Globally it has been estimated that the transport of food accounts for nearly 20% of greenhouse gas (GHG) emissions from the entire food system. The relative contribution of emissions from the transport of perishable crops is even higher and is approximately twice the amount generated during their production. For the UK which imports three quarters of its fresh fruit and vegetables, the impact of transport on climate change becomes even more important. Scientists at NRI’s Produce Quality Centre (PQC) are at the forefront of research to increase the efficiency of crop storage as a means of enabling food supply chains to reduce GHG emissions.

Storage of perishable commodities such as fruit and vegetables, which continue to live, breathe and metabolise after harvest, relies on slowing down metabolism to delay deterioration and loss of nutrients. Low temperature storage is one very effective way to do this. However, storage can be further improved by changing the storage atmosphere. Controlled atmosphere (CA) storage relies on decreasing oxygen and increasing carbon dioxide concentrations (by 21% and 0.04% respectively) compared to those found in normal air. It has been demonstrated that these changes slow down the rate of respiration and metabolism overall, thereby extending storage life, if the changes are not taken beyond the ‘safe’ range for each commodity. There is an optimum atmospheric storage environment for each type of produce that results in a slow-down of metabolism while preventing damage. Unfortunately, this optimum storage environment differs depending not only on the type of produce, but also the growing conditions. The PQC houses the most extensive facility in the UK for controlling and testing atmospheres with more than 50 chambers in different sizes, each capable of independent atmospheric control.

Over the past few years, NRI has worked on a range of projects to utilise CA storage to improve the efficiency of the UK food system, reduce GHG emissions and support the move towards net zero.

CA storage to allow air freight to be replaced by sea freight

Of the various methods of transport, airfreight has the largest freight carbon footprint. Airplanes emit 500 grams of carbon dioxide per metric ton of freight per km travelled, while cargo ships emit only 10-40 grams of carbon dioxide per km. Some of the most important work conducted at the PQC is to develop CA protocols so that produce previously transported by air freight can now be transported by sea freight. More recently NRI has supported flowers and house plants wholesaler, Flamingo Flowers, to test CA storage of cut flowers, both as individual species and whole bouquets. Several flower types can already be sea-freighted from Kenya using CA. The ambition is to extend this so that most flower types can be sea freighted. 

Extending storage time of UK apples using low oxygen CA regimes

NRI worked with the technical company, Storage Control systems Ltd, apple growers, AC Goatham, Avalon and Sainsbury’s supermarket to develop technology to monitor apple metabolism in-storage thereby detecting low oxygen stress. This allowed the use of lower oxygen storage than was previously possible so that storage times could be extended. This has enabled apple growers to store UK grown apple varieties such as Gala well into the summer (July/August) and reduced the need to import and transport fruit from the Southern Hemisphere. ‘Work carried out by the team at the PQC has been invaluable to improving our long-term storage protocols for apples and pears,’ said Nigel Stewart, Technical Director at AC Goatham.

CA storage of vegetables to facilitate management of UK supplies

PQC scientists have demonstrated that with CA it is possible to store vegetables such as leeks for up to 4 months. This has made it possible for UK growers to extend the marketing season and reduce imports. A project is currently underway with Tesco PLC to store selected vegetables (broccoli, cauliflower, leeks and Brussels sprouts) for up to 3 weeks. This will allow better management of supplies at times of high demand, such as Christmas.