Low Emission Rates Research Articles

Fuel Cell Durability Enhancement with Cerium Oxide under Combined Chemical and Mechanical Membrane Degradation

A CeO2 supported membrane electrode assembly (MEA) was fabricated by hot-pressing CeO2-coated electrodes and a PFSA ionomer membrane. Upon application of a combined chemical and mechanical accelerated stress test (AST), the CeO2 supported MEA showed six times longer lifetime and 40 times lower fluoride emission rate than a baseline MEA without cerium. The membrane in the CeO2 supported MEA effectively retained its original thickness and ductility despite the highly aggressive AST conditions. Most of the cerium applied on the anode migrated into the membrane and provided excellent mitigation of joint chemical and mechanical membrane degradation.

Assessment of WRF/Chem Simulated Vertical Distributions of Particulate Matter from the 2009 Minto Flats South Wildfire in Interior Alaska by CALIPSO Total Backscatter and Depolarization Measurements

This feasibility study examined whether total backscatter and depolarization measurements from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) in combination with sparse surface meteorological data and other information permitted qualitative assessment of simulated vertical and horizontal distributions of aerosols from wildfires over Interior Alaska. Comparisons between co-located WRF/Chem cross-sections and CALIPSO curtains showed temporal and spatial differences in smoke-plume height above ground, vertical and horizontal extension. Simple estimates of contributions of errors and processes elucidated that the different spatial and temporal resolution of model grid-cells and the lidar scan could provide offsets of the magnitude found in the comparison. The overestimation of 10 m wind speeds by on average 1.33 m&#183s&#451 contributed to the offset. Energy estimates suggested that the energy needed for permafrost thawing may contribute to discrepancies between simulated and CALIPSO indicated plume height. A sensitivity study with lower emission rates showed similar features. The study demonstrated that use of CALIPSO data in combination with data from other sources than air-quality networks could serve for identification of potential model shortcomings by assessment of magnitudes of error and process impacts.

Experimental evidence for specialized bird pollination in the endangered South African orchidSatyrium rhodanthumand analysis of associated floral traits

The bird pollination syndrome is characterized by red, unscented flowers with dilute nectar in long nectar tubes. However, the extent to which plants with such traits actually depend on birds for seed production is seldom determined experimentally, and traits such as colour and scent production are often assessed only subjectively. We documented bird pollination and quantified floral traits in the critically endangered Satyrium rhodanthum (Orchidaceae) from mistbelt grasslands in the summer-rainfall region of South Africa. Direct observations and motion trigger camera footage revealed amethyst sunbirds as the only pollinators, despite the presence of other potential pollinators. Experimental exclusion of sunbirds significantly reduced pollination and fruit set to near zero. Pollination success in naturally pollinated plants was close to 100% in one year, and fruit set varied from 23 to 64% in other years. Pollen transfer efficiency was 5.8%, which is lower than in related insect-pollinated species, probably due to a tendency of birds to wipe pollinaria from their beak. Flowers of S. rhodanthum only reflect light in the red range of the spectrum, and they produce only a few aliphatic and monoterpene scent compounds at comparatively low emission rates. Nectar volume and sugar concentration varied between 2.7 and 3.7 μL and 23.7 and 25.9%, respectively. We conclude that S. rhodanthum is highly specialized for pollination by sunbirds. Colour, scent and nectar characteristics differ from insect-pollinated Satyrium species and are consistent with those expected for bird-pollinated flowers, and may contribute to lack of visitation by other potential long-tongued pollinators. Habitat loss probably underlies the critically endangered conservation status of S. rhodanthum, but the specialization for pollination by a single bird species means that reproduction in this orchid is vulnerable to losses in surrounding communities of plants that subsidize the energetic requirements of sunbirds. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 177, 141–150.

Cold temperature and biodiesel fuel effects on speciated emissions of volatile organic compounds from diesel trucks.

Speciated volatile organic compounds (VOCs) were measured in diesel exhaust from three heavy-duty trucks equipped with modern aftertreatment technologies. Emissions testing was conducted on a chassis dynamometer at two ambient temperatures (-7 and 22 °C) operating on two fuels (ultra low sulfur diesel and 20% soy biodiesel blend) over three driving cycles: cold start, warm start and heavy-duty urban dynamometer driving cycle. VOCs were measured separately for each drive cycle. Carbonyls such as formaldehyde and acetaldehyde dominated VOC emissions, making up ∼ 72% of the sum of the speciated VOC emissions (∑VOCs) overall. Biodiesel use led to minor reductions in aromatics and variable changes in carbonyls. Cold temperature and cold start conditions caused dramatic enhancements in VOC emissions, mostly carbonyls, compared to the warmer temperature and other drive cycles, respectively. Different 2007+ aftertreatment technologies involving catalyst regeneration led to significant modifications of VOC emissions that were compound-specific and highly dependent on test conditions. A comparison of this work with emission rates from different diesel engines under various test conditions showed that these newer technologies resulted in lower emission rates of aromatic compounds. However, emissions of other toxic partial combustion products such as carbonyls were not reduced in the modern diesel vehicles tested.

Reducing CO2 emission from exhaust gases using molten carbonate fuel cells: a new approach

The aim of this study is to couple molten carbonate fuel cell (MCFC) stack with integrated gasification combined cycle fed by refinery residues, to remove CO2 from gas turbine exhaust gases that have CO2 emission rate of 14,200 ton/year. By applying multi-objective optimisation (MOO) using genetic algorithm, the optimal values of operating load and the corresponding values of objective functions are obtained. The MOO of the MCFC system regarding two scenarios is performed. The first scenario is minimisation of cost of electricity (COE) and CO2 emission rate. Objective functions of the second scenario are the same as in the first scenario while CO2 tax is taken into account. Results show that the second scenario has 29.5% lower average optimal COE and 2.5% lower average emission rate in comparison with the first scenario. A sensitivity analysis is also performed to study the effect of fuel price and CO2 tax variations on optimal solutions.

Comparison of Solid Waste Stabilization and Methane Emission from Anaerobic and Semi-Aerobic Landfills Operated in Tropical Condition

Leachate quality and methane emission from pilot-scale lysimeters operated under semi-aerobic and anaerobic conditions were monitored for 650 days. Two semi-aerobic lysimeters were filled with un-compacted and compacted municipal solid wastes whereas two anaerobic lysimeters containing compacted wastes were operated with leachate storage at 50% and 100% of waste height, respectively. Despite having high moisture in wastes and operating under tropical rainfall events, leachate stabilization in semi-aerobic lysimeters took place much faster resulting in BOD reduction by 90% within 60 days, significantly shorter than 180?210 days observed in anaerobic lysimeters. Nitrogen concentration in leachate from semi-aerobic lysimeter could be reduced by 90%. In term of gas emission, semi-aerobic lysimeter with un-compacted wastes had much lower methane emission rate of 2.8 g/m2/day compare to anaerobic lysimeters (62.6 g/m2/day) through seasonal fluctuation was observed. Nevertheless, semi-aerobic lysimeter with waste compaction has similar performance to anaerobic lysimeter.

The impact of image reconstruction bias on PET/CT 90Y dosimetry after radioembolization.

PET/CT imaging after radioembolization is a viable method for determining the posttreatment (90)Y distribution in the liver. Low true-to-random coincidence ratios in (90)Y PET studies limit the quantitative accuracy of these studies when reconstruction algorithms optimized for traditional PET imaging are used. This study examined these quantitative limitations and assessed the feasibility of generating radiation dosimetry maps in liver regions with high and low (90)Y concentrations. (90)Y PET images were collected on a PET/CT scanner and iteratively reconstructed with the vendor-supplied reconstruction algorithm. PET studies on a Jaszczak cylindric phantom were performed to determine quantitative accuracy and minimum detectable concentration (MDC). (90)Y and (18)F point-source studies were used to investigate the possible increase in detected random coincidence events due to bremsstrahlung photons. Retrospective quantitative analyses were performed on (90)Y PET/CT images obtained after 65 right or left hepatic artery radioembolizations in 59 patients. Quantitative image errors were determined by comparing the measured image activity with the assayed (90)Y activity. PET images were converted to dose maps through convolution with voxel S values generated using MCNPX, a Monte Carlo N-particle transport code system for multiparticle and high-energy applications. Tumor and parenchyma doses and potential bias based on measurements found below the MDC were recorded. Random coincidences were found to increase in (90)Y acquisitions, compared with (18)F acquisitions, at similar positron emission rates because of bremsstrahlung photons. Positive bias was observed in all images. Quantitative accuracy was achieved for phantom inserts above the MDC of 1 MBq/mL. The mean dose to viable tumors was 183.6 ± 156.5 Gy, with an average potential bias of 3.3 ± 6.4 Gy. The mean dose to the parenchyma was 97.1 ± 22.1 Gy, with an average potential bias of 8.9 ± 4.9 Gy. The low signal-to-noise ratio caused by low positron emission rates and high bremsstrahlung photon production resulted in a positive bias on (90)Y PET images reconstructed with conventional iterative algorithms. However, quantitative accuracy was good at high activity concentrations, such as those found in tumor volumes, allowing for adequate tumor (90)Y PET/CT dosimetry after radioembolization.

Gamma/neutron time-correlation for special nuclear material detection – Active stimulation of highly enriched uranium

The time-correlated pulse-height technique can distinguish multiplying (special nuclear material) from non-multiplying sources. The technique relies upon the measurement of correlated photon–neutron pairs using organic liquid scintillation detectors. For such interactions, the distribution of measured neutron recoil energy versus the time-of-flight difference between correlated photons and neutrons are imprinted with the fission chain dynamics of the source. The theoretical time-of-arrival assuming the photons and neutrons are created in the same fission is calculated. Correlated pairs with longer time-of-arrival indicate delays caused by self-induced fission chains in a multiplying source. For the specific circumstances of simulated measurements of 25.4kg of highly enriched uranium at 50cm source to detector distance, correlated pairs from fission chains can arrive upwards of 40ns later than correlated pairs with the same neutron energies from non-multiplying sources like 252Cf at the same source detector distance. The use of detectors with ns scale time resolution and the use of pulse digitization allows for the distinction of these events.This method has been used successfully in the past to measure a variety of plutonium-bearing samples. The particle transport code MCNPX-PoliMi has been used to simulate and validate these measurements as well. Due to the much lower signature emission rate of 235U, this technique has not yet been used to measure the presence of highly enriched uranium. In this work we therefore explore the use of the time-correlated pulse-height technique with the introduction of an interrogating neutron source to stimulate fission. The applicability of 252Cf, AmLi and a DD generator neutron sources is explored in a series of simulations. All three sources are viable options with their own pros and cons with the choice of appropriate source depending upon the intended application. The TCPH technique is envisioned as a viable measurement solution of special nuclear material in situations in which the presence of shielding material disqualifies the use of passive gamma spectroscopy or gamma spectroscopy reveals classified information on the special nuclear material’s isotopic composition.

Changes in floral bouquets from compound-specific responses to increasing temperatures.

We addressed the potential effects of changes in ambient temperature on the profiles of volatile emissions from flowers and tested whether warming could induce significant quantitative and qualitative changes in floral emissions, which would potentially interfere with plant-pollinator chemical communication. We measured the temperature responses of floral emissions of various common species of Mediterranean plants using dynamic headspace sampling and used GC-MS to identify and quantify the emitted terpenes. Floral emissions increased with temperature to an optimum and thereafter decreased. The responses to temperature modeled here predicted increases in the rates of floral terpene emission of 0.03-1.4-fold, depending on the species, in response to an increase of 1°C in the mean global ambient temperature. Under the warmest projections that predict a maximum increase of 5°C in the mean temperature of Mediterranean climates in the Northern Hemisphere by the end of the century, our models predicted increases in the rates of floral terpene emissions of 0.34-9.1-fold, depending on the species. The species with the lowest emission rates had the highest relative increases in floral terpene emissions with temperature increases of 1-5°C. The response of floral emissions to temperature differed among species and among different compounds within the species. Warming not only increased the rates of total emissions, but also changed the ratios among compounds that constituted the floral scents, i.e. increased the signal for pollinators, but also importantly altered the signal fidelity and probability of identification by pollinators, especially for specialists with a strong reliance on species-specific floral blends.

Impact of raw pig slurry and pig farming practices on physicochemical parameters and on atmospheric N2O and CH4 emissions of tropical soils, Uvéa Island (South Pacific)

Emissions of CH4 and N2O related to private pig farming under a tropical climate in Uvéa Island were studied in this paper. Physicochemical soil parameters such as nitrate, nitrite, ammonium, Kjeldahl nitrogen, total organic carbon, pH and moisture were measured. Gaseous soil emissions as well as physicochemical parameters were compared in two private pig farming strategies encountered on this island on two different soils (calcareous and ferralitic) in order to determine the best pig farming management: in small concrete pens or in large land pens. Ammonium levels were higher in control areas while nitrate and nitrite levels were higher in soils with pig slurry inputs, indicating that nitrification was the predominant process related to N2O emissions. Nitrate contents in soils near concrete pens were important (≥ 55 μg N/g) and can thus be a threat for the groundwater. For both pig farming strategies, N2O and CH4 fluxes can reach high levels up to 1 mg N/m(2)/h and 1 mg C/m(2)/h, respectively. CH4 emissions near concrete pens were very high (≥ 10.4 mg C/m(2)/h). Former land pens converted into agricultural land recover low N2O emission rates (≤ 0.03 mg N/m(2)/h), and methane uptake dominates. N2O emissions were related to nitrate content whereas CH4 emissions were found to be moisture dependent. As a result relating to the physicochemical parameters as well as to the gaseous emissions, we demonstrate that pig farming in large land pens is the best strategy for sustainable family pig breeding in Uvéa Islands and therefore in similar small tropical islands.

Measuring SO<sub>2</sub> ship emissions with an ultraviolet imaging camera

Abstract. Over the last few years fast-sampling ultraviolet (UV) imaging cameras have been developed for use in measuring SO2 emissions from industrial sources (e.g. power plants; typical emission rates ~ 1–10 kg s−1) and natural sources (e.g. volcanoes; typical emission rates ~ 10–100 kg s−1). Generally, measurements have been made from sources rich in SO2 with high concentrations and emission rates. In this work, for the first time, a UV camera has been used to measure the much lower concentrations and emission rates of SO2 (typical emission rates ~ 0.01–0.1 kg s−1) in the plumes from moving and stationary ships. Some innovations and trade-offs have been made so that estimates of the emission rates and path concentrations can be retrieved in real time. Field experiments were conducted at Kongsfjord in Ny Ålesund, Svalbard, where SO2 emissions from cruise ships were made, and at the port of Rotterdam, Netherlands, measuring emissions from more than 10 different container and cargo ships. In all cases SO2 path concentrations could be estimated and emission rates determined by measuring ship plume speeds simultaneously using the camera, or by using surface wind speed data from an independent source. Accuracies were compromised in some cases because of the presence of particulates in some ship emissions and the restriction of single-filter UV imagery, a requirement for fast-sampling (> 10 Hz) from a single camera. Despite the ease of use and ability to determine SO2 emission rates from the UV camera system, the limitation in accuracy and precision suggest that the system may only be used under rather ideal circumstances and that currently the technology needs further development to serve as a method to monitor ship emissions for regulatory purposes. A dual-camera system or a single, dual-filter camera is required in order to properly correct for the effects of particulates in ship plumes.

Isoprene emissions over Asia 1979–2012: impact of climate and land-use changes

Abstract. Due to the scarcity of observational constraints and the rapidly changing environment in East and Southeast Asia, isoprene emissions predicted by models are expected to bear substantial uncertainties. The aim of this study is to improve upon the existing bottom-up estimates, and to investigate the temporal evolution of the fluxes in Asia over 1979–2012. To this purpose, we calculate the hourly emissions at 0.5°×0.5° resolution using the MEGAN–MOHYCAN model driven by ECMWF ERA-Interim climatology. In order to remedy for known biases identified in previous studies, and to improve the simulation of interannual variability and trends in emissions, this study incorporates (i) changes in land use, including the rapid expansion of oil palms, (ii) meteorological variability according to ERA-Interim, (iii) long-term changes in solar radiation (dimming/brightening) constrained by surface network radiation measurements, and (iv) recent experimental evidence that South Asian tropical forests are much weaker isoprene emitters than previously assumed, and on the other hand, that oil palms have a strong isoprene emission capacity. These effects lead to a significant lowering (factor of 2) in the total isoprene fluxes over the studied domain, and to emission reductions reaching a factor of 3.5 in Southeast Asia. The bottom-up annual isoprene emissions for 2005 are estimated at 7.0, 4.8, 8.3, and 2.9 Tg in China, India, Indonesia and Malaysia, respectively. The isoprene flux anomaly over the whole domain and studied period is found to be strongly correlated with the Oceanic Niño Index (r = 0.73), with positive (negative) anomalies related to El Niño (La Niña) years. Changes in temperature and solar radiation are the major drivers of the interannual variability and trends in the emissions, except over semi-arid areas such as northwestern China, Pakistan and Kazakhstan, where soil moisture is by far the main cause of interannual emission changes. In our base simulation, annual positive flux trends of 0.2% and 0.52% throughout the entire period are found in Asia and China, respectively, related to a positive trend in temperature and solar radiation. The impact of oil palm expansion in Indonesia and Malaysia is to enhance the trends over that region, e.g., from 1.17% to 1.5% in 1979–2005 in Malaysia. A negative emission trend is derived in India (−0.4%), owing to the negative trend in solar radiation data associated with the strong dimming effect likely due to increasing aerosol loadings. The bottom-up emissions are compared to field campaign measurements in Borneo and South China and further evaluated against top-down isoprene emission estimates constrained by GOME-2/MetOp-A formaldehyde columns through 2007–2012. The satellite-based estimates appear to support our assumptions, and confirm the lower emission rate in tropical forests of Indonesia and Malaysia. Additional flux measurements are clearly needed to characterize the spatial variability of emission factors better. Finally, a decreasing trend in the inferred top-down Chinese emissions since 2007 is in line with recorded cooling in China after that year, thus suggesting that the satellite HCHO columns are able to capture climate-induced changes in emissions.

Emissions of CO2 and CH4 from sludge treatment reed beds depend on system management and sludge loading

Sludge treatment reed beds (STRB) are considered as eco-friendly and sustainable alternatives to conventional sludge treatment methods, although little is known about greenhouse gas emissions from such systems. We measured CO2 and CH4 emissions and substrate characteristics in a STRB, an occasionally loaded sludge depot (SD) and a natural reed wetland (NW). The aim was to compare (i) emissions among the sites in relation to substrate characteristics and (ii) emissions before and after sludge loading in the STRB. The STRB emitted twice as much CO2 (1200 mg m−2 h−1) as the SD, whereas the SD emitted four times more CH4 (2 mg m−2 h−1) than the STRB. The NW had the lowest emissions of both gases. The differences in gas emissions among the sites were primarily explained by differences in the availability of oxygen in the substrate. As a consequence of overloading and poor management, the SD had no vegetation and a poor dewatering capacity, which resulted in anaerobic conditions favoring CH4 emission. In contrast, the well-managed STRB had more aerobic conditions in the sludge residue resulting in low CH4 emission rates. We conclude that well-designed and well-managed STRBs have a low climate impact relative to conventional treatment alternatives, but that overloading and poor sludge management enhances the emissions of CH4.

Evolution of chemical and biological characterization during thermophilic composting of vegetable waste using rotary drum composter

Vegetable waste usually contains high levels of organic matter, moisture and nutrients that make the waste unsuitable for disposal in municipal landfills. Composting of vegetable waste is in practice by many urban local bodies, and therefore, it was composted along with cow dung and sawdust in a 550-L batch scale rotary drum composter. Four different trials of varying waste combinations of vegetable waste, cow dung and sawdust, i.e., trial 1 (5:4:1), trial 2 (6:2:1), trial 3 (7:2:1) and trial 4 (8:1:1) were composted by adding 10 kg of dry leaves as bulking agent with a total mass of 100 kg. With proper combinations of organic waste mix, a maximum temperature of 66.5 °C was observed in trial 1 and 61.4 °C in trial 2, when compared to other two trials with prolonged thermophilic period. Due to such elevated temperature, higher degradation was observed in trials 1 and 2 with inactivation of pathogens to considerable amounts. Furthermore, final compost had total nitrogen of 2.31 and 3.01 %, total phosphorous of 4.30 and 3.27 % and final carbon-to-nitrogen ratio of 15 and 12, in trials 1 and 2, respectively. Carbon dioxide evolution and oxygen uptake rate of compost samples was analyzed for its stability and was observed to reduce completely at the end of 20 days with lower emission rates.

Soft Ionization Chemical Analysis of Secondary Organic Aerosol from Green Leaf Volatiles Emitted by Turf Grass

Globally, biogenic volatile organic compound (BVOC) emissions contribute 90% of the overall VOC emissions. Green leaf volatiles (GLVs) are an important component of plant-derived BVOCs, including cis-3-hexenylacetate (CHA) and cis-3-hexen-1-ol (HXL), which are emitted by cut grass. In this study we describe secondary organic aerosol (SOA) formation from the ozonolysis of dominant GLVs, their mixtures and grass clippings. Near-infrared laser desorption/ionization aerosol mass spectrometry (NIR-LDI-AMS) was used for chemical analysis of the aerosol. The chemical profile of SOA generated from grass clippings was correlated with that from chemical standards of CHA and HXL. We found that SOA derived from HXL most closely approximated SOA from turf grass, in spite of the approximately 5× lower emission rate of HXL as compared to CHA. Ozonolysis of HXL results in formation of low volatility, higher molecular weight compounds, such as oligomers, and formation of ester-type linkages. This is in contrast to CHA, where the hydroperoxide channel is the dominant oxidation pathway, as oligomer formation is inhibited by the acetate functionality.

Trajectory sensitivity of the transient climate response to cumulative carbon emissions

The robustness of Transient Climate Response to cumulative Emissions (TCRE) is tested using an Earth System Model (Geophysical Fluid Dynamics Laboratory-ESM2G) forced with seven different constant rates of carbon emissions (2 GtC/yr to 25 GtC/yr), including low emission rates that have been largely unexplored in previous studies. We find the range of TCRE resulting from varying emission pathways to be 0.76 to 1.04°C/TtC. This range, however, is small compared to the uncertainty resulting from varying model physics across the Fifth Coupled Model Intercomparison Project ensemble. TCRE has a complex relationship with emission rates; TCRE is largest for both low (2 GtC/yr) and high (25 GtC/yr) emissions and smallest for present-day emissions (5–10 GtC/yr). Unforced climate variability hinders precise estimates of TCRE for periods shorter than 50 years for emission rates near or smaller than present day values. Even if carbon emissions would stop, the prior emissions pathways will affect the future climate responses.

Influence of Different Plant Species on Methane Emissions from Soil in a Restored Swiss Wetland

Plants are a major factor influencing methane emissions from wetlands, along with environmental parameters such as water table, temperature, pH, nutrients and soil carbon substrate. We conducted a field experiment to study how different plant species influence methane emissions from a wetland in Switzerland. The top 0.5 m of soil at this site had been removed five years earlier, leaving a substrate with very low methanogenic activity. We found a sixfold difference among plant species in their effect on methane emission rates: Molinia caerulea and Lysimachia vulgaris caused low emission rates, whereas Senecio paludosus, Carex flava, Juncus effusus and Typha latifolia caused relatively high rates. Centaurea jacea, Iris sibirica, and Carex davalliana caused intermediate rates. However, we found no effect of either plant biomass or plant functional groups – based on life form or productivity of the habitat – upon methane emission. Emissions were much lower than those usually reported in temperate wetlands, which we attribute to reduced concentrations of labile carbon following topsoil removal. Thus, unlike most wetland sites, methane production in this site was probably fuelled chiefly by root exudation from living plants and from root decay. We conclude that in most wetlands, where concentrations of labile carbon are much higher, these sources account for only a small proportion of the methane emitted. Our study confirms that plant species composition does influence methane emission from wetlands, and should be considered when developing measures to mitigate the greenhouse gas emissions.

Assessing the Soil Carbon, Biomass Production, and Nitrous Oxide Emission Impact of Corn Stover Management for Bioenergy Feedstock Production Using DAYCENT

Harvesting crop residue needs to be managed to protect agroecosystem health and productivity. DAYCENT, a process-based modeling tool, may be suited to accommodate region-specific factors and provide regional predictions for a broad array of agroecosystem impacts associated with corn stover harvest. Grain yield, soil C, and N2O emission data collected at Corn Stover Regional Partnership experimental sites were used to test DAYCENT performance modeling the impacts of corn stover removal. DAYCENT estimations of stover yields were correlated and reasonably accurate (adjusted r2 = 0.53, slope = 1.18, p 3-kg N2O-N ha−1 year−1. Overall, DAYCENT performed well at simulating stover yields and low N2O emission rates, reasonably well when simulating the effects of management practices on average grain yields and SOC change, and poorly when estimating high N2O emissions. These biases should be considered when DAYCENT is used as a decision support tool for recommending sustainable corn stover removal practices to advance bioenergy industry based on corn stover feedstock material.

Effectiveness of catechin and poly(ethylene glycol) at inhibiting the spontaneous combustion of coal

The effects of various combinations of catechin and poly(ethylene glycol) (PEG) concentrations on the inhibition of coal oxidation were studied. The oxidation behaviors of coal samples both with and without the additives were examined, based on measurements of cross point temperature, oxygen consumption during low temperature oxidation and carbon monoxide emission rates. The results demonstrate that an additive consisting of a combination of both catechin and PEG 200 is capable of inhibiting the oxidation process. In situ monitoring of the surfaces of coal samples during oxidation also indicated that these additives suppress coal oxidation by accelerating the formation of ether bonds. Accordingly, a suppression mechanism is proposed.

Forest Recovering and Soil Respiration Rate

This study was conducted to investigate the rate of soil respiration from a recovering forest of the tropics and its relationship with changes in environmental factorsafter years of deforestation. Soil respiration measurement was conducted using the continuous open flow chamber technique connected to a multi gas- handling unit and infrared gas analyser, while the forest biomass and soil properties were quantified using the Kjeldahl method and Walkley-black wet oxidation technique. The average means soil respiration rate were 341.23, 383.07, 340.30, 308.12, 286.07, 256.05 mg m -2 h -1 between June and December. Soil respiration in the month of July was significantly (p<0.01) higher compare to other months, with lower emission rate in December. Soil respiration exhibited a variation pattern that was similar to soil temperature pattern, the pattern varied monthly. Likewise, the forest carbon input and soil properties were found to be significantly correlated with soil respiration as they provide nutrients for microorganism to emit soil CO2. The remarkable soil CO2 emission from the recovering forest was attributed to changes in environmental factors as the forest is recovering from deforestation. The correlation and multiple linear regression model proved that environmental factors influenced the high rate of soil CO2 emission indicating a strong positive relationship (0.94; p<0.01). These results suggestthat forest recovering could still emit considerable percentages of soil CO2 due to the impact from deforestation which could have a great implication on environmental factors and the atmospheric carbon balance.