Short ton

Natural occurring oxygen 18 is stable and available commercially, as is water (H20 with 15% 180). Commercial oxygen consumption in the U.S. is estimated at 20 million short tons per year and the demand is expected to increase substantially. 

Yields of algae grown in outdoor pond cultures (Table 1) are on the order of 15-40 g/(m -d) (24 short tons pet acre pet year). Higher yields can be obtained under artificial illumination, but growth of algae under these conditions is not economically feasible. 

Human activity, particularly in the developing world, continues to make it more difficult to sustain the world s biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm per year. Satellite imaging and field surveys show that Brazil alone has a deforestation rate of approximately 8 x 10 hm /yr (5). At a mean net carbon yield for tropical rain forests of 9.90 t/hm yr (4) (4.42 short ton /acreyr), this rate of deforestation corresponds to a loss of 79.2 x 10 t/yr of net biomass carbon productivity. 

X 10 Btu/short ton), the solar energy trapped in 17.9 x 10 t of biomass, or about 8 x 10 t of biomass carbon, would be equivalent to the world s fossil fuel consumption in 1990 of 286 x 10 J. It is estimated that 77 x 10 t of carbon, or 171 x 10 t of biomass equivalent, most of it wild and not controlled, is fixed on the earth each year. Biomass should therefore be considered as a raw material for conversion to large suppHes of renewable substitute fossil fuels. Under controlled conditions dedicated biomass crops could be grown specifically for energy appHcations. 

The concentration of most metals in the earth s cmst is very low, and even for abundant elements such as aluminum and iron, extraction from common rock is not economically feasible. An ore is a metallic deposit from which the metal can be economically extracted. The amount of valuable metal in the ore is the tenor, or ore grade, usually given as the wt % of metal or oxide. Eor precious metals, the tenor is given in grams per metric ton or troy ounces per avoirdupois short ton (2000 pounds). The tenor and the type of metallic compounds are the main characteristics of an ore. The economic feasibihty of ore processing, however, depends also on the nature, location, and size of the deposit the availabihty and cost of a suitable extraction process and the market price of the metal. 

Numbers represent shale oil yield range in L/1. To convert L/1 to gal/short ton, multiply by 0.2397. ... 

The first stage of the Stuart oil shale project near Gladstone, AustraUa, 6000 t/d (6600 short tons /d), is scheduled to be constmcted by Southern Pacific Petroleum. Einancial assistance from the AustraUan government, consisting of special depreciation incentives and exemption of gasoline taxes equivalent to about U.S. 1.91/m of cmde shale oil ( 12.00/bbl) has been assured (68). 

The UPI and MI retorts are processing 7000 t/d (7700 short tons/d) of Irati shale to produce 24,381 m /d (3870 bbl) of shale as well as 80 t (55 short tons) of LPG, 132 t (145 short tons) of clean fuel gas, and 98 t (108 short tons) of sulfur. The SIX plant has reached its design rate (Table 16) in an energy efficient manner with a high on-stream (operating) factor. 

Shale ok production in the former Soviet Union is also declining. The orky significant shale ok operations are in Estonia. Most of the rich (208 L/1 (50 gal/short ton)) Estonian ok shale is combusted directly as fuel. 

The western phosphates are sedimentary deposits in adjoining areas of Wyoming, Idaho, and Utah derived from a former inland sea. They consist of layers of limestone, phosphate, and chert, now budded and faulted so they are rarely horizontal. The phosphate ore is strip-mined using large earth-moving equipment such as shovels, scrappers, dump tmcks, and bulldozers to mine the overburden and phosphate ore. Mining ratios of overburden to metric ton of recovered ore are from 1—3 m /1 (2—4 yd /short ton). The typical mining practice is to remove ore and overburden from a pit in discrete layers (Lifts) of 10—20 m in depth. Overburden from the pit is back-hauled to a previously mined pit. Extensive land reclamation practices are later carried out to return the mine areas to natural states. 

The standard unit of measure for refrigeration capacity is known as the refrigeration ton. It represents the amount of heat that must be removed from a short ton (909 kg) of water to form ice ia 24 h. Its value is 3.51 kWt (12,000 Btu/h(= 12.7 MJ/h)). It is conventional to designate a kilowatt of refrigeration as a thermal kilowatt (kWt) to distiaguish it from the amount of electricity (kWe) required to produce the refrigeration. 

Double-Absorption Plants. In the United States, newer sulfuric acid plants ate requited to limit SO2 stack emissions to 2 kg of SO2 per metric ton of 100% acid produced (4 Ib /short ton Ib = pounds mass). This is equivalent to a sulfur dioxide conversion efficiency of 99.7%. Acid plants used as pollution control devices, for example those associated with smelters, have different regulations. This high conversion efficiency is not economically achievable by single absorption plants using available catalysts, but it can be attained in double absorption plants when the catalyst is not seriously degraded. 

Waterborne Transport. Despite natural limitations, the transportation of chemicals by water has enjoyed substantial growth, especially siace the ead of World War 11. Assisted by governmental developmeat of the inland waterways system, including locks and other navigational aids, water carriers transport large quantities of bulk chemicals in barges between inland ports or between such ports and coastal ports. In addition, bulk chemicals ate transported by self-propelled tank vessels between U.S. coastal points, and between U.S. ports and overseas destinations. In 1989, 56.1 million metric tons (61.9 million short tons) of chemicals were transported in the U.S. domestic waterborne commerce (16). 

Production and consumption of wood products and residues are measured ia various units, based on common usage and their metric equivalents (2—4). Pulpwood logs and fuelwood are commonly measured ia cords. A cord refers to a stacked pile of wood, with outside dimensions of 4 by 4 by 8 ft (1.22 by 1.22 by 2.44 m) and a volume of 128 ft (3.62 m ). The weight of a cord depends on density of wood and bark and on moisture content. In the United States, it can range from 1.3 to 1.7 short tons (1.2 to 1.5 metric tons), air dried. 

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