Researchers at The University of Queensland (UQ) are working with industry and research partners to tap into the huge energy resource of the sun by designing solar-driven technologies based on algae.
This exciting opportunity, together with new discoveries about the processes involved in photosynthesis, is supporting next-generation solar biotechnologies.
Using electron microscopy, researchers from UQ’s Centre for Solar Biotechnology have identified the elusive cyclic electron flow (CEF) supercomplex, which is key to keeping photosynthesis running smoothly.
The discovery has the potential to fast-track the design of next-generation microalgae systems to meet the world’s growing energy needs – a challenge Professor Ben Hankamer, director of UQ’s Centre for Solar Biotechnology, says is becoming increasingly urgent.
“By 2050, the human population is expected to grow from 7.5 towards 9.8 billion people, resulting in a greater demand for resources,” says Hankamer. “We will need about 50% more fuel, 70% more food and 50% more water. These goals will have to be achieved while eliminating close to 100% of carbon dioxide emissions by 2050 if we are to avoid endangering the world’s ecosystems.”
The Earth receives a huge amount of solar energy - more than 5000 times the amount needed to power the entire global economy. Thus, the scale-up of solar-powered industries is a key focus. Over billions of years, single-celled green algae (microalgae) have evolved to tap into it and support the biosphere through the production of oxygen and biomass, which consists of a complex set of biomolecules. These provide us with food, fuel and a wide range of renewable feedstocks for industry.
Hankamer says if their photosynthetic power is tapped, microalgae could renewably provide all of the world’s aviation, shipping and diesel fuel, using only 0.2% of the world’s surface.
But to achieve this, researchers also needed to better understand how the photosynthetic processes work. The solar-driven photosynthetic interface of microalgae is based on intricate biomolecular structures that capture and convert sunlight into chemical energy, which is stored as high-energy molecules called ATP and NADPH.
Two pathways keep photosynthesis running smoothly to adjust to natural light levels and balance the cells’ ATP and NADPH requirements; linear electron flow is a biomolecular chain producing ATP and NADHP, while cyclic electron flow regulates the synthesis of extra ATP.
Tracking down what controls this adjustment has been no easy task. While previous studies had identified the CEF supercomplex as a key component of this process, until recently its physical existence and structure had not been determined.
By purifying and analysing the CEF supercomplex from the green alga Chlamydomonas reinhardtii, a species that is well-suited to industrial applications, Hankamer and colleagues were able to identify how its two key components, photosystem I and cytochrome b6f, were arranged. This revealed how these components adjust according to the light conditions, enabling the algae to maintain a state of equilibrium.
Uncovering the biological machinery of microalgae is just one part of the puzzle. Another challenge is to streamline the production process to make the price of algae-derived fuels affordable to the wider market. Professor Hankamer estimates that the price of algae-generated diesel is currently about three times higher than commercial diesel.
To drive this price down towards parity with current prices for fossil fuels, the UQ team use integrated techno-economic and lifecycle modelling to map out the whole fuel-production process. They also use robotic systems to pinpoint the best nutrient and light conditions for cultivating different algae strains. Combined, these approaches help to guide the design and development of next-gen algae systems.
“There has to be an economic, social and environmental benefit to provide robust and sustainable solutions if we are to address the challenges of climate change,” says Hankamer. “Our modelling defines pathways to achieve cost-competitiveness with fossil fuels and helps to fast-track efficient scale up of the best technology sets.”
Algae-based fuel systems have a number of advantages – they can be located on non-arable land or on oceans, they use salt water, they capture carbon dioxide and they minimise nutrient and water losses. This largely eliminates the food versus fuel concerns associated with first-generation biofuel systems such as corn ethanol, and enables a transition to a food and fuel future.
Co-production strategies that couple fuel synthesis with the production of other products – such as food, medicine, bioplastics, livestock and aquaculture feeds and clean water – further support the development of commercial renewable processes.
In addition to providing environmental and social benefits, Hankamer says that developing such processes can generate multiple income streams, helping to boost profitability, create quality jobs and establish a sustainable economy based on renewables.
To date, Hankamer and his team at UQ have worked with more than 20 industry partners to advance the development of commercial solar-powered biotechnologies.
“Renewable electricity systems like wind power and photovoltaics are excellent examples of renewable technologies that are now mainstream and reducing electricity prices,” he says. “But we use only about 20% of our energy in the form of electricity. In contrast, 80% of global energy is currently used in the form of fuels, for aviation, shipping, long haul transport and industry. If we do not scale up renewable fuel options as a matter of urgency, including emerging fuels such as hydrogen, which is of increasing international importance, we have very little chance of preventing potentially dangerous climate change.
“UQ’s Centre for Solar Biotechnology is therefore focused on driving the science and development of robust technology options to support industry and government to implement sustainable solutions.”