*2.1. The Eco-Costs, a Monetized Single Indicator in LCA*

The assessment of the eco-burden of a system is done by LCA. An important issue here is the choice of the indicator that is used for benchmarking. Such a benchmarking indicator can be a so called midpoint indicator (e.g., greenhouse gas, acidification, eutrification, fine dust, human toxicity, ecotoxicity), but the issue here is that every indicator leads to its own optimum choice in product design. A well-known example is the engineering of the Volkswagen diesel: by focusing on CO2 emissions only, and ignoring the consequences for NOx emissions, the strategic decisions of the company lead to losses of several billion euros.

The solution is to apply a so called endpoint indicator, which combines all midpoint indicators in one single score (i.e., damage based indicators like ReCiPe [18] and Ecological Footprint [19], both in 'points', or monetized scores like EPS [20] and eco-costs [21]). There is no single truth in single endpoint indicator systems, since such a system reflects a set of values and assumptions, but it is generally acknowledged that single score systems are needed in LCA benchmarking. A well-documented scientific single indicator system is always better than a set of many midpoint scores of which one or two are selected on the basis of a personal, subjective point of view [22,23].

It is useful to select a monetised single indicator in LCA, since it is related to the concept of 'external costs' (i.e., environmental costs to our society that are not included in the current product costs) and thus enables the comparison with the costs and the market value of the design. In the scientific literature there are two operational monetized systems that are widely applied in LCA: EPS 2015 (a damage-based indicator) [20] and Eco-costs 2017 (a prevention-based indicator) [21]. The advantage of monetized systems is that they do not suffer from the inaccuracies of the normalisation and weighting steps.

For the street lighting system study in Rotterdam, the eco-costs was selected as a monetised single indicator, since it is the most comprehensive system in terms of midpoints, see Figure 2, and it is the most applied system in science as well as design engineering.

**Figure 2.** The total eco-cost system in life-cycle assessment.

The eco-costs system has been developed in the period 1999–2002 [24–26] and updated in 2007, 2012 and 2017 [27]. The system is in compliance with ISO 14008 [28]. A further description of the monetisation factors can be found in [29].

The way the total eco-costs of a system like street lighting are calculated, is explained by Figure 3. The first step in LCA is to determine the so called Life Cycle Inventory (LCI) list of all polluting emissions (CO2, SO2, NOx, fine dust, etcetera) and all required resources (metals, energy carriers, water, land). The system delivers a product or service as output (in this case light), and comprises a lot of subsystems and processes (in this case the lampposts, the cables, the light bulbs, the installation processes, and the end-of-life processes). All these subsystems and processes need material, transport and energy (electricity and heat) as input.

**Figure 3.** The system components of Life Cycle Assessment.

The second step in LCA is called the Life Cycle Impact Assessment (LCIA). The goal of this step is to provide a practical interpretation of the long list of emissions and required resources of Figure 3. According to ISO 14044 [30], this is done via the calculation structure of Figure 2. The substances of the list are classified in terms of their effect, multiplied by characterisation factors, and added up within their own 'midpoint' groups (i.e., climate change, eco-toxicity, acidification, fine dust, carcinogens, etcetera). Then the midpoint groups are combined to 'endpoints' (so called Areas of Protection) after either a monetisation step (e.g., eco-costs), or by 'normalisation' (e.g., 'points' in the ReCiPe system). In the case of monetisation, the 'endpoints' can be added up to a total end-score, in our case eco-costs. (Non-monetised systems need an extra step to weight the relative importance of the points of the Areas of Protection).

LCA calculations can be made either with special software (e.g., Simapro, Gabi, Open LCA), or by means of look-up tables in excel. These tables are available for eco-costs of pure emissions, but also for the aggregated eco-costs at the level of materials (metals, plastics, wood etc.), manufacturing processes (deep drawing, turning, welding, extrusion, coating etc.), components (lamp bulbs, printed circuit boards, PV panels), transport, energy, and end-of-life processes [31]. These look-up tables have been calculated with the use of formal LCI databases, and enable a simplification of the final LCA calculation (without losing accuracy) in a way that is quite similar to cost accounting in projects (multiplying quantities with its eco-costs scores of supplies and processes, and adding it up to the total eco-costs). An example of such an LCA is given in Table 1. The table provides output data (in eco-costs and in CO2 equivalent) for one classical lamppost (type 'Kegeltop' on a 4 m pole). Note that the calculations in Section 3 (Results) show data per year, under the assumption that the lifespan of a lamppost is 40 years, and per street, under the assumption that a street has 100 lampposts.


