Chemical properties of liquid swine manure for fermentation step in public livestock recycling center

Abstract

The nutrients in livestock manure produced during fermentation processes in public livestock recycling centers are used as fertilizers. However, the large amounts of swine manure produced in intensive livestock farms can be a nonpoint source of pollution. In this experiment, we investigated the chemical properties, inorganic components, and heavy metal contents in 101 samples of liquid swine manure collected from 28 public livestock recycling centers throughout the nation. Results showed that the average pH of the samples was alkaline (pH range 5.18 to 9.54), and their maximum EC was <TEX>$53.2dS\;m^{-1}$</TEX>. The amounts of total nitrogen and total phosphorus were in the range of 1000 - 2000 and <TEX>$200-800mg\;L^{-1}$</TEX> while potassium, which constituted 47% of the total inorganic ions recovered from the liquid swine manure, amounted to <TEX>$1500mg\;L^{-1}$</TEX>. The most distinctive heavy metals recovered from the liquid swine manure were copper and zinc although the amounts of both heavy metals were much lesser than those of the standards as livestock liquid fertilizer set by the Rural Development Administration. On the other hand, the amount of nitrogen decreased rapidly with an increasing fermentation period from immature to mature, assumed to be lost as volatile compounds, such as ammonia, which are the major odor components during the fermentation process.