Jonathan Trent [ Waste Management 14:38 ] Some years ago, I set out to try to understand if there was a possibility to develop biofuels on a scale that would actually compete with fossil fuels but not compete with agriculture for water, fertilizer or land.
So here’s what I came up with. Imagine that we build an enclosure where we put it just underwater, and we fill it with wastewater and some form of microalgae that produces oil, and we make it out of some kind of flexible material that moves with waves underwater, and the system that we’re going to build, of course, will use solar energy to grow the algae , and they use CO2, which is good, and they produce oxygen as they grow. The algae that grow are in a container that distributes the heat to the surrounding water, and you can harvest them and make biofuels and cosmetics and fertilizer and animal feed, and of course you’d have to make a large area of this, so you’d have to worry about other stakeholders like fishermen and ships and such things, but hey, we’re talking about biofuels, and we know the importance of potentially getting an alternative liquid fuel.
Why are we talking about microalgae? Here you see a graph showing you the different types of crops that are being considered for making biofuels, so you can see some things like soybean, which makes 50 gallons per acre per year, or sunflower or canola or jatropha or palm, and that tall graph there shows what microalgae can contribute. That is to say, microalgae contributes between 2,000 and 5,000 gallons per acre per year, compared to the 50 gallons per acre per year from soy .
So what are microalgae? Microalgae are micro — that is, they’re extremely small, as you can see here a picture of those single-celled organisms compared to a human hair. Those small organisms have been around for millions of years and there’s thousands of different species of microalgae in the world, some of which are the fastest-growing plants on the planet, and produce, as I just showed you, lots and lots of oil.
Now, why do we want to do this offshore? Well, the reason we’re doing this offshore is because if you look at our coastal cities, there isn’t a choice, because we’re going to use waste water, as I suggested, and if you look at where most of the waste water treatment plants are , they’re embedded in the cities . This is the city of San Francisco, which has 900 miles of sewer pipes under the city already, and it releases its waste water offshore. So different cities around the world treat their waste water differently. Some cities process it. Some cities just release the water. But in all cases, the water that’s released is perfectly adequate for growing microalgae. So let’s envision what the system might look like. We call it OMEGA, which is an acronym for Offshore Membrane Enclosures for Growing Algae. At NASA, you have to have good acronyms .
So how does it work? I sort of showed you how it works already. We put waste water and some source of CO2 into our floating structure, and the waste water provides nutrients for the algae to grow, and they sequester CO2 that would otherwise go off into the atmosphere as a greenhouse gas. They of course use solar energy to grow , and the wave energy on the surface provides energy for mixing the algae, and the temperature is controlled by the surrounding water temperature . The algae that grow produce oxygen, as I’ve mentioned, and they also produce biofuels and fertilizer and food and other bi-algal products of interest.
And the system is contained. What do I mean by that? It’s modular. Let’s say something happens that’s totally unexpected to one of the modules. It leaks. It’s struck by lightning. The waste water that leaks out is water that already now goes into that coastal environment , and the algae that leak out are biodegradable, and because they’re living in waste water, they’re fresh water algae , which means they can’t live in salt water, so they die. The plastic we’ll build it out of is some kind of well-known plastic that we have good experience with, and we’ll rebuild our modules to be able to reuse them again.
So we may be able to go beyond that when thinking about this system that I’m showing you, and that is to say we need to think in terms of the water, the fresh water, which is also going to be an issue in the future, and we’re working on methods now for recovering the waste water.
The other thing to consider is the structure itself. It provides a surface for things in the ocean, and this surface, which is covered by seaweeds and other organisms in the ocean, will become enhanced marine habitat so it increases biodiversity. And finally, because it’s an offshore structure, we can think in terms of how it might contribute to an aquaculture activity offshore.
So you’re probably thinking, “Gee, this sounds like a good idea. What can we do to try to see if it’s real?” Well, I set up laboratories in Santa Cruz at the California Fish and Game facility, and that facility allowed us to have big seawater tanks to test some of these ideas. We also set up experiments in San Francisco at one of the three waste water treatment plants, again a facility to test ideas. And finally, we wanted to see where we could look at what the impact of this structure would be in the marine environment, and we set up a field site at a place called Moss Landing Marine Lab in Monterey Bay, where we worked in a harbor to see what impact this would have on marine organisms.
The laboratory that we set up in Santa Cruz was our skunkworks. It was a place where we were growing algae and welding plastic and building tools and making a lot of mistakes, or, as Edison said, we were finding the 10,000 ways that the system wouldn’t work. Now, we grew algae in waste water, and we built tools that allowed us to get into the lives of algae so that we could monitor the way they grow, what makes them happy, how do we make sure that we’re going to have a culture that will survive and thrive. So the most important feature that we needed to develop were these so-called photobioreactors, or PBRs . These were the structures that would be floating at the surface made out of some inexpensive plastic material that’ll allow the algae to grow, and we had built lots and lots of designs, most of which were horrible failures, and when we finally got to a design that worked, at about 30 gallons, we scaled it up to 450 gallons in San Francisco.
So let me show you how the system works. We basically take waste water with algae of our choice in it, and we circulate it through this floating structure, this tubular, flexible plastic structure, and it circulates through this thing, and there’s sunlight of course, it’s at the surface, and the algae grow on the nutrients.
But this is a bit like putting your head in a plastic bag. The algae are not going to suffocate because of CO2, as we would. They suffocate because they produce oxygen, and they don’t really suffocate, but the oxygen that they produce is problematic, and they use up all the CO2. So the next thing we had to figure out was how we could remove the oxygen, which we did by building this column which circulated some of the water, and put back CO2, which we did by bubbling the system before we recirculated the water. And what you see here is the prototype, which was the first attempt at building this type of column. The larger column that we then installed in San Francisco in the installed system.
So the column actually had another very nice feature, and that is the algae settle in the column, and this allowed us to accumulate the algal biomass in a context where we could easily harvest it. So we would remove the algaes that concentrated in the bottom of this column, and then we could harvest that by a procedure where you float the algae to the surface and can skim it off with a net.
So we wanted to also investigate what would be the impact of this system in the marine environment, and I mentioned we set up this experiment at a field site in Moss Landing Marine Lab. Well, we found of course that this material became overgrown with algae, and we needed then to develop a cleaning procedure, and we also looked at how seabirds and marine mammals interacted, and in fact you see here a sea otter that found this incredibly interesting, and would periodically work its way across this little floating water bed, and we wanted to hire this guy or train him to be able to clean the surface of these things, but that’s for the future.
Now really what we were doing, we were working in four areas. Our research covered the biology of the system, which included studying the way algae grew, but also what eats the algae, and what kills the algae. We did engineering to understand what we would need to be able to do to build this structure, not only on the small scale, but how we would build it on this enormous scale that will ultimately be required. I mentioned we looked at birds and marine mammals and looked at basically the environmental impact of the system, and finally we looked at the economics, and what I mean by economics is, what is the energy required to run the system? Do you get more energy out of the system than you have to put into the system to be able to make the system run? And what about operating costs? And what about capital costs? And what about, just, the whole economic structure?
So let me tell you that it’s not going to be easy, and there’s lots more work to do in all four of those areas to be able to really make the system work. But we don’t have a lot of time, and I’d like to show you the artist’s conception of how this system might look if we find ourselves in a protected bay somewhere in the world, and we have in the background in this image, the waste water treatment plant and a source of flue gas for the CO2, but when you do the economics of this system, you find that in fact it will be difficult to make it work. Unless you look at the system as a way to treat waste water, sequester carbon, and potentially for photovoltaic panels or wave energy or even wind energy, and if you start thinking in terms of integrating all of these different activities, you could also include in such a facility aquaculture. So we would have under this system a shellfish aquaculture where we’re growing mussels or scallops. We’d be growing oysters and things that would be producing high value products and food, and this would be a market driver as we build the system to larger and larger scales so that it becomes, ultimately, competitive with the idea of doing it for fuels.
So there’s always a big question that comes up, because plastic in the ocean has got a really bad reputation right now, and so we’ve been thinking cradle to cradle. What are we going to do with all this plastic that we’re going to need to use in our marine environment? Well, I don’t know if you know about this, but in California, there’s a huge amount of plastic that’s used in fields right now as plastic mulch, and this is plastic that’s making these tiny little greenhouses right along the surface of the soil , and this provides warming the soil to increase the growing season, it allows us to control weeds, and, of course, it makes the watering much more efficient. So the OMEGA system will be part of this type of an outcome, and that when we’re finished using it in the marine environment, we’ll be using it, hopefully, on fields.
Where are we going to put this, and what will it look like offshore? Here’s an image of what we could do in San Francisco Bay. San Francisco produces 65 million gallons a day of waste water . If we imagine a five-day retention time for this system, we’d need 325 million gallons to accomodate, and that would be about 1,280 acres of these OMEGA modules floating in San Francisco Bay. Well, that’s less than one percent of the surface area of the bay . It would produce, at 2,000 gallons per acre per year, it would produce over 2 million gallons of fuel, which is about 20 percent of the biodiesel, or of the diesel that would be required in San Francisco, and that’s without doing anything about efficiency.
Where else could we potentially put this system? There’s lots of possibilities. There’s, of course, San Francisco Bay, as I mentioned. San Diego Bay is another example, Mobile Bay or Chesapeake Bay, but the reality is, as sea level rises, there’s going to be lots and lots of new opportunities to consider. (Laughter)
So what I’m telling you about is a system of integrated activities. Biofuels production is integrated with alternative energy is integrated with aquaculture.
I set out to find a pathway to innovative production of sustainable biofuels, and en route I discovered that what’s really required for sustainability is integration more than innovation.
Long term, I have great faith in our collective and connected ingenuity. I think there is almost no limit to what we can accomplish if we are radically open and we don’t care who gets the credit. Sustainable solutions for our future problems are going to be diverse and are going to be many. I think we need to consider everything, everything from alpha to OMEGA. Thank you.
FEATURED IMAGE CREDIT: eutrophication&hypoxia