Evaluation of Potential Treatments to Reduce Foaming from Swine Manures

Abstract

<p>Foam formation on the surface of deep pit swine manure storages poses a safety concern for both humans and animals. Although current research has provided significant insight into both the causes and mechanisms of foam formation, thus far few practical, easily implemented treatment practices are available to help mitigate manure foaming. Thus, the purpose of these experiments were to better understand the causes of foam formation, the mechanisms of foam development and stabilization, and determine the effectiveness of Narasin, Manure Magic, and other physical, chemical, and biological manure treatments to reduce foaming in deep pit swine manure storages. Our first experiment was designed to evaluate if different feed components induced foaming properties in the manure and a follow-up incubation study to evaluate if there were difference preferences for conversion to methane from carbohydrate, protein, and fats between foaming and nonfoaming manures. In general, our results showed that easily degradable organic carbon induced microbial activity and results in grater foaming capacity and foam stability, but the effect was generally short lived. In terms of substrate preference or results showed that foaming manures showed high affinity for all carbon substrates tested but no difference between substrates was seen. Our second study focused on if manure additives could alter either the methane production rate, foaming capacity, or foam stability. These results gave important insights into the mechanisms of foam formation in that the inclusion of tannin instantly and significantly caused induced foam stability, while the decomposition of soybean oil induced foaming after several weeks. In particular, these results showed that fine particles that interact with proteins can induce stability within the foam and appeared to demonstrate that similar types of compounds can be synthesized by the decomposition of oils. Our last two experiments focused specifically on developing and evaluating foam mitigation strategies. These tests were conducted at the field- and lab-scale; our results failed to show significant difference in the labscale, presumably because microbial activity (based on methane production rates) was low for all tests. At the field-scale experiment we found that treatment with Narasin or Manure Magic reduced both methane production rate and foam stability. Our results indicated that Narasin reduced volatile solids destruction while Manure Magic increased solids destruction. Finally, microbial sequencing data indicated that our Manure Magic treatment significantly altered the microbial community away from that of our foaming control barn, but not when the manure wasn’t foaming.</p>