In this article we will discuss about:- 1. Constraints in Biofuel Production 2. Advantage of Biofuels 3. Status 4. Strategy 5. Production Processes.
Constraints in Biofuel Production:
Despite all bright aspects and potential of biofuel production, there are certain constraints in its production as mentioned below:
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i. Unorganized plantations/cultivation and collection/ processing of raw material
ii. Denatured ethanol is treated as a chemical and should not be controlled
iii. The future of biofuel programme depends on parity of ethanol pricing with that of petrol on ex-refinery basis
iv. The petrol prices vary with price of crude oil and ethanol prices vary with that of molasses and cane
v. The collection of raw material for bio-diesel production coincides with monsoon and too with little duration
vi. Absence of a reasonable negotiated price of bio-fuel valid for 4 to 5 years
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vii. Complicated procurement system of ethanol and bio-diesel, affecting regular supply to the oil depots
viii. Variable tax and duty structures on ethanol and bio-diesel from state to state
ix. Interference by the State Government in
a. Putting procedural restrictions on the industrial alcohol/ethanol/methanol and bio-diesel production, sale and distribution mean for blending with petrol and diesel
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b. Levying imports-excise, entry tax, export or import fee or any other kind of levy
c. Creating a transparent unambiguous and well defined mechanism against the possibility of evasion of excise duty and misuse or diversion of rectified spirit mean for ethanol blending in petrol
Advantage of Biofuels:
Apart from energy security, employment generation, economical gain, social security etc., the biofuels have enormous environmental benefits being superior in many aspects than conventional source of energy i.e. petrol and diesel.
Status of Biofuel Production from TBOs in India:
Constraints in Utilization of TBOs in India:
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The Government of India launched National Biofuel Mission in 2003, primarily with a view to explore the potential of biofuels as a cleaner source of energy and to partially offset the growing burden of crude oil import bills. There is need to explore the existing potential of more than 50 lakh metric tons of oilseeds of tree origin in the country.
The main advantage of tapping the existing potential of tree borne oilseeds is that no additional land and inputs are needed as in case of agriculture crops, but only the collection of seed and fruits from trees occurring in nature is required. There are some constraints, which restrict the seed collection between 15-20 per cent of the total exploitable potential.
Some of the important constraints are mentioned below:
i. Most of the oilseeds of tree origin except for sal, occur scattered both in forest as well as in non-forest areas.
ii. The collection period of most of the TBOs is short, about 4-6 weeks which precedes or even coincides the rainy season.
iii. The collections are not confined to areas near inhabitation and easily accessible.
iv. There are no storage facilities near to the collection points and no motorable roads to facilitate the transportation of seeds collected.
v. The primary seed collector usually does not get the remunerative price for the seeds collected, which discourage him/her to collect the seed from interior areas.
vi. In some cases during the same period, when these oilseeds have to be collected, the tribals have alternative opportunities like collection of tendu leaves, tamarind etc. which seems to be more remunerative.
vii. The task of collection of such oilseeds is quite complex and require all possible support of Government to enhance the collection. The Government’s role in creating infrastructure would be important to increase the procurement of seed.
viii. There are several interlinked and complicated market channels available for disposal of seed collected by tribals or other weaker sections of the society in different States. Prevalence of monopolistic market is a discouraging factor in some cases.
ix. In some areas, absence of any type of market channel leads to the products rotting without sale.
Strategy to Overcome Constraints in India:
To overcome the constraints in seed collection, marketing, augmentation of potential etc., the following strategies may be adopted:
i. Focus on increasing productivity.
ii. Encourage exploitation of large untapped potential of non-traditional vegetable oils from TBOs.
iii. Establishment of model seed procurement centers and sub-centers in potential districts of the States.
iv. Installation of pre-processing and processing facilities including oil expeller.
v. Establishment of elite nursery and compact model plantation.
vi. Technology development, refinement and value addition.
vii. Dissemination of technical know-how through awareness programmes namely trainings, field visits, study tour etc.
viii. Price support system to the primary seed collector and grower.
ix. Financing for establishment of related commercial activities.
x. Encourage sale of blended oils.
Biofuel Production Processes:
1. Methodology for Production of Bio-Methanol:
Recently, a new method of gasification by partial oxidation and production of bio- methanol from carbohydrate resources has been developed. This process enables any source of biomass to be used as a raw material for bio-methanol production. In this process, the biomass feedstock must be dried and crushed to powder.
When the crushed material are gasified at 900-1000°C with gasifying agent (steam and oxygen), all carbohydrates are transformed to hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2) and vapour (H2O). The mixture of gases is readily utilized for generating electricity. The mixture of gases is transformed by thermo-chemical reaction to bio-methanol under pressure (40-80 atm) with Cu or Zn-based catalyst.
CO + 2H2 ⇌ CH3OH + Q (Radiation of heat)
CO2 + 3H2 ⇌ CH3OH + H2O + Q (Radiation of heat)
2. Methodology for Production of Bio-Ethanol:
Ethanol is produced by fermentation of any material that contains sugars either in a free form as in the case of molasses or in the form of starch as in the case of grains. Chemically starch is a polymer of glucose. The main processes in ethanol production are enzyme digestion (to release sugars from stored starches), fermentation of the sugars, distillation and drying. The distillation process requires significant energy input for heat (thermal energy).
Molasses contains sucrose, which is easily fermented by yeast to produce alcohol. However, for alcohol production from grains, the starch present in the grain has to completely broken down to glucose by a combination of two enzymes, viz. a-amylase and amyloglucosidase, before it is fermented by yeast to produce ethanol. This additional step of starch hydrolysis and low cost of molasses as compared to grains makes alcohol produced from molasses cheaper by 25-30 per cent.
However, treatment of byproducts generated by the process of fermentation of molasses into alcohol is difficult leading to pollution of the environment. Typical yield of alcohol from molasses is 225 liters per ton. Considering molasses contains 45 per cent sugar, only 70-75 per cent of the sugars get fermented to alcohol and the remaining sugars go into spent wash.
On the other hand, in typical grain fermentation the alcohol yield is more than 360 liters per ton of grain, containing 60 per cent starch which corresponds to 85 per cent conversion of sugars to alcohol. Moreover, the remaining sugars/starch do not go into the effluent because the stillage is dried. The dried residue is called Distiller’s Dried Grain and Soluble (DDGS), which is an excellent ingredient for animal feed.
3. Methodology for Production of Bio Diesel
i. Transesterification:
Biodiesel is a methyl ester formed by a process called transesterification. The transesterification process is the reaction of a triglyceride (fat/oil) with an alcohol to form esters and glycerol. A triglyceride has a glycerine molecule as its base with three long chain fatty acids attached. The characteristics of the fat are determined by the nature of the fatty acids attached to the glycerine. The nature of the fatty acids can in turn affect the characteristics of the biodiesel.
During the esterification process, the triglyceride is reacted with alcohol in the presence of a catalyst, usually a strong alkaline like sodium hydroxide. The alcohol reacts with the fatty acids to form the mono-alkyl ester, or biodiesel and crude glycerol.
In most production methanol or ethanol is the alcohol used (methanol produces methyl esters, ethanol produces ethyl esters) and is base catalyzed by either potassium or sodium hydroxide. Potassium hydroxide has been found to be more suitable for the ethyl ester biodiesel production, either base can be used for the methyl ester.
Oil can be extracted from seeds of TBOs with a simple oil mill (as used for mustard seeds). The TBO oil is reacted with methanol in the presence of a catalyst to yield methyl esters and glycerol. Sodium hydroxide and potassium hydroxide are commonly used catalyst. The oil is heated at 65°C. Sodium hydroxide tablets are dissolved in methanol to make a solution.
The quantity of NaOH and methanol should be 2.5 and 10 per cent respectively, of the total quantity of TBO oil. After mixing this solution into hot TBO oil, the solution should be stirred for 5 to 7 minutes. Then this solution is kept undisturbed at least for four hours.
Glycerol being heavy will slowly settle down at the bottom and biodiesel can be easily separated from the top. To drain the impurities like sodium, 2-3 washings with water is given to oil. Water is added to the oil and after five minutes, the oil floating on surface is collected. This process is repeated and then finally oil is heated to evaporate the water and biodiesel is ready to use.
ii. Reaction Temperature:
Reaction is conducted close to the boiling point of methanol i.e. 60-70°C under atmospheric pressure. This requires removal of FFA from the oil by refining or pre-esterification.
iii. Ratio of Alcohol to Oil:
A molar ratio of 6:1 (Alcohol: Oil) is normally used in industrial process to obtain Methyl Ester higher than 98 per cent yield.
iv. Purity of Reactants:
About 67-84 per cent conversion takes place with crude vegetable oils whereas 94-97 per cent conversion takes place with refined vegetable oils.
v. Effects of Moisture and Free Fatty Acids (FFA):
For alkali catalysed transesterification, the glycerides and alcohol must be substantially anhydrous. The FFA content of the oil should be as low as below 0.5 per cent.
vi. Catalyst Type and Concentration:
KOH (potassium hydroxide) and NaOH (sodium hydroxide) are used in the range of 0.5-1 per cent by weight to yield 94-99 per cent conversion of vegetable oil into methyl esters.