Bioethanol production from sugarcane and emissions of greenhouse gases – known and unknowns

Bioethanol production from sugarcane is discussed as an alternative energy source to reduce dependencies of regional economies on fossil fuels. Even though bioethanol production from sugarcane is considered to be a beneficial and cost‐effective greenhouse gas (GHG) mitigation strategy, it is still a matter of controversy due to insufficient information on the total GHG balance of this system. Aside from the necessity to account for the impact of land use change (LUC), soil N₂O emissions during sugarcane production and emissions of GHG due to preharvest burning may significantly impact the GHG balance. Based on a thorough literature review, we show that direct N₂O emissions from sugarcane fields due to nitrogen (N) fertilization result in an emission factor of 3.87±1.16% which is much higher than suggested by IPCC (1%). N₂O emissions from N fertilization accounted for 40% of the total GHG emissions from ethanol–sugarcane production, with an additional 17% from trash burning. If LUC‐related GHG emissions are considered, the total GHG balance turns negative mainly due to vegetation carbon losses. Our study also shows that major gaps in knowledge still exist about GHG sources related to agricultural management during sugarcane production, e.g. effects of irrigation, vinasse and filter cake application. Therefore, more studies are needed to assess if bioethanol from sugarcane is a viable option to reduce energy‐related GHG emissions.     

Release of metals from polluted sediments in a shallow lake: quantifying resuspension

The contribution of erosion of bed sediment to the load of metals leaving Lake Ketelmeer, a shallow lake in the Netherlands fed by the IJssel branch of the River Rhine, is reported. Transport of suspended matter and associated trace metals was measured using both centrifuges and sediment traps at several locations in the lake. Mass balances of suspended matter and heavy metals were calculated using data from these field measurements.Metal/scandium-ratios were used to identify the source of the suspended matter in the lake. Since the bed sediment is more polluted than the suspended sediment entering the lake, higher metal/scandium-ratios were found for bottom sediment in the lake compared with those for suspended matter entering the lake from the River IJssel. Using the metal/scadium-ratio in suspended matter from the lake, it was calculated that bottom sediments made up 43% of the suspended matter leaving the lake. This implies an erosion flux of bottom sediment of 16 g m^–2 d^–1. For cadmium, mercury, chromium and zinc, this erosion process accounts for more than 50% of the pollutant load leaving Lake Ketelmeer and entering Lake IJsselmeer.     

Characterization of a fungal strain isolated from a polyphenol polluted site

A group of fungal strains were isolated from a polyphenol polluted soil, taken from an olive oil processing plant in Attica, Greece. The fungi were tested for their ability to decolorize a polyaromatic dye Poly R-478, which was used as a model compound to test their ligninolytic activities. The strain K1.1 decolorized efficiently the dye on agar plates and was further studied. PCR amplification of the internal transcribed spacer (ITS) region of the ribosomal RNA genes from the genomic DNA isolated from mycelium grown in liquid culture resulted in amplified fragments. Via BLASTN search, the length of a 773 base pairs was identified as the basidiomycetes Coprinellus xanthothrix. The growth rates and the tolerance of the fungus were compared on solid media, containing four different concentrations of pentachlorophenol. Extracellular enzyme activities (lignin peroxidase, manganese peroxidase and laccase) were determined in defined liquid medium. The isolate expressed laccase and manganese peroxidase but not lignin peroxidase. The removal of the dye was also estimated in liquid medium. The fungus showed biosorption and biotransformation as removal mechanisms.     

Potential applications of the oxidoreductive enzymes in the decolorization and detoxification of textile and other synthetic dyes from polluted water: a review

Recently, the enzymatic approach has attracted much interest in the decolorization/degradation of textile and other industrially important dyes from wastewater as an alternative strategy to conventional chemical, physical and biological treatments, which pose serious limitations. Enzymatic treatment is very useful due to the action of enzymes on pollutants even when they are present in very dilute solutions and recalcitrant to the action of various microbes participating in the degradation of dyes. The potential of the enzymes (peroxidases, manganese peroxidases, lignin peroxidases, laccases, microperoxidase-11, polyphenol oxidases, and azoreductases) has been exploited in the decolorization and degradation of dyes. Some of the recalcitrant dyes were not degraded/decolorized in the presence of such enzymes. The addition of certain redox mediators enhanced the range of substrates and efficiency of degradation of the recalcitrant compounds. Several redox mediators have been reported in the literature, but very few of them are frequently used (e.g., 1-hydroxybenzotriazole, veratryl alcohol, violuric acid, 2-methoxy-phenothiazone). Soluble enzymes cannot be exploited at the large scale due to limitations such as stability and reusability. Therefore, the use of immobilized enzymes has significant advantages over soluble enzymes. In the near future, technology based on the enzymatic treatment of dyes present in the industrial effluents/wastewater will play a vital role. Treatment of wastewater on a large scale will also be possible by using reactors containing immobilized enzymes.     

Recovery from training: a brief review: brief review

Athletes spend a much greater proportion of their time recovering than they do in training. Yet, much attention has been given to training with very little investigation of recovery. The purpose of this review is to stimulate further research into this vital area of training. Recovery can be categorized in three terms: i) immediate recovery between exertions; ii) short-term recovery between repeats (e.g., between resistance sets or interval bouts); and iii) training recovery between workouts. The focus of this review is training recovery. Full training recovery is essential to optimal performance and improvement. This review includes an examination of extant research on recovery and a very brief review of some potential modalities and techniques for hastening recovery and the time course of recovery and responses to some treatments. Measures of recovery and practical considerations are discussed briefly. Much research is needed in this area, but there are obstacles to high quality research. Attention must be given to key issues in research on recovery, especially the individual response to recovery treatments.     

Biodegradation of alkylpyridines by bacteria isolated from a polluted subsurface

Ten bacterial strains were isolated from alkylpyridine polluted sediments 7.6 m below the surface. These strains were able to degrade 11 different alkylpyridine isomers. Degradation rates depended on number and position of the alkyl group. Isomers with an alkyl group at position 3 were more resistant to microbial attack. Of the 10 strains, 6 isolates were selected for detailed study. These isolates mineralized the isomers to CO2, NH4+, and biomass. All strains were gram-negative rods with a strict aerobic metabolism. Characterization of physiological and biochemical properties revealed similarity between strains. Eeach strain however, had a limited substrate range which enabled it to degrade no more than 2 to 3 compounds of the 14 alkylpyridine isomers tested. Examination of the genetic variability among cultures with the randomly amplified polymorphic DNA technique revealed high levels of genomic DNA polymorphism. The highest similarity between 2 strains (0.653) was observed between 2-picoline and 3-picoline degrading cultures. The molecular basis of the differences in substrate specificity is under investigation.     

Biodegradation of alkylpyridines by bacteria isolated from a polluted subsurface

Ten bacterial strains were isolated fromalkylpyridine polluted sediments 7.6 m below thesurface. These strains were able to degrade 11different alkylpyridine isomers. Degradation ratesdepended on number and position of the alkyl group. Isomers with an alkyl group at position 3 were moreresistant to microbial attack. Of the 10 strains, 6isolates were selected for detailed study. Theseisolates mineralized the isomers to CO₂,NH₄ ⁺, and biomass. All strains weregram-negative rods with a strict aerobic metabolism. Characterization of physiological and biochemicalproperties revealed similarity between strains. Eeachstrain however, had a limited substrate range whichenabled it to degrade no more than 2 to 3 compounds ofthe 14 alkylpyridine isomers tested. Examination ofthe genetic variability among cultures with therandomly amplified polymorphic DNA technique revealedhigh levels of genomic DNA polymorphism. The highestsimilarity between 2 strains (0.653) was observedbetween 2-picoline and 3-picoline degrading cultures. The molecular basis of the differences in substratespecificity is under investigation.     

我国养殖水体N2O排放特征及其影响因素研究进展

养殖水体作为不可忽视的温室气体排放源,已引起社会广泛关注。本文通过文献综述分析了国内养殖水体N₂O溶存浓度、饱和度及排放通量的时空分布特征,并结合N₂O产生机制探讨了养殖水体N2O排放的影响因素。我国养殖水体N₂O介于饱和与过饱和状态,水-气界面排放通量范围为-9.82×10^-3~143.25×10^-3mg·m^-2·h^-1,养殖水体成为N₂O的重要排放源;空间变异特征表现为南方地区的排放通量显著高于北方地区,北方地区养殖水体N2O排放通量整体高于本区自然水体,而南方地区相反;从时间变化特征看,各养殖塘排放通量变化规律较为相似,大致表现为养殖中期排放量最高,养殖末期和养殖初期较低;季节变化上,夏季最高、冬春季较低。养殖水体N₂O的产生机制与其他水生生态系统相似,主要为硝化和反硝化作用,影响养殖水体N₂O在排放的因素除温度、pH、营养盐、盐度、叶绿素a等环境因素外,还与曝气活动、饵料投放、排水活动和养殖种类等人为因素有关。     

High incidence of selenite-resistant bacteria from a site polluted with selenium

The level of selenium-resistant bacteria in water, algal mats, and sediment from Kesterson reservoir, Calif., a site with known selenium pollution, was compared with that in nearby Volta reservoir, a site with low selenium levels. A high percentage (greater than 50%) of all isolates from the Kesterson samples were resistant to 10 mM selenite. In contrast, only a small percentage of the Volta isolates were resistant to this level of selenite. The identity of some selenite-resistant isolates and MICs of selenite, selenate, arsenate, tellurite, and tellurate were determined.     

Reduction of dioxin emissions from thermal waste treatment plants: a brief survey

Since 1977 dioxins were detected in fly ashes from waste incineration plants; this class of compounds is of major importance concerning the acceptance of this technology. Extended research and development revealed in short time the main formation mechanism of dioxins, the importance of good combustion control, the influence of halogens and sulphur, and paved the way for strategies for minimisation of formation, and efficient abatement. The main steps in this development as well as the current situation are described.     

Mutagenicity of emissions from a natural gas fueled truck

Concern about the potential health risks of particulate exhaust emissions from diesel-fueled vehicles has led regulatory agencies to foster the use of natural gas fueled heavy duty vehicles. However, the potential health risks of particulate exhaust emissions from natural gas fueled vehicles have not been well-studied. The present study investigated the mutagenicity of particulate exhaust emissions from a natural gas fueled refuse truck currently in-service. Organic solvent extracts of exhaust particulate emissions from the natural gas fueled truck were positive in both Salmonella tester strains TA98 and TA100 in the presence and absence of S-9. The maximum mutagenic responses ranged from 7-fold in the TA100 strain to 87-fold in the TA98 strain when compared to negative controls. Our results show that current in-service natural gas fueled heavy duty trucks have particulate exhaust emissions that possess mutagenic activity. This finding requires follow-up studies to develop a database on natural gas fueled vehicles for comparison with data on diesel-fueled vehicles to aid in making decisions on use of alternative fuels to reduce air pollution health risks.     

Seasonal variation of methane emissions from a temperate swamp

Methane flux measurements were made at four sites in a freshwater temperate swamp over the 13 month period of April 1985 through May 1986. Emissions were highly variable both between sites and over time at any one site. Ebullition from sediments was an important component of methane release. Although release of methane through bubbling occurred in only 19% of the measurements made between April and June 1985, when instrumentation allowed us to separate diffusive and bubble fluxes, ebullition accounted for 34% of the total flux during this period. Methane release rates showed a strong seasonal variation, with highest emission rates observed in early spring and again in late summer, which was associated with changes in plant growth and physiology. Emission rates were partially correlated with sediment temperature, but the relationship was not straightforward, and resembled a step function. Emissions responded strongly to temperature change through the range of 10–16°C. At winter sediment temperatures between 4–9°C, CH₄ flux continued at low rates (0–28 mg CH₄ m^–2d^–1; average = 7.9 mg CH₄m^–2d^–1) and appeared insensitive to changes in sediment temperature. Annual methane emission from three constantly flooded sites (mean water depth = 35 cm) was 43.7 +/- 7.8 gm^–2 (standard error); annual flux from a bank site was 41.4 +/- 20.5 gm^–2. A comparison of flux measurements from fresh and saline wetlands in the immediate area of Newport News Swamp emphasizes the importance of edaphic factors in controlling flux.     

N2O emissions from agricultural lands: a synthesis of simulation approaches

Nitrous oxide (N₂O) is primarily produced by the microbially-mediated nitrification and denitrification processes in soils. It is influenced by a suite of climate (i.e. temperature and rainfall) and soil (physical and chemical) variables, interacting soil and plant nitrogen (N) transformations (either competing or supplying substrates) as well as land management practices. It is not surprising that N₂O emissions are highly variable both spatially and temporally. Computer simulation models, which can integrate all of these variables, are required for the complex task of providing quantitative determinations of N₂O emissions. Numerous simulation models have been developed to predict N₂O production. Each model has its own philosophy in constructing simulation components as well as performance strengths. The models range from those that attempt to comprehensively simulate all soil processes to more empirical approaches requiring minimal input data. These N₂O simulation models can be classified into three categories: laboratory, field and regional/global levels. Process-based field-scale N₂O simulation models, which simulate whole agroecosystems and can be used to develop N₂O mitigation measures, are the most widely used. The current challenge is how to scale up the relatively more robust field-scale model to catchment, regional and national scales. This paper reviews the development history, main construction components, strengths, limitations and applications of N₂O emissions models, which have been published in the literature. The three scale levels are considered and the current knowledge gaps and challenges in modelling N₂O emissions from soils are discussed.     

Hybrid Mn-peroxidases from basidiomycetes: a review

The Mn-peroxidase from the fungus Panus tigrinus 8/18 is a hybrid enzyme. It catalyzes both Mn2+-dependent and Mn2+-independent oxidation of organic substrates. The spectral properties of intermediates and the pathway of the catalytic cycle are typical of hybrid Mn-peroxidases. The enzyme catalyzes the "oxidase" reaction (NADH oxidation) without peroxide and with the presence of Mn2+, which takes part in hydrogen peroxide production via Mn3+ and preserves the enzyme from inactivation. With the presence of organic mediators, the hybrid Mn-peroxidase oxidizes nonphenolic compounds: aromatic alcohols and a nonphenolic lignin model compound. The degree of conversion of 2,4,6-trichlorophenol is higher with the presence of l-hydroxybenzotriazole.     

Dichloromethane removal from waste gases with a trickle-bed bioreactor

A 66 dm³ trickle-bed bioreactor was constructed to assess the possibilities of eliminating dichloromethane from industrial waste gases. The trickle-bed bioreactor was filled with a randomly-stacked polypropylene packing material over which a liquid phase was circulated. The pH of the circulating liquid was externally controlled at a value of 7 and the temperature was maintained at 25 °C. The packing material was very quickly covered by a dichloromethane-degrading biofilm which thrived on the dichloromethane supplied via the gas phase. The biological system was very stable and not sensitive to fluctuations in the dichloromethane supply. Removal of dichloromethane from synthetic waste gas was possible down to concentrations well below the maximal allowable concentration of 150mg/m³ required by West-German law for gaseous emissions. At higher dichloromethane concentrations specific dichloromethane degradation rates of 200 g h^–1 m^–3 were possible. At very low inlet concentrations, dichloromethane elimination was completely mass transfer limited.The gas-phase mixing could be described by a series of 10 to 7 identical ideally-mixed tanks for superficial gas velocities ranging from 150 to 450 m/h. Dichloromethane elimination with the tricklebed bioreactor was modelled using an overall mass-transfer coefficient that was dependent on the gas and liquid velocities. Masstransfer resistance within the biofilm was also accounted for. Using the model, elimination efficiencies were predicted which were very close to the experimentally observed values.     

Bioremediation of MTBE: a review from a practical perspective

The addition of methyl tert-butyl ether (MTBE) to gasoline has resulted in public uncertainty regarding the continued reliance on biological processes for gasoline remediation. Despite this concern, researchers have shown that MTBE can be effectively degraded in the laboratory under aerobic conditions using pure and mixed cultures with half-lives ranging from 0.04 to 29 days. Ex-situ aerobic fixed-film and aerobic suspended growth bioreactor studies have demonstrated decreases in MTBE concentrations of 83% and 96% with hydraulic residence times of 0.3 hrs and 3 days, respectively. In microcosm and field studies, aerobic biodegradation half-lives range from 2 to 693 days. These half-lives have been shown to decrease with increasing dissolved oxygen concentrations and, in some cases, with the addition of exogenous MTBE-degraders. MTBE concentrations have also been observed to decrease under anaerobic conditions; however, these rates are not as well defined. Several detailed field case studies describing the use of ex-situ reactors, natural attenuation, and bioaugmentation are presented in this paper and demonstrate the potential for successful remediation of MTBE-contaminated aquifers. In conclusion, a substantial amount of literature is available which demonstratesthat the in-situ biodegradation of MTBE is contingent on achieving aerobic conditions in the contaminated aquifer.