China Biogas Heat Exchanger Manufacturer for Anaerobic Digestion Center Enamel delivers heat recovery and digester-heating solutions for biogas and anaerobic digestion (AD) systems, combining heat exchangers with glass-fused-to-steel (GFS) digester tanks and AD system support built for corrosive biogas environments. Anaerobic digestion depends on holding the digester at a stable mesophilic temperature (about 35 to 38 C) and recovering heat from combined heat and power (CHP)