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Biorefining Technology Scale-up

Posted on: February 17th, 2011
Source: Biorefining Magazine
Biorefining Magazine March CoverBy Marc Privitera and Christina Borgese

There are few things more satisfying in a chemical engineer’s career than when the first drop of at-rate, at-cost, on-spec product comes off a commercial-scale system. That first drop is the culmination of tireless efforts to scale up from idea to reality, and declares you the champion for that moment.

Scale up begins by defining the factors, levels and responses captured from the bench development effort. A factor is a controllable variable, or knob, that can be turned to a level, or set-point. The response is the characteristic product measurement resulting from the factor at a specific set-point. In feedstock characterization, a common factor is the moisture content, the level is the specific moisture percentage tested in the process system, and the response is the ultimate affect on product conversion.  A designed experiment is a series of tests measuring factor interaction at varying levels to extract meaningful correlations on response affects. This allows an engineer to set boundary limits on both incoming streams and process run conditions for the operators to follow to insure on-spec product.

Factors and responses are measurements that require validated test methods to ensure that decision making information is based on statistically proven repeatability and accuracy against a known standard.

Proving out Supercritical Processing

Posted on: May 13th, 2011
Source: Biodiesel Magazine
Proving out Supercritical ProcessingBy Luke Geiver
Interviews with Christina Borgese and Marc Privitera

When BioFuelBox, the biodiesel process technology company that designed, built and ran a 1 MMgy biodiesel facility in Idaho based on the principles of the supercritical process—high pressure and high temperatures—won the 2010 Technology Pioneer award from the World Economic Forum, one could argue that a new beginning in biodiesel production methods for alternative feedstocks was set. After all, look at the success of some of the previous winners, most you've probably heard of. In 2010, along with BioFuelBox, the social media company Twitter received the same award. In 2007, it was Mozilla and, in 2006, Amryis Biotechnologies received the award. If these don't make a compelling case that the supercritical process for biodiesel production was well on its way to becoming the norm after the 2010 award, consider the winners in 2002, Google and PayPal.


“We took a technology that had been done in labs, and we took it to full scale,” says Christina Borgese, former senior engineer for BioFuelBox. “We were selling product to a corporation that said we had the best biodiesel they’d ever seen.” Unfortunately, that World Economic Forum award didn’t come with a guarantee for future economic prosperity, and today, BioFuelBox is no more, a victim of an extremely difficult financial climate seen in 2010 within the biodiesel industry: an innovative company all but forgotten. Borgese, who says “it was a big accomplishment to have scaled supercritical beyond the lab bench,” is now co-founder, senior engineer and president of PreProcess Inc., along with her partner and other co-founder Marc Privitera, who was also formerly on the BioFuelBox team.

Biodiesel Reaction and Separation Technology

Posted on: September 8th, 2011
Source: Biodiesel Magazine

Biodiesel Reaction and Separation TechnologyThe chemistry and engineering behind the biodiesel process

By Christina Borgese and Marc Privitera | September 08, 2011

Biodiesel reaction and separation methods range from the time-honored large batch tanks with long residence time reactions and water washes for product separation to intensification, enzymatic, and supercritical reactions coupled with distillation and mechanical separation methods. Selecting the best reaction and separation method for the process depends upon the feedstock characterization, a process we covered in the August issue of Biodiesel Magazine. This installment highlights the specific drivers behind selecting the best reaction and separation techniques while considering process throughput, overall conversion efficiency and plant economics.

The biodiesel reactions have three elements for driving the conversion of the feedstock to the finished product: mixing, molar ratio, and residence time. In simple terms, you have to present the reagent molecules with the opportunity, enough energy and enough time to react. It’s kind of like a seventh-grade school dance.

Mixing is the first operation to consider. Mixing drives the reagent interface surface area. The interface surface area is increased by decreasing through shear the dispersed phase liquid droplet size to the smallest size possible. In the usual batch reactor, the mixing is motivated by an agitator. Many high-shear flow strategies have been successfully employed to intensify phase interaction. The number of molecules motivated to react is driven by the surface area of the two immiscible phases.

Quick and Dirty Feedstock Characterization

Posted on: July 11th, 2011
Source: Biodiesel Magazine
By Christina Borgese and Marc Privitera, PE

Practical advice for cash-strapped community-scale biodiesel plants

Feedstock characterization, process conversion and fuel finishing are the building blocks of biodiesel production. Of the three, feedstock characterization is usually underestimated. The lack of depth in the understanding of feedstock’s impact on the business plan has lead to challenges that might have been avoided for smaller scale producers. This article on feedstock is the first of three installments to discuss the building blocks of biodiesel production.


Nontraditional methods to process higher free fatty acid (FFA) feedstocks are more technically complex compared to traditional systems. High FFA feedstocks include yellow grease, brown grease, tallows, and algal oils. Yellow grease is primarily comprised of restaurant and cooking wastes. Brown grease typically comes from grease trap waste, dissolved air flotation  skimmings, agricultural spoils and meat cut waste. Algal oil is only now emerging as another feedstock. Tallows and rendered fats typically have a high existing market value.


The National Renderers Association defines yellow grease as no more than 15 percent FFA and no more than 2 percent MIU (moisture, insolubles and unsaponifiables). The historical reference on FOG, Bailey’s Industrial Oil and Fat Products, defines brown grease as having an FFA level between 15 and 50 percent. There is much debate throughout the industry on how exactly to define brown grease. In reality the nomenclature is inconsequential. What really matters is the actual FFA and MIU content received at the plant and whether or not the system is capable of processing the material. A rookie mistake is negotiating a contract to buy yellow or brown grease without the needed characterization. 
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