When the prices of oil and natural gas rise substantially, as they have recently, the attention of consumers and fuel producers naturally turns to alternative fuels. Actually, the term “alternative fuels” is not precise-one should not consider them alternatives to fossil fuels, but as complementary fuels, at least until they are technologically advanced enough to cost-effectively replace fossil fuels.
There have been numerous announcements of new biodiesel plants being constructed (OGJ Online, May 12, 2006; OGJ, Apr. 17, 2006, p. 9). More recently, Green Energy Inc. announced it will unveil its mobile catalytic depolymerization plant on May 31. The process reportedly makes clean diesel fuel from landfill, agricultural, industrial, commercial, medical, and other nonradioactive wastes.
Another technology with potential is coal-to-liquids (CTL). Similar to the more widely known gas-to-liquids, CTL uses coal instead of natural gas as a feedstock. Both processes use the Fischer-Tropsch reaction to convert synthesis gas to liquid fuels.
A recent report says coal has the potential to meet the world’s energy needs in the 21st century. It’s less confident about some of the other energy sources for which hopes now run high.
Sustainable energy
Nonfossil energy sources, which include hydropower, waves, tides, wind, geothermal, nuclear, and solar, are unlikely to significantly help meet growing world energy demand, according to the report by Klaus S. Lackner and Jeffrey D. Sachs of the Earth Institute at Columbia University. The technologies are simply too expensive, are unsafe in the public’s view, or are physically limited.
The report, “A Robust Strategy for Sustainable Energy,” appeared in the latest issue of the Brookings Papers on Economic Activity. One of the conclusions is that “there are no serious long-term (century-scale) shortages of fossil-fuel supply once the interconvertibility of oil and other fossil fuels is taken into account. Even the arrival of ‘peak oil’...would not mean a global energy shortage at today’s prices. However, the transition from oil to other sources of liquid fuel will require a significant lead time.”
In particular, the report states that CTL could provide gasoline, diesel fuel, and jet fuel with crude prices well below current levels. Current estimates state that CTL is competitive with crude at prices of $35-50/bbl. Some studies suggest that the conversion could be done at an even lower cost.
“Even with the most conservative assumptions about learning curves, it appears quite safe to predict that the cost of synthetic oil from coal or other processes, after some transitional pains, will be below $30/bbl,” the report stated.
CTL makes sense from an energy security standpoint; the US, China, and India are all coal-rich countries that are net importers of crude.
Real-world experience
Sasol Ltd. operates the world’s only commercial-scale CTL plant in Secunda, South Africa. Since starting up its Sasolburg plant on Aug. 23, 1955, the company has produced 1.5 billion bbl of synthetic fuel from about 800 million tonnes of coal.
Sasol currently makes about 28% of South Africa’s fuel from coal. The company will inaugurate a commercial-scale GTL plant in Qatar on June 6 and is studying the possibility of constructing two CTL plants in China.
Jet fuel experiment
According to a May 15 article in the Air Force Print News, the US Air Force is planning to test-fly a B-52 Stratofortress powered in part by synthetic jet fuel. The bomber, whose test flight is scheduled for September, will use a fuel blended from crude-derived JP-8 and a Fischer-Tropsch jet fuel produced from natural gas in two of its eight jet engines.
The experiment is part of the US Department of Defense’s Assured Fuel Initiative, which endeavors to secure domestic fuel sources for military needs.
“One of the primary things we are looking at is using a coal-based fuel for aviation use,” said Maj. Timothy Schulteis, as quoted in the article. “One of the big advantages of that is we have a large domestic source for coal-based fuel. The recent rise in cost of fuel has brought us to where many think we are now at the break-even point.”
Because it is an experimental program, the other six engines will use the standard JP-8 jet fuel.
The experiment will determine high-temperature stability, low-temperature properties, compatibility with materials and aircraft systems, engine performance, and emissions.
If the prices of crude and natural gas remain high, CTL could help meet many countries’ energy needs.