Water-biodiesel cocktail cuts greenhouse gas emissions

Subject : Environment

Context:

Using biodiesel to run truck engines can help reduce automotive greenhouse gas emissions, but the problem is that biodiesel releases more nitrogen oxide emissions than fossil diesel does. It further has a lower calorific value, which means you need more of it in your tank.

‘Micro-explosion’ phenomenon:

Scientists say mixing water with biodiesel addresses these problems.
Early vaporisation of water inside the fuel droplet increases its temperature, thus resulting in a phenomenon called ‘micro-explosion’, which in turn results in small fuel fragments, thus improving air-fuel mixing and reducing soot formation.
One gets better engine performance, lower emissions and less soot.

Concerns in mixing water with biodiesel:

The water and Biodiesel can not mix together.
But the problem can be solved with the help of an emulsifier, which is usually one of the chemicals that are called surfactants.
Usually, a mixture of surfactants called Span80 and Tween80 is used for this purpose.
But Span80-Tween80 is for diesel and needs a different concoction for biodiesel.
The stability of the emulsifier is critical because one can’t afford to have water separate from the oil, which would bring its own problems such as corrosion.

Solution:

A cocktail of Span80-Tween80 and two novel surfactants, polyglycerol poly ricinoleate (PGPR) and raw Karanja oil (RKO).
- PGPR is a commercially available low-cost food ingredient. RKO is a tree product. The novel surfactant is, therefore, a viable one.
The challenge is to find the optimum mix of water and biodiesel, with the surfactant thrown in.
More water means reduced tailpipe emissions, but also lower heat content of the fuel.
Researchers found that the optimum water concentration is 18 per cent, which reduced nitrogen oxide by 40 per cent,smoke by 52 per cent and carbon monoxide by 69 per cent.

Karanja tree (Pongamia pinnata):

Pongamia pinnata — better known in the subcontinent by names like Indian beech, karum tree, mullikulam tree, pongam and pongam oil tree — has attracted the attention of global investors and companies that have committed to net-zero emissions.
Pongamia pinnata has multiple applications: From land remediation and carbon sequestration to socioeconomic benefits’like afforestation.
The seeds are a good source of (non-edible) oil. Pongamia seeds give out an oil that is yellowish-orange to brown and can be used to produce biodiesel through trans-esterification.