褐煤, also known as lignite, is a type of coal that is considered the lowest rank among coal varieties. It is characterized by its brownish color and high moisture content, which makes it less efficient as a fuel source compared to higher-grade coals like bituminous coal or anthracite. Due to its lower carbon content, it burns with a lower energy output. This type of coal is primarily used for electricity generation in power plants and for producing synthetic fuels. Its extraction and use can have environmental impacts, including greenhouse gas emissions and land degradation. However, it remains an important energy resource in regions where it is abundant, such as parts of Germany and the United States.