* August aluminium output at 2.84 mln T -stats bureau
* Lowest on a daily basis since May -Reuters calculations
* Non-ferrous output at 4.54 mln T, down 1.8 pct from July (Adds detail, background)
BEIJING, Sept 14 (Reuters) - China's primary aluminium production slipped 3 percent in August from the month before, government data showed on Friday, hit by high raw material costs for smelters.
The world's biggest aluminium producer churned out 2.84 million tonnes of the metal last month, according to the National Bureau of Statistics (NBS).
That compares with 2.93 million tonnes in July, which matched the all-time monthly high, but was up 7.8 percent from a year earlier, the NBS said.
On a daily basis, China produced around 91,600 tonnes of primary aluminium last month, the lowest since May, according to Reuters calculations based on the data.
Aluminium prices on the Shanghai Futures Exchange climbed 2.1 percent over August but spot prices for alumina, the substance used to make the metal, climbed by 10.8 percent in the key eastern China region <SMM-ALM-ECHN> over the same period, putting smelters under pressure.
Over the first eight months of 2018, China produced 22.21 million tonnes of aluminium, up 3.5 percent year-on-year, the data showed on Friday.
Output of a group of 10 nonferrous metals - including copper, aluminium, lead, zinc and nickel rose 5.7 percent year-on-year to 4.54 million tonnes, but was down 1.8 percent from 4.62 million tonnes in July.
Output from this group in the first eight months was up 3.8 percent at 35.71 million tonnes. The other non-ferrous metals in the group are tin, antimony, mercury, magnesium and titanium. (Reporting by Tom Daly Editing by Joseph Radford)