Acid hydrolysis of fibers from dairy manure

Concentrated acid hydrolysis of lignocellulosic materials is a conventional treatment process for the production of mono-sugars. However, this method has been proved ineffective and undesirable for the treatment of dairy manure due to the high nitrogen content of dairy manure and the environmental issues caused by the use of highly concentrated acid solution. In an effort to overcome these barriers, a modified acid hydrolysis process with short reaction time was introduced that involved a nitrogen-removing pretreatment followed by decrystallization with concentrated acid and then hydrolysis using dilute acid. The effects of nitrogen, acid concentration, reaction time, and temperature were investigated. A pretreated manure with a low nitrogen content of 1.3% was used as the substrate. The results indicated that the optimal conditions for fiber decrystallization were 75% acid concentration, 3:5 sample to acid ratio (weight basis), and 30 min of reaction time; while the optimal conditions for acid hydrolysis were 12.5% acid and 10% dry sample at 135 °C for 10 min. These conditions produced 26 g/L glucose at a yield of 84% and 11 g/L hemicellulose-sugars at a yield of 80%.