# Modern Technologies for Waste Management: A Review
## 2 Overview of Technologies
### Automated Vacuum Collection System  
Most of the municipal waste is collected door-to-door by garbage collectors driving garbage trucks. It takes effort to optimize their routes with consideration of all factors. Truck travel distances are found to be sensitive to factors such as collection frequency, truck capacity, volume ratio of the truck compartment, and waste density [42]. As an alternative, a system of waste pipes called automated vacuum collection (AVAC) has been proposed and implemented over the years. The principle behind that solution is fairly simple: once waste is thrown into the inlet, it is transported by the vacuum principle through pipes into the terminal where waste is collected. Although AVAC is not the newest topic in waste management, it is still not very common. Some cities, such as Bergen, Norway, a medieval city, have adapted such a system. In 2008, Bergen's city council decided to shift from containers to an underground waste collection system. It was opened in 2015, since then providing 24 h a day, 365 days a year access to waste inlets collecting household waste. Later in 2021, it was extended [43]. One of the most popular AVAC systems is MetroTaifun: it is present in over 40 countries, starting with the city of Makkah, Saudi Arabia, to Sejong Happy City 5-1, South Korea. This system is especially more common in Nordic countries (Finland, Norway, Sweden, Denmark) [44]. There have been theoretical studies considering economic and ecological profitability. [PERSON] et al. [45] considered pneumatic waste pipes in a highly and densely populated area, like New York City. Current conventional waste collection requires high economic and environmental costs to sustain such an operation. In this study, three specific cases were considered: the High Line pneumatic facility, the Second Avenue Subway pneumatic facility, and alternatives for upgrading the existing Roosevelt Island pneumatic system. It was found that the costs and impacts of AVAC installations in relation to conventional collection differs due to design characteristics (i.e., the number of waste fractions, length of tube network, number of inlets) [45]. [PERSON] et al. [46] studied a small-scale solution in an airport over time using the Life Cycle Assessment (LCA) with ReCiPe indicators and IPCC2013 GHWP100a. These indicators provide information on impact points by categories of damage and equivalent kilograms of CO\({}_{2}\) emitted into the atmosphere. In a renewable energy-mix scenario, pneumatic systems have lower impact compared to truck systems, but in the Spanish national energy mix (2014) scenario it is the other way around [46]. Another LCA study was carried out by [PERSON] et al., with specific focus on the biodegradable fraction. The results indicate higher electricity consumption by pneumatic waste pipes in comparison to door-to-door systems, when the bulky fraction includes the biodegradable fraction, but comparable consumption when the organic fraction is collected separately [47]. [PERSON] et al. [48] studied a hypothetical case of the AVAC system in Helsinki, Finland. In this case, waste pipes showed a weak economic performance compared to vehicle-operated door-to-door waste collection systems. The authors suggest that unstudied technical characteristics of the pneumatic system, such as pipe diameter or different pipe routing, may significantly impact the expenses. This study also shows a significant impact of population density in relation to life-cycle costs (SLCC) [48]. [PERSON] et al. found the majority of pipeline failures are due to attrition, mainly in elbow, connections, and pip-efitting. High glass contents and high transportation rates are the main causes of attrition. This and two previous studies show the importance of the type of transported material in regards to economic performance [46].