity and specific emergy of petroleum derivatives. Based on our assumptions that petroleum derivatives are splits of a complex hydrocarbon mixture and that the emergy is split based on the fraction of energy in a product, we estimated that the transformity of petroleum derivatives is 65,826 sej/J ± 1.4% relative to the 9.26E+24 sej/year planetary baseline. Estimates of the specific emergies of the various liquid fuels from Italian and U.S. refineries are within 2% of one another and the relationship of particular values varies with the refinery design. Our average transformity is only 1.7% larger than the current estimate for petroleum fuels determined by back calculation, confirming the accuracy of this transformity in existing emergy analyses. The model uncertainty between using energy or mass to determine how emergy is split was less that 2% in the estimate of both the transformity and specific emergy of liquid fuels, but larger for solid and gaseous products. This study is a contribution to strengthen the emergy methodology, providing data that can be useful in the analysis of many human activities.     

Chlorobiphenyl contaminants at Pladda and Garroch Head in the Firth of Clyde following the cessation of sewage sludge dumping

Sewage sludge dumping at Garroch Head in the Firth of Clyde ceased on 31 December 1998. Eighteen of the 209 chlorinated biphenyls (CBs) were measured in plaice livers, collected in 1999 and 2000, from the former Garroch Head dump site. Samples were also obtained from Pladda, a site reasonably remote from the former dump site but also in the Clyde, in 1999 only. These results were compared to the CB concentrations in plaice livers collected between 1992 and 1998 from Garroch Head and Pladda. Additional samples were also taken from a clean reference site, close to Colonsay. Concentrations of the congeners in the livers of fish caught at the former Garroch Head dump site in 1999 were marginally higher than those from Pladda, with a mean CB concentration of 1861 microg kg(-1) lipid in the Garroch Head plaice livers and 1725 microg kg(-1) lipid for the sample from Pladda. The mean CB concentration in the 2000 Garroch Head samples was 2253 microg kg(-1) lipid. CB concentration in plaice livers from Colonsay were lower than both the Pladda and Garroch Head fish, with plaice livers from Colonsay giving a mean CB concentration of 1076 microg kg(-1) lipid in 1999 and 345.1 microg kg(-1) lipid in 2000. The data was evaluated using principal component analysis (PCA). Pattern analysis was undertaken by normalising to the recalcitrant CB 153. There was an indication that the CB pattern has changed since the cessation of dumping with the proportion of tri- and tetra-chlorinated CBs being lower in plaice from Garroch Head than in previous years.     

Isotopic composition and origin of uranium and plutonium in selected soil samples collected in Kosovo

Soil samples collected from locations in Kosovo where depleted uranium (DU) ammunition was expended during the 1999 Balkan conflict were analysed for uranium and plutonium isotopes content (234U, 235U, 236U, 238U, 238Pu, (239 + 240)Pu). The analyses were conducted using gamma spectrometry (235U, 238U), alpha spectrometry (238Pu, (239 + 240)Pu), inductively coupled plasma-mass spectrometry (ICP-MS) (234U, 235U, 236U, 238U) and accelerator mass spectrometry (AMS) (236U)). The results indicated that whenever the U concentration exceeded the normal environmental values (approximately 2 to 3 mg/kg) the increase was due to DU contamination. 236U was also present in the released DU at a constant ratio of 236U (mg/kg)/238U (mg/kg) = 2.6 x 10(-5), indicating that the DU used in the ammunition was from a batch that had been irradiated and then reprocessed. The plutonium concentration in the soil (undisturbed) was about 1 Bq/kg and, on the basis of the measured 238Pu/(239 + 240)Pu, could be entirely attributed to the fallout of the nuclear weapon tests of the 1960s (no appreciable contribution from DU).     

Crop residue removal and fertilizer N: Effects on soil organic carbon in a long-term crop rotation experiment on a Udic Boroll

Biofuels can be produced by converting cellulose in crop residues to ethanol. This has recently been viewed as a potential supplement to non-renewable energy sources, especially in the Americas. A 50-yr field experiment was analyzed to determine the influence of (i) removing approximately 22% of the above-ground wheat (Triticum aestivum L.) residue each crop year, and (ii) N and P fertilization on soil carbon (C) in the top 15 cm depth of a fallow–wheat–wheat (F–W–W) rotation. The study was conducted from 1958 to 2007 on a clay soil, at Indian Head in sub-humid southeast Saskatchewan, Canada. Soil C concentrations and bulk densities were measured in the 0–7.5 and 7.5–15 cm depths in 1987, 1996 and 2007 and soil C changes were related to C inputs estimated from straw and root yields calculated from regressions relating these to grain yields. Two soil organic matter models [the Campbell model and the Introductory Carbon Balance Model (ICBM)] were also used to simulate and predict the effects of the treatments on soil C change over time, and to estimate likely soil C change if 50% or 95% of above-ground residues were harvested each crop year. Crop residue removal reduced cumulative C inputs from straw and roots over the 50-yr experiment by only 13%, and this did not significantly (P > 0.05) reduce soil C throughout the experiment duration. However, after 50 yr of applying N fertilizer at recommended rates, soil C increased significantly by about 3 Mg ha⁻¹ compared to the non-fertilized treatment. The simulated effect of removing 50% and 95% of the above-ground residues suggested that removing 50% of the straw would likely have a detectable effect on the soil C, while removing 95% of the straw certainly would. Measurements and model simulations suggest that adoption of no-tillage without proper fertilization will not increase soil C. Although it appears that a modest amount of residue may be safely removed from these Udic Borolls (Black Chernozems) without a measurable effect on soil C, this would only be feasible if accompanied by appropriate fertility management.     

Microbial indicators of heavy metal contamination in urban and rural soils

Urban soils and especially their microbiology have been a neglected area of study. In this paper, we report on microbial properties of urban soils compared to rural soils of similar lithogenic origin in the vicinity of Aberdeen city. Significant differences in basal respiration rates, microbial biomass and ecophysiological parameters were found in urban soils compared to rural soils. Analysis of community level physiological profiles (CLPP) of micro-organisms showed they consumed C sources faster in urban soils to maintain the same level activity as those in rural soils. Cu, Pb, Zn and Ni were the principal elements that had accumulated in urban soils compared with their rural counterparts with Pb being the most significant metal to distinguish urban soils from rural soils. Sequential extraction showed the final residue after extraction was normally the highest proportion except for Pb, for which the hydroxylamine-hydrochloride extractable Pb was the largest part. Acetic acid extractable fraction of Cd, Cu, Ni, Pb and Zn were higher in urban soils and aqua regia extractable fraction were lower suggesting an elevated availability of heavy metals in urban soils. Correlation analyses between different microbial indicators (basal respiration, biomass-C, and sole C source tests) and heavy metal fractions indicated that basal respiration was negatively correlated with soil Cd, Cu, Ni and Zn inputs while soil microbial biomass was only significantly correlated with Pb. However, both exchangeable and iron- and manganese-bound Ni fractions were mostly responsible for shift of the soil microbial community level physiological profiles (sole C source tests). These data suggest soil microbial indicators can be useful indicators of pollutant heavy metal stress on the health of urban soils.     

Characteristics of Composition B particles from blow-in-place detonations

We sampled residues from high-order and low-order blow-in-place detonations of mortars and projectiles filled with Composition B (Comp B), a TNT and RDX mixture. Our goals were to (1) characterize the types of explosive particles, (2) estimate the explosive 'footprint' for different munitions, and (3) estimate the mass of Comp B remaining after each detonation. The aerial deposition of Comp B particles helps estimate how large of an area is contaminated by a low-order detonation and how best to sample residue resulting from different rounds. We found that the high-order detonations deposited microgram to milligram quantities whereas the low-order detonations deposited gram quantities of Comp B. For the high-order detonations the concentration of Comp B in the residue decreased as a function of distance from the blast. The low-order tests scattered centimeter-sized chunks and millimeter-sized or smaller particles of Comp B. The chunks were randomly scattered whereas the number of millimeter-sized particles decreased with distance from the detonation. For both high- and low-order detonations we found that the smaller munitions deposited less Comp B than the larger munitions and deposited it closer to the detonation point.     

Miniaturized test system for soil respiration induced by volatile pollutants

A miniaturized method based on 96-well microtitre plates was developed and used to study respiration in pristine and contaminated soils following addition of volatile substrates. Small soil samples were exposed to fuel components, which were volatilized from spatially separate reservoirs of 2,2,4,4,6,8,8-heptamethylnonane (HMN) as an organic carrier. Respiration was determined as CO(2) production by means of a pH-indicator and bicarbonate-containing agar, or as (14)CO(2) evolution from (14)C-labelled substrates. Substrate concentrations inducing maximum microbial activity or inhibition were determined and CO(2) production profiles examined by multivariate analysis. When high concentrations of fuel components were applied, distinction of hydrocarbon exposed soils from unexposed soil was achieved within 6 h of incubation. With low concentrations, adequate distinction was achieved after 24 h, probably as a result of community adaptation. Nutrient limitation was identified with the (14)C method for toluene, and the optimal N and P amendment determined. Further potential applications of this rapid and inexpensive method are outlined.