Reducing Carbon Emissions from Greenhouse Production through the Use of Temperature Integration and Alternative Sources of Heat

Temperature integration (TI) exploits the fact that, within certain limits, developmental events respond to mean diurnal temperature, rather than distinct day/night effects. The saving that can be made using TI is reviewed, drawing upon glasshouse models and trials. Humidity control strategies also have a big impact on the savings that can be made as a result of TI and this is discussed. There are limits to the ability of plants to integrate temperature, and it is important that these limits are not exceeded. Otherwise, crop quality, scheduling or yield could be affected detrimentally. Problems can arise when plants are grown at both sub- and supra-optimal temperatures. This is because supra-optimal temperatures cannot fully compensate for a period of low temperature. We summarise crop trials that have been carried out to define the safe limits to TI for tomatoes and ornamentals, focusing on recent trials at Warwick HRI. While closed and semi-closed greenhouses in The Netherlands are provoking much interest, the potential for inter-seasonal storage of heat in aquifers in the UK is limited. There is also very little potential for the use of geothermal heat. Therefore, alternative technologies are needed to reduce the carbon footprint of glasshouse production. The UK has seen a greater emphasis on the use of 'waste' heat, biomass and anaerobic digestion. The potential of these and other technologies is discussed and a number of case studies are highlighted.