The use of fossil fuels significantly drove the progress of human civilizations. Now, a new study has shown the earliest systematic coal use for fuel may have taken place as early as about 3,600 years ago in northwestern China.
Although sporadic combustion of coal for fuel was reported in some prehistoric archaeological sites, the evidence of its systematic exploitation before 2,500 years ago remained lacking.
Archaeologists from Lanzhou University, Renmin University of China, and the Institute of Cultural Relics and Archaeology of Xinjiang Uygur Autonomous Region identified coal heaps, unburnt coal, coal ashes, and coal refuse at a site in Nilka County, Kazak Autonomous Prefecture of Ili in Xinjiang, extending that record approximately 1,000 years back.
The chemical analysis revealed that those ancient fuels were carbon-rich bituminous coal exploited from nearby outcropped coal seams, according to the study published in the journal Science Advances recently.
Those relics demonstrated that the coal users chose to use fuels of high quality on purpose, and their exploitations were systematic, said the researchers.
Also, the study revealed that the coal, stored orderly along houses and metallurgical sites, were used for multiple purposes.
Inhabitants living at the site more than 4,000 years ago were found to mainly use wood for fuel, and they changed to coal 3,600 to 2,900 years ago, according to the study.
The researchers said the adjustment of energy structure might be driven by the stress of surging energy demand and the vegetation deterioration at that time.
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