EEB is produced in a complex reaction mixture along with at least 2 high-value chemicals used as intermediates in several manufacturing sectors; the resulting biofuel is a mix of products from esterification of polyhydroxyalkanoates (PHA) with ethanol. This process when combined with a related technology to produce alcohols from complex feedstock can realize an integrated biorefinery that sustainably and cost effectively converts low-value, high-volume feedstocks into a suite of bioproducts and biofuels.

The technology has received a California Energy Commission (CEC) grant to develop the process for production of EEB (also called E-xtra by Vitruvian) from WWTP (waste water treatment plant) biosolids and a National Science Foundation (NSF) SBIR Phase 1 grant to characterize EEB as a fuel additive/oxygenate for both gasoline and diesel.

Vitruvian has modeled production costs at $2.58-3.73 per gallon. The WWTP economics as a biorefinery become very favorable with an estimated potential net profit of $2.2 million per year at a 200,000 person WWTP when the crude product is further separated into purified chemicals, these are then sold and the chemical sales’ revenues are used to subsidize the cost of the biofuel.

The EEB process first ferments the feedstock to produce acetate and other volatile fatty acids. Data collected with colleagues at the University of Alabama have shown 70-90% conversion of feedstock to SCFAs (short chain fatty acids). The SCFAs are then biologically converted to a carbon storage compound (PHA) using a mixed microbial community of resident microflora. The PHA production process is directed by controlling environmental parameters to direct the metabolism of the microbial community.

The stream containing the PHAs is then reacted with an ethanol stream containing an acidic catalyst. This product mixture (EEB with similar compounds) is then purified to isolate the biorefinery products. The modeled process is able to convert all biosolids at a ratio of ~8:1 (biosolids to total bioproducts w/w) and yields an EROEI (energy return on energy invested) of 1.75, according to Vitruvian’s analysis.

EEB is a mixture of compounds that result from the coupling of ethanol or other alcohol molecules with monomers derived from the depolymerization of PHA. These compounds are more hydrophobic than ethanol and result in the transformation of ethanol or other alcohols into a much more infrastructure-compatible renewable fuel.

Engine studies of E-xtra with diesel and gasoline blends (up to 20%) have showed promising cetane and octane values as well as emissions spectra that are comparable to traditional diesel and gasoline emission levels, accordgin to the company. The data were generated in collaboration with Oak Ridge National Labs and included operation of a diesel test engine and a 2007 Pontiac Solstice on a dynamometer. These data have been generated and are awaiting publication in a journal.

Future plans include building a pilot scale facility to verify modeled assumptions. Talks have begun with a major metropolitan WWTP to gain access to biosolids for fuel production.

Vitruvian currently has 2 issued patents with respect to EEB: Nº 7,641,706 and Nº 8,377,151.