It makes products lighter, which saves energy in transportation, and it plays an important role in determining the texture and palatability of the finished product.” Those benefits come at a significant energy cost. It is estimated that drying accounts for about 25 percent of the total energy used in food production and 70 percent of CO2e emissions.
Much of this energy bill is due to basic physics. At 100ºC, it takes 2,260 kilojoules of energy to turn a kilogram of liquid water into vapor. In industrial food processing, this is typically accomplished in a convection dryer. Food or ingredients are transported through the dryer on a conveyor while hot dry air is blown over them. The heat evaporates the water, and the air carries it away, leaving the dried product ready for freezing, packaging, or further processing.
As a major supplier of drying equipment, Bühler has a clear picture of the energy requirements of modern drying operations and the challenges involved in improving efficiency. “The average dryer we supply can consume 2,300 to 2,600 kilowatts per hour,” says Britt. “For our customers, it’s not uncommon for drying to account for 50 percent of a plant’s total energy consumption.”
Industry-wide, this consumption leads to staggering totals. “If you take just the installed base of dryers that Bühler has supplied around the world, you are looking at an annual energy consumption of about 45 terawatt hours,” says Britt. “That is equivalent to the entire electricity consumption of Hungary per year. If we take the entire food drying market into account, total CO2e emissions amount to around 40 million tons a year.