inferior coal

例句：

1. 1. The company uses inferior coal to produce electricity.
   该公司使用劣质煤发电。
2. 2.Inferior coal is harder to process than standard coal.
   劣质煤比标准煤更难处理。
3. 3. The mine produces inferior coal for sale in the market.
   该矿生产的劣质煤在市场上销售。