Encyclopedia

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Carboxyl/Aminated Graphene

This is a type of graphene that has been functionalized with carboxylic acid on its surface.

Chemical Reduction of Graphene Oxide ( rGO )

This is a method for producing graphene. The rGO technique and its variants are based on the Brodie method, which was later developed into the Hummers method and subsequent variants. rGO employs graphite as a feedstock in which it is mixed with sulfuric acid to serve as an intercalating agent and potassium permanganate as an oxidant. This mixture is heated at high temperatures to produce graphene oxide (GO). At this point, the GO is reduced to graphene either chemically or thermally and with further steps of sonication, rinsing and dispersion.

Coal

What is coal?

Coal
Coal

Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. Coal is black or brownish-black, and has a composition that (including inherent moisture) consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time.

Coal is a combustible black or brownish-black sedimentary rock with a high amount of carbon and hydrocarbons. Coal is classified as a nonrenewable energy source because it takes millions of years to form. Coal contains the energy stored by plants that lived hundreds of millions of years ago in swampy forests.

Layers of dirt and rock covered the plants over millions of years. The resulting pressure and heat turned the plants into the substance we call coal.

Coal is found all over the world—including the United States—predominantly in places where prehistoric forests and marshes existed before being buried and compressed over millions of years. Some of the largest coal deposits are located in the Appalachian basin in the eastern U.S., the Illinois basin in the mid-continent region, and throughout numerous basins and coal fields in the western U.S. and Alaska.

What are the types of coal?

There are four major types (or “ranks”) of coal. Rank refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon-rich, and harder material. The four ranks are:

  • Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.
  • Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. Bituminous coal usually has a high heating (Btu) value and is used in electricity generation and steel making in the United States. Bituminous coal is blocky and appears shiny and smooth when you first see it, but look closer and you might see it has thin, alternating, shiny and dull layers.
  • Subbituminous: Subbituminous coal is black in color and is mainly dull (not shiny). Subbituminous coal has low-to-moderate heating values and is mainly used in electricity generation.
  • Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon. Lignite has a low heating value and a high moisture content and is mainly used in electricity generation.

The precursor to coal is peat. Peat is a soft, organic material consisting of partly decayed plant and mineral matter. When peat is placed under high pressure and heat, it undergoes physical and chemical changes (coalification) to become coal.

Coal is classified into four main types, or ranks: anthracite, bituminous, subbituminous, and lignite. The ranking depends on the types and amounts of carbon the coal contains and on the amount of heat energy the coal can produce. The rank of a coal deposit is determined by the amount of pressure and heat that acted on the plants over time.

Anthracite contains 86%–97% carbon and generally has the highest heating value of all ranks of coal. Anthracite accounted for less than 1% of the coal mined in the United States in 2022. All anthracite mines in the United States are in northeastern Pennsylvania. In the United States, anthracite is mainly used by the metals industry.

Bituminous coal contains 45%–86% carbon. Bituminous coal in the United States is between 100 million and 300 million years old. Bituminous coal is the most abundant rank of coal found in the United States, and it accounted for about 46% of total U.S. coal production in 2022. Bituminous coal is used to generate electricity and is an important fuel and raw material for making coking coal for the iron and steel industry. Bituminous coal was produced in at least 16 states in 2022, but five states accounted for about 78% of total bituminous production. The top five bituminous producing states and their percentage share of total U.S. bituminous production in 2022 were:

  • West Virginia—31%
  • Illinois—14%
  • Pennsylvania—14%
  • Kentucky—11%
  • Indiana—9%

Subbituminous coal typically contains 35%–45% carbon, and it has a lower heating value than bituminous coal. Most subbituminous coal in the United States is at least 100 million years old. In 2022, subbituminous coal accounted for about 46% of total U.S. coal production. The five subbituminous producing states and their percentage share of total U.S. subbituminous production in 2022 were:

  • Wyoming—89%
  • Montana—8%
  • New Mexico—2%
  • Colorado—2%
  • Alaska—<1%

Lignite contains 25%–35% carbon and has the lowest energy content of all coal ranks. Lignite coal deposits tend to be relatively young and were not subjected to extreme heat or pressure. Lignite is crumbly and has high moisture content, which contributes to its low heating value. In 2022, five states produced lignite, which accounted for 8% of total U.S. coal production. The five lignite-producing states and their percentage share of total U.S. lignite production in 2022 were:

  • North Dakota—56%
  • Texas—36%
  • Mississippi—7%
  • Louisiana—1%
  • Montana—<1%

The Great Plains Synfuels Plant in North Dakota converts lignite to synthetic natural gas that is sent in natural gas pipelines to consumers in the eastern United States.

What is coal used for?

Coal is primarily used as fuel to generate electric power in the United States. In coal-fired power plants, bituminous coal, subbituminous coal, or lignite is burned. The heat produced by the combustion of the coal is used to convert water into high-pressure steam, which drives a turbine, which produces electricity. In 2019, about 23 percent of all electricity in the United States was generated by coal-fired power plants, according to the U.S. Energy Information Administration.

Certain types of bituminous coal can also be used in making steel. Coal used for steel making needs to be high in carbon content and low in moisture, ash, sulfur, and phosphorous content. Coal that meets these specifications is known as metallurgical coal. Coal also has a myriad of other uses, including in cement production, carbon fibers and foams, medicines, tars, synthetic petroleum-based fuels, and home and commercial heating.

Which country has the most coal?

As of January 2020, the United States has the largest recoverable coal reserves with an estimated 252 billion short tons of coal remaining, according to the U.S. Energy Information Administration.

What is the biggest coal deposit in the United States?

The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which the USGS estimated to have 1.07 trillion short tons of in-place coal resources, 162 billion short tons of recoverable coal resources, and 25 billion short tons of economic coal resources (also called reserves) in 2013.

The coal in the Powder River Basin is subbituminous in rank. Large coal deposits can also be found in the Williston Basin in North Dakota and Montana (lignite in rank), the Appalachian Basin in Ohio, Pennsylvania, West Virginia, Virginia, and Alabama (bituminous in rank), and the Illinois Basin in Illinois and Indiana (bituminous in rank).

Global Coal Consumption

Global coal consumption has continued to rise, reaching new record levels in recent years.​

Global Coal Consumption Trends

  • 2023: Global coal demand reached an all-time high of approximately 8.70 billion tonnes, marking a 2.6% increase from the previous year.

  • 2024: Estimates indicate that coal consumption further increased to around 8.77 billion tonnes, setting another record.

 Regional Consumption Patterns

  • Asia: Over 80% of global coal consumption occurred in Asia in 2023. China and India were the primary contributors, with China’s consumption increasing by 4.9% and India’s by 8%. ​

  • Europe and the United States: Both regions experienced significant declines in coal consumption in 2023, with the European Union decreasing by 23% and the United States by 21%. ​

Future Outlook

The International Energy Agency (IEA) projects that global coal demand will plateau through 2027, remaining close to current record levels. Despite the expansion of renewable energy, coal continues to be a dominant energy source, particularly in developing economies.​

 

 

Conductive Ink

Conductive ink is an ink that results in a printed object capable of conducting electricity. Graphene based conductive inks have been around commercially since at least as early as 2009. Graphene based inks are generally significantly cheaper than silver and copper based inks.

CVD Graphene

Chemical vapour deposition, or CVD, is a method which can produce relatively high quality graphene, potentially on a large scale. The CVD process is reasonably straightforward, although some specialist equipment is necessary, and in order to create good quality graphene it is important to strictly adhere to guidelines set concerning gas volumes, pressure, temperature, and time duration.