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Title: A process-based model for cattle manure compost windrows: Model performance and application

item Bonifacio, Henry
item Rotz, Clarence - Al
item RICHARD, TOM - Pennsylvania State University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2017
Publication Date: 6/29/2017
Citation: Bonifacio, H.F., Rotz, C.A., Richard, T.L. 2017. A process-based model for cattle manure compost windrows: Model performance and application. Transactions of the ASABE. 60(3):893-913. doi: 10.13031/trans.12058.

Interpretive Summary: Composting of cattle manure creates carbon and nitrogen gaseous emissions to the environment, which can contribute to human health and environmental problems. USDA’s Integrated Farm System Model, a whole-farm model, was expanded to simulate changes in physical and nutrient properties of cattle manure during composting and to predict the gaseous pollutants emitted. The revised farm model appropriately predicted emissions of ammonia and greenhouse gases, and changes in moisture, temperature, and carbon and nitrogen contents measured for two experimental cattle manure compost windrows, one with turning and the other undisturbed. With the revised farm model, various management strategies of composting cattle manure can be assessed with respect to their overall impact on whole-farm emissions, along with other performance and economic aspects of cattle production. This provides a tool for evaluating and refining mitigation strategies that lead to more sustainable cattle production systems.

Technical Abstract: A model was developed and incorporated in the Integrated Farm System Model (IFSM, v.4.3) that simulates important processes occurring during windrow composting of manure. The model, documented in an accompanying paper, predicts changes in windrow properties and conditions and the resulting emissions of C and N. Our objective in this paper was to evaluate the performance of the compost windrow model. Model predictions were compared to published data from an independent cattle manure composting study that characterized static (no turning) and turned windrows composted over a 188-day period. Overall, the compost windrow model performed well in predicting C and N contents, gaseous emissions, and environmental conditions for both windrow types. The model did very well in simulating the turned windrow. Predicted and measured cumulative N losses were 55% and 57%, respectively, by day 99 of composting and 56% and 58%, respectively, by day 188. Except for cumulative N loss, the model also performed appropriately in simulating the static windrow. The higher predicted cumulative N loss (31% simulated vs. 19% measured) by day 99 was not surprising as the NH3 biofiltration effect of the finished compost cover on the actual static windrow was not modeled. After simulating the turning of the static windrow on day 99, predicted and measured cumulative N loss by day 188 were equal at 44%. With the compost windrow model as a component, IFSM can be used to evaluate gaseous emissions from composted manure as influenced by windrow management practices and environmental conditions along with other aspects of performance, environmental impact, and economics of cattle feeding operations. Simulating different composting strategies showed that addition of dry material to the cattle manure at the start of composting and turning of the manure windrow during composting produced a more stable organic soil amendment but caused greater carbon and nitrogen losses. IFSM provides a tool for evaluating management strategies to mitigate emissions and improve the sustainability of beef and dairy production systems, and the model now includes the option of manure composting.