White Paper: Toxic Air Contaminant Emissions from Fossil Gas Appliances in California
- Sustainable Communities & Climate Protection Program
- Sustainable Communities
- Policy & Research Briefs
- Project Solicitation
- Pre-Proposal FAQs
- Technical Feasibility, Cost-effectiveness, and Policy Strategies for Reducing Embodied Carbon in Building Materials
- White Paper: Toxic Air Contaminant Emissions from Fossil Gas Appliances in California
- Regional Propane and Woodburning Utilization in Commercial and Residential Buildings across California
- Impacts of Telecommuting and Remote Services on Transportation, Land Use, And Climate Change
- Sustainable Communities Strategies Evaluation Process Update
- Guidance and Best Practices for Development of Greenhouse Gas Emissions and Vehicle Miles Traveled Mitigation Banks or Exchanges
- Developing an Equity Evaluation Framework for Place-Based, Community-Scale Mobility Investments
- Evaluate the Potential Quantification of Community Garden Project Benefits
- Quantification Methodology Development for Air Filtration, Microgrid, and Electric Bicycle Incentive Projects
- Housing Solutions for Climate and Equity
- Regional Plans & Evaluations
- Regional Plan Targets
- SB 150 Data Dashboard
- Active Transportation
This project will review and synthesize the current literature to 1) identify the most impactful toxic air contaminants (TACs) emitted outdoors from fossil gas use in both residential and commercial building appliances, with a particular focus on space and water heaters but also inclusive of cooking and clothes dryers; and 2) estimate TACs emission factors, both for combustion and leakage, based on end use, age of equipment/appliance, and building type. The objective of this white paper is to support CARB’s development of the Zero-Emission Appliance Standards.
In 1983, with the passage of Assembly Bill 1807 (Tanner, Chapter 1047, Statutes of 1983), the California Legislature provided the California Air Resources Board (CARB) with the necessary authority to identify and control TACs. Pursuant to Assembly Bill 2728 (Tanner, Chapter 1161, Statutes of 1992), CARB identified the 189 federally defined hazardous air pollutants (HAPs) as TACs in 1993. TACs are defined in the California Health and Safety code (Section 39655) as an air pollutant which may cause or contribute to an increase in mortality or an increase in serious illness, or which may pose a present or potential hazard to human health.
Many studies have focused on unprocessed fossil gas, documenting the presence of aromatic nonmethane volatile organic compounds (NMVOCs) such as benzene, toluene, ethylbenzene, and ortho-, meta-, and para-xylenes (BTEX)., These TACs are released to the environment both through leakage and combustion fossil gas. This is of particular importance given their reactivity as precursors to both ozone and secondary organic aerosol (SOA) formation, and their deleterious health effects.1 The Office of Environmental Health Hazard Assessment has created a list of health values for TACs. As communities move away from fossil gas use, it is important to characterize the co-benefits, such as health benefits, of decreased reliance on this major source of greenhouse gases and criteria pollutants.
CARB is developing zero-emission appliance standards, which are aligned with California’s climate and air quality strategy as laid out in the 2022 Scoping Plan adopted in December 2022 and the 2022 State Strategy for the State Implementation Plan adopted in September 2022. The results of this study would allow CARB staff to determine what the potential outdoor TAC emissions and related health impact co-benefits may be of this regulation.Appliance age, efficiency, and maintenance level are also important factors in emission characterization as only 8% of homes replace a natural gas water heater and 4% replace a natural gas space heater annually, according to internal analysis.
III. Scope of Work
This white paper will summarize the latest understanding of TACs emitted outdoors from fossil gas building end uses and estimate the emissions of the most impactful TACs from both a toxicity impact and prevalence perspective.
The draft scope of work below outlines CARB’s goals, desired outcomes, and potential deliverables for this project. The pre-proposal should address at a high level how the applicant will approach these tasks. Applicants are not required to stay within these specific parameters and are encouraged to suggest alternative tasks and methods for realizing project goals, based on their own expertise and understanding of the project and budget. The final contract and scope of work will be developed through an iterative process with CARB and the selected contractor and will include a detailed timeline as well as guidance on deliverables (i.e., white paper contents).
Task 1 – Conduct Literature Review
The proposer will provide a general overview of the primary bodies of literature and theoretical frameworks(s) informing their proposed approach, and how their scope meets a current knowledge gap in their field. Proposers should consider how the literature review product can synthesize information and present the information such that it is relevant and useable among state and local governments.
Task 2 – Develop Methodology
The proposer will build upon the literature review to develop a methodology to achieve the goals of this study. The methodology will include, but is not limited to:
- A literature review synthesis.
- Identify the TACs that will be the potential focus of this project and why (e.g., toxicity, and/or prevalence such as high emission factors or long atmospheric lifetime).
- Propose methods they will use to estimate emissions factors and emissions inventory for the identified TACs by end use.
- Estimate the emissions generated indoors by each end use (e.g., space and water heaters, cooking, clothes dryers) and building type that escape to the outside ambient air.
- Estimate the leakage emissions by each end use and building type.
- Focus on the nature of the fossil gas used within California, including any additives.
- Identify data sources needed to complete the emissions estimations.
- Create an outline/framework for the final white paper.
Task 3 –White Paper
The proposer will implement the developed methodology to draft a white paper:
- Utilize the identified method and data sources to estimate emissions factors for the identified TACs by end use and building type in both commercial and residential buildings (e.g. multifamily dwellings, single-family homes, office buildings, hotels, etc.).
- Present the emission factor estimates in an approachable format for CARB staff to estimate the TAC co-benefits of implementing the proposed Zero-Emission Appliance Standards.
The white paper will document the methodology used as well as summarize the results.
Task 4 – Presentation and Public Outreach
The proposer should outline their plan for synthesizing their project findings in a final report and presentation, and any additional public outreach activities (such as webinars, fact sheets, community meetings, etc.).
At Pre-Proposal Stage
- Approach to literature review, sources for review and synthesis methods.
- A list of proposed project tasks and deliverables.
At Beginning of Contract
- Work with CARB staff at the beginning of the project to create a 1-page plain-language outreach deliverable for the public describing the project’s goals, process, and planned deliverables (available in multiple languages, template will be provided).
During Active Contract Period
- Quarterly Progress Reports including public-facing updates to be posted to CARB’s website.
- Quarterly Progress Meetings.
- Informal monthly progress update meetings with CARB contract manager.
- Final detailed study plan.
- Literature review.
- Draft white paper.
Prior to Contract Close
- Final white paper.
- Seminar presenting summary of results.
- Presentation summarizing findings at community meeting(s) or workshop(s) (if applicable).
Additional deliverables to be determined in consultation with CARB staff. Contractor will be responsible for making all deliverables Americans with Disabilities Act (ADA) compliant.
It is anticipated this project will be completed in 12 months from the start date (start date is estimated to be in Spring 2024). The estimated budget for this project is up to $100,000.
1. Responsiveness to the goals and objectives outlined in the proposal solicitation (20 points)
The proposal should explain—in adequate detail and clear, understandable language—how the proposed project satisfies the project objectives. This contract should synthesize current literature to identify the latest understanding of 1) the most toxic and/or prevalent toxic air contaminants (TACs) emitted outdoors from fossil gas use in residential and commercial building appliances, with a particular focus on space and water heaters; and 2) estimate the identified TACs contribution to statewide emissions based on end use equipment/appliance age and level of maintenance and building type.
2. Work experience and subject matter expertise (20 points)
The proposal should demonstrate that the proposers have the work experience or subject matter expertise required to successfully carry out the proposed project as described. Additionally, the proposal should describe how the project will build upon previous relevant work that was funded by CARB, other regional, state, and federal agencies.
3. Expanding expertise (10 points)
The proposal should explain how the project team expands expertise such as by incorporating multidisciplinary expertise or perspectives, including members from various public universities, non-academic institutions, or community-based organizations, or providing opportunities to build skills and expertise for individuals from underrepresented groups. Reviewers will consider if key personnel contributing significantly to the project (i.e., a principal investigator, co-principal investigator or co-investigator, contributing 25 percent or more of their time to the project) have not worked with CARB in the past five years.
4. Explanation of technical or methodological approach (20 points)
The proposal should clearly explain the logic and feasibility of the project’s methodology, spell out the sequence and relationships of major tasks, and explain methods for performing the work. The proposal should include a clear description and plan for how each task will be completed.
5. Level and quality of effort and cost effectiveness (15 points)
The proposal should describe how time and resources will be allocated and demonstrate how this allocation ensures the project’s success. Proposal reviewers will evaluate, for example: if the objectives of the project can be met given this allocation, if there is adequate supervision and oversight to ensure that the project will remain on schedule, if time and cost are appropriately divvied up across different project tasks and stages.
 Michanowicz et al, 2022. “Home is Where the Pipeline Ends: Characterization of Volatile Organic Compounds Present in Natural Gas at the Point of the Residential End User.”
 Lebel et al, 2022. “Composition, Emissions, and Air Quality Impacts of Hazardous Air Pollutants in Unburned Natural Gas from Residential Stoves in California.”