**1. Introduction**

Fossil fuels, which originated from the anaerobic decomposition of carbon-rich dead plants and animals, have continued to dominate the energy source and drive the industrialized world. About 70–80% of the global energy consumption is gotten from fossil fuels [1]. Fossil fuels, comprising coal, oil, and gas, are non-renewable and the main contributor to global warming and climate change. Extraction, refining, and utilization of fossil fuels have caused unimaginable degradation of the environment. Also, going by the rate of consumption, the global oil reserves estimated to be 1.65

trillion barrels may be fully depleted within the next five decades [2]. Also, increased population, accelerated industrial revolution, and increased mechanized farming has continued to cause an increased utilization of fossil fuels and consequently increased emission. The global consumption of fossil fuels was recorded as 121, 531 Terawatthour (TWh), 129,855 TWh, and 136,131 TWh for 2010, 2015, and 2019 respectively. On the other hand, the total carbon dioxide (CO2) emissions were documented to be 31.49 Billion Tonnes, 33.39 Billion Tonnes and 34.35 Billion Tonnes respectively (**Figure 1**). However, fuel consumption and CO2 emission plummeted in 2020 due to the Covid 19-imposed lockdown. With the relaxation of various travel restrictions and increased commercial and industrial activities, fuel consumption and emissions are expected to increase substantially. This is expected to escalate environmental degradation and climate change.

The use of biofuels is one of the panaceas for the unfavorable effects of fossil fuels in diesel engine applications. Biofuels are renewable fuels generated from fresh and living organisms. They usually occur in solid, liquid, or gaseous forms. Biofuels enjoy several benefits like renewability, ecological friendliness, feedstock accessibility, the elasticity of the production methods, and their amenability to existing fossil fuels pipeline infrastructure. Also, biofuels demonstrate matchless capability for the sustenance of the ecosystem [5, 6]. However, the high cost of production, increased NOx emission, and increased engine wear are major setbacks to the use of some biofuels. Also, the conflict between some of the feedstocks with the food chain, undeveloped production technologies, and unfavorable government policies have continued to militate against the wide production and utilization of biofuels in many jurisdictions. Notwithstanding these impediments and complications, biofuels remain a clean, safe, and sustainable replacement for fossil fuels and a strategic resource for CO2 reduction and carbon mitigation to avert the ominous environmental catastrophe [5, 7, 8].

The transport sector utilizes more than 90% of the total fossil fuel products and about 28% of the total global energy and is a major contributor to the emission of dangerous gases [9]. Solid biofuels (wood chips, briquettes, sawdust), liquid biofuels (biodiesel, renewable diesel, bioethanol), and gaseous biofuels (biogas, biomethane,

#### **Figure 1.**

*Global consumption (TWh) and CO2 emission (billion Tonnes) from coal, oil, and gas 2010–2020. Adapted from [3, 4].*

## *Performance and Emission Characteristics of Hydrogenation Derived Renewable Diesel… DOI: http://dx.doi.org/10.5772/intechopen.104820*

syngas) have been used as reliable and environmentally benign candidates for fossil-based fuels. The overall energy consumed in the transportation sector was 110 million terra joule (TJ) in 2015 while 129 billion liters of liquid biofuel were utilized in 2016 and the quantity is predicted to increase to 180 billion liters by 2050 [10]. The number of global on-road vehicles which was about 1.2 billion is projected to increase to 2 billion and 2.5 billion vehicles in 2035 and 2050 respectively [11]. Compression ignition (CI) engines because of their versatility, strength, and multi-faceted usage, have continued to be used as passenger vehicles, construction machinery, agricultural equipment as well as rail and heavy-duty trucks. Fueling these engines with petroleum-based diesel (PBD) fuel will exacerbate the detrimental effects on the health and environment.

To increase the share of renewable fuels in the transportation sector energy mix, renewable energy sources and other less polluting fuels such as electricity, natural gas, bioethanol, propane, biodiesel, jet fuel, and biomethane have been tested. These renewable and less polluting energy sources have been found to meet the huge demand and requirements for bioenergy and secure the energy supply. For example, the deployment of electric vehicles has been plagued with the high cost, infrastructural deficit, and long duration of charging of the battery in many jurisdictions. The liquid biofuels have the advantage of being produced for wastes and other renewable sources with a low carbon footprint, thereby making them a more economically viable option [12]. Globally, more concerted efforts geared at increasing the production and utilization of renewable fuels are needed to achieve Sustainable Development Goals and ensure environmental sustainability. Also, more public awareness and education, targeted policy, and research and development (R & D) aimed at increasing the production and utilization of liquid biofuels should be intensified.

#### **1.1 Motivation, aim, and scope**

Concerns over the environmental, social, economic, and supply of world energy have been addressed by governments in various jurisdictions. Possible solutions include the introduction of biofuel into the energy mix by encouraging and incentivizing the production and utilization of biofuels. The desire to popularize the application of these biofuels, particularly for CI engines applications, has gained considerable attention in recent years. A lot of studies have been carried out and reported on the production and utilization of biodiesel and bioethanol as CI engine fuels. In previous research, Saravanan et al. [13], Khan et al. [14], Krishna et al. [15], and Shirneshan et al. [16], among several others investigated the performance and emission characteristic of biodiesel, ethanol, and biodiesel-ethanol blends on CI engines. The outcomes of their studies showed the benefits and shortcomings of the deployment of these renewable fuels in CI engines with particular attention to Hydrogenated Derived Renewable Diesel (HDRD). In their various studies, they confirmed the superiority of HDRD over biodiesel and PBD fuels for CI engine transport applications. Recently Chia et al. [12] and Kumar et al. [17] demonstrated their preference for HDRD over biodiesel, ethanol, and other liquid biofuels. They cited the superior heating value, excellent transport and storage stability, and non-corrosive nature of HDRD as some of the reasons.

Bearing in mind the ongoing efforts at finding more sustainable renewable fuels to power CI engines, and the various challenges encountered with the usage of biodiesel and bioethanol, the relevant question to ask is how has HDRD performed as an alternative fuel for CI engines? . How effective is HDRD as CI engine fuel from the standpoint of performance and emission characteristics? The motivation for this study is the desire to improve the quantum and quality of information and awareness on HDRD as a transportation fuel to assist consumers, fuel refiners, and engine manufacturers in making informed decisions in fuel selection. The current effort aims to investigate the performance and emission characteristics of CI engines fueled with HDRD.

Overall, the outcomes of this work will equip governments, policy formulating agencies, industry experts, researchers, and the general public with the requisite information on the application of HDRD in CI engines. It is also hoped that research funding bodies will be encouraged to provide more funds for future R & D to stimulate investigation into novel strategies for production and utilization of the HDRD. To achieve this, the article will be divided into subheadings to discuss HDRD as a renewable fuel, performance of HDRD in CI engine, emission characteristics of HDRD as CI engine fuel, implications of HDRD as CI engine fuel, and conclusion. The current effort is, however, limited to a desktop review of published literature on the performance and emission behavior of HDRD in diesel engines.
