Algae Ponds: the lovers and the haters

This week’s issue of C&EN includes some news from algae-based biofuels firm Sapphire Energy. The company is reporting its first harvests of algae biomass from a large, outdoor algae farm in New Mexico.

Sapphire’s outdoor raceway ponds in New Mexico. Source: Sapphire Energy

Sapphire has grown and gathered 21 million gallons of algae biomass totaling 81 tons. Eventually, the plan is to make a kind of crude oil from the algae. They grow the stuff in very large outdoor ponds. According to the press release, “the cultivation area consists of some of the largest algae ponds ever built with groupings of 1.1 acre and 2.2 acre ponds which are 1/8 of a mile long.”

You’d think that the promoters of algae for biofuels would be clinking glasses filled with spirulina-enhanced juice at the news. But you’d be wrong.

In fact, a trade group of algae firms calling itself the National Algae Association says the kind of ponds used by Sapphire – known as raceway ponds (you can see why looking at this image) – will not scale up commercially. Instead the NAA supports the development of photobioreactors (PBRs for short). Similarly, algae researcher Jonathan Trent, writing in a New Scientist magazine piece that also appears in Slate is arguing in favor of photobioreactors. Specifically, Trent says PBRs should be deployed offshore. I’ll quote from his article where he summarizes the raceway/PBR tradeoffs:

There remains the question of how and where to grow the algae. A few species are cultivated commercially on a small scale, in shallow channels called raceways or in enclosures called photobioreactors (PBRs). Raceways are relatively inexpensive, but need flat land, have lower yields than PBRs and problems with contamination and water loss from evaporation. PBRs have no problems with contamination or evaporation, but algae need light, and where there is light, there is heat: A sealed PBR will cook, rather than grow, algae. And mixing, circulating, and cleaning problems send costs sky high.

Trent doesn’t mention what industry analysts complain about the most. When it comes to algae, though PBRs might be the best bet, they require too much capital expenditure for the equipment.

Meanwhile, Solazyme, which started life as an algal fuels firm but now is manufacturing oils for use in skin cream and other high value applications, grows its algae in a third way – its algae live in bioreactors, but in the dark. They eat sugar and make oil. Is there a best way to commercialize algae for fuels and chemicals? Is there any way? It seems that it is still too early to tell.

Author: Melody Bomgardner

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3 Comments

  1. One has not to forget, that only a few algae species are able to be grown in Raceway Ponds. There definately is a need for further PBR development to get a hold on the whole potential of algae!

  2. The price of PBRs has decreased significantly and production in PBRs has increased significantly. As I see it, one problem with NOT using raceway ponds at this point is that the DoE would have to admit that it wasted a lot of time and money, that they were short-sighted and the programs were led by less than competent people. Another problem I see is that PBRs use a whole lot less land than ponds. The poor farmers would have to grow crops on all that land they want to use for ponds, and not get paid and subsidized by the USDA and the DoE to grow corn and soybeans that they want to use to make fuel (and cosmetics, thank you Solazyme) instead of feeding ourselves.

  3. PBR and open air are not even comparible. The former is a method for converting *electricity* to liquid fuels. The latter is a method for converting *sunlight* to liquid fuels. PRB should be compared to other methods of creating chemical fuels from electricity, such as water electrolysis followed by either direct us of the hydrogen or the hydrogen’s further conversion into hydrocarbons. Honestly, PRB seems ridiculous to me. Photosynthesis is very low yield and doesn’t seem like a good way to convert high-value electricity into somewhat higher valued liquid fuels. Gasoline is worth about ten times electricity on a Joule vs Joule basis. Photosynthesis is limited to around 25% efficiency at the molecular level and even champion plants rarely crack 8% for the total process. So even if you had no capital, consumable, or processing costs, you are already in the hole at today’s prices.