The Effects of Environmental Legislation via Green Procurement Strategies: A Systematic Literature Review

Abstract

Background: EU environmental legislations affecting global supply chains have come into force since 2022. As procurement plays a direct role effectuating this, the result of these legislations via procurement becomes relevant. Methods: A systematic literature review is used to synthesize 152 articles from managerial, business administrative, and supply chain journals. The Context–Intervention–Mechanism–Output framework (CIMO) is used as the lens by which the articles are analyzed. The articles present findings from diverse methodologies and combine green business-to-business procurement with at least one element from the CIMO framework. Results: Five conceptual frameworks of different green procurement strategies are developed, each explaining the strategy and its expected result. The strategies increasingly collaborate and by this increasingly reduce environmental impact. A comparison of the strategies identified variables which strengthen the working of environmental legislation as they contribute to collaboration. Conclusions: Customer demand is crucial for collaborative green procurement. Without this, environmental legislation will only achieve limited environmental objectives. Propositions are formulated on variables which, next to the business case, strengthen the working of environmental legislation. This article adds to the science by synthesizing the existing knowledge base into propositions and future research directions. The findings may also support policymakers in understanding the effectiveness of legislation.

1. Introduction

Many governments pass laws to protect the environment, whereby especially Western legislation impacts entire global supply chains [1] to address firms’ environmental performances. For example, the European Union’s (EU) Carbon Border Adjustment Mechanism, Deforestation-free Regulation, and the Corporate Sustainability Reporting Directive have all come into force since 2022 and the first two aim to impact the environment globally via EU imports. However, overseas suppliers, often operating under less stringent legislation, focus primarily on prosperity [2] and operate under extreme cost pressure [3,4]. Despite legislation being a powerful instrument to change firms’ behaviour [5,6,7], the traditional confinement within national jurisdictions [2] limits the global impact [8].

This global impact is the result of the entire supply chain. After all “companies are only as sustainable as the suppliers that compose their supply chains” [9], whereby lower-tier suppliers cause the highest impact [3]. Next to this, global transport, enabling this supply, contributes between 20% and 31% of global greenhouse gas emission [10,11].

If the supply of goods is a substantial contributor to firms’ total environmental impact, procurement directly influences this upstream impact. Green procurement is a reaction to the increasing concern for the environment. It relates to sustainable procurement, which “meets the needs of the present without compromising the ability of future generations to meet their own needs” [7,12] and includes environmental, social, and economic decision criteria [13,14]. Green procurement selects suppliers by using environmental and economic decision criteria [15] and aims to minimize environmental impact [16]. Green procurement is associated with collaboration with suppliers [15,17,18,19,20,21,22,23], with NGOs, and even with competitors [24]. Green procurement is also described in development phases, with increasingly collaboration in the successive phases [25,26]. Tate [16] defined these phases as General Practises (GeP), Supplier Selection (SuS), Supplier Involvement (SuI), Supplier Development (SuD) and Supplier Performance (SuP). Higher phases better achieve reduced environmental impact [16,27,28].

Although business-to-business (B2B) green procurement is the topic of many scholars, the influence of legislation on B2B procurement decisions seems under-researched [29] and the effect of this legislation on the environment caused by procurement [30] remains unclear. Given the new supply chain impacting legislations in force, understanding how legislation does achieve an impact via B2B procurement becomes relevant. Since collaboration appears important to reduce environmental impact, the contribution of legislation on the decision to collaborate seems important. This study explores the existing scientific knowledge base on the interplay of environmental legislations and other variables which contribute to collaborative B2B green procurement strategies through a systematic literature review.

Five conceptual frameworks following the Context–Intervention–Mechanism–Outcome (CIMO) framework [31,32] are developed. Each represents a green procurement strategy, defined as the mechanism. They explain in which context environmental legislation triggers this strategy, and which environmental impact is expected. Literature is used to select variables which co-determine with legislation this procurement strategy. By comparing the five conceptual frameworks, propositions are developed on the interplay of environmental legislations and these variables on green procurement strategies. Legislation alone appears to be not enough for collaborative green procurement strategies. Customer demand for environmentally friendly products, and through this a business case, is vital for collaboration. Without this, environmental legislation will only achieve limited reductions in environmental impact from green procurement.

The contribution to the scientific body of knowledge is twofold. Firstly, the synthesis of existing knowledge on the effect of environmental legislation on green procurement deepens theory on green procurement. After empirically testing the developed theoretical propositions, new theory will be built. Secondly, the CIMO framework [31,32] proofs a valid instrument to explain complex constructs in a social domain as well. The contribution for policymakers and managers is understanding how environmental legislation effectively achieves the intended outcome via procurement.

The remainder of this article firstly provides the methodological justification, followed by the results, discussion, and conclusion.

2. Materials and Methods

A systematic literature review is performed to analyze and synthesize the extensive body of knowledge [33] on green procurement. This review refines theory [34] by exploring the effect of legislation on the different phases of green procurement to understand when firms come to apply collaborative green procurement. This review follows Durach and Kembro’s [35] six steps and Sauer and Seuring’s [36] 14 decisions. These steps and decisions (D) are added below. The Prisma 2020 checklists are used for reliability reasons [37].

2.1. Step 1: Define Research Question by Decisions 1, 2, and 3

To understand when firms decide to apply collaborative green procurement, the review must define the effect of legislation and identify the role of other variables on green procurement (D1).

The review has an inductive approach (D2) to refine green procurement’s theory as it aims to translate the findings from the literature to knowledge on the effect of legislation, the decisive roles of other variables, and green procurement.

The CIMO framework [32] clarifies how an Intervention (I) triggers a Mechanism (M) in a Context (C) to achieve Outcomes (O) and explains under which conditions the theory works [31]. This framework provides the fundament for the theoretical framework of green procurement used in this study (D3). It explains in which context environmental legislation (intervention) triggers a green procurement strategy (mechanism) to achieve the intended result of reduced environmental impact, and possible unintended results. Both are the outcomes. However, procurement activities involve many human decisions and can be considered a weak mechanism [32]. To better understand this weak mechanism, moderating and mediating variables are added, which results in the conceptual CIMO-based framework of green procurement presented in Figure 1.

Combining these three decisions, the research question (RQ) is formulated as follows: “How does environmental legislation effect the environment via green procurement according to the existing body of knowledge?”

2.2. Step 2: Determining the Required Characteristics of Primary Studies by Decision 4

In order to explore legislation’s role in business-to-business green procurement, journals are selected within the managerial, business administrative, and supply chain domain. The conceptual CIMO-based framework (Figure 1) shows the lens by which green B2B procurement is approached. Included articles must explain at least one element from Figure 1 with a green B2B procurement strategy, which is the unit of analysis. This enables us to analyze this procurement strategy and identify when legislation achieves the intended outcome. Other inclusion criteria are peer-reviewed studies, published in English, from 2012, with open access (D4).

2.3. Step 3: Retrieving a Sample of Potentially Relevant Literature by Decisions 5 and 6

The EBSCO databases were used to retrieve the articles. To capture all valuable findings and avoid publication bias, no restrictions were set on journals within the chosen domain (D5). The search string (D6) combines the thesaurus term “sustainable procurement” with subjects and keywords by the Boolean “OR” (

Table 1. Search string.

Thesaurus	Sustainable Procurement
OR
Subject OR keyword	sustainable procurement OR sustainable purchasing OR sustainable sourcing OR sustainable buying OR sustainable supply management OR green procurement OR green purchasing OR green sourcing OR green buying OR green supply management OR environmental procurement OR environmental purchasing OR environmental sourcing OR environmental buying OR environmental supply management
OR
Subject OR keyword	sustainability AND (procurement OR purchasing OR sourcing OR buying OR supply management)

). EBSCO only defines sustainable procurement as a thesaurus term, which includes green procurement. Green procurement with synonyms for procurement and green are used as subjects and keywords. This open approach enables to find the various variables, as presented in Figure 1, and avoids retrieval bias. However, this search may reveal for this study less relevant studies as well.

2.4. Step 4: Selecting the Pertinent Literature by Decision 7

The search was conducted in 2024, updated in January 2025, and resulted in 1306 hits. Next, 559 records were automatically removed, which left 768 records to be screened by reading the titles and abstracts. The inclusion-and-exclusion process is shown in Figure 2, which the first author applied independently with feedback by the co-authors. To avoid selector bias, no restrictions were made in the methods, concepts, and journals in which data were collected. The reference lists of the included articles were checked. A total of 21 articles that were not found in the original search were added to the search results (snowballing, as indicated in Figure 2) to reduce inclusion criteria bias. The final set included 152 articles.

2.5. Step 5 and 6: Synthesizing the Literature by Decisions 8, 9, 10, and 11 and Reporting the Results by Decisions 12 and 13

ATLAS.ti 24 is used for coding (D8), whereby all codes are derived from the conceptual framework (Figure 1) (D9). The coding scheme is developed as follows.

Context is specified into industry sector and geographical region [24]. The sector is consolidated into manufacturing and non-manufacturing firms [13,38,39]. The regions into continents and specified into developed and non-developed countries [40,41].

Words like law, legislation, regulation, and rules are coded as interventions.

The procurement strategies are coded as mechanisms and allocated to one of Tate’s [16] five procurement strategies, with increasing collaboration (

Table 2. Five green procurement strategies, adapted from Tate [16].

Green Procurement Strategy	Description from Tate	Interpretation
General Practices (GeP)	Practices that suggest concern for environmental issues but lack specificity as to what actions are actually being taken	No intention or ability to procure green products. No green supplier selection criteria. Green criteria are nice to have.
Supplier Selection (SuS)	Modifying supplier selection criteria in order to incorporate environmental criteria	Adding green criteria to the supplier selection process.
Supplier Involvement (SuI)	Captures practices in which a supplier is mentioned as being involved in helping the buying firm improve its own environmental practices	See supplier selection strategy; Involvement supplier to improve firm’s performance.
Supplier Development (SuD)	Captures practices in which the buyer provides support to the supplier in order the help the supplier improve its environmental performance	See supplier selection strategy; Development supplier to improve its performance; Exchange knowledge, data, information and offering training from firm to supplier.
Supplier Performance (SuP)	The buying firm’s performance on key sustainability metrics is linked directly to supplier sustainability outcomes	See supplier involvement and supplier development strategies; Mutual benefit by jointly improving performance of both firm and supplier.

) and by this increasingly reduced environmental impact. Since 2012, Tate has been cited 233 times and, analyzing the abstracts of these 233 studies, the five strategies have never been challenged. Instead, there is consensus on the importance of collaboration [42,43] to drive innovation [44,45].

The wording used in the included articles are compared with the wording used by Tate and with this studies’ interpretation of Tate (right column Table 2) to allocate the articles. To avoid bias, the allocation by the description of several strategies were discussed with peers.

The moderating and mediating variables are not known beforehand, and the coding scheme is interpretatively developed. Drivers and barriers of green procurement, as described in the articles, are coded as these variables. These variables are clustered in several iterations by combining variables that, although described differently, mean the same. Finally three mediating and twelve moderating variables remain. The explanation column in

Table 3. Mediating and moderating variables.

Mediating Variable	Explanation	References
Green embedded in firm	The procurement department and its strategy are part of an organization and usually follow the corporate strategy. If the firm already defined environmental targets for the entire firm, procurement likely follows.	[22,26,46,47,48,49,50,51,52,53,54,55]
Awareness	Awareness of green procurement’s importance may change behaviour and implement green procurement.	[29,56,57,58,59,60]
Availability green products	The presence of environmentally friendly products to procure influences green procurement’s possibilities.	[17,48,61]
Moderating variable
External pressure	External pressure drives firms to a certain strategy. However, these pressures are ambiguous due to variating interests and legitimate behaviours. Visible firms are highly influenced by consumers. These firms are close to end-consumers and large, limited liability companies acting globally.	[16,62,63,64,65,66,67,68,69,70]
Complexity	Green procurement is more complex than conventional procurement. The versatility of “environmentally friendly” complicates defining it and calculating the trade-off between economic and environmental performances. Next, life-cycle accounting, registering environmental impact over a product’s life-spam, is needed. Current long and dynamic supply chains with many unknown lower-tier suppliers complicates this accounting. Lastly, supplier’s environmental performance needs to be monitored continuously.	[1,14,19,20,25,61,65,71,72,73,74,75,76,77,78,79,80]
Weight supplier selection criteria	Firms often use several supplier selection criteria. Environmental supplier selection criteria being valued as equally important as economic ones sti-mulates green procurement.	[8,41,81,82,83]
Expected performance	If the environmentally friendly products are expected to perform worse on valued supplier selection criteria or if the firm’s performance is expected to worsen due to green procurement, then the procurer is less likely to procure environmentally friendly products. Green procurement is expected to increase operational costs, like procurement costs, administrative costs, and monitoring costs. It is also expected to improve reputation and by this may bring competitive advantage.	[13,24,75,84,85,86,87,88,89,90,91,92]
Organizational resources	Implementing green procurement requires investments. Enough demand for environmentally friendly products justifies these investments, but firms need enough initial financial resources. Other resources such as knowledge and innovative and collaborative skills are needed for green procurement.	[13,50,72,76,82,83,92,93,94,95,96,97,98,99,100]
Inter-firm relationship	The inter-firm relations within a supply chain must enable collaboration and by this collaborative green procurement.	[6,29,48,70,88,98,100,101,102,103]
Supply chain risks	Supply chain risks of environmentally friendly products influence the decision for green procurement.	[1,12,19,104,105,106,107,108,109,110]
Top management support	Firm’s activities, including green procurement, take place in line with (top) management’s support.	[95,111]
Organizational culture	Organizational culture influences organizational decisions. Culture which supports green procurement is characterized by concern for the environment, open for innovation, proactive attitude, flexibility, employee autonomy, trust, knowledge sharing, teamwork, concern for individual values, and creating a win-win situation. Suppliers having the same values facilitate close collaboration. Slow adaptors of innovative concepts, or firms characterized by obedience and a non-collaborative attitude, have little support green procurement.	[7,15,18,22,23,24,25,26,27,48,58,60,61,77,82,86,87,98,105,106,112,113,114,115,116,117,118,119,120,121]
Individual procurer	Middle management’s and individual procurers’ motivation, knowledge, capacity, and attitude towards the environment influence daily operation and by this the effectiveness of green procurement.	[40,41,52,98,120,122,123,124,125,126,127]
Enforcement	Enforcement of environmental legislation affects green procurement.	[2,7,21,24,128]
Company size	Large firms’ organizational resources enable green procurement.	[54,129]

summarizes the creation of these codes.

To capture both the intended and unintended results of environmental legislation, the outcome is coded in line with Melnyk’s [130] six supply chain outcomes. Melnyk defined environmental impact as “sustainability”, which “minimizes resource impact, both today and in the future”. The other outcome codes are costs (product and delivery costs), responsiveness (ability to respond to changes in the market), security (protection from external risks), resilience (recover quickly from disruptions), and innovation (new products/services that bring competitive advantage).

Five tables, one for each green procurement strategy, are created, which list all articles with their coding (Appendix A, Appendix B, Appendix C, Appendix D and Appendix E). These tables are used for frequency and content analysis (D10). Frequency analysis indicates the relevance of a variable given the amount of mentions [131]. Content analysis explains green procurement with at least one variable from Figure 1 [132]. Structural meetings with co-authors avoided expectancy bias.

The results of these analyses are presented in the next section (D12 and 13).

3. Results

3.1. Descriptive Analyses

The included articles originate from 77 different journals. The division of the domains is presented in Figure 3, the division of the publishing years in Figure 4, overviews of the used methods in Figure 5, and the overview of used theories in Figure 6.

3.2. Frequency Analysis

Each included article combined green procurement strategy with different variables from the conceptual framework (Figure 1). Some variables are more mentioned than others (

Table 4. Counting of codes.

Variable from Framework		Total	GeP	SuS	SuI	SuD	SuP
		N = 152	N = 14	N = 105	N = 7	N = 20	N = 31
Context
Sector	Manufacturing	62	5	39	4	7	19
	Both manufacturing and non-manufacturing	27	1	20	0	2	4
	Non-manufacturing	16	6	10	1	3	2
	Unknown sector	47	2	36	2	8	6
Region	Asia	41	1	27	2	2	8
	Europe	39	8	25	2	7	11
	America’s	21	1	13	1	2	4
	Other	23	2	15	1	3	5
	Unknown region	34	2	28	1	8	4
Developed status	Developed country	56	7	36	5	7	16
	Non-developed country	50	4	36	1	2	8
	Unknown status	46	3	33	1	11	7
Intervention
	Environmental legislation in force	79	5	58	3	10	16
	Environmental legislation not in force	11	5	6	0	0	0
Mediating variable
	Green embedded in firm	64	6	40	3	7	16
	Awareness	46	4	33	1	5	4
	Availability green products	29	6	22	0	4	4
Moderating variable
	External pressure	94	10	66	5	16	16
	Complexity	83	6	60	6	15	14
	Weight decision criteria	77	9	54	2	7	11
	Expected performance	75	7	49	3	13	10
	Organizational resources	62	4	39	6	10	12
	Inter-firm relationship	57	4	40	2	8	16
	Supply chain risks	41	1	28	2	7	6
	Top management support	41	2	27	2	5	8
	Organizational culture	41	1	23	1	7	11
	Individual procurer	37	5	30	0	2	4
	Enforcement	34	5	22	0	5	5
	Company size	30	2	19	2	4	5
Outcome
	Sustainability	75	3	41	4	10	23
	Cost	64	1	41	4	7	19
	Innovation	44	1	17	2	10	19

). Three of Melnyk’s [130] defined outcomes were mentioned by 12 or fewer articles and left out of further analysis.

3.3. Content Analysis

The five strategies are explained in more detail below, using a maximum of two sources per statement for readability purposes. The identified variables from Table 4 are combined with the green procurement strategy in an explanatory and narrative way, emphasizing variables which are frequently mentioned in the articles. When describing “firm”, the buying firm which implemented a green procurement strategy is meant.

3.3.1. General Practices (GeP)

GeP is applied when environmental criteria are not decisive due to lacking environmental legislation.

GeP was described in 14 articles (Appendix A) in a both manufacturing and non-manufacturing, European contexts, whereby 9 articles mentioned that environmental legislation was not in force or did not mention environmental legislation at all (Table 4).

External pressure on the firm to procure environmentally friendly products was limited [73,133]. Firms valued conventional supplier selection criteria and expected green procurement to perform worse on these criteria [63,125]. There were no certificates stating the environmental performance of the bought products, which complicated green procurement [16,61]. The market was characterized by high competition [63], small profit margins [81], powerful suppliers [25,73], and little loyalty between firms and suppliers [23]. This contributed to the non-presence of environmentally friendly products to procure [17,61].

Internal environmental targets were either not defined [23,133], not aligned between departments [81], not translated into environmental supplier selection criteria [28,134], or not enforced [23,61]. Firms lacked awareness on the importance of environmental preservation [134,135], knowledge [23,73], and collaborative capabilities [24] and were slow adaptors to new concepts [61,125]. SMEs especially [28,81] did not invest in green procurement [17,135]. Top management and staff were critical about environmentally friendly products [133,135], but, as environmental targets were not integrated into daily operation, the individual procurer’s motivation and capacity were crucial to applying green procurement [61,73].

GeP did not reduce environmental impact [63,73], and even exacerbated it [61]. No costs benefits or innovation were expected [23].

A conceptual framework of the mechanism of GeP is shown in Figure 7, which summarizes the findings above. It follows the structure of the CIMO-based framework from Figure 1. The numbers in brackets are derived from Table 4.

3.3.2. Supplier Selection (SuS)

SuS is applied due to legal obligations, but without intrinsic motivation.

SuS was described in 105 articles (Appendix B), with 59 articles described a manufacturing context (Table 4). SuS was applied by globally dispersed firms [66], triggered by environmental legislation [88,115].

The external pressure on a firm to procure environmentally friendly products was moderate. Customers [29,77], management, and staff [117,136] were unaware of the environmental impact and were not willing to pay extra for environmentally friendly products [52,137]. Green procurement was not acknowledged as a competitive advantage [90,138] and considered too complicated given the lack of certificates stating the environmental performance of products and little internal environmental knowledge [57,139]. Firms had little influence within the supply chain [68] and were primarily aiming to reduce costs [89,140] and increase profit [141]. This resulted in operational excellence [21,142] to secure reliable rather than environmentally friendly supply [79,120].

However, environmental legislation priced-in impacting the environment [6,143], making environmentally friendly product’s supply chain risks important [12,144]. Risk management [56,71], stakeholder management [3,39], and the trade-off between environment and costs [145] supported the decision of which environmental supplier selection criteria to apply [92,102]. However, the firm’s corporate strategy [59,119], its structures [41,51], and incentive system [50,86] remained the same. As a result, environmental supplier selection criteria clashed with economic ones [54,94]. Procurement managers’ [87] and procurers’ [1,124] motivation and ability to mitigate this complexity appeared essential.

Firms aimed for compliance [23,145] and a good reputation [101,107] against minimum costs. This led to the non-monitoring of suppliers’ performance [4,22], continuation of contractual relations after supplier’s non-compliance [3,20], simplifying green targets [1], selecting suppliers who operate under stringent environmental legislation [109] or with the same legitimate behaviour [65,139], using uniform environmental supplier selection criteria which limited indications of the true environmental impact [66,85], or not paying extra for environmentally friendly products [65]. This forced suppliers to non-compliancy [4] and green washing [68,127], given their extreme cost pressure [3,4] and unwillingness to bear investments alone [78,97]. Competitors’ green washing [72] and little enforcement of environmental law [7,113] contributed to these practises.

Given the above, SuS hardly reduced environmental impact [114,146], whereas it remained unclear if SuS increased profit [73,147]. Operational costs, such as transaction costs [85,148] and monitoring costs [21], and thus selling price [29,94], increased. Conversely competitiveness improved [27,149] as supply chain risks reduced [63,83] and the firm’s reputation improved [38,46], which gave access to external funding [62,82] as demand for environmentally friendly products was expected to grow [93,150].

The conceptual framework of the mechanism SuS is shown in Figure 8.

3.3.3. Supplier Involvement (SuI)

SuI is applied when the firm needs the supplier’s knowledge to meet legal and customer demands.

SuI was described in seven articles (Appendix C), of which four described a manufacturing context and five a developed country (Table 4). SuI was triggered by environmental legislation [16,27].

The firm’s awareness on environmental issues was limited [110], while consumer demand changed rapidly in asking for environmentally friendly products [16]. The supplier’s knowledge supported the firm in overcoming these novelties related to the environment [110]. The increased consumer demand justified the related investments [27], which were more easily performed by larger firms [27,151]. As the suppliers were carefully selected, SuI decreased the risks of supplier’s malfunctioning [110] or uncertain supply [151].

Firms approached procurement strategically [27], implemented internal environmental targets [152] which were equally important as economic ones [110], had access to knowledge on environmental issues [18,27], could innovate [110], and supported long term collaboration with suppliers [18,152]. Management supported the new procurement strategy [151] and procurers were free to bypass internal procedures to implement the new green procurement strategy [27].

SuI reduced environmental impact [152,153] and improved competitive advantage [18,27]. The findings on the cost effects were undetermined [151,153].

The SuI conceptual framework is visualized in Figure 9.

3.3.4. Supplier Development (SuD)

SuD is applied when the law and market demand environmentally friendly products, but suppliers cannot deliver environmentally friendly products.

SuD was described in 20 articles (Appendix D), mostly in a European and manufacturing context (Table 4). SuD was triggered by legislation [15,108], but two other variables seemed crucial. Firstly, customers’ demand for environmentally friendly products changed rapidly [17,24] and increased [47,84], which resulted in the second important variable: a business opportunity for the firm to satisfy this demand [101,154]. However, suppliers operating under less stringent legislation [30,80] were unable to deliver environmentally friendly products [155,156] and the firms were held responsible for the suppliers’ inability [19,80]. This motivated firms to analyze the (partly unknown) supply chain [15,155] to decide which suppliers to invest in long term [80,156], even with uncertain results and Returns on Investment (ROIs) [47,155]. Especially large firms were able to make these investments [47,108].

The collaboration with suppliers was characterized by jointly defining green targets [15,30], by sharing knowledge [24], by agreements on volumes and prices [17,18], by jointly developing lower-tier suppliers [19,60], and lastly by providing suppliers improvement time [20].

Firms implemented internal environmental targets [20,154] and fostered proactive attitudes [24,26], internal collaboration [15,60], innovation [20], and knowledgeable staff [20,84].

Successful SuD contributed to product innovation [122,156] and reduced environmental impact [16,84] due to (lower-tier) suppliers’ business guarantees [47,108], and by this a reliable supply of environmentally friendly products [18,60].

The SuD conceptual framework is presented in Figure 10.

3.3.5. Supplier Performance (SuP)

SuP is applied when both firm and supplier see a business opportunity to collectively meet legal and customers’ demands.

SuP was described in 31 articles (Appendix E) in a manufacturing and developed European and Asian context (Table 4).

Identical to SuD, SuP is triggered by environmental legislation [121,157], but more by high expectations of what green procurement may offer [158,159] and external pressures on the firm to procure environmentally friendly products [55,104]. The latter was related to customer’s demand for these products [64,160], competition [158], and insufficient [22,121] and unreliable [104,161] supply of environmentally friendly products, which hindered the development of innovative environmentally friendly products [116]. Firms analyzed the supply chain to decide where to collaborate [98,116] to improve the product quality of environmentally friendlier products [121].

Firms usually collaborated and shared information internally and externally [55,118]. Trust [48,98], interdependency [17,21], loyalty [23], and flexibility [99,162] enabled long lasting relations between the firm and supplier [116,163]. Monitoring led to improvement plans for both the firm and supplier [22,25]. Green standards and certificates supported collaboration with suppliers on environmental criteria [17,160].

Firms and their suppliers [128,164] had a strategic [21,163] and mature [23,159] approach on procurement, with access to knowledge [64,165]. The firm implemented internal environmental targets [165,166], anticipated long term results [21,149], and valued sustainability [99,118] and individual autonomy [27,121].

SuP resulted in a reliable supply of high-quality, environmentally friendly [167,168] and innovative [99,164] products. It reduced costs [159,165] in the long term [158] for both the firm and supplier [98,159].

The SuP conceptual framework is shown in Figure 11.

4. Discussion

The CIMO framework explains under which conditions the theory works [31]. By adding moderating and mediating variables to this CIMO framework, the effects of environmental legislation are unravelled. This is performed by five CIMO-based conceptual frameworks, each explaining one green procurement strategy within a context, and each triggered by environmental legislation and the interplay of moderating and mediating variables. The five green procurement strategies have previously been described as development phases [16,25,26] in which the increased collaboration ever more decreases the environmental impact [16,27,28]. If both effective environmental legislation and collaboration achieve reduced environmental impact, ideally environmental legislation strengthens variables which encourage firms to higher levels of green procurement. The most determining variables from Figure 7 until 11 are summarized in

Table 5. Overview determining legislation, context, and variables per green procurement strategy.

Green Procurement Strategy	Context	Environmental Legislation	Three Most Determining Variables
Supplier Performance	Manufacturing firms in developed Asian and European countries	Legislation in force	External pressure: Customer demand for environmentally friendly products. Inter-firm relations: Inter-firm collaboration is common. Green embedded in firm: Firm has incorporated internal environmental targets.
Supplier Development	Manufacturing firms in developed European countries	Legislation in force	External pressure: Customer demand for environmentally friendly products. Complexity: Complex supply chain. Expected performance: Firms anticipate economic benefits in the long run.
Supplier Involvement	Manufacturing firms in developed countries	Legislation in force	Complexity: Firm has access to knowledge. Organization resources: These are available. External pressure: Customer demand for environmentally friendly products.
Supplier Selection	Manufacturing firms globally divided	Legislation set minimum demands	External pressure: Moderate. Complexity: Green procurement is considered complex. Weight decision criteria: Cost reduction outweigh environmental performance.
General practices	Diverse firms in developed European countries	Lacking legislation	External pressure: None. Weight decision criteria: Other criteria outweigh environmental criteria. Expected performance: Environmentally friendly products are expected to worsen firm performance.

.

Combining Table 5 with all elements from the conceptual frameworks results in propositions (P1 through P8). These propositions argue how a variable strengthens environmental legislation to encourage firms to higher phases.

4.1. Context

Mostly manufacturing firms practise green procurement, since these firms are more aware of pollution and used to (environmental) product standards [13,38,39]. But they seem to apply more collaborative procurement strategies than non-manufacturing firms as well (Table 4). This may be related to the fact that manufacturers rely more on their suppliers to develop the innovative products demanded by their customers. GeP is mostly counterintuitive when described in a European context. The contradiction is that Europe is said to have the most stringent environmental legislation [16,24,160]. Possibly, GeP is described in sectors where this legislation is not in force, such as non-product related products [125], the non-industrial sector, [73] and the logistics sector [81,134]. It is possible that other sectors do operate under stricter laws. SuS is described in all geographical regions (Table 4), which is in line with previous findings [66]. Firms in developed countries seem to practise more collaborative procurement strategies (Table 4). This could relate to local stringent environmental legislation [2,3,14,80]. Combining these findings, environmental legislation alone appears to not be enough. Strengthened by high external pressure to procure environmentally friendly products, firms are encouraged to participate in collaborative green procurement [39,49,68,80]. Without this pressure, environmental legislation will trigger SuS [88,115]. In conclusion, environmental legislation may be the trigger, but without external pressure firms will not be motivated to higher levels of green procurement.

P1.

Environmental legislation is effective in countries and sectors with high external pressure to reduce environmental impact.

4.2. Intervention

The findings of this study support earlier research [29,30] that the role of legislation is underexposed: 64 articles did not mention legislation and the others mostly only just mentioned that legislation triggers green procurement without further explanation. Despite this underexposure, notable differences between the five green procurement strategies and the role of environmental legislation are surfacing. Without environmental legislation, environmental demands remain nice-to-have and not decisive [125,133]. Firms practising SuS are cost and profit driven [141], aiming for operational excellence [21], which, obliged by law, add environmental criteria to the supplier selection process [12,62]. These two strategies little reduce environmental impact and hence do not contribute to the environmental legislation’s intended outcome. The three collaborative procurement strategies, which better achieves the intended result, require long term investments [15,17,108,155,156], in the case of SuD even with uncertain ROI [47,122]. Top management is likely to appoint financial resources and other capabilities to this extensive collaboration if it is expected to bring business opportunities [6,50,80,96,133,151,154,157,158,169]. The latter is likely related to higher customer demand for environmentally friendly products, as indicated in Table 5.

P2.

Triggered by environmental legislation, firms will apply collaborative green procurement if reducing environmental impact will bring or is expected to bring a business opportunity.

4.3. Moderating and Mediating Variables

Firms react on external pressure. Little customer demand for environmentally friendly products and high pressure on costs results in GeP or SuS [125,134]; and greater customer demand for environmentally friendly products may result in SuI, SuD, or SuP [160,168]. This external pressure is important for all five strategies (see Table 5). Unfortunately, external pressure is ambiguous. Some external stakeholders demand environmentally friendly products, others lowest costs and the highest profits in the short term [60,63,65,67,84,101,133,170]. Additionally, legitimate behaviour differs: external pressure to reduce environmental impact is higher in developed Western countries than elsewhere [38,64]. Multinationals are especially confronted with these ambiguous external pressures and variating legitimate behaviours [54,129]. In conclusion, this ambiguity complicates the decision to implement green procurement.

P3.

Effective environmental legislation increases unambiguous external pressure on green procurement.

The corporate strategy determines which supplier selection criteria are important and firms valuing criteria like speed, reliable supply, and costs apply GeP [61,81,125]. Firms applying SuS have added environmental criteria to the supplier selection process, but economic criteria still outweigh the environmental ones [59,65,77]. In short, these firms expect green procurement to be too expensive. Their organizational culture does not contribute to green procurement [96]. Firms which apply SuP have incorporated environmental targets in all layers of the firm and environmental targets are as equally valued as economic ones [105,116]. These firms expect business opportunities from environmentally friendly operations [6,24,84] and may proceed with environmental targets even beyond legislative demands. A green organizational culture contributes to this collaborative green procurement strategy [18,26,48,58,60,82,106,112,115,116,119,120,121]. Thus, environmental legislation should impact firms who do not pursue these environmental targets on their own. To address cost-driven firms, environmental legislation often increases the price of pollution, but may achieve little. Cost-driven firms’ reactions barely decrease environmental impact, as described in 3.3.2. In line with this, these firms may transfer the supply chain risk of reliable environmentally friendly supply to the supplier [4,68,127], which will hardly green the supply. The collaborative green procurement strategies decrease this risk by nature. The collaboration secures the reliable supply of environmentally friendly products [22,110,116,151,155,161]. Thus, increased and stringent legislation may not be the answer. Also, enforcement plays a role, though a complicated one. No enforcement of environmental law [114,128], internal guidelines [14,67], or environmental performance agreements with suppliers [49,112] results in unfair competition for complying firms [72] and the intended outcome will not be achieved [23,88]. Especially in countries with weak governmental institutions [2,24] enforcement of contracts may have some effect [170]. However, enforcement worsens the relation with suppliers as well [65] and results, counterintuitively, in supplier’s non-compliance [20,60,86,89] and green washing [4,113,139,150,170], while it increases procuring costs [8,20,21]. The same reasoning may apply for governmental enforcement as well: strict supervision may increase governmental costs with little environmental impact. Enforcement combined with improvement plans and time [22,80], supported by subsidies [6,56,67,82,89,90,91,108,115,123,128,136], does achieve the intended outcome [49,114]. Summarizing, environmental law should increase the price for pollution, targeting cost-driven firms, but is enforced by supporting firms to change internal operations to make an actual environmental impact.

P4.

Effective environmental legislation prices pollution and is enforced by supporting firms to achieve the intended outcome.

If environmental legislation demands that the environment is addressed by procurement, the latter becomes more complicated [101,102]. Firms invest to deal with this complexity. Investment is in place for training staff [56,117,126,169], supportive tools [76,123], enabling access to internal and external experts [48]), improving supply chain transparency [58,113], and developing environmental standards and certificates [15,24,56,83]. If firms experience business opportunities from green procurement, the required investments will follow [16,27,101,154,158,159]. Given their resources, large firms more easily invest in these innovations [103,107]. Without this, firms mitigate the complexity with minimum investments [3,4,20,22,65,66,85,101,107], which will achieve the legislation’s intended environmental impact only to a limited extent [3,4,68,78,97,127]. If customers do not demand environmentally friendly products, investments in green procurement will only increase costs, without increasing revenue, and in the end may result in losses. Next to this, the effect of the presence of environmentally friendlier products to procure is counterintuitive. Firms seeing business opportunities in green procurement, but confronted with lacking supply, will invest to increase this supply as described before and apply SuD or SuP. If environmentally friendlier products are widely available to procure [60,63,94,123], compatible [119] and comparable with conventional goods [61], firms also preferring conventional supplier selection criteria may procure environmentally friendly products. Thus, the presence of environmentally friendly products seems to be relevant to convince firms which are less motivated for green procurement. In conclusion, to enable GeP and SuS applying firms to make an environmental impact via green procurement, compliance to this law must not be complicated, with limited required investments.

P5.

Effective environmental legislation is easy to comply to without investments.

Some firms are more used to collaborating than others [50,57,70,98,102]. They operate in supply chains characterized by trust [8,48] and mutual dependency [21,79,100,101,103,104]. These firms are more likely to collectively comply to environmental legislation as well. Other firms operate in highly competitive markets, aiming to reduce their own costs [6,29,127,169]. These firms, supported by their power position in the chain [14,92], are more likely to dictate environmental requirements to suppliers [88,103], which however, results in green washing and limited environmentally friendly supply [4,19,80,150]. The latter is strengthened by green procurement’s required investments [2,20,77,91]. If environmental legislation would affect entire supply chains then extensive collaboration may be less necessary. However, bounded by national jurisdictions, legislation impacts global supply chains only indirectly. Foreign firms may comply, when this brings benefits. In summary, to avoid an artificial coercion to collaborate within the chain to reduce environmental impact, legislation should bring benefits for foreign suppliers to comply.

P6.

Effective environmental legislation brings benefits for the entire global supply chain to achieve the intended outcome.

The role of individual procurers to practise green procurement is considerable in firms practising GeP or SuS according to Table 4, which is in line with previous findings [39,86,92,106]. Middle management’s [87,120,122] and procurers’ knowledge [58,77,126], experience [26,91,125,127,169], personal network [28,52,85], motivation [23,61,75,114], moral attitudes [2,38,40,41,95,123,150], and soft skills [12,124] are needed to overcome green procurement’s complexity [73]. This in particular matters since these firms value economic decision criteria over environmental ones [89,140,141] and have not internalized green criteria in daily operation [20,23,39,41,59,77,92,94,97,102,106,114,115,119,123,133,138,147] and the incentive system, [50,52,86,95,150] and hence do not facilitate for procurers to overcome green procurement’s complexity. When the intrinsic motivated procurer leaves the firm, green procurement may cease. Creating awareness of the necessity to reduce environmental impact appears important [75,136]. Awareness seems to be relatively more reported in studies describing GeP and SuS (Table 4). This stresses the importance of the awareness of environmental issues to start with green procurement. Firms applying SuI, SuD, or SuP may already be aware of the necessity of green procurement. Articles describing these strategies paid only limited attention to the procurers’ role (Table 4), possibly as green targets are already incorporated within the firm [21,48,64,98,99,163,165,166] and procurers are facilitated to overcome green procurement’s complexity since environmental experts are employed [27].

P7.

Effective environmental legislation creates awareness and intrinsic motivations among management and individual procurers to achieve the intended outcome.

4.4. Outcome

The environmental impact of a product is the accomplishment of the entire supply chain [3,9,14,19] and collaboration within this chain decreases this impact most [16,27,28]. Preferably, this collaboration is extended between partners in the chain and with competitors, NGOs, science, and governments. In line with this, but perhaps counterintuitively, increased and stringent legislation is not the answer to achieve the intended outcome, but rather environmental law strengthening collaboration is. This extended collaboration achieves the intended outcome of environmental legislation, reduced environmental impact, and provides economic benefits and (product) innovations as well [14,17,20,27,48,104,118,149,156,164] through this business opportunity.

P8.

Effective environmental legislation strengthens vertical and horizontal collaboration to achieve the intended outcome and business opportunity.

5. Conclusions and Limitations

5.1. Conclusions

Developed Western countries especially have enacted environmental laws to preserve the environment. Despite these laws and although scholars worldwide have argued that sustainable procurement does not necessarily decrease profit, it appears complicated for firms to move towards truly triple bottom line functioning. Improvement of profit and reduction in environmental impact and non-violation of human rights often remains a utopia. The contribution of this study to the existing body of knowledge is the refinement of the role of environmental legislation. All findings from the literature contributed to the formulation of propositions on how to encourage firms to participate in collaborative green procurement to achieve profit without polluting the planet.

The answer to the research question “How does environmental legislation effect the environment via green procurement according to the existing body of knowledge “ is straightforward: by increasing business opportunity. Environmental legislation may be the trigger but without customers’ demand and without a business case to deliver environmentally friendly products, firms will only apply SuS with little environmental impact. Green procurement targets economic criteria alongside environmental ones [7,12,13,14,15]. Effective environmental legislation acknowledges these economic targets as well and contributes to creating business opportunities. Next to this, it takes two to tango. It takes at least two firms to reduce the environmental impact throughout the chain. Effective environmental legislation acknowledges the opportunities collaboration brings and supports collaboration to reduce environmental impact throughout the chain. A business case supports this collaboration.

This study contributes to the scientific body of knowledge twofold. Firstly, the findings from the literature were used to describe the five green procurement strategies. This explains the role of environmental legislation and other variables on green procurement strategy. This creates an understanding of why stringent environmental legislation alone may not be the answer to reduce environmental impact. Policymakers may understand better how to achieve the intended result as the study sheds light on effective environmental legislation. It may support managers as well with this explanation. The propositions indicate which variables strengthen the working of environmental legislation. These propositions are directions for future empirical studies. Secondly, this study shows how the CIMO framework, commonly used for design studies [31,32], can explain complex constructs in a social domain as well. For this the CIMO framework is extended by adding moderating and mediating variables.

5.2. Limitations

This study used the CIMO framework to explain environmental legislation’s role in reducing the environmental impact via green procurement by adding moderating and mediating variables to this framework. The mutual interplay of these variables within the context and in combination with legislation has been explained in a narrative way. The five conceptual frameworks are prototypes. Firms operating in complex supply chains may not fit within one prototype. Some variables may affect these firms more than others. Secondly, despite the careful article selection, some valuable insights might be missing. Possibly, some drivers and barriers of green procurement are missing. Next, to the best of our knowledge, the role of environmental legislation in collaborative green procurement has not been researched in this much detail before. Thus, we believe, given the quantity and diversity of the included studies, theory on green procurement is deepened. Thirdly, the author’s bias may have misinterpreted previous findings. By following the predetermined steps of a systematic literature review and addressing the defined various biases [35], this risk is minimized. Lastly, many scholars have argued to use case studies to collect empirical data [3,7,8,22,27,42,75]. These future empirical findings will support, adapt, or reject the propositions of this study, thus providing a valuable addition to this work.