Quantification and Monitoring of Gas Emission From Agricultural Sources: Measurement Technology and Limitations.

Global emissions of gases from agricultural and animal feeding operations contribute to climate change, produce odors, degrade sensitive ecosystems, and pose a threat to public health. The complexity of these emissions and the intricate set of factors that impact them complicate their accurate and reliable quantification. Although a plethora of technologies exist for measurement of gas emissions, each method has problems that exacerbate accurate quantification. In general, measurement and monitoring techniques are divided into chamber methods, both open and closed, and micrometeorological approaches.  Chamber methods are commonly applied in agricultural operations and are usually less expensive than other approaches.  However, resulting measurements must be extrapolated over the entire agricultural operation to be meaningful. Such extrapolations may be unacceptable for certain applications where uncertainty is already high due to climatic and livestock variables. Micrometeorological methods are widely accepted and can measure gas emission on the farm scale.  Although these technologies have the advantage of being truly in situ, implementation of such measurements is limited by the cost and complexity of the required equipment. A thorough review of the literature suggests that available measurement technology for gas emissions from agricultural operations do not include real-time, continuous monitoring capabilities. Future research should focus on emerging technologies such as solid-state sensors in an effort to design low-cost real-time monitoring systems.