Synthetic sugar for sustainable power?

Energy is a major challenge for the future with important consequences on the economic and political stability, food security, water supply, energy independence, pollution, and global ecosystem. Owing to increased industrial activities and growing population, the reserve of oil and other fossil resources will become, at best, rare, and costly for extraction and commercialization. For these reasons, sustainable energy is on the top interests of scientific and political programs in many countries where economic and industrial activities are main contributors of the emission of greenhouse gases. High accumulation of these gases is predictable to affect agriculture and to sharpen climate change in the next decades. To alleviate these effects, scientists and stakeholders need to addresses all potential hypotheses and approaches to develop sustainable energy systems that minimize the pollution and the negative effects of carbon dioxide (CO2) on the biosphere. Toward this objective, different approaches are currently under investigation based on various platforms such as water, microorganisms, plants and photovoltaic devices. Splitting of water, for example, is used to generate gaseous hydrogen using molecular catalysts such as molybdenum-oxo complex (Karunadasa et al., 2010), copper oxide photocathode coated with an amorphous molybdenum sulphide (Morales-Guio et al., 2014) or Silicon/Hematite core/shell nanowire array covered with gold nanoparticles (Wang et al., 2014). Various microorganism genera are also investigated such as microalgae (Gong and Jiang, 2011), bacteria (Kalscheuer et al., 2006), cyanobacteria (Quintana et al., 2011) and yeast (Buijs et al., 2013). Other options include genetically modified plants such as sugarcane (Arruda, 2012), maize (Torney et al., 2007), sunflower and soybean (Dizge et al., 2009). Each of these platforms has its own pros and cons. The production of biohydrogen for example encounters two major challenges relating to high production cost and low-yield (Gupta et al., 2013). Important sustainability issues also obstruct the production of biofuel from algae and plant platforms at industrial viable scales, admitting that a severe compromise would be accepted for biofuel production from crops to the detriment of food production. Moreover, crops-based biofuels can provide only a small portion of the huge amounts of fuels needed annually, estimated at the equivalent of 31 billion barrels of crude oil (Rhodes, 2009). Plant-based biofuels also require precious sources (water and arable lands) that are increasingly scarce, and it is much wiser to save them for more vital needs than energy. Algae, on the other hand, have greater potential than plants to be good alternative resources for renewable energy. However, algae require substantial amount of water and fertilizer resources for scalable production of fuels (Edmundson and Wilkie, 2013). Algal fuels also cannot be produced in large volumes in an environmentally sustainable manner, although crude oil has been produced in various experimental scales (Chisti, 2013). Moreover, there is a permanent need to fully recycle the nitrogen and phosphorous nutrients that are necessary for the sustainable algal biofuel system. Other alternative energy resources include nuclear and solar-based platforms. Nuclear is a highly risk adventure at local and global level, especially under unpreventable environmental disasters and uncontrollable climate change. The other safer approach is sunlight and its applications with photovoltaic devices. An ideal energy system, however, should offer the possibility to produce sustainable power while reducing CO2 emissions at the same time. An enhanced artificial photosynthesis protocol that uses CO2, water and sunlight to produce fermentable organic matter (sugar), in the same way that plants do for their own natural photosynthesis, would be an ultimate, or at least a complementary solution to other potential bioenergy alternatives, for both the production of biofuels and the reduction of CO2 levels. Figure 1 illustrates a streamlined scheme for a conceptual energy system inspired from photosynthesis process, starting by capturing sunlight and CO2 and ending by the synthesis of sugars. The synthetized sugar can then be conducted to a chamber (i.e., fermentation reservoir) where it could be converted to bioethanol by fermentation. Once realized, such an approach would not only offer the advantage to save valuable lands, freshwater and crops, but also to reduce CO2 levels and make industrial activities as desirable activities rather than culprit operations, because the CO2 emitted will be recycled permanently to feed the artificial system and produce bioethanol. In other term, the more CO2 emitted by industrial activities, the more sugar synthesized, and the more bioethanol produced. To enable maximum fixation of CO2, such a system is expected to be implemented near industrial factories that emit CO2 intensively. The composition, size, chemical, and physical properties of appropriate devices and materials intended for such a technology need to be scrutinized and