The given line graph demonstrates a comprehensive picture of renewable energy usage, including some main sources, spanning from 1949 to 2008.
Overall, the quantity of consumption witnesses a sharp increase over the period. Another striking feature is that hydroelectric power and wood were used from the first year while biofuels and wind were just consumed in the late 20th century.
Going into details, the total consumption and hydroelectric power shared a quite similar trend. In the first 25 years, they both rose approximately 45%. Then, despite a slight drop, they kept growing to reach a peak where the total usage hit 7 quadrillion btu and 3 quadrillion btu for hydropower in 1995. After that, although they decreased significantly in 2000, a bound back was made by them in the last year when the total consumption hit 7 quadrillion btu again and over 2 quadrillion for hydropower. Meanwhile, the wood remained steady despite some fluctuations during the span.
As for the remaining group, the two eco-friendly power sources were consumed in 1980. In the next 20 years, the biofuels experienced an unremarkable increase from 0 to 0.3 quadrillion btu while the wind maintained a steady level. However, from 2000 to 2008, the biofuels grew dramatically to hit over 1 quadrillion btu compared to 0.5 quadrillion btu of wind power consumption.