We have a couple of levers to increase the interest rate. We could reduce inequality to reduce the supply of loan-able funds, we could allow large amounts of immigration to drive up the demand for loan-able funds, or we could keep interest rates high enough that we have a permanently high unemployment.
However I do have a strong worry that natural interest rates are too low for our current inflation. This gives the fed very little room to deal with the next crises. They should probably be targeting an inflation rate closer to 3-4% so we don't run into zero lower bound problems.