No abstract

No abstract

Inland water bodies (particularly ponds) emit a significant amount of greenhouse gases (GHGs), particularly methane (CH4), carbon dioxide (CO2), and a comparatively low amount of nitrous oxide (N2O) to the atmosphere. In recent decades, ponds (<10,000 m2) probably account for about 1/3rd of the global lake perimeter and are considered a hotspot of GHG emissions. High nutrients and waterlogged conditions provide an ideal environment for CH4 production and emission. The rate of emissions differs according to climatic regions and is influenced by several biotic and abiotic factors, such as temperature, nutrients (C, N, & P), pH, dissolved oxygen, sediments, water depth, etc. Moreover, micro and macro planktons play a significant role in CO2 and CH4 emissions from ponds systems. Generally, in freshwater bodies, the produced N2O diffuses in the water and is converted into N2 gas through different biological processes. There are several other factors and mechanisms which significantly affect the CH4 and CO2 emission rate from ponds and need a comprehensive evaluation. This study aims to develop a decisive understanding of GHG emissions mechanisms, processes, and methods of measurement from ponds. Key factors affecting the emissions rate will also be discussed. This review will be highly useful for the environmentalists, policymakers, and water resources planners and managers to take suitable mitigation measures in advance so that the climatic impact could be reduced in the future.

Wheat straw soda lignin was subjected to thermochemical (TC) pretreatment at low to moderate temperatures followed by electrooxidation (EO) on an SS-304 anode to produce some value-added organic chemicals. The influence of independent process variables on the product yield of major organic chemical groups, namely, aromatic carbonyl compounds (COarom), aromatic hydrocarbons (HCarom), and aliphatic hydrocarbons (HCaliph), was studied. Response surface methodology (RSM) was used to optimize the process conditions for maximizing the amount of chemical production according to the Box-Behnken experimental design (BBD). For COarom, the optimal conditions were 2 h TC pretreatment at 200°C followed by 12 h of EO at 2.24 mA cm−2current density to yield 24.7% of desired products. The optimized synthesis conditions for HCaromare 2 h TC treatment at 200°C yielding 16.1% desired products. As individual compounds, vanillin, acetosyringone, syringaldehyde, acetovanillone,o-xylene and toluene were significantly produced in different product groups. A small amount of organosilicon compounds (ORGSi) and HCaliphwas also produced.

The biggest challenge in front of energy scientists is to find the alternative to diesel engine fuel due to depletion of fossil fuels and the environmental pollution, which is increasing alarmingly. Oxygenated fuel is one of the viable solutions to the global environmental changes. Dimethyl carbonate (DMC) and Dibutyl Maleate (DBM) are two hopeful fuel additives to reduce emission in diesel engine, due to their high oxygen content, 53.3 and 28 % respectively. This paper presents an experimental study of their effects on the emission characteristics of a diesel engine. DMC and DBM was used with diesel in different blends for all load ranges of the engine viz. at no load, 25%, 50% and 75% of full load and at full load. All tests were conducted at steady state and were set at constant engine speed 1500 RPM. The smoke content reduces by 35% at full load conditions using DMC20 blend, the oxygen content in the emission increases by 39% with DBM15, the decrease in the % of unburnt hydrocarbons and carbon monoxide is respectively 19 and 21. The blends of diesel with 15% DMC and DBM by volume is the best fraction for reduction of smoke and CO emissions without much affecting the performance of the engine. On the basis of the results obtained, these additives are effective method for reducing the emission of diesel engine.