To slow down climate warming and achieve sustainable development, the Paris Agreement attempts to establish cooperative approaches (Article 6.2 in the Paris Agreement) and a sustainable development mechanism (Article 6.4 in the Paris Agreement) for carbon trading. However, deficiencies in implementation exist due to a lack of systematic execution regulations and an integrated management system. To strengthen the effectiveness of the two carbon trading mechanisms for reducing carbon emission, this paper aims to propose an implementation framework of cooperative approaches and a sustainable development mechanism. Based on the international regime theory in global climate change and the nine elements of the market mechanism, the paper makes use of comparative analysis to discuss the type of mechanism, coverage of the system, operational framework, governance framework, and implementation framework of cooperative approaches and a sustainable development mechanism. The main results and conclusions are as follows: (1) Cooperative approaches are considered as project-based and quota-/credit-based carbon market mechanisms. Under cooperative approaches, trading units should be authorized at the international-regional and sub-regional levels. CO₂, CH₄, N₂O, HFCs, PFCs, SF₆, and NF₃ are the seven types of greenhouse gases that could be traded through cooperative approaches, and they shall be accounted by the unit of CO₂-eq. (2) The sustainable development mechanism is considered as an industry-based and credit-based carbon market framework. Under the sustainable development mechanism, trading units should be authorized at the international level. CO₂, CH₄, N₂O, and PFCs can work in the sustainable development mechanism as subject matters. The unit of gases shall be CO₂-eq as well. (3) The implementation framework of cooperative approaches ought to follow three stages: project preparation, project submission, and auditing, as well as internationally transferred mitigation outcomes transfer. The implementation framework of the sustainable development mechanism ought to contain three stages: project development and review, project implementation and monitoring, and project acceptance and unit transfer. The authors hope it can work as a guideline for the early implementation stage of the cooperative approaches and sustainable development mechanism to stimulate carbon reduction and further slow climate change.

In high-density cities around the world, the contradiction of sustaining development and limited resources has become more evident. Transforming historic industrial buildings, through both functional and spatial adjustments, has emerged as a key strategy to manage these challenges effectively. There is a significant demand for the quick regeneration of industrial heritage districts, resulting in the emergence of various implementation modes (IMs). While the Sustainable Development Goals (SDGs) have gained widespread acceptance, the integration of sustainability principles into urban regeneration practices has strengthened globally. However, in many regions, approaches to achieving sustainable regeneration are still unclear, with a lack of evaluation and adjustment of sustainability performance (SP). This paper combines qualitative analysis and a quantitative assessment of indicators to compare three representative case studies with different IMs. It explores whether there is a connection between the chosen IM and SP, examines the mechanisms of impact, and discusses how to select the most suitable IM for industrial heritage regeneration. The study confirms the practicality of an SP evaluation system and identifies key factors within IMs that affect SP. Future research is expected to produce tools that support the promotion of sustainability in industrial heritage regeneration efforts.

Carbon substrate is required by biological nutrient removal (BNR) microorganism, but it is usually insufficient in the influent of many municipal wastewater treatment plants. In this study the use of ethanol-enriched fermentation liquid, which was derived from dairy wastewater, as the preferred carbon substrate of BNR was reported. First, the application of dairy wastewater and food processing wastewater and their fermentation liquid as the carbon substrate of BNR was compared in the short-term tests. The fermented wastewater showed higher BNR performance than the unfermented one, and the fermentation liquid of dairy wastewater (FL-DW), which was obtained under pH 8 and fermentation time of 6 day, exhibited the highest phosphorus (95.5%) and total nitrogen (97.6%) removal efficiencies due to its high ethanol content (57.9%). Then, the long-term performance of FL-DW acting as the carbon substrate of BNR was compared with that of acetate and ethanol, and the FL-DW showed the greatest phosphorus and total nitrogen removal. Further investigation showed that the use of FL-DW caused the highest polyhydroxyalkanoates (PHAs) synthesis in BNR microbial cells, and more PHAs were used for phosphorus uptake and denitrification rather than glycogen synthesis and microbial growth. The FL-DW can be used as a preferred carbon substrate for BNR microbes. Abbreviations: AB: aerobic end sludge active biomass; BNR: biological nutrient removal; DW: dairy wastewater; FL-DW: fermentation liquid of dairy wastewater; FPW: food processing wastewater; FL-FPW: fermentation liquid of food processing wastewater; PHAs: polyhydroxyalkanoates; PHB: poly-3-hydroxybutyrate; PHV: poly-3-hydroxyvalerate; PH2MV: poly-3-hydroxy-2- methylvalerate; PAOs: phosphorus accumulating organisms; SBR: sequencing batch reactor; SOP: soluble ortho-phosphorus; TN: total nitrogen; TSS: total suspended solids; VSS: volatile suspended solids; VFAs: volatile fatty acids; WWTPs: wastewater treatment plants