Measuring Results

Measuring Reductions in GHG Emissions

Ultimately, the effectiveness of any Climate Action Plan (CAP) is measured by the GHG emissions actually reduced. As the CAP is implemented, tracking and reporting progress toward achieving emissions reduction targets is critical to maintaining an effective program based on investing in activities that produce the most significant results. Similar to setting targets (discussed here), measuring results requires tools and methods to accurately estimate materials management related emission reductions.

When setting targets, you determine the GHG reduction goal for some future date, either broadly or based on specific programmatic actions. Many assumptions are involved in setting targets. When measuring results from materials management strategies, you generally gather data on materials and/or products to measure a change in practice and then estimate the associated reductions in GHG emissions using some of the same tools used to set targets.

This section focuses on how to use available tools to calculate the GHG reductions resulting from implementing materials management strategies. The tools are largely the same as those described on the "Setting Targets" page.

Methodologies for Evaluating Emissions Reductions

The same tools can be used both for setting emission reduction targets and for evaluating the emissions reductions associated with materials management activities. Many of the available tools and methods are detailed below.

What the evaluation looks like when you are estimating the actual emissions reduction resulting from programs that have been implemented, depends on whether the community has taken the “Inventory Purist Approach” or the “Inventory Pragmatist Approach” (see Setting Targets). For communities using the “Inventory Purist Approach”, where all credited GHGs must have a place in the inventory, estimating actual emissions reductions from programs is usually done as part of updating the inventory – perhaps on a regular periodic basis. For communities using the “Pragmatist Approach”, the estimating will often be a series of side calculations, performed separately from the traditional inventory.

Timing of Emission Reductions: For some materials management practices in any given year, the resulting emissions, or emissions reductions, may occur in future years. This is essential to keep in mind when working in the construct of a larger community inventory, as other emissions are reported in the years in which they actually occur. See Timing of Emissions page for additional details.

Tools for Measuring Results

Tools available for measuring the GHG emissions impacts of materials-related programs are the same as those used for setting targets. The only difference is the point at which a community is doing the calculations and the purpose of those calculations: you set your targets before you create a CAP to give direction, while measurement occurs after CAP activities have been implemented and you are ready to see how successful they've been. For this reason the tools information described below is nearly identical to the information presented on the Setting Targets page.


US EPA's WARM ToolEPA’s WAste Reduction Model (WARM) is a tool for assessing the GHG emissions of a baseline and an alternative waste management method for handling any of 26 materials and 8 mixed materials categories. WARM is the most common tool used to predict and estimate GHG emissions reductions from materials management strategies. WARM was created “to help solid waste planners and organizations track and voluntarily report greenhouse gas emissions reductions from several different waste management practices.” (From the WARM website). While WARM was not originally designed to be used as an inventory tool, it is possible to use WARM to estimate the life cycle GHG emissions and emissions reductions associated with a variety of material uses and end-of-life practices in a systems based approach – both projected (future) and actual (current). WARM is available both as a Web-based calculator and as a Microsoft Excel spreadsheet.

WARM calculates and totals GHG emissions of baseline and alternative waste management practices—source reduction, recycling, combustion, composting, and landfilling. The model calculates emissions in metric tons of carbon equivalent (MTCE), metric tons of carbon dioxide equivalent (MTCO2E), and energy units (million BTU) across 34 material types commonly found in municipal solid waste (MSW). The emission factors represent the GHG emissions associated with managing 1 short ton of MSW in a specified manner. GHG savings should be calculated by comparing the emissions associated with the alternative scenario with the emissions associated with the baseline scenario, as opposed to simply multiplying the quantity by an emission factor. Without the comparison, part of the emissions savings or cost will be excluded.

WARM is widely used by national, state, and local governments. It has become the standard for most communities for a variety of reasons -- it is easy to use, it is open source where many other tools are proprietary, and it is free to use. Because it is now so commonly used, it lends some universality and comparability to the analyses that are done with it. It is a "common denominator" for solid waste GHG emissions in the US. Furthermore, the emissions factors that underlie the WARM tool can also be useful for estimating life cycle emissions associated with certain materials. In sum, WARM is one of the best tools available for state and local governments to estimate the GHG emissions associated with prevention, recycling, and composting. WARM is not without limitations. More about WARM and its limitations is summarized here.

Environment Canada's GHG Calculator for Waste Management

Environment Canada's GHG Calculator for Waste Management is similar to and based on US EPA's WARM tool, although it uses Canadian GHG emission factors for materials commonly occurring in the Canadian waste stream. It includes anaerobic digestion among the waste management options and includes several new material types such as electronics and large appliances, also known as "white goods". Additionally, it estimates GHG emissions from provincial fuel generation through an analysis of where each step of the manufacturing process happens. The tools is available as an Excel spreadsheet that can be obtained free of charge at the link above.


The Climate and Air Pollution Planning Assistant (CAPPA) is a free Excel-based decision making tool from ICLEI-USA designed to help locals "explore, identify, and analyze potential climate and air pollution emissions reduction opportunities." The advantage of CAPPA is that it allows communities to consider options for GHG reductions over a wide range (e.g. electricity, transportation) simultaneously. Opportunities include several for materials and waste:

  • Composting (kitchen and yard waste)
  • Methane flaring at landfills
  • Recycling (expanding commercial, curbside, and construction materials recycling)
  • Waste reduction (Pay-As-You-Throw, reuse facilities)

For each option, CAPPA quantifies two types of avoided GHGs associated with the annual activity: (1) approximation of the annual landfill methane reduction and (2) avoided lifecycle emissions. Both numbers are based on WARM emission factors. Some outstanding concerns for using CAPPA relate to the current lack of methodology to address the timing of emissions (Link to this page for additional details). Specifically, the algorithm for prioritizing options for emissions reductions currently only credits recycling, composting, and source reduction by the avoided annual landfill methane reduction.

US EPA's MSW Decision Support Tool

The MSW Decision Support Tool (DST) is intended for use by solid waste planners at state and local levels to analyze and compare MSW management strategies with respect to GHGs and also cost, energy consumption, and environmental releases to air, land, and water (more than 30 air- and water-borne pollutants). It models emissions associated with municipal waste activities, including source reduction, waste collection and transportation, materials recovery facilities, transfer stations, compost facilities, combustion and refuse-derived fuel facilities, and landfills. The MSW DST can be used to optimize the system given constraints (e.g. determine the most cost-effective strategy for reaching specific policy goals, such as diverting 40% landfill waste). Text taken from DST requires detailed input information about the community's waste stream composition and operating information. Currently it is only available via support from Research Triangle Institute (contact Keith Weitz -,

Examples where communities have used MSW DST include: California's 2010 Life Cycle Assessment and Economic Analysis of Organic Waste Management and GHG Reduction Options and St. Paul, Washington State, and a composting facility in North Carolina.

EPA has done a comprehensive comparison of the WARM and MSW-DST tools. EPA does not recommend one in lieu of the other, but rather recommends choosing your tool based on the scope of analysis. Great effort has been made to reconcile differences between the two tools, such that given identical assumptions, the tools would yield identical results. The only major methodological difference between the tools is treatment of carbon storage and sequestration. MSW-DST reports carbon storage and sequestration separately. As of early 2011, MSW DST is not available free-of-charge, while WARM is. There are plans to make MSW-DST available at no cost in the future.

Process Life Cycle Analysis (LCA)

Process LCA is what most people think of when they hear of life cycle analysis. Process LCA maps the flows of materials through processes (mining, smelting, refining, extruding, transporting, etc.) and assigns resource flows and pollutant releases to each. EPA's WARM tool and MSW DST, and Environment Canada's GHG Calculator for GHG Management, are all derived from process LCAs of manufacturing products from virgin and recycled feedstocks, and end-of-life processes such as composting, incineration, and landfilling.

In most cases, off-the-shelf tools such as WARM will serve the needs of state and local governments, particularly when it comes to estimating the GHG emissions reductions or reduction potential of many prevention, recycling, and composting activities. Occasionally, however, special questions will arise regarding management methods or materials that have not been documented elsewhere. For example, WARM uses an average for all carpet. A green building program focusing on purchasing guidelines might want to know more about different types of carpet, such as Nylon-6 vs. Nylon-6,6 vs. wool. To answer these types of more detailed questions, process LCAs should be considered.

The greatest limitation of process LCAs are that they tend to be expensive and time consuming. However, the information gained from process LCAs are often very valuable. A few examples of process LCAs that have been commissioned by state and local governments, with a focus on materials management, are provided here.


EIO-LCA (Economic Input Output Life Cycle Assessment) is a input/output life cycle analysis tool produced by the Green Design Institute at Carnegie Mellon University. Certain EIO-LCA models (including a 2002 model of the US economy) are available free of charge via the Internet.

While EIO-LCA is a life cycle analysis tool, it operates very differently than "traditional" process LCAs (described above). While process LCAs are typically denominated in terms of mass, following the flows of materials through a supply chain and associated industrial processes, input-output LCAs are denominated in terms of dollars, following the flow of money through the economy.

EIO-LCA only evaluates life-cycle emissions upstream, associated with manufacturing, resource extraction and supply chains. It does not evaluate the full life cycle emissions (including use and end-of-life) for any given product or material. As such, its applicability for informing recycling programs is limited. In contrast, EIO-LCA can offer some rough estimates of the GHG impacts associated with producing a variety of commodities, and by extension, the GHG benefits of not producing those commodities (resulting from waste prevention, reuse, or other "sustainable consumption" efforts).

More information about EIO-LCA is provided here.