Advanced biofuels and algae research: targeting the technical capability to produce 10,000 barrels per day by 2025

In 2012, researchers from MIT, ExxonMobil and Viridos (formerly Synthetic Genomics, Inc.) published an assessment of algal biofuels in the peer-reviewed journal Environmental Science and Technology, which concluded that if key research hurdles are overcome, algal biofuels will have about 50 percent lower life cycle greenhouse gas emissions than petroleum-derived fuel. In contrast, there is a robust debate in the academic research community regarding the carbon footprint of first generation biofuels, which the EPA defines as those generated from edible crops (such as corn). Many peer-reviewed papers in the scientific literature suggest that the direct life cycle GHG emissions are lower than fossil fuels but that indirect consequences of first generation biofuel development, including changes in forest and agricultural land use change, may result in higher total GHG emissions than petroleum-derived fuels.

For these reasons, ExxonMobil is pursuing research into second generation biofuels to determine how they may best fit into our energy future. Second generation biofuels are defined as those produced from non-edible crops, crop residues or biologically generated gas and therefore do not take away from the total food or fresh water supply. Examples include algae, corn stover, switchgrass or methane emitted from microbial activity in landfills.

Biofuels research portfolio

We are funding a broad portfolio of biofuels research programs, including our ongoing efforts on algae as well as programs on converting alternative, non-food based biomass feedstocks, i.e. cellulosic biomass, to advanced biofuels. We believe our work with algae offers some of the greatest promise for next-generation biofuels, which is why ExxonMobil has committed hundreds of millions of dollars to algae research. We are working with leading researchers and have designed our portfolio to progress the science that we feel will be needed to deliver advanced biofuels with environmental benefits.

Our advanced biofuels research portfolio includes joint research collaborations focused on algae-based biofuels with Viridos, Colorado School of Mines and Michigan State. We are also exploring a variety of biomass conversion processes that could be used with non-food based feedstocks such as whole cellulosic biomass, algae feedstocks and cellulose-derived sugars. These programs are being carried out currently with Renewable Energy Group (REG) and the University of Wisconsin.

Algae for biofuels production

Benefits of using algae

Algae represents a significant improvement over alternate biofuel sources for several reasons:

• Unlike making ethanol and biodiesel, producing algae does not compete with sources of food, rendering the food-vs.-fuel quandary a moot point.
• Because algae can be produced in brackish water, including seawater, its production will not strain freshwater resources the way ethanol does.
• Algae consume CO₂, and on a life-cycle basis have a much lower emissions profile than corn ethanol given the energy used to make fertilizer, distill the ethanol, and to farm and transport the latter.
• Algae can yield more biofuel per acre than plant-based biofuels – currently about 1,500 gallons of fuel per acre, per year. That’s almost five times more fuel per acre than from sugar cane or corn.

We also know that algae can be used to manufacture biofuels similar in composition to today’s transportation fuels.

How algae grow

Algae can provide a diverse and highly desirable non-food source of the important renewable molecules that can be used to produce second generation biofuels. Some strains of algae can be optimized to produce bio-diesel precursors. Other algae strains can be optimized as a source of fermentable sugars, with compositions similar to those derived from corn kernels that are used to manufacture first generation biofuels like ethanol.

Basic algae biology research with Viridos

Today, ExxonMobil and Viridos are carrying out a basic research program to develop advanced biofuels from algae. This joint effort is working towards the technical ability to produce 10,000 barrels of algae biofuels a day by 2025. Our objective is to develop advanced algae biofuels options and identify the best pathways to make these groundbreaking technologies available to consumers. The program builds off of the many insights we have obtained and the progress we have made since we announced our initial alliance with Viridos in 2009.

Using advanced cell engineering technologies at Viridos, the ExxonMobil-Viridos research team most recently modified an algae strain to enhance the algae’s oil content from 20 percent to more than 40 percent. View the results of the research in the peer-reviewed journal Nature Biotechnology. 

Researchers at Viridos' laboratory in La Jolla discovered a new process for increasing oil production by identifying a genetic switch that could be fine-tuned to regulate the conversion of carbon to oil in the algae species, Nannochloropsis gaditana. The team established a proof-of-concept approach that resulted in the algae doubling its lipid fraction of cellular carbon compared to the parent – while sustaining growth.

“This key milestone in our advanced biofuels program confirms our belief that algae can be incredibly productive as a renewable energy source with a corresponding positive contribution to our environment,” said Vijay Swarup, vice president for research and development at ExxonMobil Research and Engineering Company. “Our work with Viridos continues to be an important part of our broader research into lower-emission technologies to reduce the risk of climate change.”

Algae has been regarded as a potential sustainable fuel option, but researchers have been hindered for the past decade in developing a strain that is high in oil content and grows quickly – two critical characteristics for scalable and cost-efficient oil production. Slower growth has been an adverse effect of previous attempts to increase algae oil production volume. 

A key objective of the ExxonMobil-Viridos collaboration has been to increase the lipid content of algae while decreasing the starch and protein components without inhibiting the algae’s growth. Limiting availability of nutrients, such as nitrogen, is one way to increase oil production in algae, but it can also dramatically inhibit or even stop photosynthesis, stunting algae growth and ultimately the volume of oil produced.

The ability to sustain growth while increasing oil content is an important advance. Algae has other advantages over traditional biofuels because it can grow in salt water and thrive in harsh environmental conditions, therefore limiting stress on food and fresh water supplies.

Oil from algae can also potentially be processed in conventional refineries, producing fuels no different from convenient, energy-dense diesel. Oil produced from algae also holds promise as a potential feedstock for chemical manufacturing.

Since 2009, ExxonMobil and Viridos have been partners in researching and developing oil from algae to be used as a renewable, lower-emission alternative to traditional transportation fuels. Swarup said that while the breakthrough is an important step, the technology is still years from reaching the commercial market.

The research challenge

We face some significant technical hurdles before biofuels production from algae will be possible at a significant commercial scale. To overcome these challenges, we are working to answer some basic questions such as:

• Why do algae utilize a relatively small amount of available light energy?
• What tools can be used to improve light utilization efficiency of algae and to improve production characteristics?
• How do you develop an organism that will produce significantly more bio oil?

The central challenge is that algae naturally harvest significantly more light than they can effectively convert to biofuels. Only a fixed amount of light hits the surface of a pond, and our goal is for the algae to use this light as efficiently as possible. The amount of wasted sunlight varies greatly depending on the algae species and growth conditions but can be as high as 80 percent or more. ExxonMobil and Viridos are conducting fundamental research to decrease the amount of wasted sunlight and increase biomass productivity by improving the photosynthetic efficiency of individual algae cells. To achieve this objective, the Viridos team is working to engineer algae cells that will absorb only the amount of light that they can effectively use.

Algae biofuels research and development is a long-term endeavor. We have learned a lot since ExxonMobil and Viridos began working together, and we continue to build the biology tools, capabilities and understandings that are necessary to overcome the technical hurdles.

The challenge of scale

According to Swarup, “We know certain types of algae produce bio-oils. The challenge is to find and develop algae that can produce bio-oils at scale on a cost-efficient basis.”

It would require a significant amount of algae to produce enough fuel to satisfy even a small portion of U.S. road transportation fuel demand. Population and economies will continue to expand along with energy demand and CO₂ emissions. At ExxonMobil, we recognize that an integrated set of solutions will be required to increase efficiency, expand supply and mitigate emissions. Technology breakthroughs will be critical and algae-based biofuels could contribute to this set of solutions.

The ultimate goal is to have algae bio-oils processed in our refineries to supplement supplies of conventional gasoline, diesel, aviation fuels, and marine fuels

What's next in advanced biofuel research? 

ExxonMobil is engaged in a wide range of research on advanced biofuels, partnering with universities, government laboratories and other companies. Global demand for transportation-related energy is projected to increase by about 25 percent through 2040, and accelerating the reduction in emissions from the transportation sector will play a critical role in reducing global greenhouse gas emissions.

ExxonMobil is also actively researching other emission-reducing technologies, including carbon capture and sequestration. In 2016, ExxonMobil announced its partnership with Connecticut-based FuelCell Energy, Inc. to advance the use of carbonate fuel cells to economically capture carbon emissions from power plants while generating hydrogen and additional electricity. Since 2000, ExxonMobil has spent about $8 billion to develop and deploy lower-emission energy solutions across its operations.

Pursuing this path involves considerable investment of time, money and scientific expertise in order to address the significant challenges associated with the development of economic, large-scale advanced biofuels. Further, predictions on success are difficult and depend directly on the pace of technological innovation. It could potentially take decades or more for advanced biofuels to reach a scale that would significantly benefit the transportation fuels sector.

We continue to evaluate our best options for continued algae biology research as part of our broader portfolio of biofuels research and development programs beyond algae.

Cellulosic research with REG

ExxonMobil has signed an agreement with Renewable Energy Group (REG) to study the production of biodiesel by fermenting renewable cellulosic sugars from sources such as agricultural waste. REG has developed a patented technology that uses microbes to convert sugars to biodiesel in a one-step fermentation process similar to ethanol manufacturing. The ExxonMobil and REG Life Sciences research will focus on using sugars from non-food sources. 

REG has a long history of innovation in the production of advanced biofuels from lower carbon, waste feedstocks. Through the research, the two companies will be addressing the challenge of how to ferment real-world renewable cellulosic sugars, which contain multiple types of sugars, including glucose and xylose, but also impurities that can inhibit fermentation. 

Our first challenge is to determine technical feasibility and potential environmental benefits during the initial research. If the results are positive, we can then take the next step and explore the potential to expand our efforts and explore scalability.