Engineers have long taken inspiration from nature when designing technologies. From solar panels (inspired by a grooved leaf), to wetsuits (which mimic an otters’ blubber), to aeroplanes (which borrow their design from birds).
However, it may come as a surprise that plants are now giving clues to the Defence industry on how to engineer energy efficient space ships.
Specifically, how to extract water from waste and keep astronauts hydrated for long stints away from earth, without the price tag involved in carrying water weight.
“One of the big issues with astronauts in space is the water filtration. Water is very heavy and it has cost as much as $250,000 per day to supply astronauts with the 11 litres of daily water they need,” said Associate Professor Caitlin Byrt of the Australian National University.
To combat this, astronauts have long been capturing bodily waste, such as urine and sweat, and drinking its repurified contents. However, the original filtration systems had a tendency to get clogged and let contaminants through.
“Size exclusion water filters regularly broke down and cost a lot to maintain, so there was a need to develop more reliable, efficient systems that could deliver a cleaner water product,” Prof Byrt said.
“This has been achieved by NASA and a company called Aquaporin based in Denmark. They used water selective proteins called aquaporins, similar to the aquaporins that living cells use for water filtration to build better water filters”.
Turning to nature
Inspired by the success of using water selective aquaporins in filters, Prof Byrt and team looked to nature for examples of where other resources are naturally separated from complex mixtures.
“Each year half of the global precipitation will pass through plants. They are the greatest filter on Earth and they play a critical role in regulating our global water cycles, so we knew this was a good place to focus our attention,” she said.
The team closely inspected the mechanisms plants use to filter metals, minerals and nutrients from the ground beneath them. Examples of these resources include ammonia, boron, cobalt, copper, lithium, nickel, nitrogen, phosphorus, potassium, urea, rare earth elements and zinc.
“Plants have evolved processes over millions of years, whereby they capture solutes from the soil, draw them up in the form of a complex solution, separate out the nutrients, metals and minerals into different membrane bound compartments, and transpire clean water from their leaves.
“There are some types of proteins called aquaporins that can transport 4 billion water molecules per second and exclude other molecules, while other aquaporins can transport valuable metals, minerals and nutrients. It is these types of mechanisms we wanted to mimic for our technological advance,” she said.
During space missions waste is bagged and attached to the inside of the space ship. The waste contains resources that could be useful, but they are trapped in the waste. For longer space missions, a more efficient process may be required, whereby molecules in the waste are reused, Prof Byrt said.
“Ideally you want to reuse all of the waste, not have it sit there and take up room or add weight to the vessel. That’s a challenge where plant-inspired technologies can deliver solutions.
“Things are often labelled waste, not because they are void of anything useful, but because their useful constituents are in a jumbled mess and cannot be accessed. With advances in precision membrane separation technology the resources trapped in waste can be separated for reuse. We are reconceptualising waste as a target for extracting valuable resources,” she said.
In addition to clean water, Prof Byrt’s technology could also help extract nutrients, metals and minerals relevant to growing plants and clean energy technologies.
“We can modularise separation systems so that they pull out target elements in the process of drawing out clean water. This means that hopefully in the future astronaut waste could efficiently turn into a resource that can safely support growing plants during space travel.”
As well as working on membrane separating technologies that borrow their design from plant proteins, Prof Byrt and team are engineering plants that can live in challenging environments on Earth and in space.
“The study of how plants adapt to extreme environments can advance the capacity to develop plants that are optimised for space growth conditions”.
There is a collaborative team called Lunaria One that will send a growth chamber to the moon in 2025 to grow plants.
“Space agriculture developments and advances in membrane separating technologies are important for sustainability. If you want to support plant propagation and minimise waste, you need to have capacity to manage and recycle primary resources in space.”
It also has applications on Earth
Alongside the potential of separation technologies in space, the technology has huge offshoot benefits for sustainability on Earth. Here, water filters containing aquaporins have already been successfully adapted for a wide range of applications.
“Most of our team have a background in plant science. We have worked extensively on bioengineering crops to make them more tolerant to saline soils, and make them more nutrient use efficient. The work we are doing that relates to sustainability in space is a natural extension of this,” Prof Byrt said.
In the future, crop and separation technologies are expected to have further applications in agriculture, aquaculture, manufacturing, mining and recycling industries.
“Any industry that generates waste can benefit from separation technology,” Prof Byrt said.
“Mining companies can clean up their waste and pull-out additional resources that they otherwise wouldn’t have had access to. It’s an environmentally-friendly approach. There is also great potential in manufacturing.”
Sharing more about the technology and what it means for space travel, Prof Byrt will join a stellar line up of speakers at this year’s ADM Space Conference, hosted by Informa Connect.
The event will feature insights from Enrico Palermo, Head of the Australian Space Agency; Bec Shrimpton, Director of Defence Strategy and National Security at ASPI; and Sarah Free, Assistant Director of Business Innovation at the ACT Government.
The conference will be held 28 November at the Hyatt Hotel Canberra.
Learn more and register your place here.
About A/Prof Byrt
Caitlin Byrt is a bioengineer working on developing future crops and membrane biotechnologies. The membrane biotechnologies her team are developing are designed to enable precious metal, mineral, nutrient and clean water resources to be harvested from wastes so that they can be reused.
Membrane biotechnologies can enable reuse of the nutrient resources required for growing crops and reuse of the metal and mineral resources relevant to renewable energy generation and storage.
Caitlin is an Associate Professor with the ANU Research School of Biology and serves as co-Director for Membrane Transporter Engineers (MTE) Pty Ltd, Deputy Director (Research) for the Australian Research Council Future Crops Centre, ANU InSpace Mission Specialist and advisor for the Lunaria One team who are working on growing plants on the Moon.