Substitution Of Fossil Fuels Research Articles

Use of ensiled green willow biomass in biogas fermentation.

The biggest challenges of our era include climate change and the global fossil energy problem. Extensive utilization of renewable energy sources should be a part of the solution for both these problems. Biogas is a versatile renewable energy carrier that has the potential to substitute fossil fuels. The most frequently utilized substrates for the anaerobic digestion (AD) process include maize silage today, but there is an increasing demand for second-generation biomass sources, which are cheaper and do not interfere with the cultivation of food production. Green biomass from short rotation coppice willow (GWB) may be a promising alternative. However, to ensure feedstock quantity and quality all year round, a preservation method has to be developed. We attempted to ensilage the biomass and subsequently utilized the resulting willow-silage in batch fermenters. Various mixtures of lactic acid bacteria were employed to facilitate ensiling by inoculation of the substrate in anaerobic jars for 60days. During the ensiling analytical investigations, (HPLC, pH, oTS/TS%) were carried out in order to follow the build-up of fermentation products. AD fermentations were assembled from the ensilaged biomass and the methane production was measured for 56days. The total methane yields of the ensilaged biomass were 8-15% higher than that of the fresh biomass and methane production rates were also improved. Our findings suggest that ensiling is not only an excellent preservation method for willow biomass, but also stimulates its AD.

Toward sustainable electricity generation mix: an econometric analysis of the substitutability of nuclear energy and hydropower for fossil fuels in Canada

ABSTRACT The dominance of fossil fuels in electricity generation fuel mix continues to undermine the importance of electricity as a critical factor for sustainable economic development. As with most economies of the world, the Canadian fuel mix for electricity generation is dominated by fossil fuels. This scenario creates both environmental and resource sustainability challenges. There are questions marks over the potentials of nonfossil energy sources to address these challenges and ensure a more sustainable electricity generation. This study aims to examine the potentials of nuclear energy and hydropower to substitute the fossil fuels of coal and natural gas in electricity generation for Canada. A trans-log production function was estimated with the ridge regression method to obtain the parameter estimates. The empirical findings show that, with the exception of coal input, all energy inputs have positive output elasticities, which indicate that an increase in the energy inputs will increase output in Canada. The results further provide evidence of positive elasticity of substitution between the non-fossil energy sources and the fossil fuels which give credence to the hypothesis that clean energy sources such as nuclear energy and hydropower have the potential to substitute for the fossil fuels of coal and natural gas the electricity generation process for Canada. The estimates show that the smallest substitution occurs between coal and gas, which is an additional evidence that clean energy has higher chances of substituting fossil fuels. Policies that promote the adoption of more renewable and clean energy sources are recommended in the body of the paper.

The substitution of fossil fuels in the US transportation energy mix: Are emissions decoupling from economic growth?

Environmental protection should be a primary factor in the evolution of the dominant transportation energy paradigm. This paper takes a fresh approach to this issue by analysing the relationship between conventional and alternative energy sources in transportation, economic growth and emissions. This is a previously unexplored topic in literature, particularly in the United States of America (US), which is analysed in detail here. The paper makes a further contribution to the field by an analysis, based on Tapio indicator, of decoupling between economic growth and CO2 emissions resulting from both overall energy consumption and energy consumption by the transportation. Empirically, this paper applies an Autoregressive Distributed Lag model by using monthly data from January 2007 to September 2018. A Decoupling Indicator was calculated by using yearly data from 2006 to 2018. Main findings suggest that alternative energy sources have not yet reducing the dependence of the transportation sector on fossil fuels. Additionally, although the use of renewable fuels by transportation reduces CO2 emissions, it also hampers economic growth, while economic growth has a negative effect on emissions. This finding is further supported by the decoupling statuses found. I Improvements in energy efficiency appear to have been effective for environmental protection.

The sector coupling concept: A critical review

AbstractPursued climate goals require reduced greenhouse gas emissions by substituting fossil fuels with energy from renewable sources in all energy‐consuming processes. On a large‐scale, this can mainly be achieved through electricity from wind and sun, which are subject to intermittency. To efficiently integrate this variable energy, a coupling of the power sector to the residential, transport, industry, and commercial/trade sector is often promoted, called sector coupling (SC). Nevertheless, our literature review indicates that SC is frequently misinterpreted and its scope varies among available research, from exclusively considering the use of excess renewable electricity to a rather holistic view of integrated energy systems, including excess heat or even biomass sources. The core objective of this article is to provide a thorough understanding of the SC concept through an analysis of its origin and its main purpose, as described in the current literature. We provide a structured categorization of SC, derived from our findings, and critically discuss its remaining challenges as well as its value for renewable energy systems. We find that SC is rooted in the increasing use of variable renewable energy sources, and its main assets are the flexibility it provides for renewable energy systems, decarbonization potential for fossil‐fuel‐based end‐consumption sectors, and consequently, reduced dependency on oil and gas extracting countries. However, the enabling technologies face great challenges in their economic feasibility because of the uncertain future development of competing solutions.This article is categorized under: Energy Systems Economics > Economics and Policy Energy Systems Economics > Systems and Infrastructure

Effects of Pyrolysis Bio-Oils on Fuel Atomisation—A Review

Bio-oils produced by biomass pyrolysis are substantially different from those produced by petroleum-based fuels and biodiesel. However, they could serve as valuable alternatives to fossil fuels to achieve carbon neutral future. The literature review indicates that the current use of bio-oils in gas turbines and compression-ignition (diesel) engines is limited due to problems associated with atomisation and combustion. The review also identifies the progress made in pyrolysis bio-oil spray combustion via standardisation of fuel properties, optimising atomisation and combustion, and understanding long-term reliability of engines. The key strategies that need to be adapted to efficiently atomise and combust bio-oils include, efficient atomisation techniques such as twin fluid atomisation, pressure atomisation and more advanced and novel effervescent atomisation, fuel and air preheating, flame stabilization using swrilers, and filtering the solid content from the pyrolysis oils. Once these strategies are implemented, bio-oils can enhance combustion efficiency and reduce greenhouse gas (GHG) emission. Overall, this study clearly indicates that pyrolysis bio-oils have the ability to substitute fossil fuels, but fuel injection problems need to be tackled in order to insure proper atomisation and combustion of the fuel.

Forecasting Wind Speed in Peninsular Malaysia: An Application of ARIMA and ARIMA-GARCH Models

In the global energy context, renewable energy sources such as wind is considered as a credible candidate for meeting new energy demands and partly substituting fossil fuels. Modelling and forecasting wind speed are noteworthy to predict the potential location for wind power generation. An accurate forecasting of wind speed will improve the value of renewable energy by enhancing the reliability of this natural resource. In this paper, the wind speed data from year 1990 to 2014 in 18 meteorological stations throughout Peninsular Malaysia were modelled using the Autoregressive Integrated Moving Average (ARIMA) to forecast future wind speed series. The Ljung-Box test was used to determine the presence of serial autocorrelation, while the Engle’s Lagrange Multiplier (LM) test was used to investigate the presence of Autoregressive Conditional Heteroscedasticity (ARCH) effect in the residual of the ARIMA model. In this study, three stations showed good fit using the ARIMA modelling since no serial correlation and ARCH effect were present in the residuals of the ARIMA model, while the ARIMA-GARCH had proven to precisely capture the nonlinear characteristic of the wind speed daily series for the remaining stations. The forecasting accuracy measure used was based on the value of root mean square error (RMSE) and mean absolute percentage error (MAPE). Both ARIMA and ARIMA-GARCH model proposed provided good forecast accuracy measure of wind speed series in Peninsular Malaysia. These results will help in providing a quantitative measure of wind energy available in the potential location for renewable energy conversion.

Environmental and energy performance of residual forest biomass for electricity generation: Gasification vs. combustion

Abstract Bioenergy systems have a great potential worldwide to substitute fossil fuels mainly because they may contribute to greenhouse gas emissions reduction. In Portugal, several biomass combustion-based power plants have been built in the last decade. Biomass gasification is a potential alternative to combustion but its environmental impacts should be evaluated. The goal of this study is to assess and compare the environmental and energy performance of direct gasification and combustion (both in fluidized bed) using residual forest biomass (RFB) from eucalypt in Portugal. In order to achieve the goal, life cycle assessment was applied, complemented with the Energy-Returned-On-Energy-Invested (EROI) indicator. The boundaries of the systems comprise three stages: (1) forest management, (2) collection, processing and transportation, and (3) electricity generation. The results indicate that gasification performs environmentally better than combustion in 5 out of 8 impact categories addressed. Conversely, combustion has greater EROI than gasification. After running a sensitivity analysis where the efficiency of the gasifier was changed from 53% in the base scenario to 57%, it is shown that the environmental performance of gasification improved in the range of 2–8%. The study concludes that gasification may be a good alternative to current combustion systems in Portugal.

Socio-economic and environmental effects of renewable energy policy in Russia

The development of renewable energy is associated with a number of economic and non-economic effects, such as, inter alia, reduction of greenhouse gas emissions, substitution of fossil fuels, impro...

Sekvestracijski potencijal energetske kulture Miscanthus x giganteus uzgajane u kontinentalnoj Hrvatskoj

Miscanthus x giganteus is an energy crop relatively recently introduced into Croatia, that is suitable for cultivation on marginal or abandoned agriculturl land. Energy crops can contribute to climate change mitigation both by carbon sequestration into soil/plant pool and by substitution of fossil fuels. Therefore, the aim of this paper is to evaluate the impact of Miscanthus x giganteus cultivation on the environment by determination of soil and soil-plant system's carbon budget, as well as to estimate the sequestration potential of Miscanthus stand on abandoned agricultural land at national level. After the 3 years of Miscanthus cultivation, soil pH and K2O decreased, P2O5 increased and Ntot remained the same. Plant biomass increased from April, peaked in September, and decreased towards the spring harvest with harvested yield of 14.5 t/ha. Average soil respiration amounted 9.1 t/ha/y, and didn't show seasonal trend, or significant correlation to soil temperature and moisture. Estimated sequestration potentials of Miscanthus are 1.3 (soil system) and 2.0 (soil-plant system) t/ha/y. The highest contribution to carbon gains and losses had respectively preharvest losses and soil respiration. Between 704 520-3 251 600 t C could be sequestrated in soil/plant pool in Miscanthus lifespan if 5-15% of abandoned agricultural land would be converted to Miscanthus cultivation. Therefore, Miscanthus represents biological carbon sink due to great sequestration potential and additional fossil fuel replacement benefits.

Molecular characterization of blue-green algae (Anabaena constricta) and comparative studies of biodiesel production from other species

Biodiesel can substitute fossil fuels adequately and thus, considered ‘future fuel’. Thus, identifying a promising algal strain for efficient biodiesel production is a very important endeavor. In the present investigation, the blue green algae, Anabaena constricta could be grown aseptically attaining exponential phase, 3 days post inoculation, responds to phototropism and amenable to both autotrophic and heterotrophic mode. Phylogenetic analysis reveal that Anabaena constricta grouped separately from other algal strains used in the study, making it unique in nature. Further, comparative studies of selected algal and blue green algal strains based on the oil percentage and fatty acid profile indicate potential biodiesel properties. The total lipid content of Anabaena constricta is estimated to 14% of the dry weight, and fatty acids profiling indicate presence of 11 fatty acid methyl esters (FAMEs), principally palmitic acid (16:0), oleic acids (18:1), linoleic acid (18:2), palmitoleic acid (16:1). The algal species, Hydrodictyon registered highest percentage of unsaturated fatty acids (59.5%), while highest content of saturated fatty acid was found in Anabaena constricta (51.5%). Cetane Number of seven algal and blue green algal biodiesel varied from 54.77 to 58.2 and Saponification Value varied from 205.6 to 211.39. PROMETHEE & GAIA analyses indicate both the Rhizoclonium and Tolypothrix species outranked while Hydrodictyon and Anabaena constricta are the least suitable species in seven algal and blue-green algal species studied for biodiesel production. Well-characterized strains offer promise for biodiesel production at a cost-effective level. The present study focus on the renewable fuel, which is useful for reducing the carbon footprint with potential to impact self-sustainability in fuel sector, without modification in current infrastructure.

Dark Fermentative Biohydrogen Production from Palm oil Mill Effluent: Operation Factors and Future Progress of Biohydrogen Energy

Malaysia is one of the largest producers and exporters of palm oil, thus, a large amount of palm oil mill effluent (POME) is generated through this process. POME contributes to environmental pollution if it is not properly treated. This complex effluent consists of colloidal matters and mainly organic components with more than 90% water. Thus, it is useful to be used as a substrate for fermentative processes, including biohydrogen production. Biohydrogen from POME is a renewable source that can potentially serve as an alternative to substitute fossil fuels. The abundance of POME and the rising price of fossil fuels in the global market create a demand for this source of energy. However, the complexity of the substituents in POME makes the optimisation of this effluent as a substrate in dark fermentation a challenge. This review article explores the important parameters that need to be considered for optimal biohydrogen production, such as the bioreactor operational parameters and the microbial consortium. Besides, the potential of metabolic engineering as a tool to overcome the limitations of the microbial strains to metabolise POME for increased biohydrogen production was also reviewed. However, further research and development are needed to increase the biohydrogen yield on par with commercial demand.

Sustainable electricity generation: the possibility of substituting fossil fuels for hydropower and solar energy in Italy

ABSTRACT Electricity remains the most important form of end-use energy consumption and an important factor for economic growth and development. However, electricity generation also constitutes a great source of concern for global warming and climate change with threats to sustainable development as fossil fuels dominate electricity generation fuel mix for most economies of the world. This is exactly the case for Italy with fossil fuels dominating electricity generation fuel mix over the last couple of decades. Thus, there is a need to reverse this trend by increasing the shares of renewable energy sources in the fuel mix. This study, therefore, investigates the potentials for renewable energy sources of hydropower and solar energy to substitute the fossil fuels of coal and natural gas in electricity generation for Italy. Adopting the ridge regression procedure to obtain the parameter estimates, the results provide evidence that substitution is possible among all fuels. While both hydropower and solar energy are found to be substitutable for the fossil fuels, solar energy is found to provide more substitutability than hydropower. This implies that Italy has the potential to gradually move away from the carbon-intensive fossil fuels of coal and gas to more environmental-friendly solar energy and hydropower in the process of generating electricity.

Optimization of an ultrasonic reactor on a semi-pilot scale for biodiesel production

Biodiesel has become a very attractive alternative to substitute fossil fuels and therefore, there is an increasing interest in the study and optimization of the transesterification reaction that is used to prepare this fuel. The most popular approach to carry out this reaction employs a homogeneous catalyst in a stirred system and recently, ultrasonic reactors in lab scale studies have shown potential. In this context, an optimization study of the operating conditions of an ultrasonic reactor at a semi-pilot scale is hereby reported. The reaction system includes a 9 L reactor equipped with ultrasonic transducers positioned outside and in contact with the reactor’s walls and connected to a 1500 W ultrasonic generator. The performance was studied using an experimental system working in a continouos process with recirculation. A 33 design of experiment (DOE) and response surface methodology (RSM) were used to evaluate the effect of % weight catalyst, methanol: oil molar ratio and reaction time on biodiesel conversion. The experimental results indicate that while the % catalyst and reaction time have a significant and positive effect on the transesterification conversion yield, the molar ratio is significant only through its interaction with time. According to the empirical equation derived from the statistical analysis, optimal conditions for the operation of the ultrasonic reactor for biodiesel production are 1. 88% of catalyst, 9:1 M ratio and 13 min of reaction to reach a conversion value of 99%.

Advantages of the unscavenged pre-chamber ignition system in turbocharged natural gas engines for automotive applications

In view of the increasing restrictions for CO2 mitigation, the evaluation of alternative fuels to ensure sustainability of transportation is becoming increasingly important. Since some of these alternatives can be refined from renewable sources, they are interesting from the perspective of both: the use of the current power-plants and the CO2 emission. In this sense, natural gas arises as an interesting propellant to substitute fossil fuels. Therefore, combining this fuel with specific combustion strategies can help to decrease the environmental footprint of transportation in the broadest sense. In this paper, an evaluation of the possible advantages of this combination has been conducted. The investigation has been carried out in a port fueled turbocharged spark-ignition engine, using compressed natural gas (CNG) and a passive pre-chamber ignition system. The effects of the CNG fuel properties on combustion have been analyzed and the global impact of using CNG for transportation has been appraised by means of the life cycle assessment. Results show that combustion of CNG refined by different renewable sources not only reduces the global CO2 emission but also can contribute to remove the existent pollution. In addition, they show an increase of the engine thermal efficiency when combining CNG and the pre-chamber ignition concept.

Assessing the Influence of Compression Ratio on Engine Characteristics Including Operational Limits of a Biogas-Fueled Spark-Ignition Engine

Abstract Biogas, which is a renewable alternative fuel, has high antiknocking properties with the potential to substitute fossil fuels in internal combustion engines. In this study, performance characteristics of a spark-ignition (SI) engine operated under methane (baseline case) and biogas are compared at the compression ratio (CR) of 8.5:1. Subsequently, the effect of CR on operational limits, performance, combustion, and emission characteristics of the engine fueled with biogas is evaluated. A variable compression ratio, spark-ignition engine was operated at various CRs of 8.5:1, 10:1, 11:1, 13:1, and 15:1 over a wide range of operating loads at 1500 rpm. Results showed that the operating range of the engine at 8.5:1 CR reduced when biogas was utilized in the engine instead of methane. However, the operating range of the engine for biogas extended with an increase in CR—an increase from 9.6 N-m-16.5 N-m to 2.8 N-m-15.1 N-m was observed when CR was increased from 8.5:1 to 15:1. The brake thermal efficiency improved from 13.7% to 16.3%, and the coefficient of variation (COV) of indicated mean effective pressure (IMEP) reduced from 12.7% to 1.52% when CR was increased from 8.5:1 to 15:1 at 8 N-m load. The emission level of carbon dioxide was decreased with an increase in CR due to an improvement in the thermal efficiency and the combustion process.

A review of conventional and renewable biodiesel production

The need for sustainable fuels has resulted in the production of renewables from a wide range of sources, in particular organic fats and oils. The use of biofuel is becoming more widespread as a result of environmental and economic considerations. Several efforts have been made to substitute fossil fuels with green fuels. Ester molecules extracted from processed animal fats and organic plant materials are considered alternatives for the use in modern engine technologies. Two different methods have been adopted for converting esters in vegetable oils/animal fats into compounds consistent with petroleum products, namely the transesterification and the hydro-processing of ester bonds for the production of biodiesel. This review paper primarily focuses on conventional and renewable biodiesel feedstocks, the catalyst used and reaction kinetics of the production process.

Bio-energy and CO2 emission reductions: an integrated land-use and energy sector perspective

Biomass feedstocks can be used to substitute fossil fuels and effectively remove carbon from the atmosphere to offset residual CO2 emissions from fossil fuel combustion and other sectors. Both features make biomass valuable for climate change mitigation; therefore, CO2 emission mitigation leads to complex and dynamic interactions between the energy and the land-use sector via emission pricing policies and bioenergy markets. Projected bioenergy deployment depends on climate target stringency as well as assumptions about context variables such as technology development, energy and land markets as well as policies. This study investigates the intra- and intersectorial effects on physical quantities and prices by coupling models of the energy (REMIND) and land-use sector (MAgPIE) using an iterative soft-link approach. The model framework is used to investigate variations of a broad set of context variables, including the harmonized variations on bioenergy technologies of the 33rd model comparison study of the Stanford Energy Modeling Forum (EMF-33) on climate change mitigation and large scale bioenergy deployment. Results indicate that CO2 emission mitigation triggers strong decline of fossil fuel use and rapid growth of bioenergy deployment around midcentury (~ 150 EJ/year) reaching saturation towards end-of-century. Varying context variables leads to diverse changes on mid-century bioenergy markets and carbon pricing. For example, reducing the ability to exploit the carbon value of bioenergy increases bioenergy use to substitute fossil fuels, whereas limitations on bioenergy supply shift bioenergy use to conversion alternatives featuring higher carbon capture rates. Radical variations, like fully excluding all technologies that combine bioenergy use with carbon removal, lead to substantial intersectorial effects by increasing bioenergy demand and increased economic pressure on both sectors. More gradual variations like selective exclusion of advanced bioliquid technologies in the energy sector or changes in diets mostly lead to substantial intrasectorial reallocation effects. The results deepen our understanding of the land-energy nexus, and we discuss the importance of carefully choosing variations in sensitivity analyses to provide a balanced assessment.

Environmental Sustainability Assessment of Molasses-based Bioethanol Fuel in Pakistan

Bioethanol is promoted as a transportation fuel due to its perceived benefits; reducing greenhouse gas (GHG) emissions, substituting fossil fuels, enhancing energy security, and promoting the rural economy. This study aims to evaluate the availability potential, energy performance, and environmental sustainability of bioethanol from sugarcane molasses in Pakistan. It was found that the current potential of molasses-based bioethanol is enough to replace around 7% of total gasoline consumption in the country. The results indicated that the use of E10 (10% blend of bioethanol with gasoline) instead of gasoline would result in the reduction of GHG emissions by 8%, human carcinogenic toxicity by 3%, and fossil resource scarcity impacts by 9%. However, E10 has comparatively higher impacts than gasoline on acidification by 20% and on freshwater eutrophication by 43%. Further benefits of molasses-based bioethanol were evident in terms of high energy gains where each MJ of the total energy input provided about 2 MJ of energy output from bioethanol and each MJ of fossil-based energy input resulted in the production of around 6 MJ of energy output from bioethanol. Furthermore, considerable improvements in performance were indicated by contemplating different existing practices and plant arrangements.

A review on the prospective use of chicken manure leachate in high-rate anaerobic reactors

The global production of chicken arises over the world, which leads to increasing manure generation and environmental problems. Anaerobic digestion (AD) is a well-known process to produce biogas from biomass. Chicken manure (CM) is considered as a feedstock for biogas production due to its high organic load, but there are some challenges to be considered, such as the heterogeneity and the high solid content. To overcome these issues, pretreatments techniques that enhance biogas production could be used. In this context, the use of the leachate process for CM pretreatment could be a novel alternative producing an easily biodegradable liquid substrate for AD. High-rate anaerobic reactors (HRAR), as mature technologies in the market, represent an opportunity for its technological simplicity and economy. Improvements of AD with leaching pretreatment were studied considering the use of HRAR as recent achievements to produce biogas and perspectives in the world. For mathematical modeling, the leaching process with CM as substrate, Computational Fluid Dynamics (CFD) methods are presented as a numerical simulation tool for a better understanding of the process. The integration of the leaching-efficient AD process in a biorefinery approach in a developing country using CM as a substrate could diversify its productions, in addition to reducing emissions to the environment. The results obtained became a tool for decision-makers and researchers about the implementation of leaching pretreatment prior to high-efficiency technologies for CM management in Poultry Farms to obtain the highest benefits, not only in Cuba but also in other developing countries with a similar situation. Production of biogas from CM is a technical solution that contributes to substitute fossil fuels by renewable energy.

Impact of sector coupling on the market value of renewable energies – A model-based scenario analysis

Decarbonizing the energy supply by substituting fossil fuels with renewable energy sources (RES) is a key task for the coming decades in order to achieve the EU's ambitious climate protection targets. Information about the possible development and marketability of RES in the electricity sector is essential for assessing future funding needs. However, rising shares of fluctuating RES generation in the energy system reduce the average market prices and increase price volatility. Balancing price variations requires a considerable degree of flexibility. Additional flexibility in the electricity market through closer interconnection between the electricity sector and other demand sectors makes it possible to keep the market values of RES closer to the general market price level, irrespective of their shares. Such sector coupling can thus contribute to a cost-efficient transition to a low-carbon energy system. This paper examines the impact of efficient sector coupling on the market values of RES in a European energy system with ambitious decarbonization. We analyze different scenarios by applying the Enertile model, which uses an integrated cost optimization approach with flexibility options due to sector coupling and provides a detailed future development of RES. In our analysis, we examine three flexibility options: smart charging of electric vehicles, decentralized heat pumps in buildings, and multivalent district heating grids. We show that the flexible use of electricity in district heating has a significant impact on market values, while the impact of both flexible electric vehicle charging and flexible heating with heat pumps is rather small. Short-term flexibility due to load shifting of the charging or heating process shows only a limited effect on market values. Fuel switching in district heating, however, offers the possibility to change the absolute demand for electricity in direct response to RES feed-in and drastically reduces the curtailment of RES.