The abstract says that "The total net energy obtained during the 32 days run was about 1.5 MWh." At a conversion factor of about 33 kWh/gal, this is equivalent to the energy in about 45,000 gallons of gasoline, or about 1.3 million automobile miles at 30 miles per gallon.
The total fuel supplied was one gram, and not all of it was consumed/converted. There was no detectable radiation (other than heat and light) outside of the container. The "ash" remaining from the reaction was not radioactive.
Safe energy from almost nothing. What's not to like?
I completely blew this calculation.
Revision in process.