Green certificates, limitation for their use in LCA and proposal for standardization

Since the end of last century, green certificates (GCs) have been gradually created in different regions or countries to help promote and contribute to renewable energy. Especially in EU, there is a long evolution for Guarantees of Origin (GOs) with series of legislations implemented and organizations founded for managing the GOs market. Nowadays, GCs are often used in environmental assessment to report relevant carbon emissions (Scope 2 emissions). However, when using GCs to apply in life cycle assessment (LCA), GCs itself has several limits, such as double counting, potential unverifiability of GCs, etc. This study offers a standardized procedure for integrating GCs into LCA, with the goal of offering broad guidelines and norms to address the chaos of GC abuse into environmental assessment globally. The whole procedures include mainly four phases: 1) Before and during GCs trading; 2) Before retiring GCs and using LCA; 3) When using LCA; 4) After using LCA. First, before and during GCs trading, it is necessary to build a GCs generating and trading system from ensuring the reliability of GCs, which is recommended as the four-component system by smart meters, distributed ledger technology, trading platform, and client application. Second, before retiring GCs and using LCA, any firm needs to determine the annual renewables (RES) usage in the company level, classify GCs by geographical and temporal matching, and check the types of GCs (bundled or unbundled GCs). Third, when using LCA, it is mandatory to uniformly choose attributional LCA approach to do environmental reporting or claims, meanwhile guaranteeing market-based accounting for Scope 2 emission in the whole market, as well as using reliable data base for residual mix and relevant emission factors. Finally, after using LCA, electricity balance sheets and renewable energy certificate details should also be included in the LCA background report. In order to test the efficiency of the GCs’ standardization in LCA, a single Italian ceramic plant was chosen for the case study in this work, which employed the suggested GC standards into LCA. Through the simulation of multiple scenarios, the company's results demonstrate how successful it is to stop the invalid carbon reduction (cut off 10~15% declared carbon emissions) and enhance the final emissions' reliability through standardization. In addition to the proposal, for further policy development, policymakers need to focus on the aspects like issuing GCs, resolving discrepancies in GC data, etc.