New Process for Production of Biodiesel Directly From Wet Algal Biomass Could Reduce Energy and Financial Costs
31 August 2010
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| Process flow diagram for biodiesel production through intracellular lipid hydrolysis and supercritical in situ transesterification (SC-IST/E) using ethanol (EtOH). Credit: ACS, Levine et al. Click to enlarge. |
Researchers at the University of Michigan have developed and demonstrated the feasibility of a two-step hydrolysis-solvolysis process to produce biodiesel directly from wet algal biomass. Their process eliminates the need for biomass drying, organic solvent extraction, and catalysts, and provides a mechanism for nutrient (e.g., N, P, and glycerol) recycling. A paper on the process was published 30 August in the ACS journal Energy & Fuels.
Levine et al. reported that a cursory investigation of the influence of some key process variables resulted in crude biodiesel and FAEE (fatty acid ethyl esters) yields as high as 100 and 66%, respectively, on the basis of lipids within the hydrolysis solids. Considering that about 80-90% of lipids in the original algal biomass were retained in the solids recovered after hydrolysis, the authors noted, the total process yield was somewhat lower.
...dewatering and drying remain energy- and cost-intensive processes. A recent life-cycle assessment (LCA) of algal biodiesel production from Chlorella vulgaris indicated that drying and hexane extraction accounted for up to 90% of the total process energy. These data indicate that drying algal biomass and treating it as a substitute for terrestrial oilseeds in traditional solvent extraction and subsequent transesterification processes is not likely to be a net energy positive route toward sustainable biodiesel production.
A biodiesel production process that obviates biomass drying and organic solvent use for oil extraction could lead to significant energy and cost savings...Herein we propose a two-step, catalyst-free biodiesel production process involving intracellular lipid hydrolysis coupled with supercritical in situ transesterification (SC-IST/E).
—Levine et al.
The team used the alga Chlorella vulgaris as the lipid-rich feedstock (53.3% lipids as FAEE). In the first step of the process, the wet algal biomass (ca. 80% moisture) reacts in subcritical water to hydrolyze intracellular lipids, conglomerate cells into an easily filterable solid that retains the lipids, and produce a sterile, nutrient-rich aqueous phase.
In the second step, the wet fatty acid-rich solids undergo supercritical in situ transesterification (SC-IST/E) with ethanol to produce biodiesel in the form of fatty acid ethyl esters (FAEEs).
Longer time, higher temperature, and greater ethanol loading tended to increase crude biodiesel and FAEE yields, which ranged from about 56-100% and 34-66%, respectively, on the basis of lipid in the hydrolysis solids.
More remains to be understood regarding how whole cells, hydrothermally processed algal biomass, and intracellular constituents influence SC-IST/E and potentially contribute to nonester components in the final fuel product. Additional research and process optimization are likely to improve yields and reduce process inputs (e.g., ethanol), thereby minimizing the overall environmental impact of algal biodiesel production. To be economically viable, biodiesel yields must be above 95% and preferably higher than current norms achieved with alkali-catalyzed processes (~97%).
—Levine et al.
Resources
Robert B. Levine, Tanawan Pinnarat and Phillip E. Savage (2010) Biodiesel Production from Wet Algal Biomass through in Situ Lipid Hydrolysis and Supercritical Transesterification. Energy Fuels, Article ASAP doi: 10.1021/ef1008314
"Additional research and process optimization are likely to improve yields and reduce process inputs (e.g., ethanol), thereby minimizing the overall environmental impact of algal biodiesel production."
Okay. But ANY production of biodiesel that is profitable is BETTER than pumping petroleum and refining it with ALL its reel costs. Take for example the fact that algal oil can be produced domestically and provides JOBS to the alternative energy sector. And begin to factor in the ACTUAL energy consumed in defending, drilling, pumping, transporting and refining petroleum.
Fuel grown at home makes more security sense than foreign oil imports.
Posted by: Reel$$ | 31 August 2010 at 09:06 AM
An excellent argument Reel$$.
Posted by: HarveyD | 31 August 2010 at 09:10 AM
I second that HD. An argument can also be made, that energy independence, being intertwined with national security, saves lives. As much of a global free market capitalist as I am, I still support 100% energy independence for America through renewables.
Posted by: ejj | 31 August 2010 at 10:07 AM
Be careful Reel$$, not any production of biodiesel is better than pumping oil.For example biodiesel from soybean may be profitable but poor energy balance and deforestation implicated makes it a problem rather than a sustainable solution for everyday transport.
Strategical reasons are another thing.
Posted by: Account Deleted | 31 August 2010 at 11:12 AM
USA may be amongst the few large countries with enough diversified non-food feed stocks to produce large quantities of bio-fuels while producing more than enough food for its growing population. Secondly, most of us could reduce food eating be 50% from 4000 cal/day to 2000/day. That would reduce harmful obesity, reduce absenteeism, reduce health care cost and increase productivity. We should probably produce less food.
Posted by: HarveyD | 31 August 2010 at 02:58 PM
I have been saying for six or seven years that Algae is the way to go to repace fossil fuels. It can be produced in a decentralized method and the destributation system is already in place.
Forget about Hydrogen and Ethanol.
Cost and handling nix H and Ethanol reduces global food supplies.
Another reasonable alternative is Methanol produced from fast growing, non-food, crops. Again it would be relatively easy to decentralize and distribute.
Posted by: Lucas | 31 August 2010 at 05:56 PM
Pier you are correct. Food crops used as feedstock result in energy imbalance. Which makes it an accounting issue; because if we raise the cost of food and deforest woodland areas - those are the REEL costs in a gallon of biodiesel. IF such costs are accounted for - these projects will not be profitable. Reel world economics.
Posted by: Reel$$ | 31 August 2010 at 10:51 PM