Viewed from a long-term perspective, the global transportation system relies almost entirely on waste, specifically the carbon-based remains of ancient plants and animals, to power its trains, planes, ships, and automobiles. Yet these fossil fuels are not typically regarded as waste material, but instead as natural resource commodities. In modern parlance, the term waste refers to materials that are discarded due to a lack of value. These economically appealing low-value and negative-value waste materials (or feedstocks) that can be converted into liquid and gaseous transportation fuels are environmentally appealing as well because they can reduce the soil and water impacts of waste. To evaluate the future of waste-derived fuels, it is necessary to consider the demanding nature of the nation’s petroleum-based transportation system, survey the diverse range of waste feedstocks and conversion technologies, and assess the various federal and state policies that are shaping and driving the industry. It is the blend of practical attributes, market opportunities, and policy drivers that defines the industry.
To an aspiring fuel supplier, the market presents several essential facets: established fuels, distribution infrastructure, vehicles, and consumers. Ultimately, consumers form the demand center for the industry and determine the market for waste-derived fuels. Remarkably, the technology used by these consumers has changed little in over a century. In 1862, German inventor Nikolaus Otto built and sold a spark-ignited engine. While not the first to invent the contraption, Otto is generally regarded as the father of the modern gasoline engine. The spark-ignited engine was originally developed with four chambers, or cylinders. A gaseous mixture of a combustible liquid such as gasoline or ethanol is delivered into the cylinder and ignited with a spark that dramatically increases the pressure within the cylinder. Upon ignition, the force from the combustion (oxidation) pushes the cylindrical piston outward, which delivers power to the crankshaft, which in turn delivers power to the transmission. About thirty years after Otto’s engine was developed, German inventor Rudolf Diesel built the first prototype of the compression ignition engine that still bears his name. Within the compression ignition or diesel engine, a less volatile distillate fuel is used. The harder-to-light diesel fuel oxidizes at pressure and delivers power more efficiently through the same mechanical system. One hundred and fifty years later, Otto’s spark-ignited engine and Diesel’s compression-ignited engine still dominate the transportation landscape. While both have been improved extensively in terms of efficiency and emissions, the core concepts remain unchanged.
The genius and allure of Otto’s and Diesel’s designs are revealed by considering the unique demands of the transportation sector compared with the more forgiving requirements of power generation. The generation of heat and electricity can occur at a chosen location, using large, stationary equipment. Coal can be delivered by the ton to a stationary plant. Natural gas can be shipped by pipeline to a power generation facility or to an individual’s home for heating purposes. By contrast, an automobile must be fully mobile to achieve its purpose. While it can be temporarily connected to an energy source, the shorter the duration, the less inconvenienced the driver. The car’s or truck’s engine must be capable of developing torque (circular force) to rapidly drive the wheels over roads for either a few short miles or hundreds of miles in a single day. Since American drivers crave the freedom of the open road, the driver wants to go wherever she wants without first engaging in logistical energy planning for the trip. With about 230 million registered vehicles in the United States, the national interest requires clean-burning vehicles that will not cloud the landscape and endanger health with emissions. U.S. Department of Transportation, Research and Innovative Technology Administration, 2013 Pocket Guide to Transportation. And because U.S. drivers consume between 337 million gallons of gasoline per day or about 4,300 gallons per second from sea to shining sea, the supply must be ubiquitous and plentiful to quench the country’s daily thirst for transportation power. U.S. Energy Information Administration, Oil: Crude and Petroleum Products Explained.