About 90 percent of the world's goods are carried by sea, with more than 70 percent in shipping containers carrying everything from TVs to sportswear from Asia to the rest of the world. But the global imbalance in trade means most of these containers are empty on the return journey.
Design student Philippe Hohlfeld, from London's Royal College of Art (RCA), has devised a way to stop this empty space going to waste. Grow Frame is a collapsible hydroponic farm that could grow vegetables inside the empty containers during the weeks-long sea voyage.
"Grow Frame tackles the challenge that half of all containers going to China are empty. And that means, right now, 13 million containers annually are travelling around with just air. And when I heard about that I thought 'no, that's not a problem, that's an opportunity," Hohlfeld told Reuters.
"Every container is 12 square meters of land, and they're basically free. And free real estate in the world is really hard to come by, and especially in the countries where they end up in China and Japan and south-east Asia, that land would be really expensive and is at a premium."
Each plant is grown in small individual plastic bags containing all the water and nutrients needed to feed the plant during the trip.
The mini farms would cultivate vegetables using battery-powered LED lights that can be adjusted to provide precisely the right spectrum of light for optimal growth. Hohlfeld said the energy efficient lights and the battery would hold enough power for the duration of the voyage; for example, for the approximately three weeks it takes for the vessel to travel from the UK to China.
To keep the climate inside each container as natural as possible, Hohlfeld said he's planning to grow mushrooms alongside leafy vegetables to help balance the mini ecosystem.
"I'm growing cabbages, spinach, lettuces and bean sprouts. All these plants create oxygen, as we know, and it's really good in nature because it balances with animals. But in the container it could be a problem; so I'm introducing mushrooms which turn the oxygen back into CO2 because they respire the same way that we do. And that way the whole system keeps itself in check," he said.
A key design consideration of Grow Frame was for it to collapse to a fraction of the size so as not to take up valuable space when the container was transporting goods.
"I thought about an autonomous process that works in an enclosed environment over three weeks and that brings a real benefit to China and that can be as collapsible as possible; so it can be as small as possible," Holhfeld said, adding that he now hopes to turn his proof-of-concept design into a working prototype that could be tested on the open seas.
Holhfeld is now looking for funding to help turn the concept into a reality. He estimates it would cost around £9,000 ($12,080 USD) to develop and manufacture the first frames, and a further £6,000 ($8,050 USD) to pay for a shipping trial. But the potential profitability of the reusable system would quickly recoup the initial costs, he said.