Keywords: Waste heat, CHP, CO2 enrichment, integrated plant, total recycle, glasshouse tomatoes, biofuel.
More than 100,000 ha of sugar beet are grown in the UK annually to produce more than 7 million tonnes of beet with an increasing improving trend on sugar yield. That sugar processed in excess of the UK national quota is used for industrial applications such as bioethanol. The British Sugar Wissington Sugar Factory, one of four UK plants, typically handles more than 17,300 t/day of sugar beet through a processing period from mid-September to March.
It is a story of economy, efficiency and recycling. The factory operates a high quality gas fired combined heat and power (CHP) plant which can export electricity to the national grid. All raw materials taken into the factory are used to produce co-products in addition to the sugar produced. Partially refined sugar is stored to facilitate year round processing and sugar is crystallised at low temperature to maximise energy efficiency. The residual syrups are re-crystallised to increase sugar yield, and are then eluted through a continuous chromatographic process to extract other co-products. In practice the factory is operated on a relatively flexible basis with regards to specific volumes of feedstock for sugar or alcohol production. Ethanol production is year-round and in it, yeast and vinasses are recycled making it a very efficient process. Utilising the front end of the beet sugar factory to start the processing also adds to the efficiency.
The site also has 11 ha of glasshouses producing fresh tomatoes. Electricity requirements for the nursery is supplied from the sugar factory operated CHP plant; factory surplus low-grade heat is utilised; the atmosphere is enriched with factory surplus CO2 and rainfall is captured in a storage lagoon, to supply a substantial proportion of the crop water requirements. This makes the operation the most energy efficient of its type.
Richard Stark and Patrick Jarvis, British Sugar plc, Peterborough, UK.
12 pages, 6 figures.