semi permeable plastic bags for algae harvestingNASA scientists from the Moffet Field laboratory in California have proposed an ingenious process to grow algal biofuels in the ocean enclosed within large floating bags made of a special semi-permeable clear plastic membrane. Growing algae in floating bags in the sea solves several major problems that are faced by current land based methods of algal biofuel production in an elegant low energy, low impact manner. This is the kind of out of the box thinking that is needed in order to grow the green economy.

In a recent update to our original post on the NASA plan to produce biofuel in floating bags filled with sewage NASA engineers and seasoned biofuel industry veterans have launched a new biofuels company called Algae Systems to produce Carbon-Negative Diesel and Jet Fuel NASA-developed technology, called OMEGA (Offshore Membrane Enclosures for Growing Algae) that is covered in our original post from last May.

NASA’s, Lisa Lockyer, Deputy Director of New Ventures and Communications for the Ames Research Center, has echoed Algae Systems’ determination and confidence by announcing the center’s support for the commercialization of the technology.

The Problems Facing Current Land Based Algal Biofuel Systems

Although algae live in water current research has been focused on land based systems for producing algal biofuels from these one celled work horses. The two land-based methods being researched today are manmade open ponds and closed bioreactors. Open ponds are shallow channels filled with freshwater or seawater, depending on the kind of algae that is grown. Closed bioreactors instead are closed systems. Both land based methods require often scarce land resources of course and also each present their own unique set of problems.

In open pond systems the water must be continuously re-circulated in order to achieve high yields and efficient production of algae. In fact, if not circulated a layer of algae – i.e. pond scum — tends to form on the water surface preventing most light and oxygen from reaching the water volumes below this surface mat of tightly packed algae mass.

In order to keep the algae suspended and the pond aerated paddle wheels need to continuously re-circulate the water mass. These manmade ponds also have the problem of water evaporation, which is a limiting factor in dry water poor areas. As water evaporates out of these shallow warm re-circulated artificial ponds a continuous supply of new freshwater (or new ocean water for salt water systems) is needed to replenish the water that has been lost to evaporation. The salinity of the water needs to be kept within operational parameters; if it gets too salty the algae in the pond will be killed.

Bioreactors, which are enclosed systems constructed using clear plastic or glass, have their own set of problems. While water evaporation is minimal because they are closed systems keeping the water from getting too hot or cold is a big problem for these types of installations.

Algal Has the Potential to Produce Large Quantities of Plant Derived Oil

“The reason why algae are so interesting is because some of them produce lots of oil,” said Jonathan Trent, the lead research scientist on the Spaceship Earth project at NASA Ames Research Center, Moffett Field, Calif. “In fact, most of the oil we are now getting out of the ground comes from algae that lived millions of years ago. Algae are still the best source of oil we know.”

Biodiesel is currently mainly produced from soy, canola, and palm trees. The biofuel yields of these crops ranges from around 500 liters per hectare per year (or 50 gallons per acre per year) for soy beans; to around three times that figure for canola and 6,000 liters per hectare per year (or 600 gallons of oil per acre per year) for oil palm.

By comparison some species of algae can produce as much as 20,000 liters per hectare per year (or 2,000 gallons of oil per acre per year) of biofuel. This is 40 times the yield of soy beans!

How NASA Proposes to Produce Fuel From Sewage Using Floating Bags

“The inspiration I had was to use offshore membrane enclosures to grow algae”, said Trent “We’re going to deploy a large plastic bag in the ocean, and fill it with sewage. The algae use sewage to grow, and in the process of growing they clean up the sewage.”

The concept is simple and elegant. Large floating plastic bags are filled with sewage and floated in open ocean water. The sewage filled bags are inoculated or seeded with the desired carefully selected strains of oil producing algae that will feed on the nutrients in the sewage, growing rich, fatty cells. The bag is made with a semi-permeable membrane material that allows fresh water to flow out into the ocean, while retaining the algae and nutrients and that is also gas permeable enabling carbon dioxide to be consumed and oxygen to be released. These special types of membranes are called “forward-osmosis membranes”, essentially they allow fresh water to run in one direction while preventing salt water intrusion from the surrounding sea water.

The continuous mechanical action of ocean swells will keep the water within the bag well mixed and promote the exchange of gases through the membrane’s surface. It will do this for free. The internal temperature of the floating bag bioreactors will be moderated by the thermal mass of the surrounding ocean water.

Think how much semi-treated or raw sewage is currently just dumped into the ocean. This process promises to turn this harmful polluting waste into valuable products in a way that uses the ocean itself to help promote its productivity. The bags are expected to last two years, and can be recycled afterwards.

© 2009 – 2010, Chris de Morsella. All rights reserved. Do not republish.

Line Break

Author: Chris de Morsella (146 Articles)

After a decade performing as a lead guitarist for rock bands, Chris de Morsella decided to return to the career his uncle mentored him in as a youth....Software Engineering. Since that time he has thrown himself into his work. He has designed a compound document publishing architecture for regulatory submissions capable of handling very large multi-document FDA regulatory drug approval submissions, for Liquent, a division of Thompson Publishing. At the Associated Press, Chris worked with senior editors at facilities around the world, to develop a solution for replacing existing editorial systems with an integrated international content management solution. He lead the design effort at Microsoft for a help system for mobile devices designed to provide contextual help for users. Chris also helped to develop the web assisted installer for LifeCam2.0, the software for Microsoft’s web cam and developed late breaking features for the product He also served with the Rhapsody client team to redesign and build a major new release of Real Networks Rhapsody client product. His most recent assignment has been Working with the Outlook Mobile Time Management team for the next release of Outlook Mobile for the SmartPhone. Chris' interests are in green building and architecture, smart grid, the cloud, geo-thermal energy, solar energy, smart growth, organic farming and permaculture. Follow Chris on Twitter.

  • Caro McClelland

    Thanks for this interesting article. I’m in the process of writing the Biofuels Industry Profile for my new book, Green Careers For Dummies, so it’s perfect timing for me to see this fascinating development.

    Always appreciate your in depth coverage of key topics in the green economy!

  • chris

    Thanks for your comment and I am glad that you found this post interesting and informative. From the research I have done on the subject algal biofuels seems like one of the more promising kinds of biofuel sources — if some of the cost barriers can be overcome. Which is precisely why I found this NASA study/proposal to be so interesting as well.

    The whole biofuel sector has been somewhat clouded by deserved blowback from the 1rst generation corn and soya derived biofuels. The energy return on energy invested or ERoEI for these food based biofuels is marginal even using the most optimistic accounting inputs and may actually use more petro based chemicals to make than the energy it produces. In addition of course it removes food from being available for human consumption in a world beset with hunger for all too many.

    I am looking forward to seeing your book when it gets published — many professionals and workers in the skilled trades are going to be needing help in order to make the transition into a green economy career. And right now there are very few resources to help people make the transition or to understand what the green economy means for them, their families and for their communities.

  • Tony Cobian

    Informative article, thanks. wondering if you have Mr. Trent contact info and will forward? I have a similar concept for open ocean algae fueling stations

  • GTG Student

    what about pollutants found in sewage? is it possible that these might leak into the ocean?

    • Chris de Morsella

      Thats a good point. Hopefully, someday the problem — and more importantly the cost — of toxic industrial, agro & household pollutants will be paid for by the parties that produce them and these costs will no longer be socialized as they currently are being. Naturally this is a huge and very complex issue that raises considerable passion and emotion, but never the less it remains painfully evident that our system socializes huge “external” costs onto the commons — i.e. you and me and everyone — and in so doing is able to squeeze out a tiny private profit.. very tiny when compared to the externalized costs that have been shed onto the commons.

      These classes of long lived industrial toxics such as PCBs, organo-chlorines, heavy metals etc. and increasingly — as America becomes a pill popping country — antibiotics and estrogenic pharmaceutical residues as well. So you definitely raise a valid concern. This is one of our world’s most serious and insidious problems, because it is a largely invisible globe spanning pollution problem. For example, the top of the food chain in our oceans is becoming poisoned away by bio-accumulations of these toxics in their bodies and is increasingly threatened in many cases with extinction.

      The sewage input into this system would need to contains very little of these classes of toxics. This is a goal we need to achieve in any case. Only sewage — or other stream such as agro-waste for example — that was somehow certified perhaps, would be pumped into these suspended floating reactor bags.

      Better yet of course is to find ways to reduce sewage streams in the first place and also to find ways to filter and otherwise process (in natural-mimetic ways) waste streams in order to bio-remediate them as close to the source as is feasible.

      As you can tell I am a big supporter of the idea of distributed decentralized systems. I believe they better fit the natural world we live in and need to better learn how to live in.

    • disqus_mP2DAssLsF

      you think they haven’t many times before and still don’t?