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Another traditional but still popular energy source is wood. Trees
burn reasonably well and can provide both heat and light. Some places
even burn them for electricity. Burning excessive amounts of wood
produces deforestation and pollution. Many societies over the
millenia of history have caused great harm to themselves by improper
management of their forest resources.
Candles (from animal sources) and oil lamps (originally from
vegetable oils) are another renewable source of energy that has
lighted homes since humans discovered fire.
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