Progress in biofuel production from gasification

Biofuels from biomass gasification are reviewed here, and demonstrated to be an attractive option. Recent progress in gasification techniques and key generation pathways for biofuels production, process design and integration and socio-environmental impacts of biofuel generation are discussed, with the goal of investigating gasification-to-biofuels’ credentials as a sustainable and eco-friendly technology. The synthesis of important biofuels such as bio-methanol, bio-ethanol and higher alcohols, bio-dimethyl ether, Fischer Tropsch fuels, bio-methane, bio-hydrogen and algae-based fuels is reviewed, together with recent technologies, catalysts and reactors. Significant thermodynamic studies for each biofuel are also examined. Syngas cleaning is demonstrated to be a critical issue for biofuel production, and innovative pathways such as those employed by Choren Industrietechnik, Germany, and BioMCN, the Netherlands, are shown to allow efficient methanol generation. The conversion of syngas to FT transportation fuels such as gasoline and diesel over Co or Fe catalysts is reviewed and demonstrated to be a promising option for the future of biofuels. Bio-methane has emerged as a lucrative alternative for conventional transportation fuel with all the advantages of natural gas including a dense distribution, trade and supply network. Routes to produce H2 are discussed, though critical issues such as storage, expensive production routes with low efficiencies remain. Algae-based fuels are in the research and development stage, but are shown to have immense potential to become commercially important because of their capability to fix large amounts of CO2, to rapidly grow in many environments and versatile end uses. However, suitable process configurations resulting in optimal plant designs are crucial, so detailed process integration is a powerful tool to optimize current and develop new processes. LCA and ethical issues are also discussed in brief. It is clear that the use of food crops, as opposed to food wastes represents an area fraught with challenges, which must be resolved on a case by case basis

COVID-19 pandemic and global carbon dioxide emissions: A first assessment

Anthropogenic carbon dioxide emissions are the main cause of global climate change. The COVID-19 pandemic has been one of the worst of its kind in the last century with regard to global deaths and, in the absence of any effective treatment, it led to governments worldwide mandating lock-down measures, as well as citizens voluntarily reducing non-essential trips and activities. In this study, the influence of decreased activity on CO2 emissions and on the economy was assessed. The US, EU-28, China and India, representing almost 60% of anthropogenic carbon emissions, were considered as reference entities and the trends were extrapolated to estimate the global impact. This study aimed to deduce initial estimates of anthropogenic CO2 emissions based on the available economic and industrial outputs and activity data, as they could not be directly measured. Sector-wise variations in emissions were modeled by assuming proportionality of the outputs/activities and the resulting emissions. A decline in road traffic was seen up to March 2020 and then a steady growth was observed, with the exception of China where road traffic started to recover by the end of January. The vast majority of passenger flights were grounded and, therefore, global air traffic plummeted by 43.7% from January to May 2020. A considerable drop in coal power production and the annual industrial growth rate was also observed. The overall economic decline led to a drop of 4.9% in annual global gross domestic product (GDP) for Q2 2020. The total global CO2 emissions reduction for January through April 2020 compared to the year before was estimated to be 1749 Mt. CO2 (14.3%) with a maximum contribution from the transportation sector (58.3% among total emissions by sector). Like other previous crises, if the economy rebounds as expected the reductions will be temporary. Long-term impacts can be minimized considering the business as well as lifestyle changes for travel, utilizing virtual structures created during this crisis, and switching to sustainable transportation

Opportunities and challenges in sustainable treatment and resource reuse of sewage sludge: A review

Sludge or waste activated sludge (WAS) generated from wastewater treatment plants may be considered a nuisance. It is a key source for secondary environmental contamination on account of the presence of diverse pollutants (polycyclic aromatic hydrocarbons, dioxins, furans, heavy metals, etc.). Innovative and cost-effective sludge treatment pathways are a prerequisite for the safe and environment-friendly disposal of WAS. This article delivers an assessment of the leading disposal (volume reduction) and energy recovery routes such as anaerobic digestion, incineration, pyrolysis, gasification and enhanced digestion using microbial fuel cell along with their comparative evaluation, to measure their suitability for different sludge compositions and resources availability. Furthermore, the authors shed light on the bio-refinery and resource recovery approaches to extract value added products and nutrients from WAS, and control options for metal elements and micro-pollutants in sewage sludge. Recovery of enzymes, bio-plastics, bio-pesticides, proteins and phosphorus are discussed as a means to visualize sludge as a potential opportunity instead of a nuisance

Equilibrium modeling of thermal plasma assisted co-valorization of difficult waste streams for syngas production

The rising quantities of difficult waste streams are a global concern. Prudent utilization of difficult wastes such as sewage sludge (SS) or refuse derived fuel (RDF) can be a small but crucial step to answer the challenges of waste management coupled with the fulfillment of global energy requirements. Lately, thermal plasma is employed globally to process difficult waste streams because of its several inherent advantages including the potential to produce H2-rich syngas. In this investigation, an equilibrium model was developed with the H2O-Ar stabilized DC arc plasma employing RDF and SS with an objective to assess the optimal process parameters, gas yield, distribution of syngas components and reactor efficiency. The influence of reactor temperature (800 to 1600 °C at SS 30 wt%) and sludge content (0 to 100 wt% at 1200 °C) on syngas constituents, gas yield, LHV, residual carbon and ash was evaluated. The maximum gas yield was noticed as 0.83 kg gas per kg fuel at 1200, 1400 and 1600 °C with a LHV of 11 MJ N−1m−3. Maximum H2and CO volume fractions of 62 and 34 respectively were also observed at 1200, 1400 and 1600 °C. The maximum H2was obtained as 67 vol% at 0 wt% SS whereas the minimum (43 vol%) was achieved at 100 wt% SS. Highest amounts of residual carbon (0.20 kg kg−1fuel and 0.35 kg kg−1fuel) were observed at 800 °C and 0 wt% SS, respectively. The highest reactor efficiency of 53% was realized at 100 wt% RDF (the comparison was performed at 1200 °C). The results of the investigation are encouraging to employ thermal plasma as potentially sustainable and environmentally friendly technology to co-valorize difficult waste streams.</p

Equilibrium modeling of thermal plasma assisted co-valorization of difficult waste streams for syngas production

The rising quantities of difficult waste streams are a global concern. Prudent utilization of difficult wastes such as sewage sludge (SS) or refuse derived fuel (RDF) can be a small but crucial step to answer the challenges of waste management coupled with the fulfillment of global energy requirements. Lately, thermal plasma is employed globally to process difficult waste streams because of its several inherent advantages including the potential to produce H2-rich syngas. In this investigation, an equilibrium model was developed with the H2O-Ar stabilized DC arc plasma employing RDF and SS with an objective to assess the optimal process parameters, gas yield, distribution of syngas components and reactor efficiency. The influence of reactor temperature (800 to 1600 °C at SS 30 wt%) and sludge content (0 to 100 wt% at 1200 °C) on syngas constituents, gas yield, LHV, residual carbon and ash was evaluated. The maximum gas yield was noticed as 0.83 kg gas per kg fuel at 1200, 1400 and 1600 °C with a LHV of 11 MJ N−1m−3. Maximum H2and CO volume fractions of 62 and 34 respectively were also observed at 1200, 1400 and 1600 °C. The maximum H2was obtained as 67 vol% at 0 wt% SS whereas the minimum (43 vol%) was achieved at 100 wt% SS. Highest amounts of residual carbon (0.20 kg kg−1fuel and 0.35 kg kg−1fuel) were observed at 800 °C and 0 wt% SS, respectively. The highest reactor efficiency of 53% was realized at 100 wt% RDF (the comparison was performed at 1200 °C). The results of the investigation are encouraging to employ thermal plasma as potentially sustainable and environmentally friendly technology to co-valorize difficult waste streams.</p

Progress in in-situ CO₂-sorption for enhanced hydrogen production

Deployment of fossil fuels to quench the energy demand of the world's rising population results in elevated levels of greenhouse gas (GHG) emissions, especially CO2, which in turn is responsible for undesirable climate change. This necessitates a shift toward cleaner energy resources such as hydrogen. Enhanced hydrogen production via steam reforming of diverse fuels (methane, biomass, organic wastes, etc.) with in-situ CO2-sorption seems to be a promising alternative. Leading-edge, innovative and eco-friendly pathways coupled with high process efficiencies are needed for the development and growth of this technology. This review article evaluates the fundamental concepts such as criteria for CO2 uptake, mechanisms, thermodynamics and kinetics of the water gas shift reaction along with different modeling methods for sorption enhanced processes. Moreover, research works carried out worldwide at lab-scale coupled with process development and demonstration units are discussed as a means to encourage this pathway for H2 generation. Furthermore, light is shed on techno-economics as an approach to improve the viability and sustainability of the proposed technology. This paper analyzes different dimensions of the CO2-sorption enhanced process to promote it as a potentially carbon-neutral and eco-friendly pathway for hydrogen production.</p

Progress in in-situ CO₂-sorption for enhanced hydrogen production

Deployment of fossil fuels to quench the energy demand of the world's rising population results in elevated levels of greenhouse gas (GHG) emissions, especially CO2, which in turn is responsible for undesirable climate change. This necessitates a shift toward cleaner energy resources such as hydrogen. Enhanced hydrogen production via steam reforming of diverse fuels (methane, biomass, organic wastes, etc.) with in-situ CO2-sorption seems to be a promising alternative. Leading-edge, innovative and eco-friendly pathways coupled with high process efficiencies are needed for the development and growth of this technology. This review article evaluates the fundamental concepts such as criteria for CO2 uptake, mechanisms, thermodynamics and kinetics of the water gas shift reaction along with different modeling methods for sorption enhanced processes. Moreover, research works carried out worldwide at lab-scale coupled with process development and demonstration units are discussed as a means to encourage this pathway for H2 generation. Furthermore, light is shed on techno-economics as an approach to improve the viability and sustainability of the proposed technology. This paper analyzes different dimensions of the CO2-sorption enhanced process to promote it as a potentially carbon-neutral and eco-friendly pathway for hydrogen production.</p

Advancements in solar technologies for sustainable development of agricultural sector in India : a comprehensive review on challenges and opportunities (Apr, 10.1007/s11356-022-20133-0, 2022)

Agriculture is the main occupation of the majority of people in India. The majority of the population in India is dependent (directly or indirectly) on agriculture as an occupation. The agriculture sector requires more freshwater and power for better yield in the current scenario. Nevertheless, the ever-increasing rate of energy consumption, limited fossil fuels, and rising pollution have made the expansion of renewable resources essential. Due to the suitable solar potential available in India, the deployment of solar energy has been more as compared to other renewable resources. The current study aims to discuss the various technologies, initiatives and policies of solar energy usage in agriculture. This work delivers an assessment of the advancement of solar energy vis-a-vis agricultural applications through the greenhouse concept and photovoltaic approach in India. Various agricultural applications of solar energy, such as solar water desalination system, solar water pumping system, solar crop dryer system for food safety, etc. are discussed as a means to promote solar-based technology. It also highlights the scenario of solar energy in India with important accomplishments, developmental approaches, and future potential. In-depth studies of various policies and government initiatives including those in research and development are also discussed. The current survey on solar technologies will be an aid to agribusiness frameworks to comprehend the statuses, obstructions, and extent of advancement. Finally, some future recommendations for further developments in this approach are discussed. This work sheds light on varied areas of solar energy-assisted agricultural systems as a potentially sustainable and eco-friendly pathway

Productivity Augmentation of Solar Stills by Coupled Copper Tubes and Parabolic Fins

A solar still is an eco-friendly device that makes use of ample solar energy for the purification of water. The main objective of this research is to increase the yield output of a double-slope solar still (DSSS) by coupling the basin liner with copper tubes and parabolic fins. In this work, the experiments were supervised for nine days with three different cases. For these experiments, copper tubes with thickness of 2 mm, outer diameter of 32 mm, inner diameter of 28 mm, and parabolic fins with 30 mm diameter and 50 mm height were considered. In the first case, non-coated copper tubes (NCCTs) were used, in the second case, coated copper tubes (CCTs) were employed, and in the last case, coated copper tubes with a combination of parabolic fins (CCTPFs) were used. The MSS (case-III) demonstrated a substantial yearly productivity enhancement of 57.79%, establishing its superiority in terms of output because of its higher daily distillate yield of 1215 mL/day in contrast to CSS. When compared, case III—CCTPF—performed better than case II—CCT—by 35.75%. The CSS and MSS both contributed to a decrease in the pH of the saline water, which went from 8.18 to 7.64 and 7.23, respectively. In comparison to the MSS and CSS, which had 0.428 mg/L and 0.569 mg/L of fluoride ions, respectively, brine water had a fluoride ion level of 0.734 mg/L. Total dissolved solids (TDS) concentration before desalination was 440 ppm and it was minimized to 20 ppm with MSS and 55 ppm with CSS, respectively, post-desalination. The corresponding cost per liter (CPL) of MSS and CSS is USD 0.053 and USD 0.040, respectively

Advancements in solar technologies for sustainable development of agricultural sector in India : a comprehensive review on challenges and opportunities

Agriculture is the main occupation of the majority of people in India. The majority of the population in India is dependent (directly or indirectly) on agriculture as an occupation. The agriculture sector requires more freshwater and power for better yield in the current scenario. Nevertheless, the ever-increasing rate of energy consumption, limited fossil fuels, and rising pollution have made the expansion of renewable resources essential. Due to the suitable solar potential available in India, the deployment of solar energy has been more as compared to other renewable resources. The current study aims to discuss the various technologies, initiatives and policies of solar energy usage in agriculture. This work delivers an assessment of the advancement of solar energy vis-a-vis agricultural applications through the greenhouse concept and photovoltaic approach in India. Various agricultural applications of solar energy, such as solar water desalination system, solar water pumping system, solar crop dryer system for food safety, etc. are discussed as a means to promote solar-based technology. It also highlights the scenario of solar energy in India with important accomplishments, developmental approaches, and future potential. In-depth studies of various policies and government initiatives including those in research and development are also discussed. The current survey on solar technologies will be an aid to agribusiness frameworks to comprehend the statuses, obstructions, and extent of advancement. Finally, some future recommendations for further developments in this approach are discussed. This work sheds light on varied areas of solar energy-assisted agricultural systems as a potentially sustainable and eco-friendly pathway