0208 GMT - The way for Rio Tinto to create more value from its big aluminum business is by improving returns, not volume growth, says Morgan Stanley. Today, Rio's aluminum division is "a high-quality but mixed-return business," MS says. The bank sees operational and brownfield projects as "the most practical levers" for creating value. It highlights the AP60 ramp-up, Weipa replacement and expansion, and Matalco utilization, among other possible drivers. "The key test is whether future spending can lift ROCE [return on capital employed] and free cash flow, rather than merely sustain the existing asset base," says MS. "The company owns a differentiated aluminium business; executing on operational improvements and brownfield expansions will determine whether it can sustain a durable earnings and cash-flow pillar alongside iron ore and copper."