A process-based model for cattle manure compost windrows: Part 1. model description

Composting is an alternative management practice for handling and storing manure in intensive cattle production systems. With composting, cattle manure is converted into a soil amendment with improved nutrient and physical properties and is easier to handle. Despite its benefits, composting can produce large amounts of gaseous carbon (C) and nitrogen (N) emissions that include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ammonia (NH3). A processbased model for cattle manure compost windrows was developed and incorporated into the Integrated Farm System Model (IFSM, v. 4.3), a whole-farm simulation model of crop, dairy, and beef production systems. Designed to simulate the different processes that influence C and N balances in windrows, the compost windrow model predicts changes in C (organic C, microbial C) and N (organic N, microbial N, ammonium (NH4 +-N), nitrate (NO3 -N)) contents in the windrow; CO2, CH4, N2O, and NH3 emissions throughout composting; and corresponding C and N losses. To increase its accuracy in simulating the different processes occurring during composting, the compost windrow model was also designed to predict environmental conditions within windrows, which include moisture content, temperature, and oxygen availability, and changes in windrow material physical properties, such as bulk and particle densities. Modeling routines and relationships of the compost windrow model are described. Evaluation of its performance in predicting windrow environmental conditions, physical andchemical properties, and gaseous emissions is documented in an accompanying article.