1. Energy needs
2. Material needs
The energy needs argument is somewhat comical and illustrates perfectly the lack of proper education and access to information that shows, without question, that the global combination of solar, space based solar, wind, wave, tidal, geothermal and fuel cell technologies are fully capable of supplying clean energy for the entire global population (such that they all have high standards of living) for the rest our existence on this planet, especially if we seriously do all we can to utilize energy efficiently and smartly, and not just give it lip service. For example, ensuring every building has some level of energy creation for itself (photovoltaic paint, solar panel tiles, built in wind generators, fuel cell systems, etc). This doesn't have to mean that every building is off the grid, but it can mean that some buildings are sources when at off-peak use, or less of a sink when they are running full tilt.
Now let's look at materials. Plastic is a huge argument by many to justify the need for fossil fuels like oil. Well step back and behold the power of innovation and science, because we are on the verge of replacing that idea completely...
The article above, in Popular Mechanics, covers this, and I want to make note of a few specific comments in the article that one should consider:
"The myriad companies running at algal biofuels today, for example, must first find and cultivate a precise strain of algae from among thousands, harvest and dry the stuff, and then somehow extract oil from the plant on a cost-competitive basis with now very cheap crude."
"But, like his comrades in the algae-oil business, the trouble hasn't been so much the science, but the supply of algae to his lab."
So let me get this right, by all technical accounts we have the technology to do this on a large scale, but costs make it "difficult" to compete in the market. Oh 'money', how I love the freedom you give us for innovation and doing the right thing. How stupid are we that we let a man-made construct restrict us so much in a time when we are capable of greatness?