New low-energy desal process could be used to make biofuels


Highly efficient heat exchangers hold the key to Terrabon’s AdVE process, which the company is combining with a biomass process to make transportation fuels and potable water.

FUENTE – CleanTechnica – 24/03/09

Houston-based Terrabon plans to begin engineering work in April on its first commercial plant to demonstrate a new method of desalination using highly efficient heat exchangers.

Terrabon just received approval from the city council of Laredo, Texas, to build and operate the $1.6 million two-year project with partner Texas Engineering Experiment Station. The demonstration project is expected to desalinate 50,000 gallons of brackish well water per day using about five heat exchangers. Construction is expected to be complete in 2009.

CFO Malcolm McNeill told the Cleantech Group that Terrabon’s desalination process has the advantage over reverse osmosis in being cheaper and less energy-intensive. But the technology isn’t limited to well water. Terrabon is in talks to use a related process to turn municipal solid waste into two products in high demand: potable water and transportation fuel.

The technology originated at Texas A&M University, which sold the exclusive worldwide license to Terrabon in 1995. Professor Mark Holtzapple developed the proprietary desalination technology, dubbed AdVE, by refining a commonly understood desalination process, advanced vapor compression evaporation.

In advanced vapor compression evaporation, salty or brackish water is placed against a metal plate that is heated on one side. The result is condensation that separates out the salty materials.

Holtzapple added proprietary heat-exchange techniques that greatly enhanced the heat-transfer rate. AdVE strings together a series of the heat exchangers to pull out the impurities in a stream of water. The resulting process lowers the capital costs and operating costs when compared to a reverse-osmosis desalination plant, McNeill said.

A report from Lux Research last week projected a compound annual growth rate for desalinated water of 9.5 percent over the next decade, thanks to “a rising wave of new water treatment technologies all aiming to challenge the incumbent reverse osmosis.”

In terms of the capital expenditure required, AdVE has an estimated cost of $2.85 per daily gallon of water processed, while reverse-osmosis desalination is about $5.10. Operating costs are projected to have a similar spread: $1.65 per 1,000 gallons for AdVE, and $4.95 for reverse osmosis (RO).

“The heat-transfer coefficient with AdVE is very efficient, while RO is very energy intensive,” McNeill said. “Higher heat transfer means you need less energy to get the same job done, and that’s your biggest operating cost.”

Terrabon sees enormous potential for its water technology and is already in talks with potential clients in Europe.

“The U.S. is behind the curve because it hasn’t taken this problem seriously,” McNeill said. “The Southeastern states, Texas, New Mexico, and even the Northeast are all starting to wake up to it.”

The technology could be used to provide potable water to ships at sea. But the most lucrative application could produce potable water and transportation fuels by combining AdVE with the process that Holtzapple was originally developing at Texas A&M.

AdVE resulted as a spinoff of MixAlco, a biomass-to-fuel conversion process developed by Holtzapple to produce mixed alcohols. In MixAlco, biomass—such as municipal solid waste or energy crops—is fermented. Water is then removed to produce organic salts, which are treated with chemicals to be made into fuels such as gasoline, diesel or jet fuel. AdVE came about as the method by which Holtzapple removed water from the fermented materials in order to create organic salts.

That MixAlco technology alone has been the focus of Terrabon’s activity to-date, and the company is in talks to deploy it. The company spent $3 million to build its SemiWorks plant in Bryant, Texas, which is set to begin fermenting sorghum in the next couple weeks. By April or mid-May, Terrabon expects to see the product from that fermentation. After a few cycles with sorghum, Terrabon plans to use the facility to test the process on municipal solid waste.

Terrabon is working with the city of Port Arthur, Texas, to build a small plant designed to turn 50 tons of waste per day into organic salts, which would then be sent to a local refinery. Engineering work has started, and Terrabon is negotiating with the city on the use of the municipal waste and location of the project.

The plant is estimated to cost $34 million, so Terrabon has applied for funding through the Texas Emerging Technology Fund and the U.S. Department of Energy. Terrabon expects the plant to produce 1.5 million to 1.8 million gallons of gasoline per year.

Once the Laredo and Port Arthur plants prove the technologies, Terrabon expects to be able to move forward with a AdVE-MixAlco combination plant that could take in 200 tons per day of municipal solid waste and 160 tons of additional materials, including lyme, inoculates and sewage sludge. Terrabon says that input could produce 4.5 million gallons of gasoline per year and 85,000 gallons per day of potable water.

“Cities like Laredo are going to need this type of technology, so our hope is the 50,000 gallon per day project in Laredo will lead to a 200 ton per day municipal solid waste processing facility,” McNeill said.

Terrabon is still a small company, with fewer than 10 fulltime employees in addition to the consultants. The founders put about $4 million into the company between 1995 and 2007, much of which obtained the license from Texas A&M. In 2007, an undisclosed investor contributed $1 million, and Terrabon secured some bridge financing in 2008 and early this year.

Now, Terrabon is seeking to raise $5 million in funding, with a portion expected to close in the next couple weeks.


Author: E. Ritch


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