Last time I posted a story about the Trifuel Lotus ExigeI found myself being accused of acting like some kind of motor industry propagandist for bio-fuels.

But, after talking through some of the comments I fielded with Lotus, I’ve come back to have another go at setting the record straight.

Methanol certainly isn’t a perfect fuel – but it is a viable CO2-neutral, non-fossil source of power. Short of shifting the entire motoring population to battery power, or waiting for the hydrogen economy to get started, it’s as good an alternative as any at present.

Lotus does accept there is a drawback with methanol’s more limited capacity to store energy. Even adjusting for its higher density than petrol, which is not the same, methanol can only store approximately 50% of the energy in a given tank volume than petrol. Therefore, if the use of a fossil fuel is not possible, Lotus reckons that society may need to accept the more frequent refuelling of vehicles.

Lotus also reckons that criticism of the safety of methanol can easily be countered, saying that the Environmental Protection Agency in the US has analysed methanol in some detail. Their modelling shows that if the US moved from gasoline to methanol as the primary fuel, then deaths, injuries and property damage would fall by 90-95 per cent This is because the flammability index of methanol is about the same as diesel, and if lit, a methanol fire will only radiate heat at the rate of 11 per cent that of gasoline.

So if methanol can be made safe, how efficient is it as a fuel? Here are some facts – rather than conjecture – from Lotus: methanol (and ethanol) both give better performance than gasoline – their octane ratings are considerably higher (so more boost and compression can be used), their latent heat of vaporization is higher (meaning they cool the air and so allow more charge mass to flow through the engine), a given mass of fuel and air contains more energy, they reject less heat to the engine structure during combustion and their flame speed is higher.

All of which leads Lotus to conclude that synthetic methanol is the closest easily-renewable fuel to what we have now and as such demands the smallest change to a fully renewable future.

And I wouldn’t disagree. Equally, I wouldn’t underestimate the scale of the conversion task either. But it’s a smaller task than converting the global car fleet to fuel cell vehicles.