* April ethanol exports soar from year before
* Also up 18 pct from month before
* China making ethanol to erode corn stockpiles
* Ethanol imports slow to trickle (Adds comment, background)
BEIJING, May 23 (Reuters) - China's ethanol exports soared in April from the same month the year before and imports slowed to a trickle, the latest sign that Beijing's drive to ramp up local output is upending trade flows in the world's fastest-growing biofuel market.
China has been pushing to erode a domestic glut in corn supply through steps such as using the grain to churn out ethanol or other products like biodegradable plastics.
The country exported 13,540 cubic metres of ethanol in April, up over 1,000 percent from a year earlier and 18 percent higher than the month before, data from the General Administration of Customs showed on Tuesday.
Traders said the reintroduction of an export rebate last year had revived foreign sales.
"This year there's a tax rebate of 13 percent and processors have subsidies," said a manager familiar with ethanol trade at trading company Zhejiang Materials. He declined to be identified as he was not authorised to speak with media.
In the first four months of the year, ethanol shipments jumped to 42,701 cubic metres, exceeding the total for the whole of 2016.
Saudi Arabia remained the top buyer of the fuel in April, accounting for 66 percent of cargoes.
Meanwhile, China imported just 23 cubic metres of ethanol last month, as a big hike in taxes at the end of 2016 hit overseas purchases.
Reporting by Dominique Patton and Josephine Mason; Editing by Joseph Radford