[marcus0x62]

The usual theory here is that fuels made from plants are carbon neutral in that while the fuel produces CO2 when burned, the plant it was made from consumed an equivalent amount of CO2 while alive. (Which, even if true ignores particulate and NOX emissions. See also: green washing.)

[jeroenhd]

This also ignores a dire problem humanity has created for itself: massive amounts of arable land wasted on fuel crops rather than food for people.

It's similar to the farming industry producing incredible amounts of food just to feed cattle rather than to feed people. Not all crops grow on all land, of course, but as long as there are large scale famines in the world, I think it's immoral to dedicate so much land towards inedible foodstuffs.

We're already burning forests under the guise of "renewable fuels" that assume we've assured that the forests are allowed grow back the next 100 years even when biofuels are no longer profitable.

There are good reasons to rid ourselves from fossil fuels where we can, not just because of global warming but also because of political reasons (the oil states getting away with literal murder and a blind eye being turned towards their funding of what would become 9/11, for one). However, I fear that these plant based "alternatives" will be quickly bought up by the oil industry, touted as the future of green energy, and used to postpone greener alternatives to the internal combustion engine yet another decade.

[elif]

"made from plants" will need a citation.

The Porsche/Exxon syn fuel uses natural gas as it's feedstock, for instance.

I'm pretty sure the Mazda pr guy was just smart enough to omit that detail, not that they are hiding it's magical eco friendly origins.

[djmips]

This other press release from Mazda's fuel supplier doubles down on the agricultural waste talking point. In this case 'straw' was used to create ethanol which was the feedstock.

https://coryton.com/lab/articles/the-opportunity-for-sustain...

[kremi]

Some more drawbacks : 1. the plants are usually grown using fertilizers that are made out of, ironically, fossil fuels. 2. the process of turning the plant into fuel might also create emissions that need to be taken into account.

[pfdietz]

Fertilizers can also be made without fossil fuels.

One really has to distinguish between CO2 that would be emitted by the process in the current fossil fuel economy, vs. CO2 emitted when the world is off fossil fuels. In the latter, where do the carbon atoms come from if not from the biomass, and hence from the air?