Effects of composting swine manure on nutrients and estrogens

Authors: DERBY, NATHAN - North Dakota State University; Hakk, Heldur; CASEY, FRANCIS - North Dakota State University; DESUTTER, THOMAS - North Dakota State University

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2010
Publication Date: 2/10/2011
Citation: Derby, N.E., Hakk, H., Casey, F.X.M., Desutter, T.M. 2011. Effects of composting swine manure on nutrients and estrogens. Soil Science. 176(2):91-98.

Interpretive Summary: Direct application of raw manure to fields as a fertilizer can contribute adverse odors and other environmental concerns from administered antibiotics, for instance. In addition, raw manures contain concentrations of reproductive hormones that are known endocrine disruptors. Composting manure, in which aerobic microorganisms convert organic compounds into more stable forms, may also reduce hormone levels. Two piles of swine manure with corn stalk bedding were monitored for internal temperature and sampled periodically for nitrogen, phosphorus, potassium, pH, electrical conductivity, and the hormones 17ß-estradiol (E2) and estrone (E1). A heated, aerobic compost pile was mixed periodically resulting in a rapid temperature increase within the pile to the thermophilic range (40-60°C) after each mixing. A static manure pile was not mixed, and the internal temperature stayed very close to ambient. After 92d, the compost resembled a soil-like material with very little odor, while the static pile maintained much of its original physical characteristics. The compost had a pH closer to neutral, a lower electrical conductivity, and slightly lower total N content than the static manure pile. Both piles had greatly reduced ammonia concentrations. E2 concentrations did not decline, but rather fluctuated with time, and were much lower than E1 concentrations, which were initially very high and did decrease during the study. Therefore, static manure storage was just as effective in reducing estrogenicity due to E2 and E1 when compared to aerobic composting, in that estrogenicity was reduced by 74% in the static manure pile and 79% in the composted pile.

Technical Abstract: Direct application of raw manure to fields as a soil amendment can contribute ammonia, pathogens, and volatile organic compounds at concentrations that may give rise to adverse odors and environmental concerns. In addition, raw manures can contain concentrations of reproductive hormones that could impact the endocrine systems of sensitive organisms. Composting manure, in which aerobic microorganisms destroy pathogens and convert organic compounds into more stable forms, may reduce its potentially harmful effects. Two piles of swine manure with bedding (corn stalks) were monitored for internal temperature and sampled periodically for inorganic and total N, P, K, pH, EC, and the hormones 17ß-estradiol (E2) and estrone (E1). A compost pile was mixed periodically throughout the study, resulting in temperature increases within the pile to the thermophilic range (40-60°C) after each mixing. A static manure pile was not mixed and the temperature of the manure stayed very close to ambient throughout. After 92d, the compost resembled a humus-like material with very little odor, while the static pile had maintained much of its original physical characteristics. The compost had a pH closer to neutral, a lower electrical conductivity, and slightly lower total N content than the static manure pile. Both piles had greatly reduced ammonia concentrations. E2 fluctuated throughout the study, but was much lower than E1 concentrations, which were initially very high but decreased during the study. Static manure storage was just as effective in reducing estrogenicity due to E2 and E1 when compared to aerobic composting, in that it was reduced by 74% in the static manure pile and 79% in the composted pile.