Team:Macquarie Australia/Project/Background

Background

For engineers, it is not money, but energy, that makes the world go around.

The ability to effectively and conveniently generate, store and access energy is the hallmark of the developed world. These systems extend to almost all aspects of our everyday lives; integral to transport, heating, industrial production, control of water supply, and recreation.

The requirement for alternative energy sources

Fossil fuels have been the powerhouse of Earth's energy needs in the 20th century and continues to be in the present. Their long formation time and high human rate of consumption led theorists to predict catastrophic economic consequences of exhausting the non-recyclable resource, cumulating in theories such as the famous 'peak oil' proposition (Hsu). While advances in technology for gas and oil exploration and extraction have solved (at least for now) the issues surrounding the scarcity of energy resources(Technology), the planet's capacity to withstand the release of carbon by-products remains a pertinent challenge to our generation.

Alternative, 'green' energy sources are those that directly harness incoming solar energy, and purpose it toward human use. It can be direct, converting photons to electricity in solar cells, or indirect, harnessing the power of the wind or the waves. These are characteristically green and renewable, producing few harmful byproducts. One of humanity's first energy sources was also renewable: the usage of biofuels, organisms that harvested solar energy and stored them as energetic organic compounds. These were burnt, and in the present time, fermented, allowing a useful conversion of solar energy to that useful for human purposes.

Solar Energy Redux: Obtaining Usable Energy

Despite the higher efficiency of direct photovoltaic conversion of photons to electrical energy, biofuels remain a relevant option. Concerns are raised regarding the industrial processes and hazardous materials involved in the creation of photovoltaic systems, often requiring significant fossil fuel energy to produce(Mohr et al., 2009), (Fthenakis et al., 2008). Biofuels are cheaper, requiring less capital and energy to produce. They are self-replicating and require uncomplicated maintenance. The drawbacks are in efficiency: high efficiency biofuels produce fuels capturing a peak of 6% of solar energy, whereas the thermodynamic limit of photovoltaics is around 14%(Sydney).

The salient difference is how the energy is used; biofuels provide an efficient mechanism for storing energy, sealing it within energetic organic compounds such as ethanol or hydrogen gas, enabling relatively easy transportation and storage of energy in comparison to batteries, that are often heavy and lose energy over time. The place for biofuels in the 21st century is producing a convenient storage mechanism for energy, particularly for vehicles, where there is a need to carry fuel for long distances without opportunity to refuel on electrical power. Biofuel research and development in the 21st century has focused around high efficiency bioethanol production for these purposes(Liew et al., 2014).

Our Response

The Macquarie iGEM team aims to give synthetic biologists the tools for a bacterial powerhouse that can harvest solar energy. By developing an enzyme pathway capable of synthesising the primary component of photosystem-II, namely chlorophyll-a, the first step toward an entirely synthetic photosynthetic pathway is taken. These parts will also be expressed in a foreign but well characterised host, namely, E. coli K 12 strain.

It is hoped that by successfully engineering and demonstrating the capacity for this organism to express the relevant enzymes, and produce chlorophyll-a, that the ATP and NADPH produced by the photosystem can be used to produce biofuel substrates. Successfully coupling the photosystems products to known proteins for the production of substrates is one such future use, with proteins available to manufacture hydrogen (Higorani, unpublished), which may be transfected into an expression host to create an entire synthetic system for the production of hydrogen gas.

References

• Australian National University, Water and sunlight the formula for sustainable fuel - Newsroom – ANU.
• Fthenakis, V.M., Kim, H.C., and Alsema, E. (2008). Emissions from Photovoltaic Life Cycles. Environ. Sci. Technol. 42, 2168–2174.
• Hsu, J. Oil Production to Peak in 2014, Scientists Predict.
• Liew, W.H., Hassim, M.H., and Ng, D.K.S. (2014). Review of evolution, technology and sustainability assessments of biofuel production. J. Clean. Prod. 71, 11–29.
• Mohr, N., Meijer, A., Huijbregts, M.A.J., and Reijnders, L. (2009). Environmental impact of thin-film GaInP/GaAs and multicrystalline silicon solar modules produced with solar electricity. Int. J. Life Cycle Assess. 14, 225–235.
• Sydney, D.T.S.L. in A. at U. of For efficient energy, do you want solar panels or biofuels
• Technology, J.R., Energy Innovation: Policy and We Will Not Run Out of Fossil Fuels (Op-Ed).