ANAEROBIC DECOMPOSITION OF SWINE MANURE AND AMMONIA GENERATION IN A DEEP PIT

This article reports a laboratory study of swine manure decomposition in a deep pit. Distributions of solids, organic matter pH, and ammonia in fresh swine manure after 12 h settling in a 1.2 m column were char acterized, and solids reduction and ammonia generation rate during 28 d anaerobic decomposition were determined by using the manure initiall y having 1.8% and 3.3% total solids content (TS). In the settled manur e, the pH became lower toward the bottom of the pit where manure solid s and organic matter became concentrated, and the pH of bottom manure layer was 0.5 and 0.9 unit lower than the pH of top manure layer for t he manure initially having 1.8% and 3.3% TS, respectively. Ammonia dis tribution in the manure was relatively uniform. The manure started to decompose rapidly after excretion from pigs. During the 28 d decomposi tion period, the solids contents of bottom manure layers were reduced linearly with time, and ammonia increased logrithmically with time. Hi gher temperature resulted in higher solids reduction and ammonia gener ation rate in the manure. The TS of bottom layer manure was reduced by 15% at 20 degrees C and 27% at 30 degrees C by the end of the 28 d pe riod. The determination methods and prediction equations for ammonia g eneration rates in discrete layers of decomposing manure are presented .