In a recent article from "Scientific American," author Vaclav Smil takes a look at major energy sources over the past 200 years, documenting that it takes upwards of 50 to 60 years for new sources to supplant existing energy forms. Taking into account the slow and arduous journey of new energy fuels, investors can take comfort in the immense possibility ahead of both natural gas, now comprising 25% of world energy demand, and renewable energy, which makes up 3.4% of global demand.

On the flip side, replaced fuels do not die quickly, as capital-intense infrastructure also needs to be replaced. This, too, leads to intriguing opportunities for long-term investors, especially if you dig in the bargain bin for incredible discounted coal producers. 

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This segment is from Tuesday's edition of "Digging for Value," in which sector analysts Joel South and Taylor Muckerman discuss energy and materials news with host Alison Southwick. The twice-weekly show can be viewed on Tuesdays and Thursdays. It can also be found on Twitter, along with our extended coverage of the energy and materials sectors @TMFEnergy.

Joel South has no position in any stocks mentioned. Taylor Muckerman has no position in any stocks mentioned. Taylor Muckerman has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.