It seems in Andrea Rossi cold fusion experiment the main contribution is due to repulsive gravity.
Attractive gravity and repulsive gravity have the magnitude of the electromagnetism:
http://www.zpenergy.com/modules.php?name=News&file=article&sid=3268
The scientific community thinks wrongly that the interaction by gravitons is 10
40 times weaker than electromagnetism.
Gravity as a macroscopic phenomenon (as discovered by Newton) is a combination of interactions by two sort of gravitons:
Repulsive gravitons
Attractive gravitons
The interaction by repulsive gravitons is a little weaker than the interaction by attractive gravitons.
Such "soup" of gravitons cause a resultant macroscopic gravity 10
40 times weaker then electromagnetism.
However, in special conditions near to nuclei, only the attractive gravity actuates, and so it helps the cold fusion, since it has the magnitude of the electromagnetism.
However, cold fusion occurs through resonance, in special conditions, and so the gravity only helps its occurrence.
Gravity ifself, alone, cannot produce cold fusion