Sustainability can be defined as the ability to meet present needs without disturbing Nature’s equilibrium by a holistic approach while not compromising the ability of the future generation to continue to meet their needs. Holistic is “Characterized by the belief that the parts of something are intimately interconnected and explicable only by reference to the whole” (Wikipedia). Mathematically and scientifically any exponential growth or consumption will not be sustainable and such growth will eventually be curtailed by forces of Nature. Unfortunately current models of sustainability do not take a holistic approach but focus only on a continuous growth or expansion to meet the demands of the growing human population thus disturbing the Nature’s equilibrium. The holistic approach is essential because our world is interconnected and any isolated growth or development in one part of the world will affect the other part of the world. Such a growth is counter-productive to human civilization as a whole. At the same time Nature’s equilibrium is critical for the survival of humanity and science should take into account this critical issue while developing solutions to problems. Otherwise such a solution will not be sustainable in the long run.
Nature maintains a perfect equilibrium (dynamic equilibrium) while maintaining reversibility. Both are intricately linked. If the equilibrium is not maintained then it becomes an irreversible process and the entropy of such a system will only increase according to the second law of thermodynamics. The order will become disorder or lead to chaos. Moreover any human interference to nature’s irreversibility and equilibrium by human beings will need energy. Any energy generation process within the system will not be holistic and therefore will not be sustainable.
For example, reverse osmosis (RO) is a major industrial process now used to desalinate sea water/brackish water to potable water. This process is reversing the Nature’s osmotic process by applying a counter pressure over and above the osmotic pressure of the saline water using high pressure pump. This requires energy in the form of electrical energy or thermal energy in the case of distillation. When such energy is generated by burning fossil fuel then the entropy increases because combustion of fossil fuel is an irreversible process. It is clearly not sustainable.
Energy is directly connected with economic growth of the world, but Governments and industries failed to adopt a holistic approach while generating energy by simply focusing only on economic growth. The fossil fuel power generation has resulted in the accumulation of GHG in the atmosphere and in the ocean changing the climate. Power generation by nuclear plant (Fukushima) has spilled radiation into the ocean and has crossed the Pacific Ocean to shores of North America. These are irreversible changes. The human and economic costs from such pollution will easily dwarf the ‘the economic growth’ of the world. It is not holistic because the emissions caused by one country affects the whole world; then it becomes the right of an individual to object to such pollution and it is the obligation of the Governments, United Nations and the industries to protect people from such pollution. Right now all these agencies are helplessly watching the deteriorating situation because they do not have the solution or means to reverse the situation whether it is an advanced country or a poor country; we always measure growth only by income and not by the quality of air we breathe in or water we drink or the environment we live in.
The demand for energy and water are constantly increasing all over the world; and we are trying to meet these demands by expanding existing power plants or by setting up new plants. When we generate power using fossil fuel the heat energy is converted into electrical energy and the products of combustion are let out into the atmosphere in the form of CO2 and Oxides of Nitrogen. It is an irreversible process and we cannot recover back the fossil fuel already burnt. Similarly the electricity generated once used to do some useful work such as lighting or running a motor etc cannot be recovered back. The process of electricity generation as well as usage of electricity is irreversible. Similarly when it rains the water percolates into the ground dissolving all the minerals, sometimes excessively in some places making it unsuitable to drink or irrigate. This process can be reversed but it again requires energy.
Both the above processes are irreversible and thermodynamically they will increase the entropy of the system. Any energy generation process will have cost implications and therefore irreversibility and entropy are directly linked with economics. Fortunately renewable energy sources offer hope to humanity. Even though the entropy is increased due to its irreversible nature there is no depletion of energy (sun shines everyday). Only Nature can come to human rescue to our sustainability. Science and powerful economies cannot guarantee sustainability irrespective of the size of the budget. There is a myth that billions of dollars can reverse the irreversibility with no consequences.
It raises question on the very basis of science because science depends on “observation and reproducibility” as we know. The biggest question is: “Who is the Observer and what is observed”? When sages of the East such as Ramana Maharishi raises this question, the Science has clearly no answer and the world is blindly and inevitably following the West to the point of no return.
Renewability and sustainability are two critical factors that will decide the future course of the world. We have to learn from Nature how sun is able to sustain life on earth for millions of years without the slightest hitch. The sun provides light energy for the photosynthesis to generate Carbohydrate using carbon dioxide from the atmosphere and water. The green pigment in the leaves of the plant ‘Chlorophyll’ catalalyses the photosynthesis. The plant grows and serves as food for animals. After certain period both the plant and animal dies and becomes carbon. New plants and animals are produced and the cycle continues. The dead plant decays and serves as manure for the new plant. A sequence of combinations of atmosphere, photosynthesis, micronutrients in the soil, absorption of carbon dioxide from air and release of Oxygen into the atmosphere, food production, life sustainenace, death and decay play like a symphony in an orchestra. Microorganisms too play their role in this cycle.
It is obvious from the above process that life cycle is based on ‘Renewability’.The death and decay of the old plant gives way to the birth of new plant and new cycle. There is nothing static .It is a dynamic and cyclic process, where ‘Renewability’ is the key. Only with renewability the process can ‘sustain’. Without a cyclic nature, the process will end abruptly. In fact ‘renewability’ and ‘sustainability’ are closely linked.
When we try to develop a new source of energy it is absolutely critical that such a source is renewable and available directly from Nature. Sun is the prime source of such energy, though it is also available in other forms such as wind, wave, ocean thermal etc. Such renewability can come only from Nature because human life in intricately linked with Nature such as earth, sun and wind. Everything that happens in Nature is to support life on earth and not to destroy. This is a fundamental issue.
When we dig out Carbon from the earth that was deeply buried by Nature and burn them, we release Carbon dioxide as well as Oxide of Nirtogen.Though our primary interest is only heat, we also create by-products such as greenhouse gases that upset the natural equilibrium. Nature can make some adjustments in order to maintain equilibrium; but when this limit exceeds, the equilibrium is upset creating a new environment, which may be alien to human life. This is unsustainable. Nature does not burn organic matter indiscriminately to generate Carbon dioxide to promote photosynthesis. It judiciously and delicately uses atmospheric Carbon dioxide without the slightest disturbance to the equilibrium. Many chemical reactions are irreversible and can cause irreversible damages, similar to ‘radiation’ from a nuclear reaction.
Whatever we do in the name of science, we will have to face their consequences, if we fail to understand the process of Nature completely and thoroughly. Fossil fuel sources are limited and burning them away to meet our energy demands is neither prudent nor sustainable. Human greed has no limit. We live in a finite world with finite resources and there is no place for infinite greed and destruction. There is no solution in Science for human greed.
It is clear substituting fossil fuels with Hydrogen is not only efficient but also sustainable in the long run. While efforts are on to produce Hydrogen at a cost in par with Gasoline or less using various methods, sustainability is equally important. We have necessary technology to convert piped natural gas to Hydrogen to generate electricity on site to power our homes and fuel our cars using Fuelcell.But this will not be a sustainable solution because we can no longer depend on piped natural gas because its availability is limited; and it is also a potent greenhouse gas. The biogas or land fill gas has the same composition as that of a natural gas except the Methane content is lower than piped natural gas. The natural gas is produced by Nature and comes out along with number of impurities such as Carbon dioxide, moisture and Hydrogen sulfide etc.The impure natural gas is cleaned and purified to increase the Methane content up to 90%, before it is compressed and supplied to the customers. The gas is further purified so that it can be liquefied into LNF (liquefied natural gas) to be transported to long distances or exported to overseas.
When the natural gas is liquefied, the volume of gas is reduced about 600 times to its original volume, so that the energy density is increased substantially, to cut the cost of transportation. The LNG can be readily vaporized and used at any remote location, where there is no natural gas pipelines are in existence or in operation. Similarly Hydrogen too can be liquefied into liquid Hydrogen. Our current focus is to cut the cost of Hydrogen to the level of Gasoline or even less. Biogas and bio-organic materials are potential sources of Hydrogen and also they are sustianable.Our current production of wastes from industries business and domestic have increased substantially creating sustainability isues.These wastes are also major sources of greenhouse gases and also sources of many airborne diseses.They also cause depletion of valuable resources without a credible recycling mechanisms. For example, number of valuable materials including Gold, silver, platinum, Lead, Cadmium, Mercury and Lithium are thrown into municipal solid waste (MSW) and sewage. Major domestic wastes include food, paper, plastics and wood materials. Industrial wastes include many toxic chemicals including Mercury, Arsenic, tanning chemicals, photographic chemicals, toxic solvents and gases. The domestic and industrial effluents contain valuable materials such as potassium, Phosphorous and Nitrates. We get these valuable resources from Nature, convert them into useful products and then throw them away as a waste. These valuable materials remain as elements without any change irrespective of type of usages.Recyling waste materials and treatment of waste water and effluent is a very big business. Waste to wealth is a hot topic.
The waste materials both organic and inorganic are too valuable to be wasted for two simple reasons. First of all it pollutes our land, water and air; secondly we need fresh resources and these resources are limited while our needs are expanding exponentially. It is not an option but an absolute necessity to recycle them to support sustainability. For example, most of the countries do not have Phosphorous, a vital ingredient for plant growth and food production. Bulk of the Phosphorus and Nitrates are not recovered from municipal waste water and sewage plants. We simply discharge them into sea at far away distance while the public is in dark and EPA shows a blind eye to such activities. Toxic Methane gases are leaking from many land fill sites and some of these sites were even sold to gullible customers as potential housing sites. Many new residents in these locations find later that their houses have been built on abandoned landfill sites. They knew only when the tap water becomes highly inflammable when lighting with a match stick. The levels of Methane were above the threshold limit and these houses were not fit for living. We have to treat wastes because we can recover valuable nutrients and also generate energy without using fresh fossil fuels. It is a win situation for everybody involved in the business of ‘waste to wealth’.
These wastes have a potential to guarantee cheap and sustainable Hydrogen for the future. Biogas is a known technology that is generated from various municipal solid wastes and effluents. But current methods of biogas generation are not efficient and further cleaning and purifications are necessary. The low-grade methane 40-55% is not suitable for many industrial applications except for domestic heating. The biogas generated by anaerobic digestion has to be scrubbed free of Carbon dioxide and Hydrogen sulfide to get more than 90% Methane gas so that it can be used for power generation and even for steam reforming to Hydrogen generation. Fuel cell used for on site power generation and Fuel cell cars need high purity Hydrogen. Such Hydrogen is not possible without cleaning and purifying ‘ biogas’ much. Hydrogen generation from Biogas or from Bioethanol is a potential source of Hydrogen in the future.
Renewable energy is one of the fastest growing energy sources of our times. But still there are many obstacles to overcome, before it can substitute current methods of electricity generation using fossil fuels, or substitute petrol in cars. The main obstacle is, the intermittent and unpredictable nature of renewable energy sources, such as wind and solar. Wind blows only certain seasons of the year and then wind velocity fluctuates widely in a day. Similarly sun shines only certain hours in a day and the intensity of radiation varies widely in a day. The wind velocity and sun’s radiation intensity are critical components in designing a reliable energy system. It is an anomalous situation, when we need power, there is no sun or wind; when sun shines or wind blows, we may not need any power. How to overcome this anomaly? That is the key, in successfully deploying renewable energy technologies.
Currently we are using batteries to store the energy. When there is a wind with reasonable velocity or sunshine with reasonable radiation intensity, we can generate power and store them in batteries. The wind velocity should be above certain threshold limit, say such as, a least wind velocity of 3mts/sec for amount of hours, while designing a wind based energy system. The same principle applies to solar energy and we need certain minimum solar intensity and several hours. But in reality, we don’t get these minimum operating parameters, which make the design of a renewable system more complicated.
Batteries can accumulate these small energy generations by intermittent sources of wind and sun, and store them. But these batteries have certain life between 3-5 years and requires regular maintenance, replacements.They also have certain charging and discharging cycles and limitations. At the end of its life, it has to be disposed carefully because these batteries are made of lead and acid, which are toxic materials. Many companies are trying to introduce better technologies such as ‘flow batteries’. But experience shows that such batteries are confined to only smaller capacities. Large scale storage is expensive and sometimes it is not economically feasible. Lithium-ion batteries are more efficient than Lead-acid batteries, but they are more expensive so the renewable energy projects become expensive and cannot compete with conventional fossil fuels, in spite of higher tariffs offered by Government as incentives. Moreover the demand for Lithium-ion batteries will increase substantially in the future, as more and more Electric cars are produced. But lithium sources are limited and it is not sustainable.
The best option to develop renewable energy systems is to generate Hydrogen using renewable energy and store them, instead of storing them in batteries. We can use stored Hydrogen to generate power, or use as fuel for the car, as and when we need. There are no maintenance or disposal problems with Hydrogen storage, when comparing with batteries. Hydrogen generators (electrolyzers) can generate Hydrogen when the intermittent power flows from wind or sun. They can run from a range of capacities from 5 to 100% of rated capacity and they are more suitable for renewable energy sources. But there will be a loss of energy, because the amount of power required to generate Hydrogen, is more than the power generated from the resulting Hydrogen by a Fuelcell.The initial cost will be higher, but it will give operational flexibility with least maintenance, and even adoptable to remote sites. Technology is improving to cut the cost of fuel cells and electrolyzers so that Hydrogen based renewable energy will become a sustainable source of energy in the future. Hydrogen is the only solution that can solve both power generation and transportation problems the world is currently facing.