The ecoinvent database version 3 (part I): overview and methodology. Gregor Wernet, Christian Bauer, Bernhard Steubing, Jürgen Reinhard, Emilia Moreno-Ruiz, Bo Weidema. Received: 17 June 2015 / Accepted: 6 March 2016 / Published online: 21 April 2016. © Springer-Verlag Berlin Heidelberg 2016. Abstract: The ecoinvent database is the largest transparent unit-process LCI database worldwide. Version 3, released in 2013, introduced significant methodological and technological improvements, along with many new and updated datasets. The aim was to expand the database's content, support regionalized LCIA, offer multiple system models, allow easier integration of data from different regions, and reduce maintenance efforts. This article describes the methodological developments. Methods: In version 3, modeling choices and raw data were separated, enabling different sets of modeling choices or system models to be applied to the same raw data with little effort. Flow properties were added to all exchanges in the database, providing more information on the inventory and allowing fast calculation of mass and other balances. Version 3.1 is generally water-balanced, allowing determination of water use and consumption. Consumption mixes, called market datasets, were added to the database, along with global background data, often extrapolated from regional data. Results and discussion: With hundreds of new unit processes from regions outside Europe, these changes improved modeling of global supply chains and more realistic distribution of impacts in regionalized LCIA. The new mixes facilitated further regionalization due to the availability of background data for all regions. Conclusions: Version 3 substantially expands the goals and scopes of LCA studies ecoinvent can support. The new system models allow new, different studies to be performed. Global supply chains and market datasets increase the database's relevance outside Europe, and regionalized LCA is supported by the data. Datasets are more transparent, include more information, and support, e.g., water balances. The developments also support easier collaboration with other database initiatives, as demonstrated by a first successful collaboration with a data project in Québec. Version 3 has set the foundation for expanding ecoinvent from a mostly regional into a truly global database and offers many new insights beyond the thousands of new and updated datasets it also introduced. Keywords: Ecoinvent version 3; Life cycle assessment (LCA); Life cycle inventory (LCI) database; Parametrization; Regionalization; System model.The ecoinvent database version 3 (part I): overview and methodology. Gregor Wernet, Christian Bauer, Bernhard Steubing, Jürgen Reinhard, Emilia Moreno-Ruiz, Bo Weidema. Received: 17 June 2015 / Accepted: 6 March 2016 / Published online: 21 April 2016. © Springer-Verlag Berlin Heidelberg 2016. Abstract: The ecoinvent database is the largest transparent unit-process LCI database worldwide. Version 3, released in 2013, introduced significant methodological and technological improvements, along with many new and updated datasets. The aim was to expand the database's content, support regionalized LCIA, offer multiple system models, allow easier integration of data from different regions, and reduce maintenance efforts. This article describes the methodological developments. Methods: In version 3, modeling choices and raw data were separated, enabling different sets of modeling choices or system models to be applied to the same raw data with little effort. Flow properties were added to all exchanges in the database, providing more information on the inventory and allowing fast calculation of mass and other balances. Version 3.1 is generally water-balanced, allowing determination of water use and consumption. Consumption mixes, called market datasets, were added to the database, along with global background data, often extrapolated from regional data. Results and discussion: With hundreds of new unit processes from regions outside Europe, these changes improved modeling of global supply chains and more realistic distribution of impacts in regionalized LCIA. The new mixes facilitated further regionalization due to the availability of background data for all regions. Conclusions: Version 3 substantially expands the goals and scopes of LCA studies ecoinvent can support. The new system models allow new, different studies to be performed. Global supply chains and market datasets increase the database's relevance outside Europe, and regionalized LCA is supported by the data. Datasets are more transparent, include more information, and support, e.g., water balances. The developments also support easier collaboration with other database initiatives, as demonstrated by a first successful collaboration with a data project in Québec. Version 3 has set the foundation for expanding ecoinvent from a mostly regional into a truly global database and offers many new insights beyond the thousands of new and updated datasets it also introduced. Keywords: Ecoinvent version 3; Life cycle assessment (LCA); Life cycle inventory (LCI) database; Parametrization; Regionalization; System model.