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Cooking Up Biofuels

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By Emily Hong, Yale University

Any college student who has ever had to cook and fend for themselves knows the advantages of one-pot cooking. One-pot cooking means no complex culinary wrangling of ingredients or excessive rounds of prep-work: Drop the goods in a pan, add a little heat, and out comes something delicious. Or at least edible.


Now imagine your one-pot recipe is for converting algae — that's right, the green scummy stuff you find in tide pools or at the lake — into a biofuel that you can pump straight into your car. Sounds more like fantasy than Food Network, am I right?

Well, this is exactly what Julie Zimmerman's group at the Yale Center for Green Engineering and Green Chemistry is working on (I worked as an undergraduate research assistant at the center during my sophomore year). Zimmerman and her collaborators aim to achieve the conversion of biomass to biofuels without having to push the chemistry to extreme heats or conditions, as well as streamline the conversion process for maximum sustainability.

biofuel pic

The idea of biofuels (essentially petrochemical substitutes derived from plants and the like) present some interesting opportunities for chemists and scientists interested in sustainable technologies. A broader shift towards biofuels could reduce our dependence on fossil fuels with a renewable replacement. However, biofuels often rely on not-so-sustainably produced feed stocks that are dependent on fertilizers, pesticides, and energy-intensive conversion processes to extract the valuable compounds from the raw plant mass.

So far, life cycle analyses of conventional biofuel production techniques have shown that the conversion of biomass into usable fuel raises real concerns of energy balance: With conventional techniques, the energy required to convert biomass into fuel could cancel out the environmental benefits of this renewable technology.

In an article that will soon be published in ChemSusChem, Zimmerman and her collaborators describe their method for the conversion of triolein to methyl oleate - the transesterification of a triglyceride - in supercritical carbon dioxide and methanol with a heterogeneous catalyst, which builds on previous work on lipid extraction from wet biomass using similar scCO2 dependent conditions. Together, these techniques represent significant advances towards the development of a one-pot conversion of biomass to biofuels.

Transesterification of Triglycerides

Transesterification of triglycerides with ethanol (Dr. Zimmerman's work uses methanol)
Source: File:Transesterification of triglycerides with ethanol.png - Wikimedia Commons

Now think back to that kitchen analogy. Cooking can lead to co-products: for example, the egg yolks and shells you don’t need in that meringue, or the broth you made as a result of boiling vegetables for dinner. Another major advantage of the Yale group’s extraction approach is the commitment to maximize all possible utilities from the biomass, following the old maxim of “using every part of the buffalo.” While it is the lipid fractions that are converted to biofuels, the Zimmerman group can also retrieve nutraceuticals along with leftover proteins and carbohydrates from algae, which can then be converted for use in animal feels. Evan Beach, the Program Manager and an Associate Research Scientist with the Yale Center for Green C..., describes these methods within the concept of a “biorefinery,” which further allows for flexibility regarding “what to do with the biomass depending on market conditions and environmental impacts.”

Again, the analogy of cooking is helpful to understand the power of these techniques to turn renewable biomass into usable products. A potato can be mashed, but it can also be used in soups, turned into fries, or be baked and dressed with sour cream depending on the circumstance. Very few people see raw potatoes as delicious, but with the right culinary skills, their unlimited potential for tastiness is unlocked. Zimmerman’s group is harnessing simple principles to literally turn green into to (black) gold and beyond. Their innovations seem to circle back and serve “sustainability” on many different levels. Now there’s something to toast to.

Emily HongEmily Hong is a junior at Yale University from Nashville, TN. While she is currently majoring in Global Affairs, Emily is a lifelong chemistry nerd who loves Chemistry Cat jokes and the smell of benzaldehyde. In the past she has conducted research on the depolymerization of lignin, and she’s interested in the implications of technology and sustainability in the developing world. Her other activities include varsity fencing, coordinating social media for the Yale Admissions Office, and eating French desserts after studying abroad and working at a bakery in Paris.

This blog was co-published in the ACS Undergraduate blog, Reactions

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