Landfill sites as a source of pests: Waste disposal often leads to problems with pests at the landfill site
In Germany, tipping untreated household waste has been banned since 2005. But the country still has numerous landfill sites, collection points and intermediate storage areas. Here, one specific problem has not been resolved it has only been relocated: vermin and pest infestation. However, pest control has to be limited to containing the problem. This article describes pest control methods that could be used throughout the world.
(01.06.2010) In Germany and other countries in Europe a new term has been coined over the last few years: "pre-sorted recyclable waste". This is not an official description in terms of the waste catalogue, but it is known among all the experts. Many small and several large intermediate storage sites were established for which open areas (even agricultural land) or large halls are used, where the waste can be gradually sorted. The waste residue that cannot be utilised then has to be transported to a landfill site.
These intermediate storage sites have not resolved an old problem, it has only been shifted. I mean by this vermin and pests. Some examples will be given to describe the problem and potential ways of resolving it.
The waste to be sorted is delivered in bales. The content of the bales is pressed together and wrapped with wire, string or plastic foil for better transport and so that the bales can be stacked. However, in these bales there is an adequate amount of air to allow pests to live and breed. They also contain a lot of organic residues so that the insects and rats have sufficient to eat. Because of the heat generated from rotting waste even tropical and sub-tropical pests that are normally found only in buildings are able to survive in winter. The German cockroach in particular finds optimum living conditions.
1. The old rubbish tips were miles away from towns and cities. Vermin lived in the tips, but they seldom migrated to residential areas. The decay shifted and the pests along with it. Later, the decaying layers were covered with earth and became uninteresting for the pests. Freshly delivered waste was compressed through constant rolling; this reduced the air supply – especially to prevent fires.
2. But this is not the case in the "intermediate tips". They are located very close to residential and business areas (with the permission of the responsible authorities, by the way). Often, they border properties directly or, at best, there is perhaps a road between the tip and the houses and businesses. The stored waste is not compressed. The bales are stacked to between 5 and 8 metres high, the decay causes temperatures of up to 70°C. The authorities generally approve a storage time of 18 months, which is often exceeded. Besides, the stacking height of 5-8 metres is often exceeded considerably. This applies especially for "upwards open" storage outdoors. In many cases the bales are stored on unsealed soil – obviously also with the approval of the authorities; at least, they don't seem to complain.
3. The pests and vermin include: Norway rats (Rattus norvegicus), domestic flies (Musca domestica), blowflies (Calliphora and Lucilia), larder beetles (Dermestes), fur beetles (Attagenus) and, especially, the German cockroach (Blattella germanica). The German cockroach is a tropical species. It is found all over the world and has lived in our latitudes for several hundred years, but always in buildings. With favourable conditions its development cycle is 9 to 12 weeks. A female cockroach produces about 100 to 120 young cockroaches, which are sexually mature at around 3 months, when they begin producing their own young. It is not surprising that when they are undisturbed for 18 months and longer an enormous number of cockroaches develop. The preferred temperature for the German cockroach is 24° to 26°C. If its habitat becomes too warm, it is driven out of its substrate, which results in migration from the "pre-sorted recyclable waste" into the surrounding areas – and these are the neighbouring properties and businesses. Since cockroaches can carry pathogens, the fact that they come from waste is a risk that should be taken seriously. Unfortunately, in some cases the indignation of the residents, who are already extremely angry because of the periodic annoyance due to smells and plagues of flies, is not only expressed at residents' meetings in front of the press, but also in arson.
In specific examples two large-scale open-air storage sites were seriously in breach of the allowed amounts of waste and in terms of the storage times. Over a long period there had been an unnoticed massive increase in the number of German cockroaches and also woodlice and beetles. Increased heat forced millions of cockroaches out of the recyclable waste and they migrated to the neighbouring properties. Residential estates, a combined heat and power station, a school, houses and business premises were all affected. In the case of the CHP station there was also a risk of a technical accident, as the cockroaches from the directly neighbouring storage site got into the control room and the computers.
Attempts to control the pests at the intermediate storage sites were unsuccessful as the pesticides were unable to penetrate the bales properly. It was necessary to protect the surrounding areas against the migration. To do this, the waste storage areas were surrounded by an adequately wide clean strip. In one case an eight-metre wide gravel strip between the site and a neighbouring property was established; behind this an earth mound was constructed, which was covered in plants after a year. This created cool zones that the cockroaches no longer crossed – at most they remained there.
Decisive were the additional pipe traps that were laid as barriers. For this purpose, drainage pipes were slit open on the side and spacers were inserted (see sketch). The slits were large enough that the cockroaches could not cross them; instead they had to crawl inside the pipes. Insecticide powder was placed inside the pipes. This powder stops the cockroaches climbing up the smooth walls; they keep falling back and are quickly killed in the pipe.
In a storage hall the bales were stacked in blocks, but the storage times were exceeded. Here, the pests were mainly rats and German cockroaches. Excess heat also forced the cockroaches out of the hall and they migrated to neighbouring houses and allotments. Initially, chemicals were sprayed over the bales to kill the cockroaches. But this did not work.
Since the floor was a concrete screed, a strip about one metre wide around the storage areas was cleaned carefully and a complete barrier of insecticide dust was applied. The cockroaches had to cross this barrier and in doing so covered themselves in powder. They were killed quickly and reliably. These insecticide strips are maintained constantly. This measure was also successful.
Summary: Delivering cockroaches and other pests cannot be avoided. But it is possible to stem propagation and it is extremely important to stop the pests migrating.
What conclusions can operators of waste and recyclable material storage facilities draw? 1. Mass propagation of pests and vermin must be prevented. This can be achieved by keeping the retention periods for waste as short as possible – based on the principle of 'first in – first out'. Ideal is a storage time of no more than three months. Then the cockroaches would have only one breeding cycle and the number of young cockroaches would be relatively small.
2. Pests must be prevented from migrating to open areas. This can only be achieved if suitable traps and monitoring strips, pipe traps with insecticide powder or mat traps impregnated from below with long-term insecticide are installed. This must be carried out by specialist companies – also the subsequent maintenance. As the insects constantly migrate, this maintenance must be regarded as a permanent task.
3. Limiting the quantities of waste and stacking it appropriately.
4. Stopping pests migrating out of the halls: installing clean strips around the stored materials on the floor and installing insecticide powder barriers. These strips must also be maintained regularly.
5. A still unresolved problem is how to combat the insects in the stored waste. At present it is only possible to deal with the rats.
This also has significant consequences for the responsible authorities in Germany. The criteria for allowing a storage site for "pre-sorted recyclable waste" should be reviewed, believes the author.
1. Allowing waste to be stored for 18 months encourages pests and vermin and allows mass propagation. The retention time should therefore be reduced.
2. Sites for these storage areas should be as far away from residential and commercial buildings as possible.
3. The storage sites should be checked regularly by experts.
Author: Dr. Ingrid Koerber, specialist consultant and expert for pest science, Berlin (Germany)
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