The operative phrase that needs a definition is "near future'. If by that you mean in the next 5 years the answer is No. Can it supplement and pave the way to a fossil fuel free future? Yes, of course but not any time soon. Separately the "best" for economic, social and environmental is a very complicated answer too. There is also a matter of what is considered high quality fuel- is reliability an issue also, predictability, where is energy storage in the equation and what about micro grids? Can you ignore the CO2 emissions from the manufacture of solar panels or a utility-scale wind turbine and only count the non-generation related benefits? I don't think so but that's also not a reason not to figure these questions out and lead the way.

I don't think Renewable Energy systems will ever be able to be a complete substitute to the use of fossil fuel. Fossil Fuels sources like Natural Gas are virtually infinite in supply and is readily available in addition to being a fuel source that burns clean. I believe Hydroelectric power plants are the best bang for the buck in power generation. The first costs are substantial but the payback is fairly short due to the amount of electrical power that can be generated. The environmental impact is a concern with the flooding of a valley and other terrain in which wildlife lives but their "forced" relocation would be gradual where they could easily adapt to another nearby location. The social impact would be very positive with new locations for boating, swimming and fishing. This assumes of course that we continue the process of moving to electric power and away from fossil fuel as an energy source.

Fossil fuel is sure to be substitute in the near future. Regarding which renewable energy is the best depends on a few factors. First of all, the geographical influence. Solar energy would be one of the best choice for certain countries which have substantial amount of sun exposure all year long such as those in the tropics. However, some countries which has vast field and strong wind could harvest the wind energy while some which have coast line could harvest the ocean current as a source of alternative energy. Second, it depend on what resource the country have. For instance, Brazil is focusing in converting sugar cane as a source of bio-fuel due to the reason that the country is rich in sugar cane production, while Mexico is studying the possibility of using algae as a potential source of clean energy!

Renewable energy is already starting to substitute for fossil-based fuels and chemicals. Ethanol blended into gasoline comes from bio-based corn starch...AND...is starting to be made from lignocellulosic resources, wood and waste products from agriculture.

Solar and wind, while perhaps not "technically" renewable, are certainly low carbon alternatives to fossil fuel. There are technical challenges around storage of this energy source. These are already being addressed through improvements in battery technology. The game changer for wind/solar will likely come through conversion of this energy into a carrier like hydrogen. Being energy dense and transportable, like natural gas, hydrogen will likely become a major low carbon fuel for transportation.

At the moment, the only fuel-related technology that actually reduces atmospheric carbon is renewable fuels based on conversion of plants into fuels. The best known examples are ethanol, biodiesel and renewable (or green) diesel.

Solar and wind do not reduce atmospheric carbon.

Atmospheric carbon is captured by plants, trees, algae, seaweed, etc. The conversion of these bio-based feedstocks is, at the moment, the best way to reduce atmospheric carbon in relation to the renewable vs fossil issue.

I don't think that it could be completely substituted in the near 10 years period but there is a potential in perhaps 50 o 100 years. This is due to the reason that there are many under developed countries are still heavily dependent on fossil fuel to operate in a massive scale. Not to mention, the lack of technological support from developed countries.

There's no single answer. We must use all sustainable alternative energy sources in order to reduce the use of fossil fuels.