Introduction
When I was first introduced to Organic Chemistry in my tenth standard, I was taught that alcohols can be used as fuels and that they are efficient enough to not only be widely used, but to also be produced for the purpose of trading by some countries (predominantly, Brazil). In India the main products used as fuel are diesel and petrol and therefore the purpose of my project is to determine the efficiency of the various alcohols through their heat of combustion and see how they fare against petrol and diesel. Also taken into consideration will be the availability, environment impact and ease of obtainment to validate which fuel is better for the economy.
Aim
To determine the productivity of various alcohols as fuels taking their enthalpy of combustion, efficiency, availability and environmental impact into consideration by conducting experiments and investigating these prerequisites/specifications.
Background Information and Research on the Fuels
Alcohols are organic compounds containing the functional group R-O-H. The functional R-O-H group determines the characteristic reactions of the compound. The general formula of alcohols is CnH2n+1OH, where n is a number. The first four aliphatic alcohols (methanol, ethanol, propan-1-ol, and butan-1-ol) are of interest as fuels because they can be synthesized chemically or biologically. Methanol is synthesised from the methane (marsh gas) released from nearly every biomass (including but not restricted to animal waste, dead and decaying living matter). It can also be produced by the gasification of organic materials to synthesis gas followed by conventional methanol synthesis. Recently, methanol fuel has been produced using renewable energy and carbon dioxide as a feedstock. Widespread production by this route has a proposed potential to offer methanol fuel at a low cost and with benefits to the environment. Methanol is far more difficult to ignite than gasoline and burns about 60% slower. A methanol fire releases energy at around 20% of the rate of a gasoline fire, resulting in a much cooler flame. This results in a much less dangerous fire that is easier to contain with proper protocols. Unlike gasoline fires, water is acceptable. These facts mean that, as a vehicle fuel, methanol has great safety advantages over gasoline. Post-accident environmental damage mitigation is facilitated by the fact that low-concentration methanol is biodegradable, of low toxicity, and non-persistent in the environment. Ethanol is a form of quasi-renewable energy that can be produced from agricultural feedstock. It can be made from very common crops such as hemp, sugarcane, potato, cassava and corn. There has been considerable debate about how useful bioethanol is in replacing gasoline. Concerns about its production and use relate to increased food prices due to the large amount of arable land required for crops. However, a brand of ethanol, cellulosic ethanol has been found to allay these problems. Cellulosic ethanol is ethanol (ethyl alcohol) produced from cellulose (the stringy fibre of a plant) rather than from the plant’s seeds or fruit. It is a biofuel produced from grasses, wood, algae, or other plants. The fibrous parts of the plants are mostly inedible to animals, including humans, except for ruminants (grazing, cud-chewing animals such as cows or sheep) thus solving the fuel vs. food debate. Growth of cellulose by plants is a mechanism that captures and stores solar energy chemically in nontoxic ways with resultant supplies that are easy to transport and store. Additionally, transport may be unneeded anyway, because grasses or trees can grow almost anywhere temperate. This is why commercially practical cellulosic ethanol is widely viewed as a next level of development for the biofuel industry that could reduce demand for oil and gas drilling and even nuclear power in ways that grain-based ethanol fuel alone may not.
It has also been found that cellulosic ethanol can produce a positive net energy output and help in having a positive economic impact. Propanol and butanol are considerably less toxic and less volatile but the fermentation processes to produce propanol and butanol from cellulose are fairly tricky to execute, the process stops at 7% of the fuel. For comparison, yeast dies when the ethanol content of its feedstock hits 14%. Fixing this will be helpful as Butanol has a higher energy density than ethanol, and because waste fibre left over from sugar crops used to make ethanol could be made into butanol, raising the alcohol yield of fuel crops without there being a need for more crops to be planted.