Catalysing Fuel Production with Bionanocatalysts
Meera - But this integration doesn't stop at the production of hydrogen gas. Bacteria are also being used to produce components of the hydrogen fuel cell itself. When converting hydrogen to electricity, fuel cells use catalysts made from metal such as platinum and other platinum group metals to speed up the reaction. But now, a new development in the field of biomaterials is converting bacteria into these catalysts. By combining bacteria with small traces of these metals, Angela Murray, is producing a new generation of materials known as biocatalysts and reducing the demand on this scarcely available platinum group metals.
Angela - Platinum and in particular the platinum group metals are a unique group of metals because the price of them is very high and over 75% of the world supply is based in South Africa. So as a result, it means there's a focus on recycling these strategic metals. We use a number of sources. One of which is road dust because your car catalytic converter actually loses somewhere between 30 and 70% of its platinum group metals over the course of its lifetime as you drive it around, and this end up into road dust. Well, to look at incinerater ashes from municipal wastes. We also look at electronic scraps. We look at industrial slag materials as well. To give you an idea, if you were to go to South Africa which has the richest deposits on Earth at the Bushveld complex, you'd find levels of about 2 to 10 parts per million pgm precious metal that's platinum group metals. Now that's the richest place on Earth and that's mined from deep underground which is both energy expensive and environmentally damaging. If you look at something, for instance, if we take the raw dust as an example, you're looking at levels of 1 to 2 parts per million total platinum group metal content and the road dust. And although that sounds low, that's approaching a low to intermediate grade mine, but the material is already on the surface of the road, it's not needing to be extensively crushed and processed, and it's ready to be collected.
Meera - And so, what's the process?
Angela - The technology that we've developed looks at taking that road dust after collection and physically processing it in order to concentrate up these platinum group metals, the metals we want. From all the different components of road dust that we are not interested in via magnetic separation, electrostatic separation, a gravity technique. So what you're doing is just separating on the basis of the material's, properties to get the platinum and associated metals that you want out of all the other materials there which you don't want.
Meera - What are the next steps to really kind of fine-tune that and get platinum?
Angela - The idea is you really have 2 options. So the first option is you can send us material for smelting which is the traditional recycling route for PGMs. Instead of taking these metals for smelting, which is obviously melting them at high temperature - it's energy expensive - we can also leech these metals into a solution so you end up with the solution of metals instead of powder, and we can then add bacteria. And these bacteria have a neat trick in that they're able to reduce the metals onto their surface. So what you end up with, if you can visualise it, is a bacteria with a little metal jacket, lots of tiny little particles on the surface of it.
Meera - All of which are platinum.
Angela - Well, they can be platinum, they can be palladium. You can do mixes of metals, so they're all precious metals and we call these bio nanocatalysts because these bacteria, once they had the metal deposited onto them, have a functionality in their own right. And so actually, they can be used as the platinum or palladium source for fuels cells. So we can actually make a biological based platinum catalyst which can then be used in your fuel cells.
Meera - So all in all, these are biologically and environmentally friendly methods of generating both the fuel and the fuel cells.
Angela - You're taking the waste biomass and you're producing a clean hydrogen to run the fuel cell, and then you're taking precious metals that have been recovered from wastes, and you're using those to produce the precious metals needed for the fuel cell. So really, you're taking 2 different waste materials and you're using it to generate clean energy. It's the whole number of projects at the university coming together to deliver this new technology.