Reinforcing the ground beneath our feet

CEE’s Mike Gomez and his team are using bacteria to strengthen soil and prevent liquefaction, offering a sustainable alternative to traditional methods.

When a powerful earthquake strikes, the damage is often visible — collapsed buildings, cracked roads and broken infrastructure. But sometimes, the most dangerous effects happen below the surface. In earthquake-prone regions worldwide, a phenomenon called soil liquefaction has caused massive destruction, from Japan to New Zealand to the United States. Liquefaction occurs when intense shaking turns water-saturated sand into something that behaves like quicksand, causing the ground to lose its strength and structures to sink, tilt and sometimes collapse.

For decades, engineers have tried to strengthen soils and prevent these failures using cement-based grouts and mechanical methods like ground compaction and vibration, but these approaches are costly, disruptive and often have a high environmental impact.

What if bacteria could provide a better solution?

When the ground fails

Liquefaction occurs in loose, saturated, sandy soils, where gaps between soil grains are filled with water. During an earthquake, quick shaking causes the loose sand particles to shift and try to pack more tightly together. However, because water fills the gaps between them, the particles can't rearrange. Instead, the pressure in the water builds up, pushing the sand grains apart. As a result, the solid ground momentarily loses its strength and behaves more like a liquid, making it unable to support the infrastructure above it.

Traditional solutions involve injecting cement-based grouts or other synthetic additives into the soil to bind it together or applying mechanical energy to compact soils into denser arrangements. While effective, these approaches are energy-intensive, require heavy equipment and contribute significantly to global greenhouse gas emissions.

Mike Gomez, an associate professor of civil and environmental engineering at the UW, is working on an alternative: biocementation, a process that uses bacteria to strengthen soils naturally from within.

A more sustainable way to strengthen soil

Biocementation is inspired by nature. Just as corals and shellfish use calcium carbonate in their protective shells, this process uses bacteria already present within soils to begin forming similar minerals underground. Instead of injecting cement-based materials, engineers introduce a water-based solution containing nutrients, urea and calcium salts into the ground. The solution enables the growth of bacteria, which act like microscopic builders, producing an enzyme that breaks down urea and releases carbonate ions. These ions react with calcium in the solution, forming calcium carbonate — the same mineral found in limestone. As this mineral grows, it “cements” sand particles together, transforming loose sand into a rock-like material that can better resist liquefaction.

"We’re taking something that looks like loose sand and, in a matter of days, turning it into something that behaves more like soft rock," Gomez explains. "Although such changes can occur naturally over geologic time, we’re doing it with a process that is dramatically accelerated by microorganisms."

Because the biocementation process relies solely on liquid injections, it requires no excavation or heavy construction equipment, making it ideal for urban environments where reinforcing the ground under existing buildings, roads and bridges can be difficult and more disruptive with traditional methods. Unlike thicker cement and chemical grouts, which require high pressure to inject, biocementation treatments flow easily through the soil, allowing them to reach deep underground with minimal disturbance.

"With this method, we’re injecting a fluid that has essentially the same viscosity as water, so it has the potential to be transported over larger distances under existing infrastructure with minimal disruption," Gomez says.

Beyond its practical advantages, biocementation can offer significant environmental benefits. Portland cement, the key ingredient in most soil stabilization methods, is a major contributor to global CO₂ emissions, accounting for nearly 8% of total emissions worldwide. Conventional soil stabilization methods are used in over 40,000 projects annually in the U.S. alone, costing more than $6 billion per year. These methods are effective but come at a steep environmental price, contributing to greenhouse gas emissions and changes in soil ecology, and have even resulted in groundwater contamination in some instances. Biocementation offers a way to realize comparable engineering benefits with lower environmental impacts.

Biocementation eliminates the need for cement-based grouts by using bacteria to form calcium carbonate, which binds soil particles together. And while engineers once thought they needed to create a hard sandstone-like material to reduce liquefaction, Gomez’s research has shown that even a tiny amount of cementation — less than one percent by mass — can significantly improve soil strength.

"We’re realizing that even a small amount of cementation can lead to significant improvement," Gomez explains.

This means fewer materials, lower energy consumption and the possibility of a much smaller carbon footprint compared to conventional soil improvement methods.

Gomez is also exploring different approaches to generate biocementation by drawing inspiration from natural materials found in shells and insect skeletons — materials that provide both strength and flexibility. By incorporating more flexible components, his team hopes to create a version of biocementation that is not only strong but also better able to withstand extreme loading events.

"Ultimately, these efforts could help us develop new materials that are more durable and can provide new functionalities for different engineering challenges," Gomez says.

Bridging the gap between innovation and trust

Like any new technology in engineering, biocementation faces skepticism. The industry has relied on cement-based solutions for decades — not necessarily because they’re perfect, but because they’re familiar.

"In almost every area of civil engineering, our profession has remained heavily reliant on Portland cement," Gomez says. "We know cement, we trust cement, and there’s no one questioning whether or not it works."

Biocementation, by contrast, introduces something unfamiliar: the use of bacteria to initiate the natural formation of minerals in the soil.

"We are not as used to using biological processes in geotechnical engineering," Gomez says. "And that’s part of the challenge: not just proving that it works, but helping people understand how it works, where it makes sense to use it, and identifying its limitations just like we would any other ground improvement technology."

Gomez has spent years educating engineers and industry leaders, presenting at conferences, visiting consulting firms and showing lab results. While many are intrigued by the technology, he notes that engineers are hesitant to adopt new methods until they can trust that they are as successful, reliable and safe as traditional methods.

That proof starts in the UW’s Biogeotechnics Lab, where Gomez and his team study how biological processes, like biocementation, can change the way soil behaves. One way they test this is by sending small, non-destructive shear waves through treated soil samples to measure how these processes affect a soil’s stiffness — the faster the waves travel, the stiffer the soil is, which correlates to the amount of cementation generated.

They also simulate earthquake loadings by repeatedly cycling the treated soil samples under controlled conditions to see how they behave prior to and after the occurrence of soil liquefaction.

"In some of our tests, untreated loose sands can see liquefaction within just a few loading cycles,” Gomez explains. "But when we add even a small amount of cementation, a level that we can detect with non-destructive shear waves but not enough to feel by touch, the same soil can withstand tens or even hundreds of cycles before liquefaction occurs."

This dramatic improvement, achieved with minimal material input, highlights biocementation’s potential as a low-impact, sustainable alternative to traditional ground improvement techniques.

Looking ahead

So far, much of what’s been learned about biocementation comes from lab tests. The next step will be testing it in real-world conditions.

"The geotechnical engineering community has already completed many large-scale tests and field trials using this technology, but they’ve been for things like sealing rock fractures or stabilizing soil erosion," Gomez says. "So far, none have been for the deeper geotechnical challenge of liquefaction mitigation."

Field trials present unique challenges. Unlike the uniform soil conditions in a lab, real sites have varied soil types, groundwater flow and less predictable environmental conditions. Engineers will need to figure out how to distribute nutrients evenly through different materials, control reaction speeds, and ensure that cementation remains effective and stable long after treatments have been completed.

Another challenge is adoption. Despite its potential, biocementation is still relatively new, and industrial use of the technology has been limited.

"There is a real opportunity to deploy this technology for problems with few existing solutions," Gomez says. "A successful field trial for liquefaction mitigation could pave the way for wider adaptation, and our research team is committed to realizing real-world impacts."

The demand for sustainable engineering solutions is growing. And as biocementation continues to prove its effectiveness, it could become a powerful tool for protecting infrastructure from earthquake damage — offering a less disruptive, more sustainable alternative to traditional soil stabilization.