In general, shipping has been shown to be an energy-efficient means of transportation. While more than 90% of world trade is transported by sea , only about 3% of the world's carbon dioxide emissions come from shipping . We aspire to reduce this even further by becoming a top quartile, climate-efficient oil and gas transporter by 2020. We are endeavouring to reduce our carbon footprint from shipping through lower fuel consumption and greater fuel efficiency in our activities.
Statoil strives to continually expand its commitment to a cleaner natural environment. Our sustainable shipping strategy also addresses key environmental issues relating to the minimisation of invasive aquatic species, the reduction of exhaust gas emissions - including carbon dioxide, nitrogen oxides and sulphur oxides - and risks pertaining to accidental spills.
A number of specific achievements support our sustainable shipping strategy.
For example, we are reducing our emissions through initiatives such as being the world's first commercial enterprise to convert a tanker from heavy oil fuel to dual fuel, enabling liquid natural gas (LNG) to be used for power generation. Compared with heavy oil fuel, the combustion of LNG is expected to reduce nitrogen oxides emissions by 85%, carbon dioxide emissions by 25%, and sulphur oxides and other particles completely. 
The fouling of ships' hulls is a well-known phenomenon, causing reduced speed, increased fuel consumption and general wear and tear to vessels. To reduce fouling, Statoil employs the Norwegian service company CleanHull, which has an environmentally responsible method of cleaning ship hulls. Hull cleaning reduces emissions and minimises the transfer of invasive species. CleanHull removes hitch-hiking marine organisms picked up in foreign waters and can cut carbon dioxide emissions by around 100,000 tonnes a year if cleaning is performed twice annually. 
Although the number of large oil spills from tankers has decreased significantly over the past 40 years, the economic and reputational impacts have increased, and the issue is still highly relevant to the shipping industry.
To identify and analyse risk, we and Det Norske Veritas have developed an IT tool to calculate risk from our operations. The tool, which is currently being improved, includes GIS (geographical information system) functionality.
We have also stipulated technical requirements to minimise risk, and we regularly train our emergency response personnel and hold drills. Our requirements and training programme are under greater scrutiny after an oil spill occurred during loading to a shuttle tanker in the North Sea in 2007.
One action taken to reduce our emissions is the "green voyage procedure" (GVP) for shuttle tankers. GVP targets the optimisation of tanker scheduling. The strategy includes practices such as "virtual arrival", a process for tankers developed by the Oil Companies International Marine Forum (OCIMF) that establishes a framework for agreeing to reduce a vessel's speed on voyages to meet a revised arrival time when there is a known delay at the discharge port. 
According to Teekay's "Shuttle Tanker Emissions Report 2008", a two-knot decrease from 14 knots to 12 knots results in a 10% reduction in fuel consumption and an almost 6% decrease in greenhouse gas emissions. The most economically efficient speed is vessel specific, but it averages about 12 knots.