ENERGY USAGE IN UK ONION (ALLIUM CEPA L.) STORAGE

Abstract

The current practices and performance of curing and cold storage of Rijnsberger onions (Allium cepa L.) within the UK was investigated between September 2002 and April 2003. The study aims included investigation into the energy usages, economic, managerial and logistical aspects of three types of common UK onion storage methods; bulk, tonne container and large container (18 tonnes). Approximately 15.85% of the nationally stored crop was investigated, and the store raw data collated and subject to analysis to produce a storage index. The complete costs of each store was also investigated and compared by store type. It was found that the energy inputs do not necessary relate directly to the overall costs of storage, indicating many factors involved in the storage types investigated during this study. It was found that there was a relationship between the bulk density and the storage index. Comparing the container storage; large containers were cheaper to run than smaller containers, but had a higher initial capital investment, leading to a higher overall cost per tonne stored. Logistical aspects highlighted that large containers (18 tonne units) offer reduced handling with potential for over 1500 tonnes day -1 loading, but requires skilled operation. Smaller containers (1 tonne units) reduce the handling speed (480 tonnes day -1 ) due to the requirement for box fillers and extra manpower required to load the store, but offer greater crop traceability and isolation of problems. The energy costs per tonne were not in the same ranking as energy usage showing the importance of tariff selection. The choice of onion curing and cold storage is a complex issue that includes many enterprise specific factors, such as client base or cooperative ventures. However this study shows that energy factors correlate with store type in all cases.