There are a number of adverse health and environmental effects of coal burning especially in power stations, and of coal mining. These effects include:

• Coal-fired power plants shorten nearly 24,000 lives a year in the United States, including 2,800 from lung cancer
• Generation of hundreds of millions of tons of waste products, including fly ash, bottom ash, flue gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals
• Acid rain from high sulfur coal
• Interference with groundwater and water table levels
• Contamination of land and waterways and destruction of homes from fly ash spills such as Kingston Fossil Plant coal fly ash slurry spill
• Impact of water use on flows of rivers and consequential impact on other land-uses
• Dust nuisance
• Subsidence above tunnels, sometimes damaging infrastructure
• Uncontrollable underground fires which may burn for decades or centuries.
• Coal-fired power plants without effective fly ash capture are one of the largest sources of human-caused background radiation exposure
• Coal-fired power plants emit mercury, selenium, and arsenic which are harmful to human health and the environment
• Release of carbon dioxide, a greenhouse gas, which causes climate change and global warming according to the IPCC and the EPA. Coal is the largest contributor to the human-made increase of CO₂ in the air

Refined coal is the product of the application of a coal upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals and raising their calorific values. Coal refining or upgrading technologies are typically pre-combustion treatments and/or processes that alter the characteristics of a coal before it is burned. The goals of pre-combustion coal upgrading technologies are to increase efficiency and reduce emissions when coal is burned. Depending on the situation, pre-combustion technology can be used in place of or as a supplement to post-combustion technologies to control emissions from coal-fueled boilers. A primary benefit of refined coal is the capacity to reduce the net volume of carbon emissions that is currently emitted from power generators and would reduce the amount of emissions that is proposed to be managed via emerging carbon sequestration methodologies. Refined coal technologies have primarily been developed in the United States, several similar technologies have been researched, developed and tested in Victoria, Australia, including the Densified coal technology (Coldry Process) developed to alter the chemical bonds of brown coal to create a product that is cleaner, stable (not prone to spontaneous combustion), exportable and of sufficiently high calorific value to be a black coal equivalent.

Commercial Development of Refined Coal

United States

Evergreen Energy constructed a full-scale coal refinery near Gillette, Wyoming that began operation in late 2005. Designed originally to be a commercial plant, the facility encountered design and operational problems. Evergreen idled the facility in March 2008 and instead used the plant as a process development platform with its engineering, construction and procurement contractor Bechtel Power Corporation.

Evergreen is now seeking to construct a coal refinery using the improved Bechtel design at locations in the Midwestern United States and in Asia.

Australia

Calleja Group constructed a full-scale 16,000 tonne per annum pilot demonstration plant at JBD Business Park at Maddingley Mine near Bacchus Marsh, Victoria that began operation in early 2004. From 2005 ECT Limited upgraded the facility, added a water recovery process with Victorian Government funding in 2007 and operated the plant as a process development platform with its engineering partner ARUP. In 2009 ECT Limited secured and agreement with Thang Long Investment Company (Tincom) of Vietnam to finalise commercial feasibility ahead of construction of a 2 million tonne pa export plant by 2014 and 20 million tonne pa export by 2020. ECT Limited is using the ARUP improved design to secure technology licensing agreements with brown coal suppliers in China, India, Indonesia, Poland, Greece and Russia.

Coal liquefaction is the process of producing synthetic liquid fuels from coal.

The Coal liquefaction processes are classified as direct conversion to liquids processes and indirect conversion to liquids processeses. Direct processes are carbonization and hydrogenation.

Pyrolysis and carbonization processes

There are a number of carbonization processes. The carbonization conversion occurs through pyrolysis or destructive distillation, and it produces condensable coal tar, oil and water vapor, non-condensable synthetic gas, and a solid residue-char. The condensed coal tar and oil are then further processed by hydrogenation to remove sulfur and nitrogen species, after which they are processed into fuels.

The typical example of carbonization is the Karrick process. The process was invented by Lewis Cass Karrick in the 1920s. The Karrick process is a low-temperature carbonization process, where coal is heated at 680 °F (360 °C) to 1,380 °F (750 °C) in the absence of air. These temperatures optimize the production of coal tars richer in lighter hydrocarbons than normal coal tar. However, the produced liquids are mostly a by-product and the main product is semi-coke, a solid and smokeless fuel.

The COED Process, developed by FMC Corporation, uses a fluidized bed for processing, in combination with increasing temperature, through four stages of pyrolysis. Heat is transferred by hot gases produced by combustion of part of the produced char. A modification of this process, the COGAS Process, involves the addition of gasification of char. The TOSCOAL Process, an analogue to the TOSCO II oil shale retorting process and Lurgi-Ruhrgas process, which is also used for the shale oil extraction, uses hot recycled solids for the heat transfer.

Liquid yields of pyrolysis and Karrick processes are generally low for practical use for synthetic liquid fuel production. Furthermore, the resulting liquids are of low quality and require further treatment before they can be used as motor fuels. In summary, there is little possibility that this process will yield economically viable volumes of liquid fuel.

Hydrogenation processes

One of the main methods of direct conversion of coal to liquids by hydrogenation process is the Bergius process. The Bergius process was developed by Friedrich Bergius in 1913. In this process, dry coal is mixed with heavy oil recycled from the process. Catalyst is typically added to the mixture. The reaction occurs at between 400 °C (752 °F) to 5,000 °C (9,030 °F) and 20 to 70 MPa hydrogen pressure. The reaction can be summarized as follows:

n C + (n + 1) H₂ → C_nH_{2 n + 2}

After World War I several plants were built in Germany; these plants were extensively used during World War II to supply Germany with fuel and lubricants. The Kohleoel Process, developed in Germany by Ruhrkohle and VEBA, was used in the demonstration plant with the capacity of 200 ton of lignite per day, built in Bottrop, Germany. This plant operated from 1981 to 1987. In this process, coal is mixed with a recycle solvent and iron catalyst. After preheating and pressurizing, H₂ is added. The process takes place in a tubular reactor at the pressure of 300 bar and at the temperature of 470 °C (880 °F). This process was also explored by SASOL in South Africa.

In 1970-1980s, Japanese companies Nippon Kokan, Sumitomo Metal Industries and Mitsubishi Heavy Industries developed the NEDOL process. In this process, coal is mixed with a recycled solvent and a synthetic iron-based catalyst; after preheating H₂ is added. The reaction takes place in a tubular reactor at temperature between 430 °C (810 °F) and 465 °C (870 °F) at the pressure 150-200 bar. The produced oil has low quality and requires intensive upgrading. H-Coal process, developed by Hydrocarbon Research, Inc., in 1963, mixes pulverized coal with recycled liquids, hydrogen and catalyst in the ebullated bed reactor. Advantages of this process are that dissolution and oil upgrading are taking place in the single reactor, products have high H/C ratio, and a fast reaction time, while the main disadvantages are high gas yield (this is basically a thermal cracking process), high hydrogen consumption, and limitation of oil usage only as a boiler oil because of impurities.

The SRC-I and SRC-II (Solvent Refined Coal) processes developed by Gulf Oil and implemented as pilot plants in the United States in the 1960s and 1970s. The Nuclear Utility Services Corporation developed hydrogenation process which was patented by Wilburn C. Schroeder in 1976. The process involved dried, pulverized coal mixed with roughly 1wt% molybdenum catalysts. Hydrogenation occurred by use of high temperature and pressure synthesis gas produced in a separate gasifier. The process ultimately yielded a synthetic crude product, Naphtha, a limited amount of C₃/C₄ gas, light-medium weight liquids (C₅-C₁₀) suitable for use as fuels, small amounts of NH₃ and significant amounts of CO₂. Other single-stage hydrogenation processes are the Exxon Donor Solvent Process, the Imhausen High-pressure Process, and the Conoco Zinc Chloride Process.

There is also a number of two-stage direct liquefaction processes; however, after 1980s only the Catalytic Two-stage Liquefaction Process, modified from the H-Coal Process; the Liquid Solvent Extraction Process by British Coal; and the Brown Coal Liquefaction Process of Japan have been developed.

Shenhua, the Chinese coal miner, decided in 2002 to build a direct liquefaction plant in Inner Mongolia, with barrel capacity of 20 thousand barrels per day (3.2×10³ m³/d). First tests were implemented at the end of 2008. A second and longer test campaign was started in October 2009.

Chevron Corporation developed a process invented by Joel W. Rosenthal called the Chevron Coal Liquefaction Process (CCLP). It is unique due the close-coupling of the non-catalytic dissolver and the catalytic hydroprocessing unit. The oil produced had properties that were unique when compared to other coal oils; it was lighter and had far fewer heteroatom impurities. The process was scaled-up to the 6 ton per day level, but not proven commercially.

Indirect conversion processes

The main indirect process is the Fischer-Tropsch process. In this process, coal is first gasified to make syngas (a balanced purified mixture of CO and H₂ gas). Next, Fischer-Tropsch catalysts are used to convert the syngas into light hydrocarbons (like ethane) which are further processed into gasoline and diesel. This method was used on a large technical scale in Germany between 1934 and 1945 and is currently being used by Sasol in South Africa. In addition to creating gasoline, syngas can also be converted into methanol, which can be used as a fuel, or into a fuel additive.

Syngas may be converted to liquids through conversion of the syngas to methanol which is subsequently polymerized into alkanes over a zeolite catalyst. This process, named as the Mobil MTG Process, was developed by Mobil in early 1970s.

As geological processes apply pressure to dead biotic material over time, under suitable conditions it is transformed successively into:

• Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland. In its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water
• Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Upper Palaeolithic
• Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
• Bituminous coal, dense sedimentary rock, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke
• Steam coal is a grade between bituminous coal and anthracite, once widely used as a fuel for steam locomotives. In this specialized use it is sometimes known as sea-coal in the U.S. Small steam coal (dry small steam nuts or DSSN) was used as a fuel for domestic water heating
• Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil, as from the deposits in Pennsylvania
• Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.

The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:

Name	Volatiles %	C Carbon %	H Hydrogen %	O Oxygen %	S Sulfur %	Heat content kJ/kg
Braunkohle (Lignite)	45-65	60-75	6.0-5.8	34-17	0.5-3	<28470
Flammkohle (Flame coal)	40-45	75-82	6.0-5.8	>9.8	~1	<32870
Gasflammkohle (Gas flame coal)	35-40	82-85	5.8-5.6	9.8-7.3	~1	<33910
Gaskohle (Gas coal)	28-35	85-87.5	5.6-5.0	7.3-4.5	~1	<34960
Fettkohle (Fat coal)	19-28	87.5-89.5	5.0-4.5	4.5-3.2	~1	<35380
Esskohle (Forge coal)	14-19	89.5-90.5	4.5-4.0	3.2-2.8	~1	<35380
Magerkohle (Non baking coal)	10-14	90.5-91.5	4.0-3.75	2.8-3.5	~1	35380
Anthrazit (Anthracite)	7-12	>91.5	<3.75	<2.5	~1	<35300
Percent by weight

The middle six grades in the table represent a progressive transition from the English-language sub-bituminous to bituminous coal, while the last class is an approximate equivalent to anthracite, but more inclusive (the U.S. anthracite has < 6% volatiles).

Cannel coal (sometimes called "candle coal"), is a variety of fine-grained, high-rank coal with significant hydrogen content. It consists primarily of "exinite" macerals, now termed "liptinite".

Countries with annual import higher than 30 million tonnes are shown.

Imports of Coal by Country and year (million short tons)

Country	2006	2007	2008	2009	Share
Japan	199.7	209.0	206.0	182.1	17.5%
China	42.0	56.2	44.5	151.9	14.5%
South Korea	84.1	94.1	107.1	109.9	10.6%
India	52.7	29.6	70.9	76.7	7.4%
Taiwan	69.1	72.5	70.9	64.6	6.2%
Germany	50.6	56.2	55.7	45.9	4.4%
United Kingdom	56.8	48.9	49.2	42.2	4.1%
Total	991.8	1,056.5	1,063.2	1,039.8	100%

Countries with annual export higher than 10 million tonnes are shown.

Exports of Coal by Country and year (million short tons)

Country	2007	2008	2009	Share
Australia	268.5	278.0	288.5	26.5%
Indonesia	221.9	228.2	261.4	24.0%
Russia	112.2	115.4	130.9	12.0%
Colombia	74.5	74.7	75.7	6.9%
South Africa	72.6	68.2	73.8	6.8%
USA	60.6	83.5	60.4	5.5%
China	75.4	68.8	38.4	3.5%
Canada	33.4	36.5	31.9	2.9%
Vietnam	35.1	21.3	28.2	2.6%
Kazakhstan	32.8	47.6	25.7	2.4%
Poland	20.1	16.1	14.6	1.3%
Total	1,073.4	1,087.3	1,090.8	100%

The reserve life is an estimate based only on current production levels and proved reserves level for the countries shown, and makes no assumptions of future production or even current production trends. This is a list of countries by coal production in 2009 based mostly on Statistical Review of World Energy 2010 published in 2010 by BP ranks countries with coal production larger than 100 millions tonnes.

Production of Coal by Country and year (million tonnes)

Country	2007	2008	2009	Share	Reserve Life (years)
China	2526.0	2782.0	3050.0	45.6 %	38
USA	1040.2	1062.8	973.2	15.8 %	245
India	478.4	521.7	557.6	6.2 %	105
EU	593.4	587.7	536.8	4.6 %	55
Australia	399.0	401.5	409.2	6.7 %	186
Russia	314.2	326.5	298.1	4.3 %	150+
Indonesia	217.4	229.5	252.5	3.6 %	17
South Africa	247.7	250.4	250.0	3.6 %	122
Germany	201.9	192.4	183.7	2.6 %	37
Poland	145.9	143.9	135.1	1.7 %	56
Kazakhstan	97.8	111.1	101.5	1.5 %	308
Total World	6,421.2	6,781.2	6,940.6	100 %	119

The 930 billion short tons of recoverable coal reserves estimated by the Energy Information Administration are equal to about 4,116 BBOE (billion barrels of oil equivalent). The amount of coal burned during 2007 was estimated at 7.075 billion short tons, or 133.179 quadrillion BTU's. This is an average of 18.8 million BTU per short ton. In terms of heat content, this is about 57,000,000 barrels (9,100,000 m³) of oil equivalent per day. By comparison in 2007, natural gas provided 51,000,000 barrels (8,100,000 m³) of oil equivalent per day, while oil provided 85,800,000 barrels per day.

BP, in its 2007 report, estimated at 2006 end that there were 909,064 million tons of proven coal reserves worldwide, or 147 years reserves-to-production ratio. This figure only includes reserves classified as "proven"; exploration drilling programs by mining companies, particularly in under-explored areas, are continually providing new reserves. In many cases, companies are aware of coal deposits that have not been sufficiently drilled to qualify as "proven". However, some nations haven't updated their information and assume reserves remain at the same levels even with withdrawals. Collective projections generally predict that global peak coal production may occur sometime around 2025 at 30 percent above current production in the best case scenario, depending on future coal production rates.

Of the three fossil fuels, coal has the most widely distributed reserves; coal is mined in over 100 countries, and on all continents except Antarctica. The largest reserves are found in the USA, Russia, China, India and Australia. Note the table below.

Proved recoverable coal reserves (million tons (teragrams))

Country	Bituminous & Anthracite	SubBituminous	Lignite	TOTAL	Percentage of World Total
United States	108,501	98,618	30,176	237,295	22.6
Russia	49,088	97,472	10,450	157,010	14.4
China	62,200	33,700	18,600	114,500	12.6
Australia	37,100	2,100	37,200	76,500	8.9
India	56,100	0	4,500	60,600	7.0
Germany	99	0	40,600	40,699	4.7
Ukraine	15,351	16,577	1,945	33,873	3.9
Kazakhstan	21,500	0	12,100	33,600	3.9
South Africa	30,156	0	0	30,156	3.5
Serbia	9	361	13,400	13,770	1.6
Colombia	6,366	380	0	6,746	0.8
Canada	3,474	872	2,236	6,528	0.8
Poland	4,338	0	1,371	5,709	0.7
Indonesia	1,520	2,904	1,105	5,529	0.6
Brazil	0	4,559	0	4,559	0.5
Greece	0	0	3,020	3,020	0.4
Bosnia and Herzegovina	484	0	2,369	2,853	0.3
Mongolia	1,170	0	1,350	2,520	0.3
Bulgaria	2	190	2,174	2,366	0.3
Pakistan	0	166	1,904	2,070	0.3
Turkey	529	0	1,814	2,343	0.3
Uzbekistan	47	0	1,853	1,900	0.2
Hungary	13	439	1,208	1,660	0.2
Thailand	0	0	1,239	1,239	0.1
Mexico	860	300	51	1,211	0.1
Iran	1,203	0	0	1,203	0.1
Czech Republic	192	0	908	1,100	0.1
Kyrgyzstan	0	0	812	812	0.1
Albania	0	0	794	794	0.1
North Korea	300	300	0	600	0.1
New Zealand	33	205	333-7,000	571-15,000	0.1
Spain	200	300	30	530	0.1
Laos	4	0	499	503	0.1
Zimbabwe	502	0	0	502	0.1
Argentina	0	0	500	500	0.1
All others	3,421	1,346	846	5,613	0.7
Total world	404,762	260,789	195,387	860,938	100