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Artificial photosynthesis

THE ROOTS of human evolution are closely linked with plant existence. The most important chemical process running in biological regimes is photosynthesis. The significance of this process can be assessed by the fact that biggest machinery providing food and oxygen to the world is dependent on this particular phenomenon. Each year green plants use to produce about one thousand billion metric tons of organic matter and over 700 billion metric tons of oxygen by using carbon dioxide. That organic matter is used as food by each and every secondary consumer including human beings. And oxygen is the only source for the process of breathing on planet. In this way photosynthesis is guarantor of survival and food security. Food production is the biggest attribute of this particular process. In this century energy crisis has emerged as one of the biggest conundrums along with food security, climate change and eco-degradation. We have to feed more number of mouths, have to run more number of vehicles, have to produce more electricity, have to explore more sources of fuel and surely have to find alternative energy options. Present scenario of energy worldwide is very alarming as the biggest hub in the form of fossil fuels (petroleum and gas) is depleting and nothing is there to replenish it. Scientists have tried a lot to discover renewable and non-conventional resources of energy to fulfill needs of modern era. But the problems associated to all such options are of critical nature limiting their feasibility and sustainability. For example wind or water energy requires large scale and complex installments and is not feasible everywhere in the world. Similarly the nuclear energy has wide range of environmental hazards and social concerns. Meanwhile solar energy has come up as a pragmatic option but still not much adaptable and practical. So, an energy source is required which will be more natural and long lasting.

Struggling but pondering minds of naturalists have discovered a very unique approach to optimize energy needs of future. The concept is not much newer but getting famous now because of some breakthroughs in the field. The mystery of Artificial Photosynthesis is very simple in terms of scientific understanding but very tough in terms of taking form of technology.

We know very well that photosynthesis is basic process undergoing in green plants in which solar energy is converted into chemical energy and carbon dioxide is fixed into carbohydrates. A very sophisticated and complex organization has been made by the nature in plant leaves to run this process. This micro level setup involves energy capturing chloroplast molecules and a very fine sequence of proteins to govern this energy in the form of electrons within the biological membranes. The most important molecule is water which splits into its basic components - hydrogen and oxygen - evolving electrons for the smooth running of electron transport chain which is the basic part of light reaction of photosynthesis. A very organized set of biomolecules and chemical elements offering help in the whole process is present as enzyme. Manganese is the basic element which acts as carrier of electrons from photolysis of water in oxygen evolving complex. Here oxygen is released in the environment through leaf stomata which we use to breathe. On the other hand electrons evolved contribute towards the formation of NADPH which is the product of light reaction and used for carbon dioxide fixation in later phase of photosynthesis. The movement of hydrogen ions across the membranes through world’s smallest rotary motor (ATP synthase), helps to form biological energy unit (ATP). This energy is the base of life.

Now imagine practicing the whole chemistry of photosynthesis artificially outside the plant body. It seems very easy theoretically as the whole process is well defined step by step through intensive research of botanists and plant physiologists but it is nearly impossible. The difficulty lies in each and every step of this super organized process. The concept of mimicking photosynthesis has been developed to use electrons released during photolysis of waters for the generation of electricity. Simply it is an idea of wiring up nano-structure of leaf to extract electrons from it to run electrical devices as we call running electrons “electricity”. In this way, scientists are eager to have “bioelectricity” in future. This particular operation is not possible with natural photosynthesis because its rate is very slow in efficiency under extremely optimum conditions is only two per cent. So, the idea of developing an artificial leaf like structure to govern chemical reaction of photosynthesis which are surely not as simple as I briefly discussed. There are more than 100 reactions occurring naturally during the whole process of photosynthesis. But researchers are only interested in the process of water breakdown artificially but believe me the very same process occurring smoothly in leaf requires a huge amount of energy in artificial conditions. This is the beauty of nature and the reason why scientists are compelled to copy the nature.

Another aspect of mimicking the photosynthesis process is for the development of natural fuel cells. The idea is to pump out the hydrogen produced during photosynthesis. It is very common in modern industrial countries to use hydrogen fuel cells. Hydrogen is basically very fine and efficient fuel but the cost related to it is the real problem. What if such precious fuel comes from a natural process (photosynthesis) which is not going to stop as far as universe exists? Of course it will be a great achievement and an unlimited resource of eco-friendly and sustainable energy. But again it is very hard nut to crack. Scientists have done a lot of homework on this process as well and proof of concept exists as some geniuses have figured out the opportunities, orders, disorders, limitations and up to certain extent options for this unique and revolutionary technology. They have a hope that in future maybe in near future this aspect will be practically improved and they will be able to get energy in this way. However the other approach (production of bioelectricity) is still very much immature and requires massive basic research. Then there will be the way forward to asses those refined theoretical assumptions practically.

Artificial photosynthesis will be a bright part of biological research and the interests of organizations, authorities and nations will keep rising on this very option. The speculated and theoretically justified benefits of this approach include:

1   Non degradable and sustainable energy production

2   Cheapest electricity provision

3   Finest and easy coming fuel

4   Improved resources for industrial as well as domestic use

5   No environmental hazards

     Economic boost

6   Revolution in energy and engineering sectors

All these benefits are very encouraging. Now it’s up to scientific tiers that how much promising is this approach and will they be able to acquire a command so that they can use it for welfare of humanity. There are numerous challenges which no doubt much bigger than the perspective of any single individual or organization. Major constraints which are mostly of technical nature are as follows:

i    Complex nature of photosynthesis really difficult to copy

ii   Enzymes working in living systems do not fit in artificial environment

iii  Elements which have identified as catalysts for artificial synthesis are very costly like gold etc

iv  It is tough to develop nano structures and electrodes that can work to capture electrons

v   Photolysis of water is high energy requiring reaction outside living body and optimum substrates as well as catalysts are not present

Although there are challenges but scientists are still optimistic about the success of artificial photosynthesis. Future endeavors are well focused on technological advances in this regard. Large scale scientific projects involving world class educational institutes and funding agencies have been initiated. Researchers have embarked upon a true expedition for the sustainability of earth and of course it is a step forward in the battle of survival. Realization of this wonderful idea has many limitations but still it is possible through integration of sound physiological knowledge, excellent engineering skills and fascinating molecular approaches. A lot of time, energy, skill, intellect, capital and above all intriguing will are required to reach this goal. It is a win-win approach beyond any doubt and will change the world altogether once after coming in frame of reality.

The writer is M.Sc. (Hons.) Agriculture, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.


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