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India has about a tenth of the world’s coal reserves, much of it with high mineral content. These coals produce a large amount of fly ash, which can affect human health and environmental quality aspects during utilization. In this paper, the petrological and biological aspects of some industrially important Indian coal fly ash (CFA) from a coal-based captive power plant are addressed. The petrology of the CFAs is also studied for the samples collected in different times. The study has revealed that the CFAs contain mainly glass fragments, spinel, quartz, and other minerals in lesser quantities. Fly ash carbons were present as chars, possibly from the incomplete combustion of the coals (bituminous and/or subbituminous) used in the power plant. The deposition of CFAs over the leaves of different plant species reduces the photosynthesis rate by about 95% within a period of 2 h. The CFAs also show minor effects to some test microbes. This investigation will be useful in assessment of the environmental impact of a coal-based power plant. [ABSTRACT FROM AUTHOR]

• 6.34% of fuel energy and 5.20% of fuel exergy are lost through the exhaust gases. • KCS11 can well be integrated with cogeneration plant for exhaust heat utilization. • On the basis of acid due point calculations, exhaust heat is utilized up to 105 °C. • Exhaust temperature can be further lowered if FGD unit or Teflon coating is used. • The performance can be improved drastically if bagasse moisture is reduced to nil. Power generation through bagasse-fired cogeneration plants is a common practice in sugarcane producing countries. The exergy-based analysis of a 16 MW grid-connected cogeneration plant of a sugar factory situated in India carried out by the author earlier and published as a separate paper, had disclosed that 6.34% of fuel energy and 5.20% of fuel exergy were lost through the flue gases. To utilize a part of this waste heat for conversion into electricity, in this paper, Kalina cycle is theoretically integrated with the considered plant. The sulphuric dew point is estimated to be 100.25 °C. Hence, to prevent acid condensation from exhaust gases, the exhaust heat can be safely utilized up to a temperature of 105 °C. Keeping ammonia-mass fraction at 0.8 and turbine inlet pressure at 4000 kPa, the net power output of the integrated plant is found to increase by 375.2135 kW thereby increasing the overall energy and exergy efficiencies of cogeneration by 0.3819% and 0.3150% respectively. The plant currently uses bagasse containing 50% moisture. If bagasse is completely dried by suitable means, power output will further increase by 3531.5 kW increasing the cogeneration energy and exergy efficiencies further by 3.5948% and 2.9630%. [ABSTRACT FROM AUTHOR]

• India's road transport sector heavily dependent on imported fossil fuels. • Consequently, energy security, economy and environment are adversely impacted. • Biofuels, CNG, CBG, LPG, methanol, electricity, and hydrogen are preferred alternative options. • Policy supports for development of these alternative fuels are discussed. • Opportunities and challenges for growth of these fuels are also analysed. Rapid economic development and increasing population are contributing to growing energy demand in India. Road transport sector, almost fully dependent on petroleum oil, is the third highest user of the total final energy in India. More than four-fifth of crude petroleum is imported, which is responsible for nearly one-fifth of country's import bill. India's share of the global energy related CO 2 emissions was about 7% in 2018, of which about 13% was caused by the transport sector. With a view of decarbonising the road transport sector and also addressing issues concerning energy efficiency, energy security, air quality and transport induced noise, alternative fuels have been explored in India for about two decades. This paper reviews policy support and related developments regarding biofuels, compressed natural gas, methanol, electricity, and hydrogen for automotive applications in India with a brief mention about international progress. The opportunities for their growth by 2030 and challenges to realise the potential are also analysed. Biofuels and electricity can offer significant opportunities for decarbonising the road transport sector in the near term. Compressed natural gas in short term and hydrogen in medium and long term may also play important roles in this regard. [ABSTRACT FROM AUTHOR]

• Indian power coal and fly ash are examined geochemically and petrologically. • Advance electron beam techiniqes are applied for nano-scale studies of the samples. • Concentration of trace and REEs in the samples are determined and studied. • There is possibility for environmental implications from these coal fly ash. The utilization of coal and its by-products (coal-combustion fly ash) is known for its detrimental effects on the environment including human health issues and global climate change. In this paper, the basic chemistry and geochemistry along with the petrographic studies of thermal plant's feed coal and their generated coal fly ashes is reported. The study also aims to predict the associated environmental concerns and quantification of REEs in the fly ash, which possibly might represent sources for recovery. The major minerals observed were quartz, kaolinite, haematite, illite, pyrite, and calcite in coal; and quartz, haematite, and pyrite in fly ash as confirmed by X-ray diffraction analysis. The results also demonstrated that Ce and Pr were exceptionally high in the both the samples C-1 (1075 ppm) and CF-2 (1248 ppm). The abundance of Nd is found to be high (479 ppm) in the fly ash samples. Hazardous elements were associated with nanominerals, including pyrite, anatase, and kaolinite as identified by using electron beam techniques. A multivariate statistical analysis of the elements including REEs in both coal and coal fly ash is also carried out to understand their mutual correlations. [ABSTRACT FROM AUTHOR]

• Lithotype and depth control cleat permeability in Raniganj coals, India. • Analytical permeabilities are two-fold larger than measured permeabilities. • Depth calibrated minimum aperture as input provides closest approximation. • Results will be useful in pre-drill permeability estimation. Coal porosity and permeability are key petrophysical parameters, pivotal in facilitating coalbed methane extraction and CO 2 sequestration. Distribution of coal fractures, their association with coal stratigraphy, and their depth of occurrence primarily control coal porosity and permeability. The primary coal fracture networks, made of cleats, are the fundamental pathways for fluid flow through coal seams as matrix porosity and permeability are negligible. This paper documents the distribution of cleats and interrelationships amongst their attributes (aperture, spacing) as a function of depth and their role in controlling the porosity-permeability distribution of the Gondwana coals (Raniganj Formation) from India. The analytically computed effective permeability (based on effective aperture) estimations using the measured cleat parameters are more than two orders of magnitude higher than previously reported permeability values derived from geophysical log analysis, laboratory measurements and field tests. Such gaps between analytical results and measured data are also reported from multiple coal-bearing basins around the world. We, therefore, carry out an uncertainty analysis of measured aperture and used reported limits of cleat compressibility to estimate the range of possible permeabilities. We infer that the analytical solution combining the lower bounds of aperture distribution and cleat compressibility can be used as the closest approximation of effective permeability at pre-drill exploration stage of a coalbed methane project. [ABSTRACT FROM AUTHOR]

• Need of biofuel in lieu of fossil fuel has been justified. • Evolution of biofuel policies in Brazil and Russia were described. • Bioethanol and biodiesel policy of India, China and South Africa were addressed. • Blending mandate and Legal challenges of biofuel in BRICS were presented. Biofuels share a meagre fraction in the total fuel consumption, and their usage is speculated to upsurge steadily in the years to come. One of the key drivers for the development of biofuel production industries and simultaneous dilution of biofuels in the energy market is the country's policy. Hence, this critical review focuses on the evolution of biofuel policies in the BRICS (Brazil, Russia, India, China, and South Africa) nations and successful implementation of the policies by the respective countries. In detail, this paper provides legal framework and policies prompted the expansion of biofuel research and industries across the BRICS nations. It extensively presents key laws, blending targets, current regulation, national action plan, government support mechanism (subsidies), output targets, and major hurdles and scope in biofuel policies of BRICS nations for efficient penetration of biofuel to the energy market. [ABSTRACT FROM AUTHOR]

• Cotton stalk is characterized and investigated for pyrolysis and CO 2 gasification reactions. • Single Reaction and Distributed Activation Energy models explains the pyrolysis kinetics. • Gas evolution and tar formation are studied for cotton stalk pyrolysis at 10 K/min heating rate. • Surface area of char during CO 2 gasification reaction goes through a maximum. • Modified Random Pore Model explains the kinetics of CO 2 gasification of char. The paper presents a detailed study on both, pyrolysis and gasification of cotton stalk, investigated using Thermo-gravimetric Analyser (TGA) and a fixed bed reactor. The pyrolysis experiments are conducted at different heating rates over a range 5–30 K/min in an inert medium. Pyrolysis reactions are observed to be dependent on the operating condition and chemical composition confirmed by FTIR analysis. Gas evolution kinetics during pyrolysis process and tar formation are also studied in a specially designed fixed bed reactor. CO 2 -char gasification experiments are conducted at different temperatures over a range of 973–1123 K. The char gasification reaction is observed to be dependent on char surface area and inorganic content of biomass. The kinetic parameters for pyrolysis are estimated using model-free/model-fitting methods such as Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Coats-Redfern (CR), Single Reaction Model (SRM), and Distributed Activation Energy Model (DAEM). The kinetic parameters for CO 2 gasification are estimated using Random Pore Model (RPM) and Modified RPM. [ABSTRACT FROM AUTHOR]