The future of waste collection? Underground automated waste conveying systems

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As waste management operations all over the world attempt to become cleaner and greener in the face of new legislation, some companies are looking to move away from the older systems of collecting and transporting waste by road – and are taking the whole thing underground. Here, we take a look at underground pneumatic waste conveying systems and explain the benefits ...

by Katariina Honkio

Even though pneumatic waste collection systems have been around for decades, they are experiencing an upsurge in popularity, as cities are becoming increasingly aware of the problems related to conventional methods of waste collection. The trend to incorporate automated waste collection systems into new housing development projects is rising, particularly in Europe, and in Asia where South Korea, Taiwan and Hong Kong are leading the way in implementing this type of technology.

How it works …

Users of the pneumatic waste collection system deposit their refuse into waste inlets, located around the chosen operating area. Waste collection points are placed outdoors or indoors and are accessible 24 hours a day. There is one waste inlet for each type of refuse (which will typically be divided into mixed waste, organic waste and paper waste). The refuse is temporarily stored by the waste inlets until the next emptying cycle.

The refuse is then transported along the pipelines into containers at the waste station. When full, the containers are sent away for further processing using, for example, the city’s existing underground railway network.

The system is remotely monitored and controlled by operators at the waste station. In addition, some staff are needed to handle the system maintenance when required. No personnel are needed in the actual collection and transport of waste from the collection point to the waste station.

As well as savings from reduced personnel costs, waste vehicle and fuel costs, there are various ways in which automated waste collection systems benefit not only the city image but the environment.

One of the main environmental benefits is reduced CO2 emissions, which is a result of reduced waste vehicle traffic. Reduced waste vehicle traffic also means a more pleasant and safe environment for people living in the area where the system is in use.

Typical application areas for pneumatic collection systems include large metropolitan and residential areas, high-rise buildings, public spaces, healthcare facilities, and hotel and office complexes.

The system life cycle depends on several factors, such as the amount of collected waste, the climate of the operating environment and ground conditions. MariMatic, a company that provides waste, by-product and conveying solutions for a wide range of businesses globally, has developed the MetroTaifun™ system. This system is designed to last for at least 60 years (this applies to the pipeline and waste inlets).

Waste inlets

Waste inlets are the points where the users deposit their refuse bags. Each waste collection point incorporates as many waste inlets as there are types of refuse. There are various classifications for waste fractions. The most commonly used waste fractions in pneumatic waste collection systems are: mixed waste, organic waste and paper. Alternatively, the waste can be sorted at recycling centres. In this case, there is only one waste inlet per collection point.

Residential waste inlets can be located indoors or outdoors.Outdoor waste points are preferred for sparsely populated areas because of their lower construction costs. It is often a good idea to equip residential outdoor waste inlets with locks to prevent unauthorized usage. An alternative method is to use RFID (Radio frequency identification) tags to identify the users. This allows for distribution of waste handling costs based on the actual usage – typically one collection point serves 100–150 residents.

Depending on the amount of waste generated, the capacity of the waste inlet, and the size of the system, the emptying interval may vary between hours and days. All waste inlets incorporate sensors for the detection of the refuse level. This prevents overflow while eliminating the unnecessary emptying of waste inlets.

Waste inlets generally lie 1.5 metres above ground level, and the rest of the waste inlet system lies beneath the surface. This underground part of the waste point substantially increases the storage volume of the inlet without taking up unnecessary space above ground. The underground space also serves as the technical room, housing various sensors and discharge valves.

Pipeline

The main network typically comprises 500 mm diameter steel pipes that are hermetically welded. Any major wearing of the pipe is the result of abrasion by the transported material, in particular, hard and edgy materials such as glass or metal refuse – with the most significant pipe wear occurring at bends. MariMatic has developed and patented special, durable bends used in the MetroTaifun™ system to help overcome this issue.

Waste station

Typically, the waste station is located as far as 2 km from the waste collection points. The entire network can be monitored and controlled by the waste station operators. At least one container is required for each waste type. It is also possible to connect the waste station to the existing public transportation rail network.

The number of waste containers is dependent on the number of waste fractions, waste volume and emptying frequency. For biowaste, a tank is used instead of a container. Full waste containers remain closed and the only time a container is in contact with air is when a full container is replaced by an empty one; this ensures that high levels of hygiene are maintained throughout the system.

Benefits

Pneumatic waste collection systems provide notable long-term cost savings. In order to operate, systems require personnel at the waste station and for maintenance – but no manpower is needed in the actual collection and transportation of waste to the waste station. In addition, no waste trucks are needed to collect waste containers from residential areas, bringing savings in fuel costs and vehicle costs.

While the initial investment cost for a pneumatic system is higher than that of traditional methods, the operating cost of the old system is usually considerably higher, and after the typical estimated payback period of 10–12 years, the pneumatic system is considerably more economical than the conventional one.

In addition to cost savings, pneumatic waste management systems have environmental benefits. As there are no waste collection trucks circling around the residential areas, there are less fuel emissions, less traffic and fewer accidents. It has also been discovered that the waste collection points of the pneumatic system encourage the users to recycle more efficiently. The inlets are never full and the fact that there are no unsightly piles of waste or unpleasant odours is beneficial for both the cleanliness and image of the area. Another benefit is that a pipeline-based waste collection system is very flexible and the system does not get congested – even at peak times.

Single-line and ring-line systems

Single-line systems are the conventional type of automated waste collection system. In a single-line system, the pipeline network forms a tree-like layout, where the waste station is located at the root of the tree and the waste inlets are located along the branches.

Ring-line systems are a novel technology developed by MariMatic. In MetroTaifun™ ring-line systems, the main pipeline both starts and ends at the waste station. The ring-line uses vacuum and pressure to convey refuse along the pipeline.


Ring-line systems use both vacuum and pressure to transport waste. This brings many benefits, such as the automatic removal of blockages. Click here to enlarge image

The ring-line system enables effective and safe municipal waste collection and offers a cleaner, quieter and less smelly solution to municipal waste collection, when compared with the conventional single-line systems.

The use of both suction and overpressure in a ring-line system allows for automatic blockage removal. The system also has a considerably lower energy consumption. In the automatic blockage removal system, the blockage is moved backward and forward by the alternating vacuum and air pressure until it is successfully removed. This means that less maintenance is needed to keep the system operative.

The MetroTaifun™ automatic airflushing and drying system operates by forcing double air speed through the pipes. This is done in the periods between waste fraction collections so that the pipes are clean and dry for each waste stream. This results in vastly improved material recyclability, as there is no cross contamination between different types of waste. This capability has arisen from from the extensive experience and advanced solutions that MariMatic has in conveying food destined for human consumption.

The ring-line systems have lower energy consumption than conventional pneumatic systems. The reason for this is that the ring-line system mainly utilizes the existing air in the network, and that the combination of underpressure and overpressure conveys material with less energy than just the underpressure which is used by single-line solutions.

Thanks to the durable special bends used in the MetroTaifun™ solution, the system also allows for the conveying of glass and metal waste which cannot be done by conventional systems.

Some application areas

Automated waste conveying systems are typically used in large, modern metropolitan areas as well as residential areas, and in healthcare facilities, town shopping centres or airports.

Residential solutions are used in highly populated areas with high-rise buildings. The buildings are linked to the MetroTaifun™ main pipeline and replaceable containers are used. An economically feasible size for this system is 500+ households. The full-fledged MetroTaifun™ metropolitan waste system is suitable for large residential areas with over 20,000 households. The replaceable containers can be collected by metro/underground trains from the waste station.

Smaller-scale pneumatic waste systems are ideal for shopping centres or airports where the installation of a comprehensive system is not as economically feasible. A waste collection system in a public space improves the image of its surroundings by eliminating overfilled waste bins and improving hygiene. Optional waste-bin fire detectors also improve safety.

Hospital and nursing home waste systems offer a solution for healthcare facilities where hygiene is an issue and it is necessary for people to avoid contact with the discarded material. By installing a MetroTaifun™ system with separate collection points for waste and laundry, direct contact with these items can be avoided and the infection risk lowered. It is also possible to convey waste and laundry in completely separate systems.

Growing popularity

Pneumatic conveying systems are rapidly gaining ground in the waste industry, and many new projects are in the planning stages or already in development in various countries. The city of Helsinki, Finland, and the neighbouring city of Vantaa are planning to incorporate pneumatic waste collection systems into their new urban development projects.

Helsinki has several important urban development projects underway. Construction of the Jätkäsaari residential area will begin soon on the city’s southern peninsula. According to plans, the area will be ready by the year 2023. When completed, the total development, covering over 200 hectares will house about 16,000 residents and about 6000 workplaces. Helsinki has decided to handle the waste management of the new Jätkäsaari area with a pneumatic conveying system. The number of waste collection points will be about 350, and the daily system capacity about 22,000 kg of waste. It is estimated that the total residential waste per annum is about 6.4 million kg and the total office waste about 550,000 kg. This is the first major pneumatic waste conveying system installed in the city of Helsinki.

Marja-Vantaa is the most important urban development project in the Finnish city of Vantaa. When completed, the new area will house about 27,000 people and will provide jobs for up to 23,000 people. The first phase of the development project is the construction of the Keimolanmäki residential area, which will have an estimated 2400 residents and 600 jobs.

A pipeline-based system has been proposed as the waste collection solution in Keimolanmäki. This would keep the heavy garbage collection trucks out of the area, making Keimolanmäki safer and more pleasant for the residents. The estimated daily system capacity for Keimolanmäki is 3,000 kg of waste and there will be over 75 waste collection points.

Similar projects are in development throughout the world. It is safe to say that the automated pneumatic collection systems truly are the future of municipal waste management.

Katariina Honkio, marketing and communications, MariMatic Oy, Finland
e-mail: katariina.honkio@marimatic.fi

Additional information compiled by Claudine Capel, editor of Waste Management World
e-mail: wmw@pennwell.com

Movac from Envac

Since the early 1960s, Envac has specialized in the development and installation of automated, underground waste collection systems based on vacuum technology. The mobile vacuum system was developed during the late 1980s in addition to Envac’s stationary vacuum system. Since then, around a thousand residential areas, particularly in the Nordic countries, have made use of these mobile vacuum systems.

Two new features

The new Movac system consists of two main components: the new, third generation mobile vacuum vehicle, the VL-5, and the patented screw tank concept.

These features provide an efficient and environmentally friendly method of waste collection in urban and suburban areas. In comparison with previous mobile collection systems, the emptying time is generally cut in half and collection capacity is generally doubled.


An illustration of the Envac system Click here to enlarge image

The first installation of the new Movac system was made in a residential area in Trondheim at the end of 2008.

One person who has much experience with the system and sees it working on a daily basis is Knut Lugvigsen. He is the chairman of the board for the Ustmyra housing co-operative in Kattem, which is located outside Trondheim. He says: ‘The solution we have today with Envac involves an odourless system that offers a clear advantage to the individuals who are exposed to the working environment.’

How Envac’s third generation mobile vacuum system works … The waste inlet is positioned centrally. Users throw their waste bags into readily accessible waste inlets located indoors or outdoors. The waste is then stored in closed underground screw tanks which are linked together with docking points and a network of underground pipes.

The docking points are positioned on the periphery. The location of the docking points is planned to ensure that the vacuum truck picking up the waste does not have to drive into gardens or narrow streets.

The tanks are emptied regularly, depending on the amount of waste discarded and the storage capacity of the screw tanks. The vacuum truck which empties the tanks via the docking points creates a vacuum in the pipe system. Once this vacuum has reached a required level, the screws in the tanks are activated automatically. The waste is sucked out of the tanks, through the pipe system and into the vacuum truck, where it is compressed.

The waste is then weighed. When the screw tanks are emptied, the amount of waste collected per tank is recorded by measuring the weight within the vehicle. This information can then be used to invoice individual property owners or companies for the waste they produce. It is also possible to identify the various waste inlets according to use and type of waste thanks to card-reader systems and transponders.

Molok® – the deep collection system

Molok Ltd is the inventor, developer and marketer of the original deep collection system for solid waste. The company has grown from a small family enterprise to an international business. The waste management field is facing more and more challenges, particularly regarding recycling and sustainable development and Molok Ltd aims to continue to meet these demands.


Molok Deep Collection waste containers in Finland for the collection of paper, dry waste and biowaste Click here to enlarge image

Molok Deep Collection system is based on a vertical design. Two-thirds of the container is installed undeground and is emptied by lifting the inner collection bag and releasing the locking system at the bottom. This design provides additional benefits for users than other waste management systems. It has more capacity, improved hygiene, is more convenient to use, and saves space above ground. Because of the large capacity of Molok deep collection containers, the intervals between emptying are usually longer than for standard surface containers. This provides an increased economic benefit, as well as protecting the natural surroundings, as there are fewer transport intrusions.

Molok deep collection containers are built to last for long periods of use. All Molok container parts are made of recyclable material, and all metal parts are made of corrosion-proof metals.

Molok is a very simple, and fundamentally sound, waste management solution for the private and public sector, allowing the collect mixed waste, paper, cardboard, organic waste, glass, metal and hospital waste.

The Molok solution is economical, as well as ecological. For more information, see www.molok.com.

Sulo Iceberg Underground Systems

Underground waste collection systems have been developed by SULO Umwelttechnik, a division of the SULO group based in Herford, Germany. Founded in 1892, SULO is a major manufacturer of waste collection containers. One of the notable solutions the company has launched is the Iceberg Optima, a system which enables the efficient and environmentally friendly collection of up to 5 m³ of waste and recyclables underground. These underground systems have a large capacity compared to conventional waste containers and therefore need to be emptied less frequently. The column, walk-on platform and collection container are bolted together, forming a unit. When emptied, the entire unit is lifted from the concrete casing and emptied above the collection vehicle. A safety system installed inside the concrete casing secures the shaft during collection.

Click here to enlarge image

Underground systems can comprise equipment such as fill-level measurement for ‘just in time’ collection logistics, as well as access control systems for fair and individual invoicing based on the ‘polluter-pays-principle’. For example, in the Dutch city of Zoetermeer, where more than 1000 underground systems are in operation, citizens have an electronic key that allows them access to other underground systems nearby. While preventing unauthorized access, the system also enables fair invoicing based on the number of times a citizen actually uses it.

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