I was studying how ethanol will benefit India, and many intresting facts came under my notice, I thought it will be benifitial to all VP members, so I am staring this new thered to discuss and understand it better.
Ethanol, also known as ethyl alcohol or drinking alcohol, is a combustible clear liquid. Ethanol shares similar properties to that of petrol, and as such has evolved into a fuel substitute and fuel additive. The amount of ethanol contained in a fuel is usually indicated by the letter E, combined with a number, which signifies its concentration. E10 for instance, is 10 percent alcohol and 90 percent petrol. E85, another common fuel, is 85 percent ethanol. E100 is pure ethanol.
How Ethanol is produced
Ethanol is made from a variety of biomass materials called feedstocks (the raw materials used to make a product). Ethanol is mainly produced from food grains and crops with high starch and sugar content as feedstocks for making ethanol such as corn, sorghum, barley, sugar cane, and sugar beets. Ethanol can also be made from grasses, trees, and agricultural and forestry residues such as corn cobs and stocks, rice straw, sawdust, and wood chips. Ethanol is made from these feedstocks in several ways.
Fermentation is the most common method for producing fuel ethanol
The most common ethanol production processes today use yeast to ferment the starch and sugars in corn, sugar cane, and sugar beets. The starch in it is fermented into sugar, which is then fermented into alcohol.
Sugar cane and sugar beets are the most common feedstocks used to make fuel ethanol. Because alcohol is made by fermenting sugar, sugar crops are the easiest ingredients to convert into alcohol.
Cellulosic ethanol is a large potential source of fuel ethanol
Ethanol can also be produced by breaking down cellulose in plant fibers. This cellulosic ethanol is considered an advanced biofuel and involves a more complicated and costly production process than fermentation. However, there are large potential non-food crop sources of cellulosic feedstocks. Trees, grasses, and agricultural residues are potential feedstocks for cellulosic ethanol production. Trees and grasses require less energy, fertilizers, and water to grow than grains do, and they can also be grown on lands that are not suitable for growing food crops. Scientists have developed fast-growing trees that grow to full size in 10 years. Many grasses can produce two harvests a year for many years without annual replanting. Despite the technical potential for cellulosic ethanol production, economical production has been difficult to achieve.
Octane value of Ethanol
The Octane Number affects the activation energy of the fuel. In simple terms, an increase in the octane number will make the fuel require a higher amount of energy before it starts to combust. So even if the side conditions like pressure, temperature are higher, the increased activation energy will make sure that the fuel will only catch fire because of the spark plug and not because of the surrounding conditions.
In India, the minimum octane rating for fuels as prescribed by Government through Bharat 3 to 6 emission norms is 91 Octane.
Octane value for pure petrol is around 85.
The octane rating of pure ethanol is 100. What’s interesting is that when ethanol is blended with petrol, it performs as if its octane rating is 113, making ethanol a very effective octane booster when used in petrol.
When we mix 10 percent 113 octane ethanol with 85 octane petrol it increases the octane two points to 87 octane. so the higher the ethanol content, the higher the octane. The octane rating for E15 (15% ethanol) is 88 octane, E20 (20% ethanol) is 91 and E85 (85% ethanol) is 108 octane.
Higher octane fuels are often required or recommended for engines that use a higher compression ratio and/or use supercharging or turbocharging to force more air into the engine. Increasing pressure in the cylinder allows an engine to extract more mechanical energy from a given air/fuel mixture but requires higher octane fuel to keep the mixture from pre-detonating. In these engines, high octane fuel will improve performance and fuel economy.
Energy Efficiency of Ethanol
To produce ethanol, we require lots of resources and energy. The majority of energy consumed during the production of ethanol comes from production of the crops, growing and harvesting of crops requires land, water, fertilisers, pesticides, etc. To produce fertilisers and pesticides also requires energy. Other than this cutting, cleaning, transportation, crushing, fermentation and all other processes requires energy.
There are many studies conducted on this to measure energy efficiency of ethanol, but I couldn’t find a clear answer on this, some studies say that is not at all efficient, some studies are saying it is too efficient and rating varies between 0.85 to 1.6.
Considering higher side of efficiency that is 1.6 and ethanol blend of 10% we can overall save mere 4% of fossil fuel, If we use 20% ethanol blend than we can save 8% of fossil fuel.
How much feedstock is required to produce ethanol?
Ethanol yield is directly proportional to the total starch content present in crops, below is an average expected yield of ethanol from different crops
1 ton of sugarcane – 80 L
1 ton of Wheat – 60 L
1 ton of Corn – 70 L
What is the annual production of different crops in India?
According to FOASTAT 2019 annual production of different agri crops in India are as follows-
Sugarcane – 4054 Lakh Tonnes
Wheat – 1036 Lakh Tonnes
Rice – 1776 Lakh Tonnes
Ethanol is nontoxic and biodegradable
Unlike fossil fuels, pure ethanol is nontoxic and biodegradable, and it quickly breaks down into harmless substances if spilled. Chemical denaturants are added to ethanol to make fuel ethanol, and many of these denaturants are toxic. Similar to petrol, ethanol is a highly flammable liquid and must be transported carefully.
These emissions are sometimes referred to as “indirect” and result from the emissions generated by the production of ethanol fuel, fossil fuels like petrol and diesel are used in trucks, tractors, and warehouses to produce the crops and during fermentation process.
When ethanol combusts, it releases primarily carbon dioxide and water vapor. Despite the fact that a litre of ethanol produces less carbon dioxide than petrol, it still produces greenhouse emissions like carbon dioxide. However, the combustion of ethanol is largely particulate-free, whereas petrol combustion forces many particles into the air. Since a litre of ethanol contains less energy than a litre of petrol, it can require more ethanol than petrol to travel similar distances, which can contribute to more greenhouse gas emissions.
Need for Land
Another debate about producing ethanol concerns the amount of land it takes away from food production. The challenge of growing enough crops to meet the demands of ethanol production is significant and, some say, insurmountable. According to some authorities, producing enough biofuels to enable their widespread adoption could mean converting most of the world’s remaining forests and open spaces to farmland—a sacrifice few people would be willing to make.
To replace 20% of petrol with ethanol, India will require approximately 1000 Cr Lit of ethanol annually. Which in turn requires 1250 Lakh tonnes of sugarcane, to produce 1250 Lakh tonnes of sugarcane will require 10 Lakh hectares of extra land.
Water ConsumptionThe field crops which are used in ethanol production requires more amount of water than other crops, which also increase burden on our existing sources of potable water, with ground water table going deeper day by day it may be more concern for overall ecology.
To produce 1 Lit of ethanol from sugarcane approximatly 2800 Lit of water is required.
Other long-term environmental effects include less bio-diversity and food scarcity, soil erosion etc.
Further studyA good book to study in depth on bio fuels-
Disclosure - I am not holding any positions in any ethanol, sugar or related company.