Improved Chamber Systems for Rapid, Real-Time Nitrous Oxide Emissions from Manure and Soil

Abstract

Abstract. Nitrous oxide (N2O) emission rates have traditionally been measured using non-flow-through (NFT), non-steady-state (NSS) chambers, which rely on measuring the increase in N2O concentration in the sealed chamber headspace over time. These flux measurements are very labor- and time-intensive, requiring three to four gas samples collected over a 30 to 60 min period, followed by laboratory N2O measurement with a gas chromatograph (GC) and subsequent flux rate calculation. The objective of this research was to develop and evaluate improved, real-time flux chamber designs that rapidly quantify N2O emissions from manure and soil. The first chamber system consisted of six square 0.95 m2 chamber pans. The chamber pans were mounted on a rail system to facilitate controlled indoor/outdoor laboratory research at a pilot scale. An aluminum lid was moved among the chamber pans. A second portable chamber system with a circular footprint (0.49 m internal dia.) was designed for use in field measurements. With both systems, N2O concentrations were measured each second with 0.1 ppb resolution by recirculating sample air through a real-time continuous N2O analyzer with return flow into the recirculating-flow-through (RFT-NSS) chamber. Performance and observational data are presented for different chamber vent designs, sealing mechanisms between the chamber pan and lid, recirculation pumps, and presence/absence of an internal fan that mixes headspace air within the sealed chamber. As examples of the repeatability and precision of the methodology, ten consecutive flux measurements were obtained using moist manure (32.6% wet basis water content, WCWB) within a 15 min period in which chamber pans were fitted with lids for 60 s and removed for 30 s. The mean calculated N2O flux was 43.08 ±0.89 mg N2O m-2 h-1. Using dry manure (WCWB = 10.8%), five consecutive flux measurements showed a very low, but consistent, flux that averaged 0.025 ±0.0016 mg N2O m-2 h-1. Five case study experiments demonstrate the usefulness of these chamber systems and highlight discoveries and lessons learned to enhance future research efforts. Major discoveries and observations include: (1) installation of a small internal fan within the chamber lids decreased N2O fluctuation over small time periods, allowing precise measurement of manure N2O fluxes as low as 0.0073 mg N2O m-2 h-1 during a 60 s measurement period; (2) two distinct N2O peaks were observed at 1 and 21 d following the addition of water to manure (initial WCWB = 32.6%), with the second peak accounting for 83% of the total N2O emitted over 45 d; and (3) there was notable diurnal variation in N2O fluxes due to temperature variation, even when the manure was dry (WCWB = 10.8%). These flux chamber systems proved to be more rapid, precise, and repeatable than traditional flux chamber methods and offer promise for future greenhouse gas emissions research on manure and soil. Keywords: Cattle, Chamber, Diurnal, Fan, Feedlot, Greenhouse gas, Manure, Precision.

Nitrous Oxide from Beef Cattle Manure: Effects of Temperature, Water Addition and Manure Properties on Denitrification and Nitrification

“…From Day 1 to 21, the five chambers were maintained at 1 Emissions were baseline until H2O was added, and then a large peak was observed in all chambers: (a) Days 1-20, and (b) Days 20-59, where temperatures were increased in three chambers and a second, longer-term N2O peak was observed that was related to temperature. Source: Parker et al [3].…”

“…Selected physicochemical properties of the manures from the two depths, five chambers, and six sampling dates are presented in Table 1, along with N 2 O emissions data from Parker et al [3]. Manure DM content after both artificial rainfall events ranged from 63% to 82% at 0-5 cm and 66% to 85% at 5-10 cm.…”

“…Beef cattle feedyards produce nitrous oxide (N 2 O) from manure [1][2][3][4][5][6]. Nitrous oxide is a potent greenhouse gas (GHG) implicated in climate change due to a global warming potential (GWP) of 265-298 carbon dioxide equivalent (CO 2 e).…”

“…Feedyard N 2 O emissions are highly variable over both space and time [4,5]. This variability has been linked to temperature [2,4,9], H 2 O content [2][3][4]10], and manure characteristics [1,4,[11][12][13]. Unfortunately, the relationships observed between these variables and N 2 O losses have been inconsistent, likely due to differences in manure physicochemical properties and treatment effects among studies.…”

Greenhouse Gas Emissions from Beef Feedlot Surface Materials as Affected by Diet, Moisture, Temperature, and Time

“…(table 2). Recently, Parker et al (2017aParker et al ( , 2017b) conducted studies to quantify N 2 O emissions after a rainfall event on surface materials from simulated open-lot beef cattle pens. Their study used 1 m × 1 m × 0.89 m deep steel pans that were repacked with FSM collected from a commercial feedlot in Deaf Smith County, Texas.…”