## 1 Introduction  
Around the world, public organisations have designed sustainable public procurement (SPP) policies to oblige suppliers to contribute to the achievement of their policy objectives [1, 2]. Public procurement refers to the acquisition of goods and services by government or public sector organisations [3]. In the European Union, public organisations annually spend approximately 16% of the gross domestic product on public procurement [4], and it is increasingly used as policy tool [5]. In the Netherlands, public procurement is for example used to stimulate the production and consumption of environmentally friendly products, diminish the distance to the labour market for the long-term unemployed, and drive innovation [6]. The uptake and implementation of these SPP policies are the topic of a growing number of academic studies [7]. They show that the uptake and implementation of SPP varies greatly across countries, organisations, and projects [8, 9]. One explanation for this is that inside the public organisations, changes have to be made and barriers removed, which does not always happen [10]. [PERSON], for example, showed that public procurers that are not affectively motivated to SPP, implement fewer SPP than public procurers that are affectively motivated [10]. Knowledge is also frequently identified as a barrier or driver of SPP. Due to the complexity and contested nature of sustainability a lack of knowledge makes it difficult for public procurers to see the potential of SPP, which drives them to make safe and traditional choices [8; 11; 12; 13; 14], and which as such can enable or disable procurers from procuring sustainability. Other studies explain that public procurers also need to have the opportunity to procure in a sustainable manner. [PERSON] and [PERSON] [8], for example, explain that it helps if procurers work in an organisation with a climate that is supportive of change and doing something new. Although we know from extant studies that the ability, motivation and opportunity to procure in a sustainable manner affect the implementation of SPP, the majority of these studies examined it only in the context of one type of SPP; for example, only in the context of green public procurement (GPP) [9; 15], but not in the context of social procurement, fair trade or circular economy. SPP is considered to be an umbrella concept that encompasses \"a concern for social, economic _and_ environmental aspects of procurement decisions\" [16]. Public organisations have thus developed SPP policies that, for example, aim to reduce the environmental impact of production and consumption (green public procurement or GPP), but also policies that aim to reduce the employability chances for the long-term unemployed (social return on investment or SROI), that drive innovation (IPP) or that reduce waste and work toward a more circular economy (CIE). Although the literature has thus identified ability, motivation, and opportunity as barriers and drivers of SPP, we do not know if the barriers and drivers for all types of SPP are the same because it only examined these factors in regards to specific types of SPP. The goal of this paper is therefore to examine the effect of ability, motivation, and opportunity on the implementation of six types of SPP policies in the Dutch public sector. More information about the types of SPP is presented in Section 2. The following research question has therefore been formulated: _If and how do the perceived ability, motivation, and opportunity to procure in a sustainable manner affect the implementation of the various types of SPP?_ To answer this question, a survey was administered amongst Dutch public procurers. The Netherlands is considered a frontrunner with regards to SPP [17] and has developed and implemented a wide range of SPP policies [6]; it is therefore considered an ideal context for examining the impact of various barriers on the various types of SPP.