New Method for Estimating Greenhouse Gas Emissions fromLivestock Buildings Using Open-Path FTIR Spectroscopy

摘要

It is widely known that methane, together with carbon dioxide, is one of the most effective greenhouse gases contributing to climate global change. According to EMEP/CORINAIR Emission Inventory Guidebook~1, around 25% of global CH_4 emissions originate from animal husbandry, especially from enteric fermentation. However, uncertainties in the CH_4 emission factors provided by EMEP/CORINAIR are around 30%. For this reason, works addressed to calculate emissions experimentally are so important to improve the estimations of emissions due to livestock and to calculate emission factors not included in this inventory. FTIR spectroscopy has been frequently used in different methodologies to measure emission rates in many environmental problems. Some of these methods are based on dispersion modelling techniques, wind data, micrometeorological measurements or the release of a tracer gas. In this work, a new method for calculating emission rates from livestock buildings applying Open-Path FTIR spectroscopy is proposed. This method is inspired by the accumulation chamber method used for CO_2 flux measurements in volcanic areas or CH_4 flux in wetlands and aquatic ecosystems. The process is the following: livestock is outside the building, which is ventilated in order to reduce concentrations to ambient level. Once the livestock has been put inside, the building is completely closed and the concentrations of gases emitted by livestock begin to increase. The Open-Path system measures the concentration evolution of gases such as CO_2, CH_4, NH_3 and H_2O. The slope of the concentration evolution function, dC/dt, at initial time is directly proportional to the flux of the corresponding gas.This method has been applied in a cow shed in the surroundings of La Laguna, Tenerife Island (Spain). As expected, evolutions of gas concentrations reveal that the livestock building behaves like an accumulation chamber. Preliminary results show that the CH_4 emission factor is lower than the proposed by the Emission Inventory.