Carbon footprint

When capturing and storing CO2 (CCS) the intention is of course to reduce the climate footprint of the activity from which the CO2 is emitted as a byproduct.

But can we be sure we are not emitting more CO2 than we are permanently storing in this effort? In cooperation with DNVGL and Carbon Limits AS, Gassnova has developed a tool to calculate the amount of CO2 emitted during any given CCS operation.

What do we mean by carbon footprint? 

A carbon footprint is defined as the total amount of greenhouse gases produced which directly and indirectly support human activities, usually expressed in equivalent tonnes of carbon dioxide (CO2). 

Most of the emissions in any given carbon footprint come from "indirect" sources, such as fuel burned and resources spent to produce materials and goods far away from the final consumer. These are distinguished from “direct” sources of emissions which come from using our own products, such as driving a car or doing an activity. 

How should we calculate the carbon footprint of an activity, process or product? 

Several free online carbon footprint calculators exist, including a few supported by publicly available peer-reviewed data and calculations. These are largely aimed at educating consumers about their activities and preferences. 

To be more accurate, calculation of a carbon footprint should follow the cradle-to-grave approach used in life cycle assessments. (These principles are described in ISO standards 14040 and 14044.) 

In effect, this means it is necessary to establish a kind of carbon accounting system where all greenhouse gas emissions caused by all materials, chemicals, fuels and transport required to produce a product, run a process, or carry out a certain activity is summarized. As a result, a considerable amount of basic data and emission factors are required to succeed in establishing a reliable carbon footprint. 

Why is it important to assess the carbon footprint of CCS? 

Questions are often raised whether it is worthwhile introducing CCS as CO2 emission mitigating measure. CCS has been accused of being both inefficient and high energy consumption. Since the objective of CCS is to reduce CO2 emissions by capturing and permanently storing CO2 in subsurface/subsea reservoirs, it makes sense that CCS should not lead to more CO2 being emitted than is ultimately stored. Gassnova thus felt the urgent need for establishing a possibility to do sound and best possible calculations of the carbon footprint for CCS. 

Gassnova’s footprint calculator 

In cooperation with DNVGL and Carbon Limits AS, Gassnova has developed a tool to calculate the amount of CO2 emitted during any given CCS operation. 

It is based on an Excel spreadsheet model and the greenhouse gas emission factors are taken from open source databases. Gassnova will use this tool to summarize the carbon footprint of the present Full-scale CCS project. 

Project partners Fortum Oslo Varme, Norcem and Equinor will contribute with consumption figures for their aspects of the project in waste-to-energy capture, concrete production capture and transportation and storage, respectively. 

What do we know now and when will we get the complete answer? 

Preliminary results based on very early input data indicate a carbon footprint (i.e. the CO2 emitted from all material, chemicals and fuels consumed and all necessary transport and activities involved in constructing and operating one CCS chain) that will be in the range of 3-10% of the CO2 stored. This is further dependent on the number of years the storage facility is in operation and whether the full capacity of the storage site is used. 

When the FEED studies mentioned above are completed at the end of 2019 and all necessary input data has been established, Gassnova will prepare final carbon footprint calculations for the project.