Prospects of Alternative Transportation Fuels

Energy is a basic requirement for economic development. Growing energy consumption has resulted in world becoming increasingly dependent on fossil fuels such as coal, oil and gas; therefore, it becomes necessary to develop a sustainable path of energy. Gaseous fuels and biofuels seem to have the potential to contribute significantly to India’s energy security. This monograph shows the current status of different alternative fuels and describes some advanced techniques to improve the quality of alternative fuels. Utilization of these alternative fuels in existing vehicles is another important aspect, which has been covered in this monograph.

Due to rapidly increasing energy consumption rate, access to clean, affordable and sustainable energy has become one of the important factors for economic development of any country. Depletion of petroleum reserves and associated issues related to their utilization in internal combustion (IC) engines motivated researchers to explore such alternative energy resources. In this quest, researchers have developed various solar-based and water-based energy generation methodologies; however, these techniques are not mature enough to fulfil the current energy requirements of transport sector. Therefore, appropriate alternatives to liquid fossil fuels (mineral diesel and gasoline) have been explored, in which gaseous fuels (compressed natural gas (CNG), liquefied petroleum gas (LPG), dimethyl ether (DME), Hydrogen, HCNG, etc.), biofuels [alcohols, biodiesel, straight vegetable oil (SVO)], synthetic fuels, etc., are the important ones. Utilization of microbes to produce biofuels has also gained significant attention of researchers. This chapter provides a snapshot of the current energy landscape, available options and discusses the path forward, which can be used for the development of sustainable and secure energy options for our nation.

Socioeconomic development of a nation primarily depends on energy as a vital input, and thus, the energy strategy of a nation targets at energy security as well as at energy efficiency for its economic development. Owing to the rising population, limited crude oil reserves due to fast depletion of conventional fossil fuel sources along with rising greenhouse gas (GHG) emissions, there has been a global concern for energy security and environmental protection. In view of these concerns, energy production especially from sustainable sources has become the most imperative concern for national as well as for international policies. In this perspective, hydrogen has gained substantial global attention as clean, sustainable, and versatile energy carrier. Existing hydrogen production technologies mainly rely on photochemical, thermochemical processes which are high energy intensive and make use of conventional fossil fuel sources as feedstock either directly or indirectly. On the contrary, hydrogen production processes through biological route are less energy intensive, can be generated from renewable sources from organic wastes, and thus are sustainable. Biologically, hydrogen can be produced by few of the unique microbes/algae though four distinct approaches: (a) biophotolysis of water using algae/cyanobacteria, (b) photodecomposition (photofermentation) of organic compounds using photosynthetic bacteria, (c) dark fermentative hydrogen production using anaerobic (or facultative anaerobic) bacteria, and (d) hybrid biological hydrogen production through integration of dark fermentation process with photofermentation process. This chapter highlights in prospects and limitations of biohydrogen production process including recent developments on this domain. In addition, this chapter also sheds light on economic feasibility of biohydrogen production processes and addresses the need for integration of these technologies with production of value-added bio-based products in a biorefinery approach.

With the scarcity of fossil fuels as well as stringent emission norms, there is a huge shift in the automotive research to develop engines capable of utilizing alternative fuels with superior fuel efficiency and lower emissions. Several alternative fuels have been tried out to cater to ever-increasing needs of better efficiencies and reduced emission. One of the most promising fuel researchers are currently evaluating is hydrogen because of its better combustive properties compared to conventional fuels, as well as the absence of carbon in its molecular structure. While there are various advantages of using this fuel for our needs, there are few challenges also, which form a roadblock for making hydrogen a commercially viable fuel. This chapter discusses the efforts made by several researchers over decades to make hydrogen a suitable fuel for future internal combustion engines.

The rapacious growth of transport sector in last few decades has made it one of the major contributor of air pollution. This has pushed the governments of different countries around the globe to impose stringent pollution norms on vehicular emissions. Therefore, these days design of automobile engines is greatly influenced by criteria of reducing the emissions. Amongst all automotive engines, compression ignition engines are especially prominent in long-hauling scenarios due to their higher thermodynamic efficiency and better low-end torque. However, they are notorious for the black smoke which they emit. Alternative fuels and combustion technologies are explored extensively to reduce the emissions and improve the combustion efficiency further in such engines. Amongst different alternative fuels explored by researchers, hydrogen is attractive due to its extremely clean combustion properties. This work critically evaluates the amenities and shortcomings of the hydrogen as a fuel in compression ignition engines. Application of hydrogen in advanced compression ignition technologies such as HCCI and PCCI is also explored.

This chapter discusses implementation of hydrogen-enriched compressed natural gas (HCNG, also called hythane) in automotive engines. Existing passenger vehicles (PV) and commercial vehicles (CVs) are mainly dependent on fossil fuels such as gasoline and diesel. Due to depleting fossil fuel reserves, stringent emission legislations and on-road fuel economy requirements, IC engines are required to use cleaner alternate fuels. Several prominent alternative fuels have emerged such as alcohols, biodiesel and LPG but none of them are widely accepted for large-scale commercial applications. However, most countries have implemented blending of gasoline with alcohol (up to 5–15% v/v) for commercial applications. Compressed natural gas (CNG) has also been widely successful as a commercial automotive fuel. Over last couple of decades, number of CNG vehicles on the roads has increased drastically worldwide. CNG as an automotive fuel is commercially implemented for PVs and heavy-duty CVs. Most important quality of CNG is its lower emissions and it is accepted as a clean transport fuel. However, CNG suffers from severe shortcomings, especially related to its chemical and physical properties such as lower diffusivity, lean-burn limits, high ignition energy requirement, lower flame speed and large flame quenching distance compared to hydrogen. To improvise the properties of CNG as well as for implementing hydrogen for automotive applications, drawbacks of CNG are countered with hydrogen blending. This mixture is known as hydrogen-enriched compressed natural gas (HCNG/H₂CNG or hythane). HCNG also improves feasibility of implementing hydrogen in automotive industry, which otherwise has serious safety concerns because of low ignition energy and wide flammability range of hydrogen. In this scenario, HCNG is fast emerging as a feasible alternative fuel to meet stringent emissions and fuel economy norms with minimal increase in cost and hardware of existing conventional gasoline/diesel engine.

The balance between production and consumption of energy is an important factor, which drives future direction of energy resource development. This largely depends on the decision made by producers, consumers, and governments. The deciding factors for aforesaid choices are their cost, quality, reliability, convenience, and social impact. Globally, the most commonly used automotive technology includes Otto- and diesel-cycle engines. Consequently, their fuels are gasoline and diesel. “Alternative fuels” are those existing fuels, which are neither gasoline nor diesel. Commonly available alternative fuels are alcohols, vegetable oils, and their derivatives such as biodiesel, gaseous fuels (natural gas, hydrogen, and liquefied petroleum gas), ethers, etc. Alcohols are oxygenates of primary hydrocarbons with hydroxyl groups. Presence of oxygen in them contributes to smoothness of combustion process in the IC engines. This results in cleaner burning characteristics compared to fossil fuels. Also, alcohols can help in lowering emission of hazardous gases and can reduce dependency on non-renewable energy sources.

Methanol and DME are emerging as greener substitute of gasoline and diesel, respectively, due to soot-free combustion and low NOx emissions with high EGR of these fuels. Focused research efforts are thus needed not only for developing technologies but also on defining complete value chain to establish sustainable production routes. Majority of the present methanol and DME production processes utilize coal and natural gas as the feedstock, whereas other feedstocks are not found techno-economically viable for commercial plants. Thus, there is a significant research gap and scope of innovation to make these fuels particularly from alternate resources like biomass, bio-oil, and carbon dioxide. This chapter delineates pervasiveness and potential of methanol and DME in the world as fuel, the chemistry, and the sustainability of different pathways for their production from each of the possible feedstock like coal, petcoke, natural gas, biomass, and carbon dioxide.

Due to the scarcity of fossil energy sources and high combustion generated pollution, new alternative greener energy sources became the necessity of the time. Biodiesel is a potential alternative for depleting energy sources since it is produced mainly from vegetable oils and animal fats, which are a renewable resource and are biodegradable and non-toxic. The production process of biodiesel involves heating and mixing triglyceride with methanol (or ethanol) in the presence of various catalysts. Currently, biodiesel is produced via transesterification reactions catalyzed by chemical catalysts, which produces higher fatty acid alkyl esters in shorter reaction time. The amount of electricity required for heating and mixing in this process need to be replaced with renewable resources. An effective means for minimizing the amount of power required to drive chemical reactions to completion is proposed through the use of various solar systems. In this study, CSP is used to incorporate solar energy for biodiesel production. Experiments are conducted with various solar techniques and with different process parameters to propose the optimized solution. Through the utilization of solar energy, the generation of carbon dioxide waste during biodiesel production has been eliminated. Biodiesel produced is comparable to the petro-diesel in properties and production process economical.

Millions of tons of solid wastes are produced as a result of various household, agricultural, and industrial activities around the globe every year, which if not managed and disposed properly can create serious health and environmental issues. At the same time, huge amounts of coal, oil, and natural gas are burnt daily to generate electricity and power to run domestic, workplace, and industrial appliances. The excessive and un-managed use of fossil fuels has not only put pressure on already limited resources, but has also resulted as major contributor of environment pollution. The scientific community has been continuously searching for the renewable and alternate sources of fuel on one hand and an amicable solution to manage the waste on the other hand. These two biggest challenges before the world presently, if diagnosed and managed scientifically, can provide solution to each other by providing clean renewable energy from solid and liquid waste materials. Waste-to-energy technologies physically convert waste matter into more useful forms like bioethanol, biobutanol, biogas, biohythane, CNG, and syngas through various processes such as combustion, pyrolysis, gasification, or biological treatments. The processes like anaerobic digestion and fermentation and combinations of various technologies can be used to tackle the rising demand of energy. Utilizing these wastes would not only provide supply of fuels on sustainable basis but would also be helpful in conserving our environment. The selection of appropriate raw material and efficient technology for biofuel production is of immense importance in order to produce high-quality product with reduced environmental impact. Various aspects of waste utilization through clean renewable source of energy for sustainable development of society are of paramount significance in today’s context and need immediate attention.

Increasing global energy demand is being substantially contributed by the bioenergy sector. For the rural communities, bioenergy provides opportunities for social and economic development by improving the waste and other resource management. The contribution of bioenergy proves to be significant in terms of maintaining social, economic as well as environmental health, ensuring energy security. Biomass, when converted to bioenergy, may undergo different suitable processes. Thermochemical conversions are no exception. The process technologies include combustion, torrefaction, pyrolysis, and gasification. All these processes having the common backbone of thermal decomposition are optimized by different factors and yield specific products of different states such as solid, liquid, and gases. The characteristics of generic types of reactors used to carry out such processes are described with their special features, advantages, and disadvantages. Though researches have called for three types of possible biomass for conversion such as lipid, sugar/starch, and lignocellulose in the present chapter, conversion of lignocellulosic biomass feedstock is focused. It has been discussed how the variations in composition of biomass at optimized process flow differ the quality and quantity of potential product yields.

Pyrolysis oil produced using lignocellulosic material is an alternate source of energy. Pyrolysis is an attractive option for the conversion of lignocellulosic biomass into liquid, pyrolysis oil, and gaseous hydrocarbons and is considered as an emerging and challenging research area in the current scenario of renewable energy. To ensure the production of “drop-in” liquid hydrocarbons from biomass, there is urgency of integration of pyrolysis process with conventional petroleum refinery’s trillion dollars worldwide infrastructure. This will happen into reality only after going through the necessary actions and precautions at various process development stages, such as biomass pyrolysis, pyrolysis oil upgrading, and effective integration of biomass pyrolysis with refinery. Herein, the opportunities lie in upgrading of pyrolysis oil in petroleum refinery units such as catalytic cracking and steam reforming, is described. The challenges arise ahead of pyrolysis oil upgrading in fluid catalytic cracking (FCC) approach have been reviewed. The extent of pyrolysis oil coprocessing with vacuum gas oil (VGO) in a refinery FCC unit is discussed. The advances in biomass pyrolysis process integration schemes with petroleum refinery have been revealed.

Diesel engines are used in heavy transportation vehicles and heavy machineries as they produce higher torque at low speeds for a given power meeting the primary requirement for a heavy engine. Moreover, diesel engines provide higher compression ratio and, if gasoline has to be used in bigger engines, they will produce higher knocking due to preignition. Therefore, the use of diesel in heavy vehicles is indispensable; however, exhaust gases emerging from the engine contain pollutants predominantly nitric oxides (NO_x) and particulate matter (PM). Nowadays, there is an extensive focus toward improving emission characteristics and enhanced combustion properties with pure diesel oil in an IC engine. One of the recent ways to achieve the similar characteristics is to develop a water-in-diesel oil (W/D) nanoemulsion that reduces the pollutants and at the same time enhances combustion properties. Therefore, the proposed chapter is aimed to discuss the advancement and opportunities in W/D nanoemulsion fuel preparation using different surfactants and additives that provide improved emission characteristics and engine performance.

In present chapter, the potential usage of peroxy-fuels (usually known as organic peroxides) either in technically pure or in a blended form in engine combustion processes are explored. Although as additives (in small quantities <5% to conventional fuels, e.g., diesel, gasoline) peroxy-fuels are well known for many years their commercial applications as a main or primary fuel are not investigated in detail as such except a few. Their thermal instability and energy density demand great care during processing, which restricts their commercial exploitation. However, once the issues with safety are resolved they can be much more advantageously employed than conventional fuels. Some of these advantages are significant amount of fuel saving, reduction in amount of inducted air, or even the complete absence of air, i.e., anaerobic combustion, smaller volume of combustion (chamber), oxygenated fuel quality, and low emissions. An idea to develop the components of an engine operating solely on peroxy-fuels is also introduced. The engine concept is based on single and multiple injectors in a cylinder with special material coating to ensure a temperature-controlled processing.

In the past few decades, rapid technological advancements have resulted in significantly fast depletion of petroleum resources. Extensive utilization of gasoline and mineral diesel in automobiles sector has led to an increase in the worldwide fuel consumption. Today compression ignition (CI) engines are being widely used in light-duty and heavy-duty vehicles, mainly because of their higher efficiency, greater reliability, and superior fuel economy compared to gasoline engines. However, CI engines experience major drawbacks of very high emissions of oxides of nitrogen (NO_x) and particulate matter (PM). Although several after-treatment devices such as lean NO_x trap (LNT), diesel particulate filters (DPFs), diesel oxidation catalysts (DOCs) are being used to meet stringent emission norms, however, high initial cost, operational issues, and system complexity put serious limitations on their usage. Therefore, researchers have been actively working to explore and develop new combustion strategies such as low-temperature combustion (LTC) in order to control harmful exhaust emissions. Utilization of alternative fuels in these advanced combustion concepts has given a new direction to IC engine research through which issues such as rapid petroleum consumption rate and engine exhaust emissions can be resolved simultaneously. This chapter describes various derivatives of LTC technique and methodology for utilization of various alternative fuels.

Most widely acceptable, new-generation alternatives to the fossil (diesel and gasoline) fuels are alcohols, biodiesel, hydrogen, dimethyl ether, and natural gas. Current supply situation of these alternative fuels does not allow for a full replacement of the fossil fuels. For achieving the stringent emission norms (i.e., beyond EURO V or Bharat Stage V), engine manufactures are facing challenges in terms of engine technology upgradation while simultaneously controlling the cost for design and modification of the engine and fuel injection equipment for blending as well as using alternative fuels. This chapter reviews the fuel injection equipment technology employed worldwide for the alternative fuels (or its blend with the fossil fuels) and suggests important modifications. The injection strategy optimization, which includes understanding the fuel injection systems’ requirements and the interplay between various injection parameters for different fuel blends, is also discussed.