Evaluation of the Photoacoustic Multi-gas Monitor during measurements of gas emissions from composting livestock manure

Summary

Livestock manure contributes significantly to the atmospheric concentration of ammonia (NH3) and green house gasses. Increase in the atmospheric concentration of these gasses cause serious environmental impact locally and globally. There is therefore a need for abatement technique to reduce the gas emission from manure, and for safe and reliable measuring methods. The Photoacoustic Multi-gas Monitor (PMM) is an efficient and handy method for continuous and simultaneous measurements of concentrations of different gases and its reliability was therefore tested during measurements of gas emission from a store of composting livestock manure. Concentrations of ammonia, methane (CH4) and nitrous oxide (N2O) in airflows entering and leaving a store of composting livestock manure was estimated by the PMM method and compared to estimations of gas concentrations attained by different types of measuring techniques. The PMM measuring system gave similar estimates for ammonia concentration as observed by Kitagawa measuring technique when concentrations of ammonia were lower than 50 ppm, but slightly lower estimates when concentrations of ammonia were higher than 50 ppm. The PMM measuring technique measured similar concentrations of CH4 as the gas chromatograph (GC) method, when measuring concentrations above background levels. However, when used for measuring background level of CH4, estimations obtained by the PMM method were different from estimations obtained by the GC method and seemed to be correlated with air humidity. Estimations of N2O concentrations obtained by the PMM method were almost similar to results obtained by the GC measuring technique, except when high levels of ammonia concentration were observed.