The importance of strain selection using batch cultures: development of a robust methodology to estimate large-scale algae biomass and lipid productivities Alex Holland1,3, Joe Dragavon2, David Sigee3 1Chemical Engineering, 2Chemistry, University of Washington, Seattle, USA 3Faculty of Life Sciences, Manchester, UK
Applied and Environmental Microbiology Gordon Research Conference 2005, CT, poster presentation
Metabolic Engineering V 2004, CA, poster presentation
Metabolic Engineering IV 2002, Italy, poster presentation
During this past academic year, the IGERT Multinational Collaborations on Challenges to the Environment fellowship has provided me with the resources to further investigate whether our society has the technological means to achieve sustainable development while reducing environmental stress. I would like to start by emphasizing the fact that energy efficiency alone will not prevent greenhouse gas accumulation; severance from the use of fossil and nuclear resources as energy sources, for consumer goods and use in infrastructure is essential. While I would not render justice to the latter, I hope to show that satisfying the first two does not require any major scientific breakthrough.
I am defining sustainable development as ‘the integration of the human activity into the natural carbon cycle, where all the chemical intermediates and products are bio-available, where no fossil resource is utilized (coal, oil, natural gas), and current forest ecosystems are preserved’. My presentation: “Global Sustainability: The Role of Emerging Technologies” points to a variety of sustainable technological alternatives, whose potential and significance should be assessed at three different levels:
In addition, Life Cycle Analysis is a powerful tool to assess current research potential for significant large-scale environmental impact. Furthermore, funding agencies could utilize this tool in order to best allocate their funds.
It is a common public perception that technological choices should be left to discussion among ‘experts’, and that funding agencies tend to fund the most promising areas of research across all disciplines. Yet, the reality is that each ‘expert’ knows best about their own area and will expectedly advocate for it. Thus, each scientist is, by definition, partial to their own research. In order to prevent this, the public must be educated about the basic science behind each discipline to formulate an overarching set of criteria, in order to determine the most viable routes toward sustainable development.
The understanding that carbon neutrality is necessary to achieve sustainable development is increasingly being accepted by the public. When I joined the Sierra Club Energy Committee five years ago, I had a heated discussion with one of the members who claimed that hydrogen should be preferred as a transportation fuel over methanol as hydrogen does not emit carbon dioxide. But, the more relevant question to answer was whether the methanol or the hydrogen was produced from a fossil resource, since the use of the fossil resource would undermine carbon neutrality. In the same manner, fuel cells are a more efficient means to produce power compared to combustion engines. However, the energy sources for these fuel cells are still typically derived from fossil resources which, again, do not support carbon neutrality. As our society engages in its sustainable transition, it is crucial for the public to understand the bigger picture and build a consensus about the goals for scientists and engineers to reach.
Rough assessment of various technologies can easily be achieved with back of the envelope calculations which can be discussed across a broad range of disciplines. In my presentation, I carried out such rough preliminary assessment with algae biofuel production as an example.
The individual contribution of each technology can be better assessed once integrated, which is crucial to the process’ overall success. With this in mind, and as a tool for learning, such analysis can be carried out by teams of chemical or mechanical engineering undergraduate students in the scope of an independent senior design project. An integrated process combining algae lipid synthesis to produce biofuel, anaerobic digestion to produce methane, and methane fuel cells to produce electricity, will be examined during the Chem E 497A course during the 2006-07 academic year. This will fulfill my IGERT fellowship pedagogical internship.
IGERT project overview
Rhonda Schmidt (Forest Resources), Nam Nguyen (Materials Science Engineering) and I (Chemical Engineering) worked as a team to look at ‘Tri-Glyceride production from algae grown on dairy anaerobic digester effluent’ during the 2005-06 fellowship year. Anaerobic biodigesters (ADs) are able to process cow manure and stable scrapings to produce methane which can, in turn, power a generator. The electricity that is generated can be used for the farm or sold back to the local utility. The byproducts of the process are carbon dioxide, dry fiber and nutrient-rich liquid effluent. The dry fiber is used as animal bedding or nursery material, but there is currently no practical use for the carbon dioxide and liquid effluent. The carbon dioxide is released into the atmosphere and the wet effluent is normally lagooned and seasonally applied to fields.
ADs are environmentally-friendly since they produce and concentrate methane for fuel that would normally be released into the atmosphere if the manure was lagooned. Methane is approximately 25 times more potent as a greenhouse gas than carbon dioxide. Dairy farms are a significant source of atmospheric methane. Unfortunately, anaerobic biodigesters are not very economically viable in the Pacific Northwest since this region has some of the lowest electric rates in the country due to the abundance of hydroelectric power. Since the cost of electricity is so low, the electricity produced by the burning of methane from the AD process is also of relatively low value and it can take over 10 years to pay back the initial cost of the digester.
As a group, we decided to look at a way to make the AD process more economically viable and to utilize the byproducts of the AD process. We determined that using coupled AD/algal bioreactor system could possibly meet our objectives. Algae can produce large amounts of Triacylglycerols (TAGs), on the order of 20-30% of their cell weight. TAGs constitute the oil-precursor of biodiesel. Algae produce what is considered high-quality TAGs for biodiesel and they are resistant to gelling and oxidation. To grow the algae, we are proposing to use AD effluent and carbon dioxide from the AD process as nutrient sources. TAG from the algae will be extracted enzymatically, and used for biodiesel production on the farm.
Project timeline and meetings
I met Paul Davis, a farmer interested in commercializing his small-scale biodiesel production unit, and tried to help him take advantage of University resources to do so. In the process, I found out about algae production of bio-oil on the University of New-Hampshire website: http://www.unh.edu/p2/biodiesel/article_alge.html
November and December, 2005:
- University of Washington Engineering Open House 2002, 2003, 2004, performed the demo on luminescent bacteria ‘the Glow of Nature’
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