Abstract
Agricultural biogas facilities in Switzerland generally complement livestock farms. Facilities in the vicinity of residential areas can cause residents to complain about odours. Area sources include storage facilities of substrates, fermentation residues, the animal housing and outdoor exercise areas, feed and manure stores. Biogas can also escape directly from the facility.
The aim of these investigations was to examine the odour impact of the farm as a whole in relation to the decay behaviour of the odour plume, with a view to determining the requisite distance to residential areas. Plume inspections of the ambient air on a dairy farm with a biogas facility were carried out on three days during the summer and transitional period, in each case in the afternoon and evening. Six assessors at various distances from the farm registered their odour perception at 10-second intervals.
The odour intensity distribution of the assessors during individual field inspections is presented: high percentage odour times with high odour intensities are ascertained at positions close to the farm. As the distance increases, there is a noticeable reduction in percentage times with odour as well as a decrease in the high intensity levels. The higher the wind speed, the further the odour reaches and the more intense it is perceived. Biogas leakage situations further increase the effect. Biogas odour is rated as definitely unpleasant by the assessors.
Compared with grid inspections the decay behaviour of odour could be determined much more efficiently by focussing on the odour plume. As a precaution, it is advisable to take great care when selecting the location for new agricultural biogas facilities, usually as an addition to livestock farms. Distances to residential areas should be adequately assessed. Process optimisation and maintenance should be addressed in order to prevent biogas leakage.
