Notes on Composting at La Collette

A few comments on the residents' problems associated with the composting site at La Collette. This is coming up again, with calls for it to be closed.

1) "Just a smell"

Smell is due to minute particles in the air being picked up by the olfactory system of the human body. To say that something is "just a smell" as has been reported in the JEP by some authorities is misleading; if you can smell something, some kind of particles are in the air. The question is whether those particles are sufficient to cause allergic reactions in some individuals.

2) Bad use of statistics

To say that workers at the site have experienced no side effects is again misleading. Workers are fit, healthy individuals who engage in this kind of work precisely because they are not susceptible to allergic reactions! They are not representative of the population as a whole. It is like checking to see how many gardeners suffer from hay-fever; if you suffer severely from hay-fever, gardening is unlikely to be your profession of choice!

3) The link between compost and allergy

That composting can cause allergic reactions in workers (who are not normally susceptible), can be seen at the Arkenas site on composting and solid waste management. Note the conditions - such as allergies or asthma - which should be avoided by those in proximity to compose. Clearly the effect of airborne particles is diluted by the wind, but nevertheless, it cannot be ruled out as a cause.

http://www.adeq.state.ar.us/solwaste/branch_technical/compost.htm#Precautions

Just as individuals vary in their resistance to disease a few individuals may be particularly sensitive to some of the organisms in compost. The high populations of many different species of molds and fungi in an active compost process can cause allergic reactions in sensitive individuals, though most experience no adverse reaction. Conditions that may predispose individuals to infection or an allergic response include: a weakened immune system, allergies, asthma, some medications such as antibiotics and adrenal cortical hormones or a punctured eardrum. Workers with these conditions should not normally be assigned to a composting operation.

4) Seasonal evidence

It would be interesting to see if any the medical profession have noted any increase in patients attending surgeries from the areas possibly affected by La Collette. One aspect of composting mentioned by a House of Commons Select Committee (http://www.publications.parliament.uk/pa/cm199900/cmselect/cmenvtra/903/903m47.htm) suggests that this is dependent on climate and seasonal factors, and this should be borne in mind for any testing of emissions or reports of sickness.

Good control of aerobic composting sets optimum conditions for efficient decomposition. That creates an ideal habitat for the growth of micro-organisms including fungus. Fungi include pathogens and allergens harmful to people, livestock, wildlife or crops. Frequent lifting and turning is necessary for good management to aerate the mass of material. That causes fungal spores and fragments to be spread abroad and scattered in the wind. Some will remain aloft for days and travel many miles. They are subject to Stokes' equation and other physical factors and will not obey edicts from the Environment Agency anymore than the waves would retreat for King Canute. We are unable to verify the claim of the Composting Association that the concentration of bioaerosols reaches background level at 200 metres from the source. Some more independent people put it at 1,000 or 1,500 metres. Our own observation is that much depends on climatic conditions. It is seasonal and that is especially evident when fungus is carried with the Autumn mists. Remnants can establish new colonies on naturally decaying vegetation thus moving out more slowly but surely or they may contaminate the exposed finished compost.

5) Reducing odor - why it happens and best practice

There is an excellent site on composting facilities and odour management at:
http://www.epa.state.oh.us/dsiwm/document/guidance/gd_497.pdf

This explains how a properly run composting site can reduce the odours to a minimum. It would be interesting to note which of the methods explained in this report is used by the States at the La Collette site to reduce foul odours (click on the link for the full report and details of procedures used).

A frequent problem encountered at composting facilities is the generation of foul odors. This fact sheet is intended to provide guidance and answer some questions about the origin of foul odors and how to prevent and manage them.

How are anaerobic odours generated?

Anaerobic odours can originate with the incoming feedstocks or bulking agents, which may have been stored without aeration for some time before transport to the composting site. Once those feedstocks or bulking agents are incorporated into the composting system, subsequent odor problems are usually a result of anaerobic (low oxygen) conditions. These odors include a wide range of compounds, of which the most notorious are the reduced sulfur compounds (i.e. hydrogen sulfide, dimethyl sulfide, dimethyl disulfide, and methanethiol), volatile fatty acids, aromatic compounds, and amines.

Ammonia is the most common odor that can be formed anaerobically as well as aerobically, and is usually more
noticeable on the composting site rather than off-site. This is due in part because it is lighter than air and rapidly rises up into the atmosphere. Noticeable ammonia losses are primarily a result of low carbon to nitrogen (C:N) ratio. However, pH is also a contributing factor. If the pH is around 9, there is a reasonable equilibrium. A higher pH forces more ammonium into the gas form which you can smell.