We present a silicon based metamaterial, Black Silicon in our case, which exhibits a very high wide band spectral emissivity in the spectral range of thermal radiation, up to 8 µm, which can be used as a broadband emitter. Black Silicon is a bottom-up nano-structured silicon surface that can be created using a variety of processes, such as wafer-level cryogenic plasma etching in our case. After demonstrating previously that the use of a heavily doped silicon wafer to fabricate Black Silicon can extend such remarkable emissivity to the mid-infrared (MIR) and touching the far-infrared (FIR) spectrum, we now report on the spectral hemispherical emissivity of BSi measured by both indirect and direct radiometric methods. The emissivity values obtained by the two methods are in good agreement.