This paper presents a circular business model (CBM) designed to promote the valorization of agricultural biomass ash for producing an alternative binder in construction, aiming to reduce CO₂ emissions and landfill waste. The circular economy framework emphasizes regeneration and restoration to minimize resource and energy use, waste generation, pollution, and other environmental impacts. Aligned with these principles of sustainability, the construction industry, energy sector and food processing industry can establish a shared interest through industrial symbiosis. In the proposed CBM, waste from one industry becomes an input for another. The model leverages industrial symbiosis by using sunflower husk ash (SHA) as an alternative hydroxide activator for alkali-activated materials. A case study of companies in the Republic of Serbia that produce SHA as waste forms the basis for this model, featuring promising results of experimental testing of three alkali-activated mortars produced by activating ground-granulated blast furnace slag (GGBFS) with different SHA contents (15, 25 and 35 wt% GGBFS), instead of commercially available hydroxide activators. The potential of SHA as an alternative activator was assessed by testing flow diameter and compressive strength at 7 and 28 days of curing. The highest 28-day compressive strength was attained for the addition of 25% SHA (28.44 MPa). The promising results provided a valid basis for CBM development. The proposed CBM is stream-based, resulting from merging and upgrading two existing industrial symbioses. This study highlights the benefits of the CBM while addressing the challenges and barriers to its implementation, offering insights into the possible integration of agricultural biomass ash into sustainable construction practices.

The circular economy is considered the best principle through which sustainable practices may be established. Mineral exhaustion, decarbonisation, and waste elimination can all be addressed through a circular economy. The built environment is one of the largest waste producers and a significant user of materials such as concrete and steel. However, there are considerable barriers to the adoption of a circular economy. The objective of the study was to identify, examine, and comprehend the main challenges that impede the implementation and scaling of circular practices within the built environment. As part of the CircularB network, a questionnaire was launched in 2024 to gather opinions on the technical, political, regulatory, cultural, societal, economic, and market barriers to circular economy from built environment professionals. This paper focuses on the economic and market barriers, which were recognised as the most important according to the insights of 270 respondents. The hurdles investigated include extra costs of building insurance, inadequate collaboration, linear public procurement, unwillingness to take back used components, low awareness of exchange marketplaces, and market disconnection due to significant transport distances. Addressing these barriers plays a crucial role in advancing a circular built environment, and all stakeholders must explore solutions to overcome them.

The main objective of this article is to study the impact of trade liberalisation in Croatia as one of the first structural reforms being implemented, covering the period from 2000 to 2021. The panel data model was specified using a two-step system generalised method of moment estimator. The obtained results show that trade liberalisation measured through the specific indices encompassing a broader set of both tariff and non-tariff barriers, size of the trade sector, freedom of foreign exchange market, and capital controls positively impacted export performance. The results also showed a negative and statistically significant effect of remoteness on trade, confirming that geographical distance is an essential indicator of transportation costs. The coefficient for Schengen accession was positive and statistically significant, indicating that the Schengen agreement has boosted exports and that we can expect the same for Croatia, especially in the context of simultaneous accession to the Eurozone and the Schengen area on 1 January 2023.

This chapter explores the complexities of aligning national policies with the European Union’s objectives in transitioning to a circular economy within the construction sector. While EU directives establish general frameworks, national governments encounter challenges in adapting these directives into coherent and context-specific regulations. The chapter identifies key obstacles to effective policy implementation, including fragmentation, institutional overlap, and inconsistent terminology. Additionally, it examines how governance structures, planning traditions, and institutional cultures influence policy coherence. The analysis is based on survey results collected in 2023. Although subsequent policy and regulatory changes have occurred in the past two years, the data remain relevant, as they capture the main trends and challenges that continue to shape national approaches to circular construction. By analyzing case studies and examples from various member states, the chapter emphasizes the necessity for enhanced multilevel coordination, harmonized regulatory frameworks, and knowledge-sharing platforms. Bolstering policy coherence is crucial to ensure that national initiatives make meaningful contributions to the EU’s circular economy goals and the broader sustainability agenda.

This chapter introduces a comprehensive glossary developed as part of the COST Action CircularB, aimed at standardising terminology related to the circular economy and the built environment. Acknowledging the conceptual complexity and terminological inconsistencies across various disciplines and practices, this glossary serves as an essential reference to enhance communication, research, and implementation. It encompasses over 400 terms and definitions sourced from European regulations, ISO standards, and expert practices, providing clarity and consistency for stakeholders, including policymakers, practitioners, researchers, and industry professionals. The glossary was designed with the overarching goal of promoting a shared language that fosters collaboration and accelerates the transition toward a sustainable and circular built environment.