The formation of acidic deposition is largely from the combustion of fossil fuels and the smelting of sulfide ores. Minor natural sources exist such as the formation of hydrochloric and sulfuric acid from gaseous volcanic eruptions.

There are well over 100 gaseous and aqueous phase reactions that can lead to acid formation and more than fifty oxidizing agents and catalysts may be involved. However, in the simplest terms sulfur in fuels is oxidized to SO2 , and SO2 in the atmosphere is further oxidized and hydrolyzed to sulfuric acid. Most nitric acid is formed by the fixation of atmospheric nitrogen gas (N2) to NOx (NO and NO2) during high temperature combustion emissions, followed by further oxidation and hydrolysis that produces nitric acid in the atmosphere. (more…)

With ethanol’s future uncertain, many commentators see the transportation debate evolving into a war between two other technologies—hydrogen-powered fuel cells and battery powered electric vehicles. Some alternative fuel advocates are putting their support behind hydrogen, the most abundant element on Earth. Water, for example, is composed of hydrogen and oxygen molecules. Hydrogen can be produced from water by electrolysis, which separates the oxygen from the hydrogen. It can be used to power hydrogen fuel cells for vehicles (or to provide heat and electricity for buildings). Hydrogen fuel cells work by recombining hydrogen and oxygen—a process that produces electricity, heat, and water. Hydrogen-powered cars, therefore, could be an ideal transportation solution—nonpolluting, zero-emission vehicles that release only water, a natural and completely safe waste product. Also, fuel cells are highly efficient and powerful, and unlike typical batteries, fuel cells will never lose their charge as long as hydrogen fuel is supplied.

Hydrogen fuel cell technologies, however, must overcome many stubborn challenges before they can become a practical source of energy. Perhaps the biggest obstacle is cost; it currently takes more energy to make hydrogen than is produced, and production relies on expensive catalysts made from platinum, a scarce metal. And like biofuels, hydrogen is currently made using fossil fuels, so it is not emissions-free. In addition, liquid hydrogen fuel is highly flammable and must be stored at very low temperatures or under very high pressure, making transport and storage difficult. Switching vehicles to hydrogen fuel cell power also would require building a whole new infrastructure similar to the chain of gas stations that currently dot the landscape. Researchers are hoping to find answers to these problems by searching for other types of catalysts, studying other ways to improve production, and developing better hydrogen storage options.

Hydrogen researchers, however, have been promising breakthroughs since the 1990s with little progress to show for their efforts. Many observers are thus coming to the conclusion that the hydrogen fuel cell is a technology that will not be perfected in the near future. As physicist and climate expert Joe Romm explains, “Neither government policy nor business investment should be based on the assumption that these technologies will have a significant impact in the near or medium-term.” The Obama administration apparently agrees; it submitted a budget for 2010 that sharply cut back on government support for hydrogen projects. U.S. Energy Secretary Steven Chu explained the administration’s problems with hydrogen technology:

Right now, the way we get hydrogen primarily is from reforming [natural] gas. That’s not an ideal source of hydrogen. . . . The other problem is, if it’s for transportation, we don’t have a good storage mechanism yet. Compressed hydrogen is the best mechanism [but it requires] a large volume. We haven’t figured out how to store it with high density. What else? The fuel cells aren’t there yet, and the distribution infrastructure isn’t there yet. So . . . to get significant deployment, you need four significant technological breakthroughs. That makes it unlikely

Congress promptly reversed President Obama’s decision, however, restoring more than $200 million to 190 hydrogen projects around the country.

Air-blown circulating fluidized bed gasifiers are of interest because they produce a good quality, low calorific value (LCV) gas (4–6 MJ/Nm 3 ) and possess a very high carbon conversion efficiency while allowing high capacity, good tolerance to variations in fuel quality, and reliable operation. The high and homogeneously distributed temperatures and the use of particular bed materials, such as dolomite, favor tar cracking. Successful tar cracking can also be achieved using secondary circulating fluidized bed reactors. Also, successful tests on catalytic tar cracking have been performed, for example, by introducing nickel compounds into the gasifier. Sulfur control is made easier because of the significant reduction that can be achieved by adding limestone or dolomite to the gasifier bed. (more…)

The energy efficiencies of various fuel production pathways from well to pump. The efficiencies shown are defined as the energy in a given fuel (available at pumps in vehicle refueling stations) divided by total energy inputs during all Well-to-Pump activities, including the energy content of the fuel. One way to interpret the Well-to-Pump efficiencies in the figure is as the difference between 100% and the energy efficiencies, which roughly represent energy losses during Well-to-Pump stages for making a given fuel available at the pump. As stated in Section 3, Well-to-Pump activities include biomass feedstock production; feedstock transportation and storage; fuel production; and fuel transportation, storage, and distribution. (more…)

At present, in the United States and worldwide, motor vehicles are fueled almost exclusively by petroleum based gasoline (or reformulated gasoline) and diesel fuels. Since the first oil price shock in 1973, efforts have been made to seek alternative fuels to displace gasoline and diesel fuels and achieve energy and environmental benefits. Some of the alternative fuels that have been researched and used are liquefied petroleum gas (LPG), compressed natural gas (CNG), liquefied natural gas (LNG), methanol (MeOH), dimethyl ether (DME), Fischer– Tropsch diesel (FTD), hydrogen (H 2 ), ethanol (EtOH), biodiesel, and electricity. Production processes associated with gasoline, diesel, and each of these alternative fuels differ. (more…)

The spark-ignition and compression-ignition engine and internal combustion engines technologies that are currently employed in motor vehicles were developed more than 100 years ago. These conventional vehicle technologies are fueled by petroleum-derived gasoline and diesel fuels (the socalled conventional fuels). Over the past 100 years, the conventional technologies have been dramatically improved, reducing cost and increasing performance. (more…)

There are different types of vehicle propulsion systems and the transportation fuels that have been studied for their potential to power the vehicles. Gasoline, CNG, LNG, LPG, methanol, ethanol, and hydrogen can be used in vehicles equipped with conventional spark-ignition (SI) engines. Interest in developing efficient, low-emission, spark-ignition direct-injection (SIDI) engine technologies has heightened in recent years. (more…)

It shows Well-to-Wheels Greenhouse Gas emissions of the 23 vehicle/fuel systems. For each system, the bottom bar represents CO2 -equivalent emissions of CO2 , CH4 , and N2O, combined with their greenhouse global warming potentials (GWPs). The top bar represents CO2 emissions only. For the two ethanol pathways (corn and cellulosic ethanol), there are some negative emissions. They represent carbon uptake during biomass growth. The carbon is eventually emitted to the air during ethanol combustion air. (more…)

An important element for the entire infrastructure of hydrogen energy infrastructure is having hydrogen delivery system the safely and efficiently deliver hydrogen from productions sites to end stations. Hydrogen delivery methods are varying widely, most of them depend on the hydrogen production method and end use. Currently, hydrogen is transferred to a limited number of production plants by using pipeline or transported by road via cylinders, tube trailers. (more…)

Hydrogen has many applications when it comes to fuel. It can be used both in internal combustion engines and hydrogen fuel cells. Hydrogen engines are using the same principle the same way as gasoline fuels or hydrogen natural gas burned combustion, while the chemical energy of hydrogen used to generate electricity and heat transmission. Since the electrochemical reactions produced more efficient energy compare to the combustion energy, fuel cells are created more efficient fuel compare to internal combustion engines. In the long term it will benefit to the more efficient hydrogen conversion process. (more…)