Emissions of nitrous acid (HONO), nitric oxide (NO), and nitrous oxide (N2O) from horse dung

Abstract

Horse dung contains considerable amounts of nitrogen which is partly lost during the storage period. Leaching of nitrogen from the dung can be prevented with constructions but also gaseous N-emissions occur. However, the emission rates are not reported in the literature. We measured in laboratory conditions nitrous oxide (N2O), nitric oxide (NO) and nitrous acid (HONO) emissions from fresh, one month old and one year old horse dung samples. NO and HONO emissions increased with the storage time of the dung. The mean emission rates of HONO and NO were from 36 to 280 ng N kg dw-1h-1 and from 15 to 3500 ng N kg dw-1h-1, respectively. N2O emissions were more variable showing also highest emissions (20.3 µg N kg dw-1 h-1) from the oldest samples. Thus, the longer storage of horse dung increases gaseous N losses which should be taken into account when planning the environmental friendly way to handle horse dung.