One feasible alternative to the hydrogen economy - what we now call the "Methanol Economy" - has been proposed and discussed to great extent in this book (Fig. 14.1). Methanol is a convenient, oxygenated liquid hydrocarbon that at present is prepared from fossil fuel-based syn gas. As discussed earlier, however, new methods are currently under development for its production by the direct oxida-tive conversion of still-existing large natural gas (methane) sources, or by the hy-drogenative conversion of exhausts of fossil fuel-burning power plants and other industrial plants, which are rich in CO2. Eventually, it will be possible chemically to recycle atmospheric CO2 itself via hydrogenative conversion to methanol. The required hydrogen will be obtained from water (an inexhaustible resource), using any energy source - atomic or renewable energy. In this way, extremely volatile hydrogen gas will be conveniently and safely stored by converting it, with CO2, into liquid methanol.
Methanol represents not only a convenient and safe means of storing energy but, when combined with easily derived dimethyl ether (DME), this pair of compounds represent excellent fuels in their own right. Methanol and DME can be blended with gasoline/diesel and used in internal combustion engines, as well as in electricity generators. Methanol is particularly efficient, when used in the
direct methanol fuel cell (DMFC) (see Chapter 11), where methanol is oxidized directly with air to CO2 and water while producing electricity. In addition to its many uses for diverse chemical products and materials, methanol can also be readily converted to ethylene and/or propylene (the MTO process), which then can be used to produce synthetic hydrocarbons and their products, that presently are obtained from oil and gas.
CH3OH-»- CH2=CH2and/or-» hydrocarbons
Although today, methanol is prepared exclusively from fossil fuel-based syn-gas, while natural gas remains available it would seem reasonable to convert it directly into methanol, without first going through the syn-gas stage. This developing technology would not only greatly simplify its production but also extend its availability.
Methanol can also be obtained from CO2 by catalytic reduction with hydrogen, or by electrochemical reduction in water. The emissions of fossil fuel-burning power plants and chemical plants contain high concentrations of readily isolable CO2. As these large amounts of CO2, when released, contribute greatly to global warming, it is now generally agreed that they must be captured and disposed of. Rather than simply sequestering them, however, their chemical recycling to methanol seems a most feasible approach. Water could provide the required hydrogen for converting CO2 to methanol using any energy source (alternatives include atomic, photochemical and even bacterial conversions). In the longer per spective, however, fossil fuel-derived excessive CO2 generation will not be problematic, as our non-renewable fossil fuels will last at most for some centuries. At the same time, the recycling of atmospheric CO2 itself via its reductive hydrogenation to methanol will offer an inexhaustible carbon source for fuels, synthetic hydrocarbons and their products.
As the CO2 content of the atmosphere is low (0.037%), new and efficient ways for the separation of CO2 are needed. Today, selective absorption and other separation methods are making significant advances to allow the separation of atmospheric CO2 from the air on a practical scale. Methanol produced efficiently on a large scale from atmospheric CO2 and hydrogen from water will therefore be able to replace oil and gas both as a convenient way to store energy, as a suitable fuel and chemical raw material for synthetic hydrocarbons and their varied products (including polymer and even proteins). Thus, the "Methanol Economy" will eventually liberate mankind from reliance on diminishing and non-renewable fossil fuels.
Nature itself recycles CO2 in the photosynthetic processes conducted by plants (using water and energy from the Sun). The subsequent formation of fossil fuels from plant life is however, a very slow process requiring hundred of millions of years (although rapid bacterial conversion is a possibility). Hence, in a way the "Methanol Economy" supplements and greatly accelerates Nature's own recycling processes.
Ultimately, the majority of our energy on Earth comes from the Sun. It is considered that the Sun will last for at least 4.5 billion years, during which time the possibilities for mankind to devise more efficient ways of harnessing its energy are limitless. Whilst we cannot even begin to imagine the advances that will be made by future generations, our present discussions have been limited to what might be achieved in the foreseeable future, based on our present and developing knowledge base.
Our conclusion for the future is optimistic. Humankind is an ingenious species which always seems to find ways of overcoming adversities and challenges. As history teaches us, however, humankind's reaction to significant major problems and challenges usually comes only when a crisis is already upon us. Many believe that the problem of our oil and gas reserves is not yet at the crisis stage, and that we do not yet need to unduly worry about them. Past pessimistic predictions concerning our diminishing fossil fuel resources have always turned out to be "false alarms", and this is substantially true considering the short time spans to which they were applied. However, with regard to the longer range, the outlook is different. We must face the fact that our Nature-given non-renewable fossil fuel resources are finite and diminishing, whilst worldwide both the population and consumption is growing. We need to find new solutions, if we wish to continue our lives at a comparable or even higher standard of living. We need to start developing new solutions now - while we still have the time and resources to do it in an orderly fashion.
As rightly argued, one way of extending our oil and gas reserves is their better and more economical use, conservation measures and the introduction of new ef ficient technologies, particularly in the transportation area where oil-based gasoline and diesel fuel continue to be used primarily. Fuel savings, together with more efficient vehicles (such as using hybrid propulsion systems combining internal combustion engines with onboard generated electricity driven electric motors) can reduce gasoline and diesel fuel use and extend their availability. Fuel cells based not only on hydrogen, but also directly on methanol (DMFC) can provide cars with great fuel efficiency. The wide use of hydrogen for energy storage and as a fuel (the so-called "hydrogen economy") - except perhaps for larger static installations - is considered less feasible, as volatile hydrogen gas is extremely difficult to handle. This would necessitate not only the development of an entirely new and expensive infrastructure but also the recognition and control of serious safety hazards.
The proposed "Methanol Economy" represents a feasible new approach which extends beyond the era of abundant and cheap oil and gas. We hope that this book will further raise interest in the study of such an economy, together with its development and applications. It is not suggested, however, that this is the only approach to be followed - or is even necessarily the most feasible in all aspects. Rather, mankind will need to rely on all possible solutions available. We believe however, that the "Methanol Economy" is feasible and warrants extensive further study, development and evaluation.
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