Making it Concrete: Analysing the Role of Concrete Plants’ Locations for Circular City Policy Goals

Increasingly, space for remanufacturing is seen as the most valuable resource to achieve circular economy (CE) policy goals, in particular for cities. However, in many cities, industrial urban areas are increasingly subject of – mostly circular designed - residential redevelopment. The proposition of this paper is that these diminishing industrial areas host, at least potentially, essential functions necessary to “close the material loop.” The reason why policy makers neglect the necessity of remanufacturing capacity, is because it is difficult to pinpoint the “ideal” geography of a circular loop. Most (circular) products can be transported limitless, thus their remanufacturing functions can be located around the world. But what if a critical material cannot be transported limitless and has circular potential? Therefore, this paper focusses on concrete for two reasons. First, concrete is by far the most abundant material in urban areas. Second, newly/circular made fluid concrete can only be transported for a limited time and distance. The hypothesis of this paper is that concrete plants are and will become essential for circular cities. Subsequently, we focus on the Dutch city of The Hague and combine a Material Flow Analysis with the locations of the concrete resupply chain. Our results show that potentially The Hague has a 100% circular concrete chain, but the importance of its concrete plant is (implicitly) neglected. We conclude that The Hague is illustrative for the problem of many circular cities that are without (implicitly) taking into account the whole circular resupply chain, jeopardized today a future urban CE.

INTRODUCTION
This paper operationalizes the concept of urban metabolism to explore the spatial challenges of urban circular economy (CE) policies. Our arguments start from the paper by Newell and Cousins (2015) on the boundaries of urban metabolism. In their paper, they point out that the concept of urban metabolism is not straightforward and can be perceived within three different ecologies: Marxist, industrial and urban ecologies (see also Wachsmuth, 2012). Without explaining them in detail, they differ in how they use urban metabolism as an analytical unit to study respectively nature-society relationships, quantitative material flows and stocks, and urban complex ecosystems (of sub-systems, cf. Luhmann (1982)). As they continue, all three have their advantages and disadvantages. But, similar to Newell and Cousin's arguments, in this paper we don't state the one is better suited than the other, but emphasize that advantages in our understanding will come if we combine insights from all three. In particular, Newell and Cousins propose to combine industrial ecological with political ecological research. That enables on the one hand to use clear result oriented quantitative methodologies, but simultaneously on the other hand enables to apply qualitative spatial critical socio-economic and institutional approaches. In other words, the concept of urban metabolism is useful to understand relational socio-ecological systems, by applying quantitative material processes.
The goal of this paper is to continue this endeavour and go to the next step, namely the operationalization of the concept of urban metabolism in order to understand its boundaries. The setting in which we operationalize the concept is the CE. It is not the first time the concept of urban metabolism and CE are combined, quite the contrary (Russell et al., 2019;Paiho et al., 2020). Nevertheless, arguably at least implicitly many of these studies quickly see them as synonyms. We, however, state that this is not true. While urban metabolism is a neutral quantitative and qualitative analytical concept examining (im)material, institutional and energy relations and flows within, from and towards cities, the CE is normative as it strives that the existing flows are or should become circular. Another difference is that the CE in essence is a network concept, without a clear geography, or (urban) boundaries. Hence, translating the CE towards an urban context, via thus in this case urban metabolism, is not straightforward. In other words, it is not because the CE is combined with urban metabolism, one then has solved the issue of scale and has clearly defined an urban CE. The misunderstanding here comes exactly from the reason that an urban metabolism is not only a clear quantifiable concept, but also a political ecological one, as explained above. Putted more simply, although thus urban metabolism clearly focusses on the urban, it still remains vague what that urban then exactly entails (Heynen et al., 2006). Indeed, a city is all but a clear defined entity (Brenner and Schmid, 2014). Hence, a circular urban metabolism is maybe easy to understand as a normative discourse, nevertheless, it remains difficult to exactly know what it entails. The reason for this is because it is unclear what the 'urban' entails, where it starts and where it ends. In other words, it is not clear what the spatial contours are of a circular urban economy (see in this respect also Tapia et al., 2021). This leads to our research question: What is the geography of a circular city?
Until today, foremost the quantitative methods dominate both the urban metabolic as CE studies, receiving vast critiques by now (Korhonen et al., 2018a;Korhonen et al., 2018b). While most critiques underlinecorrectlythat we should enhance our insights on the topic of the social and economic elements of the CE, in this paper, we focus on the political institutional part of the CE. We do this because a circular city is in essence a political subject. Different than urban metabolism or CE, circular city as a concept and by now even discourse (Van den Berghe and Vos, 2019), did not emerge within a dominantly scientific community (cf. Wolman, 1965), but within policy maker environments. As described by others (Williams, 2019;, the policy ambition to become a circular city has recently become embraced by numerous city governments around the world, such as Paris, London or Amsterdam (Williams, 2021). The core of these urban policy goals is to avoid waste as much as possible and to use no longer virgin materials. Different themes are then chosen to focus on, but a constant is a focus on the built environment. This is not a coincidence, because the built environment and construction sector is the major reason of the vast use of virgin materials and the production of waste of cities (UN, 2019).
The reason why in this paper we attempt to explicitly research the geography of the circular city, is because recently increasing authors have signalled that the current application of the circular city policy is at least implicitly not being used in the first place to make cities more circular, but to accelerate the development of residential and commercial land use. As explained by Van den Berghe and Vos (2019) and Williams (2019), a circular city exists if both the outcome of the built environment, thus a circular designed built environment, is combined with a circular functioning built environment. The latter entails that a circular city policy also takes into account that the material flows going to (cf. construction) and coming from (cf. demolition/harvest) the built environment are processed in a circular way. Put otherwise, a successful circular city implies that the whole existing chain of the built environment is circular. This implies that not only supply and demand of materials is matched, but also the often forgotten step-in-between, the remanufacturing, is taken into account. It is in most cases an utopia that supply and demand match perfectly. This is because of two reasons. First, realistically there is a time difference, which implies that materials have to be stored temporally before they can be used again. For this reason, increasingly cities are thinking of creating so-called circular material hubs (Loeber and Snoek, 2020), areas where materials can temporarily be stored. Second, mostly materials cannot be used one-on-one from a demolished building into a new building. Mostly, materials need to be modified (e.g. painted). Sometimes, materials have to be processed entirely to become useful again. Examples are steel or concrete, abundantly present in urban built environments, that in many cases have to be melted or grinded respectively before they can be circularly be remade into new steel and concrete.
To answer the research question the article is structured as following. In the next section, we explain the conceptual challenge of connecting space with networks, or geography with relations, exactly the conceptual challenge of a circular urban metabolism as explained. Next we introduce our conceptual framework presenting a circular (re)supply chain, not only composed by the source and destination of circular materials, but also including the necessary connecting functions in-between. Next, we introduce our case study of the city of The Hague in Netherlands, a city which has the policy ambition to become a circular city, but is characterized as a foremost residential and commercial land use city, without the presence of large industrial areas. As we will show, exactly these areas and the (potential) circular functions it hosts, will come crucial in the (near) future to achieve circular city policies. However, the current land use policy of The Hague does all, but safeguarding these areas, paradoxically thus by referring to its circular city policy. We end with a discussion and conclusion. Hobson and Lynch, 2016;Deutz et al., 2017;Haezendonck and Van den Berghe, 2020;Salomone et al., 2020;Van den Berghe and Daamen, 2020;Williams, 2021). Although obvious differences in analytical focus, subject and methodologies exist between these works, what they have in common is stressing out the challenge of taking into account the spatial systems boundaries when dealing with sustainable development, of which the CE is the most recent popular advocate (Köhler et al., 2019). In particular Korhonen et al. (2018b) argue that the choice of unit of analysis and the accompanying methodological approaches should always be interpreted together with a critical reading, otherwise it can lead to "scale misperceptions in the interpretation of the applicability of the study results [. . . whereby for example] a microeconomic-level success can be falsely understood as a contribution to the overall macroeconomic-level sustainability" (Korhonen et al., 2018b).
Until today, arguably the role of scale within the CE literature has been used merely as a way to explain the starting point of the research, rather than being the subject itself. For example, Pomponi and Moncaster (2017), exploring the CE for the built environment, categorized scale using three analytical levels: 1) the micro level, which focuses on materials and components, 2) the meso level, which focuses on buildings, and 3) the macro level, which focuses on cities. Others like Kalmykova et al. (2016), Reike et al. (2018) or Bauwens et al. (2020) use local/regional, national or global as their divisions. We argue, however, that this is not straightforward. The at least implicitly 'mistake' in these studies is namely that scale is seen as a given. In contrast scale is not an objective reality, but influenced by many path-and contextdependent processes of structure and agency (Elder-Vass, 2010). Different processes of regulation eventually lead to different regimes of accumulation (Jessop et al., 2008) at which the production, circulation, realization and interpretation of value are regulated (Savini, 2019).
Bringing this back to urban metabolism and circular cities, seeing scale as such, fits well with seeing the city as a social boundary object, and seeing the city as part of a relational socioecological system, as argued by Newell and Cousins (2015). In other words, urban metabolism or circular cities are not a given, but part of an ever-changing path-and context-dependent process of structure and agency. This implies that policy measures taken to achieve a circular city policy goal, have effects not only on the policy area related to the policy domain (e.g. a municipality and its administrative area), but it also effects the (im)material relations coming to and from the city in particular (cf. the urban metabolism).
If one is analysing a circular city, it is necessary therefore to take two system boundaries into account: a political one, and a network one. The first one is related to the level the policy goal is spoken out of, and its related administrative area. This can be from an international level (e.g. the European Commission) to a local level (e.g. a municipality). The network one is related to the particular material and/or immaterial flows taken into account. Finding the system boundary of a network is less obvious than the political boundary. A network is namely in most cases limitless. However, a network can be spatially demarcated by taking into account the spatial boundary one focusses one, in this case thus the political one (e.g. a municipality), and the thematic boundary (e.g. organic flows, financial transactions, labour transfers, . . . ) (see in this respect Menzel and Fornahl, 2009). Although always arbitrary, one will detect that the relevance of the network at some point decreases significantly for the place taken as the starting point, and this then can be seen as the relevant network system boundary. Now, one has two system boundaries that together are the system boundary of the circular city taken into account. The operational problem is, however, that in this globalized world, most materials and immaterials travel around the world. This makes it difficult to demarcate the relevant network system boundary, and as such it is difficult to examine 'action (cf. measures) and reaction' when circular city policies are executed. Understanding this is essential, because only as such research can analyse how a measure taken within the political administrative area (cf. a circular city measure), affects the network it is part of, both within the area as beyond. As such, one can see how a policy measure affects other policy areas. The advantage is hereby that one can see if there is a so-called "problem displacement" going on, a concept well-known within political geography, whereby a policy (environmental) measure taken into one place to 'improve' a certain situation, worsen the one in another place (cf. Dryzek, 1987;Emel andPeet, 2001 [1989]). In the next section, we explain how we operationalize the "action-reaction" of circular cities.

METHODOLOGY
In this section, we first explain the political system boundary taken into account, namely the Dutch city of The Hague. Next we explain why we focus on concrete, among the numerous possible (im)materials relevant within the CE. Then we explain our conceptual framework and how we will calculate the different steps to fill in the framework.

The Hague and Its Circular City Policy
The Hague belongs to the so-called "G5-cities," or the five biggest cities in Netherlands (Amsterdam, Rotterdam, Utrecht, The Hague and Eindhoven). This group of five is not an institutionalised set of administration, although one arguably can say that these five do have more administrative capacities. To some level, arguably that is one of the reason that all five cities have in one way or another visions and policy developed in line with the 'newest kid on the block', the CE. Amsterdam is worldwide known as a frontrunner (Williams, 2021), but also the others have clear policy documents to become a 'circular city'.
Similar to most circular city policy documents, The Hague focusses on three important material flows in its city (Den Haag, 2018): 1) biomass, or organic waste, 2) construction and demolition waste (CDW), and 3) critical metals. In this paper we focus on CDW. The Hague explains that at the moment 95% of the CDW is already being recycled, but almost exclusively "down-cycled," in particular for road foundations. Therefore, the policy document states that the built environment has to be circular designed and combined with a "material passport," explaining what and how much materials are in buildings. The document also states that there is a need for a physical "market place" where materials can be stored and sold. As we will explain further, this can be labelled as a circular material hub, a concept many cities explore (Ramli, 2021). For our paper, interestingly is that the policy document is not appointing the land use functions that re-make, re-fit or re-manufacture the old materials into new circular materials.

Circular Concrete
In Europe, the average composition of CDW consists of 85% stony waste (Gálvez-Martos et al., 2018), in particular concrete. Hence, avoiding the use of virgin concrete can result in significant ecological improvements (Huntzinger and Eatmon, 2009;Nußholz et al., 2019). Generally speaking, there are four possible ways of dealing with stony waste, beyond thus the "traditional" land-fill (Zhang et al., 2018): 1) recycling aggregate for brick manufacturing, 2) on-site breaking for road base filling (a very popular and widely applied process, but which can be labelled as "down-cycling"), 3) recycling aggregate for prefabricated components, and lastly 4) recycling clean aggregate for structure concrete. The latter is the most impactful and can be labelled as "up-cycling" and implies that old concrete can be used as new concrete. In principal, it is possible to recycle 100% of concrete with the existing technologies, of course neglecting market and cost and benefit conditions, and also neglecting the vast amount of (fossil) energy and water needed to support the process. Nevertheless, even taking these into account, the ecological gains of up-cycled circular concrete, thus avoiding the use of virgin materials, remain significant (Zhang et al., 2019).
Without going further into (very technical and socioecological) calculations (cf. Meyer, 2009), in this paper we go beyond the "yes, but" discussion and take the proposition that concrete can be 100% circular reused. Following this proposition, one can see the city not as a source of huge CDW, but as a huge potential circular material stock. Taking into account that in the contemporary "urban age" (Brenner and Schmid, 2014) most of the construction is and will happen in urban regions, the potential of re-using concrete from CDW is arguably clear. Of course, much debate is going on if at all we should keep on using concrete in our built environment, mostly accompanied with the call for using timber as a construction material (Kremer and Symmons, 2015). Without neglecting the very needed discussion here, we though question the challenge which then would emerge concerning the huge material stock of concrete in our urban built environment that at that moment is no longer of (re-)use anymore. In other words, since we during the last century have accumulated an enormous amount of concrete, maybe it is not a bad idea to try to keep on using this material stock; even more taking into account that we don't have yet the material stock of wood available for a (circular) built environment. Hence, on the short term, all this wood will be virgin, and the (circular) benefits will only arrive on the longer term. Thus, in the meantime, we argue that at least try to reuse the concrete there is available, should not be neglected.
But the main reason why we focus on concrete, is because the material can only be transported for a rather short distance. Different than asphalt, bricks, steel, food, clothes, or almost any material or product used in urban environments, concrete is per definition a local product. The reason is that concrete, an artificial stone, is made by adding water to cement and granulate (sand and gravel). At that moment a chemical reaction occurs whereby the spaces between the gravel become filled with sand, "glued" to each other by the cement. When the material then hardens, one has concrete. Since mostly very large quantities of concrete are needed in a short period, the chemical reaction starts at the concrete plant, whereby then the concrete is transported by very heavy concrete trucks (cf. 14 ton), that keep on mixing the concrete until it can be poured and hardened at the definitive location. The time, and therefore distance, between the start of the process (cf. the concrete plant) and the destination is limited, before the concrete becomes too much hardened. The order of magnitude is around 15-20 km (de Kort, 2017).
Conceptually, concrete becomes therefore an interesting analytical subject. As explained in the introduction, a large debate within the CE literature is namely what geographical extent the closed material networks should have (Tapia et al., 2021;Van den Berghe, 2021;Williams, 2021). Some advocate to have a CE as local as possible, but it remains vague "how local" it then should be. Following this ambiguity, circular spatial planning remains arguably absent and fails until now to link it to what circular functions are essential to maintain or create a "as local as possible" circular material flow. This becomes even more a challenge if space is non-abundant, especially in urban regions, where space is scarce. Hence, if for policy makers the location of circular functions is not very clear, and therefore its importance is not clear, the land use function "loses" to other urban land use functions, in particular residential land use functions. In many aspects, this is a rather 'logical' explanation of the evolution of ). Subsequently, goods and products are transported into city centres, illustrated by the vast increase of all different types of (urban) transport modes (Hall and Hesse, 2012). But for concrete, there is thus a geographical limit. Hence, if a city wants to become circular, whereby waste becomes input, for concrete it will therefore need to host a concrete plant within or nearby (with a maximum of 15-20 km) its contemporary and also future construction and demolition locations, as these two will become connected. Note that of course concrete could also be reused as modules, but we argue that it is an utopia that there will be no need any more of fluid concrete, hence the 15-20 km limit.

The Circular Supply Chain
If waste becomes a commodity or output becomes input, one moves from a linear to a circular material flow. In economic or logistical terms, the supply production or construction chain becomes here a re-supply chain. The difference thus with the linear supply chain is that a same location is at one point the supply of materials, when it is demolished, and at another point is the demand of materials, a circle thus. Sometimes a location is even both at the same time, for example when a building is renovated or adapted. For concrete, this implies that when a building is demolished, old concrete is removed from the supply location, and, before it is brought to the demand location, is collected and stored, which could be the building' site itself, but mostly is another location. As explained, it is namely an utopia that concrete can one-on-one be reused in a new construction, not only in terms of fitting, but also in time. To solve this, increasingly cities are exploring the potential of a so-called "circular material hub," where thus materials are stored temporarily and even can be combined with a market function (Ramli, 2021). However, what these hubs do not include, it the possibility to adapt the materials and goods (Williams, 2020). For concrete, this implies a function is needed that broadly is able to fracture the old concrete into small particles, that subsequently can be remade into liquid new concrete. To some extent, these functions are already known, namely the current concrete plant, this with the difference that almost none of those have a fracturing function. Our conceptual framework presents the circular resupply chain of concrete ( Figure 1). It shows three steps: a supply of old concrete (cf. demolition or "harvesting"), a remanufacturing place where the old concrete is made into new concrete, and a demand of circular concrete.
In the following parts, we explain how we calculate the different steps to visualize and analyse the circular resupply chain of concrete in The Hague.

Supply and Demand
To quantify the metabolic reproductive system of concrete, we calculated the material stock of concrete in the Hague and the inand outflows generated by this supply from 2020 to 2025. To put the size of the concrete stock within our case study into perspective, we calculated the total material stock of the built environment of the Hague. Together with the construction and demolition agenda of the municipality of the Hague and the available concrete mortar plants, the reproductive capacity of concrete per year was calculated.
Supply: calculation of the material stocks for the case study. The building material stocks within the case study were calculated based on the methodology by Verhagen et al. (2021). The public spatial dataset of the Netherlands, the BAG3D (2020 version), was combined with the material intensity data of Sprecher et al. (2021) for the municipal boundaries of the Hague. With the use of the BAG3D dataset, it was possible to identify the following residential buildings types: detached houses, row houses, apartments and high rise. For utility buildings, the following building types were identified: offices, commercial buildings and other types. The BAG3D dataset also contains information on the floor area, building type, year of construction and the building height. The material stocks per building were calculated as follows Materials j,k,l (tonnes) MI j,k,l tonnes m 2 pFloor area m 2 (1) Where the material intensity (MI) for each material (j) was calculated based on the building type (k) and the year of construction (l). The following building materials were included in the quantification: aluminium, bitumen, brick, cast iron, ceramic, concrete, glass, gypsum, roof gravel, steel, wood, and others. The category "other" contains a multitude of materials which were difficult to identify and quantify separately. The material intensity of the building stock in metric tonnes per m2 of building floor area is shown in section 4.1 of the results to illustrate the division of building materials in the case study.

Supply and Demand Over Time
We used the construction and demolition agenda of the municipality of the Hague to calculate the concrete supply and demand of its built environment over time. The included period for this data is from 2020 to 2025, and the data includes the amount of floor area (m2), and the types of buildings planned to be built. The buildings planned to be demolished were based on the location of the planned construction projects and we identified the corresponding building characteristics from the BAG3D dataset. In total, 1,839,406 m 2 of floor area is planned to be constructed, while 2,647,786 m 2 of floor area is planned to be demolished in the included timeframe. We calculated the materials in the buildings planned for demolition and construction based on the method explained before. Though the construction and demolition agenda contained a considerable amount of data, some assumptions had to be made to be able to calculate the in-and outflow of building materials over time. Some buildings have in reality multiple roles, such as a residential and a commercial function. In our analysis we only used the building function with the largest share of floor space. Also, the municipal demolition and construction agenda is more accurate for the earlier years, as not all the future construction and demolition projects were already included for the later period. We use this data in our research to visualize the potential size of material flows, and how the construction and demolition flows compare to each other.

Geography: Origin-destination (O/D) analysis of the concrete spatial remanufacturing capacity
To quantify the impact of the relocation of concrete mortar plants within the Hague, we used an origin-destination analysis (O/D analysis). We used an overview of the concrete production plants in the province of Zuid-Holland (de Kort, 2017), and the location of the demolition and construction projects. This analysis was applied using ArcGis Pro. The Google Maps Street data is used in the O/D tool of ArcGis Pro to calculate the distance travelled by road between the locations. We calculated the travel distance and travel time in the current and future situation with a relocated or removed concrete plant in the case study. We illustrate this analysis in a GIS map with the demolition and construction projects and the corresponding concrete plant used in the scenario.
According to de Kort (2017) in general the distance to concrete plants is ideally 15 km. To calculate the maximum viable range of transporting concrete within our case study, we used the 'service area' option within ArcGIS, using the Dutch National Road Transport shapefile (NWB, 2021).

CO 2 Footprint of Concrete Transportation
To assess the increase in CO 2 emissions of concrete mortar transportation, we used the travel distance calculated from the O/D analyses. We assumed that a concrete truck with a net weight of 14 tonnes can transport 9m3, or 21,6 tonnes of concrete, resulting in a total transport weight of 43 tonnes (Betoncentraal, 2021). Together with the transport distance, back and forth, and the resulting CO 2 impact of transporting concrete in kg CO 2 /ton/ km we calculated the overall CO 2 impact of the transportation of concrete between the concrete plants. The impact of transporting concrete in (0.154 kg CO 2 /ton/km) was obtained from a Dutch report made for the Dutch ministry of infrastructure and the environment (CE Delft, 2013).

Material Stocks Within the Municipal Boundaries of the Hague
Of all calculated building materials, concrete is by far the biggest material stock in the case study with 3.4 × 10 7 metric tonnes ( Table 1). All the other materials range from 3.8 × 10 4 metric tonnes for ceramic roof tiles up to 7.5 × 10 6 metric tonnes for brick. The results in Figure 2 illustrate the material intensity within the municipality of the Hague, ranging from 0.5 tonnes/m 2 to 49 tonnes/m 2 . Especially in the city centre and the high-rise commercial buildings area a high material intensity can be observed. Taken together, we find a weight of 5.1 × 10 7 metric tonnes for the built environment of The Hague in 2020. Overall, the demand and supply of concrete are fairly matched. In our case study (Figure 3), the supply and demand of concrete decreases over time from 891 kilotonnes supply and 765 kilotons demand in 2020, to 12 kilotonnes supply and 48 kilotonnes demand in 2024. The available concrete supply and demand varies per year. In 2020 there is an oversupply of 126 kilotonnes of concrete within the municipality of the Hague, while in 2021 there is a shortage of 134 kilotons. Also, in comparison with the material stock in 2020, the concrete outflow through demolition in 2020 is 2.6% of the stock, while the material inflow through construction is 2.2%.
The overall demand and supply of concrete decreases over time due to the limited agenda and planning of the construction and demolition projects. It does however give an indication of the variation between the demand and supply of the construction sector within our case study. A more balanced supply and demand of concrete often increases the recycling rate of materials.
The spatial distribution of potential circular concrete plants.
We now have estimated the supply and demand of concrete in The Hague. One could thus conclude now that The Hague needs around 750 kilotons of concrete mortar each year to fulfil the demand of the construction sector. Even more important, a comparable amount of concrete will be available from demolition each year.
Within the surroundings of the Hague, four of the 12 nearest concrete plants are reachable within 20 km (Figure 4). Increasing the transportation distance to 30 km, a theoretical upper limit for wet concrete mortar, expands the availability of concrete mortar plants to 10 for the city of the Hague. Though the available capacity of concrete plants can be increased by expanding the transportation distances, this also has impact on the drying of the concrete mortar, pressure on the road network, and the resulting CO 2 emissions from transportation.
O/D analysis and CO 2 impact of transportation. On average, the distance of all the demolition and construction projects in the Hague to the closest concrete plant, located in The Hague, is 7.0 km and 11.8 min, or 6,849 km and 11,612 min in total. As shown in Figure 5, closing this concrete plant will redirect all the concrete flows to the second closest concrete plant in Delft, increasing the average distance to 15.5 km and 18.1 min, or 15,458 km and 17,755 min in total (Table 2). Furthermore, this increase in travel distance produces an additional 4,947 tonnes of CO 2 emissions per year (Table 3).  Switching from the concrete plant in the Hague to the one in Delft increases the total distance by 126%, increases the travel time by 53%. This has implications for the concrete drying time the impact of traffic jams and a larger environmental impact from transportation, in particular since concrete trucks are large trucks (43 tonnes), with a significant impact on the already saturated roads.

DISCUSSION AND CONCLUSION
This paper operationalized the concept of urban metabolism to explore the spatial challenges of urban CE policies, also known as circular cities. We developed a conceptual framework that is able to visualise and analyse the different steps of the complete resupply chain of concrete. We applied this conceptual framework on the Dutch city of The Hague. The particular characteristic of concrete is that when the chemical process starts, it can only be transported for a limited time and therefore distance. For Netherlands, the maximum distance is around 15 km, before the concrete becomes too much hardened out and cannot be poured anymore. As such, choosing concrete as material is promising as it can overcome the conceptual challenge of knowing on what scale a material resupply chain should be organized. Thus different than wood, steel, glass, bricks, and so many other materials used in our built environment  Frontiers in Built Environment | www.frontiersin.org October 2021 | Volume 7 | Article 748842 8 that can be transported limitless, concrete makes the challenge of a circular built environment and its geographical resupply chain thus clear. Our empirical results show that The Hague can at least in potential (taking into account that concrete could be 100% circular reused) become almost self-sufficient for its future demand of concrete. We showed that this potential is, however, jeopardized because there are plans to close its existing concrete plants in The Hague, paradoxically because of the plans to redevelop the area wherein they are located -The Binckhorst -, as a circular built residential and commercial area. We mapped where then the concrete could come from, and showed that there is only one concrete plant at the moment that can serve within the 15 km range the whole area of The Hague with (circular) concrete, namely the one of Delft. We calculate that, however, only with this arguably small addition in distance, the overall needed driven kilometres and linked CO 2 emission are significant. Even if all this transport would be electrified, still the enormous addition of driven square meters to the already saturated road networkespecially because we deal here with almost 50 tonnes trucksis not really desirable in dense urban areas.
We conclude therefore that our focus on circular concrete has discovered an important challenge for circular cities, namely the need of (re)manufacturing functions to match supply and demand of materials. If these are not included, and hence are not present within the respectively administrative area, the city with its circular policy is dependent on other municipalities in their attempt to achieve their policy goal. For concrete, this remains within Netherlands, but for other products, municipalities/regions and even Netherlands (Rijksoverheid, 2016) as a whole are thus dependent on locations around the world, locations that host the functions that enable to match supply and demand of circular products. For concrete, The Hague will thus become dependent on Delft. The paradox is, however, that also in Delft the concrete plant's location, the Schieoevers, is being questioned and subject of residential and commercial redevelopments (Delft, 2021).
Although not yet decided, most likely the concrete plant will be closed in Delft or it will have to move to a more southern location in Delft. In any case, the distance from and to the concrete plant to and from The Hague will most likely increase, maybe even beyond the threshold of 15 km.
Our paper shows thus the importance of linking space and responsibility, or in other words, how 'circular sherry picking' can jeopardize a circular city policy goal. We have one clear policy recommendation, namely that it is not enough to pose circular city policies, but also needs a focus on the sometimes difficult choices there have to be made. If not, one could argue that there is (at least implicitly) "circular washing" ongoing. For future research, we would welcome more research that tackles the conceptual difficulty between networks and places, scale and responsibility, or material flows and circular (always normative) economy policies.

DATA AVAILABILITY STATEMENT
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

AUTHOR CONTRIBUTIONS
KV has focussed on the theory and conceptual framework, TV on the methods and results. Both on the discussion and conclusion.

FUNDING
This article is part of the research project Circular Area Development Binckhorst, funded by the Accelerating the Circular Economy Zuid-Holland (ACCEZ), a collaboration between the Dutch Province Zuid-Holland, employers association VNO-NCW West and the universities of Leiden University, Delft University of Technology, Erasmus University Rotterdam, and Wageningen Research University.


Pushing the Limits using Business Model Innovation a Three Pronged Approach and Lessons Learned

In a constantly changing business environment, with increasing digitisation and fourth industrial revolution blurring the traditional value creation boundaries, companies need to explore ways to push the limits to remain competitive. Business model innovation offers companies the dynamic capability to differentiate business models and find innovative revenue streams while reducing costs. As such, the question arises as to how company may use business model innovation to remain competitive as the world digitises. Based on a literature review and empirical research involving six case studies, a three pronged approach in support of business model innovation is proposed. Business model innovation has the potential to push the limits when company executives and academia focus on the interrelation between drivers, process and components. Moreover, both effective and ineffective practices based on the research are presented. In conclusion, for companies to use business model innovation in pushing the limits, there is need to respond to the business model innovation drivers, adopt a systematic process and change at least one or more business model components and taking into account the interactions between these three concepts. This article may contribute to existing theory in the field of business model innovation and lessons learned from executives that have pushed the limits using business model innovation.

Introduction
The fourth industrial revolution and the convergence between the digital and cyber physical world is having a significant impact on value creation and increasing the need for business model innovation. More so, the COVID-19 pandemic has fuelled the growing digitization with most companies having had to shift services online. In this growing digitisation business model innovation has the potential to support companies to recover from and successfully cope with the COVID-19 crisis [1]. Business model innovation is a global concern with the World Economic Forum (WEF) highlighting that fewer than fewer than 10% companies have innovated business models thus have business models that are economically viable as the world digitises. However, the majority of company executives are doubtful of own companies' ability to use business model innovation to harness opportunities from the growing digitization [2]. Furthermore, in a majority of companies the business model is not articulated [3][4][5]. In addition, the process for managing business model innovation to push the limits and remain competitive is not clearly expressed and companies are mostly using generic business models [3]. This emphasis that companies have to explore ways to use business model innovation in pushing the limits to remain competitive within the environment where the financial outperformers put twice as much emphasis on business model innovation as underperformers [6]. Amazon and Apple are good examples of companies that are using business model innovation to push the limits to remain economically viable in a digitised world [2]. There is limited published research on approaches and lessons learned from companies that are successfully using business model innovation to push the limits and remain economically viable in a digitising environment. Moreover, Teece (2010) highlights the need for empirical research on business model innovation [7].
Therefore, the question that arises as to how companies may use business model innovation to push the limits and remain competitive as the world digitises. This article aims to ascertain how company may use business model innovation to remain competitive as the world digitises and provide some practical insights for company's executive on ground level on operationalising business models using a literature review and drawing from six case studies conducted in South Africa.

Business Model Innovation
Business model innovation refers to either adapting an existing business model components or creating a completely new business model with the aim to enable the company push through the limits and compete effectively in a changing environment. Examples of business model innovation include Intel who, according to Pigneur (2006) [8], despite chip design and technology that differs only slightly from that of competitors have excelled at partnerships with PC manufacturers, Microsoft and retailers resulting in an increased competitive advantage. Another example is Gillette, who pioneered customer relationship innovation by giving away razors and making money on the blades in what is also known as 'bait and hook' [8]. Companies, like BMW in South Africa use 'bait and hook' by providing car deals and make money on the financial services offered [9]. Another example is the technology giant Google, who innovated the revenue component of their business model by bringing together searchers and advertisers in a unique way, thus creating an entirely new industry with high growth potential, leveraging on unique assets and building a new market space [6]. Another example from South Africa is Capitec bank that has created an innovative banking business model undercutting traditional procedures and using a simple approach that speeds up service processing as well as providing customers with a simplified service compared to that of competitors [10]. Business model innovation is often driven by a number of internal and external factors. In the next section business model innovation drivers will be examined.

Business Model Innovation Drivers
Business model drivers maybe either external or internal. Sosna et al. (2010) [11] suggest that the drivers are often external. However, Bucherer et al. (2012) [12] put forward the view that the drivers can be internal or external and can also be categorised into threats and opportunities. Meertens et al. (2013) [13] agree that these drivers could be related to threats or opportunities and add that the drivers should have enough expected potential to be worthy of pursuit. The external drivers have been identified as: technological advancement [7,12,[14][15][16][17], market factors [12,14] and regulatory factors [12,14,18,19]. The internal drivers are growth aspirations [20], resources [12], time management challenges, availability of highly skilled experts and joy-in producing high quality products [16]. These business model innovation drivers are illustrated in Figure 1. The business model innovation drivers will lead to a change in the business model components.

Business Model Components
The business model components specify the interrelated set of components which together constituent a business model; Zott et al. (2011) [21] state that each component could constitute a part of a generic business model. There is lack of consensus on what a business model is, and the boundaries for the business model concept has resulted in divergent views on the components of the business model. Andersson et al. (2007) [22] say that a number of ontologies have been developed that state precisely what to include in a business model, while Chandrasekara (2008) [23] highlights that previous research has proposed confusing business model components. In paper, the components are selected from previous studies on business models and business model ontologies.
A business model assists in answering key questions pertaining to the underlying economic logic in a company. According to Osterwalder and Pigneur (2002) a business model identifies what value is offered by the company; to whom the company offers value in terms of one or more customer segments; and how the value is created, taking into account company architecture and partners and relating this to how much profit is made [24]. The business model components are placed in the four main categories ('what', 'how', 'how much' and 'who') of the business model. The 'what' category covers the value proposition and differentiation. 'How' reflects the key activities, key resources and key partners. The 'how much' category represents both the revenue structures and cost structures, while 'who' is the core in the business model covering the target customers, distributional channels as well as the customer relationships that the company maintains with the customers. The business model components are shown in Figure 2.

4I-2M Business Model Innovation Process
Over time business models diffuse and become homogeneous; therefore, to compete effectively, companies need to continuously innovate and sustain the business model [3,17]. However, determining the next cycle of business model innovation is challenging as financial performance may still be ascending while market relevance is decreasing and, hence, the financial performance influences top management against actively seeking new business identification and development. In continuous business model innovation, the model is designed to counter competitor moves while strengthening company capabilities [26]. The process is often iterative; however, a phase-based approach serves as a useful guideline in undertaking a business model innovation [27]. While there is general agreement that innovation is not linear but complex and dynamic, the normative process model helps to reduce complexity and derive the required activities and decision points [12]. Furthermore, Zott and Amit (2015) highlight that while companies jump back and forth through the steps a generalised process model provides a useful guidance for practitioners [30].  [27] state that only a few scholars have focused on a business model innovation process which consists of phases or process steps. Those scholars propose business model innovation phases that are fairly similar or are complementary [12,14,27,28,30]. Frankenberger et al. (2013) developed the 4I-framework from innovation management literature and adapted to business model innovation through an exploratory study in 14 cases [27].
However, Zott and Amit (2015) [30] criticised Frankenberger et al. (2013) [27] as having focused on the challenges in the phases rather than elaborating on the activities undertaken in the phases. In this paper Frankenberger et al. (2013) [27], 4I-framework will be used and supported by the Zott and Amit (2015) [30] design process model and Meertens et al. (2011) [13] to elaborate on the key activities undertaken in each phase of the business model innovation process.
The Frankenberger et al. (2013) [27] framework includes initiation, ideation, integration and implementation will be extended with mobilisation and monitoring phases [12,14,28] to become 4I-2M framework. The mobilisation phase is added because mobilisation in the context of business model innovation is seen as creating awareness of the need for the new business model [28]. Such awareness is an important part of obtaining top management and employee commitment and involvement at the start of the process. Securing explicit top management commitment through the business model innovation process is identified by Elbers (2010) as being essential [31].
Furthermore, early involvement of top management and employees at the mobilisation phase contributes to overcoming internal resistance, which is identified by Frankenberger et al. (2013) [27] as the most common challenge in successful business model innovation. Osterwalder and Pigneur (2010) [28] highlight that continuous monitoring, evaluation and adaptation or transformation of the business model is necessary in response to market changes and hence the monitoring phase is added.
The Business model innovation process complexity is influenced by the scope in terms of the number of components that are innovated. As such business model innovation may be either simple or complex with simple business model innovation involving a change in one of the components of the business model, while complex business model innovation could entail simultaneous changes in the various components of the business model [29]. However, both complex and simple business models are important with Zott et al. (2011) [21] suggesting that it is necessary to innovate the business model even if it may not be game-changing for the industry and Taran et al (2015) [29] indicating the change in the business model components may either be radical or incremental. Based on these theoretical review of the three concepts of business model innovation drivers, components and process empirical data was collected to shed some insights on how these three contribution in the approaches that sample companies are using business model innovation to push the limits and remain competitive as digitising environment.

Research Philosophy and Approach
The study leans towards problem solving in terms of developing an understanding of how companies manage business model innovation to compete effectively in a changing environment as such used a pragmatist philosophy, whose ontological assumption departs from the dualism of subjectivism and objectivism to inter-subjectivity of an informative relationship between inquiry and practice as opposed to a linear relationship where inquiry informs practice [32]. Furthermore, according to Powell (2001) [33] pragmatism's research mandate is not to find truth or reality but rather to facilitate human problem solving. Methodologically pragmatism has no set of methodological requirements but a consequential action knowledge framework to guide inquiry, allowing the researcher to select any method based on the method's appropriateness to the study [32]. As such pragmatism does not require a particular method, or method mix and does not exclude methods [34]. In this paper a mono qualitative research method linked to the abduction theory development approach was used. As according to Saunders (2015) [35] abduction may entail making abductive inference to generate a testable conclusion, with data collection used to explore phenomena and identify themes and patterns. The qualitative approach was supported with case studies and structured interviews to collect data. In addition, theoretical sampling was used to aid transferability. Morse et al. (2002) [36] explain that theoretical thinking requires macro-micro perspectives where ideas emerging from data are reconfirmed in new data, giving rise to new ideas that, in turn, must be verified in data.

Background Information
There is a growing need for the South African ICT and financial services companies to innovate its business model. As Hanna & Knight (2012) [37] point out, the South Africa ICT sector is highly competitive with many players. Whilst in the financial services the banking sector market boundaries are eroding with a fast paced entry of new digital players that are challenging the status quo and driving unprecedented levels of innovation [38]. Thus South African ICT and financial services sectors present a good opportunity for investigating how companies manage business model innovation to compete due to the intense competition in these sectors. Moreover, both sectors have global relevance with leaders such as Microsoft and IBM operating in the ICT and with the some of the companies in financial services sector in the top 100 in global rankings in terms of the quality of organisations and respective business models. It is in this environment that sample case studies were selected and data collected using structured interviews. The sample case studies were selected based on having previously conducted business model innovation. The data was collected using unstructured interviews lasting between 45 and 90 minutes. A brief overview the participant companies and why the companies were selected is briefly outlined in the next section.

Case Study A: Digital Marketing Company
Identified as a viable case for examining business model innovation as the company was branded as one that values innovation and new thinking, according to information published online. In addition, the company is a leading digital marketing company having won several awards and the company perceives itself as a trail blazer in the digital marketing space. Services provided include search engine marketing, digital advertising, big website developments and training. The products include the content management systems, Webcam, mail systems and CRM systems.

Case Study B: Large ICT Company
This large ICT Company was identified as a viable case for examining business model innovation as the company is an ICT services provider that operates in a business-to-business environment and is branded as having a unique business model. Outsourced IT services and products for mission critical systems are provided to some JSE-listed companies as well as to public and private companies including companies in the mining sector.

Case Study C: Small ICT Company
A consulting services, e-learning and software systems provider to large enterprises in South Africa. Uses the business model canvas to help customers to document business models and identify broad-based economic empowerment (BBEE) opportunities. The company utilise business model concepts to help customers to understand the impact of BBEE on their business model. Hence, the company presents an opportunity for the researcher to examine how the company innovates the business model to compete effectively, as well as how the company supports customers to manage business model innovation to achieve BB-BBEE compliance.

Case Study D: Financial Services Provider A
Financial services provider A presents a curious case as it is a subsidiary of a global group and is perceived to be unique, focusing on their customers' service requirements. This financial services provider seeks to address customer frustrations while saving them money. It offers banking and insurance services.

Case Study E: Financial Services Provider B
Financial services provider B presents opportunities to examine business model innovation in a company that operates in a niche market. It is newly established and is a renewable energy funding provider with an innovative product that was not being served by the commercial banks as the market is regarded as too small for commercial banks yet too big to be funded from developer's balance sheets.

Case Study F: Financial Services Provider C
This is a company in a financial services sector where there is a high degree of concentration and interconnectedness with the top five banks. Financial services provider C is one of the leaders in the market, providing both financial services and insurance services. In addition, the company is perceived to be a first mover and disrupter in its market, a view supported by some of the executives in the competitor companies that participated in the study.

Case Study Results
In comparing the case study results, the business models from the sample companies are perceived to be differentiated from those of competitors to varying degrees. The case companies in ICT services differentiation appears to focus on provision of customised products and services, while financial services providers focus on the uniqueness of products and services. Thus suggesting that in the case of the ICT companies the differentiation is a bit reactive directly customer led while financial services are a slightly proactive predicting customer needs but this is based on their own insight. This may be attributed to the fact that while the companies in the ICT sector provide products that are supported by services and mostly focus on the business-to-business services, those in the financial sector provided a greater variety of services ranging from different banking products and insurances services in a business-to-consumer environment.
The business model challenges faced by the ICT companies include scalability of services, the low barriers to entry and the resulting intensifying competition with some case partners becoming competitors. The 'China price' was found to be eroding margins from the product business models while Indian companies are eroding the margins on the services business models. In the financial services case studies, the business model challenges include the global financial meltdown which resulted in some of the case studies needing to strengthen regulatory compliance requirements, especially for companies that are owned by foreign companies. Competitive pressure is also said to be increasing with new players, such as retailers, entering the market and the growth of direct online marketing channels in the case of insurance companies. Furthermore, challenges regarding continued survival leading to business model innovation and changes in the global markets were discussed but only in some financial services case studies. The abstraction levels of the business model range from a very detailed product level, the business level and the company level to the much aggregated industry level [39]. In this research the business model level discussions indicated that in both sectors there is a focus on product level, company level as well as in the industry specific business model level.
The business model innovation drivers were continuously monitored in the case studies. The perceptions that the intensity of the external drivers' act as drivers for business model innovation were found to vary amongst the case studies. However, internal factors were perceived to be intense drivers in all the sample companies. These internal factors include entrepreneurial or inspirational leadership, staff quality and in some cases growth aspirations.
An understanding of the business model components was regard to be of value in the sample companies with two of the six case studies using Osterwalder and Pigneur (2010) [28] business model canvas to support visualisation of the business model. One company used the stickman house analogy to visualise the business model. In the house analogy the components in terms products and services are depicted in the foundation, and how such products and services are differentiated in the roof as well as how the products and services are created as illustrated in the house block in terms of the operations, processes, structure and culture. The visualisation also depicts the 'who' of the business model in terms of the target customers, the relationships that are maintained and the distribution channels. A suggestion from one of the case studies was to extend the product and services visualisation with "who: could content the value proposition as this would provide a proactive approach to risk in the company products being context as the case of Uber and the local meter taxi example. The detailed case studies results are depicted in the Table 1.

Lessons Learned Managing Business Model Innovation
A number of effective and ineffective practices in managing business model innovation may be presented as lessons learnt from the case study. One such lesson is using a continuous approach to business model innovation that advocates a tipping point approach to retire the old business model as reflected in this quote.

"A continuous business model innovation process with the old and new business models running concurrently until a tipping point is reached. That is a point where the new business model is generating more money than the old one and at this point you retire the old business model and switch offer to the new business model as such closing off the old business model. And you don't switch overnight and say this is our new model because you are going to destroy value."
The use of subsidiary companies to pilot test business model innovation projects as an effective practice for managing business model innovation. In such an instance, the business model innovation project would be implemented by the subsidiary company on a "trial and error" basis, with the project eventually being brought into the company.
"We put outside with our subsidiaries small innovative experiments that we will eventually bring in." Furthermore, the use of subsidiary companies was regarded as an effective practice for providing services to the previously unserved customers. For example, Large ICT Company is a provider of ICT services in the business-tobusiness consumer market, thus in targeting an unserved market a subsidiary with a business model that is different from that of the parent company is used.

"For the unserved customers we have a company called XYZ as we largely support big clients. If we want to support the masses, we need a different business model. That business model, which I have told them clearly is based on automation and self-service, otherwise you need thousands of resources to support that market which is not a sustainable model. So our focus new market is on self-service and automation."
The identification of the type of relationship the company has with the target customer segment was one key issue for managing business model innovation as business models for one-to-one and those that are aimed at one-to-many relationships are different. As the pricing and business models around one-to-many and one-to-one relationships are completely different. This view was expressed as follows: "I think it is also important for me that business models are applicable to each segment that you are working. We tend to segment our market in two: mid-market enterprise customers and the small-mediummicro customers. Down there we find that the relationship is one-to-many whereas in mid-market and up the relationship tends to be one-to-one. Then your pricing and business models around one-to-many and one-toone are completely different".

Table 1. Case study results
The effective management of business model innovation to compete entails a continuous business model innovation approach in which the company business model is evolved on an ongoing basis. This was illustrated as follows by one of the participants: "The core business model for our company is to make money using technologies as … I think that is the view that the business model is bringing in -that you might be making shoes today but you are not in the shoe making business but what you are trying to do is to solve a customer problem. As such I see the core business of Large ICT Company as making money using technologies." An additional effective practice in managing business model innovation entails using business model innovation as a theme to bridge the gaps between the various organisational units as illustrated as follows: "We have been a bit unfortunate in that with all this accountability and measurement that have been in our company for so many years, people have built some islands they have been so proud of. What they not necessarily want to share or work with other people and that is true for many other organisations.
We have now build bridges between all those silos where there is joint benefit for the guys to work together and this is the whole theme of our business model innovation project bring people together … First time it seems like our data centre infrastructure people joined forces with the application people. So we were able to write an application run it on our data centre that uses our communication network team to be able to deliver video over mobile. We see a converged solution pulling all the necessary different silos together at one offering, as such building bridges between those silos where there is joint benefit for the guys to work together." Risk management is an effective practice in managing business model innovation to compete effectively as failure to manage risk in business model innovation in business model innovation could have a "domino" effect as shown by this extract:

"In a business model innovation project anywhere you have a got a weak link -it will have a domino effect all across. So if it is hasn't got a domino effect it is not fully integrated business model. So it is one of those things that you need to get right"
Pricing influences business model innovation; the lessons regarding the effective management of business model innovation is the use of customised pricing as shown in this extract: "Pricing is not always the same ... as we tend to work on demand type basis and the minute you are selling customized offerings … so it is very difficult to compare this offering to another because each offering is customized for that enterprise … However, the company uses sophisticated pricing and guidelines for deviations from the set price. We using different models as to what we are selling to whom. It is not always the same and one of the pricing is based on what is being specified by the customer and we do have guidelines for the deviations from the set price"

Discussion
The main conclusion from the research study, supported by both the theory and empirical findings, is that managing business model innovation to compete effectively is a complex activity with three interrelated concepts. The research study examines the three interrelated concepts of drivers, process and components related to approaches to business model innovation. These conceptual framework is illustrated in Figure 3 below.
Firstly, managing business model innovation entails having a clear understanding of the factors that drive this innovation as these have the potential to make the existing business model irrelevant in the market. Thus, companies need to monitor business model innovation drivers that are continuously changing. These drivers in the current study deviate from Sosna et al.'s (2010) [11] suggestion that drivers are mostly external but rather supports Bucherer et al. (2012) [12] views that drivers may be internal opportunities or threats as well as external opportunities or threats.
However, an additional insight generated from the empirical data is that interrelationships between the drivers result in additional complexity. Thus, companies often have to respond to complex, interrelated drivers so as to adapt or totally redesign the existing business model and the underlying business model components.
Secondly, as a response to the drivers, companies need to adopt a continuous business model innovation process that is either organic or structured. Those companies that adopt an organic process perceive that a structured business model innovation process could stifle creativity while those that choose a structured process view such structure as a guide to ensuring the business model innovation process steps are complete as each step is supposed to be part of an effective management of the business model innovation. The size and proximity of the business model design team could be a factor that has a bearing on the adoption of either of the approaches. In the case where the team is small an organic approach was adopted as reflected in the following extract: "It is not many of us. Board meeting happens very quickly like let's say we need to spend the whole day somewhere or whatever like now in Durban we are going to work on our business." "The nice thing of having a small kind of operation... the fund that I manage is run by myself and a colleague in Cape Town, so it's nimble and we're able to actually to modify our strategy and process by the day if necessary and I then meet once a week with my colleagues. Three of them are the senior guys within this business, and once a week we have a feedback session on how the business is performing, the existing assets and then on ad hoc basis we discuss where we need to go and what needs to be done."

Figure 3. Conceptual framework three pronged approach business model innovation
In both a structured and an organic approach a continuous business model innovation process is adopted as Chesbrough (2007b) and Mahadevan (2004) [3,17] have recommended as over time business models diffuse and become homogeneous, resulting in a renewed need for business model innovation to enable companies to differentiate their offerings. As such managing business model innovation to compete will be hampered if there is a lack of a defined process for business model innovation. Thus the 4I-2M business model innovation process adapted from Frankenberger et al. (2013) [27] and Zott and Amit (2015) [30] as well as Meertens et al. (2011) [13] supported with contributions from [12,14,28] was found to potentially be a relevant framework. The main steps in such a process are mobilisation, initiation, ideation, integration, implementation and monitoring.
Thirdly, the business model components are redesigned in response to the business model innovation drivers. Such a redesign, as highlighted in Taran et al (2015) [29], could either be simple business model innovation in terms of only one component of the business model being redesigned, or complex where two or more components are simultaneously innovated. In the sample case studies both simple and complex approaches were adopted with simple approaches focusing on innovating value propositions while complex approaches include redesigning value propositions in tandem with delivery channels of revenue sources where a revenue share strategy with customers was adopted.
Therefore, based on these arguments, the research study proposes a conceptual framework for managing business model innovation to compete in a changing environment. This framework has three major parts. Firstly, the business model innovation drivers illustrated previously in Figure 1. Secondly, the business model innovation process 4I-2M synthesised from Frankenberger et al. (2013) [27] 4I-framework. This 4I-2Mframework has been supported by the Zott and Amit (2015) [30] design process model to elaborate on the key activities undertaken in each step and adapted with contributions from Osterwalder and Pigneur (2010); and Bucherer et al. (2012) [12,14,28]. Thirdly, the business model components illustrated in Figure 2 whose conceptualisation is informed by the work of Osterwalder and Pigneur (2010) [28] supported by scholars such as Johnson et al. (2008), Stähler (2002) and Chesbrough and Rosenbloom (2002) [4,28,40,41]. Moreover, the conceptual framework has been reviewed for relevance as part of the research being reported on here that is, in the sample case studies in the ICT and financial services sectors in South Africa.
Having done this creates a foundation based on which additional elements can be identified that are core to a comprehensive understanding of how companies manage business model innovation.

Conclusion
In conclusion, the study uses theory and empirical data to generate insights into three interrelated concepts, namely, the business model innovation drivers, process and business model components. In managing business model innovation to compete companies will be hampered if there is a lack of a defined process for business model innovation; thus, the study provides a theoretical basis for further exploration regarding how these elements contribute to managing business model innovation in order to compete effectively in a continuously changing environment. Furthermore, the theoretical contribution relating to the business model components extends to both the communication of the business model and the companies' approaches to business model innovation. Hence, the paper, by examining the three interrelated concepts (drivers, process and components) with the communication of the business model and approaches to business model innovation, presents a foundation for the identification of additional elements that are core to a comprehensive understanding of how companies manage business model innovation to compete. In addition, it provides effective approaches in managing business model innovation. These lessons include using a continuous approach to business model innovation that advocates for a tipping point approach to retire the old business model. Such an approach would require running the old business model and the new business models concurrently until a tipping point is reached. That is a point where the new business model is generating more money than the old one and at this point you retire the old business model and switch over to the new business model by closing off. As well as a risk management is practice as failure to manage risk in business model innovation in business model innovation could have a "domino" effect.

Data Availability Statement
The data presented in this study are available on request from the corresponding author.

Funding
The research work was supported by National Research Innovation Fund (ZA); Banking Sector Education and Training Authority ((BANKSETA) (ZA); University of the Witwatersrand, Johannesburg.

Declaration of Competing Interest
The author declares that there is no conflict of interests regarding the publication of this manuscript. In addition, the ethical issues, including plagiarism, informed consent, misconduct, data fabrication and/or falsification, double publication and/or submission, and redundancies have been completely observed by the author.