International Review of Waste Management Policy - Department of ...

The current analysis assumes that in total, 95% of the nitrogen in the NH3 entering
the biofilter is converted by the action of the biofilter. Of the converted proportion,
25% of the nitrogen is assumed to be converted to N2O. We also assume that 50% of
the VOCs are removed by the action of the biofilter, and that those remaining are not
harmful to health (and therefore no damage cost is associated with their emission).
63.8.3.3 Bioaerosols
Significant recent interest, at least within the UK, has centred on the potential
consequences of emissions of bioaerosols from composting processes. The
Environment Agency sponsored two studies in the early part of the decade. These
studies were reviewed for the Cabinet Office in a paper by Hogg. 1267 That review cast
some doubt upon the conclusions drawn from the research undertaken, notably, the
way in which it was used to influence regulatory guidance, for example, in respect of
distancing from compost facilities. 1268
Bioaerosols are micro-organisms and other tiny biological particles that are
suspended in air. They are respirable and generally invisible. Dusts are small particles
that are larger than bioaerosols. They are inhalable but not respirable and are visible.
Bioaerosols and dusts can both be produced by the composting process. Surveys
have drawn particular attention to a fungus called Aspergillus fumigatus. It is found
all over the world, especially in soils and in forest litter. It is particularly associated
with the composting process as it is capable of degrading cellulose (a carbohydrate
found in plant material) and it is capable of surviving at temperatures of up to 65°C.
As part of its lifecycle, Aspergillus fumigatus produces tiny spores. If inhaled as a
bioaerosol these spores may cause allergies and inflammation, which in certain
individuals can cause serious health disorders such as Asthma, Alveolitus, Mucus
membrane irritation, Chronic Bronchitis and coughs, Gastro-intestinal disorders and
Skin disorders.
Individuals who work at a composting facility – less frequently those who are located
in close proximity to a facility – may be exposed to, and inhale large quantities of
bioaerosols, particularly when compost is being moved or agitated, To most
individuals, exposure to bioaerosols does not appear to cause significant problems.
However, as with some more conventional pollutants, certain individuals, for example
asthmatics and the immuno-compromised, may suffer adverse health effects after
exposure to bioaerosols.
The number of individual organisms necessary to cause a reaction varies according to
the state of health of the person exposed to them. In the composting process, the
levels encountered can be significantly higher than background levels. Therefore it is
imperative that steps should be taken to protect site operatives and residents in the
surrounding areas. Effective operational management can help to control the
formation of bioaerosols and dusts and thus reduce the impacts associated with
these pollutants.
1267 D. Hogg (2002) Waste Treatments Mk II: Health Effects, Report for the Strategy Unit.
1268 See Environment Agency (2001) Agency Position on Composting and Health Effects, 2001.
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