* Trading houses hit by low volatility, compliance costs
* Gunvor still deciding on Rotterdam refinery coker unit
* CFO says return on U.S. investment to show in 2018 figures
* LNG traded volume rose to 7 mln tonnes, more growth targeted (Adds details, quotes)
By Julia Payne
LONDON, May 3 (Reuters) - Swiss-based energy trader Gunvor posted its lowest net profit last year since at least 2011 due to major investments to set-up a U.S. trading presence and a prolonged planned turnaround at one of its refineries, the company said on Thursday.
Net profit fell by 49 percent to $162 million from $315 million in 2016 while the rise in oil prices raised revenue to $63 billion from $47 billion. The level was its lowest since at least 2011.
Traded volumes rose 22 percent to 184 million tonnes from 153 million.
In a statement, Gunvor said a difficult trading environment and the end of several long-term contracts and storage commitments also contributed to the lower profit.
Profit at some of Gunvor's main competitors was also hit by the low volatility which characterised global oil prices for much of 2017 and the year-end market shift from a contango structure to backwardation.
In addition to the market structure change, the rising costs of compliance and credit has also weighed generally on trading houses, CFO Jacques Erni said.
Vitol's net profit dropped about 25 percent and Trafigura's fell 9 percent year-on-year to the lowest since 2010.
Gunvor's choice to build up a trading firm in the United States rather than buy one came at a high cost as there was no immediate positive addition to the balance sheet, Erni said.
"It was a pure cost, it's gone from a one-man show to an 80 person operation. It's been much slower than we thought but it's there now and it's performing very well now in 2018," Erni said.
"Getting registered, getting licences in all the states because we are trading domestically ... it was complicated, expensive and time-consuming. We also hired traders and trading teams."
He added that growth from its new U.S. operations would only be reflected in 2018 results as trading there mainly ramped up at the end of 2017. Gunvor now has two U.S. offices in Houston and Stamford, Connecticut as well as a representative office in Calgary, Canada.
As for the turnaround that takes place every six years at its 110,000 bpd Ingolstadt refinery, Erni said the timing was unfortunate as Gunvor missed out on strong margins in the first quarter of 2017 when the plant was shut.
He added the turnaround was extended to about 7-8 weeks from 4-5 weeks when the firm saw opportunities to make additional improvements.
Erni said the most notable volume increase was in liquefied natural gas, which grew to 7 million tonnes from 4 million tonnes in 2016.
For 2018, expanding trade in the U.S. domestic market and in LNG were the company's priorities. The firm was also looking to do more structured pre-export finance deals.
In terms of physical investments, Gunvor was still deciding whether to invest in adding a coking unit to its 88,000 barrel per day Rotterdam refinery to convert output of high-sulphur fuel oil into higher quality products like diesel.
Shipping is the main outlet for fuel oil and a global rule change in 2020 is expected to create a glut of the product and hurt the profitability of refineries unless they alter their yield make-up.
The rules from the International Maritime Organization (IMO)aim to cut sulphur emissions produced by ships, creating a challenge for shipping companies and oil refiners.
Reporting by Julia Payne; editing by Jason Neely/David Evans