Science Interviews

Interview

Thu, 11th Jul 2013

Green Solar: the power of algae

Bob Lovitt, Swansea University

Listen Now    Download as mp3 from the show Souping up Solar

We’ve all got an image in our head of solar panels comprising of rows and rowsAlgae on a beach of shining blue sheets, but can algae, which naturally harvest the sun’s energy for their own energy needs, offers a more natural alternative to solar power? Dominic Ford was joined by Bob Lovitt from Swansea University who worked on this very problem through a European project called enalgae.

Dominic - Now first of all Bob, why algae in particular?

Bob - Algae offer a very productive way of capturing light and converting CO2 into biomass which can then be used in a number of ways to make energy or chemicals and so on. Compared to normal green of plants, they're very productive, people say of the order of 10 times more productive. So, if you think about a unit area of land, these organisms will produce significantly more amount of biomass compared to say, normal green plants.

Dominic - So, once you’ve used the sunlight to grow this mass of algae, what do you actually do with them?

Bob - That’s a very interesting question because there are lots of things you can do with them. You can basically dry them and burn them to get you energy back as heat or you can refine the materials into protein, as a feed, then use those to generate energy, or you can actually sell the algae as feed for fish, and things like this in farming situations.

Dominic - I guess when I think of algae, I think of blooms in the ocean and if I remember rightly, there was a massive bloom in China just before the Olympics a few years ago. Why are you growing it in farms rather than just fishing it out of the ocean?

Bob - Normally, when you get algal blooms, the first is that they can be very harmful. A lot of algae of the wrong sort contain toxins and these toxins can be – if you’ve got a water say a desalination plant and you want to make drinking water a sea water, if you have these algal blooms, they can actually contaminate the water and cause really serious problems. Also, if you look up in the natural systems, they're mixed systems. They're basically naturally selected and consequently, are optimal maybe for growth in those certain conditions, but they don’t make the products that make potentially more value out of the algae.

Dominic - I guess, any solar-powered generation scheme, what's important is how much sunlight you're collecting. So, I presume – have you got a farm somewhere with a huge collecting area of sunlight?

Bob - We basically are working in what we call photobioreactors. These are contained systems as opposed to raceway systems which is another way of doing it. Basically, large areas of water, looking like canals about 30 cm deep.  At this stage, 2 or 3 hectares of these are used to generate the algae. We go for photobioreactors which are different. They're basically pipes. They're slightly more efficient in the way they operate and we can contain the algae themselves in a much better way and control what we’re doing with them. Raceways are far more open to contamination. You can get a duck swimming across the top of the algal pond and so on. This means that as like any other farming process, if you get contamination, you have to control that and so, within a raceway, there are a number of problems associated with that which you can avoid if you go to a photobioreactor.

Dominic - You said at the start that algae are much more efficient than other forms of biofuel. What's the difference between covering these 2 or 3 hectares with algae versus planting crops that you might then go and burn?

Bob - The main differences are, that you would need to supply the nutrients that they require far more intensively. This means that we need sources of carbon dioxide like power stations. We need nutrients like phosphate and ammonia, and another nitrogen sources which we get from sewage wastewater treatment systems when we’re cleaning up the water, remove the nitrogen phosphorus. What we can do is integrate these processes to effectively combine the waste products if you like of these processes to make algae. The fact is, what we’re doing, by integrating with waste processes, at the same time, we can make much better use of nutrients and so on.

Dominic - You're killing two birds with one stone. You're dealing with the CO2 and you're also getting useful energy out of it.

Bob - Yes.

Dominic - How do you harvest energy out of this at the end?

Bob - There's a number of ways in which you do that. Basically, the calorific value of algae is about – I think it’s 28 mega joules per kilogram – something like that. If you burn the waste, that’s what you get in the calorimeter when you burn algae. If you think about it, that energy is the raw energy, but what you're also doing here is you can make carbon materials which replace other forms of energy if you like. If you're going to make plastics and so on, you start with a fossil carbon. You can substitute that carbon from algae into those manufacturing processes. So, you effectively save a lot of energy that way because you're using the embedded energy that’s fixed in the organisms to make substitute for other energy forms really.

Dominic - Am I right in thinking that the facility you got at the moment is actually a test. How are you going to scale that up to industrial production?

Bob - The way we’re doing this is that we take what we call a biorefinery approach which is that you cannot expect to make money from the energy that you're capturing using the algae. If you look at the amount of energy you put into the system compared to the amount of energy you get out of it, i.e. the energy put in is things like the ammonia you need, the pumping power you need and so on to move the liquids around, and you compare that with the energy you get out of the system then what you find is you're around 1.3, 1.5 energy return. In other words, you're not making a big energy surplus, but what you are doing is fixing CO2 and you're making chemicals from that, effectively very little energy releasing CO2. So, you've got a low carbon way of doing things.

Dominic - So, you're essentially making the power stations cleaner which are providing the CO2 to the process.

Bob - That’s right and then the other approach we’re taking is we’re taking things like anaerobic digesters and you take the waste products from an anaerobic digester that’s maybe setup in a combined heat and power system where you basically take waste materials, you digest them and you make the methane. We can then burn the methane in an engine and then we can take the CO2 from that engine and put it into an algal bioreactor.

At the same time, we can then take the residuals, the nitrogen phosphate residuals from the anaerobic digester, and we can put that into the reactor, and so, you then generate all the nutrients basically from the anaerobic digester. So effectively, what you’ve done is you’ve recycled a lot of the waste nutrients back into the algae. We can then refine the algae, basically remove the protein and we can make animal feed or something from that protein while the rest, the remaining waste material can be put back into the digester.

So, what you're doing here is you're using a lot of waste materials that need to be removed from the environment anyway and certainly, anaerobic digestion is now being seen as the way to get rid of food waste, rather than put it in landfill and things like that. So, you need another technology then on the end of the anaerobic digester to absorb the nutrients and then make new materials which then go back into the system to make food. So, you’ve basically closed the loop on the whole process of nutrient flows in the environment.

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