Simple Management Changes Drastically Reduce Pig House Methane Emission in Combined Experimental and Modeling Study

Abstract

Reducing methane from livestock slurry is one of the quickest ways to counteract global warming. A straightforward strategy is to reduce slurry retention time inside pig houses by frequent transfer to outside storages, where temperature and therefore microbial activity are lower. We demonstrate three frequent slurry removal strategies in pig houses in a year-round continuous measurement campaign. Slurry funnels, slurry trays, and weekly flushing reduced slurry methane emission by 89, 81, and 53%, respectively. Slurry funnels and slurry trays reduced ammonia emission by 25–30%. An extended version of the anaerobic biodegradation model (ABM) was fitted and validated using barn measurements. It was then applied for predicting storage emission and shows that there is a risk of negating barn methane reductions due to increased emission from outside storage. Therefore, we recommend combining the removal strategies with anaerobic digestion pre-storage or storage mitigation technologies such as slurry acidification. However, even without storage mitigation technologies, predicted net methane reduction from pig houses and following outside storage was at least 30% for all slurry removal strategies.

Pig slurry organic matter transformation and methanogenesis at ambient storage temperatures

“…Particularly propionic acid concentrations >900 mg L −1 are inhibitory for methanogenic activity (Wang et al, 2009), and propionic acid exceeded ∼1.5 g L −1 throughout the incubation experiments at 10-15˚C and until day 63 at 20-25˚C. Similar or higher concentrations of VFA and propionic acid are normally observed in pig slurry (Dalby et al, 2023;Sommer et al, 2015). After ∼2, ∼5, and ∼10 weeks, CH 4 emission increased at 20˚C, 15˚C, and 10˚C, respectively (ρ = 0.3 for time-CH 4 production rate at all temperatures), but not at a rate comparable to that observed at 25˚C after 1 week (ρ = 0.37 for temp-CH 4 production rate).…”

“…It was suggested that degradable VS could be quantified in an aerobic assay (Petersen et al., 2016), but the method is tedious and does not address the fact that degradable VS consists of many OM sub‐pools that may degrade at completely different rates. At low temperatures, methanogenesis can be rate limiting (Dalby et al., 2023), necessitating modeling of microbial growth for the prediction of CH 4 emission in slurries at farms. The anaerobic biodegradation model includes the growth of methanogen groups but does not differentiate between VS sub‐pools due to limited knowledge of hydrolysis rates at low temperatures (Dalby et al., 2021a).…”

“…In pig manure, Methanoculleus, Methanobrevibacter , and Thermoplasmata are frequently reported (Barret et al., 2013; Dalby, Hansen, et al., 2020; Petersen et al., 2014). Tracing and linking their presence to diet and management could be key to explaining the large variation in reported CH 4 emissions from pig houses (Dalby et al., 2023; Külling et al., 2003; Velthof et al., 2005).…”

“…In pig manure, Methanoculleus, Methanobrevibacter, and Thermoplasmata are frequently reported (Barret et al, 2013;Petersen et al, 2014). Tracing and linking their presence to diet and management could be key to explaining the large variation in reported CH 4 emissions from pig houses (Dalby et al, 2023;Külling et al, 2003;Velthof et al, 2005). Herein, we measured degradation of individual OM components and CH 4 emission in fresh pig manure at 10-25˚C, which represents typical storage temperatures (in-house and outside) in northern regions.…”

Analysis of the Nexus between Structural and Climate Changes in EU Pig Farming

“…However, the identified list of best practices is not exhaustive, while the successful control and reduction in GHGEs depend on many factors. For example, academic research highlights the role of animal genetics [48], age and weight [16,34], activity and density [16,42], climate characteristics and season [16,45], building characteristics, including equipment, such as ventilation [16,49], frequency of manure/slurry removal from buildings [39,50], storage practices [46], emissions that depend on the particular manure utilisation techniques [15,46,51], etc. In fact, the GHGE potential in MSs depends on the multi-choice options on farms, and research that covers the aforementioned aspects and assists in the selection of the most effective and economically viable GHGE reduction alternatives remains critical for the development of sustainable pig farming systems.…”