Biological EM emissions
According to this author (1) the human body emits radiation, mostly in the infared region. Human body temperature generally exceeds that of its surroundings and so there is a net flow of heat from the body into the environment, some due to convection and some due to thermal radiation. 

This Czech paper suggests (2) human EM emission in a particular low-frequency band (0.5 - 30 Hz), but the writing is awkward and I do not think this is peer-reviewed. 

A more comprehensive Russian paper (3) discusses, among other things, emission of photons (light!) from human skin. The energy of this light is not very high (1-3eV, which is 1-3 times $1.602~ \text{x}~ 10^{-19}$ Joules), but it's not nil. 

This interesting topic has been studied extensively and this is a quick glance. Am adding the link furnished in a comment by OP above which does suggest that the body can emit energy via radioactive decay. 

Also, this link (4) based on the paper by Toohey below discusses radioactive emission by humans in some detail, including radioactive decay of potassium-40. There is apparently a mechanism by which ambient gamma radiation can interact with atoms in cells (photoelectric effect) to produce x-rays, which are emitted from the body. 

(1) Olivia Lee, Hong Kong Observatory, Sept. 2010

(2) Lipkove, Cechak, Human Electromagnetic Emission in the ELF Band,Measurement Science Rev. vol. 5 sec. 2, 2005 

(3) Ignativ et al., Fields in the Electromagnetic Spectrum Emitted From the Human Body..., J. Health, Medicine and Nursing, vol. 7, 2014

(4) Toohey RE, Keane AT, Rundo J. Measurement techniques for radium and the actinides in man at the Center for Human Radiobiology. Health Phys. 44(1):323–341; 1983.