Sulfonated carbon-based catalysts were prepared from agroindustrial wastes (sugar cane bagasse, coconut husk, and coffee grounds). These catalysts showed high activity for glycerol etherification with tert-butyl alcohol. Yields of mono-tertbutyl glycerol (MTBG), di-tert-butyl glycerol (DTBG), and tri-tert-butyl-glycerol (TTBG) were higher than that obtained using Amberlyst-15 commercial resin. At 393 K and 5 wt % catalyst loading, glycerol conversion and selectivity to DTBG+TTBG after 4 h reaction time were 80.9% and 21.3%, respectively, with the sugar cane bagasse-based catalyst. Both catalytic activity and selectivity were affected by the presence of water in the reaction medium. However, the flexible and hydrophilic structure of the oxidized carbon allows the adsorption of water without compromising the activity of acid sites.