This paper explores how neat tallow can be used as a renewable fuel from waste for electricity generation in a large direct injection (DI) diesel engine capable of burning higher viscosity fuel. It looks also at the barriers imposed by the Waste Incineration Directive (WID) and possible ways of compliance. The research, including 2000 h of testing on a large 800 kW 600 rpm engine, was part of a program between John Pointon & Sons Ltd. and The University of Birmingham. The objective of this research was to study the impact of neat tallow on combustion quality, emissions, and engine performance taking into account fuel flow related problems. Two methods for assuring compliance with WID are proposed. Cooled and humidified exhaust gas recirculation (cEGR) was designed, employed and tested as a NO abatement method. Hydrogen-rich syngas production from tallow was shown to be a realistic proposal and potential benefits of its introduction in the environment of the large engine has been discussed using previously published studies. It is also proposed that the requirement for the exhaust to be subjected to temperatures above 850 °C could be satisfied by upgrading of waste tallow oil to syngas by employing an integrated tallow reformer looped with the engine.