In the first part, this review has explained the environmentally benign products and processes that constitute the essence of green technology. In this part, we will conclude the review by focusing on three cardinal areas bearing on the challenge of green technology: Alternate Fuels, Green Buildings and Green Nanotechnology.
Green alternatives to fossil fuels
Energy is one of the grand challenges of the present century. Research focus worldwide has perceptibly shifted to renewable energy, and solar energy is unquestionably one of the most promising large-scale routes to this. Solar energy can be transformed into electricity through photovoltaic cells or solar power plants.
Presently, biocatalysis using genetically engineered fungal and bacterial microorganisms remains the most cost-effective pathway for obtaining biofuels from biomass. For example, genetically engineered fungi e.g. Trichoderma reesei is used to produce large volumes of cellulase, xylanase and hemicellulase enzymes. These enzymes then convert cellulosic biomass into fermentable sugars. As cellulose, in contrast to starchy feedstocks, contains large amounts of 5-carbon sugars, fermentation to cellulosic ethanol is best achieved using genetically engineered Escherichia coli bacterium.
Green buildings have been shown to save on average between 30 – 40 per cent energy and carbon emissions every year, and between 20 – 30 per cent potable water annually, when compared to the industry norm.
Green nanotechnology in environmental sustainability
We end this brief survey by citing three examples of how nanotechnology can specifically aid in environmental sustainability efforts from the aspects of pollution monitoring and possible remediation.
1.Real-time monitoring of air, water and soil quality has become a necessity in our present-day world to detect and quantify polluting sources. Advances in solid-state sensors and nano-fabrication technology have led to the development of many intelligent detection systems for this purpose. Examples include gas leak detectors, fire and toxic gas detectors, breath alcohol detectors, and the like. Nanosensors in the farm have prevented excessive use of fertilisers and pesticides, thereby reducing both environmental contamination and production cost. Recent innovations have seen the development of nanotin oxide and carbon nanotube (CNT) sensors to detect variant kinds of gas; CNT functionalised with palladium can detect hydrogen leaks in hydrogen fuel cells of electric cars.
2.An interesting serendipitous finding is that a sponge of entwined potassium manganese oxide nanowires can soak up to 20 times its weight in oil, while rejecting water with its water-repellent coating. The sponge can be reused after heating. The possibility that it can be produced in large quantities augurs well for its use to mop up and recover oil spillages in waterways.
3.An international team of researchers has advanced a futuristic solution to reducing toxic metal levels in wastewater and oceans through their development of nanobots. These nanobots have a graphene exterior to absorb the heavy metal, a nickel core that enables control of the nanobots' movement via a magnetic field, and an inner platinum coating that powers the bots forward via a chemical reaction with hydrogen peroxide. The nanobots can be reused for further sweeps.
Academician Professor Emeritus Dato' Dr V G Kumar Das has offered his views solely in his private capacity and they do not in any way represent the views of the Academy of Sciences Malaysia.