Measuring greenhouse gas emissions from point sources in agriculture

Abstract

McGinn, S. M. 2006. Measuring greenhouse gas emissions from point sources in agriculture. Can. J. Soil Sci. 86: 355-371. Carbon dioxide, methane and nitrous oxide emissions from agricultural sources have a significant role in the overall enhancement of the global greenhouse gas (GHG) effect. In research, measurements of GHG emissions are made to improve upon emission factors used in national inventories, identify and promote mitigation practices, and drive policy on GHG emissions in agriculture. These measurements are fundamental to the process of better management of GHG emissions. There is a variety of measurement techniques used in GHG research depending on the measurement environment and available resources. Techniques that use chambers or micrometeorological measurements are commonly employed for calculating emissions of GHG from point sources in agriculture, such as livestock and manure-holding facilities. This review examines these techniques, their limitations, and discusses methods to quantify their accuracy and precision. Emerging techniques like the use of dispersion models provide opportunities to directly determine emissions from whole farms. A few micrometeorological techniques (integrated horizontal flux and mass difference) are ideal for point sources such as manure storage facilities. For smaller sources, chambers are still recommended. In designing GHG emission studies, employing more than one technique when measuring GHG emissions is recommended, as often differences can exist due to technique. Ideally, a controlled release of the target gas, and its recovery, should also be conducted to evaluate techniques prior to their application. Although many techniques are often sensitive enough to quantify mitigation practices, i.e., the relative change in emissions, it is more difficult to determine "true" emission factors as required for inventory work. It follows that the precision and accuracy of the techniques must accompany their application when estimating GHG emissions. De telles mesures sont essentielles à une meilleure gestion des rejets de GES. La recherche sur les GES fait appel à diverses méthodes de mesure, selon l'environnement et les ressources disponibles. Pour calculer les émissions des sources ponctuelles agricoles comme les éle-vages ou les installations de stockage du fumier, on recourt couramment à des méthodes fondées sur la cellule ou la micrométéorologie. L'article que voici fait le tour de ces techniques, en explique les limites et examine comment en établir l'exactitude et la précision. De nouvelles techniques tel l'usage de modèles de dispersion permettent de jauger directement les émis-sions d'exploitations entières. Quelques méthodes micrométéorologiques (flux horizontal intégré et variation de masse) conviennent à merveille aux sources ponctuelles comme les installations de stockage du fumier. Pour les sources plus petites, on recommande toujours l'emploi de cellules. Lorsqu'on entreprend une étude sur les émissions de GES, il est préférable de recourir à plusieurs techni...

Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture

“…The open-path laser method for whole-farm methane measurements is already in use in Canada (McGinn 2006 ;Flesch et al 2005Flesch et al , 2007, Australia McGinn et al 2008 ;Denmead 2008 ;Tomkins et al 2011 ), New Zealand (Laubach and Kelliher 2005 ) and China (Gao et al 2010 ). Methane concentration measurements are performed using one or more tuneable infrared diode lasers mounted on a programmable and motorized scanning unit (Tomkins et al 2011 ).…”

A Comparison of Methodologies for Measuring Methane Emissions from Ruminants

“…The open-path laser method for whole-farm methane measurements is already in use in Canada (McGinn 2006 ;Flesch et al 2005Flesch et al , 2007, Australia McGinn et al 2008 ;Denmead 2008 ;Tomkins et al 2011 ), New Zealand (Laubach and Kelliher 2005 ) and China (Gao et al 2010 ). Methane concentration measurements are performed using one or more tuneable infrared diode lasers mounted on a programmable and motorized scanning unit (Tomkins et al 2011 ).…”

Approaches to measuring fluxes of methane and nitrous oxide between landscapes and the atmosphere

“…It outlines the more common approaches available for measurement of land/atmosphere fluxes of CH 4 and N 2 O with particular focus on the challenges facing scientists in this region. Many approaches exist and have been described in depth in texts and review papers over the last decade, e.g., Matson and Harriss (1995), Hatfield and Baker (2005), McGinn (2006), Pattey et al (2006a, b). Each technique has its niche: chambers for small plots and very small gas fluxes; mass balance techniques for small bounded areas and heterogeneous sources; newly emerging backward Lagrangian stochastic (bLs) dispersion techniques using point or open-path line-averaged concentrations for point, line or small, well-defined areal sources; and eddy covariance, eddy accumulation and fluxgradient methods for larger landscapes with homogeneous surface sources.…”