One of the biggest buzzwords in the green building industry right now is carbon, and for good reason. Carbon is, after all, inextricably linked to the greatest threat faced by humankind: the climate crisis. Though very simple when taken at face value, carbon has a lot of intricacies as it relates to the green building industry. From embodied carbon to net zero carbon to carbon sequestration, the variations are endless! Let’s dive deep into the vast world of carbon and define these terms.
Before defining complex carbon terms, let’s first start with the basics and define carbon. In the context of buildings, “carbon” refers to carbon dioxide, which is a long-lived greenhouse gas. Carbon dioxide levels are currently at an all-time high as a result of human industrial activities, contributing to global warming, ocean acidification, and a variety of other secondary impacts.
In an attempt to slow the impacts of climate change, carbon sequestration is used to capture and store atmospheric carbon dioxide. Carbon sequestration takes place naturally through the storage of carbon in vegetation, oceans, and soil. More technologically advanced methods involve capturing carbon and using it as a resource to create building materials, fuels, and carbon materials.
Carbon offsets are actions to offset or compensate for emissions of carbon dioxide into the atmosphere. A prominent example of this is investing in projects that aim to reduce CO2 emissions, such as new renewable energy infrastructure or carbon sequestration projects. Carbon offsets are often used to achieve many of the carbon performance standards defined below.
Operational carbon is exactly what it sounds like: it’s the CO2 emissions associated with building operations. A building that uses electricity from a coal-fired power plant would have operational carbon associated with it, since burning fossil fuels (such as coal) produces carbon dioxide emissions.
Going a step further than operational carbon, embodied carbon is all the CO2 emissions associated with the entire life cycle of building materials, including mining, harvesting, processing, manufacturing, transportation, and installation. The embodied carbon emissions of a new building are equivalent to about 20 years of operating emissions, making this category of carbon absolutely critical to address. To reduce the embodied carbon of a building, you can reuse buildings and materials, maximize high recycled content materials, choose carbon sequestering materials, and minimize waste.
Decarbonization is the reduction of carbon dioxide emissions over the entire life cycle of a building, addressing both operational and embodied carbon. This can be achieved in many ways – increasing energy efficiency, generating and procuring renewable energy, investing in carbon offsets, etc. You may be familiar with decarbonization from L.A.’s Green New Deal, which focuses in part on decarbonizing new and existing buildings.
A building that is zero carbon does not generate any carbon emissions, period. An example of this would be a building that is powered by 100% renewable energy. Zero carbon is currently only feasible when considering operational carbon. A zero-carbon building that included both operational and embodied carbon would mean that every step in the building’s life cycle – and every step in the building materials’ life cycles – would be powered by 100% carbon-free energy. We’re not there yet, but we’ll get there one day!
Carbon Neutral / Net Zero Carbon
You’re likely familiar with these terms, as large companies such as Apple have recently committed to ambitious carbon neutrality goals. In the context of green building, a building that is carbon neutral or net zero carbon emits net zero carbon emissions into the atmosphere. This can be achieved through energy efficiency measures, renewable energy generation and procurement, and carbon offsets. Therefore, a carbon-neutral building may still generate CO2 emissions, but these emissions must be counterbalanced by carbon offsets. Some carbon neutral or net zero carbon standards only address operational carbon, while others are more comprehensive and address both operational and embodied carbon.
Carbon negative goes beyond net zero carbon to remove more carbon from the atmosphere than is emitted. Essentially, carbon-neutral buildings “do no harm” by emitting net zero CO2, while carbon-negative buildings go a step further and contribute to positive environmental benefits. Some ways to achieve a carbon-negative building include generating excess renewable energy and sending it back to the grid or incorporating carbon sequestration projects that more than offset the building’s carbon emissions.
As confusing as it may sound, carbon negative and carbon positive are actually interchangeable terms. Carbon positive is a more optimistic-sounding version of carbon negative and is mainly used in marketing, but it has the same meaning as carbon negative: removing more carbon from the atmosphere than is emitted.
Who knew carbon could be so complex! Though there are numerous ways to talk about carbon emissions in the green building sphere, there’s only one way to manage carbon: reduce it. Let’s embrace the industry focus around carbon, understand the nuances and variations, and take action to decarbonize our built environment.