Context: The Automotive Research Association of India (ARAI) was exploring the possibility of blending isobutanol with diesel. The move comes after the efforts to blend ethanol with diesel were unsuccessful.
Relevance of the Topic: Prelims: Isobutanol and its feasibility to blend with Diesel: Pros & Cons.
Biofuel blending in Petrol and Diesel is an important contributor to the government’s objective of scaling the net zero emission target by 2070.
Isobutanol and its feasibility to blend with Diesel
- Isobutanol is a higher molecular weight alcohol with inflammable properties. It is used as a solvent in several industries, including painting.
- It is produced from either thermochemical pathways (such as synthesis gas to mixed alcohols) or biochemical pathways (such as fermentation by specially designed microbes under sterile conditions).
Isobutanol Blending vs Ethanol Blending with Diesel
Studies suggest:
- Isobutanol has higher energy content as compared to ethanol and is more amenable to pipeline distribution.
- Isobutanol blends better with diesel compared to ethanol. There is no need to add any complement for efficiency.
- Less water absorption (less hygroscopic) compared to ethanol, thus it has lower corrosion risks.
- The flash point or the lowest temperature at which isobutanol yields a vapour igniting a momentary flash is higher than ethanol.
- A lower flash point was among the reasons that ethanol was not considered ideal for blending with diesel. Fuels with lower flash points are more volatile and entail a higher risk of catching fire.
- Proposed blending opens avenues for the surplus ethanol production sources to be diverted to produce isobutanol. Isobutanol can be produced from the same feedstock required to produce ethanol such as sugarcane syrup and molasses and grains etc.
The proposed blend would have an impact on reducing emissions and help with import substitution.
Associated Concerns:
- Isobutanol and diesel may have issues on miscibility (ability of two substances to mix to form a homogenous mixture) though it can be sorted out by mixing biodiesel to the blend. Biodiesel is the fuel manufactured from non-edible vegetable oils, used cooking oil and/or animal fat.
- Isobutanol has significantly lower cetane number (measure of combustion quality) as compared to diesel (the base fuel). This would reduce the blend’s overall cetane number. This raises concerns about diesel knock which can result in reduced power and potential damage to engines.
- An ideal combustion translates to rapid ignition and the fuel combusting completely to produce the necessary energy.
- ‘Knocking’ occurs when the fuel burns unevenly and/or prematurely in the vehicle’s fuel cylinder. However, cetane value can be restored through proper additives which would entail incremental costs.
The blending paradigm is still being studied and the pilot project would take about 18 months to complete. If successful, India would be the first country to have blended isobutanol with diesel.
Also Read: What are Biofuels?
Proper studies should be initiated encompassing varied vehicle classes and types. Phased blending targets with no more than 10% blending of isobutanol should be considered.