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How Landscape Architects Can Harness Embodied Carbon
“Landscape architects have started talking about embodied carbon. People are recognizing that we can no longer ignore the gray,” Stephanie Carlisle, senior fellow at the Carbon Leadership Forum and University of Washington, said at a conference organized by the American Society of Landscape Architects’ Biodiversity and Climate Action Committee. said during the first of a series of webinars.
The gray sections are concrete, steel, and other manufactured goods in the project. The conversations that are taking place lay the groundwork for moving away from using these materials. Landscape architect climate leaders driving these conversations are offering practical ways to decarbonize projects and specify low-carbon materials.
“The built environment now accounts for 40% of global greenhouse gas emissions,” Carlisle said. As the population grows, “the global building stock is expected to double over the next 40 years. That means a new New York City every month.” It also means that “between now and 2050, embodied carbon is expected to account for More than half of emissions from buildings.”
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For landscapes, approximately 75% of emissions come from embodied carbon. These are produced through the extraction, manufacture, transportation and installation of landscape materials. The other 25% comes from operations – lighting, water systems and maintenance. “Landscape projects are infrastructure. They are carefully designed. They share the same materials as buildings, roads and bridges,” Carlisle said. “Parks and other landscaping can also be hardscapes using concrete and steel.”
ASLA’s Climate Action Plan calls for eliminating embodied carbon emissions from projects by 2040. Landscape architects can achieve this by tracking the global warming potential (GWP) of the materials they specify. Life Cycle Assessment (LCA) is the global standard for measuring a project’s GWP. It covers the energy and emissions generated by material manufacturing, construction processes, material use and their end-of-life reuse, recycling or disposal.
In the past, LCA has typically focused on buildings, but Carlisle and landscape architects are leading the shift to project-wide LCA, which also includes energy and water use and emissions from the landscape and infrastructure surrounding the building. There are a range of tools for measuring project impact, including professional LCA tools, carbon calculators, design-integrated whole-building LCA tools and product libraries.
Another way to measure GWP is through Environmental Product Declarations (EPDs). These require product manufacturers to develop. EPD determines the carbon emissions of products and is a supplement to the plant-wide LCA. “Designers can use both models.” Carlisle said LCA should not be used “only for special projects” but should become part of a landscape architect’s core design services. “This is the path to zero emissions.”
She also urges landscape architects to:
- “Build less, reuse more
- Designed to be lighter and smarter
- Use low-carb alternatives
- Purchase low-carbon products
- Minimize on-site disruption
- and increased carbon sequestration. “
But she noted that landscape designers should be realistic about how long it takes for carbon to be stored in soil and plants. In all of these efforts, “landscape architects are the driving force behind the game,” says ASLA, PLA, Sasaki senior fellow and founder of Carbon Conscience, leading the industry’s transition says Chris Hardy, landscape architect at Carbon. “The architects were about 10 years ahead of us.”
Although the entire building LCA process has been in development for over five years, the entire project LCA approach was only recently developed through Climate Positive Design’s Pathfinder tool. Hardy recommends that landscape architects focus on the carbon content of products and their alternatives; the construction process; and the circular economy, including how products are reused or recycled after their use in the landscape has ended.
Landscape architects also have the unique ability to store carbon in the landscape through soil, plants and trees. This provides a great opportunity. But he points out that carbon storage capacity varies by ecosystem type. “Wetlands, saltmarshes and mangroves have higher carbon storage capacity, followed by forests and grasslands.”
At Sasaki, he developed carbon awareness tools to “change the conversation during the project concept and planning stages,” when the opportunity to reduce emissions is greatest. The tool enables landscape architects to understand the carbon impact of different site scenarios. There are 260 landscape and 250 building uses available. Soon, landscape architects will be able to move their conceptual designs from carbon-conscious to climate-positive design’s Pathfinder, where more detailed carbon calculations can be performed based on specific material choices.
“Our mission is to decarbonize,” says Climate Positive Design founder Pamela Conrad (ASLA, PLA), who has been a leader in the field of decarbonizing landscape design for five years. leader of. “Seven years ago, when I was working on the Treasure Island project off the coast of San Francisco, I realized that landscape architects were discussing climate impacts like sea level rise rather than the carbon footprint of our projects.”
When Conrad started crunching the numbers, she discovered that the landscape she designed would take 200 years to offset. But with some adjustments that maintain design integrity, the lifespan can be reduced to 20 years. “That was an awakening moment. I realized we needed to change the way we were doing it.”
Conrad serves as chair of the working group that develops the ASLA Climate Action Plan in 2022. In the plan, she outlines science-based goals that landscape architects need to achieve. “To limit global warming to 1.5°C (2.7°F), we need to halve project emissions by 2030. We then need to reach zero emissions by 2040 and increase current carbon sequestration rates Double that.”
Conrad has been tracking the carbon performance of landscape design projects. To date, more than 10,000 projects have been submitted to Pathfinder, which will plant a total of 1.9 million trees, the equivalent of taking 400,000 cars off the road. But there is still much work to be done. Landscape architects will need to further adjust their design approaches to take into account a project’s global warming potential.
Conrad encourages them to apply practical strategies:
- “Integrating walking and cycling infrastructure
- Use recycled and reused materials
- Replace cement with other lower carbon materials
- Reduce site disturbance that impacts soil carbon storage
- restore ecosystem
- Increase planting area
- Green Creativity”
“Just sourcing products locally can reduce transport emissions by 15-20%.” As pathfinders and carbon conscience develop further, landscape architects will also need to collaborate more with architects and engineers on decarbonization. With their ability to store carbon in the landscape, they could play a greater role in reducing the climate impact of the built environment.
This article originally appeared in Dirt.
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