I agree, I missed the point about the bias. It is essentially an amplified crystal set.
However, in the dim past when I made crystsal sets, we listened with earphones that had a resistance of about 2k. So the 10k should be adequate. Certainly, the selectivity won't be brilliant, but he only wants a short range receiver.
The simplest way to bias it would be to connect two 22k resistors in series across the supply rails and connect the + input of the op amp to the mid point.
Also, the gnd line should be connected to earth and the antenna cut to length according to the frequency.
Len