Welcome back to our series on Sustainability in Landscapes! This month we are focusing on hardscape materials -- anything in your landscape that is "built" rather than "planted."
Imagine redesigning your patio and realizing that your choices could either contribute to carbon emissions or actively support local ecosystems. What if you could turn old materials into something new instead of sending them to a landfill?
Have you ever thought about the environmental impact of your patio or other hardscaping? Not only in the way it impacts the ecology of your back yard, but the cost associated with manufacturing, transporting, and installing the materials? We're talking about water use, embodied energy and carbon, fuel burned to transport and install them. Not to mention adding more surface area that causes additional stormwater runoff. And what if you're re-doing your old hardscaping.... what happens to all of those waste materials?
I'd like to share with you some newer ideas in sustainable hardscaping, as well as some inspiration for reusing materials on site.
Choosing Sustainable Hardscape Materials
Hardscape materials, their manufacture, transport, installation, and disposal impact the environment in terms of air pollution, water contaminants, energy consumption, carbon release, deforestation, etc.
I'm guessing the most commonly installed hardscaping material is pre-cast concrete pavers and blocks for patios and retaining walls. Did you know that these have 2 1/2 times the embodied energy than even poured concrete? Embodied energy is the amount of energy used over a product's lifetime in terms of raw materials acquisition, manufacturing, transportation, use, and disposal. Concrete accounts for 7-8% of all CO2 emissions in the US. Another metric used to calculate the sustainability of a material is embodied carbon. This measures the amount of CO2 released during all phases of a product's lifecycle including the fuel burned in the processing and transportation these products.
While concrete is widely used, alternatives like locally sourced stone, reclaimed brick, or other natural materials significantly reduce emissions and waste. Another natural choice is wood decking rather than composite. Check out some options available from Robi Decking, manufacturer of lumber and end grain flow pavers using heat-treated black locust.
Another strategy is to minimize the quantity of materials required - by reducing the area of your hardscape surfaces to just the amount you really need for daily use. The other benefits of this strategy are of course, less cost for the homeowner, and more room for plants that actually have positive impacts on the environment.
Local impact can be further mitigated by using what we call "permeable" materials - they allow stormwater to soak through into the soil rather than running off. This can be achieved with using permeable pavers, bricks, or flagstone with open joints instead of mortar in between. Even better, using an aggregate such as pea gravel is the ultimate in permeability. These materials not only reduce runoff but can also help homeowners comply with stormwater management regulations and prevent erosion in flood-prone areas. Bonus points if your materials are locally sourced, as this reduces transportation emissions and helps support your local economy. Double bonus points if they have been recycled from another project!
Building retaining walls can also have a very high environmental impact. The use of gabion walls (filled with construction rubble and faced with a more aesthetically appealing material) or even planted crib walls have a much smaller impact. If you are removing existing hardscaping, gabions can be filled with the waste material and eliminate the need to transport and dispose of it in the landfill.
Beyond choosing sustainable new materials, one of the best ways to minimize environmental impact is to repurpose what’s already on-site.
Repurposing Hardscape Materials: Reducing Waste
Apiary Studio is one of the industry leaders in pushing for more sustainable practices in landscaping. They have used recycled curbing, chunks of concrete from sidewalks, and other similar materials to create new garden spaces. Check out this project where they re-used existing pavers plus pea gravel to expand their client's hardscapes and gardens.
Local firm Potted Luck Landscape has used recycled materials in their client's projects as well. Take a look at this decorative path edging created by using broken-up chunks of concrete -- it creates an interesting feature reminiscent of a mountainous landscape. Even the bench seating is made from re-used concrete. In another instance, Potted Luck re-purposed factory ductwork into large planters on site.
Repurposed materials may also be used for steppingstones, drainage features, and entire new patios. Even asphalt and concrete can be sliced up and used as garden bed edging - either in chunks or cut slabs.
At the extreme end of keeping building materials on-site and out of the landfill we have Wagon Landscaping in France. In one project an asphalt parking lot was broken up and plants were installed directly into the cracks (with the addition of just a bit of soil), creating a temporary public park. In another, mixed building materials were used to create an artistic "rock garden" stye focal point.
While that is an extreme example, it is always best to keep all materials on site in some way. The next best thing is to find someone else nearby who can use your materials and keep them out of the landfill.
What Local Landscape Installers Say
Locally, current demand for sustainable solutions varies. While larger installation companies may not get a lot of direct requests from consumers for repurposing or using eco-friendly, more niche companies have clientele more interested in supporting local ecology and using environmentally conscious materials. These customers are making the choice to spend more to support their values.
Sustainable choices are generally not the most budget-friendly option. The materials are more expensive and require more skill (and time) to install but also tend to be trend-proof and longer lasting. The patina that develops on these materials over time through the growth of moss and lichens adds to their beauty and value. For Mike Elston of EarthWorks Landscaping & Construction (a one-man crew), using natural materials are such an important value to him, that he offers little else in his practice:
"For hardscapes, we lean into natural stone and real clay brick, both of which are abundant in Pennsylvania, for the less impactful manufacturing processes and the reduced trucking distances needed to get them to our sites. These materials also tend to be more durable and less vulnerable to trend changes over time, so they offer a longer lifespan as compared to precast concrete hardscape materials. There is an inherent need for trucks and heavy equipment in hardscape construction. By working almost strictly local, we keep to a minimum the total annual mileage and subsequent costs and emissions."
Mike's recommendation for eco-friendly material is Pennsylvania bluestone:
Quarried less than 200 miles away, this abundant resource has been an architectural workhorse in the northeast for hundreds of years. From wall stone to flagstone to stair slabs, the variety of applications is hard to beat. And because there is no concrete involved and only short distance hauling, the environmental impact of bluestone production is fundamentally less than that of precast concrete materials.
Earthworks also uses a lot of repurposed building stone, from salvaged barn foundations to granite curbing and cobblestone, which are plentiful in our area. However, repurposing materials can at times double the labor involved in the project. Stone or brick must be dismantled, cleaned, and stored until ready to use. The cost of purchased recycled materials will reflect this extra labor to obtain them.
Elmer Fisher of Potted Luck Landscapes, a larger installation firm, installs a lot of permeable pavers to reduce stormwater runoff, re-uses boulders on site, and tries to recycle concrete that is being removed or replaced. They mitigate excess materials by being very meticulous in the ordering process and storing any leftovers for future projects. He enjoys re-using materials found on site like in the planters shown above, or as art installations.
Elmer says when presenting new ideas to clients, creating plenty of visuals is a key for helping them understand how materials will be used in their landscape. His advice for homeowners and designers:
Think outside the box. That’s how trends arise - find something that speaks to your creativity and be open to pivoting if needed.
Conclusion
While sustainable hardscaping can require more time and investment upfront, it pays off in durability, aesthetics, and environmental benefits. By choosing materials wisely, we can create landscapes that are both beautiful and responsible.
If you'd like to nerd-out and deep dive into the nitty gritty of the impact of different materials:
The carbon impact of a site can be evaluated by using tools such as Carbon Conscience, which can help determine which material choices can reduce the impact of a project.
You can learn more about the embodied energy and carbon of different landscape materials in sustainable-design expert Meg Calkin's presentation to the Landscape Architecture Foundation here. Meg is a professor at NC State, a founding member of the Sustainable Sites Initiative (SITES) and author of The Sustainable Sites Handbook. Look for her new book coming out in a few months Details and Materials for Resilient Sites.
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