These include increasing difficulties of mining far below the ground in the key producing nation of South Africa, as well as labor issues that mean higher costs and the threat of supply disruptions due to strikes.

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At that time, a small quantity of US shale oil was being unlocked by mining the rock out of the ground, trucking it to centralized plants, and heating the rock to release the hydrocarbons.

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The threat of a power shortage in the country, and thus a curtailment of electricity needed for mining that tends to occur far under the ground, has been an ongoing issue for a few years now.

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