Enhanced biogasification from ammonia-rich swine manure pretreated by ammonia fermentation and air stripping

Abstract

Anaerobic digestion (AD) is widely applied for efficient energy recovery from livestock manure. However, due to its high ammonia concentration and the resultant inhibition to methanogens, dry AD of livestock manure is difficult to achieve high efficiency of energy recovery. In this study, ammonia fermentation and air stripping were attempted as pretreatments to remove and recover ammonia, targeting enhanced dry AD of ammonia-rich swine manure. The effect of manure pH on ammonia stripping was specifically investigated under high solids condition and then on the subsequent dry AD. In order to remove and recover more nitrogen from manure, ammonia fermentation was conducted to release ammonia before air stripping. Results indicated that 90% and 85% of ammonia removal from the ammonia fermented manure (with ammonia nitrogen content of 17–18 g for per kilogram of total solids (TS)) could be obtained after being stripped at pH10.2 and pH8.8, respectively. Moreover, the biogas production from the subsequent dry AD of ammonia-stripped swine manure was about 1.6–1.7 times higher than that from the raw manure (27.5 ml for per gram of volatile solids (VS)). This study implies that ammonia fermentation followed by air stripping is a prospective solution for ammonia removal and recovery from livestock manure and then enhanced dry AD.