Building a Carbon Negative Future with Steel and Cross Laminated Timber
In a new $3.1M grant from the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E), Northeastern Department of Civil and Environmental Engineering Chair and CDM Smith Professor Jerome Hajjar will lead a multi-institution team of researchers developing a new carbon sequestration technique using cross-laminated timber composite floor systems in bolted steel construction for building structures. The new structural method aims to decrease the use of steel while increasing the use of carbon-storing timber and design for deconstruction methods. The team envisions the research may enable widespread construction of carbon-negative multi-story buildings in the coming years.
The construction industry represents a major piece of the climate puzzle. Emissions from the mining, fabrication, and transportation of construction materials such as concrete, timber, and steel greatly contribute to society’s annual carbon output. “There’s huge, untapped potential in reimagining building materials and construction techniques as carbon sinks that support a cleaner atmosphere and advance President Biden’s national climate goals,” said U.S. Secretary of Energy Jennifer M. Granholm in a press release from ARPA-E announcing the grant. “This is a unique opportunity for researchers to advance clean energy materials to tackle one of the hardest to decarbonize sectors that is responsible for roughly 10% of total annual emissions in the United States.”
The new research builds on a promising technology: cross-laminated timber (CLT). The research team estimates that traditional building materials contribute nearly half of a high-rise commercial building’s embodied carbon emissions. Cross laminated timber can be partially substituted for some of these materials. Timber’s origin as a photosynthetic lifeform means it serves as a “carbon sink,” and CLT diaphragms can store about 50% of their weight in carbon until it decomposes or is otherwise destroyed. “We are exploring how timber may be incorporated into our design thinking in a way that complements other emerging sustainable practices such as steel recycling and renewable energy-powered forging,” says Hajjar.
The team will work to further understand the structural properties of CLT and develop new solutions for improving the design of CLT within steel building structures to move past traditional structural limitations of timber. According to the team, CLT buildings are “held back by designs that are constrained by the limited mechanical performances of timber, imposing stricter span limits or increased beam depth (increasing building height up to 10%).”
To achieve their carbon reduction and CLT design improvement goals, the team will utilize another innovative method Hajjar has helped pioneer. Design for Deconstruction (DfD) is a method of steel framework design allowing deconstruction of the building at the end of its lifecycle in a manner that preserves the steel components for reuse. In this grant, the team will study combining DfD steel and CLT to create a new framework for buildings designed with greener, more reusable materials.
The ARPA-E grant was awarded as part of the Harnessing Emissions into Structures Taking Inputs from the Atmosphere (HESTIA) program. The grant team will include industry partners Simpson Gumpertz & Heger (SGH) led by Mark Webster, and OPAL, led by Matthew O’Malia; researchers from the University of Massachusetts Amherst, including Professor Sanjay Arwade and Associate Professor Kara Peterman, and Swarthmore College, including Assistant Professor Fiona O’Donnell. Northeastern researchers include Hajjar, Assistant Professor Michael Kane, Associate Professor Matthew Eckelman, Associate Professor Michelle Laboy, and Roux Institute Director of Engineering Research and Professor Jack Lesko, and Research Associate Professor Nathan Post from the Roux Institute.
Eckelman, an expert in lifecycle assessment of materials and processes, will model how the new method of DfD + CLT will differ from current methods in their carbon emissions. Michael Kane, a structural engineer with expertise in automation, artificial intelligence, and building energy systems, will design AI methods that will inform the researchers about the differences in the mechanical properties of local timber feedstocks, further improving their understanding of the structural performance of the CLT diaphragms. The ability to source timber locally will further decrease a build’s carbon emissions by limiting the material transport distance. Laboy will research the design and modeling of whole buildings, including structural patterns and enclosure systems, that will be used by the Life Cycle Assessment experts, while Jack Lesko and Nathan Post will be supporting the development of the design standards for reclaimed structures based on service life reductions in properties and performance. The teams at University of Massachusetts and Swarthmore will be leading the identification of appropriate timber species and the development of innovative layups for the CLT floor system. “We believe that by combining Design for Deconstruction and Cross Laminated Timber, baseline emissions can be reduced by up to 70%, and the reusable nature of the building materials will mean the biogenic carbon potentially stays locked in for long enough to qualify as carbon negative,” said Hajjar.