Farm-scale Methane Fluxes - ETH - Grassland Science Project

The release of the IPCC's Fourth Climate Assessment Report has once more drawn the public attention to the important role that agriculture plays in the global greenhouse gas budgets, namely in the case of CH4 and N2O. In Switzerland, 80.5% of all national CH4 emissions stem from the agricultural sector (year 2007 values).
However, these numbers so far lack direct experimental validation in the field and are based on expert knowledge. We thus propose to investigate the CH4 emission processes leading to a clear increase in CH4 concentrations within the nocturnal atmospheric boundary layer. This project will thus aim at validating CH4 emissions at the farm scale as a first step towards a validation at the national scale. We hypothesize that the diurnal cycle in CH4 concentration is the combination of the local surface exchange of CH4 with oxidation by the soil if it is unsaturated or emissions from the soil if saturated, plus a much larger component attributable to emissions from cattle (ruminants). Our specific aim is to quantify CH4 emissions at the farm scale (0.5-5km2) of the ETH Research Station Chamau and relate this to estimates reported in the Swiss National Inventory Report under the Kyoto Protocol. We plan to employ a boundary-layer budgeting method (BLBM) by focusing on the nocturnal boundary layer conditions where steadily increasing CH4 concentrations can be observed during most of the nights. To achieve this, we need the following four components of our experiment: - Eddy covariance flux and concentration measurements to quantify the surface exchange of CH4 (soil production or consumption); - Vertical CH4 concentration profiles to know the vertical distribution of CH4 in the incompletely mixed stable nocturnal boundary layer (NBL), to determine the NBL height and its temporal evolution which are essential information required by the BLBM; - Spatial variation of near-surface CH4 concentrations to address the question how spatially representative our near-surface CH4 concentration measurements actually are. Measurements of stable isotopes, in particular d13C ratios in CH4 will provide additional information about the processes responsible for the CH4 fluxes obtained via the BLBM aproach. Our project will contribute to develop and test a potentially useful method for validating CH4 emissions at the farm scale and larger scales. This project will contribute to our scientific understanding by bridging the spatial and temporal gap in our efforts to quantify and validate CH4 emission estimates at the farm scale to regional scale.

Context

The release of the IPCC's Fourth Climate Assessment Report has once more drawn the public attention to the important role that agriculture plays in the global greenhouse gas budgets, namely in the case of CH4 and N2O. In Switzerland, 80.5% of all national CH4 emissions stem from the agricultural sector (year 2007 values). These numbers so far lack direct experimental validation in the field. The project will thus aim at validating CH4 emissions at the farm scale as a first step towards a validation at the national scale.

Objectives

Thus, the ETH Grassland Team aim to quantify CH4 emissions at the farm scale (0.5–5 km²) of the ETH Research Station Chamau and relate this to estimates reported in the Swiss National Inventory Report under the Kyoto Protocol.

Also the Swiss television SF1 was interested in our project investigating the regional methane budget. See the short video of the Einstein show broadcasted in September 2011, starring Jacqueline Stieger and Dennis Imer.

 

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