Methane production in ruminant animals

Agriculture is a significant source of GHGs globally and ruminant livestock animals are one of the largest contributors to these emissions, responsible for an estimated 14% of GHGs (CH4 and N2O combined) worldwide. A large portion of GHG fluxes from agricultural activities is related to CH4 emissions from ruminants. Both direct and indirect methods are available. Direct methods include enclosure techniques, artificial (e.g. SF6) or natural (e.g. CO2) tracer techniques, and micrometeorological methods using open-path lasers. Under the indirect methods, emission mechanisms are understood, where the CH4 emission potential is estimated based on the substrate characteristics and the digestibility (i.e. from volatile fatty acids). These approximate methods are useful if no direct measurement is possible. The different systems used to quantify these emission potentials are presented in this chapter. Also, CH4 from animal waste (slurry, urine, dung) is an important source: methods pertaining to measuring GHG potential from these sources are included

Determination of the absolute accuracy of UK chamber facilities used in measuring methane emissions from livestock

Respiration chambers are one of the primary sources of data on methane emissions from livestock. This paper describes the results from a coordinated set of chamber validation experiments which establishes the absolute accuracy of the methane emission rates measured by the chambers, and for the first time provides metrological traceability to international standards, assesses the impact of both analyser and chamber response times on measurement uncertainty and establishes direct comparability between measurements made across different facilities with a wide range of chamber designs. As a result of the validation exercise the estimated combined uncertainty associated with the overall capability across all facilities reduced from 25.7% (k = 2, 95% confidence) before the validation to 2.1% (k = 2, 95% confidence) when the validation results are applied to the facilities’ data

Determining the potential of a LoRa technology approach to measure methane emission in sheep

Thesis (MScAgric)--Stellenbosch University, 2022.ENGLISH ABSTRACT: As a result of their contribution to global methane (CH4) emissions, ruminants are under scrutiny, with research focusing on quantifying CH4 production to contribute to the development of CH4 mitigation strategies. Previous studies have quantified CH4 emissions from ruminants; however, these studies were carried out under controlled conditions, and therefore the results cannot be extrapolated to animals under extensive (free range) production conditions. Despite the various studies on CH4 emissions in ruminants, there is a lack of data regarding CH4 emissions in sheep under extensive production conditions. Agriculture as an industry is in a unique state of transformation, as new technologies provide the opportunity to create automated and data-driven agricultural practices. A prominent technology available to the industry is LoRa (Long Range), a sub-technology of the ‘Internet of Things’ (IoT). LoRa technology presents an opportunity for the development of a low-power, affordable, and simple CH4 measurement technique, which can measure CH4 emissions with little to no human input. This study aimed to determine the potential of a novel LoRa CH4 detection unit to measure CH4 emissions in sheep under South African grazing conditions. The CH4 emissions of ten intact Dohne Merino rams grazing kikuyu pasture were determined using the LoRa CH4 detection units, a hand-held Laser methane detector, and an Australian-adapted Tier 2 approach. Three LoRa CH4 detection units were installed in a 0.07 ha camp, and set to take CH4 measurements for ten days, i.e. two days where background CH4 concentrations were measured, and eight days where sheep CH4 emissions were recorded. The LMD was used to take daily enteric CH4 emission measurements from each ram for ten days. The objectives of this study included determining the potential of the LoRa CH4 detection units to measure sheep CH4 emissions under grazing conditions, and to compare emissions measured by the LoRa devices with that recorded by a laser methane detector (LMD). Both devices were used to establish diurnal CH4 emissions in sheep, and to compare the recorded levels with the calculated IPCC Tier 2 levels for sheep under grazing conditions. The effect of ambient conditions on the CH4 concentrations measured by the LoRa detection units was investigated. Relative humidity had a significant positive correlation with the CH4 concentrations measured by the LoRa detection units, while air temperature, wind speed and solar radiation had a negative correlation with the CH4 concentrations measured by the LoRa detection units. Significant correlations were reported for Device 3 only. The LoRa detection units and LMD compared favourably in terms of the characterization of the diurnal fluctuation in CH4 concentration. The CH4 levels measured per ram by LoRa Devices 1 (24.0 ppm) and Device 2 (52.9 ppm) were significantly higher than the levels detected by the LMD (13.9 ppm), while the CH4 levels measured per ram by LoRa Device 3 (11.9 ppm) were similar to the LMD detected levels. The IPCC Tier 2 approach (10.3 g/day) underestimated the CH4 emissions per ram compared to the LMD (27.6 g/day). It was not possible to compare the CH4 emissions data obtained using the LoRa technology and Tier 2 approach in this study as their emission estimates had different units (ppm versus g/day, respectively). The LoRa CH4 detection device developed for this study, has the potential to be a low-cost and practical measurement technique to quantify CH4 emissions from sheep under grazing conditions, limited to use in small, controlled camps. Once the device design is refined to overcome the few limitations identified in this study, the LoRa technology can assist with the generation of sheep CH4 emission data under various production conditions to improve emission inventories and verify mitigation strategies, on a national and international scale.AFRIKAANSE OPSOMMING: As gevolg van hul bydrae tot globale metaanvrystellings (CH4) word herkouers onder die loep geneem, met navorsing wat fokus op die kwantifisering van CH4-produksie om by te dra tot die ontwikkeling van strategieë wat sal bydra tot verlaging van CH4 geproduseer deur herkouers. Vorige studies het CH4-emissies van herkouers gekwantifiseer; hierdie studies is egter onder beheerde toestande uitgevoer en daarom kan die resultate nie geëkstrapoleer word na diere onder ekstensiewe (vrylopende) produksietoestande nie. Ten spyte van die verskeie studies oor CH4 vrystellings by herkouers, is daar 'n gebrek aan data rakende CH4 emissies by skape onder ekstensiewe produksietoestande. Landbou as 'n bedryf is in 'n unieke toestand van transformasie, aangesien nuwe tegnologie die geleentheid bied om geoutomatiseerde en data-gedrewe landboupraktyke te skep. 'n Prominente tegnologie wat vir die bedryf beskikbaar is, is LoRa (Long Range), 'n sub-tegnologie van die 'Internet of Things' (IoT). LoRa tegnologie bied 'n geleentheid vir die ontwikkeling van 'n lae-krag, bekostigbare en eenvoudige CH4 metingstegniek, wat CH4 emissies kan meet met minimale menslike insette. Hierdie studie het ten doel gehad om die potensiaal van 'n nuwe LoRa CH4 metingseenheid te bepaal om CH4 emissies in skape onder Suid-Afrikaanse weidingstoestande te meet. Die CH4 vrystellings van tien intakte Dohne Merino ramme wat kikoejoe weiding bewei het, is bepaal deur gebruik te maak van die LoRa CH4 metingseenhede, 'n laser-metaan metingtoestel (LMD) en 'n Australies- aangepaste Vlak 2-benadering. Drie LoRa CH4 metingseenhede is in 'n kamp van 0,07 ha geïnstalleer en gestel om CH4 metings vir tien dae te neem, dit wil sê twee dae waar agtergrond CH4 konsentrasies gemeet is, en agt dae waar skaap CH4 vrystellings aangeteken is. Die LMD is gebruik om daaglikse enteriese CH4 emissiemetings van elke ram vir tien dae te neem. Die doelwitte van hierdie studie het ingesluit die bepaling van die potensiaal van die LoRa CH4 metingseenhede om skaap CH4 vrystellings onder weidingstoestande te meet, en om emissies gemeet deur die LoRa eenhede te vergelyk met dié wat deur 'n LMD aangeteken is. Beide toestelle is gebruik om daaglikse CH4 emissies by skape vas te stel, en om die aangetekende vlakke te vergelyk met die berekende IPCC Vlak 2-vlakke vir skape onder weidingstoestande. Die effek van omgewingstoestande op die CH4 konsentrasies gemeet deur die LoRa metingseenhede is ondersoek. Relatiewe humiditeit het 'n beduidende positiewe korrelasie gehad met die CH4 konsentrasies gemeet deur die LoRa metingseenhede, terwyl lugtemperatuur, windspoed en sonstraling 'n negatiewe korrelasie gehad het met die CH4 konsentrasies gemeet deur die LoRa metingseenhede. Beduidende korrelasies is slegs vir Toestel 3 aangemeld. Die LoRa metingseenhede en LMD het gunstig vergelyk in terme van die karakterisering van die daaglikse fluktuasie in CH4 konsentrasie. Die CH4 vlakke gemeet per ram deur LoRa metingseenheid 1 (24.0 dpm) en metingseenheid 2 (52.9 dpm) was aansienlik hoër as die vlakke wat deur die LMD opgespoor is (13.9 dpm), terwyl die CH4 vlakke gemeet per ram deur LoRa metingseenheid 3 (11.9 dpm) ) soortgelyk was aan die LMD-bespeurde vlakke. Die IPCC Vlak 2-benadering (10,3 g/dag) het die CH4 emissies per ram onderskat in vergelyking met die LMD (27,6 g/dag). Dit was nie moontlik om die CH4 emissiedata wat verkry is met behulp van die LoRa tegnologie en Vlak 2-benadering in hierdie studie te vergelyk nie, aangesien hul emissieskattings verskillende eenhede gehad het (onderskeidelik dpm versus g/dag). Die LoRa CH4 metingstoestel wat vir hierdie studie ontwikkel is, het die potensiaal om 'n lae-koste en praktiese metingstegniek te wees om CH4 emissies van skape onder weidingstoestande te kwantifiseer, beperk tot gebruik in klein, beheerde kampe. Sodra die toestel-ontwerp verfyn is om die paar beperkings wat in hierdie studie geïdentifiseer is, te oorkom, kan die LoRa tegnologie help met die generering van skape CH4 emissiedata onder verskeie produksietoestande om emissie-databasisse te verbeter en strategieë om metaanproduksie te verlaag te verifieer, op nasionale en internasionale skaal.Master

Quantifying daily methane production of beef cattle from multiple short-term measures using the GreenFeed system

On-farm CH₄ emissions have been identified as the largest contributors to the carbon footprint of livestock production systems. A requirement to quantify on-farm mitigation under commercial production conditions and a desire to establish the phenotype of thousands of ruminants for breeding programs, has fueled the development of techniques to estimate daily methane production (DMP) from short-term measures of methane concentration or methane flux.The accuracy, precision and applicability of these methods has been largely untested and forms the susbtance of this thesis. In assessing the accuracy of short-term emissions measures to estimate DMP, a high level of concordance was observed between DMP measured over 24h in a respiration chamber (RC) and estimated from multiple short-term measurement estimates using the GreenFeed Emission Monitoring system (GEM). Three independent experiments comparing DMP confirmed that estimates between methods differ by 5% to 8% (P>0.05). This implies that multiple short-term measures of emission rates are complementary to and consistent with respiration chamber-derived measures, providing capability to measure a greater number of animals, potentially in their production environment over extended periods of time. Methane yields (MY; g CH₄/kg DMI) were also derived based on multiple short-term emission measures, with results consistently within 10% of those calculated based on 24h RC data. The overall MY of animals consuming roughages was 21.8g CH₄/kg DMI using GEM data, in keeping with the 22.3g CH₄/kg DMI average in the literature. That implies that GEM units can not only accurately estimate DMP of cattle but also support accurate MY estimates that can be used in quantifying livestock emissions for national greenhouse inventory calculations

Towards Sustainable Livestock Production: Estimation of Methane Emissions and Dietary Interventions for Mitigation

The increasing need for sustainable livestock production demands more research in the field of greenhouse gas (GHG), particularly methane (CH4), measurement and mitigation. Dietary interventions, management, and biotechnological strategies to reduce the environmental impacts and economic implications of enteric CH4 emissions are needed. While the use of biotechnological interventions and management strategies can be challenging on a routine basis, feed additive supplementation appears to be the most researched, developed, and ready to use strategy to mitigate enteric CH4 emissions. This paper discusses various recently developed feeding strategies to reduce enteric CH4 emissions in livestock. Additionally, the manuscript reviews various technologies developed for CH4 estimation since the accurate and reliable estimation of CH4 emissions can be a limiting step in the development and adoption of any mitigation strategy