The question with plant based fuels is where do you grow them?
We have 6bn people on earth, and another million joining us every 5 days. There'll be 10bn by the middle of the century. To feed these people more wild land will go under the plough. If we were to try to supply fuel for hundreds of millions of vehicles too, we would literally run out of land.
George Monbiot's covered it in an accessible, concise yet authoritativve and referenced way:
"The most productive oil crop which can be grown in this country is rape. The average yield is between 3 and 3.5 tonnes per hectare. One tonne of rapeseed produces 415 kilos of biodiesel. So every hectare of arable land could provide 1.45 tonnes of transport fuel.
To run our cars and buses and lorries on biodiesel, in other words, would require 25.9m hectares. There are 5.7m in the United Kingdom. Switching to green fuels requires four and half times our arable area. Even the EU’s more modest target of 20% by 2020 would consume almost all our cropland."
http://www.monbiot.com/archives/2004/11/23/feeding-cars-not-people/
So we go to more productive plants that grow in hotter regions with sufficient rainfall; ethanol from sugar, or palm oil. These mean great deforestation in Brazil for the former, and Malaysia, Indonesia and Pacific islands.
I fear that we will make fuel oil the next great cash crop, and poor nations will go hungry while we continue to drive round expending the energy it takes to carry a ton of metal with us wherever we go.
Monbiot again:
"In September, Friends of the Earth published a report about the impacts of palm oil production. “Between 1985 and 2000,” it found, “the development of oil-palm plantations was responsible for an estimated 87 per cent of deforestation in Malaysia”. In Sumatra and Borneo, some 4 million hectares of forest has been converted to palm farms. Now a further 6 million hectares is scheduled for clearance in Malaysia, and 16.5m in Indonesia.
Almost all the remaining forest is at risk. Even the famous Tanjung Puting National Park in Kalimantan is being ripped apart by oil planters. The orang-utan is likely to become extinct in the wild. Sumatran rhinos, tigers, gibbons, tapirs, proboscis monkeys and thousands of other species could go the same way. Thousands of indigenous people have been evicted from their lands, and some 500 Indonesians have been tortured when they tried to resist. The forest fires which every so often smother the region in smog are mostly started by the palm growers. The entire region is being turned into a gigantic vegetable oil field.
Before oil palms, which are small and scrubby, are planted, vast forest trees, containing a much greater store of carbon, must be felled and burnt. Having used up the drier lands, the plantations are now moving into the swamp forests, which grow on peat. When they’ve cut the trees, the planters drain the ground. As the peat dries it oxidises, releasing even more carbon dioxide than the trees. In terms of its impact on both the local and global environments, palm biodiesel is more destructive than crude oil from Nigeria."
http://www.monbiot.com/archives/2005/12/06/worse-than-fossil-fuel/
The link you give talks of using plant fuels (problems as already described), fossil fuels (problems I don't need to mention), or hydrogen.
Hydrogen is currently mostly derived from natural gas; it's another fossil fuel. It is possible to extract it from sustainable sources like water, but it takes a tremendous quantity of energy to do so, far more than you get from burning the resulting hydrogen. And that's before you deal with the power needed to compress and distribute it.
It's rather like having a battery-making machine that needs two batteries as power for every one it produces.
Finding more efficient uses of fuel (such as hybroids) or ways to use avaialble sources such as waste vegetable oil are laudable and buy us some time to power down a bit more gently. But that has to be their aim. There is no way that we can continue our high-travel lifestyles on anything other than fossil fuels. We have to wean ourselves off them.
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