Categories
INFO SHEETS

STiCH Carbon Calculator Technical Document/FAQ

Authors: Matthew Eckelman, Sarah Nunberg

Introduction to the STiCH Carbon Calculator

A core element of the Sustainability Tools in Cultural Heritage (STiCH) project is a user-driven online Carbon Calculator that allows conservators and allied professionals to assess the sustainability of the products and processes they use in their day-to-day practices. The calculator includes data for more than 1,000 common materials used in the cultural heritage field, with items being added continuously with feedback from users.

The Calculator was designed by a team of conservators, designers, and engineers to be intuitive and easy to use. The Calculator currently exists as a ‘black box’, wherein quantities of materials are entered by users and the tool then provides an overall carbon footprint of each entry. This Technical Document and FAQ aims to answer questions about the design of the Calculator and the data and methodology that sit behind it.


How was the Calculator Constructed?

The construction of the Calculator took place in several steps, as detailed below. Work began on a beta version, funded by a 2017-2018 Tier I Research and Development Grant from the US National Endowment for the Humanities. This beta version was tested with small groups of potential users through a series of workshops, and their feedback was used to guide the design of the current Carbon Calculator.

Step 1- Assemble Product Lists 
Lists of products and materials of interest to the cultural heritage community were collected based on input from more than 15 peers, students, and institutions, as well as existing lists such as CAMEO (www.cameo.mfa.org) and lists provided by the AIC Materials Working Group. These lists were then collated and each item entered into a shared database with identifying information including: product name; purchasing size and quantity (in units of g, L, m3, etc.); manufacturer; weblinks; and vendor (if applicable).

Step 2- Classification 
Products and materials were then classified into 13 categories and 99 sub-categories according to their use (see Table 1). Many materials could be classified under multiple categories, but for data integrity and look-up purposes, each material only appears in the database once, under one category and one sub-category. 

Table 1.  STiCH carbon calculator tool categories and sub-categories

Step 3- Specifications 
To determine the carbon footprint and other environmental health and safety information of a product, the composition and material specifications are required. Some STiCH products are essentially pure chemicals, such as acetone, while others, such as archival blue board, are complex mixtures of chemicals and/or materials, and require detailed investigation. To complete the Carbon Calculator, product specification data were collected manually through the research efforts of more than 27 collaborators, institutions, and already-assembled lists.  Data collected included: chemical or material composition (in mass %), density, and any hazard information embedded in safety data sheets (SDS). These data were then entered into the shared spreadsheet (Figure 1).

Figure 1. Screenshot of STiCH Carbon Calculator tool shared spreadsheet

Step 4- Match Items with Life Cycle Inventory Data
Based on the chemicals or materials specified for each product, a matching chemical or material was identified from the existing life cycle inventory (LCI) database ecoinvent 3.6, a commercial database of environmental data for thousands of products and processes, published in Switzerland (https://ecoinvent.org/). There are several system models available from ecoinvent that follow different accounting rules on how recycling of materials is treated; here, the ‘cut-off’ database was used. Once a suitable match was found in the ecoinvent database, the corresponding cradle-to-gate greenhouse gas (GHG) emissions factor was extracted and entered into the STiCH shared spreadsheet. The ecoinvent database differentiates entries by where manufacturing takes place. In all cases, a market average was used for consistency. 

Step 5- Convert Units and Average to Product

Emissions factors from ecoinvent are given in specified units, typically kg CO2 equivalents per kg of material. These units might be different than the units of purchase as seen by cultural heritage professionals. For example, acetone is typically purchased by the liter (L), but the emissions factor is expressed in mass units (kg) of acetone. Using density information collected during Step 3, unit conversions were made so that the purchase unit and emissions factor unit match. For ‘pure’ products made up of only one chemical or material, the converted emissions factor represents the carbon footprint of one unit of purchase. For products that are made up of more than one chemical or material, the corresponding emissions factors were mass-averaged according to the composition of the product. An example calculation is given below.

Suppose a STiCH product is made up of two materials. 
Material A: makes up 80% of the product
has a carbon footprint of 3 kg CO2e/kg.
Material B: makes up 20% of the product
has a carbon footprint of 7 kg CO2e/kg.  

Mass-averaged carbon footprint per kg of the product is:
(3 kg CO2e/kg)*(0.8) + (7 kg CO2e/kg)*(0.2) = 3.8 kg CO2e/kg

If the product has a mass of 4 kg, the total carbon footprint is: 
(4 kg)*(3.8 kg CO2e/kg) = 15.2 kg CO2e/kg

Step 6- Front-end Design of the Calculator 
A web programmer created a plug-in for the STiCH wordpress site that pulls the final carbon emissions results for each product per unit of purchase. Users who want to calculate carbon footprints and/or look up links to environmental health & safety information sheets simply browse the categories or search directly for a product of interest, add to the calculation, and enter the relevant quantities, as shown in Figure 2. As additional products are added to the back-end shared spreadsheet, the new results will be pulled into the front-end calculator.

Figure 2. Screenshot of STiCH Carbon Calculator bar graph and results chart

FAQ

Is transportation included in the calculator?
Yes and no. Transportation that occurs ‘upstream’ in the supply chain is included, but the final transportation from retail to where the products are used is not included, as this is completely dependent on the location of the purchaser and so it is not possible to include without explicit user data on location. The carbon factors extracted from the ecoinvent database are ‘cradle-to-gate’, meaning that they only include up to the point of shipping by the manufacturer. Most published LCAs from manufacturers have the same cradle-to-gate scope. Final transportation typically makes up a small percentage (5-10%) of product emissions in LCA, so its omission is unlikely to have any meaningful impact on the comparative results. The project team is considering adding a way for users to specify their distance from manufacturers in future versions of the calculator.

In contrast, the Case Studies that are included in STiCH do include final transportation because these assessments are carried out with partners in specific known locations.


Is disposal included in the Calculator?
No, disposal is not included. The carbon factors extracted from the ecoinvent database are ‘cradle-to-gate’, meaning that they only include up to the point of shipping by the manufacturer, and not final transportation, use, or waste management. Most published LCAs from manufacturers have the same cradle-to-gate scope. Carbon emissions from waste disposal depend on local waste management practices, both between and within countries, and so it is not possible to include without explicit user data on location. The project team is considering adding a way for users to specify local waste management practices in future versions of the calculator.

In contrast, the Case Studies that are included in STiCH do include waste management because these assessments are carried out with partners in specific known locations.


How do I learn more about carbon footprinting / life cycle assessment?
There are many excellent resources on carbon footprinting and life cycle assessment, as these tools have gained in popularity and importance in many different sectors. One of the most influential groups behind carbon accounting has been the GHG Protocol (https://ghgprotocol.org/).  We have prepared an LCA factsheet to introduce the basic method, which can be found on the STiCH website.


I have seen other carbon calculators.  What makes this one different?
Carbon calculators have been developed for individuals, households, industries, and institutions at different scales. They are usually divided up into different general sections, such as energy use, transportation, and overall categories of purchasing. What makes the STiCH calculator unique and useful is that it is both highly detailed and specific to the cultural heritage sector. For example, whereas most calculators will simply have a single question where users can enter in total use of a material (such as paper), the STiCH calculator differentiates among many types of paper, tissue, and board materials used in the field. This allows STiCH users to compare products based on carbon emissions and make decisions at a product level, rather than just seeing an aggregated total.


What GHG Accounting Scopes does the STiCH Carbon Calculator cover?
Carbon footprint accounting is most commonly separated into three ‘Scopes’, following conventions set by the GHG Protocol (https://ghgprotocol.org/). Scope 1 includes on-site emissions. Scope 2 includes emissions from purchased energy such as electricity. Scope 3 includes everything else, most prominently emissions associated with non-energy purchases of goods and services (otherwise known as supply chain emissions). Most existing calculators cover only Scope 1 and Scope 2 emissions because these are relatively straightforward to calculate based on utility bills, whereas Scope 3 emissions are often excluded because they are much more complex to track. In contrast, the STiCH carbon calculator focuses exclusively on Scope 3 emissions from materials and products used in the cultural heritage field. 


Am I able to see the shared spreadsheet where all the raw data are?
Unfortunately, data copyright restrictions require the raw carbon footprint calculations to be visible only to ecoinvent database license holders, so the tool instead provides the carbon footprint results per unit of purchase for each overall product.


What about Environmental Impacts other than Carbon Footprint?
Carbon footprinting is just one type of environmental impact, albeit a critical one. Other types of environmental impacts such as ozone depletion, acidification, eutrophication, or toxicity, can be calculated using the same life cycle assessment (LCA) approach as carbon. The community of cultural heritage professionals involved in the project have identified carbon footprint as the environmental metric they most want to see, but the back-end of the tool has been designed so that additional environmental data can easily be imported from the ecoinvent database if users desire.


Where is Environmental Health & Safety Data (EHS) displayed?
If a safety data sheet (SDS) exists for the product of interest, a link will be displayed in the calculator on the right side of the results table. This EHS information is not linked to the quantity of each product used, it is simply provided as information on inherent chemical hazards. LCA can also be used to evaluate toxicity through a risk-based framework, as long as there is data on the quantity of product emissions (e.g., mass of evaporated solvent) and the exposure potential (e.g., distance to breathing zone, presence of fume hood or other ventilation). These data are use-specific and are therefore not included in the Calculator, but toxicity is considered in the STiCH Case Studies because these assessments are carried out with partners where exact practices can be observed and measured.


How do I compare products?
Products can be compared by entering them as two different lines within the calculator, or by simply running the calculations one at a time. In order to capture the efficacy of each option, products should be compared in terms of the quantities needed to perform a certain task or function, what is called the ‘functional unit’ in life cycle assessment.


Can I use the calculator to find the carbon footprint of an entire treatment?
Yes! Simply add each material or product needed for the treatment, including the quantity of each, and the calculator will provide the total greenhouse gas emissions in units of kg CO2 equivalents, which is how carbon footprints are measured. The Calculator results tell you ‘cradle-to-gate’ emissions, that is, emissions associated with the manufacture and supply chain of each product. This is different than the ‘cradle-to-gate’ scope of the STiCH Case Studies, which are much more complex and include details of final transportation, product use, and waste management.


Can I make the results specific to my own country/region?
No. We have designed the Calculator so that the factors represent a global average in terms of where items are produced and how far they have to travel. This means that results can be compared for institutions in different locations. 


Are carbon emissions, greenhouse gas emissions, and carbon footprint different?
Yes, these terms are different. Carbon emissions refer to carbon dioxide only, while greenhouse gas emissions refer to all types of emissions that cause radiative forcing in the atmosphere. The major greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), fluorinated gases (F-gases).  Carbon emissions and/or greenhouse gas emissions come from a wide variety of sources, dominated by fossil fuel combustion, but also included agriculture, industrial processes, and natural sources such as fires. A carbon footprint refers to the total greenhouse gas emissions (not only CO2) of a product, process, or organization.


What if I don’t see the product or material I want to evaluate?
While the STiCH Carbon Calculator includes more than 1,000 items, it cannot include every possible item that conservation professionals use.  If you cannot find an entry that accurately represents your item of interest, please let us know by sending a message to stich@culturalheritage.org or use the contact form on the STiCH website: https://stich.culturalheritage.org/about/.  If we agree that your item should be added to the tool, we will include it in future versions.


Why am I seeing different results for products that are made of the same material?
Certain sub-categories of materials and products in the STiCH Calculator are basically made of the same material but may have different trade names, manufacturers, and vendors. It is possible that two items that are made of the same materials could have different carbon footprints if the unit of purchase is different. Carbon emissions factors are typically in mass or volume terms. So, if two tissues are being compared that are made of the same fibers and have the same area but have different thicknesses, then their masses and carbon footprints will differ.


Why am I seeing the same results for products that are made by different vendors?
Certain sub-categories of materials and products in the STiCH Calculator are basically made of the same material but may have different trade names, manufacturers, and vendors. Carbon footprints reflect the physical composition of products and the processes used in their manufacturer. So, if two products have essentially the same composition and are produced using the same standard manufacturing processes, then they will have the same carbon footprints per unit mass.


Some of the calculator entries say ‘coming soon’.  How soon?
The manual calculations behind the Carbon Calculator are time-consuming, and we are constantly adding items to our lists for consideration. We refresh the data behind the calculator periodically.  If there are certain items that you want to see sooner rather than later, please drop us a line at stich@culturalheritage.org or use the contact form on the STiCH website: https://stich.culturalheritage.org/about/, and we will prioritize them for the next refresh.

Leave a Reply

Your email address will not be published.