Last week, Frank Ciampa, posted Algal Biodiesel: Pros and Cons, his response to Could Algae be the New Corn?, written by Julia Verdi. This week, Eamon Keane, responds to Julia’s post, explaining why he does not feel that algae biofuels is a good alternative to oil.
by Eamon Keane
I thought this title was actually going to critically analyse algae. Instead there were no figures, just word based arguments. You will be aware of the study which came out in January which showed algae to have significantly higher emissions than diesel. Also, the non-solar energy invested in algae is the same as the energy contained in algae (EROI=1). Then there’s the small matter of cost, far north of $10/gallon. The DOE says they are at least 10 years away, and if you read their document there are so many issues involved, I don’t hold out much hope.
American presidents have been promising for decades to wean Americans off foreign oil. Obama is the latest, with $44m recently allocated to what’s widely regarded as the ideal solution – algae.
Algae aren’t new, they’ve been studied for over 80 years. In 1978 Carter launched the Aquatic Species Program to get oil from algae. It was defunded in 1996 by Clinton without any noticeable success.
Recently, a paper by the University of Virginia undertook what is essentially the first Lifecycle Analysis (LCA) of algae for biofuels. The paper, which I’ve read, is behind a $30 paywall but the supporting info (.pdf) with all the calculations is not. The results are not good. The study only accounts for the energy and emissions for the algae biomass before processing to get a liquid biofuel. I’ve adjusted the results assuming 50% lipids which reveals the following comparison:
Figure 2 shows the energy invested over the lifecycle versus the energy in the algae biomass:
Energy Return On Investment (EROI) is critical to understanding new energy sources. In the past oil required almost no energy expenditure to extract – you just pricked a hole about 15 feet deep and out it gushed.
Figure 3 shows the EROI for other energy sources:
If recoverable oil reserves are 2 billion barrels but it takes 1 billion barrels worth of oil energy to extract them, then you’ve actually only got 1 billion barrels of reserves.
So clearly algae aren’t the sort of ‘free energy’ from the sun as they might be portrayed. The energy inputs break down approximately as follows:
The study assumed the CO2 was a pure gas which accounts for the large energy input. The suggestion is of course that you would co-locate it with say a coal plant and feed the flue gas, however this results in an average drop of 50% in yield. You can quibble about the energy inputs if you like, but take, for example this quote from the DOE’s June 2009 Algae Biofuels Technology Roadmap (.pdf):
Nonetheless, this analysis shows that any harvesting/extraction scheme involving dry algae is energy prohibitive, requiring at least 60% of the energy content of algae. There is thus a need to develop strains of algae with much higher energy content than available today.
Furthermore take a look at the process flow diagram and all the times energy input is required:
This was for an open pond environment, the energy inputs for a photobioreactor would be much higher. In every report I’ve read, they’ve been dismissed as impractical and much more expensive than open pond. The former head of the Aquatic Species Program refers to them as bizarre contraptions.
So open ponds are the only show in town. The problem with them is that they’re open to the atmosphere and thus invasive species. Take this quote from an algae expert (.pdf):
Although large scale microalgal culture has now been undertaken for over 40 years, our experience is still limited to a few species, and even for these, our understanding of their ecology is still very incomplete.
Not exactly inspiring considering there are millions of algal species and viruses.
You can talk about using manure from farms or using wastewater to supply the nutrients. The problem with manure would be the energy needed to collect, transport and extract nutrients from it, and also the fact that most of it is already left on fields as natural fertilizer. Furthermore algae require the exact right ratio of nutrients for optimal growth, which may not be forthcoming from manure.
Using algae to clean wastewater of nutrients is actually a good idea, but it’s not going to yield commercial quantities of algae, and if you wanted to scale it up you’d still have to add lots of nutrients.
It is thus quite difficult to assign any confidence for the future of algae. Because of the harsh realities, you’ll never find a life cycle assessment in an algae biofuel press release. However, quelle surprise, the algae biofuels association disputes the findings and says it is using “outdated data”. Show us the new data, then.
© 2010, Eamon Keane. All rights reserved. Do not republish.