Other than the number of boxes, many containers heading back to Felixstowe / Soton / Gateway are loaded with scrap, which is rather heavier than most of the consumer goods they come in with.
There are different types of scrap so the payload will vary slightly, but by and large scrap containers tend to weigh about 25mt, or 12.5 mt per teu which is heavier than consumer goods. However, it's very unlikely that the southbound containers carried any scrap because Liverpool does not currently have a regular direct service to China or other areas which are known to recycle scrap materials.
I didn't know scrap generally travelled in shipping containers...how do they get it in & out without making a big mess?
It depends on the type of scrap. Waste paper and card is generally baled, plastic scrap may also be baled or it may be in big one tonne bags in granular form. Non ferrous metals will almost certainly be either in drums or palletised. Scrap tyres will be loose. There are very strict regulations for shipments of scrap and the shipping lines demand sight of the paperwork at the time of booking, in addition containers may be subject to random inspection at the port of loading to check compliance.
I wouldn’t say it’s the normal route for scrap exports, but it’s a cheap way of doing it, filling a box that would otherwisebe hewding back to China emoty. Just chuck it in, and close the doors. It doesn’t need to be full. Lots of plastic goes the same way, albeit that’s lighter, obviously.
Sadly it's not as simple as that, the movement of scrap or all types is highly controlled and as I mentioned earlier is subject to very strict regulation. It's also very competitive and I can assure readers that beneficial cargo owners (BC0) will switch volumes between carriers for US$25.00 difference in cost. Because of the competitive nature of the market BCOs like to ensure the occupancy of the container is fully utilised hence why most scrap is shipped in 40ft units with payloads of around 25t. How plastic scrap is shipped depends a little on it's source, but packaging scrap of the type used in supermarkets etc will likely be in highly compressed bales, whilst scrap plastic from the manufacture or windows and doors may be in granular form in bags which can mean payloads can reach 25t.
It only seems to be a recent thing where someone must've been stood there scratching their head. Now they have hoist type thing that stands the container on its end so that the mechanical grab just drops it neatly in from the top. Before it's lowered to the ground and man goes up the top and closes the doors so it doesn't all fall again when it goes back to horizontal
Most shipping lines no longer accept loose scrap in their containers because of the damage it causes to the container walls and wooden floor. It's an expensive operation reflooring a container and the freight revenue generally does not justify the cost or the repair and the lost revenue whilst the container is out of commission at destination. For these reasons these movements tend to be accomplished by one way shipper owned containers.