Sunliquid cellulose ethanol process reaches demo scale in Germany

By Susanne Retka Schill | July 26, 2012

The Swiss specialty chemicals company Clariant is now operating its demonstration-scale cellulosic ethanol plant in Straubing, Germany. With an annual capacity of up to 1,000 tons (330,000 MMgy), the demonstration facility is scaling up the company’s pilot-scale work by about a factor of 1,000. “The equipment type and specifications in the demo plant will allow scale-up to production scale,” said Markus Rarbach, head of Clariant’s Biocatalysis, Biotech and Renewables Center. “This has been validated by a team of external and internal engineers.”

Pilot-scale work on the Sunliquid process began in 2009 when Sud-Chemie opened its pilot plant at its research headquarters in Munich. Construction on the demonstration plant in Straubing, near Munich, was started in mid-2010. Clariant, which acquired Sud-Chemie last year, says the project represents an investment of about EUR28 million ($34 million).

In development since 2006, the Sunliquid process is a fully-integrated enzymatic hydrolysis with a number of energy-saving aspects, which results in a 95 percent reduction in greenhouse gas emissions when compared to gasoline in a life cycle analysis, according to Clariant. The process uses a hydrothermal pretreatment at very mild process conditions, Rarbach told EPM. “We can use very mild pretreatment because of the superior quality of our feedstock-specific enzymes.”

The company has worked to optimize the cellulose enzyme mixtures for different feedstocks, “to ensure the highest possible space-time yields,” he said. “We optimize the enzyme to work with the process and not the other way around.” A small amount of pretreated feedstock is used as the substrate for on-site enzyme production. “Thus we ensure lowest enzyme cost and are independent of external suppliers.”

The Sunliquid process also involves a specialized fermentation organism that simultaneously converts C5 and C6 sugars into ethanol in a one-pot reaction, achieving high yields. “We are in a position to offer our customers both genetically modified organisms (GMO) and non-GMO,” he added, saying that they don’t comment on the exact nature of the organism used.

Lignin for power and an energy-efficient ethanol purification technology are other features of the Suniquid system, helping to make it energy self-sufficient. Lignin is separated from the sugar solution after hydrolysis and is used for energy generation. “The lignin is sufficient to provide the complete process energy,” Rarbach said. The company has developed an ethanol purification technology that efficiently deals with the lower ethanol concentrations in the fermentation broth when compared to sugar- or starch-based ethanol processes. “Our newly developed adsorption-based technology, specifically isolates ethanol from the broth,” he said, eliminating the energy required for separation in the beer column. The process has been demonstrated with high stability in laboratory and pilot tests, he said, saving up to 50 percent energy when compared to conventional distillation. “Now it goes to demonstration scale.”  

While intending to become a process provider, and not an ethanol producer, Clariant does expect to take a more active role in building the first commercial-scale plant using the Sunliquid process. 

In a statement following the inaugural ceremonies held July 20, Clariant pointed out the the demonstration plant will produce up to 1,000 tons of cellulose ethanol from around 4,500 tons of wheat straw. “Studies show that Germany potentially has around 22 million tons of straw that could be used for energy production without compromising essential soil regeneration. This would be sufficient to cover around 25 percent of Germany’s current gasoline requirements.”