What is carbon neutrality, Energy expert guide, climate change design, Green architecture
What is carbon neutrality?
December 14, 2021
An Energy Expert Answers the Question: What Is Carbon Neutrality?
Written by Tim Johnson, Mechanical Engineer, Cushing Terrell
What is carbon neutrality – built environment
We’ve seen big companies and organizations in the headlines lately as they make carbon neutral pledges, publicly stating their commitment to slowing the effects of climate change. These goals are admirable, but are they attainable? And perhaps more importantly, do we really understand what it means to be carbon neutral?
In the building industry, the carbon conversation has been ongoing for years. Those who study carbon emissions are keenly aware that the built environment is a major contributor to a warming planet. Organizations such as Architecture 2030, American Institute of Architects (AIA), the Carbon Leadership Forum, and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) are working toward common definitions, but in the meantime, as we seek a universal standard, there are meaningful steps we can take toward carbon reduction now — and maybe, eventually, carbon neutrality.
As an engineer immersed in energy modeling and research, the carbon issue is always on my mind and a big part of my work. In this blog post, I hope to help clear up some common misconceptions about carbon accounting methods, as well as layout reduction strategies, define commonly used terms, and get you on your way to developing standards and taking steps to reduce the carbon footprint of your own project, building, or operations.
Carbon and Energy
Carbon and energy are strongly linked and often used synonymously. For example, the Architecture 2030 Challenge, which is targeting carbon-neutral buildings, tracks total building energy consumption, not carbon emissions. While energy reductions will generally lead to carbon reductions, there are nuances that are becoming increasingly important to understand.
Establishing the Boundaries for Calculating Emissions
In the absence of a standard definition of carbon neutrality, each organization is allowed (or obligated) to determine where to draw their own accounting boundaries and methods for offsetting emissions. Thus, it helps to first understand the concept of carbon neutrality, before choosing how to calculate it.
The basic idea of carbon neutrality is offsetting all of one’s carbon emissions through renewable energy or carbon sequestration. However, there are still debates about what should be included when it comes to calculating carbon emissions and offsets.
The basic idea of carbon neutrality is offsetting all carbon emissions through renewable energy, sequestration, or removal of carbon, but calculating the balance isn’t as straightforward as it sounds. There are questions about what boundaries exist and where they are. Answering these questions first requires knowing how carbon emissions are defined.
Three Scopes of Emissions
To calculate emissions and set boundaries, it helps to understand how emissions are categorized. The U.S. Environmental Protection Agency (EPA) defines emissions within three distinct scopes:
Scope 1 includes any emissions from sources owned by an organization. This includes direct fossil fuel consumption from natural gas heating systems and gasoline usage in company vehicles.
Scope 2 generally consists of emissions due to fossil fuel combustion at offsite electric generation facilities.
Scope 3 emissions are the most difficult to quantify as they include emissions from the supply chain, including material harvest and transportation, business travel, waste generation, investments, and the processing and use of a company’s products. The most common Scope 3 emissions category included in building analyses is embodied carbon.
When establishing carbon reduction targets, all three types of emissions need to be considered. Using environmental product declarations (EPDs), a material’s carbon impacts can be tracked all the way from cradle to grave.
Methods for Offsetting Emissions
Once an organization determines their boundaries for calculating emissions, methods of offsetting these emissions need to be evaluated, because there are many, and all come with their own advantages and drawbacks. For instance, the use of renewable energy is a common method of carbon reduction, but the location and transmission of that energy must also be taken into account: Is the energy generated offsite and transmitted to your location as valuable as the energy that could be generated on site? Another option is purchasing carbon offsets to match a facility’s carbon footprint. This puts money toward renewable energy, forest management, and other strategies — but these offsets generally occur at a remote location.
Other carbon offsetting methods may include capturing and destroying gases that would otherwise end up in our atmosphere. Burning methane from landfills or farm waste are good examples of carbon capture. Or relying on plants to naturally capture carbon dioxide by investing in sustainable forestry.
For years, the building industry has been aware of the impacts of the built environment on greenhouse gas emissions. Buildings generate nearly 40% of annual global CO2 emissions — and of those, building operations are responsible for 28% annually, while building materials and construction are responsible for 11% annually.
As business owners or those in the design community, it’s crucial to know we have options for reducing carbon emissions, which can be actioned immediately and with relative simplicity. For example, Architecture 2030 initiated the 2030 challenge in 2006 with a goal of net zero carbon emissions by the year 2030. Rather than going through the complicated calculations associated with carbon emissions, this challenge uses energy as a surrogate for emissions.
While this doesn’t paint the whole picture, energy efficiency and renewable energy production are still the most effective methods of reducing carbon emissions in our buildings.
Site Energy vs. Source Energy
It is important to understand the difference between site energy and source energy. The energy usage number you see on your utility bill is site energy. The energy required to generate and deliver that energy to your location is called source energy. On average, electric source energy is a little less than three times site energy while natural gas source energy is about 10% more than site energy.
In many cases, buildings can be designed to reduce energy consumption with very few upfront costs. Similarly, existing buildings can often save substantial amounts of energy with little capital investment. Energy modeling and benchmarking are effective tools for identifying and prioritizing efficiency opportunities.
Electrification of buildings is one common strategy for carbon reduction, which means eliminating fossil-fuel combustion from equipment like water heaters, kitchen appliances, and HVAC systems. However, it is important to consider where our power comes from, because there are cases where electrification will actually result in increased carbon emissions. For example, when we factor in the source of our power and the losses associated with generating that power, we find that — at this time — burning natural gas directly actually results in less carbon emissions than using electric resistance heating. That means when we electrify appliances with electric resistance heat, we are making a bet on the power grid increasing renewable energy production within the life of the purchased equipment. In many locations, there have been strong commitments toward increasing renewable energy contributions to the electric grid, but in some areas, the improvements are more gradual.
Tools like EPA’s Power Profiler can help us understand our local electric grid. According to the Profiler, about 17% of our nation’s power comes from renewable sources and the remainder comes primarily from gas and coal. The fuel mix varies widely between regions, so a key step is to check your local utility and region.
One option for reducing carbon emissions through electrification is using heat-pump technology for heating systems. This system uses the refrigeration cycle running backward to transfer heat from a heat source (often outside air) to the indoors. Depending on the heat source, this type of system usually uses one-third or less of the energy of electric resistance heat and subsequently, results in significant greenhouse gas reductions in most electric grids.
Renewable Energy Production
Once we have reached a practical limit for energy efficiency in our buildings, we need to look at how to implement renewable energy to offset energy consumption and GHG emissions. In most cases, solar photovoltaic (PV) is the most cost-effective renewable source of onsite renewable energy, but solar thermal, wind, biomass, or geothermal resources may be viable options in many areas. See Cushing Terrell’s Solar Integration Design Guide for ideas on how on-site solar might fit into your project.
PV Energy Systems
A common misconception about solar energy is that the panels require more energy to produce than they generate. While it is true that solar panels require a high energy input in manufacturing, the energy generated from these panels offsets the embodied energy in roughly two years, depending on location.
The Big Challenge: Embodied Carbon
With the right combination of energy efficiency measures and renewable energy generation, net zero energy can be achieved, but to achieve true carbon neutrality, Scope 3 emissions are a critical consideration. Scope 3 emissions are generally associated with supply chain, travel, and commuting and vary widely from company to company.
The term embodied carbon represents the idea that the materials we use have an environmental impact in their extraction, maintenance, and eventual disposal. In the context of building design and construction, these Scope 3 emissions can have a big impact. For example, the steel used in sheet metal must be mined, manufactured, installed, maintained, demolished, and disposed of, and in between each of those processes, there is transportation from one location to another. Even lumber, which is generally considered to sequester carbon, still requires energy between harvest and use in a building.
At a glance, these components are hard to quantify, but it is possible to understand the impacts of embodied carbon on a building’s carbon footprint by way of a life cycle assessment (LCA). This type of analysis uses information from EPDs to estimate the cradle-to-grave impacts of materials. In general, materials such as concrete and steel are high embodied carbon materials and are good targets if you’re looking to reduce carbon emissions.
Embodied vs. Operational Carbon
Embodied carbon is less tangible than operational carbon. This concept includes carbon emissions from the harvest of materials to manufacturing, construction, repairs, and finally demolition and disposal. As buildings become more efficient and our energy generation becomes more renewable, greenhouse gas emissions associated with building energy consumption are reduced and the embodied carbon becomes a higher priority.
While exact definitions and measurements of carbon emissions are still being fleshed out, we know that work can be done to move the needle on reducing a building’s overall emissions and impact on the environment.
A good first step is to work with energy modeling and systems design consultants. These experts don’t have all the answers, but they can help you take the critical first step of outlining a plan for honoring your carbon commitment and help solve for important and specialized questions including:
How can we make the project as efficient as possible within a set budget?
What is the local electric generation fuel mix? Is this a good project to consider electrification?
How might renewable energy be worked into this project? If the budget can’t afford renewable energy now, can we include some basic infrastructure to make it easier later?
What materials have the largest carbon footprint and how can we reduce it?
What are some of the carbon impacts of the business operations and how might they be reduced?
What are some ways to offset the remaining carbon footprint that could be implemented now?
When it comes to setting ambitious sustainability and carbon reduction goals, it is easy to become hyper focused on a single piece of the puzzle, but when we are talking about quantifiable carbon impacts, it is important to have a broader focus. By considering and understanding the big picture, we can make meaningful progress toward achieving carbon reduction goals.
About Tim Johnson
Tim is a mechanical engineer and a member of Cushing Terrell’s Energy Services team. His focus is on building performance analysis, specifically energy modeling to help reduce building operating costs, minimize environmental impacts, and improve occupant health and well-being. His experience includes mechanical and plumbing design and document production for schools, commercial offices, supermarkets, healthcare facilities, industrial facilities, and government buildings.
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Design: sculpture by Gerry Judah
photo : Dan Sellers
DRIFT, Dallas, Texas sculpture by Gerry Judah
Commonwealth Pier, Seaport World Trade Center, Boston, Massachusetts
Design Architect: Schmidt Hammer Lassen Architects
image © Schmidt Hammer Lassen Architects
Commonwealth Pier Boston
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