Safeguard of global environment and human health in this environment is more and more highlighted as huge stakes for mankind in energy-related issues. It is a key point for a sustainable development of our world.
The global warming issue is not the only one to be tackled in the coming years; internal and external air pollutions linked with fuel combustion are also on the spot either in developed countries or in developing ones.
To combat pollutions we may either act on the devices using fuels to absorb and treat pollutants or to remove potential pollutants from the fuel itself or to find a non-polluting fuel.
Both ways were and are explored on existing fuels which are generally multiple molecule fuels except natural gas.
For multiple molecule fuels, these two ways are complex, expensive and perhaps drive to a dead-end especially if we have to deal with some very small particles.
In the beginning of the nineties, some US companies and research centers looked for a safe molecule, easy to produce and with a clean combustion i.e. without emission of the main well-known pollutants.
Such a molecule would enable engine makers to simplify their combustion systems and then make savings.
The result of this "Envirolene" project was DME, for Di-Methyl Ether, the simplest ether.
By virtue of its chemical composition (CH3-O-CH3), DME has no direct carbon bonds giving it a property of no particulate matter (PM) (commonly referred to as "soot") emission from combustion.
Compared to other unique molecule fuel such as methanol, DME is non toxic and then used as aerosol propellant for personal usages such as spray for hair dressing or wart removers.
DME became spray propellant thanks also to its harmlessness to the ozone layer as it decomposes in the atmosphere.
Moreover, DME is as easy to handle as LPG and its calorific value per kg is close to coal, better than methanol, much better than hydrogen and less than LPG, Diesel or methane. Per liter, it is close to methanol, methane or propane and largely greater than hydrogen.
We will first insist on some of the environmental and health issues the world has to deal with.
Then, we will show the advantages of DME compared to other fuel in that respect.
Last, we will show that DME, as it may be produced from various sources, may be a good candidate as clean energy carrier in a sustainable development perspective before the possible advent of hydrogen, probably in the long term.
Global Environmental and Health issues:
In terms of environment, the world is facing two main issues:
On one hand, global warming and its impacts on the world economy.
On the other hand, the rapid decline of outdoor air quality in large cities with increasing traffic and the everlasting bad quality of indoor air in poor countries linked to the usage of coal or biomass for heating and cooking.
Human activity is now accepted as the main reason of this global warming through greenhouse gases (GHG) emissions mainly CO2. But some scientists have begun to recognize (see www.enviroliteracy.org) that "black carbon - a component of PM, as having the potential to cause changes in climate. Soot is comprised of microscopic particles released", "when burning fossil or biomass fuels. In most developed countries, diesel fuels are the main source of black carbon", mainly from trucks; "elsewhere, the main sources are from the burning of wood, animal dung, vegetable oil, and other biomass fuels. Soot absorbs sunlight and, therefore, heats the surrounding air, also reducing the amount of sunlight that reaches the ground, resulting in a cooler surface. The heated air can create an unstable atmosphere resulting in rising air, forming clouds and bringing rainfall to areas heavily concentrated with soot. The rising air is often balanced by an increase in sinking air in neighbouring regions, which tends to prevent cloud formation and rainfall. An example of this rising and sinking air can be found in southern and northern China. Southern China has experienced rising air forcing increased rainfall and flooding due to soot and other pollutants, while in northern China sinking air has increased the occurrence of dust storms and has resulted in droughts.