Smart City technology evolved together with the developments in wireless sensor networks (WSN) and the Internet of Things (IoT). Smart cities essentially combine the use of ICT to provide services for better living conditions inside cities. It is a diverse topic of discussion with several application areas as shown in Figure 1. This article focuses on the Smart Waste Management application.
The current state of technology in the field of smart waste management involves use of sensors that measure fill level of the trash bin. Measured data is sent to the Cloud for further processing and analysis. By exploiting this data, trash collection can be planned as well as truck routes can be optimized. Despite this solution being an improvement of the conventional (sensorless) solution, it suffers from major drawbacks, poor sensor performance and lack of any contribution to the trash sorting at the recycling facility. The solution presented in this article focuses on the mitigation of these disadvantages by implementation of RFID based trash identification system and additional weight sensor for improved fill level estimation.
Let’s first define the problem;
The current process of waste management starts with the waste being created by people in the cities and disposed in trash bins near its creation point. The disposed trash is collected by municipality or private company trucks at the predefined times and transferred to temporary collection centers. The trash at the collection centers is then sent for recycling.
This process in current city setting solves the waste problem partially while it creates other problems such as;
- Some trash bins are overfilled while others are underfilled by the trash collection time,
- overfilled trash bins create unhygienic conditions,
- unoptimized truck routes result in excessive fuel usage and environmental pollution and
- all collected trash is combined which complicates sorting at the recycling facility.
Some of these problems can be mitigated by implementing smart waste management systems.
Problem mitigation through smart waste management
The waste management services take care of a healthy environment allowing optimization of the utilities and prevent overloading the carrier for waste disposal. Smart waste management also contributes to the overall waste recycling efficiency and provides the route optimization opportunity for utilities to reduce traffic and fuel use.
An example of modern smart waste management system would include; a sensor attached to the trash bin that measures fill level; and a communication system that transfers this data to Cloud. Data is processed in the Cloud, thus, route of collection trucks is optimized.
Smart waste management companies have recently developed solutions based on the ultrasonic distance measurement. Some companies prefer to approach to the problem with an alternative solution using image processing and camera as a passive sensor. However, majority of these solutions use ultrasonic sensor for measurement of the distance.
Ultrasonic sensors use well-known sonar technique to perform measurement of the distance between the sensor and an obstacle. The sensor consists of an emitter that sends the sound pulse and a receiver that detects that pulse upon its reflection from an object. The distance to an object can be determined by measuring time between emitting and receiving a pulse since the speed of sound is known. As stated in Table 1, besides the determination of the fill level by implementing different kind of sensors additional data may be obtained. These sensors monitor other parameters related to the status of container such as position using GPS or motion sensors to register container collections, movement to detect possible vandalism.
Disadvantages of Current Solutions
The solutions available on the market suffer from two major disadvantages.
First disadvantage is related to the usage of the ultrasonic sensor. Trash is non-uniformly distributed inside the container. Simple distance measurement leads to false fill level measurement. Although several software procedures were proposed to increase the accuracy of this sensor, unfortunately, results remain poor. By using multiple sensors, fill level can be determined more precisely, however the cost of the system also increases. So, this is usually not a commercially preferred solution.
Second disadvantage of the current solution is that it is partial and incomplete. The waste management cycle starts with the garbage being produced, then it gets disposed at the local trash bins or other garbage collection points. Afterwards, it is being collected by a garbage collecting company and brought to garbage depot where it is being sorted and sent for recycling, destruction (burning) or storage. A complete waste management should be involved in trash bin fill level measurement, route optimization of the trucks and contribution to the recycling process by easing out the sorting process, which is currently manual and slow. Current smart waste management services do not offer any solution with regard to the recycling process.
Ideally both of these disadvantages could be resolved…
Recycling of trash is a complex task. Obstacles that may be encountered in implementation of this task are as follows;
- recyclables are distributed throughout the city (municipality) and collection of recyclables and other materials is complicated;
- the city trash and recyclable materials are generated not only in every home, building and production facilities, but also in public spaces (streets, parks);
- each recyclable has a different strategy for the end of life management.
Recycling of used products could be simpler and cheaper through the establishment of a system for automated management of product lifecycle, whereby, the technical information about the product must be incorporated in itself during production. Information such as the materials of which the product is made, ways to recycle, repair or installation of its elements must be contained in the product itself. Thus, organizations responsible for waste collection could automatically search for the contents of the container or special items and organize collection service according to this information. Should this happen, there would be a huge reduction in the quantity of municipal solid waste, which would make waste management activities become cost-effective for both the city and citizens.
Product management at the end of life-cycle could become widespread thanks to the technological improvements in the identification and the use of Internet. There are several innovations for automatic identification of products, among which RFID tags have shown great potential in applications such as management of the products . Waste management is another promising application area of RFID technology.
Systems for the measurement of trash bin fill level discussed above must be augmented with the implementation of RFID technology. The augmented system must be realized so that there will be exchange of information between cloud (dispatcher center) and trucks for waste disposal or directly for the trash bins where the information from each bin would be conveyed to the cloud and the product life cycle management could be realized and recycling process could be eased.
At the time of trash disposal, the material to be recycled could be identified using RFID technology. Data obtained in this way can be passed through the cloud to retailers of secondary raw materials, as well as other interested parties, such as Internet services for the sale of products, or institutions responsible for hazardous waste. In this way, it is possible for waste material to be recycled or reused before the garbage collection services pick it up. Even if the waste is collected by municipality services, sorting, storing and recycling would be eased up at the recycling facilities.
RFID technology can increase the rate of recycling of different types of waste of components such as batteries, electronic waste, hazardous substances and valuable recyclables. Sorting different types of batteries could be cheaper and easier with the use of an RFID tag that is placed on the battery. RFID tags placed on electronic equipment could contain information about the possibility of dismantling, the content and type of constituent elements, the method of selection of components in dismantling and recycling possibilities of individual elements of electronic devices (e.g. white goods where the housing element that can be reused).
Next to the RFID, weight sensors should be added to the trash bin to improve the fill level measurement. By fusion of sensory information (ultrasonic + weight) the classification of trash could be done and overall fill level estimation would be improved.
In the system advocated above, fusion of sensors, identification technology and internet connectivity will lead to a uniquely smart disposal trash bin. Together with the cloud, these trash bins would become irreplaceable element in the waste management cycle where the collection, transportation, storage and recycling of waste could be automated. The use of RFID technology in waste collection services not only increases efficiency of waste management through automation, but also increases environmental responsibility which is one of the pillars of the Smart City.