Where will money to pay interest on $16 trillion come from??

[EdwardBaiamonte]

The Income Tax is what pays the Interest on the money the US Govt BORROWS from the Federal Reserve every year to run itself.

The Fed never buys bonds directly from the Treasury. It's prohibited from doing so.

1) actually, under Section 13(3) it can do anything it wants

2) if it doesn't buy directly so what everyone just buys from the primary dealers.