Preface

Natural gas or fossil fuel is a hydrocarbon gas mixture that mainly consists of methane. It also has different amounts of higher alkanes and small amounts of nitrogen, carbon dioxide, helium, or hydrogen sulfide. As it is a colorless and odorless gas, a sulfur odor is usually added to it for its early leakage detection. Over millions of years, under the earth's surface, in the expanse of layers of decomposing plant and animal matter to heat and pressure, natural gas is formed. Plants obtain energy from the sun, which is stored in natural gas in the form of a chemical bond.

Natural gas as a non-renewable hydrocarbon is used as an energy source for cooking, heating, vehicle fuel, and electricity generation. It is also used as a chemical feedstock in the manufacturing of plastics and organic chemicals. Unfortunately, natural gas extraction and consumption is a major cause of climate change. Potentially, natural gas is a greenhouse gas and due to burning, it releases CO2 into the atmosphere. Before being used as a fuel, natural gas must be processed to eliminate impurities and meet marketable specifications. Ethane, propane, butanes, pentanes (and higher hydrocarbons), H2S, CO2, water vapor, helium, and nitrogen are byproducts of this purification step. This book presents new perspectives and future developments regarding natural gas.

In Chapter 1, the authors conduct a life-cycle assessment to evaluate the environmental impact of marine fuel and LNG produced by energy consumption and greenhouse gas emissions. These results are in accordance with the environmental policy of South Korea.

Chapter 2 describes adsorbed natural gas as a cleaner substitute for gasoline to be used as a transportation fuel. Due to specific compression, liquefaction, and adsorption methods required for the storage of natural gas, adsorption-based natural gas is the economic and safe option for its storage.

Chapters 3 and 4 discuss and evaluate fermentation processes for producing value-added products from natural gas. As C–H bonds have high activation energy, extreme separating conditions are required for the chemical conversion of natural gas. Recently, microbiological processes are being investigated.

Chapter 5 reviews various processes used for C3+ hydrocarbon separation from natural gas, with a focus on a polymer-based membrane separation process. C3+ hydrocarbons are one of the significant natural gas impurities that can be used as valuable chemical feedstocks as well as liquid fuel for power generation.

Chapter 6 discusses natural gas consumption in the United States. Due to the COVID-19 pandemic, the forecast of long-term natural gas consumption was obsoleted.

Chapter 7 examines developments in India's goal of increasing its share of natural gas, which is critical to developing India's green economy.

Chapter 8 uses a smart grid concept to discuss the operation of a natural gas system in the framework of energy systems. It also discusses the worldwide application of demand-response principles for increasing the efficiency and operability of natural gas networks.

Chapter 9 focuses on natural gas dehydration, which is normally performed by absorption process using TEG (tri ethylene glycol). Generally, natural gas and TEG thermodynamic parameters must be optimized for successful glycol regeneration.

Chapter 10 discusses biogas as an interesting source of renewable energy. It has high methane content and its use as an alternative to fossil fuels can help minimize energy dependence. The chapter also discusses different aspects of biogas decomposition processes for the simultaneous production of syngas and carbon nanofilaments.

Chapter 11 evaluates the properties of carbon nanotubes as a new material for storing renewable energy. Due to their exceptional characteristic properties, carbon nanotubes are advantageous for energy storage.

Chapter 12 presents 2005–2016 data from twenty-nine nations to study the effect of price and income on natural gas demand elasticities and addresses how to incorporate these characteristics into natural gas demand modeling.

I wish to express my sincere appreciation to IntechOpen for giving us the opportunity to publish this book. I would like to thank all the authors for their significant contributions and for sharing their high-quality research.

> **Maryam Takht Ravanchi, Ph.D.** National Petrochemical Company, Teheran, Iran
