NOVELTY - Autothermal torrefaction device comprises: torrefaction chamber(s) (40) having inlet (41) for biomass and outlet(s) (43, 44); outer jacket (120) surrounding chamber(s) and having inlet (122) and outlet (124), where jacket and chamber(s) define space in between; and burner unit (90) having inlet connected to chamber outlet and outlet connected to jacket inlet, so that vapors produced from within chamber(s) travel into burner unit for combustion of at least a portion of vapors and then travel through space between jacket and chamber(s) to provide heat for autothermal biomass torrefaction.    USE - As autothermal torrefaction device for autothermal torrefaction of biomass (claimed). The torrefied biomass is useful as a coal fuel substitute or biomass fuel additive; bio-char that is useful as both permanent carbon sequestration material in soil and soil amendment for increasing plant growth rates; as feedstock for further biomass gasification and feedstock for liquid fuel substitutes; and as fuel, fertilizer, and long-term carbon storage. The autothermal torrefaction device is also useful as waste disposal or waste reduction unit to reduce weight and volume of animal and plant waste products.    ADVANTAGE - The device provides efficient autothermal torrefaction device, as compared to prior art torrefaction devices. In device, outer jacket and torrefaction chamber define space between them such that burner unit including inlet operatively connected to chamber outlet and outlet operatively connected to jacket inlet, which allow vapors produced or released from within chamber to travel into burner unit for combustion of at least portion of vapors and subsequently travel through space between jacket and chamber to provide heat necessary for autothermal torrefaction of biomass. Also, combustion/flue-gases from burner indirectly heat biomass through walls of chamber. The combustible gases produced and/or released in chamber are at least partially combusted in burner to generate process heat for biomass torrefaction in conjunction with heat available from any steam driven from biomass in chamber. Thus, with use of device, there is no need to segregate water vapor from other gases emitted by biomass, and biomass can have moisture content as high as (55 wt.%). Thus, all heat energy used for torrefaction comes from biomass itself. The device is stationary; or mobile and/or modular so that it can be field portable and self-heated, which reduces transportation costs for fuel production and eliminates such costs for carbon sequestration and soil amendment. The device also increases cost effectiveness of using torrefied biomass as fuel, in which autothermal torrefaction device is operated at point separate from power plant, where point of operation is point of harvest having source of biomass comprising field, farm, or forest; or more than one off-site field of operation including biomass for torrefaction. Thus, costs, per British thermal unit (BTU), of transportation of shipping feedstocks are greatly reduced, as cost of transporting water in untreated biomass is substantially eliminated and fuel in more energy dense. The proximity of fuel production to original feedstock source also reduces overall use of carbon emitting fuels. The device further includes feed pelletizer or briquetter for hot torrefied biomass to form pellets or briquettes with relatively small energy inputs and no additional binders; such that device provides many products in the fields and forests with a technology that is mobile and/or modular. As torrefaction process drives off most to all of moisture contained in biomass and further renders biomass hydrophobic in nature, cost of transporting torrefied biomass is less than cost of transporting unconverted biomass. Moreover, hydrophobic nature of torrefied biomass enables longer transportation and holding/storage times without undesirably picking up moisture. Further, as torrefied biomass is less likely to rot than untreated biomass, torrefied biomass can be stored for greater periods of time prior to use.    DETAILED DESCRIPTION - An autothermal torrefaction device, comprises: torrefaction chamber(s) (40), each including chamber inlet (41) for receiving biomass and at least one chamber outlet (43, 44); an exterior housing defining outer jacket (120) substantially surrounding torrefaction chamber(s) and including jacket inlet (122) and jacket outlet (124), where outer jacket and torrefaction chamber(s) define space between them; and a burner unit (90) including inlet operatively connected to torrefaction chamber outlet and outlet operatively connected to jacket inlet; such that vapors produced or released from within torrefaction chamber(s) travel into burner unit for combustion of at least a portion of vapors and subsequently travel through space between jacket and torrefaction chamber(s) to provide heat necessary for autothermal torrefaction of biomass. The autothermal torrefaction device further comprises at least one pellet or briquette mill operatively connected to chamber outlet such that torrefied biomass exiting torrefaction chamber is palletized, briquetted, or densified. INDEPENDENT CLAIMS are included for the following:    (1) process for autothermal torrefaction of biomass involving: indirectly heating biomass and air surrounding biomass within torrefaction chamber(s) through walls of the chamber(s) to temperature sufficient to produce torrefied biomass; allowing or drawing vapors produced or released from within chamber(s) into burner unit; combusting at least a portion of vapors in burner unit; and passing vapors through jacketed space located between and defined by chamber(s) and exterior housing substantially surrounding chamber(s), such that vapors provide heat necessary for autothermal torrefaction of biomass within torrefaction chamber;    (2) method for increasing cost effectiveness of using torrefied biomass as fuel, involving: providing at least one autothermal torrefaction device at point of operation separate from power plant; charging biomass located at point of operation to autothermal torrefaction device; and converting biomass located at point of operation into torrefied biomass; and    (3) process for producing pellets of torrefied biomass, involving: converting untreated biomass into torrefied biomass at a point of harvest; and pelletizing the torrefied biomass at the same point of harvest.    DESCRIPTION OF DRAWING(S) - The figure shows autothermal torrefaction device.    Heat exchanger (10)    Torrefaction chamber (40)    Torrefaction chamber inlet (41)    Torrefaction chamber outlet (43, 44)    Burner (90)    Portable gas tank (100)    Circular outer jacket (120)    Jacket inlet (122)    Jacket outlet (124)