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Title: An evaluation of the physiochemical and biological characteristics of foaming swine manure

item VAN WEELDEN, MARK - Iowa State University
item ANDERSEN, DANIEL - Iowa State University
item Trabue, Steven
item Kerr, Brian
item ROSTENTRATER, KURT - Iowa State University
item PEPPLE, LAURA - University Of Illinois

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2015
Publication Date: 12/1/2015
Citation: Van Weelden, M.B., Andersen, D., Trabue, S.L., Kerr, B.J., Rostentrater, K.A., Pepple, L.M. 2015. An evaluation of the physiochemical and biological characteristics of foaming swine manure. Transactions of the ASABE. 58:1299-1307.

Interpretive Summary: Foam accumulation in the manure of deep-pit swine barns is an increasing concern for swine producers because of the logistical and safety-related problems it creates. Current thought on foaming is that its associated with a three-phase model containing the following elements: 1) a liquid phase in which a compound in the manure (known as a surfactant) changes the manure in such a way that it increases the chances of gas bubbles being trapped within its confines; 2) a solid phase that consists of particles that create stability within the foam so bubbles do not collapse and drain rapidly back into the manure; and 3) a gas phase known as biogas (i.e., methane and carbon dioxide) that expands the foam layer that is controlled by microorganisms within the manure. Samples of swine manure were collected from 58 swine production facilities in Iowa with varying levels of foam accumulation over a 13-month period. No liquid was detected that could change the manure to trap bubbles to explain why foaming was occurring. Instead liquids in the manure were coming together and staying together to create the foam. However, these liquids do not normally associate with each other due to their chemical properties. It is believed a different compound in the manure enables the two liquids to come together creating the stable foam. Foaming manures had significantly higher particle concentrations than non-foaming manures and these particles are thought to limit drainage of liquid from the foam layer, thereby increasing the stability of the foam. Methane production rates were significantly higher in the foaming manure compared to non-foaming manure. While data from this study did not support the three-phase model with a single compound changing the manure, the data did support the three-phase model with an emulsion as the cause of foam. Information in this report will be of value for growers, animal scientists, and engineers who are working on manure management systems.

Technical Abstract: Incorporation of dedicated herbaceous energy crops into row crop landscapes is a promising means to supply an expanding biofuel industry while increasing biomass yields, benefiting soil and water quality, and increasing biodiversity. Despite these positive traits, energy crops remain largely unaccepted due to concerns over their practicality and cost of implementation. This paper presents a case study on Hardin County, Iowa, to demonstrate how subfield decision making can be used to target candidate areas for conversion to energy crop production. The strategy presented integrates switchgrass (Panicum virgatum L.) into subfield landscape positions where corn (Zea mays L.) grain is modeled to operate at a net economic loss. The results of this analysis show that switchgrass integration has the potential to increase sustainable biomass production from 48 to 99% (depending on the rigor of conservation practices applied to corn stover collection) while also improving field-level profitability. Candidate land area is highly sensitive to grain price (0.18 to 0.26 US$ kg-1) and dependent on the acceptable net profit for corn production (ranging from 0 to -1,000 US$ ha-1). This work presents the case that switchgrass can be economically implemented into row crop production landscapes when management decisions are applied at a subfield scale and compete against areas of the field operating at a negative net profit.