Bioplastics... from poo!
Could we switch to an alternative that isn’t so long lasting? Bioplastics aim to do this, by using alternatives to oil in the production process. One team is aiming to cut waste even further by making bioplastics from waste itself! Georgia spoke to Damian Laird at Murdoch University in Perth.
Damian - We like to tell people that we’re making plastics from poo but, in reality, what we’re trying to do is utilise resources that are in waste streams and turn them into something profitable. Rather than just basically treat them and send them out into another stream, try and make a product out of them.
Georgia - What kind of product can you make from sewage?
Damian - To be frank, we don’t quite use the sewage. We use the bacterial cultures that are in the sewage and they can produce a bioplastic. That’s biodegradable and we can use it for packaging and some other types of things and replace oil based plastics.
Georgia - Would this look like an ordinary plastic? Would it smell?
Damian - No, no, they just look like ordinary plastics at this stage. They definitely don’t smell, the cultures themselves don’t even smell which is great because it makes the lab much more interesting. But, yeah, we’re hoping that we can reproduce the same characteristics of an oil based plastic but hopefully use a biological process to get it done, so whilst the biological process is cleaning the water we’re getting a product at the same time.
Georgia - How does this technology work?
Leonie - My names Leonie Hughes and I’m a lecturer in chemistry at Murdoch University in Perth, Western Australia.
Basically, it’s the equivalent of us eating too much food and getting fat. The bacteria are put under conditions where they are given far too much food, but not enough of an oxidant source, such as oxygen or ammonia, something like that. So they get too much of chips and not enough fruit and veggies and exercise. Under those conditions they effectively store the rich carbon source that they get given so that they can hide it from other bacteria. It’s an evolutionary thing that advantages them over other bacteria. And then, under conditions where they suddenly have no external source of carbon but a rich source of oxygen or ammonia, they can then use that to continue growing when no-one else can.
Georgia - I’m imagining the bacteria equivalent of a hamster stuffing seeds in its cheeks?
Leonie - Pretty much. It actually form vacuoles in the cells that you can visualise as big lumps of plastic basically.
Georgia - What do you have to put into the bacteria to get this plastic out?
Leonie - Many many many bacteria are shown to do this, obviously some are better than others. You just need to give them something like glucose or vinegar, something rich in carbon, and let them do it. Just try not to give them too much oxygen or too much nitrogen at the same time and they pretty much go for it themselves.
Georgia - Then they create these bags of plastic in their cells, how do you then get this out of them?
Leonie - At the moment this is the un-environmentally friendly bit, potentially. This is the bit where we have to use solvents and thing to kill the bacteria and extract out the plastic, so that part of it, at the moment, is not looking particularly nice. However, there are some people doing some research in similar areas with things like algae that can extrude thing like bio oils or potentially even the plastic so there are other ways of looking at it.
Georgia - How is this plastic different from ordinary plastic?
Leonie - It’s not. It’s what’s classed as a thermoplastic. It still has the same kind of properties that plastics that you see in shampoo bottles and things have. It does need some post-processing, so it doesn’t have the cross-linking things, the more complicated third degree structure that plastics have that get used commercially. But those are things you can add in a chemical sense after they’ve been extracted from the bacteria. We might be able to design the feed that we give the bacteria better to enhance the production of copolymers, so polymers made up of more than one monomer, more than one building block and, if we do that, plastics will come out closer to commercial plastics at that point already.
Georgia - How easy will this be to scale up? How are you going to get a usable amount of plastic from this process?
Leonie - Yeah, it’s not trivial. We would have to do things like high density cell cultures and they’re quite hard to manage. You would need to have membrane technologies and things like that to have maximum, maximum, number of bacteria in small footprints of space so that you’ve got minimal amount of water, maximum amount of bacteria and, therefore, ease of extraction of the bacteria. These are not trivial questions but, if we can get the technology working at the lab scale, then that’s where we would link up with an engineer who would solve, hopefully, those problems for us.
Georgia - Then, at the end of this process you hopefully have a plastic that is biodegradable. Why is it biodegradable?
Leonie - Just purely because of the nature of why the bacteria make it. They make it so they have carbon source later when they have abundance of oxygen, but they don’t have any carbon external to the cell. It has to be degradable by them otherwise they wouldn’t have made it for the advantage of getting the fat in their cells and stealing it from other bacteria, so that automatically means it’s biodegradable.
Georgia - Best case scenario: what are you hoping that this can do?
Damian - The big picture is that we could hopefully locate one of these plants next to an industrial site, take their waste water, clean up the nitrogen in particular that comes out of it that the bacteria can use, and then also produce a product. We can hopefully create a product that we can change that product at will for different uses.
One of the really big ideas we’d like is not just to take traditional waste streams like you would expect in a wastewater treatment plant, but industrial waste streams as well. There are lots of industries - wineries for example, breweries that use use bacterial cultures to clean their water before they release it, but that contains a lot of carbon. We hope that what we can do is create carbon, create these polymers from that waste carbon in a sense, and then may be able to produce the packaging for the beer along the way.
Georgia - Using a product that would have been created anyway by this other process that would have otherwise gone to waste?
Damian - Yeah. And so that whole process them becomes very microbiological because you use yeast to make the beer in the first place. Bacteria in yeast to clean the water and then produce the packaging potentially for the product, which is amazing.