Tar: A liquid product of thermal processing of carbonaceous materials.

Tar sand (bituminous sand): A formation in which the bituminous material (bitumen) is found as a filling in veins and fissures in fractured rocks or impregnating relatively shallow sand, sandstone, and limestone strata; a sandstone reservoir that is impregnated with a heavy, extremely viscous, black hydrocarbonaceous, petroleum-like material that cannot be retrieved through a well by conventional or enhanced oil recovery techniques.

TA study: Technical assistance study under the federal Institutional Conservation Program (ICP).

Tertiary air: Combustion air in addition to under-fire and over-fire air, injected downstream in the flame path to increase turbulence and aid in carbon burnout.

Tertiary heat exchanger: A heat exchanger that removes latent heat from the exhaust gases by cooling them below the condensation point.

Thermal NOx: Nitrous Oxide (NOx) emissions formed at high temperature by the reaction of nitrogen present in combustion air. cf. fuel NOx.

Thermochemical conversion is a chemical process that breaks long-chain organic compounds that make up biomass into short-chain hydrocarbons. Thermochemical conversion is characterized by higher temperatures and conversion rates than most other processes. Within thermo-chemical conversion four process options are available: combustion, pyrolysis, gasification and liquefaction. see Biochemical conversion.

Thinning: A tree removal practice that reduces tree density and competition among remaining trees in a stand.

Timberland: Forest land that is producing or is capable of producing crops of industrial wood, and for example, to make useful energy products.

Timber Product Output Database Retrieval System (TPO): Developed in support of the 1997 Resources Planning Act (RPA) Assessment, this system acts as an interface to a standard set of consistently coded TPO data for each state and county in the country. This set of national TPO data consists of 11 data variables that describe for each county the roundwood products harvested, the logging residues left behind, the timber otherwise removed, and the wood and bark residues generated by its primary wood-using mills.

Therm : A unit of energy equal to 100,000 Btus (= 105.5 MJ); used primarily for natural gas.

Thickening: the process of increasing the viscosity of a liquid either by reduction, or by the addition of a thickening agent.

Tipping fee: A fee for disposal of waste.

Tolerant Species: A species of tree that has the ability to grow in the shade of other trees and in competition with them.

Tonne (imperial ton, long ton, shipping ton): 2240 lb; equivalent to 1000kg or in crude oil terms about 7.5 bbl of oil.

Topping cycle: A cogeneration system in which electric power is produced first; the reject heat from power production is then used to produce useful process heat.

Topping and back pressure turbines: Turbines which operate at exhaust pressure considerably higher than atmospheric (noncondensing turbines); often multistage with relatively high efficiency.

Total lignin: The sum of the acid soluble lignin and acid insoluble lignin fractions.

Total solids: The amount of solids remaining after all volatile matter has been removed from a biomass sample by heating at 105°C to constant weight. (Source: Ehrman, T. Standard Method for Determination of Total Solids in Biomass. NREL-LAP-001. Golden, CO: National Renewable Energy Laboratory, October 28, 1994.)

Toxics: As defined in the 1990 Clean Air Act Amendments, toxics include benzene, 1,3 butadiene, formaldehyde, acetaldehyde, and polycyclic organic matter.

Tramp air: Unintentional, uncontrolled air entering the combustion chamber.

Tramp metal: Metal found in biomass fuel (nails, chainsaw chain, tools, etc.).

Transesterification: The chemical process in which an alcohol reacts with the triglycerides in vegetable oil or animal fats, separating the glycerin and producing biodiesel.

Transpiration Drying: The natural drying that occurs when leafy biomass material is left on the tree.

Traveling grate: A type of furnace in which assembled links of grates are joined together in a perpetual belt arrangement. Fuel is fed in at one end and ash is discharged at the other.

Tree-length: Trees felled, delimbed, and topped in the stump area and processed at the landing.

Triglyceride: A triglyceride is an ester of glycerol and three fatty acids. Most animal fats are composed primarily of triglycerides.

Trommel screen: A revolving cylindrical sieve used for screening or sizing compost, mulch, and solid biomass fuels such as wood chips.

Tub grinder: A shredder used primarily for woody, vegetative debris. A tub grinder consists of a hammermill, the top half of which extends up through the stationary floor of a tub. As the hammers encounter material, they rip and tear large pieces into smaller pieces, pulling the material down below the tub floor and ultimately forcing it through openings in a set of grates below the mill. Various sized openings in the removable grates are used to determine the size of the end product.

Turbine: A machine for converting the heat energy in steam or high temperature gas into mechanical energy. In a turbine, a high-velocity flow of steam or gas passes through successive rows of radial blades fashioned to a central shaft.

Turn down ratio: The lowest load at which a boiler will operate efficiently as compared to the boiler’s maximum design laod.

Turnkey: For mechanical systems, a contracting process under which the contractor has full responsibility for design and for the complete installed package of work. The owner accepts the completed system once the contractor has demonstrated that the system meets the performance specifications.

Two-pass Method: A harvest practice where roundwood and biomass are recovered in separate passes. Biomass removal can precede or follow the conventional product harvest.

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