Characterizing manure drying practices in Iowa commercial egg production facilities

Abstract

As laying hen housing styles change throughout Iowa to meet legislative and consumer demands, drying of manure can be economically expensive and energy intensive. With about 50% of total electricity consumption and about 60% of annual electricity costs attributed to manure drying, this represents an opportunity for producers to decrease production costs while reducing electrical grid strain. To understand current practices and potential opportunities, survey data were collected from 34 Iowa egg producers in fall 2020, representing egg-laying ( n = 50), breeding ( n = 30), and rearing ( n = 20) facilities. Average (± SD) reported number of weekly manure removal events was 2.2 ± 0.50 for all housing styles with 2.4 ± 0.09 for cage-free aviaries and 2.2 ± 0.58 for conventional cage. Reported daily manure blower operation was 14.2 ± 11.0 h/d for all facilities, with cage-free aviaries operating blowers for 10.0 ± 11.8 h/d while conventional cage houses operated blowers for 15.1 ±10.8 h/d. On a per thousand bird basis, reported overall energy usage was 10.1 kWh per day, 308 kWh per month, and 3.7 MWh per year. Energy costs per thousand birds were US$0.81 per day, US$25 per month, and US$296 per year. Respondents from 16 facilities reported their facility did not have smart meters (i.e., monitoring voltage, current, power factor, and energy consumption), while 10 reported smart meter usage and 5 reported they were unsure. Managers were no more likely to be aware of facility peak demand or track peak demand regardless of whether the facility had a smart meter (aware: P = 0.09; track: P = 0.26). Interestingly, all 21 respondents reported being aware of peak demand incentives; however, only 9 (43%) respondents indicated their facilities participate in these incentives. These results provide a characterization of manure drying practices and energy usage in Iowa egg production facilities. There are opportunities to impact the manure drying process through control strategies that optimize blower energy based on environmental conditions, target manure moisture content, and peak demand periods.