Retaining walls have changed in structure, material and integrity over the years, as environmental, aesthetic and practical needs have shifted. However, making the practice greener has become a more prominent priority in recent years, requiring engineers and builders alike to consider key parameters like embodied energy and recyclability. How do the most common materials compare to one another when observing their life cycle — including harvesting, maintenance and disposal?
A Life Cycle Comparison of Retaining Wall Materials
Here is a look at the most popular materials used in retaining walls, evaluated based on their embodied carbon, and how maintenance needs and longevity impact their life cycle assessment, which covers 30-50 years.
Material | Embodied Energy | Durability and Lifespan | Environmental Impact and Carbon Footprint | Maintenance Demands |
Natural stone | Low because of heavy reliance on natural processes, but higher when considering transportation | 50-75 years | Low to moderate based on the intensity of quarrying and transportation, but can incorporate reused materials and local assets | Minimal if provided adequate drainage |
Concrete | High due to high energy requirements and intensive mining | 50-75 years | High because of high-temperature manufacturing and the carbon footprint of cement | Medium if cracking appears |
Gabion baskets | Low to moderate, depending on wire materials and cage contents | 50-75 years | Low if the wire mesh is made sustainably and the cage is filled with low-carbon materials like local stone or recycled tires | Minimal if corrosion prevention strategies are used |
Engineered timber | Low because of renewability and lower processing temperatures | 30-35 years | Moderate due to deterrents like chemical use, but benefits like carbon sequestration | High due to frequent inspections and finishings |
Recycled options | Very low, even for recycled cement | Varies based on material | Very low, depending on the materials, as it can prevent landfill waste and cut energy from virgin material processing | Varies based on material and composition |
Analyzing the Most Sustainable Retaining Wall Options
By the numbers, the most eco-conscious options are gabion baskets and recycled alternatives. They have a long shelf life, while requiring low processing and minimizing stress on transportation systems. If materials are repeatedly cycled through the economy, then their life cycle assessment becomes greener after each use case. However, there are several nuances to consider.
The longer a retaining wall stands without replacements or repairs, the better it is for the planet. Natural stone, if sourced locally to minimize transportation emissions, may be a better long-term option compared to alternatives due to its resistance to the elements. Options, like concrete and timber, may be cheaper, but they need replacing more frequently, adding to their adverse impact.
Stakeholders should also consider how a material provides other sustainability benefits in the area. Investing in outdoor features can also reduce the carbon footprint of nearby households by protecting them against climate stressors, while increasing property value. Efforts like landscaping — which may include hardscaping fixtures such as retaining walls as protective or decorative features — could boost the price by 5.5% to 12.7% if they appeal to the design preferences of modern buyers.
All retaining walls support climate mitigation, helping to stave off the negative effects of environmental damage and rising temperatures. Some variants, like living walls, can also incorporate organic materials to restore nature while providing the benefits of conventional retaining structures. Nature-based solutions are inherently more sustainable, as they offset some of the embodied energy associated with a material’s acquisition or transportation.
Choosing more sustainable materials should be the direction experts move in. However, vegetated or living retaining walls could move civil engineering in a new direction. They incorporate more robust environmental considerations into the planning stages as they collaborate with other specialists, such as soil experts or geoengineers. Using natural additives or vegetation may also be combined with other materials, such as concrete blocks, to enhance their ecological benefits while mitigating mechanical drawbacks.
Embracing a Life Cycle Approach
Ultimately, there is a way to make each material more sustainable for retaining walls. Experts can utilize new technologies — such as low-carbon, self-healing concrete — to reduce emissions. They can use sealants to increase the lifespan of timber. Professionals may also leverage nature-based or recycled solutions to support a circular economy.
Diverse solutions are necessary to support the supply chain for retaining walls, and every effort to decarbonize matters. Eventually, experts will begin defaulting to more eco-conscious options, which will help retaining walls become dependable fixtures for climate mitigation and environmental control.
Author
Grace Waters
Always inspired by the natural world around her, Grace grew up
exploring tide pools and hiking mountain trails, developing a deep appreciation for biodiversity and conservation. Now, Grace works as the Senior Editor of Environment.co where she covers topics related to emerging clean technologies, zero-waste initiatives, and the intersection of environmental policy and everyday living.
