Understanding Carbon Footprinting & Making the Case for UV/EB Sustainability
By Dr. Doreen M. Monteleone, director of sustainability & EHS initiatives
RadTech International North America
TABLE 1. The global warming potential (GWP) of gases and groups of gases that contribute to global warming. The amount of gas is multiplied by the GWP to calculate the CO2e. According to the Intergovernmental Panel on Climate Change (IPCC), GWPs typically have an uncertainty of roughly ±35 percent, though some have greater uncertainty than others.
The generation of electricity, heat or steam falls under Scope 1 of the Greenhouse Gas Protocol.
TABLE 2. Some key sources of information on reducing GHG emissions and carbon footprint calculations – available online.
With increasing emphasis on sustainable practices, every industry group is undergoing major changes in the way it does business. From the supply chain to the branding process, focus is on meeting the goals of sustainable production and profit. Although sustainable business practices are being driven by companies wanting to be sustainability leaders, often it is the result of customer demands.
Because of sustainability requirements of companies – most notably the worlds largest retailer, Walmart – sustainability has gotten the attention of everyone. Minimizing carbon footprinting has become a requirement to do business with Walmart. For many production lines – from coatings to package printing – the potential impact on a facilitys carbon footprint often positions the use of UV/EB over traditional systems as a more sustainable business practice. Although the amount of solvent in formulations can vary, quite often, facilities using UV/EB systems have a lower carbon footprint than comparable operations using traditional alternatives, such as organic solvent or water-based systems. To determine the extent of the sustainability advantage to UV/EB end users requires an understanding of the elements of a carbon footprint.
A carbon footprint is a measure of greenhouse gas (GHG) emissions that contribute to global warming. GHGs include carbon dioxide (CO2) and other gases that are expressed as equivalent (CO2e). Because of their heat trapping abilities, emissions of methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) also are included when calculating a carbon footprint. By using conversion factors called global warming potentials (GWPs), GHGs are all measured against the heat trapping ability of CO2 to calculate the CO2e (Table 1). In total, these compounds comprise a carbon footprint typically expressed in a unit of weight, such as tons.
Although there is no mandatory standard for measuring total GHG emissions, the international voluntary standard – the Greenhouse Gas Protocol (GHG Protocol) – is used worldwide. The GHG Protocol divides the types of GHG emission sources into three “scopes.” Scope 1 includes GHGs from direct emissions of onsite combustion and mobile sources. Scope 2 includes indirect emissions from purchased electricity and is, perhaps, the most straightforward scope to calculate. Scope 3 includes emissions from product transport, employee business travel and employee commuting. It is the most challenging to calculate and requires significant documentation of the sources and information used to calculate the carbon emissions. Quite often it is considered an optional calculation.
Although the GHG Protocol has defined the various scopes, it can be confusing as to what is included in each set of calculations. So, at every step, it is important to keep detailed documentation of emission sources included in the calculation, as well as any conversion factors to ensure consistency when making comparisons over time or with other facilities.
Scope 1: Direct emissions from sources owned or controlled. Direct GHG emissions are principally the result of the following types of activities:
- Generation of electricity, heat or steam. These emissions result from oxidative combustion (burning) of fuels in stationary sources (e.g., boilers, furnaces, turbines and oxidizers).
- Physical or chemical processing. Most of these emissions result from manufacture or processing of chemicals and materials.
- Transportation of materials, products, waste and employees. These emissions result from the combustion of fuels in company-owned/controlled mobile combustion sources (e.g., trucks, trains, ships, airplanes, buses and cars).
- Fugitive emissions. These emissions result from intentional or unintentional releases (e.g., equipment leaks from joints, seals, packing and gaskets); methane emissions from coal mines and venting; CO2; hydrofluorocarbon (HFC) emissions during the use of refrigeration and air conditioning equipment; and methane leakages from gas transport.
For a typical manufacturing facility, Scope 1 emissions would include, but are not limited to:
- Emergency generators
- Gas boilers, process dryers and water heaters
- Air pollution control devices
- Company-owned or leased vehicles, power landscape equipment
- Propane forklifts and landscaping equipment
- Refrigerants (HFCs)
- CO2 used in some electron-beam coating lines
Scope 2: Emissions from the generation of purchased electricity that is consumed in, owned or controlled equipment or operations. GHG emissions from electricity generation will depend on the fuel sources used by the utility and may include any one or a combination of coal, oil, natural gas, hydropower, nuclear or wind power. The US Environmental Protection Agency (US EPA) publishes the Emissions & Generation Resource Integrated Database (eGrid), which includes conversion factors based on the fuel sources used for electricity generation by utilities nationwide.
Scope 3: Optional emissions include all indirect emissions not covered in Scope 2. It includes upstream and downstream emissions; emissions resulting from the extraction and production of purchased materials and fuels; transport-related activities in vehicles not owned or controlled by the entity; use of sold products and services; outsourced activities; recycling of used products, waste disposal, etc.
For a typical manufacturing facility, Scope 3 emissions might include:
- Product materials produced by suppliers
- Waste disposal
- Employee commuting
- Business travel
When calculating a carbon footprint, a company first must determine to what level or scope the calculations will be made and then compile the associated data. Once the boundaries are selected, consistent methodology is paramount to compare changes over time.
The three basic steps to determining total carbon emissions from a facility are list, convert and add.
- List: List each of the gases to be quantified and determine the emissions of each. For example, 1,000 kilograms of CO2 may be emitted along with 100 grams of methane (CH4) and 50 grams of nitrous oxide (N2O).
- Convert: Convert the non-CO2 emissions to CO2e emissions by multiplying by their GWP (Table 1), which indicates the relationship between CO2 emissions to those of various other non-CO2 greenhouse gases.
- Add: Add the CO2 emissions to the resulting CO2e emissions of the other pollutants. Make sure to convert all emissions to either kilograms or metric tons before adding. The final number will represent the total greenhouse gases emitted into the atmosphere on a CO2e basis.
Numerous websites provide detailed information to determine emissions of GHGs from various sources and calculate a carbon footprint. A thorough search on the internet will provide up-to-date conversions, but a few key sites are listed in Table 2.
For a facility calculating a footprint for the first time, a baseline carbon footprint is useful to establish – to analyze future trends and make comparisons to similar facilities. Once the size of a carbon footprint is calculated and understood, strategies can be devised to reduce it by technological developments and/or better process and facility management. For example, purchased electricity represents one of the largest sources of GHG emissions and is the most significant opportunity to reduce these emissions. So, technology that serves to reduce electricity use also will impact a carbon footprint. Facilities often find that even making basic changes in this area not only will reduce their carbon footprint, but also will often yield a return on investment in less than two years.
In sustainability practices, carbon footprinting is an important metric that will highlight the greatest areas of concern, where improvements might be achieved and might determine long-term trends. Progressive businesses are using carbon footprint figures in their decision-making process as they choose future products and services. Getting started can be challenging, but with detailed notes and a step-by-step process, the task certainly is achievable.
Reducing carbon footprint through UV/EB technology
As sustainability encompasses the entire supply chain, printers, for example, will turn to their ink and coating suppliers to lower their GHG emissions. Printers will ask about the contribution the particular inks they use make to their carbon footprint. In fact, programs like the Sustainable Green Printing Partnership (see page 5) require printers to calculate their carbon footprints and maintain an open dialog with suppliers to promote continuous improvement.
Whether the end user is a printer or coater, there are opportunities to reduce a carbon footprint in all three scopes. Here are just a few examples.
Scope 1 – Emissions example
UV/EB has the potential to reduce Scope 1 emissions. According to (Ross 2007), UV/EB technology can reduce volatile organic compound (VOC) and GHG emissions in the flooring industry. He also stated that the energy to dry a UV/EB coating is much lower than that of a conventional solvent or waterborne coating. As there is no use of natural gas to cure UV/EB formulations, combustion of natural gas for drying is eliminated from the carbon footprint equation. Natural gas is mainly methane (CH4) and – even though it is cleaner than oil, gasoline or coal – it does convert to CO2 when burned. In the combustion process, almost all of the carbon in the natural gas is converted to CO2. Due to impurities present during the natural gas refining process, traces of sulfur, nitrogen and other hydrocarbons also are emitted when natural gas is burned.
But there is a second source of carbon emissions in the oxidation process besides the natural gas combustion (Monteleone 2011). The actual combustion of the solvents that are volatile organic compounds (VOCs), often are overlooked as another source of CO2. VOC combustion can be expressed as follows: VOC + oxygen (O2) in the presence of heat creates water (H2O) and CO2. By comparison, when UV/EB is used instead of a solvent system, not only is the CO2 from the natural gas combustion eliminated, but the CO2 from oxidation of solvents is eliminated as well. Although there may be VOCs in some UV/EB formulations, it is typically not a high enough concentration to warrant combustion.
To calculate the amount of CO2 emitted from natural gas combustion, determine how much was used in 1 CCF (100 cubic feet) of natural gas. Natural gas combustion yields 12.012 lbs of CO2 per CCF. Multiply 12.012 lbs by the number of CCF consumed annually and divide by 2,204.62 to calculate metric tons of CO2. (Source: US Department of Energy 1605(b) Voluntary Reporting of Greenhouse Gases Program, eia.gov/oiaf/1605/coefficients.html)
Usage (CCF) x (12.012 lbs CO2/CCF) / 2,204.62 lbs/metric ton = CO2 emissions (metric ton)
For example, if a dryer uses 12,424 CCF of natural gas.
12,424 CCF x (12.012 lbs CO2/CCF) / 2,204.62 lbs/metric ton = 67.69 metric tons CO2
Then again, natural gas combustion is only part of the Scope 1 emissions as oxidation of the solvents (VOCs) emits CO2 as well. Depending on the type of VOC being used, such as n-propyl alcohol or n-propyl acetate, the amount of CO2 being generated per molecule of VOC would be different. For example, in the case of oxidation of n-propyl alcohol – C3H8O – the oxidation reaction would be
2C3H8O + 9O2 –> 6CO2 + 8H2O
So, for every two molecules of n-propyl alcohol, six molecules of CO2 are emitted.
Emission conversion factors by weight for solvents used by flexographic printers range from 2.0-2.2 (Monteleone 2011). The calculation of a carbon footprint from VOC oxidation would be as follows:
Usage (VOC Combusted in US tons) x 2.1 average emission factor x 0.907 metric tons/US ton = CO2 Emissions (metric tons).
For example, if a facility oxidizes 10 tons of VOCs: Using an average conversion factor of 2.1, it would generate approximately 21 tons of CO2. To convert US tons to metric tons, the number is multiplied by 0.907 metric tons/US ton, which equals 19.05 metric tons of CO2.
10 US tons of VOC x 2.1 x 0.907 metric tons /US ton = 19.05 metric tons of CO2.
By eliminating both the use of natural gas and the oxidation of a solvent, UV/EB can reduce a facilitys Scope 1 carbon footprint.
Scope 2 – Footprint example
Another major area in which UV/EB can reduce a carbon footprint is by reducing the use of electricity contributing to Scope 2 emissions. Depending on the fuel source for the local utility, the conversion factor from kilowatt hours (kWh) to carbon footprint varies considerably. Of the most common fossil fuels used, coal combustion results in greater amounts of CO2 emissions per unit of electricity generated, while oil produces less and natural gas produces the least. Emissions of CO2 and CO2e from CH4 and N2O are included in Scope 2, so it is necessary to know how much of each gas is generated from the production of one kilowatt hour of electricity by the local utility.
The US Environmental Protection Agency (US EPA) posts regional conversion factors online for each of the GHGs being emitted by utilities on the Emissions & Generation Resource Integrated Database (eGRID) webpage. The agencys most recent eGRID emission factors are from 2010 and are based on the mix of electricity fuel sources used in a particular region of the country. These factors are included in the calculation of total carbon emission in metric tons. Although many companies use eGRID emission factors, they are expressed only regionally. More accurate information may be available from the local utility and is sometimes indicated on a utility bill.
To calculate total carbon emissions for Scope 2, all GHGs must be expressed as CO2 (or CO2e) using the emission factors provided by the utility or eGrid for CO2, CH4 and N2O) and the global warming potential (GWP) for each of them as follows:
Usage (kWh) × CO2 emission factor (lbs CO2/kWh) / 2204.62 lbs/metric ton +
(Usage (kWh) × CH4 emission factor (lbs CH4/kWh) / 2204.62 lbs/metric ton) × 21 GWP +
(Usage (kWh) × N2O emission factor (lbs CH4/kWh) / 2204.62 lbs/metric ton) × 310 GWP = CO2e Emissions (metric tons).
It has been well documented that UV/EB curing uses less electricity than traditional systems. Following a review of the electricity use studies of several reports on UV/EB, (Golden 2012) noted that thermal-curing energy requirements were found to be five to nine times higher than UV/EB curing in the same process. Similarly, the difference in the carbon emissions would be five to nine times.
Scope 3 – Footprint example
As carbon emissions from transportation are included in Scope 3 of a carbon footprint, any minimization of the use of combustion of fuel that can be attributed to using UV/EB can be considered. In other words, if a UV/EB supplier can make the case of reduced transportation compared to other ink systems, there would be a parallel carbon footprint reduction for the end user. Whether it is an overall lighter weight, smaller volume or closer distance, the reduced use of fossil fuel to transport the ink or coating to the end user results in a reduced carbon footprint for that aspect.
The sustainability benefits for end users positions UV/EB for continued growth in a world where sustainability is not just a good business practice, but is expected. Depending on the formulation, UV/EB formulations have the ability to significantly reduce all three scopes of an end users carbon footprint calculation. The magnitude of these reductions will depend on the resins and solvents in the UV/EB formulation. Except for the 100 percent solid formulation, some UV/EB inks and coatings may contain VOC solvents and water that must be evaporated, but often not requiring an oxidizer for combustion. All of these aspects must be considered when making sustainable business decisions to modify ink or coating systems. Detailed records are a must to demonstrate where UV/EB provides these benefits. The reduction in use of electricity, natural gas or fuel, plus conversion factors to CO2 and CO2e, must be included in any report to validate the sustainability advantages UV/EB has for end users. In that way, UV/EB can make its case as providing a sustainable link in the supply chain.
Golden, R. 2012. Whats the Score? A Method for Quantitative Estimation for Energy Use and Emission Reductions for UV/EB Curing. RadTech Report, Issue 3.
Monteleone, D.M. 2011. Calculating Your Facilitys Carbon Footprint. Scope 1 Direct Emissions. FLEXO Magazine, October. pp. 91-94.
Ross, J.S. 2007. UV & EB in the Flooring Industry – Reducing Greenhouse Gas Emissions & HAPs. RadTech Report, July/August.