Biodiesel based on algae
Emma - I'm riding on one of Cambridge's bio buses, so named because they run on 100% biodiesel. At the moment this comes from recycled cooking oil, but in the not-so-distant future, biodiesel could come from quite a different source - algae. Joining me on board are three researchers from the Department of Plant Sciences at Cambridge University: Elena Kazamia, Jit Ern Chen, and Dr. Nic Ross. They all work with algae, and they're here to tell me about its potential as a fuel source.
Elena - We're definitely running out fossil fuels, and even if we are not running out any time soon, we are definitely running out of cheap fuel, so the necessity for biofuels is increasing. Algae are a very general group of organisms - pretty much anything that lives in water and photosynthesises is algae. They can be single-celled or enormous - giant kelp for example, the big seaweed, is also technically algae. There are many reasons why we prefer to grow algae on a large scale for biodiesel production over any conventional land plant: algae do not grow on arable land so you're not competing with food production.
Emma - So how do you get from algae photosynthesising the sort of diesel that you could put into a car or into a bus?
Elena - Some algae, much like the cells in our bodies, store energy in the form of lipid. Some algal species can have up to 70% of their mass in oil, and so all you need to do is break that cell open and release the fuel molecules. You can do that either using solvents on an industrial scale or one of the things we are investigating in our laboratory is the use of enzymes to break some of the cell wall components, which then makes the extraction of the oil a lot easier.
Emma - Jit Ern, once you have extracted these oils from the algae, how do you then convert them into actual diesel?
Jit Ern - The molecule that we are actually extracting from algae are known as triacylglycerols, and you cannot actually put these molecules into an engine. They are not very friendly for internal combustion so what you have to do is to use a process called transesterification. What transesterification does is it converts triacylglycerol into molecules known as fatty acid methyl esters (FAMEs) and these molecules are structurally very similar to the diesel that you get from petroleum, and therefore they can be using car in engines with little or no modification.
Emma - Nick, is it possible to scale this up so you can produce diesel on a much more industrial scale, the scale on which it is demanded at the moment?
Nick - Algae are already grown on an industrial scale to make different types of products. In Australia, for example, they grow algae in giant ponds to get various types of antioxidants. So, you could do a similar thing - growing algae in large ponds. You could really scale up. And the size that you would want to scale up to is enormous - it would be something like 10,000 hectares as a starting size of algal ponds.
Emma - So what's standing in the way now?
Nick - The problem right now is that it is just too expensive to make diesel from algae and that is just because the costs are really quite large - building massive ponds, the costs of extraction. Even though it is a really attractive way to get energy, at the moment it costs about twice as much to make it as you can sell it for. The efficiency of the process is something like 2%. So we are looking at ways in which we could actually improve that. We are looking at ways to genetically engineer the algae to make them more efficient at the way that they capture light and then can convert that into, ultimately, the types of fuel molecules that we want.
Emma - And I understand that is something you are looking at, Jit Ern. You are actually studying the different genetic pathways algae use to produce oils and, more importantly, the right kinds of oils?
Jit Ern - Yes, the idea is that although algae do produce oils, the oils that they produce may not necessarily be the ones that we would like to put into our engines. One of the biggest problems of biofuels is that certain types of biofuels tend to freeze under low temperatures and therefore you have to do something. You can either put some sort of chemical in the fuel to make them have a lower freezing temperature or you can genetically engineer the algae so that they produce oil that is more liquid under low temperatures. And there are various other things - how much and how strongly these fuels burn are dependent on the characteristics of the few molecules, and all that can be manipulated genetically.
Emma - How would you then genetically manipulate the algae to produce large quantities of those kinds of oils?
Jit Ern - The first step is to shut down or reduce the amount of what we call secondary pathways or side-chain pathways - the alternative pathways that would take away molecules that we want to convert into biofuel and change them to something else. And you can do that in two ways - you can either improve the genes that are in the pathway you want, or you can remove the genes that are in pathways that you don't want. But obviously, we have to be really careful because these are living organisms - if you tinker too much with the internal genetics of the organism it may die, or it may start to produce something that you don't want.
Emma - Elena, how long do you think it will take until a bus like this is run on algae biodiesel?
Elena:: I think it depends on how optimistic you are. The optimists say we are ready to scale up, the pessimists say it will never happen! Another fundamental thing that stands in the way of production on a large scale is that we simply cannot replicate what we are doing in the lab outdoors. We simply do not know how the algae, as living organisms, interact with their environment. So, even though we have these amazing strains that we are developing in the lab that are genetically modified, can have very good lipid production, have fantastic efficiencies, if they then get eaten by something or if your ponds get populated by some other competing organism that contaminates it and you have to shut down your production system, that is also a very bad thing. The technology is not quite ready, the research is ongoing, but there is definitely a lot of will within the scientific community and so, I think somewhere around 10 years perhaps.