Harnessing recalcitrant lignocellulosic biomass for enhanced biohydrogen production: Recent advances, challenges, and future perspective

Biohydrogen (Bio-H2) is widely recognized as a sustainable and environmentally friendly energy source, devoid of any detrimental impact on the environment. Lignocellulosic biomass (LB) is a readily accessible and plentiful source material that can be effectively employed as a cost-effective and sustainable substrate for Bio-H2 production. Despite the numerous challenges, the ongoing progress in LB pretreatment technology, microbial fermentation, and the integration of molecular biology techniques have the potential to enhance Bio-H2 productivity and yield. Consequently, this technology exhibits efficiency and the capacity to meet the future energy demands associated with the valorization of recalcitrant biomass. To date, several pretreatment approaches have been investigated in order to improve the digestibility of feedstock. Nevertheless, there has been a lack of comprehensive systematic studies examining the effectiveness of pretreatment methods in enhancing Bio-H2 production through dark fermentation. Additionally, there is a dearth of economic feasibility evaluations pertaining to this area of research. Thus, this review has conducted comparative studies on the technological and economic viability of current pretreatment methods. It has also examined the potential of these pretreatments in terms of carbon neutrality and circular economy principles. This review paves the way for a new opportunity to enhance Bio-H2 production with technological approaches.

Utilization of used textiles for solid recovered fuel production

One of the current important issues is the management of used textiles. One method is recycling, but the processes are characterized by a high environmental burden and the products obtained are of lower quality. Used textiles can be successfully used to produce SRF (solid recovered fuels). This type of fuel is standardized by ISO 21640:2021. In the paper, an analysis of used textiles made from fibers of different origins was performed. These were acrylic, cotton, linen, polyester, wool, and viscose. A proximate and ultimate analysis of the investigated samples was performed, including mercury and chlorine content. The alternative fuel produced from used textiles will be characterized by acceptable parameters for consumers: a lower heating value at 20 MJ/kg (class 1-3 SRF), mercury content below 0.9 µg Hg/MJ (class 1 SRF), and a chlorine content below 0.2% (class 1 SRF). However, the very high sulfur content in wool (3.0-3.6%) and the high nitrogen content in acrylic may limit its use for power generation. The use of alternative fuel derived from used textiles may allow 3% of the coal consumed to be substituted in 2030. The reduction in carbon dioxide emissions from the substitution of coal with an alternative fuel derived from used textiles will depend on their composition. For natural and man-made cellulosic fibers, the emission factor can be assumed as for plant biomass, making their use for SRF production preferable. For synthetic fibers, the emission factor was estimated at the level of 102 and 82 gCO2/MJ for polyester and acrylic, respectively.

Integrating properties and conditions to predict spray performance of alternative aviation fuel by ANN model

Alternative aviation fuel has been confirmed benefits for GHGs reduction and energy saving. Alternative fuel use should meet drop-in fuel requirement, and one of the important factors to ensure combustion completeness is to achieve spray requirement in the whole envelop of flight. Alternative fuels are characterized different fuel properties at low temperature comparison with traditional jet fuel. For understanding fuel properties and spray-related processes under different conditions, alternative aviation fuel, including Fischer Tropsch (FT), cellulose hydrotreating jet fuel (CHJ) and traditional jet fuel (RP-3), were investigated spray performance. According to empirical equation deduced from experiment data (283 K-343 K), deviations to RP-3 enhanced significantly on surface tension and viscosity at low temperature aera (243 K-273 K). As the complex and discontinuous interaction between nozzle structure and fuel properties with temperature, and thus it is difficult to obtain appropriate empirical equation or simulation results at low temperature. Moreover, non-drop-in fuel like pure FT fuel cannot comply with the same spray mechanism as drop-in fuel. The artificial neural network (ANN) approaches have been involved to solve the complex relationship of properties with spray performance. ANN-spray model coupling with ANN-mass flow can predict not only cone angle and liquid length but also SMD and velocity in liquid zone and droplet zone with above 0.99 total correlation coefficient. Coupling simulation results of mass flow and spray performance, FT and CHJ as well as blend fuels present more obvious difference to RP-3 in droplet size distribution and velocity distribution at low temperature.

Advancing renewable fuel integration: A comprehensive response surface methodology approach for internal combustion engine performance and emissions optimization

In the realm of internal combustion engines, there is a growing utilization of alternative renewable fuels as substitutes for traditional diesel and gasoline. This surge in demand is driven by the imperative to diminish fuel consumption and adhere to stringent regulations concerning engine emissions. Sole reliance on experimental analysis is inadequate to effectively address combustion, performance, and emission issues in engines. Consequently, the integration of engine modelling, grounded in machine learning methodologies and statistical data through the response surface method (RSM), has become increasingly significant for enhanced analytical outcomes. This study aims to explore the contemporary applications of RSM in assessing the feasibility of a wide range of renewable alternative fuels for internal combustion engines. Initially, the study outlines the fundamental principles and procedural steps of RSM, offering readers an introduction to this multifaceted statistical technique. Subsequently, the study delves into a comprehensive examination of the recent applications of alternative renewable fuels, focusing on their impact on combustion, performance, and emissions in the domain of internal combustion engines. Furthermore, the study sheds light on the advantages and limitations of employing RSM, and discusses the potential of combining RSM with other modelling techniques to optimise results. The overarching objective is to provide a thorough insight into the role and efficacy of RSM in the evaluation of renewable alternative fuels, thereby contributing to the ongoing discourse in the field of internal combustion engines.

The potential GHGs reduction of co-processing aviation biofuel in life cycle

The challenge of drop-in jet biofuel should couple the reduction of GHGs emission in whole life cycle with economic competitiveness and achieving performance without reducing performance of engine and aircraft. Co-processing was recognized a promising solution due to availability of existing refining infrastructure and facilities. Based on the LCA approach, the quantitative LCA assessment model (AF-3E) has been established for discovering potential GHGs reduction by co-processing. Typical representatives of oily feedstock, including used cooking oil, soybean, rapeseed, peanut, corn oil, Xanthoceras sorbifolia, jatropha and algae, were compared co-processing with HEFA-SPK blend on GHGs and energy consumption in the whole life. Computational framework is integrated into 3 sub-models and 4 modules, which include feedstocks model, fuel model, flight model and electricity module, hydrogen module, methanol module, hexane module. In flight model, the emissions were investigated at LTO condition and cruise condition and transfer to six types of typical aircraft widely used by similarity criterion. Co-processing achieve less energy consumption and GHGs emission than HEFA-SPK blend, which is attributed to less energy consumption in fuel stage. Used cooking oil conducts 8.17% GHGs reduction in 5% bio-feedstock co-processing and 6.39% in 5% HEFA-SPK jet biofuel blend compared with petroleum-based jet fuel. By sensitivity analysis, the vital factors on GHGs have been extracted in whole life cycle. The purpose of this paper is to discover the advantages and vital factors of co-processing. The results would enhance the interests in both LCA and co-processing for sustainable aviation biofuel.

Thermodynamic evaluation of solar assisted ZnO/Zn thermochemical CO2 splitting cycle

The solar thermochemical CO₂ splitting (CDS) is scrutinized via a redox ZnO/Zn cycle. The second law efficiency analysis is carried out by acquiring the required thermodynamic data from HSC Chemistry software. The main focus of this study is to explore the influence of reduction temperature (T_red), molar flow rate of inert sweep gas (n˙_inert), and energy required for the gas separation on the solar-to-fuel energy conversion efficiency (η_{solar-to-fuel}) of the ZnO/Zn cycle. All the calculations are conducted at a constant gas-to-gas heat recovery effectiveness (ε_gg) equal to 0.5. n˙_inert required is recorded to be too high (5050 mol/s) at T_red equal to 1500 K and moderately low (15 mol/s) for T_red equal to 2000 K. The amount of thermal energy required to heat the inert/O₂ gas mixture (from CDS temperature to separator-1 temperature) and inert sweep gas (from separator-1 temperature to reduction temperature) has a significant impact on the total thermal energy requirement of the cycle (Q˙_TC). The rise in T_red from 1500 K to 2000 K shows a considerable decline in Q˙_TC from 77417.5 kW to 1161.8 kW, respectively. Consequently, the highest η_{solar-to-fuel} (17.0%) is recorded for T_red equal to 2000 K.

Estimating the urban environmental impact of gasoline-ethanol blended fuels in a passenger vehicle engine

A large portion of urban emissions in developing countries come from old gasoline vehicles driven in metropolitan areas. The present study aimed to develop models to estimate the environmental impact of different contents of gasoline and ethanol mixtures (pure gasoline; 25, 50, 75% ethanol blended to gasoline; and 100% ethanol) in a flex-fuel engine. We tested the blended fuel using three different speeds and recorded the GHG emissions and engine output data. The data mining approach was used to develop environmental impact predictive models. The ethanol content in gasoline; the engine rotational speed 900, 2000, and 3000 rpm; and λ were used as attributes. The classification target was the environmental impact concerning the CO₂ emission ("low," "average," and "high"). We employed the Random forest algorithm to develop predictive models. The mean values of CO₂ concentrations for all studied fuel content were above 2.47% of the volume. The trees' models (accuracy 73%, κ =0.61) showed three alternatives for predicting the environmental impact based on the ethanol blend, the engine rotation, λ, and the air-fuel ratio. Such models might help policymakers develop educational campaigns to reduce short- and medium-term urban commuter traffic pollution in countries that lack suitable urban transportation.

Environmental protection and energy efficiency improvement by using natural gas fuel in maritime transportation

Emissions from vessels are a major environmental concern because of their impacts on the deterioration of the environment, especially global warming of the atmosphere. Therefore, the International Maritime Organization (IMO) concerns significant care to environmental protection through the reduction of exhaust emission and improvement of energy efficiency through technical and operational measures. Among the suggested measures from IMO, the alternative fuel such as natural gas has the priority to be used instead of fossil fuels. The present paper calculates the effect of using natural gas in a dual-fuel engine from environmental and energy efficiency perspectives. As a case study, a container ship has been investigated. The results of the analysis show that the percent of CO₂, NOx, and SOx emission reduction corresponding to using a dual-fuel engine operated by natural gas instead of a diesel engine operated by heavy fuel oil is about 30.4%, 85.3%, and 97%, respectively. Moreover, it found that NOx and SOx emission rates of the dual-fuel engine comply with the IMO 2016 and 2020 limits, respectively. Furthermore, the Energy Efficiency Design Index value in the case of using dual-fuel engine is lower than the value by using diesel engine by about 30%, and this value will be 77.18%, 86.84%, and 99.27% of the required value for the first, second, and third phases, respectively, as recommended by IMO.

Insight into the recent advances of microwave pretreatment technologies for the conversion of lignocellulosic biomass into sustainable biofuel

The utilization of renewable lignocellulosic biomasses for bioenergy synthesis is believed to facilitate competitive commercialization and realize affordable clean energy sources in the future. Among the pathways for biomass pretreatment methods that enhance the efficiency of the whole biofuel production process, the combined microwave irradiation and physicochemical approach is found to provide many economic and environmental benefits. Several studies on microwave-based pretreatment technologies for biomass conversion have been conducted in recent years. Although some reviews are available, most did not comprehensively analyze microwave-physicochemical pretreatment techniques for biomass conversion. The study of these techniques is crucial for sustainable biofuel generation. Therefore, the biomass pretreatment process that combines the physicochemical method with microwave-assisted irradiation is reviewed in this paper. The effects of this pretreatment process on lignocellulosic structure and the ratio of achieved components were also discussed in detail. Pretreatment processes for biomass conversion were substantially affected by temperature, irradiation time, initial feedstock components, catalyst loading, and microwave power. Consequently, neoteric technologies utilizing high efficiency-based green and sustainable solutions should receive further focus. In addition, methodologies for quantifying and evaluating effects and relevant trade-offs should be develop to facilitate the take-off of the biofuel industry with clean and sustainable goals.

Synergizing environmental, social, and economic sustainability factors for refuse derived fuel use in cement industry: A case study in Espirito Santo, Brazil

The cement industry has been under pressure due to the environmental impact of high cement production, which demands a significant amount of energy and results in greenhouse gas (GHG) emissions. In many developed countries, the cement industry has sought to replace conventional fossil fuels with alternatives to minimize GHG emissions; however, Brazil has underexploited this possibility. Considering the potential of refuse-derived fuel (RDF) to reduce the non-recycled waste disposed in landfills, and its suitable performance as an alternative fuel for cleaner cement production, this paper presents a reverse logistics network analysis for RDF production planning with respect to local economic incentives, social euqity and justice, pollution prevention, and global environmental concerns regarding carbon emissions reduction. The reverse logistics network involves important stakeholders related in waste management in Espirito Santo, Brazil, especially harmonizing social sustainability concerns between waste pickers' cooperatives and waste retailers. By considering the waste generated in 78 municipalities in the Espírito Santo state, the possible levels of fuel replacement in cement industries reflects the economic sustainability of the timeframe of the solid waste management policy implementation. The results showed that the RDF to be produced varies from 42,446.5 tonnes in 2024 with a small fuel replacement by cement industries, to 567,092.1 tonnes in 2040 if all non-recyclable waste available can be used to produce RDF. The avoided annual disposal costs via this network analysis vary from $3,855,412.0 in the initial years to $47,822,876.8 in the year 2040 under optimistic conditions, representing around 25% of the total cost in the network. The cost and GHG emitted reduced significantly in all simulated scenarios; however, the financial incentives are essential for achieving the network social sustainability.

Alternative fuel technologies emissions for road heavy-duty trucks: a review

Many alternative fuel technologies have been studied for the transport sector to increase its sustainability while reducing costs, greenhouse gases (GHG), and air pollution emissions. Nevertheless, conventional diesel is still the predominant fuel for heavy-duty trucks. Road freight transport consumes 25% of the world's energy and is responsible for emissions with local health impacts and the global greenhouse effect. In this context, this paper reviewed items from 2015 to 2020 to analyze the technologies available for the road freight transport regarding pollutant and GHG emissions. Results are presented in two parts: first quantitatively, quantitative data was extracted from reviewed papers and statistically treated and, second, qualitatively through a comparative chart, which shows the impact on air pollutants from the use of a different type of fuels. In general, papers are mostly concerned with particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) emissions due to its impact on public health, with a low number of papers covering GHG emissions. The trade-off between different fuels and how this process can impact emissions, sometimes increasing or decreasing specific pollutants, is discussed. According to the analyzed papers, the main characteristics that affect the pollutant emissions are, in general, the fuel oxygen content and the combustion chamber temperature.

Effect of nanocatalysts on the transesterification reaction of first, second and third generation biodiesel sources- A mini-review

Biodiesel is a fuel that has numerous benefits over traditional petrodiesel. The transesterification process is the most popular method for biodiesel production from various sources, categorized as first, second and third generation biodiesel depending on the source. The transesterification process is subject to a variety of factors that can be taken into account to improve biodiesel yield. One of the factors is catalyst type and concentration, which plays a significant role in the transesterification of biodiesel sources. At present, chemical and biological catalysts are being investigated and each catalyst has its advantages and disadvantages. Recently, nanocatalysts have drawn researchers' attention to the efficient production of biodiesel. This article discusses recent work on the role of several nanocatalysts in the transesterification reaction of various sources in the development of biodiesel. A large number of literature from highly rated journals in scientific indexes is reviewed, including the most recent publications. Most of the authors reported that nanocatalysts show an important influence regarding activity and selectivity. This study highlights that in contrast to conventional catalysts, the highly variable surface area of nanostructure materials favours interaction between catalysts and substrates that efficiently boost the performance of products. Finally, this analysis provides useful information to researchers in developing and processing cost-effective biodiesel.

Morphology and composition of particles emitted from conventional and alternative fuel vehicles

Size, morphology, and composition of airborne particles strongly affect human health and visibility, precipitation, and the kinetic characteristics of particles. In this study, the morphology and chemical composition of particles emitted from conventional (diesel and gasoline) and alternative (CNG and methanol) fuel vehicles were characterized through scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The SEM images revealed that the size of primary particles (without agglomeration) was approximately 10 nm in the exhaust from all the tested vehicles. The particles emitted from gasoline vehicle (GV), CNG vehicle (CNGV), and methanol vehicle (MV) had the same median diameter, 62 nm, which was smaller than those from heavy diesel vehicle (HDV) and light diesel vehicle (LDV). Soot was observed in the HDV, LDV, and GV samples but not in the CNGV and MV. The fractal dimension, which was used to quantify the degree of irregularity of soot, was 1.752 ± 0.014, 1.789 ± 0.076, and 1.769 ± 0.006 in the exhaust from HDV, LDV, and GV samples, respectively. The particles discharged by all tested vehicles contained the elements C, O, Fe, and Na. The main element in the samples of HDV, LDV, and GV was C, while O was the main element in the samples of alternative fuel vehicles. The profiles of minor elements were more complex in the emissions of alternative fuel vehicles than those in the emissions of conventional fuel vehicles. The results improved our understanding of the morphology and elemental composition of particles emitted from vehicles powered by diesel, gasoline, CNG, and methanol.

Protocol for Biodiesel Production by Base-Catalyzed Transesterification Method

The importance of biodiesel and its production cannot be overemphasized; biodiesel has assumed a very prominent position in the energy development of both the developed and developing nations. This is due probably to climate change and the fear of the depletion of the fossil fuel. Biodiesel being not only clean fuel but also obtained from renewable sources is believed to be a better alternative to the traditional petrodiesel. Thus, development geared toward the production and utilization of biodiesel will go a long way in conserving the ecosystem as well as serve as a source of income. This chapter therefore itemizes the protocol for production of biodiesel from plant material using base-catalyst transesterification reaction method.

Potential utilization of commercial waste in Jakarta as alternative fuel by cement industry

As the capital city of Indonesia, Jakarta had a population of 10.2 million in 2015 that generated 6200 metric tonnes (Mt) day^-1 of municipal waste in the 2017-2019 period. In the composition of the waste, as much as 9% is contributed by the commercial sector. This research focuses on five shopping areas in Jakarta (commercial areas (CAs)). The five CAs produce 110 Mt of waste per day and 79% of them are disposed of in landfills. 95% of the waste is a combustible fraction which can be used as an alternative fuel by the cement industry because the fraction has a low heating value of around 24 MJ kg^-1. It is estimated that in one year, the CAs can produce about 34,500 Mt of alternative fuel with 820 TJ of energy. Approximately, the resulting energy savings are 2.6% which is equal to approximately 35,500 Mt of coal. In addition, the utilization of alternative fuel can reduce carbon dioxide emissions by 1.7% or 50,000 Mt.

Sustainability of Palm Biodiesel in Transportation: a Review on Biofuel Standard, Policy and International Collaboration Between Malaysia and Colombia

Biodiesel is gaining prominence as a superior alternative source of energy to replace petroleum-based fuel in transportation. As of today, the biodiesel market continuous to rise up as the biofuel has been introduced to more than 60 countries worldwide. The aim of the present review is to highlight on the scenario of the biofuel implementation in transportation sector towards sustainable development in Colombia and Malaysia. Colombia serves as an ideal comparative case for Malaysia in terms of biodiesel development since the country is the main palm oil producer in Latin America region and the pioneer in bioethanol industry. The first section shows an overview on the biodiesel as an alternative fuel in transportation. The next section will focus on a comparative study between Malaysia and Colombia biodiesel sector in terms of energy supply, resource, production and consumption, standards, techno-economic cost and their biodiesel policies. A comprehensive review was studied to discuss on the sustainability of palm cultivation and biodiesel, impact of palm industry and biodiesel policy in transportation sector and potential international collaboration between Malaysia and Colombia to improve their existing policies, strategies and blueprints related to the palm biodiesel industry, thus overcoming the challenges when dealing with global energy issue.

Prospect of using rice straw for power generation: a review

With the ever-increasing energy demands, fossil fuels are gradually depleting and eventually, these nonrenewable sources of energy will be exhausted. Hence, there is an urgent need to formulate alternative fuels that are both renewable and sustainable. Biomass is one of the reliable sources of energy because it is replenishable. Rice is the staple food in many countries, particularly in Asia. The number of paddy fields has increased tremendously over the years and is expected to increase in the future in response to the growing world population. This will lead to significant amounts of agricultural wastes annually, particularly rice straw. In some countries, open burning and soil incorporation are used to manage agricultural wastes. Open burning is the preferred method because it is inexpensive. However, this method is highly undesirable because of its detrimental impact on the environment resulting from the release of carbon dioxide and methane gas. Hence, it is important to develop an energy-harvesting method from rice straw for power generation. More studies need to be carried out on the availability and characteristics of rice straw as well as logistic analysis to assess the potential of rice straw for power generation. This paper is focused on reviewing studies pertaining to the characteristics and potential of rice straw for power generation, current rice straw management practices, and logistic analysis in order to develop a suitable energy-harvesting method from rice straw in Malaysia.

Food residue biomass product as an alternative fuel for the cement industry

The present study focuses on the production of an alternative fuel (AF) for the cement industry from a food residue biomass (FORBI) product, generated from pre-sorted household food waste (HFW). FORBI is generated by drying and shredding the fermentable fraction of HFW collected door-to-door in the Municipality of Halandri, Greece. The key physicochemical properties such as the net calorific value (NCV), and the concentration of heavy metals and chlorine are subsequently determined using well-established international standards (EN and ISO). FORBI is evaluated as a potential AF in terms of technical feasibility and environmental impacts. Based on the characterization, FORBI is classified as a non-dangerous waste according to EWC 20 01 08, European Commission Decision 2014/955. According to EN 15359, it is classified as category 3, 2, and 1 with respect to NCV, Cl, and Hg respectively. The study concludes that FORBI is a suitable candidate as a secondary fuel for the cement industry, given its high calorific value along with its low humidity and ash content. Challenges for practical implementation include the relatively high chlorine content, the inclusion of alkalis in the cement produced, and the reduction of non-thermal NOx emissions.

Combustion and emissions analysis of Spent Pot lining (SPL) as alternative fuel in cement industry

Spent Pot lining (SPL) is a carbonaceous material generated during the primary aluminum smelting process. SPL is a hazardous waste but the high energy density (carbon rich fraction) and good environmental impacts (toxic materials such as cyanides are destroyed at temperature well above 1000 °C) of the treated SPL (water washed followed with and NaOH and H₂SO₄ treatments) makes it a valuable material for use as fuel feedstocks in cement and steel industries. The principal objective of this study is to investigate the combustion performance and emission characteristics of SPL as alternative fuel in cement industry. The goal is to develop sustainable process systems by using solid waste materials such as SPL from Aluminum industry as a fuel in the cement industry. The proximate (moisture, volatile, fixed carbon, and ash contents) and ultimate (C, H, O, N, S) analyses and the heating value (MJ/kg) of the raw and treated SPL materials are determined first. Computational Fluid Dynamics analysis based on gas and discrete phase modeling (DPM) approach and probability density function/mixture fraction turbulent non-premixed combustion model are used to test the combustion performance and pollutants emissions (flame temperature, fuel particle devolatization and burnout rates, and species concentration formations inside and at the exit of the combustor) of the SPL fuel. The results of the SPL or the alternative fuel combustion are compared with conventional fuel (coal) combustion used in cement industry. The final treated SPL fuel (water washed SPL followed with NaOH and H₂SO₄ treatments) combustion shows lower temperature and NO and CO₂ emissions at the exit from the furnace compared to coal. The results show that the final treated fuel can be used as alternative fuel in cement industry to displace coal fuel and reduce the pollutant emissions from the combustor in cement industry.

Optimization of cultural conditions for lipid accumulation by Aspergillus wentii Ras101 and its transesterification to biodiesel: application of response surface methodology

The present study is aimed to maximize biodiesel production by using the fungal strain Aspergillus wentii Ras101 as a feedstock. Response surface methodology was used to relate the interaction between some nutritional and environmental factors affecting the lipid productivity by A. wentii Ras101. By applying LINGO optimization program, the maximum lipid production of 40% dry biomass of this fungal isolate has been attained in a fermentation medium composed of 50 g/l glucose, 1 g/l nitrates, 1.5 g/l phosphorous, and 0.5 g/l NaCl. This medium was adjusted at pH of 6, and incubated at 28 °C for 7 days. The values of correlation errors between the experimental and estimated values are less than 1%; this proves that the proposed correlation could be used effectively for estimating the fungal lipid production. Consequently, the effects of time and temperature on the amount of biodiesel produced in the extraction and transesterification one-step process have been investigated. The maximum biodiesel production of 28% dry biomass (80% lipid) has been achieved in the transesterification process at 70 °C for 30 min. Additionally, it is found that the combination of glucose, nitrogen and phosphorous contents has a positive influence on lipid production in the fungal biomass. The density, kinematic viscosity, water content and calorific value of the produced biodiesel were 800 kg/m³, 2.8 mm²/s, 66 ppm and 10122 kcal/kg, respectively that matched well with biodiesel and fossil standard specifications.

Experimental investigations on a diesel engine operated with fuel blends derived from a mixture of Pakistani waste tyre oil and waste soybean oil biodiesel

The waste tyre and waste cooking oils have a great potential to be used as alternative fuels for diesel engines. The aim of this study was to convert light fractions of pyrolysis oil derived from Pakistani waste vehicle tyres and waste soybean oil methyl esters into valuable fuel and to reduce waste disposal-associated environmental problems. In this study, the waste tyre pyrolysis liquid (light fraction) was collected from commercial tyre pyrolysis plant and biodiesel was prepared from waste soybean oil. The fuel blends (FMWO10, FMWO20, FMWO30, FMWO40 and FMWO50) were prepared from a 30:70 mixture of waste tyre pyrolysis liquid and waste soybean oil methyl esters with different proportions of mineral diesel. The mixture was named as the fuel mixture of waste oils (FMWO). FT-IR analysis of the fuel mixture was carried out using ALPHA FT-IR spectrometer. Experimental investigations on a diesel engine were carried out with various FMWO blends. It was observed that the engine fuel consumption was marginally increased and brake thermal efficiency was marginally decreased with FMWO fuel blends. FMWO10 has shown lowest NOx emissions among all the fuel blends tested. In addition, HC, CO and smoke emissions were noticeably decreased by 3.1-15.6%, 16.5-33.2%, and 1.8-4.5%, respectively, in comparison to diesel fuel, thereby qualifying the blends to be used as alternative fuel for diesel engines.

A review on the engine performance and exhaust emission characteristics of diesel engines fueled with biodiesel blends

Biodiesels have gained much popularity because they are cleaner alternative fuels and they can be used directly in diesel engines without modifications. In this paper, a brief review of the key studies pertaining to the engine performance and exhaust emission characteristics of diesel engines fueled with biodiesel blends, exhaust aftertreatment systems, and low-temperature combustion technology is presented. In general, most biodiesel blends result in a significant decrease in carbon monoxide and total unburned hydrocarbon emissions. There is also a decrease in carbon monoxide, nitrogen oxide, and total unburned hydrocarbon emissions while the engine performance increases for diesel engines fueled with biodiesels blended with nano-additives. The development of automotive technologies, such as exhaust gas recirculation systems and low-temperature combustion technology, also improves the thermal efficiency of diesel engines and reduces nitrogen oxide and particulate matter emissions.

Production of an environmentally friendly fuel with the aid of ultrasonic waves from a new plant source, and the investigation of its effect on pollutants reduction in a CI engine

In this study, methyl ester of Sisymbrium plant seed oil with the chemical formula of C₁₈H₃₄O₂ is produced for the first time, with the aid of ultrasonic waves and in the presence of a nanocatalyst. After measuring its characteristics and comparing with ASTM standard, it is tested and evaluated with different ratios of diesel fuel in a single-cylinder diesel engine. The reactions are accomplished in a flask by an ultrasonic processor unit and in the presence of CaO-MgO nanocatalyst. The engine tests were conducted based on the engine short time experiment. The results showed that with the increment of biodiesel ratio in the fuel blend, pollutants level of CO, HC, and smoke opacity are decreased comparing diesel fuel due to the improvement of the combustion process, and the amount of NOx emission is increased owing to high pressure and temperature of the combustion chamber. Also, produced biodiesel fuel causes an increment in the fuel consumption and exhaust gasses temperature. Overall, with regard to its effects on the engine and also being a native and easy cultivation plant, it can be resulted that Sisymbrium oil biodiesel and its blends with diesel fuel can be applied as an alternative fuel.

The RDF/SRF torrefaction: An effect of temperature on characterization of the product - Carbonized Refuse Derived Fuel

The influence of Refuse Derived Fuel (RDF)/Solid Recovery Fuel (SRF) torrefaction temperature on product characteristic was investigated. RDF/SRF thermal treatment experiment was conducted with 1-h residence time, under given temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as reference material. The following parameters of torrefaction char from sawdust and Carbonized Refuse Derived Fuel (CRDF) from RDF/SRF were measured: moisture, calorific value, ash content, volatile compounds and sulfur content. Sawdust biochar was confirmed as a good quality solid fuel, due to significant fuel property increase. The study also indicated that RDF torrefaction reduced moisture significantly from 22.9% to 1.4% and therefore increased lower heating value (LHV) from 19.6 to 25.3MJ/kg. Results suggest that RDF torrefaction may be a good method for increasing attractiveness of RDF as an energy source, and it could help unify RDF properties on the market.

Plastic waste to liquid oil through catalytic pyrolysis using natural and synthetic zeolite catalysts

This study aims to examine the catalytic pyrolysis of various plastic wastes in the presence of natural and synthetic zeolite catalysts. A small pilot scale reactor was commissioned to carry out the catalytic pyrolysis of polystyrene (PS), polypropylene (PP), polyethylene (PE) and their mixtures in different ratios at 450°C and 75min. PS plastic waste resulted in the highest liquid oil yield of 54% using natural zeolite and 50% using synthetic zeolite catalysts. Mixing of PS with other plastic wastes lowered the liquid oil yield whereas all mixtures of PP and PE resulted in higher liquid oil yield than the individual plastic feedstocks using both catalysts. The GC-MS analysis revealed that the pyrolysis liquid oils from all samples mainly consisted of aromatic hydrocarbons with a few aliphatic hydrocarbon compounds. The types and amounts of different compounds present in liquid oils vary with some common compounds such as styrene, ethylbenzene, benzene, azulene, naphthalene, and toluene. The FT-IR data also confirmed that liquid oil contained mostly aromatic compounds with some alkanes, alkenes and small amounts of phenol group. The produced liquid oils have high heating values (HHV) of 40.2-45MJ/kg, which are similar to conventional diesel. The liquid oil has potential to be used as an alternative source of energy or fuel production.

Chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot after reactive gas probing using diffuse reflectance FTIR spectroscopy (DRIFTS)

A chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot has been developed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) before and after the reaction with different probe gases. Samples were generated under combustion conditions corresponding to an urban operation mode of a diesel engine and were reacted with probe gas-phase molecules in a Knudsen flow reactor. Specifically, NH₂OH, O₃ and NO₂ were used as reactants (probes) and selected according to their reactivities towards specific functional groups on the sample surface. Samples of previously ground soot were diluted with KBr and were introduced in a DRIFTS accessory. A comparison between unreacted and reacted soot samples was made in order to establish chemical changes on the soot surface upon reaction. It was concluded that the interface of diesel and HVO soot before reaction mainly consists polycyclic aromatic hydrocarbons, nitro and carbonyl compounds, as well as ether functionalities. The main difference between both soot samples was observed in the band of the C=O groups that in diesel soot was observed at 1719 cm^-1 but not in HVO soot. After reaction with probe gases, it was found that nitro compounds remain on the soot surface, that the degree of unsaturation decreases for reacted samples, and that new spectral bands such as hydroxyl groups are observed.

Dioxin-like pcb emissions from cement kilns during the use of alternative fuels

The substitution of combustion fuels in cement plants is increasing throughout many countries, and its individual performance is constantly assessed against strict regulatory standards. For cement plants within Australia, normal operations remain to use petroleum coal as the dominate energy source at the precalciner, avoiding the opportunity to reduce carbon-based resources and pollutant emissions (such as carbon dioxide, oxides of nitrogen, persistent organic pollutants) whilst providing the necessary energy needs through resource recovery. This paper presents stack emission monitoring of health-critical dl-PCB (dioxin-like polychlorinated biphenyl) congeners during the substitution of alternative fuels at ten Australian cement plants, and to distinguish statistical similarities between other key pollutants (such as polychlorinated dibenzo-p-dioxins and furans (PCDD-F) and hydrogen halogens) and amongst the fuels used. Sampling of plant emissions was performed during normal operations (as baseline trials) and with the varied substitution rates of waste oil, solvents, chipped wood, refuge waste, carbon dust, shredded tyres and black sand (as experimental trials). The extraction of field and analytical data during these trials allowed for determining the total and individual unit mass of dl-PCB and PCDD-F isomers, standardised to 10% O₂ and to World Health Organization (2005) toxicity equivalence (TEQ) values. The findings showed waste co-incineration during cement operations does reduce health-critical congeners of dioxins and dl-PCBs whilst providing the necessary energy and calcination needs. Experimental trials showed all dl-PCBs and PCB TEQ are below the internationally regulated Stockholm Convention article of 10pg TEQ/Nm³. In several cases, an increased rate of substituted fuel also identified a consistent reduction to baseline dl-PCBs. The distribution of toxic isomers (TCDD-F and PeCDD-F) were shown to be predominate during waste oil, wood chips, and solvent trials. Whereas the use of TDFs consistently showed a lower toxicity contribution. The distribution of dl-PCBs toxic congeners showed PCB-126 (3,3',4,4',5-Pentachlorobiphenyl) to be greatly present during the co-incineration of waste oil, wood chips, solvents and TDF trials. Principle component analysis identified a statistical predominance from the 1,2,3,7,8-PeCDF (Pentachlorodibenzofuran) and 1,2,3,4,7,8-HxCDF (Hexachlorodibenzofuran) congeners, while dl-PCBs TEQs had similar correlation amongst combustion fuels with major contributions being from the PCB-126 and PCB-169 (3,3',4,4',5,5'-Hexachlorobiphenyl) congeners.

Effect of hydrogen on ethanol-biodiesel blend on performance and emission characteristics of a direct injection diesel engine

Environment issue is a principle driving force which has led to a considerable effort to develop and introduce alternative fuels for transportation. India has large potential for production of biofuels like biodiesel from vegetable seeds. Use of biodiesel namely, tamanu methyl ester (TME) in unmodified diesel engines leads to low thermal Efficiency and high smoke emission. To encounter this problem hydrogen was inducted by a port fueled injection system. Hydrogen is considered to be low polluting fuel and is the most promising among alternative fuel. Its clean burning characteristic and better performance attract more interest compared to other fuels. It was more active in reducing smoke emission in biodiesel. A main drawback with hydrogen fuel is the increased NO_x emission. To reduce NO_x emission, TME-ethanol blends were used in various proportions. After a keen study, it was observed that ethanol can be blended with biodiesel up to 30% in unmodified diesel engine. The present work deals with the experimental study of performance and emission characteristic of the DI diesel engine using hydrogen and TME-ethanol blends. Hydrogen and TME-ethanol blend was used to improve the brake thermal efficiency and reduction in CO, NO_x and smoke emissions.

Solid recovered fuels in the cement industry--semi-automated sample preparation unit as a means for facilitated practical application

One of the challenges for the cement industry is the quality assurance of alternative fuel (e.g., solid recovered fuel, SRF) in co-incineration plants--especially for inhomogeneous alternative fuels with large particle sizes (d95⩾100 mm), which will gain even more importance in the substitution of conventional fuels due to low production costs. Existing standards for sampling and sample preparation do not cover the challenges resulting from these kinds of materials. A possible approach to ensure quality monitoring is shown in the present contribution. For this, a specially manufactured, automated comminution and sample divider device was installed at a cement plant in Rohožnik. In order to prove its practical suitability with methods according to current standards, the sampling and sample preparation process were validated for alternative fuel with a grain size >30 mm (i.e., d95=approximately 100 mm), so-called 'Hotdisc SRF'. Therefore, series of samples were taken and analysed. A comparison of the analysis results with the yearly average values obtained through a reference investigation route showed good accordance. Further investigations during the validation process also showed that segregation or enrichment of material throughout the comminution plant does not occur. The results also demonstrate that compliance with legal standards regarding the minimum sample amount is not sufficient for inhomogeneous and coarse particle size alternative fuels. Instead, higher sample amounts after the first particle size reduction step are strongly recommended in order to gain a representative laboratory sample.

Volatile organic compounds (VOCs) in surface coating materials: Their compositions and potential as an alternative fuel

A sampling system was designed to determine the composition ratios of VOCs emitted from 31 surface coating materials (SCMs). Representative architectural, automotive, and marine SCMs in Korea were investigated. Toluene, ethylbenzene, and xylene were the predominant VOCs. The VOC levels (wt%) from automotive SCMs were significantly higher than those from architectural and marine paints. It was found that target SCMs comprised mainly VOCs with 6-10 carbon atoms in molecules, which could be adsorbed by activated carbon. The saturated activated carbon which had already adsorbed toluene, ethylbenzene, and m-xylene was combusted. The saturated activated carbon was more combustible than new activated carbon because it comprised inflammable VOCs. Therefore, it could be an alternative fuel when using in a "fuelization system". To use the activated carbon as a fuel, a control technology of VOCs from a coating process was also designed and introduced.

Energy intensity, life-cycle greenhouse gas emissions, and economic assessment of liquid biofuel pipelines

Petroleum fuels are predominantly transported domestically by pipelines, whereas biofuels are almost exclusively transported by rail, barge, and truck. As biofuel production increases, new pipelines may become economically attractive. Location-specific variables impacting pipeline viability include construction costs, availability and costs of alternative transportation modes, electricity prices and emissions (if priced), throughput, and subsurface temperature. When transporting alcohol or diesel-like fuels, pipelines have a lower direct energy intensity than rail, barge, and trucks if fluid velocity is under 1 m/s for 4-inch diameter pipelines and 2 m/s for 8-inch or larger pipelines. Across multiple hypothetical state-specific scenarios, profit-maximizing design velocities range from 1.2 to 1.9 m/s. In costs and GHG emissions, optimized pipelines outperform trucks in each state and rail and barge in most states, if projected throughput exceeds four billion liters/year. If emissions are priced, optimum design diameters typically increase to reduce pumping energy demands, increasing the cost-effectiveness of pipeline projects.