Mitigating Ammonia and PM Generation of Cage-Free Henhouse Litter with Solid Additive and Liquid Spray

Abstract

A number of chain restaurants, retailers, and grocers in the U.S. have pledged to source only cage-free (CF) eggs in the foreseeable future (e.g., by 2025) due to marketing reasons or concerns over animal welfare. However, CF housing has some inherent challenges, and a predominant one is poor air quality, i.e., ammonia gas (NH3) and particulate matter (PM), and increased emissions. Spraying a liquid agent such as electrolyzed water (EW) can effectively suppress PM generation of CF henhouse litter. However, liquid spray can enhance NH3 generation because it increases the litter moisture content (LMC). Application of acidic liquid to the litter would help control NH3 while suppressing PM, but con-cerns arise about the potential corrosive effect of acidic liquid on housing equipment. To overcome this dilemma, this study evaluated the effect of applying PLT, a commercial poultry litter additive (LA), on NH3 emissions of CF hen litter while spraying it with neutral EW (NEW) at a rate of 25 mL kg-1 dry litter d-1. The PLT application rates were 0.3, 0.6, and 0.9 kg m-2, denoted as Low-LA, Med-LA, and High-LA, respectively. CF litter was placed inside dynamic emission chambers and automatically stirred to mimic hen scratching. PLT was topically applied onto the litter on day 1; NEW was sprayed daily for 11 d, followed by a 3 d non-spray period (i.e., 14 d per trial); and each regimen was replicated four times. The ammonia emission rate (ER) of the control (no LA), Low-LA, Med-LA, and High-LA regimens (mean SE) was, respectively, 0.76 0.05, 0.55 0.06, 0.37 0.04, and 0.16 0.02 g kg-1 dry litter d-1, i.e., 28% to 79% reduction by the treatments. The NH3 reduction efficiency was linearly proportional to the PLT application rate, with higher application rate resulting in lower litter pH (p < 0.05). At the end of each trial (d14), the Med-LA and High-LA regimens still showed relatively low NH3 emissions, suggesting the need for a longer measurement period in future studies. The NEW spray increased LMC by up to 60% after 11 once-a-day sprays, which reduced PM2.5, PM10, and TSP levels from 3.83, 6.39, and 7 mg m-3 to 0.07, 0.14, and 0.15 mg m-3, respectively. After a 3 d spray suspension, the PM levels rebounded to 0.72, 1.02, and 1.12 mg m-3 for PM2.5, PM10, and TSP, respectively, due to decreased LMC. Field verification of the mitigation efficacy and an economic assessment of the method are warranted.

Evaluation of nesting behavior of individual laying hens in an enriched colony housing by using RFID technology

“…At the same time, welfare standards of hens continue to elevate, and some of the criteria (e.g., allocation of enrichment, housing systems, and management practices) are subject to debate [1][2][3][4] . Transitioning of egg production systems from conventional cage to alternative housing (e.g., enriched colony, aviary cage-free) is increasingly occurring in various parts of the world, especially in Europe and the United States, to meet animal welfare requirements or legislation [5,6] .…”

&lt;i&gt;Mitigating Particulate Matter Emissions of a Commercial Cage-free Aviary Hen House&lt;/i&gt;

“…1a) so that other types of liquid agents (e.g., electrolyzed water or slightly acidic electrolyzed water) may be sprayed as well in the future. During the lab study that preceded the field verification test, a spray dosage of 125 mL m -2 corresponding to 1 cm litter depth had been shown to achieve over 50% PM reduction without causing NH3 problem (Chai et al, 2017(Chai et al, , 2018a. This spray dosage was used as the base and adjusted according to the litter depth (table 1).…”

“…Application of low pH liquid to the litter would help control PM and ammonia at the same time, but concerns arise about the potential corrosive effect of acidic liquid on the housing equipment. Chai et al (2018a) conducted research in dynamic emission chambers by spraying neutral electrolyzed water (pH=7-8) at 125 mL m -2 (corresponding to litter depth of 1 cm) and applying PLT TM litter additive at 30 g per kg dry litter onto CF henhouse-collected litter, which reduced the generation of PM by 60-70% and NH3 by 70-80%, respectively. Properly controlling the water spray dosage could maintain over 50% PM reduction efficiency without causing NH3 issue.…”

Mitigating Particulate Matter Generation in a Commercial Cage-Free Hen House

“…The authors reported reduction of 60-70% in PM generation and 70-80% in NH3 generation. Chai et al (2018a) also showed that properly controlling water spray dosage could provide >60% PM reduction efficiency without causing an increase in NH3 concentrations.…”

“…However, concerns exist about the potential corrosive effect of acidic liquid on housing equipment (Chai et al, 2017). Chai et al (2018a) conducted a lab-scale study that involved spraying neutral electrolyzed water (pH=7-8) at 125 mL m -2 (at 1 cm litter depth) and applying poultry litter additive/treatment (PLT, sodium bisulfate, NaHSO4) at 30 g per kg dry litter onto CF henhouse litter. The authors reported reduction of 60-70% in PM generation and 70-80% in NH3 generation.…”