With volatile organic compounds now capable of being used as fuel, the OCIMF* recommendations in its ‘Volatile Organic Compound Emissions from Cargo Systems on Oil Tankers’ are useful and prescient
Volatile organic compounds (VOCs) occur due to vaporisation of the surface of oil cargoes, from the liquid to the gas state, through evaporation or boiling (dependent on the boiling point). VOCs may contain methane, a component of the greenhouse effect, and/or non-methane elements that can affect human health.
The factors involved in the evaporation of VOCs from the oil cargo are temperature, pressure, concentration of the liquid, concentration of vapour in the cargo space, flow rate of the vapour, surface area of the liquid, volume of the tank space and surface area.
These factors can be manipulated on the tanker and the VOC captured by processing equipment. It can then be used as a fuel component, as is the case in the Wärtsilä-led Teekay e-shuttle tankers project, currently under construction in South Korea.
IMO published guidance on VOC management in MEPC.1/circ 609 in July 2009 which is a supplement to MEPC.185(59) which came into effect on 1 July 2010. The IMO requires all member states to have a VOC Management Plan that follows these guidelines.
"The Norwegian Climate and Pollution Directorate has set limits on VOC emissions during loading at Norwegian continental shelf oil fields”
The standards for the design, construction and installation of equipment to collect VOCs on tankers is laid down in Vapour Emission Control Systems (VECs) MSC/Circ.585 (16 April 1992) Marpol Annex VI/15 and there should be a VEC manual on-board. In addition, each tanker must have a system to collect VOCs for processing in a shoreside terminal.
Norway has gone further in its attempts to control VOC emissions. The Norwegian Climate and Pollution Directorate has set limits on VOC emissions during loading at Norwegian continental shelf oil fields.
OCIMF recommends that operators are aware of which elements of Marpol Annex VI regulation 15 apply to the nature of their operations, bearing in mind that the aim is to reduce the emissions of VOC. The VOC Management Plan must be approved by the Flag State or a recognised organisation before obtaining an International Air Pollution Prevention Certificate (IAPP). The VOC Management Plan should be oil tanker-specific and include:
The VOC Management Plan should also include the following drawings:
OCIMF recommends that the VOC Management Plan states the person on board responsible for the plan and those who have specific tasks or duties relating to the plan.
The guidelines note that the responsible person on board must complete a specific VOC training plan, which should cover:
*The Oil Companies International Marine Forum (OCIMF) was formed in 1970 in response to growing public concern about marine pollution, particularly by oil, after the Torrey Canyon incident in 1967. It comprises 107 oil companies worldwide.