Alternatives to ethanol


Most voyagers use diesel engines for their vessel’s auxiliary propulsion. To drive their dinghies and tenders, however, most use gasoline outboards. And the gasoline in the marine distribution chain contains ethanol, which can have deleterious effects on engines and fuel systems — even at the 10 percent ethanol formulation. In recent years, 15 percent ethanol formulations have appeared, further exacerbating problems. There’s a variety of companies working on making an alternative to ethanol called isobutanol or biobutanol. This product promises to do the same job as ethanol as a gasoline additive but without many of the associated problems.

One of the companies making biobutanol is a Colorado-based firm called Gevo. Patrick Gruber, CEO and founder of Gevo, recently visited our office and discussed his company’s efforts to ramp up production of biobutanol.

Ethanol is made from corn, but Gevo has developed processes to make biobutanol from corn as well as other carbohydrate raw materials like sugar cane, molasses, bagasse (the stalks remaining after sugar cane has been crushed to extract the juice), rice straw, wheat straw, corn stover, wood, forestry residue and slash.

Since biobutanol is made from plant products like ethanol, what makes it different from ethanol? The difference is the chemical makeup of the two compounds. Ethanol is C2H5OH, while biobutanol is C4H9OH. They’re similar in that they both are carbon and hydrogen with an oxygen thrown in. The difference, according to Gruber, is in the number of carbons. Ethanol has two carbons while biobutanol has four carbons. The two carbons of ethanol are what make it hydrophilic — literally “water-loving.” Ethanol attracts the water in gasoline, which is not a huge problem if the gas is used right away. If, however, the gasoline sits unused for a time, phase separation can occur and the heavier water and ethanol drops to the bottom of the tank with the gasoline on top of it. That mass of water and alcohol is not going to promote reliable combustion! Not only that, but the mixture can also promote corrosion.

Ethanol also has a solvent effect on any gums or resins present and these can precipitate out on carburetor parts, for example, and hinder their function. Ethanol can cause engines to run hot, and it can also affect hoses and seals in a fuel system.

Biobutanol, however, is not hydrophilic and won’t attract water like ethanol does. It has a higher energy content compared to ethanol (82 percent of the energy of gasoline compared to 65 percent for ethanol), and biobutanol can be a drop-in replacement for ethanol because it doesn’t harm fuel system elements.

Gevo has big plans for its biobutanol product. The company wants to sell it in the marine world, in addition to the automotive and jet fuel markets as well. The marine uses for the product should dwarf other uses in the future.
The key element for mariners being able to use gasoline with biobutanol is distribution. According to Gruber, boat owners need to start asking for the product at their local gas docks. Gruber hopes consumer demand will lead to wider distribution of biobutanol blends.

BoatUS, the Washington, D.C.-based boat owner’s association, has long warned of the drawbacks of ethanol in marine use. As David Kennedy, BoatUS manager of government affairs, said in a phone interview, “Right now it’s okay to use up to 10 percent ethanol in fuel, but we would prefer not to have any ethanol in fuel.” And the association has resisted government efforts to increase the distribution of 15 percent ethanol fuels. Independent testing has buttressed BoatUS’ arguments against any increase in ethanol levels. A study undertaken by the National Renewable Energy Laboratory in 2011, for example, showed that outboard engines had a variety of problems when using 15 percent ethanol fuel. The result of testing has shown that, according to Kennedy, “Anything over E10 [10 percent ethanol fuel] is not safe for engines.”

The Gevo company has tested its biobutanol fuel additive in a variety of engines including Yamaha, Mercury, Evinrude, Tohatsu, Honda, Johnson and Volvo Penta, representing these engine types: electronic fuel injection (EFI) four-stroke outboards; carbureted four-stroke outboards; open-loop (CARB 3-star) SD/I and PWC engines; closed-loop (CARB 4-star) SD/I engines; conventional carbureted two-stroke outboards; and direct fuel injection two-stroke outboards.

The test regime included tests of greenhouse gas (GHG) emissions, combustion analysis, cold start, power and performance, runability, winter storage, full useful life endurance/durability, engine teardown and component inspection.

Biobutanol gasoline additives like the product from Gevo have potential to solve some of the issues mariners have experienced with ethanol mixed fuels — including less worry about putting the outboard on the inflatable and getting it to run properly, especially if it has been sitting unused. Of course, small outboards being the quirky beasts they are, they’ll likely always have starting issues, no matter what the fuel additive.

By Ocean Navigator