COLLECTION AND TRANSPORT
OF SOLID WASTE IN THE FEDERAL
REPUBLIC OF GERMANY
Joachim Knoch
Joachim Knoch, VPS: Private Refuse Disposal Contractors' Association, Cologne, F.R.G
Waste management & Research (1986) 4, 137-145
The most important techniques for the collection and transport of household and similar solid waste in use in the F.R.G. are presented. Graphs present relationships between weight and volume of containers, collection rate, collection cost, transport distance and number of stops per 100 metres.
Key Words: Municipal solid waste, collection, containers, costs, time, routes, F.R.G.
1. Introduction
The technical status of refuse disposal is the result of 70 years experience. In the last 25 years, important innovations in the organization and development of technical systems have been caused by (a) strict laws for the protection of the environment, (b) the demand to make work more humane, (c) pressure to rationalize in order to reduce costs (increasing wage, energy and material costs), (d) changes in the legal regulations concerning roads and vehicles, and (e) the changed characteristics of waste matter itself.
As opposed to the time when refuse disposal was first organized on a technical basis, which dealt mainly with residues from household combustion (waste collection bins were called in the jargon of the day "ashbins", and the refuse disposal worker was known as the "ashman"), today refuse disposal services have to collect and transport much larger amounts of waste. Above all, however, the most important characteristics of waste, as far as transport technology is concerned, are completely different.
The technical status of refuse disposal is the result of 70 years experience. In the last 25 years, important innovations in the organization and development of technical systems have been caused by (a) strict laws for the protection of the environment, (b) the demand to make work more humane, (c) pressure to rationalize in order to reduce costs (increasing wage, energy and material costs), (d) changes in the legal regulations concerning roads and vehicles, and (e) the changed characteristics of waste matter itself.
As opposed to the time when refuse disposal was first organized on a technical basis, which dealt mainly with residues from household combustion (waste collection bins were called in the jargon of the day "ashbins", and the refuse disposal worker was known as the "ashman"), today refuse disposal services have to collect and transport much larger amounts of waste. Above all, however, the most important characteristics of waste, as far as transport technology is concerned, are completely different.
While the volume of waste has increased, the weight per volume of waste is ever decreasing (when collecting in 240 and !100 1 containers, it is c. 0.1-0.2 tonnes m-3). While compressibility has increased, the waste itself is less easy to shape in terms of plasticity. This means that waste matter in collection vehicles has to be compressed using a relatively high amount of energy, in order that the permissible payload of the vehicle can be reached. An example of this is the incidence of plastic foams found in waste: while they have a very small weight per volume, they can only be compressed by using a great deal of energy, when loading the vehicle, and on decompression, when unloading the truck, take on almost the same original volume (spring-back effect). In order to maximize the payload while maintaining a constant permissible maximum weight, the tare weight of the vehicle must be minimized. Therefore the construction of the vehicle must take up the smallest possible volume in relation to the compession unit. As.far as waste disposal is concerned, refuse collection is particularly important, as only collected waste can be hankiled correctly and in an environmentally suitable manner. Refuse collection is the essential pre-requisite for the effective handling of waste. All tasks which are connected with the collection and transport of waste must, initially, be
solved as far as the concept of Waste management of a region is concerned; treatment of waste is the second step; for example, waste treatment plants can only be correctly planned when the amount of waste is known. This is only possible through a complete refuse collection system---questionnaires or similar methods cannot be used to assess these values.
In connection with the efforts being made in utilization of waste, collection and the techniques used for collection and transport take on a particular importance. Waste recycling should not be impeded by these methods, on the contrary, refuse collection must be brought into the concept of recycling waste. When, for example, waste matter has to be sorted, then additional mixing and breaking up of the waste matter during collection and transport should be prevented. To achieve this, collection vehicles with pressing rather than mixing units should be used. It may be necessary to sort the waste at its place of origin. This will reduce the costs of recycling, but will make refuse collection more expensive.
Of particular importance as far as achieving a successful concept for recycling waste is concerned, is the integration of collection, transportation and recycling--both technically and in terms of organization. It should be noted here that recycling waste has the manufacture ofproducts as a goal, (e.g. paper, scrap, compost). These have to be marketed if they are not to become waste products themselves. These tasks have to be completely fulfilled commercially otherwise it is not possible to achieve long-term success.
As a result of experience gained with technically complicated waste treatment plants "(e.g. combustion and pyrolysis), centrally placed plants in the F.R.G. are experiencing a trend which is putting the use of simple forms of technology to the test in decentralized plants. This approach can be regarded as a competitor of perfectionist, centralized techn01ogy. Here it is possible that economic and ecological success will occur when a unified concept for the collection, transport and treatment of waste matter is dealt with consistently. The most important aspect of this concept is the method of adapting technology to a changed task. It is also inevitable that the administrative area will have to be flexible in order to permit this technology (laws, regulations, contracts and scales for charges).
In connection with the efforts being made in utilization of waste, collection and the techniques used for collection and transport take on a particular importance. Waste recycling should not be impeded by these methods, on the contrary, refuse collection must be brought into the concept of recycling waste. When, for example, waste matter has to be sorted, then additional mixing and breaking up of the waste matter during collection and transport should be prevented. To achieve this, collection vehicles with pressing rather than mixing units should be used. It may be necessary to sort the waste at its place of origin. This will reduce the costs of recycling, but will make refuse collection more expensive.
Of particular importance as far as achieving a successful concept for recycling waste is concerned, is the integration of collection, transportation and recycling--both technically and in terms of organization. It should be noted here that recycling waste has the manufacture ofproducts as a goal, (e.g. paper, scrap, compost). These have to be marketed if they are not to become waste products themselves. These tasks have to be completely fulfilled commercially otherwise it is not possible to achieve long-term success.
As a result of experience gained with technically complicated waste treatment plants "(e.g. combustion and pyrolysis), centrally placed plants in the F.R.G. are experiencing a trend which is putting the use of simple forms of technology to the test in decentralized plants. This approach can be regarded as a competitor of perfectionist, centralized techn01ogy. Here it is possible that economic and ecological success will occur when a unified concept for the collection, transport and treatment of waste matter is dealt with consistently. The most important aspect of this concept is the method of adapting technology to a changed task. It is also inevitable that the administrative area will have to be flexible in order to permit this technology (laws, regulations, contracts and scales for charges).
2. Collection
Here, tile aim is to collect and register all waste. Various technical systems are used for this purpose and consist for the main part of containers and vehicles which have technical units adapted to the containers.
(1) Emptying system: waste is collected in the system's containers by the refuse collectors; these are emptied at regular periods of time into the collection vehicle and then put out again, ready to collect further refuse; and refuse that has been collected is compressed in the collection vehicle.
(2) Exchange system: waste is collected in the system's containers by the refuse collectors; according to demand--or at regular periods of time--the containers are exchanged by the vehicle for empty containers; and compression of waste does not occur, or it may be carried out by stationary or mobile compression units on the exchange container.
(3) Disposal system: waste is contained in disposable containers (generally sacks); these are collected, including their contents, as waste; and the compression of the waste material occurs in the collection vehicle.
Of central importance are the containers which are used to collect the waste and which are passed on to the refuse collection. These containers have to generally fulfil the following conditions:
(1) practicable for the waste producer;, (2) strong enough to withstand the waste (chemical and mechanical strains) (3) practicable for carrying out the refuse collection (management) and (4) maintenance-free (construction and material).
Experience in the F.R.G. has shown that all the waste is collected only when the waste producer is given a container with a large enough volume to deal with the waste without it having to be reduced or pressed together beforehand. It would seem that collection using four waste bins, each of 60 1 volume, is statistically just as good as using one container of 2401 volume. In fact, collection using a 2401 container is more successful as a result of its geometry of space which also allows bulky waste to be dealt with better than in four waste bins each of 60 1 in volume.
2.1. Containers
2.1.1. Emptying system
The following types of container are used.
(1) Round containers (bins, barrels) made of galvanized steel or plastic (generally polyethylene) with volumes of 35 and 50 1 (small), with a uniform lid geometry for even tipping into the collection vehicle, or 60, 90 and 110 1 (medium), with a uniform lid geometry for even tipping into the collection vehicle. Different tipping procedures are necessary for the small and medium containers. This makes emptying more difficult when different container types are used together.
(2) Square-type containers made of galvanized steel, ungalvanized steel, aluminium or plastic with volumes of 120 and 240 1 (large), with a uniform lid geometry for even tipping into the collection vehicle; 1100 1 (330 and 660 ! containers have recently been introduced), for which special tipping is necessary; or 2500 and 5000 1, for which special tipping is necessary. Containers with volumes of 120-11001 can be emptied in one tipping which means the collection of waste with the aid of these large types of containers can be carried out with a uniform vehicle technology. The advantages are flexibility in route planning, exact adaptation of the container volume ot the amount of refuse, a rational collection system and better maintenance of technical equipment such as the vehicle, tipper unit, containers, etc.
In order to make the work easier and to aid rationalization, the containers are generally equipped with wheels so that they can be moved relatively easily when they are completely full. Tipping to empty the containers generally takes place at the rear of the vehicle. This means that containers have to be brought from their location to the place where the vehicle is stopped, either by carrying them, rolling them on the ground or by using the wheels mounted on the container.
In order to simplify matters (particularly to save on labour), the following systems have been developed for emptying containers.
(I) Front-loader: (for containers with a volume up to 4.5 3) the vehicle drives up to the container; the container is raised overhead, using a fork device over the front of the vehicle, emptied into the collector of the vehicle from above and finally replaced back on the ground; the driver can observe the pick-up procedure; apart from the driver, no further employees are necessary.
(2) Side-loader: (for containers up to c. 300 1 in volume) a grab unit is mounted on the side of the vehicle which can pick up the container, empty it into the vehicle and replace it.
Which of these two systems best fulfil the requirements has not yet been finally assessed. In the F.R.G. the following trend is taking place. Transportable containers, on wheels, with volumes of 120-1 I00 I (emptied with the aid of a tipping unit on the vehicle) are being used, as are containers with volumes of 2500-5000 1 (emptied using a special tipping unit on the vehicle); by mounting tippers on the rear of the vehicle, they can also be used for the collection of bulky refuse which can be loaded directly (this is not possible with front-loaders). The emptying system is mainly used to collect refuse which occurs regularly in many different places (for example, residential areas); such waste is generally compressible.
2.1.2. Exchange system
Containers of the most varying types of construction and size (volume) are used here; generally they are made of steel. The volume of the containers is between 5 and 40 m 3. A complete list of all systems used is not possible; in principle the following divisions can be made.
(1) Filling the container: containers with stationary or mobile compression units for waste; containers without compression units.
(2) Container handling: lifting up/setting down containers in a horizontal position (moveable with chains on swinging arms); picking up/setting down of containers in an inclined plane (sliding onto a cradle which can be tipped).
The container exchange system can generally be used when large amounts of waste arise over short periods of time, or when waste is not compressible (elg. building site rubble). The exchange system is effective particularly when collecting during peak periods, at events or when waste is seasonally defined. For some time now, with the aid of the exchange system, in the F.R.G. an attempt has been made to separate waste, e.g. using special containers for glass or paper.
2.1.3. Disposal system
Here sacks are used generally as containers; these are made of paper, plastic or paper and plastic. Experience has shown that the use of sacks can present problems because
(1) they can easily be destroyed by sharp or pointed parts in the waste.
(2) the danger of injury for the refuse disposal worker is relatively large,
(3) the physiological requirements from the refuse disposal worker are very un-favourable (all waste that has to be collected has to be lifted and carried by the employee),
(4) relatively large amounts of "bulky" refuse result (the refuse which does not fit into the sacks),
(5) a relatively large amount of raw material used as sacking has to be discarded as refuse. In favour of the use of sacks is the fact that only very small initial investment is required (vehicles but no containers).
In the F.R.G., refuse collection with sacks is only carried out at isolated sites.
2.1.4. Location of the containers
The location for the containers must be so designed that:
(I) the containers can be filled in safety;
(2) in the emptying system, the containers can be moved safely and, if possible, on level ground (free of steps), or can be carried over this ground;
(3) in the case of the exchange system, the containers can be reached by the vehicle directly, with a clearly visible access;
(4) the containers, where possible, should stand in the shade; and
(5) cleaning and care should be easy to carry out.
2.2. Vehicles
Vehicles which are used for collection, together with the containers used, make up a uniform system for the collection of waste. For lifting and emptying containers, special equipment is required which has to be firmly mounted onto the vehicle; in the case of exchange containers, according to the system of containers used, the suitable technical equipment (lifting gear) has to be available on the vehicle. It is not possible to combine at will vehicles with a fixed tipping/lifting gear and containers of various types. The vehicles used can be placed into the following construction categories.
(1) For the emptying system: chassis with drive unit, collector with compressing equipment for the waste tipper;
(2) for the exchange system: chassis with drive unit, lifting equipment for p!cking up and setting down exchange containers;
(3) for the disposal system: chassis with drive unit; collector with compressing unit for the waste (practically the same vehicle as in the emptying system,but without tipping gear).
In order to carry out the collection of refuse in the best way possible, the vheicle has to fulfil contradictory requirements:
(I) for collections--mainly in urban areas--a small and manoeuvrable vehicle is required; payload c. 6 tonnes (with a total weight c. 16 tonnes with two axles).
(2) for transport to the treatment plant a vehicle with the highest possible payload is needed which does not have to be so manoeuvrable; payload 17 tonnes (total weight c. 38 tonnes with five axles).
A three axle vehicle with a payload of c. 9 tonnes can be regarded as a compromise which needs more time when collecting than a two axle vehicle, but which, however, is better in terms of transportation. The use of transferable units (from two axle to five axle vehicles) is considered the most suitable solution at present.
The development of a collection vehicle with an exchangable collector used as an exchange container would be consistent with this. This would optimize collection with a manoeuvrable vehicle, allow transference onto a vehicle with a higher carrying capacity and allow intermediate storage of empty and full containers. Prior knowledge about the waste concerned is essential in the choice of vehicle. In relation to the size of the collectors, the weight per volume of the waste is c. 0.1-O.2 tonnes m-3, with a mid-range of c. 0.15 tonnes m -3. The compression performance which can be reached using the body mounting of the collection vehicle is c. 3.5-4.5 with a mid-range of c. 4.0 (that is the relationship of the weight per volume I~fore and after compression). At a given payload, it is possible to calculate the necessary volume of the body mounting of the collection vehicle (VA) (collector):
payload, 6 tonne VA = 6/4.0 x 0.15 = 10 m 3,
payload, 9 tonne VA = 9/4.0 x 0.15 = 15 m
3. There is a relationship between the compression capacity and payload as, on increasing the compression capacity, the energy needed from the equipment increases, the tare of the vehicle increases and the payload thus decreases. Furthermore, the distribution of the axles has to be taken into consideration. In the F.R.G. the maximum permitted axle weights have been laid down and may not be exceeded. When, as a result of the vehicle's construction, the rear axle is loaded to its full permissible weight when only partly filled with waste, no further loading may be carried out. That vehicle then has a "reduced payload". Such vehicles should not be used.
The technifial information about the collection vehicles is produced by the vehicle manufacturer. The use of a particular type of vehicle for a job can only be decided by test, such as driving behaviour and maneuverability during pre-set traffic and topo- graphical situations, or the compressibility of waste, etc.
3. District planning
The estimation and organization of refuse collection is only possible when the amount of the total work can be described (the amount of waste according to time and type), as well as when it is possible to divide up the area where waste management is to be carried out (town, region). A division into districts is absolutely essential in order to make easily comprehensible organization units (technical equipment and staff). This permits the same team to work in the same district allowing them to obtain the necessary knowledge of the area. The size of the district has to be calculated from the type of container system, the type of vehicle, the density of population as well as the collection and transport vehicles. It is not possible to "calculate" in a mathematical sense, like an equation, these factors and their relationship. The specific performance of the collection vehicle has to be established empirically (speed in km h-1, collected waste in tonnes h-1 or tonnes km-1 as a function of the container system). To achieve this, test areas must be established. This can be based on experience made at another area and with different requirements and conditions, but which is still suitable to serve as a base for the conception of other tests. What is important is that the data and experience used, as a result of refuse collection in these test districts, improve the tests and can be examined as to their suitability for other regions/districts.
The following data can be used in order to establish a test district. They contain average values resulting from a series of running statistics kept by the company Edelhoff Staidtereinigung (Town cleaning) GmbH & Co as follows.
Fig. 1. Relationships between weight per volume and container volume (a), and the collecting speed and number of stops (b), weight of waste (c) and container volume (d)
Fig. 2. Relationships between weight of waste and collecting rate (a), size of collecting vehicle and collecting cost (b), and transport distance and time required (c) and transport cost (d).
In Figs 1 and 2, the connection between collection capacity and collection technique and cost is shown, obtained as a result of calculations. With the help of this experience, it is possible to plan out a test district.
One restriction which must be borne in mind in this procedure is that this experience has been obtained by the observation of a perfectly functioning example of refuse collection in the F.R.G. Should one, at the very beginning, want to avoid these very high expenses, it is conceivable that the following concept could be used.
Exchange containers which people bring their waste to are placed at central positions. This means having to forego the comfort of having waste collected during the test period. However, the advantage of this system can be seen in that very small initial investment is required, and it can be put into practice relatively quickly. It can be adapted to demand by changing the volume of the container, and by the frequency of collection. In order to ascertain the type of dimensions involved, an estimation of the amount of waste must be made, as well as the furthest acceptable distance between the exchange container and the area of residence. Exact observation would show whether this distance was too great and needed to be reduced (this cannot be corrected by raising the frequency of collection).
The system has one serious disadvantage. In general, the permissible payload cannot be reached when the exchange container is loosely filled. It might therefore be more effective if large volume emptying containers are used instead of the exchange containers. These can be emptied into the collection vehicle and the waste could then be compressed. In using emptying containers with a volume of 5 m3, it would be possible to place them at a short distance from the area of residence. As opposed to the use of exchange containers, more containers are used. The location for the containers must be able to be reached by the collection vehicle and must be kept clean.
4. Trans-shipment
Trans-shipment (at a transfer station) is a good idea when lots of small amounts can be made into one single large quantity, and when the transport costs for direct transportation are less than for small amounts. Here, driving time (dependant on the road network, road condition and traffic situation), as well as payload, has to be taken into consideration. It could be more suitable, for example, when a collection vehicle with a 6 tonne payload travels 3 X daily to the treatment plant (depot), then trans-shipping into a transport vehicle with a 18 tonne payload. The trans-shipment of waste in stationary plants in the F.R.G. is practised mainly because the treatment plants have been centralized, giving transport routes of up to 100 km; and vehicle technology does not at the moment allow for mobile transference units, e.g. for exchangable collectors of the collection vehicle.
Although this technology, both for vehicle and collection, is urgently required, its development has been hindered by the operation of stationary trans-shipment plants. The aims in planning a trans-shipment plant should be
(1) quick processing (emptying) of the collection vehicle;
(2) transport vehicles with a higher payload and simpler vehicle technology;
(3) loading the transport vehicles either directly from a collection vehicle (funnel, slide methods), or with loaders on rollers or something similar;
(4) the use of normal trade equipment which can be exchanged, repaired and is reliable; and
(5) the adaptability of the plant to changed loads (organization, technology).
As delivery of refuse does not run synchronously to its being transported away, an interim stage has to be incorporated. This storage capacity must be generous in size so that amounts during peak periods, as well as operational breakdowns, repairs, etc., can be dealt with, without delaying the emptying of collection vehicles. The collection and trans-shipment of waste can be integrated when the same technology is used for collection and transport. This then means that vehicles and containers are interchangeable. This, in turn, means a reduction in investment, simplification of maintenance, increased operational reliability and better organization (technical equipment, maintenance and staff).
The use of compressing equipment having hydraulic presses and specially designed enclosed containers demands expensive equipment both in terms of its construction, its machine technology and its control units. Because of the expensive technology and the complicated organization and maintenance needed, this unit tends to be less reliable in operation. The payload of the transport vehicle is greatly reduced by the heavy "pressing container". On the whole, the technology of trans-shipment plants has come under criticism because, in spite of the considerably higher investment costs and greater expense, no better results have been achieved than in trans-shipment plants using normal trade equipment and with a large storage capacity. Not only that, the high technology plants are not flexible enough to be able to adapt to changed requirements.
It must be mentioned, in this connection, that trans-shipment plants, for example, could carry out simple sorting of waste. However, this would not be possible after compression in the case of technically highly complicated plants.
Operating a trans-shipment plant can be effective when the distance between treatment plants lies between c. 30 and 50 km. The cost of trans-shipment is around DM 15-30 per tonne. The relationship between transport costs and distance can be seen in the Figures.
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