Digestion and gasification
The well-to-usage carbon emissions of green gas supply chains reported in commonly used sources like www.CO2emissiefactoren.nl are currently incomplete or based on outdated practical data. Co-digestion, for example, is cited as giving a reduction of ‘only’ 33% relative to natural gas. Current practice for green gas is now fundamentally different, in terms of both digestion processes and new processes like gasification. This study provides a complete and up-to-date picture.
The emission reduction achieved with digestion chains varies from 50 to 80%, depending on feedstock and application. When the impact of avoided emissions from manure storage is also factored in, in line with the European RED calculation methodology, the CO2-eq. emission reduction for manure digestion is 183% points higher. If use is made of Carbon Capture and Storage or Utilisation (CCS/CCU) this rises to 90-136%. If the carbon emission reduction associated with by-products is also included, the range goes up to 149-223%.
The emission reduction achieved with gasification chains varies from 75 to 97%. The highest of these values is for supercritical water gasification. If CCS/CCU is assumed, this figure rises to 121-160%.