Kate Roberts (with input from Preservation and Property Operations colleagues at Ngā Taonga; Dan Eady, Luke Tearle and Steve Hutchinson)
Introduction
Ngā Taonga Sound & Vision is the national audiovisual archive for Aotearoa New Zealand. It is the archive for the country’s broadcast TV and radio heritage, as well as New Zealand made content on film and audiovisual formats, from the 20th-21st C, deposited by film production companies and producers. Ngā Taonga is a charitable trust which is core funded by Manatū Taonga Ministry for Culture and Heritage. It is not an archive within a broadcast agency, nor a government documentary heritage institution with an audiovisual component to its collections. It holds deposits mostly on behalf of owners, including the New Zealand Government. Our Strategic Plan prioritises the collection, management, preservation and supply of heritage audiovisual content in digital form, while also continuing to hold a legacy sub collection of film and television physical artefacts and documentation.
This case study describes the use of a method for calculating the carbon emissions of the electricity consumption used to run a system whose core function is the ingest of digital preservation bundles, their subsequent storage to LTO tape, and restoration and transcoding of digital files for supply. The method involved using a Carbon Calculation Toolkit (Excel workbook) developed by the DPC Carbon Calculation Support Group (v0.6) in 2026.
The scope of the calculation omits any fabrication or transport of the equipment to the facility and does not include the components related to staffing, or the disestablishment or destruction of the equipment at its end of life.
The key intention is to show the annual impact, in terms of greenhouse gas emissions, of running the digital preservation infrastructure, as a start for characterising, measuring and comparing all collection functions carried out at Ngā Taonga in terms of carbon emissions. The context for undertaking the calculation was the recent work done by our collegial institutions the National Library of New Zealand and Archives NZ to reduce the energy spent on physical collection storage, through better HVAC management and introduction of solar power generation.
Why we got involved in testing the DPC’s Carbon Footprint Toolkit
Ngā Taonga have been associate members of the DPC since 2022 and became aware, through networking, of the carbon footprint calculation work being undertaken to support members. Kate Roberts joined the group testing the calculation spreadsheet tool, in order to become more informed about the climate change impacts of digital preservation, at a time when data centre proliferation for AI processing is causing public concern, increasing the scrutiny of data management practices in public institutions.
What we chose to focus on
We decided to restrict the inputs for the calculation to the electrical power spent running our digital preservation equipment infrastructure, at this point, expressed in kgCO2e/year. This kept the study focussed on the functions carried out in one server room and one digital archive tape library and the cooling and humidity control running in those spaces. This could be augmented in future by also undertaking the calculations for the cost of running equipment used to transfer analogue formats to digital and to manage supply of bulk files to customers. A nominal amount could be added for the cost of people to support the system, although there is currently no permanent team structure dedicated entirely to the digital preservation effort.
What we achieved
We established that we could roughly calculate the power usage over a year by taking a single reading of the amperage running through two PDUs connected to all of the relevant digital processing equipment in our server room, converting it to Watts and then calculating the equivalent annual consumption. While the load on the equipment will be subject to a lot of fluctuation due to ingest and restoration of varying file numbers and volumes, we have not added in a mean based on a range of min to max, to avoid building in more assumptions. In discussion with Steve Hutchinson, our Property Operations Manager, with a background in power station management, I opted to add in the power usage to cool the server room and to run a process cooler to manage both temperature and humidity in the LTO tape library room which acts as our digital archive. On Steve’s advice, I chose a proportion for this power use of 25% of the power to run the digital equipment itself and added it to the two ‘on premise’ lines in the spreadsheet, incorporated in the summary below. In the summary table below the power use in the server room is allocated to the Acquisition, Transfer and Ingest row and the power use in the LTO tape library is added to the Bitstream Preservation line.
We chose to use the international average grid carbon intensity in kgCo2e/kWh of 0.445 (included in the Carbon Footprint Calculation Tool), rather than using figures for New Zealand made available online because the reporting on carbon emissions tends to focus on national aggregated power consumption of key high-volume industries and we couldn’t tell whether the data on carbon intensity would apply for all power consumers. New Zealand does have a relatively high proportion of hydro-electric power, as opposed to fossil fuel generated electricity, giving it an overall score of 83% renewable energy and 0.0148 kgCO2/kWh, so this may mean the carbon footprint is naturally lower than represented in my calculations (ref: Carbon Intensity by Country – Estimated Grid Emissions Rankings | World Power Plants).
Screenshot of the summary tab from the Carbon Footprint Calculation Tool. The spreadsheet provides a framework for calculating the carbon footprint of different areas of digital preservation activity and the summary tab brings it all together. Users of the toolkit are encouraged to focus on the areas of most interest to them (or focus their initial calculations on an achievable goal) rather than trying to calculate everything at once.
Lessons learned
We learnt that digital preservation based on LTO tape storage contributes very little to national or global greenhouse gas emissions. This is because the digital preservation bundles are stored on LTO magnetic tape so they are not in a state of constant availability (and therefore power consumption) as they would be in disc storage. Based on the information gathered we are satisfied that we can show that digital storage running in a stable annual throughput without major ingest or file delivery activity, is very economical, in terms of power, compared to maintaining a physical vault running to magnetic tape storage specifications. Being able to express this in carbon emissions equivalent volumes over time helps in any future discussion about trade-off between physical and digital storage as long term strategies (putting aside the issue of impending degralescence of legacy tape formats).
We learnt that we can roughly compare our digital preservation and its power consumption/greenhouse gas emissions to that of the Finnish national digital preservation services whose annual carbon footprint was calculated in 2023 at 21,869 kgCO2e/year (equivalent to just under the annual emissions for 3 Finns per year). This is a useful comparative set of data for us given that the Finnish digital preservation storage solution is also LTO tape.
Next steps
It would be useful to undertake the work to define the annual carbon footprint of physical collection storage by volume , and to follow up the calculation of just the digital storage with a calculation for the analogue to digital preservation workstreams in film and audiovisual collection processing. It would also be useful to establish the cost of production, transport, replacement and disposal of the digital process infrastructure, especially considering how far we are from the location of the manufacturers of the equipment. We are currently procuring a second LTO tape library to act as our second site for security of the content, in another city in NZ, so our power use for digital preservation and procurement will also increase when we factor in back-up and migration activity.