The introduction of new fuels into the market is a unique opportunity to take advantage of new fuel compositions to improve the efficiency and emissions of internal combustion reciprocating engines and alternative fuel feedstocks. However, there are numerous challenges that introductions of new fuels face before they can become first legal, then ubiquitous. This chapter reviews four different case studies related to changing fuel composition. In some circumstances, the fuel formulation was changed in seemingly minor ways, and resulted in the unanticipated consequences. In other cases, a fuel change was desired, but an unexpected barrier slowed the introduction of the fuel change. These case studies should be viewed as opportunities to understand the interdependencies that exist and factors that need to be considered when trying to change the fuel in the marketplace.

Wood gas. Biogas. Syngas. Landfill Gas. Renewable Natural Gas. Production and use of renewable carbon-based gaseous fuels have a history stretching back centuries and even millennia, providing heat, light and power to support both rural development and urban industrialization. The processes used to generate these gaseous fuels can be separated into two categories: thermochemical and biological, producing syngas and biogas, respectively.  Thermochemical conversion processes produce a synthesis gas, abbreviated as syngas, which is a mixture composed primarily of hydrogen and carbon monoxide, but may also contain carbon dioxide and methane.

Gas turbines are able to utilize a wide variety of fuels, including fuels with low- or zero-carbon content. This includes hydrogen (H2), ammonia (NH3), synthetic and renewable natural gas, as well as a range of biofuels. These are sometimes referred to as zero-carbon, net-zero-carbon, or near-zero-carbon fuels. A subset of these fuels have been used to produce power from gas turbines for decades. This chapter will review experience and practical challenges in the use of these fuels in gas turbines for power generation applications, describing case studies for utilizing these fuels in the field.

Gas turbine engines for aircraft applications are complex machines requiring advanced technology drawing from the disciplines of fluid mechanics, heat transfer, combustion, materials science, mechanical design, and manufacturing engineering. In the very early days of gas turbines, the combustor module was frequently the most challenging. Although the capability of the industry to design combustors has greatly improved, challenges still remain in the design of the combustor, and further innovations are required to reduce carbon emissions. Many companies in the aviation industry committed to a pathway to carbon-neutral growth and aspire to carbon-free future in 2008. Additionally, airframers have aggressive goals to reduce carbon dioxide emissions by 50% by 2050 compared to those in 2005. Achieving these goals require technology advancements in all aspects of the aviation industry including airframers, engine manufactures fuel providers, and all the associated supply chains. The focus of this chapter is the influence of one module of the aircraft engine – the combustor.

A major motivation for the development and ultimate replacement of petroleum-based fuels with alternatives is the desire to reduce the carbon emissions (i.e., CO2) created when burning hydrocarbon fuels in prime mover devices. In addition to CO2, combustion of hydrocarbon fuels in air will inevitably create a number of other emissions (e.g., NOx, soot, etc.), which can have detrimental effects on human health or the local (or global) environment. Furthermore, the desire for a more economic and stable fuel supply has also provided impetus for the identification of alternative feedstocks for fuels. With these motivations to find alternative fuels for power generation, it is important to understand how different fuels can impact pollutant formation. This chapter focuses on the fundamentals of pollutant formation in combustion, as well as the impact of various alternative fuels on the combustion generated emissions. This includes carbon monoxide, nitrogen oxides (NOx), and soot. These topics are addressed for a variety of candidate fuels, including hydrogen and ammonia.

Wood gas. Biogas. Syngas. Landfill Gas. Renewable Natural Gas. Production and use of renewable carbon-based gaseous fuels have a history stretching back centuries and even millennia, providing heat, light and power to support both rural development and urban industrialization. The processes used to generate these gaseous fuels can be separated into two categories: thermochemical and biological, producing syngas and biogas, respectively.  Thermochemical conversion processes produce a synthesis gas, abbreviated as syngas, which is a mixture composed primarily of hydrogen and carbon monoxide, but may also contain carbon dioxide and methane.

As the study of our “house,” ecology considers interactions between humans and our environments. Hutchinson noted modern society’s effects, including from overconsumption, on the major cycles of nitrogen, carbon, and other elements, foretelling research on the Earth system. A major driver is agriculture, including the scale of pesticide use, an alarm sounded by Rachel Carson in Silent Spring. Industrial agriculture keeps crop ecosystems in a perpetual early state, Odum contends, trading off calorie production for services provided by more-mature ecosystems, such as water purification. Holling showed that ecosystems can exist stably in different states and be resilient to impacts. Pastoral ecosystems may not have a single equilibrium state, as shown by Ellis and Swift, with implications for development. Species play various roles in ecosystems, and their loss can affect key services, as noted by Ehrlich and Mooney. Conserving biodiversity will benefit from Indigenous knowledge, argue Gadgil and colleagues, including knowledge of the shifting baseline of fisheries, notes Pauly. As Earth urbanizes, rural to urban gradients present a growing research opportunity, McDonnell and Pickett argue.