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VOC losses

About 40 Suezmax cargoes of crude oil vanish into the air every year. That’s about 6 billion USD worth of oil. As much as half of it can be recovered with Venturie.

The most obvious problem with the emissions is cargo value lost, and perhaps that everybody is so used to accepting it. The less tangible loss is that of air quality. Hydrocarbon gases, nitric oxides from combustion and sun light create ground level ozone. It is not useful like the protective ozone layer, down here ozone damages crops, buildings and causes respiratory problems for people. Besides, it harms the plants’ ability to take up CO2. Ground level ozone is not just a city problem, since hydrocarbons and nitric oxides are long lived and transboundary pollution.

Methane does not take part in ozone formation, it’s just a very potent greenhouse gas. Therefore we speak of non-methane VOC, and refer methane to CO2 and “greenhouse protocols”.

VOC emissions from sea transport of oil are distributed as in the next figure. Discharge loss is evaporation during unloading, in a Suezmax (average crude oil tanker size) this is about 55 tonnes of hydrocarbon vapours that leave along with the incoming oil’s vapour growth when the ship loads.


In-transit losses are ventings through the mast riser at sea. Data from 60 ships, carrying all sorts of crudes on 300-odd voyages indicate 45 tonnes lost – 470 barrels of oil – per voyage from the average ship – a Suezmax tanker, and it’s tonnage dependent. This is about 20% of the total loss. Intertanko and Pres-vac claim that in-transit losses are considerably higher. The sudden pressure drop makes the oil produce a violent upsurge of hydrocarbons, similar to what can be seen from carbonated water. This is seen as sharp pressure rises after gas release.

With the Venturie Cargo System, the distribution is shifted: