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algae fuels: butanol

 

A team of chemical engineers at the University of Arkansas has developed a method for converting common algae into butanol, a renewable fuel that can be used in existing combustible engines. The green technology benefits from and adds greater value to a process being used now to clean and oxygenate U.S. waterways by removing excess nitrogen and phosphorus from fertilizer in runoff.

Algae growth is enhanced by delivering high concentrations of carbon dioxide through hollow fiber membranes that look like long strands of spaghetti. The algae are grown on trough screens.

The researchers harvest the algae every five to eight days by vacuuming or scraping it off the screens. After waiting for it to dry, they crush and grind the algae into a fine powder as the means to extract carbohydrates from the plant cells. Carbohydrates are made of sugars and starches. For this project, Hestekin’s team works with starches. They treat the carbohydrates with acid and then heat them to break apart the starches and convert them into simple, natural sugars. They then begin a unique, two-step fermentation process in which organisms turn the sugars into organic acids — butyric, lactic and acetic.

The second stage of the fermentation process focuses on butyric acid and its conversion into butanol. The researchers use a unique process called electrodeionization, a technique developed by one of Hestekin’s doctoral students. This technique involves the use of a special membrane that rapidly and efficiently separates the acids during the application of electrical charges. By quickly isolating butyric acid, the process increases productivity, which makes the conversion process easier and less expensive.

Butanol has several significant advantages over ethanol, the current primary additive in gasoline. Butanol releases more energy per unit mass and can be mixed in higher concentrations than ethanol. It is less corrosive than ethanol and can be shipped through existing pipelines. These attributes are in addition to the advantages gleaned from butanol’s source. Unlike corn, algae are not in demand by the food industry. Furthermore, it can be grown virtually anywhere and thus does not require large tracts of valuable farmland.

Source: Science Daily

Photo Jaime Brown

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