For the first time, both life cycle impact and health hazard data are integrated into an open database.
The Quartz Project was founded on the idea that transparency and open access to data are critical for true market transformation of the building products industry. The purpose of the Common Products database is to be an educational and actionable source of information for those who are looking to more deeply understand the human health and environmental implications of common building products on the market. By providing this data in a transparent, and accessible manner, we hope to encourage innovation in the tools and processes that impact the design of buildings and the products that constitute them.
Quartz Common Product Profiles are common representations of building products based off of numerous respected sources—including patents, the Pharos Project database, Environmental Product Declarations, and GaBi databases. These profiles are not endorsed by product manufacturers. Real manufactured products vary widely between manufacturers with respect to product formulations, raw materials sourcing, manufacturing processes, etc. Only a fraction of product categories have been reviewed and included in the current database. If there is a product you would like to see in the database, please write to us at firstname.lastname@example.org.
Common Product data is best used as benchmarks to represent generic products and should not be used as a replacement for manufacturer literature and technical documentation. The methodology by which discrete quantities, components and chemicals have been included in each profile is documented below. Our methodology is rigorous, consistent, and most importantly, transparent. This work is licensed under a Creative Commons Attribution 4.0 International License.
Investigating and Creating Common Product Profiles
Each of the Common Product Profiles (CPPs) within our database includes three components:
- A definition that describes the generic, non-manufacturer-specific composition and use of the product, researched and compiled by HBN
- A Health Hazard Screening that describes the aggregated human health impacts of the product’s composition, compiled by HBN through the Pharos Project database
- An ISO 14040 Life Cycle Assessment (LCA) that describes the environmental impact analysis of the product, scoped by thinkstep
- The details of these three components are described below.
Common Product Definition
Every Common Product Profile Definition includes the following fields:
Table 1: Parts of a Common Product definition
|Name||The most common way of referring to the CP|
|Synonyms||Any known alternatives to the name|
|Description||A summary of the product information, such as the composition, how the product is made and/or installed, key environmental or human health attributes, and/or any assumptions made in defining the CP, as well as references to relevant standards (ASTM, ANSI, etc.) used in determining the boundaries of the product’s content|
|Declared unit||A baseline unit (usually in weight, i.e., 1 kg)|
|Production composition||A functional list of the product components (intended ingredients and unintended residuals or contaminants) with the associated information when applicable: CASRN, percent weight within overall product, function or role within the product, sources (citations), and additional notes|
Sources of Information
A combination of publicly available documents were used to inform the composition of each Common Product. These documents include, but are not limited to, trade association documents, Environmental Product Declarations (EPDs), Life Cycle Assessments (LCAs), Health Product Declarations (HPDs), patents, Material Safety Data Sheets (MSDSs), technical product documents, and documents provided by government, academic, and other authoritative institutions. Because product compositions change frequently, recent sources were preferred over older sources.
Investigating Product Composition
The Common Product database contains a “generic” composition for each CP, as opposed to a manufacturer-specific composition or an aggregation of all possible contents used across manufacturers. The most common material or substance for a given function is included, and the proportional allocation of each material or substance is based upon actual formulations in the marketplace to ensure the “generic” compositions represent functional products.
The vocabulary used for describing different components of a Common Product are consistent with terms used in existing standards and assessments, as identified by the Material Health Harmonization Task Group. Read more about their findings in their Material Health Evaluation Programs Harmonization Update report (April 2015).
Contents are only included in the Common Product Profile if they meet the following disclosure thresholds:
- Homogeneous materials are included if present in quantities > 0.01% (100ppm) of the overall product mass AND cited in two or more sources. If a material is listed in a trade association document or other source that represents more than one manufacturer, the material is eligible for inclusion in the Common Product Profile without additional sources.
- Chemical substances are included if present in quantities > 0.01% (100ppm) of the material’s mass. The same sourcing requirements apply as for homogeneous materials.
Contents below these thresholds are included if they are hazardous (see Section Common Product Health Hazard Screening below for description) AND either:
- Exceed an established regulatory or other authoritative threshold for presenting a health hazard OR
- Are asthmagens (respiratory health endpoint), carcinogens, or persistent bioaccumulative toxicants (PBT) OR
- Contain impurities that are asthmagens, carcinogens or PBTs.
The mass percentage of each material or substance is derived by taking a median of the quantities identified across all sources. If the sum of the median percentages does not equal 100%, the percentages are normalized to total 100%, keeping the individual substance percentages within the range reported in the literature.
Composition is determined for each product based on its state as delivered to the job site; for example, paint applied on-site is characterized in its liquid state.
Capturing High Concern Impurities
The CPPs also capture unintentional content when appropriate, as dictated by the following methodology:
All impurities, including residuals from processing and contaminants from raw materials, are identified using Life Cycle Research as reported in the Pharos Chemical and Material Library (CML) or other sources. The Life Cycle Research looks at substances used in or produced during the manufacturing process, including reactants, catalysts, solvents, by-products, and process aids, as well as contaminants or pollutants commonly found in the materials or substances.
An impurity is reported in the CPP if it has a health hazard not already covered by the associated substance (see Health Hazard Screening of Common Products below for more information). If an impurity is already captured as intentional content in the CPP, then it is not listed as an impurity.
Mass percentages for impurities within the product are quantified if data is available. Quantities come from (a) aggregated data provided by industry trade associations or government authorities, or (b) a minimum of two independent sources. Otherwise, the mass percentage is listed as “unknown”. Once quantified, the same threshold rules apply for the inclusion of impurities as for the intentional content detailed above.
Lack of Disclosure
Sometimes publicly available sources are insufficient for identifying discrete materials or substances beyond a general description. In such cases, a proxy material or substance is reported that matches the function of the unspecified content. For example, public information about coatings applied to the interior of sprinkler pipes describe them as “epoxy” with no further specificity. A CPP for a general epoxy high-performance coating was used as the proxy for what might be used specifically in sprinkler pipes.
Lack of disclosure often occurs with polymers, whose identities are sometimes held as proprietary and only referenced using a general name within the product literature. In such cases, the identity of a given polymer is determined from patent information if possible. Patents often provide a formulation of ingredients that are reacted to form the finished polymer and can be used to identify common reactants. These common reactants are listed as impurities if they pose a hazard not already captured by the polymer. In addition, if the mass percentage of a polymer within a product is not available, it is estimated by adding the mass percentages of its reactants (such as monomers and crosslinkers) within the product. If the polymer’s specific name or CASRN cannot be identified, it is listed by its general name without a CASRN and “unknown” health hazards.
When no common reactants are known but a representative polymer is identified (i.e., no specific polymer is identified as common, but one source references the CASRN), the polymer is listed by its general name with the CASRN, hazards, and residuals of the representative polymer.
When no common reactants are known and no representative CASRN is identified, the polymer is listed by its general name without a CASRN. No residual information is included unless it is available from product literature. The health hazard is listed as “unknown”.
All content included in the CPP is appropriately cited with a list of sources from which the information was derived. Additional sources that contributed to defining the functional unit or any other part of the Profile are also cited.
Common Product Health Hazard Screening
About Health Hazard Screening
A variety of state, national, and international governmental bodies and non-governmental organizations (NGOs) maintain authoritative chemical hazard lists. These are lists of substances for which an authoritative body of scientists has undertaken a systematic review of scientific evidence and categorized the substances as having an association with a specific health hazard. There is currently no single, comprehensive authoritative list or database that assesses and rates all chemicals across all human health hazard endpoints. The Pharos CML begins to address this problem by combining many single hazard endpoint lists into one combined database that provides a view across multiple endpoints.
Health Hazard Screening of Common Products
Health hazard data from the Pharos CML were used to screen the chemical substances within the CPPs to determine if the substances have been associated with a health concern by an authoritative body. 35 authoritative hazard lists from the Pharos CML, including the entire GreenScreen List Translator set of lists, were referenced for CPP hazard screening. The screening does not include a risk or exposure assessment. If, however, the hazard screening designates the hazard as occupational, this is indicated. Non- or indirect human health hazards, such as ozone depletion or aquatic toxicity, are not included.
Hazards associated with a particular substance are indicated by a priority level (the orange, red, and purple color codes noted in the CPPs; based on Pharos CML classification) and human health endpoint (such as cancer or reproductive). The orange and red priority levels are based upon criteria developed for the top two levels of the GreenScreen benchmarking system (benchmark 1 - red and benchmark 2 - orange). The Pharos system further subdivides the red category into red and purple to differentiate persistent, bioaccumulative toxicants (PBTs) as worst case actors. The descriptions of the priority levels are as follows:
Table 2: : List of health hazard priority levels and descriptions
|Purple||Urgent concern to avoid||Material of urgent concern due to combinations of known high persistence, bioaccumulation and toxicity. PBT substances flagged purple do not break down rapidly in the environment into more benign substances and therefore accumulate and concentrate as they work up the food chain.|
|Red||Very high concern to avoid||Material of very high concern, identified as known or likely to lead to priority human health effects - defined as a high hazard of the GreenScreen Group I Human hazard endpoints.|
|Orange||High concern to avoid||Material of high concern due to possible association with priority human health effects or high potency for other acute or chronic human health effects.|
Health endpoints included in Common Product data are:
Table 3: List of health endpoints and descriptions
|Pharos endpoint||GreenScreen endpoint||Description|
|PBT||Persistent Bioaccumulative Toxicant||Does not break down readily from natural processes, accumulates in organisms, concentrating as it moves up the food chain, and is harmful in small quantities.|
|Cancer||Carcinogenicity||Can induce cancer or increase its incidence.|
|Cancer (occupational)||Carcinogenicity||Can induce cancer or increase its incidence when inhaled in forms and quantities generally only occurring in occupational settings.|
|Developmental||Developmental Toxicity||Can cause harm to a developing child, including birth defects, low birth weight, and biological or behavioral problems that appear as the child grows.|
|Reproductive||Reproductive Toxicity||Can disrupt the male or female reproductive systems, changing sexual development, behavior or functions, decreasing fertility, or resulting in loss of a fetus during pregnancy.|
|Endocrine||Endocrine Activity||Can interfere with hormone communication between cells which controls metabolism, development, growth, reproduction, and behavior (the endocrine system).|
|Mutagenicity||Mutagenicity/ Genotoxicity||Can cause or increase the rate of mutations, which are changes in the genetic material in cells.|
|Respiratory||Respiratory Sensitization||Can lead to hypersensitivity of the airways following inhalation of the substance.|
|Respiratory (occupational)||Respiratory Sensitization||Can lead to hypersensitivity of the airways following inhalation in forms and quantities generally only occurring in occupational settings.|
|Neurotoxicity||Neurotoxicity||Can cause damage to the nervous system, including the brain.|
|Mammalian||Acute Mammalian Toxicity||Can be fatal on contact or ingestion for humans and other mammals.|
|Eye Irritation||Eye Irritation/ Corrosivity||Can cause irritation or serious damage to the eye.|
|Skin Irritation||Skin Irritation/ Corrosivity||Can cause irritation or serious damage to the skin.|
|Skin Sensitization||Skin Sensitization||Can trigger allergic reactions on the skin.|
|Organ Toxicant||Systemic Toxicity/ Organ Effects||Can cause serious damage on contact or ingestion, includes immunotoxicity-repeated exposure.|
See the methodology for Pharos flags and Hazard warnings for a full description and the authoritative lists and governing bodies responsible for Hazard warnings in the CPPs.
Common Product LCA Data
About Life Cycle Assessment (LCA)
Life Cycle Assessment (LCA) is a scientific technique for assessing the potential environmental impacts associated with a product (or service). It has emerged as a valuable decision support tool in helping policy makers and industry professionals better understand environmental impacts associated with their activities. A life cycle assessment study focuses on the stages of product life cycle, for example from cradle-to-gate or cradle-to-grave. More commonly, these stages are thought of as material extraction, processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. LCA encourages interdisciplinary thinking and incorporation of broad environmental concerns by providing environmental data needed for robust decision-making.
There are four linked components of LCA according to ISO 14040:
- Goal definition and scoping: identifying the LCA's purpose and the expected products of the study, and determining the boundaries (what is and is not included in the study) and assumptions, based upon the goal definition;
- Life cycle inventory: quantifying the energy and raw material inputs and environmental releases associated with each stage of production;
- Impact analysis: assessing the impacts on human health and the environment associated with energy and raw material inputs and environmental releases quantified by the life cycle inventory;
- Interpretation: evaluating opportunities to reduce energy, material inputs, or environmental impacts at each stage of the product life cycle.
While the results of a LCA study highlight many environmental factors, the Quartz project focuses on the following six.
- Global Warming Potential
- Ozone Depletion Potential
- Primary Energy Demand
- Acidification Potential
- Eutrophication Potential
- Smog Formation Potential
See Impact Assessment Methodology for more information on how these environmental impacts are measured and what they mean.
Following ISO standards, LCA is underpinned by a rigorous scientific and technical foundation. This enables decisions to be taken based on facts, backed by data derived over many years of industrial, scientific, and academic research.
Goal and Scope
The system boundary of the analysis is cradle-to-gate + end-of-life (EoL), based on LCA standard language and using LCA methodology. It includes raw material production, inbound transportation, manufacturing, and disposal/recycling processes. Installation, use, and maintenance phases are not considered; materials are modeled as ready for delivery to the construction site at the final factory gate. The exception to this boundary are products that use a physical or chemical blowing agent or are site-applied adhesives, sealants, coatings, and paints. For these products, the boundaries include emissions from off-gassing and drying that occur during on-site application and over the life of the installed product.
Ancillary materials are not included unless they are part of the material formulation. For example, blowing agents are included as a material component of the spray foam insulation formulation, so upstream data for these chemicals are included. Materials, such as staples, would not be considered part of the product formulation if they are applied on-site.
Table 4: System Boundary for LCA studies
This Common Products database uses a declared unit to establish the reference against which the environmental indicators are measured. The declared unit for all CPPs is one kilogram (1 kg). The functional unit of a particular CPP will depend on where and how it is installed in a building. A declared unit is used instead of a functional unit because the exact function, quantity, duration, and quality of the product within the building are unknown, and the installation and use phases of the life cycle are omitted.
The data used to create the inventory model are as complete, consistent, and representative as possible with regards to the goal and scope of the study.
- “Completeness” is judged based on the completeness of the data on the inputs and outputs per unit process and the completeness of the data on the unit processes themselves. As discussed below, no cut-off criteria are defined for this study.
- “Consistency” refers to modeling choices and data sources. The goal is to ensure that differences in results occur due to actual differences between product systems, and not due to inconsistencies in modeling choices, data sources, emission factors, etc.
- “Representativeness” expresses the degree to which the data match the geographical, temporal, and technological requirements defined in the study’s goal and scope.
The LCA models are intended to be representative of the year 2015. Formulations within each CPP are for products common in their respective industries in 2015. Background data for upstream and downstream processes are obtained from the GaBi 2014 databases and are intended to represent the year 2015. Data from the GaBi 2014 database reference years 2009-2013. Third-party datasets may fall outside this range, such as worldsteel (2007) and NAIMA (2007), due to lack of more recent datasets from these sources.
The study is intended to represent current technologies common to the products’ respective industries. For all ancillary or process materials not specific to the product’s manufacturing processes, generic inventories from the GaBi 2014 database are used.
The CPs are representations of typical material compositions and manufacturing processes of building and construction products sold in the US. CPs were modeled using the following hierarchy:
- US industry-average life cycle inventory (LCI) dataset representative of similar ingredients and technology, as defined in the CP, and calculated using primary data from multiple manufacturers.
- Product composition modeled distinctly, with some proxy data use, and manufacturing data obtained from the GaBi database or literature research.
- Aggregated composition and manufacturing data available through an existing GaBi dataset.
The geographical boundary of the project is the United States (US). All upstream materials are assumed to be produced in the US. Where a product is not produced in the US, it is modeled using conditions representative of the country of production and includes initial transportation to the US, though further distribution within the US or to site is excluded. This caveat currently only applies to bamboo and linoleum flooring, which are manufactured in China and Europe, respectively. All downstream production steps are modeled under US conditions.
Where US background data is not available, global or European data are used as proxies. Where a proxy dataset contributes a significant portion of the mass or the impact (approximately 10%), the dataset is updated with US-specific background data.
Completeness and Consistency
No primary data are collected for the CPs, instead the literature sources listed for each CP are used. Each foreground process is checked for mass balance and completeness of the emission inventory. No data are knowingly omitted. All background data are sourced from GaBi databases with the documented completeness. To ensure data consistency, all foreground manufacturing data are modelled with the same level of detail, while all background data are sourced from the GaBi databases.
Allocation is required when a process or system produces multiple co-products. The inputs and outputs must be divided between the co-products in order to accurately calculate the environmental impact attributed to each co-product. ISO 14040/44 specifies that a physical relationship (e.g., mass, volume, or energy) should first be considered as the basis by which to divide the process or system inputs and outputs. If the physical relationship is not suitable for the process, another method, such as economic allocation, may be used instead.
No allocation decisions have been directly applied to the foreground modelling. Background data use allocation relevant to the system under study and are available on the GaBi 6 website.
Cut-off Criteria (Disclosure)
“Cut-off criteria” refers to the point at which an input or output would be deemed insignificant to the overall LCA and therefore can be excluded. It is defined by the level of contribution to the overall mass, energy, or environmental impact, e.g., anything less than 1% mass can be excluded if the total of excluded flows is not greater than 5%.
No cut-off criteria are explicitly defined for the LCA portion of this database. All available energy and material flow data are included in the model. In cases where no suitable matching life cycle inventories are available to represent a flow, proxy data are applied based on conservative assumptions regarding environmental impacts.
End-of-life (EoL) treatment is based on average United States construction and demolition waste treatment methods and rates. This includes the relevant material collection rates for recycling, processing requirements for recycled materials, incineration rates, and landfilling rates. The specific methods for each product category group are detailed in End-of-Life Data Sources section below.
For metals that are recycled, the avoided burden approach is used for modeling, where part of the burden of primary material production is allocated to the subsequent life cycle based on the quantity of recovered secondary material resulting in an environmental credit at EoL, as pictured in Figure 2. A ‘net scrap’ approach is applied during modeling where the scrap sent to recycling at EoL is first balanced out with the scrap input into the initial manufacturing. The remaining net scrap is then sent to recycling and given credit for use in subsequent production systems. Where the scrap sent to recycling at EoL is less than the scrap input required during manufacturing of the product, a burden for the difference in scrap is assigned to the initial manufacturing that corresponds to the negative of the avoided burden, i.e., the burden of primary material minus the burden of recycling.
For all other materials that are recycled, the cut-off approach is used, where the burden of the primary production is attributed to the first life cycle and the burden associated with secondary material recovery and refining is attributed to the subsequent life cycle, as pictured in Figure 3. Therefore, no primary burden is assigned for the use of a recycled material and no credit is given for recycling a material.
Under the cut-off approach, no burdens associated with landfilling and incineration of materials are attributed to the first life cycle and no credits for energy recovery are given. The impacts associated with landfilling are based on average material properties, such as plastic waste, biodegradable waste, or inert material. The End-of-Life Data Sources section contains details on EoL data and assumptions for various CPs.
Applying different EoL allocation approaches to metal and non-metal products introduces a certain bias into the comparison between such products. While this cannot be completely eliminated, the bias is estimated to be minimal for the following reasons:
- Non-metal products such as concrete (55% recycling rate) and non-pressure-treated wood (17.5% recycling rate) from construction wastes are not easy to recycle and usually experience significant levels of downcycling, and the avoided burden would be low compared to their primary burden.
- For the other non-metal products, recycling rates are well below 10% (see End-of-Life Data Sources section), so the choice of EoL allocation approach does not materially affect the overall impact profile.
- Likewise, incineration with energy recovery is rarely used for construction wastes in the US, with 17.5% of the non-pressure-treated wood and 2.2% of the carpet modeled as incinerated at EoL.
- All other non-metal materials are sent to landfill.
Impact Assessment Methodology
A set of impact assessment categories and other metrics considered to be of high relevance to the goals of the project are shown in Table 2 and Table 3. The US EPA’s TRACI 2.1 (Tool for the Reduction and Assessment of Chemical and other environmental Impacts) was selected as it is currently the only impact assessment methodology framework that incorporates US average conditions to establish characterization factors. However, the most recent global warming characterization factors from the Intergovernmental Panel on Climate Change (IPCC) have been used instead of the TRACI 2.1 factors, which are out of date.
Table 5: Descriptions of Life Cycle Impacts included in LCA studies
|Global Warming Potential (GWP), including biogenic carbon||A measure of greenhouse gas emissions, such as CO2 and methane. These emissions are causing an increase in the absorption of radiation emitted by the earth, increasing the natural greenhouse effect. This may in turn have adverse impacts on ecosystem health, human health, and material welfare.||kg CO2 equivalent||(IPCC, 2013)|
|Eutrophication Potential (EP)||“Eutrophication” covers all potential impacts of excessively high levels of macronutrients, the most important of which are nitrogen (N) and phosphorus (P). Nutrient enrichment may cause an undesirable shift in species composition and elevated biomass production in both aquatic and terrestrial ecosystems. In aquatic ecosystems, increased biomass production may lead to depressed oxygen levels because of the additional consumption of oxygen in biomass decomposition.||kg N equivalent||(Bare, 2012) (EPA, 2012)|
|Acidification Potential (AP)||A measure of emissions that cause acidifying effects to the environment. The acidification potential is a measure of a molecule’s capacity to increase the hydrogen ion (H+) concentration in the presence of water, thus decreasing the pH value. Potential effects include fish mortality, forest decline, and the deterioration of building materials.||kg SO2 equivalent||(Bare, 2012) (EPA, 2012)|
|Smog Formation Potential (SFP)||A measure of emissions of precursors that contribute to ground level smog formation (mainly ozone O3), produced by the reaction of VOC and carbon monoxide in the presence of nitrogen oxides under the influence of UV light. Ground level ozone may be injurious to human health and ecosystems, and may also damage crops.||kg O3 equivalent||(Bare, 2012) (EPA, 2012)|
|Ozone Depletion Potential (ODP)||A measure of air emissions that contribute to the depletion of the stratospheric ozone layer. Depletion of the ozone leads to higher levels of UVB ultraviolet rays reaching the earth’s surface with detrimental effects on humans and plants.||kg CFC-11 equivalent||(Bare, 2012) (EPA, 2012)|
Table 6: Additional environmental indicators included in LCA studies
|Primary Energy Demand (PED)||A measure of the total amount of primary energy extracted from the earth. PED is expressed in energy demand from non-renewable resources (e.g., petroleum, natural gas, etc.) and energy demand from renewable resources (e.g.. hydropower, wind energy, solar, etc.). Efficiencies in energy conversion (e.g., power, heat, steam, etc.) are taken into account.||MJ (lower heating value)||(Guinée, et al., 2002)|
It should be noted that the above impact categories represent impact potentials, i.e., they are approximations of environmental impacts that could occur if the emissions would (a) actually follow the underlying impact pathway and (b) meet certain conditions in the receiving environment while doing so. In addition, the inventory only captures that fraction of the total environmental load that corresponds to the declared unit (relative approach).
LCA results are therefore relative expressions only and do not predict actual impacts, the exceeding of thresholds, safety margins, or risks.
The LCA model is created using the GaBi 6 Software system for life cycle engineering, developed by thinkstep. The GaBi 2014 LCI database provides the life cycle inventory data for the majority of the raw and processed materials obtained from the background system.
Data Source Decisions by Life Cycle Stage
Each CPP includes a summary of the product’s common use, manufacturing and installation route, composition with CASRN, and each material’s or substance’s function or role in the product. Products and their composition are modeled explicitly and annotated in the “LCA?” column of the CPP General Composition section with a “yes”. This column will read “no” when the LCA deviates from the listed composition. This only occurs when a reliable and compatible industry-average or aggregated generic LCA dataset (which includes components, quantities and manufacturing routes) already exists.
Best available data that are most representative of US production conditions are used to model the manufacturing processes for the common products. The preferred data source for manufacturing energy exists within an aggregated industry-average dataset available in the GaBi 6 database. If this is not available for a common product, then manufacturing data is taken from one of the following sources, listed in order of preference:
- Generic manufacturing processes within the GaBi database not based on industry-average data
- Published LCA studies
- Proxy based on similar production technologies
- Patents, aligned with sources for common products methodology
- Ullmann’s Encyclopedia of Industrial Chemistry
When data are not available for products that require mixing, a 0.5 MJ/kg mixing energy was assumed. This is a rule-of-thumb estimate used in the absence of product-specific mixing energy, based on thinkstep’s industry experience.
There are no assumptions made about the inclusion of cooling or other process water, and process water is only included when data are directly available.
Unless more complete data are available, it is assumed that 2% of the solvents used for manufacturing evaporate and the remaining solvent is reused. As the recycling of solvents is often internal, the recovered solvent is assumed to be reused within the product manufacturing process to offset inputs of the primary solvent. Data on the energy required to recover the solvent are unavailable and therefore not included, though it is expected that the burden would be small compared to the total.
When a manufacturing step can take place either at the manufacturing facility or on-site, it is assumed that the step takes place at the manufacturing facility and is included in the cradle-to-gate model [e.g., application of High performance coating (epoxy)].
In the case of polymers, when common reactants and process chemicals are identified, all are modelled, including solvents, catalysts, and cross-linkers. As discussed previously, the CP composition only includes the substances that would be present in the final product and the masses of all reactants are scaled to the mass of the declared unit of the final product.
Where a specific CASRN is identified for a polymer in the CP definition, the polymer is modeled with best available data. If the exact polymer is not available in the GaBi 6 database, the polymer is modeled using a proxy from the same class of polymers. For example, High performance coatings (acrylic) references ‘2-Propenoic acid, polymer with butyl 2-propenoate and ethenylbenzene’ but is modeled as ‘styrene butylacrylate copolymer’.
Unidentified polymers, where the polymer used in formulations is proprietary and only a generic polymer description is available, are modeled as follows:
- Where common reactants are identified and the ingredients and mass percentages match a dataset for a polymer in the same class available in the GaBi 6 database, the GaBi dataset is used to model that polymer
- Where common reactants are identified and a GaBi 6 dataset is available for a polymer in the same class, but the ingredients and mass percentages in this dataset do not match those identified in the CP research, the information from the CP research is used and manufacturing data is approximated from the GaBi 6 dataset for the polymer in that class
- Where common reactants are identified and there is no GaBi dataset available for a polymer in the same class, the polymer is modeled using the reactants identified in the CP research with a mixing energy of 0.5 MJ/kg
- Where no common reactants or polymer CASRN is identified and a generic polymer name is used, the polymer is modeled with a worst-case proxy (high environmental impact) from that polymer class.
Installation / Use
To inform the amount of blowing agent remaining in the insulation at EoL, and thus the mass of product to be disposed of, release profiles of blowing agents during use and EoL are obtained from the EPA’s report on foam emissions. For all CPPs under consideration for this work, 100% of the blowing agents incorporated in the products are released during the installation and use phases.
The percentage of VOCs within each common product is determined using the median of reported values for actual VOCs (g/L) and the median reported product density. All VOCs released during installation or use are modeled as unspecified non-methane VOCs (NMVOCs). Additionally, any water in the product is assumed to be released as vapor before EoL.
The EoL scenario modeled always aligns with the CP definition. For example, the percent of biodegradable or plastic material sent to landfill is calculated based on percent of plastic material specified in the CP definition. The table below discusses the EoL treatment for each category of product. As discussed previously, the burdens for recycling are cut-off unless otherwise stated.
Table 7: End-of-life treatments grouped by product category
|Product Category||End-of-Life Treatment|
Concrete can be recycled into aggregate or general fill material. The EPA estimates that 50-60% of all concrete is recovered, while the rest is landfilled. It is assumed that 55% of concrete is recycled.
It is assumed that 100% of drywall is landfilled. While gypsum in drywall can be recovered and used as a secondary material input for drywall or as an agricultural supplement, drywall from building demolition at EoL is often contaminated and therefore rarely recycled. The majority of recovered gypsum comes from new construction waste and, therefore, is not included in the system boundary.
|Granular Fill||Granular fill can be reused as fill without further processing. There is currently a lack of data on the recycling rates of granular fill, so it is assumed that the recycling rate is equal to the recycled content, 50%, as specified in the CP.|
|Mineral Wool||It is assumed that all mineral wool is landfilled at the end of the building’s life. While mineral wool often uses large amounts of recycled materials as part of the formulation, diverting waste material from landfills, it is not commonly recycled at EoL. Source|
|Grouts, Sealants, and Mortars||These products are assumed to be landfilled, as this is the disposal route for the majority of demolition waste in the US. Source|
|Metals||Recycling of metal products is modeled using the avoided burden approach. At EoL, the recycling rate of the metal is used to determine how much secondary metal can be recovered, after having subtracted any scrap input from manufacturing (net scrap). This manifests itself as an environmental credit for a corresponding share of the primary burden, which can be allocated to the subsequent product system that uses the secondary material as an input. Metals not recycled are sent to landfill. Recycling rates by metal:|
|Wood||Wood products are modeled using the cut-off approach. Burdens for recycling and credit for landfill or incineration of any wood-based products are not included. The referenced report found that 48% of wood waste is available for recovery, but recycling is not common in practice. Therefore, it is assumed that this portion of the waste stream is sent to landfill. The remaining 52% is “recovered, combusted, [or] not usable” (sent to landfill). It is assumed that these three pathways are equally likely, and so wood EoL is modeled with 65.5% sent to landfill, 17.5% to incineration and 17.5% to recovery. This split is applied for all wood products, with the exception of pressure-treated lumber. Pressure-treated lumber cannot be incinerated and should not be turned into chips or sawdust for mulch due to the presence of preservatives. Therefore it is assumed that 100% is landfilled. See section below on biogenic carbon. Source|
|Plastics||The majority of plastics in the United States are not recycled, with an average recycling rate of 9% in 2013 (for municipal solid waste). In addition, the inclusion of some additives, such as flame retardants, may negatively affect recyclability. Lastly, current literature available on plastic recycling refers mainly to food and beverage containers, and does not reference plastics used in the construction industry. Therefore, a worst-case scenario of 100% to landfill is assumed for all plastic-based materials.|
|Window Glass||Window glass is not currently recycled into new window glass. It can be downcycled into lower-quality glass products, however data on the rate of downcycling are currently unavailable. Therefore, 100% of window glass is assumed to be landfilled. Source|
|Fiberglass||100% of fiberglass is assumed to be landfilled. Source|
|Coatings, Sealants, and Paints||Certain materials typically function as ancillary materials to a larger assembly. These primarily include sealants, coatings, and paints. Specific cases are discussed in the following sub-sections.|
|Concrete Supporting Materials||Products that are readily separated from the concrete, such as plastic films, are sent to landfill. Liquid applied products that are bound to the concrete, such as a sealant, are considered to be recycled with the concrete and have the same recycling rate.|
|Solvents||It is assumed that solvent components of common products evaporate during the use phase. Therefore there are no impacts associated with solvent evaporation during EoL.|
|Metal Coatings||There is no burden associated with the incineration or landfilling of coating, as the burdens associated with the incineration of an average coating are included in the metal recycling processes.|
|Heterogeneous Assemblies||The EoL of heterogeneous assemblies—products composed of materials that can be easily separated—is modeled using the appropriate methodologies for the component materials as described above.|
The biogenic carbon innate in wood products is accounted for at EoL, assuming 50% carbon content by mass of the wood fraction of the formulation, and neglecting the variable moisture content. As modeled in the landfill dataset, and consistent with the US EPA’s WARM tool, 98-99% of the carbon in landfilled wood is sequestered for more than 100 years, while the remainder is released as biogenic CO2 and biogenic CH4. All carbon contained in incinerated wood is released as biogenic CO2. The carbon contained in the fraction of the wood product that is sent to recycling leaves the system. This is represented by a biogenic CO2 emission and accounts for the carbon that is contained in the wood being used in the next life cycle. [Source]
As transportation can be highly variable, an estimate of 311 miles (500 km) by truck is assumed for inbound materials to manufacturing, unless specific data is available. This is a conservative estimate made by thinkstep based on industry experience.
Distance to landfilling in the United States is assumed to be 20 miles (32 km). [Source]
Given the potential variation in metal recycling locations, it is assumed the distance for metal recycling is 100 miles (161 km). The distance for concrete recycling is 31 miles (50 km). [Source]
All datasets used to model Cradle-to-Gate impacts are listed within the individual CPP. The datasets listed in Table 5 are used to model the various EoL environmental impacts.
Table 8: Datasets used for EoL modeling
|Recycling Process / Material Credit||Value of scrap||GLO||worldsteel||2007|
|Recycling Process/ Material Credit||Electrolytic copper secondary (input heavy copper scrap 95-98% Cu)||US||thinkstep||2012|
|Recycling Process||Copper mix (99,999% from electrolysis)||US||thinkstep||2013|
|Material Credit||Secondary Aluminum Ingot||US||thinkstep||2010|
|Recycling Process||Primary Aluminum Ingot||US||AA/thinkstep||2010|
|Material Credit||Landfilling of ferro metals||US||AA/thinkstep||2013|
|Landfill||Landfilling of wood products (OSB, particle board) (modified based on US EPA’s WARM tool landfill documentation)||US||thinkstep||2015|
|Landfill||Landfilling of glass/inert||US||thinkstep||2013|
|Landfill||Landfilling of paper waste||US||thinkstep||2013|
|Landfill||Landfilling of plastic waste||US||thinkstep||2013|
|Landfill||Landfilling of biodegradable waste||US||thinkstep||2013|
|Landfill||Landfilling of textiles||US||thinkstep||2013|
|Incineration||Pure wood (10% H2O content) in waste incineration plant||US||thinkstep||2013|
Bare, J. (2012). Tool for the Reduction and Assessment of Chemical and other Environmental Impacts (TRACI) - Software Name and Version Number: TRACI version 2.1 - User’s Manual. Washington, DC: US EPA.
BSI. (2012). PAS 2050-1:2012: Assessment of life cycle greenhouse gas emissions from horticultural products. London: British Standards Institute.
EPA. (2012). Tool for the Reduction and Assessment of Chemical and other Environmental Impacts (TRACI) – User’s Manual. Washington, D.: US EPA.
Frischknecht, R. (2010). LCI modelling approaches applied on recycling of materials in view of environmental sustainability, risk perception and eco-efficiency. The International Journal of Life Cycle Assessment, 15(7), 666-671.
Guinée, J. B., Gorrée, M., Heijungs, R., Huppes, G., Kleijn, R., de Koning, A., . . . Huijbregts, M. (2002). Handbook on life cycle assessment. Operational guide to the ISO standards. Dordrecht, Netherlands: Kluwer.
IPCC. (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories - Volume 4 - Agriculture, Forestry, and Other Land Use. Geneva, Switzerland: IPCC.
IPCC. (2013). Climate Change 2013: The Physical Science Basis. Geneva, Switzerland: IPCC.
ISO. (2006). ISO 14040: Environmental management – Life cycle assessment – Principles and framework. Geneva: International Organization for Standardization.
ISO. (2006). ISO 14044: Environmental management – Life cycle assessment – Requirements and guidelines. Geneva: International Organization for Standardization.
JRC. (2010). ILCD Handbook: General guide for Life Cycle Assessment – Detailed guidance. EUR 24708 EN (1st ed.). Luxembourg: Joint Research Centre.
Pfister, S., Koehler, A., & Hel, S. (2009). Assessing the Environmental Impacts of Freshwater Consumption in LCA. Environ. Sci. Technol., 43(11), 4098–4104.
Rosenbaum, R. K., Bachmann, T. M., Swirsky Gold, L., Huijbregts, M., Jolliet, O., Juraske, R., . . . Hauschild, M. Z. (2008). USEtox—the UNEP-SETAC toxicity model: recommended characterisation factors for human toxicity and freshwater ecotoxicity in life cycle impact assessment. Int J Life Cycle Assess, 13(7), 532–546.
thinkstep. (2014). GaBi LCA Database Documentation. Retrieved from thinkstep AG: http://database-documentation.gabi-software.com
van Oers, L., de Koning, A., Guinée, J. B., & Huppes, G. (2002). Abiotic resource depletion in LCA. The Hague: Ministry of Transport, Public Works and Water Management.
WRI. (2011). GHG Protocol Product Life Cycle Accounting and Reporting Standard. Washington DC: World Resource Institute.
- Avoided burden approach - The method of recycling allocation in which part of the burden of primary material production is allocated to the subsequent life cycle based on the quantity of recovered secondary material, resulting in an environmental credit at EoL.
- Background data - Upstream and downstream, generic or average life cycle inventories for the energy and materials required to calculate the life cycle inventory of the current product under study.
- CASRN - A Chemical Abstract Services Registry Number is a unique identifier assigned by the Chemical Abstract Service of the American Chemical Society to uniquely identify chemical elements, compounds, polymers, and other materials and mixtures. Frequently used in Material Safety Data Sheets (MSDSs). Also known as a “CAS number”.
Common Product Profile (CPP) - A profile of a generic, non-manufacturer-specific product that contains: 1) definition and composition based on curated, public, technical documents, 2) health hazard screen data based on the Pharos CML, and 3) LCA data (following ISO 14040 principles).
- Product - A finished good composed of parts and/or homogeneous materials. A product may function as part of another product. A product may be made of one or more homogeneous materials, which are composed of chemical substances.
- Homogeneous Material or Material - A uniform solid, liquid, or gas composed of one or more substances that cannot be mechanically disjointed, in principle.
- Chemical Substance or Substance - A substance of fixed composition, characterized by its molecular structure(s), which typically has an associated CASRN.