Sustainable Solar Drying of Brewer’s Spent Grains: A Comparison with Conventional Electric Convective Drying

CAPOSSIO, JUAN PABLO; FABANI, MARÍA PAULA; REYES-URRUTIA, ANDRÉS; RODRIGO TORRES SCIANCALEPORE

Process Design and Sustainable Development

MDPI

Lugar: Basilea; Año: 2024; p. 110 - 127

Spent grains from microbreweries are mostly formed by malting barley (or malt) and aresuitable for a further valorization process. Transforming spent grains from waste to raw materials,for instance, in the production of nontraditional flour, requires a previous drying process. A naturalconvection solar dryer (NCSD) was evaluated as an alternative to a conventional electric convec-tive dryer (CECD) for the dehydration process of local microbrewers’ spent grains. Two types ofbrewer’s spent grains (BSG; Golden ale and Red ale) were dried with both systems, and sustainabilityindices, specific energy consumption (eC ), and CO 2 emissions were calculated and used to assessthe environmental advantages and disadvantages of the NCSD. Then, suitable models (empirical,neural networks, and computational fluid dynamics) were used to simulate both types of dryingprocesses under different conditions. The drying times were 30–85 min (depending on the dryingtemperature, 363.15 K and 333.15 K) and 345–430 min (depending on the starting daytime hourat which the drying process began) for the CECD and the NCSD, respectively. However, eC andCO2 emissions for the CECD were 1.68–1.88 · 10−3 (kW h)/kg and 294.80–410.73 kg/(kW h) for thedifferent drying temperatures. Using the NCSD, both indicators were null, considering this aspect asan environmental benefit.