Abstract
Introduction
Six years ago in December 2008, the US Department of Energy (DOE) sponsored a workshop to stimulate discussion on the development of a national algal biofuels industry. DOE's Bioenergy Technologies Office (BETO or “the Office”) organized the workshop, which gathered 200 stakeholders to discuss and identify the critical challenges hindering the development of a domestic, commercial-scale algal biofuels industry. One of the workshop's major objectives was to gather the information necessary to produce an algal biofuels technology roadmap that both assessed the current state of technology and provided direction for the Office to initiate a research and development (R&D) effort.
The workshop solidified the opinion of attendees that algae biofuels offer great promise in contributing to the nation's need for renewable fuels and could contribute to meeting the Office's goals of producing cost-competitive advanced biofuels. As a result of the planning initiated by the workshop, DOE developed a long-term applied R&D strategy to increase the yields and lower the costs of algal biofuels. In 2010, DOE selected four multidisciplinary research consortia to accelerate technology development to meet these objectives: the Sustainable Algal Biofuels Consortium, the Consortium for Algal Biofuels Commercialization, the Cornell Consortium, and the National Alliance for Advanced Biofuels and Bioproducts (NAABB). This investment established a new generation of algae researchers and catalyzed progress across the entire algal biofuels supply chain.
To highlight the progress made across the industry in the five years since DOE published the National Algal Biofuels Roadmap, BETO hosted two additional strategy workshops in November 2013 and March 2014. 1 Coupled with a comprehensive program project review held in the spring of 2013, BETO was able to take a fresh look at the potential of algal biofuels and consider its strategy for the next 5–10 years. Proceedings from the peer review and workshops are accessible on BETO's website. 2,3
Algal Biofuels
The Potential
There is no lack of agreement that algae have the potential to produce a wide array of both energy- and non-energy-related products. Algal lipids are useful for the production of biodiesel, bioethanol, renewable diesel and biogasoline, biohydrogen, and bio-jet fuels, and they also serve as a feedstock for electricity production. The protein component of algae is already being used as an important food, and other components have found uses in the health and nutraceutical industry in the production of drugs, cosmetics, and skin care products. Algae are also used to supplement feed supplies for livestock as well as aquaculture. Algae's high productivity and ability to grow where traditional crops do not do well make it seem like the perfect industrial feedstock.
The Challenge
DOE has established a strategic goal: “to develop algae production and logistics technologies that, if scaled-up and deployed, could support the production of 5 billion gallons per year of sustainable, reliable, and affordable algae-based advanced biofuels by 2030.” While algae are seemingly the perfect feedstock for bioenergy production, techno-economic analyses published by the National Renewable Energy Laboratory and NAABB in 2012 show that the current state of technology would produce fuel at about $18 per gallon gasoline equivalent. 4 The analyses concluded that in order for commercial fuel production to be a viable option, a 5-fold increase in combined productivity and yield would be needed over the assumed 13 grams per square meter per day productivity and 25% oil yield, while significantly reducing capital costs.
A significant amount of R&D must be completed before algal biofuels will be cost competitive with petroleum fuels. One of the biggest challenges is developing economical and sustainable technologies to produce, harvest, extract, and convert the useful components into advanced biofuels. BETO conducts research on relevant technologies to scale-up the production of algal biofuels in accordance with its Multi-Year Program Plan. 5
BETO's R&D focuses on overcoming technical barriers to the cost-effective production of algal biomass and intermediates, as well as on developing logistics systems for producing commercially viable algae-based biofuels and bioproducts. Algal biomass includes micro- and macro-algae, as well as cyanobacteria. These efforts are broadly classified into algal biomass production, which includes the development of algae strains and algae cultivation systems (eg, open-pond and closed photobioreactor systems) able to cost-effectively produce commercial levels of algal biofuels and bioproducts cost effectively.
DOE-Funded Progress
NAABB, the largest of DOE's four algae consortia, has completed its research and issued a final report. The diverse successes of this 39-member consortium range from basic advances in algal biology, such as the genetic sequencing of production strains, to the development of hydrothermal liquefaction—a breakthrough conversion pathway for algae. 6 New biological and engineering approaches are enabling productive use of an increasing share of algal biomass—boosting process efficiency. In addition to using the stored fats (lipids) in microalgae, researchers are exploring ways to use secreted compounds (without destroying the cells) or the whole algae biomass of some strains.
Researchers at the Scripps Institute of Oceanography (SIO) made a significant breakthrough in the metabolic engineering of algae to improve the yield of lipids (the energy-storing fat molecules that can be used in biofuel production). Typically, algae only accumulate lots of lipids when they are starved for nutrients, but the drawback to starvation is that it limits organism growth. The SIO research team genetically engineered a disruption in the synthesis of the enzymes that break down the storage lipids that are produced during normal growth, allowing for a lot of lipid accumulation without starving the algae. The resulting algae grow quickly and accumulate lipid at the same time. The high lipid yields that result from utilizing this method can potentially improve the economics of algal biofuel production. 7
DOE successfully established a series of regional algal testbeds in 2013. The vision for this effort was to establish a network of algal test sites that would accelerate the creation and dissemination of knowledge to the algal research community. Stakeholders now have access to high-quality facilities, including outdoor cultivation, downstream processing, and laboratory facilities. Innovations in large-scale production of algae can more easily be tested without the need for expensive capital on a per project basis. The facilities are positioned in four different geographic locations to expand the breadth of understanding of algae in different climates.
DOE continued its strategic partnering approach and is demonstrating promising cultivation techniques in open ponds, photobioreactors, and hybrid systems. For example, BETO provides cost-shared funding to the following partners for the demonstration of various algae production and conversion technologies: Sapphire Energy Inc. (demonstration scale), Algenol Biofuels Inc. (pilot scale), Solazyme Inc. (pilot scale), and BioProcess Algae (pilot scale). These DOE partnerships are leveraging significant investment to further their efforts. For instance, Sapphire Energy—one of the world's leaders in algae-based green crude oil production—entered into contract agreements with two major oil and gas companies: Phillips 66 and Tesoro. Phillips 66, an integrated energy manufacturing and logistics company, partnered with Sapphire to test and upgrade the company's “Green Crude” into on-spec diesel to allow it to be dropped into any existing diesel fuel tank and delivered using current infrastructure.
Tesoro, an independent refiner and marketer of petroleum products, agreed to a commercial purchase agreement with Sapphire. Additionally, Cellana, a leading developer of algae-based bioproducts and a member of the DOE-funded Cornell Consortium, secured a contingent offtake agreement with Neste Oil, the world's largest producer of renewable diesel, in 2013. More information about these and other successes are available on the BETO website. 8
Targeted Areas for Improvement
Despite these successes, much remains to be done if DOE is to accomplish its goals. Attendees of the recent Algae Biofuels Strategy Workshop continue to see a need for a strong effort in understanding fundamentals and enabling technologies, such as models, genetic toolkits, databases, standards, and protocols that will support researchers as they continue to work to overcome barriers. The Algae Review Panel at the 2013 Program Peer Review pointed out that progress toward productive, high lipid algae species has been slow and that the capital cost of cultivation systems remains high.
To address this, BETO continues to examine ways to reduce or eliminate the constraints of balancing lipid production with the overall growth rate of the algae. Combined with consistent, quantitative metrics for evaluating algal biofuel production pathways, BETO identified an additional design pathway deemed capable of producing an algae-based biofuel that could sell for less than $5 per gallon (gasoline equivalent) by 2022 on the way to the overall goal of $3 per gallon in 2030. BETO has increased efforts to develop whole algae hydrothermal liquefaction (HTL), as well as the more traditional algal lipid upgrading pathway.
Another area of increased emphasis geared toward reducing overall production costs is the development of algae cultures that produce valuable bioproducts alongside fuels to increase the overall value of the biomass. Co-products that can enable the economics of the biorefinery could include animal and fish feed, pharmaceuticals and food supplements, as well as eventually providing substitutes for petroleum-based chemicals that could be used as fibers, plastics, and in other chemical markets. DOE recently issued a funding opportunity announcement entitled “Target Algal Biofuels and Bioproducts.” This effort will support work at bench and process development scales to develop valuable co-products, crop protection, and carbon dioxide (CO2) utilization strategies. This effort to support biofuels development will be looking to enhance the economics of algal-based biorefineries by diversifying the products and adding necessary value to the biomass, reducing the risk of production of fuels. In addition, the effort addresses comments provided by the strategy workshop participants to increase investigation of CO2 resource availability, transport, cost, delivery, and utilization.
Conclusions
Although it has been 5 years since publication of the National Algae Biofuels Roadmap, it remains a commonly held view that algal biofuels offer great promise in contributing to the nation's energy needs, representing a significant opportunity to impact the US transportation fuels supplies. Despite their potential and the successful efforts of a wide array of researchers and industrial entities, the state of technology for producing algal biofuels remains immature compared to other potential biofuels, such as cellulosic ethanol, which has seen several production-scale facilities complete construction in 2014. A considerable amount of research, development, and demonstration is still needed to achieve affordable, scalable, and sustainable algal-based biofuels. DOE is continuing to work toward the goal of reducing the cost of algal biofuels to $3 per gallon gasoline equivalent despite an ever-changing energy landscape. Slow and steady advances, continued stakeholder engagement, and review and validation of ongoing efforts will pay off to ensure that options for renewable energy will be available when needed and will provide consumers with choices.