Nigerian banks are now accepting and dispensing the old 500- and 1,000-naira notes following a directive by the Central Bank of Nigeria. However, due to the over 2 trillion naira mop up by the apex bank, scarcity of the old notes still persists. Dipo Ajayi, the Head of Fixed Income and FX at Chapel Hill Denham, joins CNBC Africa to explore how banks can ramp up currency circulation.