Landfill Gas To Energy Incentives And Benefits

Municipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50-60%) and carbon dioxide (40-50%). Although LFG poses a threat to the environment, if managed properly it is a valuable energy resource due to the methane content. Currently there are over 550 active LFG to energy (LFGTE) facilities in the US, producing renewable energy from LFG. A major challenge in designing/operating a LFGTE facility is the uncertainty in LFG generation rate predictions. LFG generation rates are currently estimated using models that are dependent upon the waste disposal history, moisture content, cover type, and gas collection system, which are associated with significant uncertainties. The objectives of this research were to: Evaluate various approaches of estimating LFG generation and to quantify the uncertainty of the model outcomes based on case-study analysis, Present a methodology to predict long-term LFGTE potential under various operating practices on a regional scale, and Investigate costs and benefits of emitting vs. collecting LFG emissions with regards to operation strategies and regulations. iii The first-order empirical model appeared to be insensitive to the approach taken in quantifying the model parameters, suggesting that the model may be inadequate to accurately describe LFG generation and collection. The uncertainty values for the model were, in general, at their lowest within five years after waste placement ended. Because of the exponential nature, the uncertainty increased as LFG generation declined to low values decades after the end of waste placement. A methodology was presented to estimate LFGTE potential on a regional scale over a 25-year timeframe with consideration of modeling uncertainties. The methodology was demonstrated for the US state of Florida, and showed that Florida could increase the annual LFGTE production by more than threefold by 2035 through installation of LFGTE facilities at all landfills. Results showed that diverting food waste could significantly reduce fugitive LFG emissions, while having minimal effect on the LFGTE potential. Estimates showed that with enhanced landfill operation and energy production practices, LFGTE power density could be comparable to technologies such as wind, tidal, and geothermal. More aggressive operations must be considered to avoid fugitive LFG emissions, which could significantly affect the economic viability of landfills. With little economic motivation for US landfill owners to voluntarily reduce fugitive emissions, regulations are necessary to increase the cost of emitting GHGs. In light of the recent economic recession, it is not likely that a carbon tax will be established; while a carbon trading program will enforce emission caps and provide a tool to offset some costs and improve emission-reduction systems. Immediate action establishing a iv US carbon trading market with carbon credit pricing and trading supervised by the federal government may be the solution. Costs of achieving high lifetime LFG collection efficiencies are unlikely to be covered with revenues from tipping fee, electricity sales, tax credits, or carbon credit trading. Under scenarios of highly regulated LFG emissions, sustainable landfilling will require research, development, and application of technologies to reduce the marginal abatement cost, including: Diverting rapidly decomposable waste to alternative treatment methods, Reducing fugitive emissions through usage daily/intermediate covers with high oxidation potential, Increasing the lifetime LFG collection efficiency, and Increasing LFG energy value – for instance by producing high-methane gas through biologically altering the LFG generation pathwa

Estimation of coliform contamination rate and impact of environmental factor on bacterial quality of tube well water supplies in Khorramdarreh County, Iran

In this study, the presence of fecal coliforms in tube wells of Khorramdarreh County, Iran, and impact of environmental factors on quantity and quality of these organisms were evaluated. In a cross-sectional survey, 76 tube well water samples from March to September 2010 were tested to determine presence of fecal coliforms, by measuring the most probable number (MPN), and identification of three enteric bacteria namely, Escherichia coli, Klebsiella sp. and Salmonella sp. Out of 76 wells, 24 (31.57%) and 25 (32.89%) wells showed presence of fecal coliforms, during rainy and dry seasons, respectively. In contrast to seasonal changes, depth of the wells showed significant correlation with type of isolated bacterial indices (P = 0.0005). On the other hand, depth of the well and seasonal variations did not show any significant correlation with fecal coliform contamination rate. The level of bacterial contamination of tube wells, in terms of presence of fecal coliforms is alarming. This was only an indicative study, and therefore, appropriate studies are required to determine the extent, risk factors and nature of the problem.Keywords: Fecal coliforms, tube well, E.coli, Klebsiella sp., Salmonella sp

Collaboration network of applied linguistics research articles with different methodological orientations

The current study draws on synthetic techniques and bibliometric analysis to explore the patterns of scientific collaboration in light of methodological orientations. We examined 3,992 applied linguistics (AL) articles published in 18 top-tier journals from 2009 to 2018 and analyzed their methodological orientations and scientific collaboration. Considering that the number of co-authored papers outweighs single-authored counterparts, our results revealed that the overall degree of collaboration for AL journals was moderate-to-high (57.7%). In particular, quantitative studies contained the highest degree of collaboration (66.8%). This was followed by systematic reviews (60.9%), and mixed-methods approach (55.7%). Country-wise, our overall findings further indicated that the United States and the United Kingdom were the two main hubs of collaborative activities for quantitative, qualitative, and mixed-methods research. While the USA was the top country in systematic reviews like all other research approaches, the UK was the fifth country in systematic reviews. As for collaborating authors, our findings demonstrated that the most influential quantitative researchers had collaborated on Natural Language Processing (NLP) and data mining. While the mixed-methods researchers had a tendency to collaborate on conceptual issues subscribing to the language testing and assessment strand, the most productive qualitative researchers had collaborated on L2 writing issues. Implications for applied linguistics research are further discussed

catena-Poly[[diphenyl­propyl­tin(IV)]-μ-chloroacetato-κ2 O:O′]

The title compound, [Sn(C3H7)(C6H5)2(C2H2ClO2)]n, comprises polymeric carboxyl­ate-bridged spiral chains with two monomer formula units in the asymmetric unit. Both Sn centres exhibit similar distorted trigonal–bipyramidal [C3SnO2] coordination, with the O atoms of the carboyxlate ligands in trans positions

Vitamin B12 supplementation in end stage renal diseases : A systematic review

Acknowledgements The authors wish to thank Hossein Ansari, Javad Tarrahi, Dr. Sakineh Shabbidar and Dr. Hadi Tabibi for their technical and valuable comments.Peer reviewedPublisher PD

Di-μ-ethano­lato-bis­[diethano­lato(2-methyl­quinolin-8-olato)titanium(IV)]

In the centrosymmetric dinuclear title compound, [Ti2(C10H8NO)2(C2H5O)6], the Ti atom is bonded to an N,O-bidentate quinolin-8-olate ligand, two terminal ethano­late anions and two bridging ethano­late anions in a distorted TiNO5 octa­hedral geometry. An intra­molecular C—H⋯O hydrogen bond occurs; in the crystal, inter­molecular C—H⋯O inter­actions help to establish the packing