Which Indian Institute of Technology (IIT) has developed a "soil-to-soil" technology to manufacture cheaper, faster and pollution free biofuel from biomass?

Introduction / Context:
The search for clean and sustainable energy sources has led to intensive research into biofuels. Indian Institutes of Technology have played a key role in designing technologies that can convert agricultural and organic waste into useful fuel in an environmentally friendly way. One such innovation was described as a "soil-to-soil" technology, emphasising that the process begins with agricultural residues from soil and ends with by products that can safely return to the soil. This question asks which IIT developed this particular biofuel technology.

Given Data / Assumptions:

• We are talking about a "soil-to-soil" technology that produces biofuel.
• The technology is cheaper, quicker and pollution free compared to many existing methods.
• The options are IIT Kolkata, IIT Kharagpur, IIT Delhi and IIT Bombay.
• We must choose the IIT associated with this innovation.

Concept / Approach:
IIT Kharagpur has a strong record in agricultural engineering, biotechnology and rural development research. It has been specifically mentioned in news reports for developing a "soil-to-soil" technology for converting biomass into biofuel where the residues can be reused as soil conditioners. The other IITs also work on energy projects, but this particular phrase and concept have been prominently linked with IIT Kharagpur. Recognising that connection allows us to select the correct answer.

Step-by-Step Solution:
Step 1: Understand that the phrase "soil-to-soil" suggests a process starting with agricultural waste and returning safe materials to the soil at the end. Step 2: Recall which IIT has a strong emphasis on agricultural and rural technology; IIT Kharagpur fits this profile. Step 3: News on this innovation highlighted IIT Kharagpur scientists developing a method to convert organic waste into biofuel while minimising pollution. Step 4: Examine the other options. IIT Kolkata is not an official name; the institute in that region is IIT Kharagpur, located in West Bengal. Step 5: IIT Delhi and IIT Bombay are major institutes but were not associated with the specific "soil-to-soil" label. Step 6: Therefore, identify IIT Kharagpur as the correct choice.

Verification / Alternative check:
A useful cross check is to think of media coverage on innovative low cost clean energy solutions developed in Indian institutes. Articles discussing "soil-to-soil" technology specifically mention IIT Kharagpur's role in designing a system to create biofuel without leaving harmful residues. This alignment of phrase and institution supports the conclusion that IIT Kharagpur is the correct answer.

Why Other Options Are Wrong:
IIT, Kolkata: There is no IIT officially named IIT Kolkata; this option is misleading and likely included as a distractor.
IIT, Delhi: While IIT Delhi conducts energy research, it is not the institute highlighted in connection with the "soil-to-soil" technology referenced in the question.
IIT, Bombay: Similarly, IIT Bombay is a leading institute but not linked to this particular phrase and biofuel innovation.

Common Pitfalls:
Some candidates may be confused by the mention of Kolkata and select it due to familiarity with the city, not realising that IIT Kharagpur is the correct institution in West Bengal. Others might assume that any major IIT such as IIT Delhi or IIT Bombay must be responsible. It is important to pay attention to subtle clues such as unique phrases like "soil-to-soil" and recall the specific institute associated with them.

Final Answer:
The "soil-to-soil" biofuel technology was developed by IIT, Kharagpur.