ExxonMobil and Synthetic Genomics progressing in their algal biofuels partnership; preliminary results from lifecycle analysis
ExxonMobil is progressing in its partnership with Synthetic Genomics (SGI) (earlier post) to explore algae biofuels. At the 2011 Algae Biomass Summit in Minneapolis, Dr. Michael Matturro, Corporate Programs Laboratory Director for ExxonMobil, provided a brief overview of the scope of the work and described some preliminary results from a comprehensive lifecycle analysis of different algal biofuel production pathways being done by the two partners along with MIT.
Dr. Matturro said that ExxonMobil and SGI are working on developing solutions to the challenges of large-scale production and commercialization of biofuels derived from algal oils, including identifying and developing algal strains that achieve high bio-oil yields at lower cost; determining the best product systems for growing strains; selecting an optimum process strategy for bio-oil recovery; establishing a bio-oil upgrading process compatible with existing refinery infrastructures; and developing an integrated system required for full-scale economic production of biofuel.
Our focus [with SGI] is to research and develop next-generation biofuels based on photosynthetic algae. We think this approach complements the many sorts of technology we are trying to pursue in conventional oil and gas. The challenges are rather significant and require an investment of time, money, and scientific expertise. We think it’s an effort worth making.—Michael Matturro
The lifecycle analysis work being done with MIT includes an assessment of carbon and freshwater footprints, direct land use and facility siting. The analysis is based on publicly available data and the engineering judgement of the partners, Matturro said.
The product assessed is hydroprocessed diesel—i.e., renewable drop-in diesel produced by the hydrotreating of algal oil. The current “pond-to-wheels” analysis is based on the use of open pond systems (raceways with paddle wheels) for algae production, and models several oil recovery options—dry extraction, wet extraction and secretion cases—to which the researchers refer as technology sets.
Their results indicate that a nominal dry extraction pathway (i.e., reflecting some improvement in technology above today’s commercial systems) yields significantly higher net greenhouse gas emissions (i.e., emissions minus credits for carbon uptake in the algae and the use of biogas electricity) than the production of conventional petroleum-based diesel; about 50% of the GHG burden in growth, harvesting and drying is the drying. Shifting to nominal wet extraction and secretion methods, they found that both yielded almost a 50% reduction in GHG compared to petroleum diesel.
However, Matturro noted, the team has found that pond-to-wheel greenhouse gas emissions for algal biofuels can span a broad range depending upon the technology choice, pointing to results that showed even the dry extraction pathway can beat the petroleum diesel baseline with almost a 50% reduction in a stretch case (e.g., with the most optimistic technology assumptions for high productivity).
The point of this is to bring out the fact that you need to look at the range of sensitivities of all these process schemes and understand where the levers are.—Michael Matturro
The team has also run freshwater consumption cases, and compared the results to freshwater consumption by petroleum, corn ethanol and soy biodiesel cases. Freshwater consumption scenarios result in much higher water consumption for algal diesel than required by petroleum, and below consumption of irrigated water for ethanol and biodiesel, although again significantly above rain-fed processes for those fuels.
However, the use of brackish water brings freshwater consumption in nominal and stretch cases for algae down to approximately the level of consumption by petroleum and rain-fed soy diesel, and below rain-fed corn ethanol.
Greenhouse gas emissions and on site freshwater consumption for algal biofuels can vary considerably; it depends on the technology set. The near-term technology set for algal diesel can have higher lifecycle GHG than fossil diesel. We can bring that down. On site freshwater consumption for algae in open ponds can be comparable to petroleum fuels. The next steps will involve the analysis of closed systems.—Michael Matturro