Review on greenhouse gas emissions from pig houses: Production of carbon dioxide, methane and nitrous oxide by animals and manure

peer reviewed ; The environmental impacts of livestock production are attracting increasing attention, especially the emission of greenhouse gases (GHGs). Currently, pork is the most widely consumed meat product in the world, and its production is expected to grow in the next few decades. This paper deals with the production of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) by animals and by manure from pig buildings, with a focus on the influence of rearing techniques and nutrition. GHG emissions in piggeries originate from animals through CO2 exhalation and CH4 enteric fermentation, and from manure through the release of CO2, CH4 and N2O. The level of the CO2 exhalation (E-CO2, pig) depends on the physiological stage, the body weight (BW), the production level and the feed intake of the animals concerned. Enteric CH4 (E-CH4, pig) is principally related to dietary fibre intake and the fermentative capacity of the pig’s hindgut. Based on a review of the literature, the following equations are proposed in order to estimate E-CO2, pig (in kg day_1) and E-CH4,pig (in g day_1) for fattening pigs: E-CO2, pig = 0.136 _ BW0.573; E-CH4,pig = 0.012 _ dRes; with BW (in kg) and dRes for digestible residues (in g day_1). Numerous pathways are responsible for GHG production in manure. In addition, the microbial, physical and chemical properties of manure interact and modulate the level of emissions. Influencing factors for removal systems for both liquid and solid fractions of manure have been investigated. A large range of parameters showing an impact on the level of GHG production from pig houses has been reported. However, few of these can be considered unquestionably as GHG mitigation techniques because some strategies have shown contradictory effects depending on the gas, the circumstances and the study. Nevertheless, frequent manure removal seems to be an efficient means to reduce concurrently CO2-, CH4- and N2O-emissions from pig buildings for both slatted and bedded floor systems. Manure removal ...