North of England P and I

The cargo, essentially a waste product from the production of olive oil, is shipped from typical olive-producing countries, such as Tunisia or Greece.

When producing olive oil, the by-product ‘olive mill waste water’, can be treated to extract the majority of the liquid. The remaining solid substance is known by a number of names, such as ‘olive mill solid waste’, ‘olive millcake’ or ‘olive margine’ and can be used for soil stabilisation or biomass fuel.

https://www.nepia.com/articles/warning-on-risks-of-olive-waste-cargoes/