Environmental and resource effects of CCU – a literature study

The main goal of this study was to examine how different CCU routes perform environmentally and regarding resource efficiency. The report is a delivery in the ‘CCUS Verdiskapingspotensialet – næringsutvikling og innovasjon’ project for the Viken region.

The literature study has focused on finding reliable and quality assured LCA (Life Cycle Assessment)-based climate change results. To obtain this, NORSUS has searched for papers published in scientific journals. Quantitative results have only been included from papers which follow the recommended methodology for LCA of CCS and CCU systems; this being connected to system boundaries, the use of system expansion to solve multifunctionality, the inclusion of reference systems, and the definition of CCU. The papers found are all desktop studies, as none describes physical facilities running today.

NORSUS finds the following conclusions for the different CCU product categories justified for climate change:

1          For chemicals and fuels:

  • Today and in the near future, CCS systems have a better performance than CCU systems. Not capturing CO2 at all can also perform better than a CCU system.
  • In a fully decarbonised future for electricity grid mix and in ‘electricity lock-in’ situations, CCU systems are preferable.
  • The reason for the diverging conclusions depending on time horizon is the large consumption of renewable electricity in the process of converting CO2 into chemicals/fuels. This electricity can, in the compared systems, be used to substitute other electricity sources.

2          For direct use of CO2:

  • Direct use of CO2 is beneficial.

3          For mineralisation:

  • CCU systems where CO2 is mineralised have a better performance than CCS systems. How much better depends largely on the climate burden of the product being substituted by mineralised CO2.

An important aspect to consider when developing strategies on a political level, is whether suboptimisation can be tolerated as a means to develop technology and markets for a fossil free future. This is relevant, for example, for the aviation sector.