JSDEWES: Life Cycle Assessment of Shared Dockless Stand-up E-scooters in Sweden

The objective of the study is to understand the environmental burden and the energy and resource utilisation of shared stand-up ESs in Swedish cities, as well as to understand which factors have the largest impact on the resource and energy efficiency of these ESs.

The performed study is a comparative attributional LCA. Two main cases are analysed: Case 1 corresponds to the first-generation ES model that dominated the Swedish market during 2018−2020, which has a low weight and a short lifetime mileage and does not have a swappable battery, and Case 2 corresponds to a significantly heavier ES that was introduced in Sweden from 2020 onwards with a swappable battery and with different scenarios for the lifetime mileage. The functional unit used in this study is the passenger kilometre (pkm). The system boundaries of the ES life cycle in this study, which include the production, the transport of the ES from the manufacturer to the user, the use phase, and the end-of-life phase, are shown in Figure 1.

The Environmental Footprint method 3.0 is used for the impact assessment [14]. The included environmental impact categories are:

• Climate change, indicated by radiative forcing as global warming potential, measured in g CO₂ eq. (summarised by GWP₁₀₀ factors according to IPCC 2013 baselines [15]).

• Resource use, minerals, and metals indicated by abiotic depletion potential (ADP) for minerals and metals measured in mg Sb eq. (Antimony equivalents).

• Total energy demand or cumulative energy demand, measured in MJ of the higher heating value of fuels.

• Photochemical ozone formation, indicated by tropospheric ozone concentration increase, measured in g NMVOC eq. (Non-Methane Volatile Organic Compound equivalent).

Table 1 presents the main characteristics and data used for the two cases. More details are given in the following sections and the Appendix. The results should be used to identify which parts of the lifecycle contribute most to the ES’s resource use and environmental impact and answer the two hypotheses in the introduction.

The ESs were assumed to be manufactured in China, and the batteries – in South Korea. The emission factors for the electricity mixes for these countries, as given in Ecoinvent 3.8, were used in the simulation for the production phase. The transportation of the batteries from South Korea to China was not included. Due to a lack of data on the origin of the materials used to produce the ES, market values from Ecoinvent 3.8 were used. The library for a cut-off by classification was used for all material streams. A proportion of recycled material (15–20%) was considered for aluminium.

The production steps for both cases were assumed to be identical, and the following processes were included: powder coating, aluminium sheet production, wire drawing for steel, and injection moulding. The production processes were assumed to use electricity (medium voltage) and heat for process heating. The electricity demand is based on data given by the ESSS companies, except for processes of aluminium arc welding and powder coating, based on Ecoinvent 3.8 data on the production of electric bicycles.

Repairability is one of the main changes from the first-generation to the later-generation ES. This study assumes the number of reparations per 10,000 trips based on data from the ESSS companies for the newer generation ES (corresponding to Case 2), considering a selection of spare parts. Table 3 shows the included spare parts in each case. For Case 1, fewer parts are considered repairable, but the same frequency of repairs per 10,000 trips as in Case 2 is used.

The results presented in Figure 3 show that, for both Case 1 and Case 2, the production phase (including raw materials, production of components and manufacturing) is the main contributor to the environmental impacts across all investigated impact categories. For Case 1 ES, the second largest contribution to the environmental impact across all the impact categories comes from collecting the ESs for charging, maintenance, and redistribution (hereafter called collection & redistribution).

For Case 1, the production phase and the collection & redistribution together account for 93%, 90% and 97% of the climate change, total energy demand, and resource use minerals and metals, respectively. Charging has the smallest contribution to the climate impact, at only 0.6%, but accounts for 6.5% of the total energy demand. The reason for the smaller contribution to the climate impact is the low emission factor of the Swedish electricity mix. Transportation of the ES from the manufacturing site to the user contributes 8% to the total impact of photochemical ozone formation.

For Case 2, the spare parts in the use phase generate the second largest contribution to all the impact categories. It should be noted that the production of spare parts is considered during this phase. The production of the 0.4 extra batteries assumed to be needed for the ES with swappable batteries is included in the production phase. The maintenance and redistribution for Case 2 ES contribute to 10% of the total climate impact. The contribution to the total energy demand is similar for the three parts of the use phase, i.e., charging, collection & redistribution, and spare parts. The largest contributions to the photochemical ozone formation come from the production phase, followed by spare parts and collection & redistribution. Transport from the manufacturing site to the user contributes almost 8% of the total impact of photochemical ozone formation.

Case 1 and Case 2 are similar in that the battery, aluminium alloy and printed wiring board generate the largest contributions to the climate impact and cumulative energy demand from the production phase (Figure 4 and Figure 5).

Figure 6 displays the absolute impacts for the base cases of the two ESs. Only the impact of the spare parts increases from Case 1 to Case 2. All other processes decrease in Case 2 compared to Case 1, as the lifetime and distance driven increase significantly for the Case 2 ES. Furthermore, more parts are assumed to be exchangeable/repairable for Case 2 ES.

Figure 7 displays the results of a sensitivity analysis of the lifetime mileage of the considered cases. The higher the lifetime mileage, the lower the impact. The result for Case 1 is shown by a horizontal line and text in Figure 7.

The result shows that the total number of km travelled during the ES lifetime needs to almost double to have a lower climate impact than the Case 1 ES. If the lifetime mileage is not doubled for the Case 2 compared to the Case 1 ES, the climate impact will be higher for the Case 2 scooter. The results for the other impact categories are shown in Table 5.

The results of this study show that the production phase is the most important part of the life cycle, contributing the largest share to the overall environmental impacts for the categories: climate impact, total energy demand, resource depletion minerals and metals, and photochemical ozone formation. In line with previous studies results, future efforts to reduce the environmental impact should also be directed towards the production phase. Many countries’ electricity generation and industrial sectors are transitioning towards lower GHG emissions, so the impacts for these parts of the ES production phase will likely decrease. Moving the production of ES or components to areas with better availability of clean energy could be one way to speed up this improvement.

Our results show that aluminium and battery are the two parts of the ES that make the largest contribution to the environmental impacts of the production phase. Using more recycled aluminium or reducing the amount of aluminium could be important efforts to reduce the environmental impact of the production. Previous studies have also pointed this out [5]. Reducing the environmental impact of the batteries could be done in several ways, including the intensified use of renewable energy in production. The need for battery capacity could also be reduced by the right battery sizing or by prolonging the battery lifetime (through improved handling during the use phase, such as avoiding extreme temperatures and complete depletion of charging [20]).

The development of the ES to improve lifetime, robustness, safety, and repairability has led to heavier scooters. The heavier scooter requires using more material, but an increase in the lifetime mileage could offset the larger environmental impact if it can be increased sufficiently. The results of this study show that the lifetime mileage needs to nearly double or more (depending on the impact category) to get a lower impact compared to the lighter ES. Efforts to reduce the environmental impact by improved ES design and choice of materials should also consider the consequences for the ES lifetime mileage. Sustainable solutions should have a low environmental impact from the production and a long lifetime mileage.

The new heavier ES models entered the Swedish market approximately two years ago, and their implementation has been gradual. None of the new ESs has reached a lifetime of 5 years yet, but this is the expected lifetime according to ESSS companies based on observed decommissioning rates. It also substantiates this study’s chosen base case lifetime of the Case 2 ES.

The sensitivity analysis shows the reduced environmental impacts resulting from significantly shorter and longer lifetimes. The lifetime mileages have been calculated assuming the same utilisation rates (trips per day and trip lengths) for each lifetime. If the utilisation rates can be increased, the lifetime mileage can be increased with more modest lifetimes in calendar days. Future evaluations should follow up on the total lifetime mileage of the new ES models. The lifetime mileage is also important for cities implementing new policies to follow up. The lifetime mileage depends on the use intensity, which can be impacted by, e.g., local regulation. Regulations that limit the number of actors and/or the number of ESs for each actor can influence the use intensity of the ES, which in turn can significantly affect the environmental impact of the ESs.

The results show that the environmental impacts of the collection of ES or batteries for charging, maintenance and redistribution have been reduced significantly due to the lower demand for transports by using swappable batteries and by replacing the vehicles used for collection with smaller ones with less environmental footprints. ESSS companies further develop this positive trend by enabling swapping stations where users are nudged (e.g., through free rides) to swap depleted batteries, reducing the need for transports.

The charging of the ES, i.e., the use of electricity during the use phase, gives a small contribution to the overall environmental impacts for both Case 1 and Case 2 ES. The Swedish electricity mix has a relatively low environmental impact; in another context, with electricity having a significantly higher environmental impact from production, the contribution of the use phase would increase significantly.

The ESSS companies have systems for reusing parts of the ES that are still functional when the ESs meet their end of life. The reuse of spare parts was not considered in this study. If spare parts are extensively reused from decommissioned ES, the estimated impact of spare parts in this study is overestimated. However, the environmental impacts of spare parts, as estimated in this study, show the environmental benefits of reusing these components. For example, if 50% of the spare parts are reused parts from decommissioned ES, the impacts from the spare parts could be reduced by 50%.

The ESSS companies also have systems for reselling refurbished ESs that are still functional when they meet end-of-life in their service. Resell programmes are not considered in this study. Previous LCA studies of ES have omitted the end-of-life because most parts of the ES have ended up in a stock of spare parts [7].

One important environmental impact category for urban transport is particulate matter (PM). This category was not included in this study since no appropriate data are available for the direct emissions from the wear of tyres and breaks during the use phase. For other vehicles, this is the main source of PM. The other source of local PM emissions from the use phase would be the vehicles used for collection and redistribution. All other PM emissions will occur at other places (e.g., at the sites of material, component, and ES production, by transport from the manufacturing site to the users or at end-of-life), which is not considered to have an impact on the local air quality in the cities where the ES are being used.

To compare the impact of the shared ESs to the other modes of transport that the ESs trips replace gives an additional aspect to their environmental impact. It was not the focus of this study, but according to previous studies, shared ESs have a higher climate impact than the modes they replace, whereas privately owned ESs have a lower climate impact than the modes they replace [10]. If looking into details, the shared ES has a higher climate impact than the active modes of transport, such as walking or biking [6]. Compared to electric bikes, they also have a higher climate impact [5]. However, when it comes to public transport, it could be better or worse depending on the actual lifetime mileage and the specific impact of the public transport (comparative figures vary between 80−130 g CO₂ eq./pkm for buses and between 10−60 g CO₂ eq./pkm for trams or commuter trains, based on the results from [5], [6]. It is most likely that the ES has a lower impact than personal cars. Central estimates of the climate impact from a life cycle perspective for a midsize diesel-driven car is 167 g CO₂ eq./km and 183 g CO₂ eq./km for a gasoline-driven [21]. Cars smaller than midsize have lower impacts, and many alternative fuels also result in lower impacts.

The comparison of the environmental impact of the shared ESs in Sweden indicates that there have been significant improvements since the first ES models were introduced. However, compared to transport modes replaced by ES, the climate impact of ES is still high. The most important factors for the environmental impacts of shared ES are the production phase and the lifetime mileage of the ES. The lifetime mileage is determined by the utilisation rate (trips per day per ES and trip lengths) and the lifetime of the ES. The utilisation rate and lifetime or lifetime mileage are parameters that policymakers should follow up on to estimate the actual environmental impacts of shared ES in their city.

Even if it does not have a significant impact on overall energy use and climate impact, it should be noted that losses during idle time could be significant. This issue was not investigated in the present study, but according to [22], losses from the battery during idle time could be as much as 30% of total consumption during the use phase.

The impact of ESSS on people’s mobility in cities is complex. Although some studies have analysed the types of trips being replaced by ESSS trips, there are likely additional indirect effects on public transportation, congestion, and other factors. Further research is needed to comprehensively understand the environmental impact of ESSS.

In addition, future studies should investigate the environmental impact of the digital systems required for the sharing service. This aspect was not considered in the present study or the previously mentioned LCAs of shared ES services.