Some Random Notes of Algal Fuels
The first draft of my book chapter on jatropha and algae as fuel sources has been submitted. My posting frequency here will now go back to normal. Those book chapters are a lot of work, but I enjoy writing them because I always learn a lot as I am doing the research. Here are five issues that I covered in the chapter, with references in case you want to read up on some of the issues.
1. The present cost of algae production from open ponds is too high to make fuel production economically viable.
There are a number of commercial algae operations around the world today, and costs per ton are well known in the U.S. It costs at least $5,000 to produce 1 ton of algae. If you optimistically presume that there is 30% oil embedded in that ton, then that translates into around $50 per gallon of oil, before it has been extracted and converted to diesel. Therefore, commercial operations based on open ponds will have that problem to contend with (Benemann 2009).
2. Photobioreactors (PBRs) are too expensive.
The capital cost for photobioreactors is at least $150 per square meter, approximately ten times the cost of open pond systems (Abayomi et al. 2009). Optimistically, the best possible yield you are ever going to get from that square meter, based on the amount of sunlight that algae can convert into biomass, amounts to less than 2 gallons. The actual current best yields as reported in the literature are under 0.5 gallons per square meter. So the problem there becomes a capital cost of $150 to produce at best 2 gallons of fuel a year. And we haven’t even gotten into operating costs.
3. The energy inputs into the algae production process are very high.
There were numerous reports in the literature that cited the high energy inputs required to produce algae and convert it into fuel. At least one comprehensive life cycle assessment done by the University of Virginia concluded that algae yields less energy than it takes to produce it (Clarens et al. 2010). This LCA was cradle to gate, and did not consider the energy cost of converting the algal oil into fuel.
4. Some algae don’t need sunlight, and can produce oil in a fermentor.
The fermentation approach appears to hold some promise. Cited costs in the literature were roughly an order of magnitude lower than either the open pond or PBR approaches. The caveat here is that the algae must be fed a sugar source, but the ultimate goal is to produce that sugar from cellulose. This is the approach that Solazyme is taking, and I am not betting against their eventual success.
5. Don’t believe the cited per acre yields that some proponents claim.
The very high algal oil yields that you see some proponents suggest are all fictional. Nobody, anywhere, is making thousands of gallons of algal oil per acre. What people do is extrapolate best case lab results to thousands of acres, and then report those numbers – often as if they are actually achieving them. Or, they calculate best cases based on theoretical solar insolation. So it is best to treat those claims of high algal yields skeptically. As my friend John Benemann says, when you hear someone talk about yields like that, ask them how much oil they have for sale.
My conclusion is that with the possible exception of the fermentation approaches, the issues that caused NREL to abandon algae in the mid 1990’s are still pressing issues today. I see very little likelihood that companies basing their plans on either open pond systems or photobioreactors can be successful without heavy, perpetual doses of government funding.
Algae is still a lab project for the most part, and companies that have moved to commercialize it presently have little chance of economic viability. However, having said that, I think there are some niches in which it might eventually work, and I do favor spending research money in the hopes that in 10 or 15 years, commercialization is a realistic goal.
Abayomi, A., Tampier, M., Bibeau, E. (2009). Microalgae Technologies and Processes for Biofuels/Bioenergy Production in British Columbia. Retrieved May 2, 2010 from http://www.bcic.ca/images/stor…..report.pdf.
Benemann, J. (2009). Microalgae biofuels: a brief introduction. Retrieved April 24, 2010 from http://www.adelaide.edu.au/bio…..uction.pdf
Clarens, A., Resurreccion, E., White, M., Colosi, L. (2010). Environmental Life Cycle Comparison of Algae to Other Bioenergy Feedstocks, Environmental Science & Technology, 44 (5), 1813-1819
For anyone interested, below is the Table of Contents in the draft I just submitted:
The Potential of Algae and Jatropha as Biofuel Sources
3 Renewable Diesel
3.2 Green Diesel
4 Jatropha Curcas as a Source of Biofuel
4.1 Jatropha Description
4.3 Harvesting and Processing
4.4 Jatropha Oil
4.5 Jatropha Biofuel Feasibility Calculations
4.6 Conclusions on the Near Term Viability of Jatropha-Based Biofuel
5 Algae as a Source of Biofuel
5.1 Algae Description
5.2 Algal Oil
5.3 Algae Production Systems
5.4 Algae Life Cycle Assessment
5.5 Algal Biofuel Feasibility Calculations
5.6 Conclusions on the Near Term Viability of Algal Biofuel
7 Conversion Factors
7.1 Lower Heating Values