What is it?
Ethyl alcohol, also known as ethanol, is the proper name for grain alcohol "spirits." In academic organic chemistry, this substance is also known as ethyl hydroxide.
The fermentation of sugar into ethanol is one of the oldest chemical processes known to humanity. Since the mid-twentieth century, ethanol has been produced for industrial use as a by-product of petroleum refining. It has since become a partial replacement fuel for gasoline-powered engines. Since most of the ethanol consumed in automotive engines today is derived from plant matter, modern-day gasoline is a partial bio-fuel.
Retail gasoline typically contains ten percent ethanol. Ethanol, like methanol and other short chemical chain alcohols, absorbs water and also dissolves into water depending on which is the greater molecular quantity.
If contact with water is excessive, the quality of ethanol-blended fuel would degrade, but an engine would still run.
For an engine to run on a gasoline/alcohol mixture that exceeds ten percent ethanol, it has to be modified, leading to "flex-fuel" cars. From 1908 until Prohibition went into effect, Model "T" Fords were adapted to run on ethanol by modifying internal engine parts. A hundred years later, we see history repeating itself in order to take advantage of readily available ethanol.
World ethanol production for automotive fuel tripled between 2000 and 2007 from 13 million to more than 41 million metric tons. International trade in ethanol and bio-diesel has been small so far (about 2.5 million tons per year over 2006-07), but is expected to grow rapidly in Brazil, which reached a record high of about four million tons of ethanol fuel export in 2008. Brazil is the largest exporter and the US is the largest importer of ethanol. The US also exports a small quantity of ethanol.
How is it shipped?
In the United States, ethanol is shipped almost exclusively in rail tank cars and in tank barges from the chemical plant where it was produced to the refinery or the gasoline blending plant, where it's blended with gasoline. Additionally, large quantities of ethanol are shipped from one region to another on tank ships.
Domestic tank vessels are inspected and certificated under Title 46 of the Code of Federal Regulations, Subchapter "D" (rather than subchapter "O") because alcohol has a relatively low danger threat. If an alcohol-carrying tank ship is of foreign registry, it must have been issued the appropriate certificate of compliance by the Coast Guard, just as an oil tanker would be required to have in order to trade in the United States.
Ethanol is shipped and stored at ambient temperature and atmospheric pressure and, like gasoline and diesel fuel, is never heated prior to being pumped through a hose or pipeline.
Why should I care?
Ethanol is a grade "C" flammable liquid, with a closed cup (sealed lid) flashpoint of 12.8oC, meaning it can be expected to be above its flashpoint in warm weather.
Gasoline is always above its closed-cup flashpoint of -39oC, but automotive diesel fuel is almost always transported and stored below its 52oC closed-cup flashpoint. Therefore, the level of concern among transportation workers handling ethanol is midway between gasoline and diesel fuel.
Ethanol, like other alcohols, is somewhat corrosive. However, there is little concern for the structure of an ethanol-carrying barge or its pumps and piping because the tanks are inspected (for certification) by the US Coast Guard and because ethanol is only mildly corrosive.
As far as the stability and seaworthiness of the vessel is concerned, it's a physical impossibility to overload a barge because the specific gravity of ethanol is considerably lower than fresh water: 0.79 (at 20oC) versus 1.00.
The principal concern is for the flammable vapours.
One characteristic of ethanol vapour that causes concern is the width of its flammable range. Ethanol's range, from 3.3 to 19.0 percent (by volume in air) is considered somewhat wide in comparison to gasoline's narrow range of 1.4 to 7.4 percent. The wider the range, the greater the chance of a flammable mixture (of air and vapours) should a leak or spill occur. Since ethanol is heavier than air, its vapour spreads out downwind and downhill, hugging the ground or deck.
There has been only one maritime tragedy during the transportation of ethanol where the US Coast Guard became involved. On February 28, 2004, approximately 50 nautical miles off the Virginia coast, a foreign-flagged chemical tank ship exploded and sank en route from New Jersey to Texas.
The ship was also certificated to carry methyl tert-butyl ether (MTBE) while trading with the US. While en route to Texas, the tanks that had previously contained MTBE were empty, and the crew was engaged in tank cleaning when the incident occurred. The ship sank with 11,500 tonnes of ethanol and 700 tonnes of fuel.
Only six crewmen survived. In a situation like this, the ethanol dissolves into the seawater and evaporates into the air quickly, but the oil slick from the fuel remains an environmental concern for several days. If this had happened in port, in addition to the human tragedy, it would have been an environmental and economical disaster.
The short-term exposure limit is 1,000 parts per million (ppm). Exposure to a concentration of ethanol vapour of more than 1,000ppm may cause headache and eye irritation, which was the case during the rescue operation off the Virginia coast. Exposure to ethanol vapour also causes dizziness, double vision, and other classic alcohol intoxication symptoms. A victim of vapour exposure should always be removed to fresh air.
What is the Coast Guard doing about it?
The Coast Guard monitors ethanol spill statistics. Over the past six years, there have been only two ethanol spills from tank vessels in the US while loading or discharging, and they were both under 19 litres. Therefore, there is little concern over the handling of ethanol by the tank barge segment of the maritime industry. Waterfront facilities have averaged exactly one spill a year, and only one of these spills has been more than 378.5 litres.
Because industrial ethanol usage (as a bio-fuel) is increasing in society, more ethanol-carrying tank vessels are being inspected for certification, and the number of qualified inspectors in the field is being increased.
The following is an edited version of an article published in the US Coast Guard journal Proceedings, Spring 2010 issue