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Forget creosote-laden railroad ties and drab concrete walkways: Update your landscape with eco-friendly, recycled plastic landscape timbers, dazzling recycled glass mulches to set off your tree island, and walkways made from crushed stone, pavers, and other water-permeable, natural materials.

Find it! eco-friendly landscape materials

How to use eco-friendly landscape materials

Traditional materials used in landscaping include stone, gravel, masonry, wood, and plastic. Newer materials include recycled plastic (for edging and landscape timbers) and recycled glass (for decorative mulches and walkways). The most common landscape materials include:[1][2]

• Stone including fieldstone, rubble, flagstone, crushed stone, and stone dust.
• Gravel differs from stone in industry terminology in that it occurs naturally in small pieces, rather than being quarried and crushed with machines.
• Masonry such as bricks, pavers, concrete, terra-cotta, and adobe.
• Wood including pressure-treated landscape timbers, wood chips, and bark mulch.
• Plastic used primarily for edging, especially in flower beds.

Choosing the right material

Choosing the right eco-friendly material depends on your landscape application. Here are a few suggestions:

• Walkways and paths can be made of brick, pavers, recycled broken concrete, crushed stone, and recycled glass.
• Steps can be contructed from bricks, fieldstone with one flat side, or recycled broken concrete.
• Retaining walls, which help control erosion, can be made from fieldstone, recycled broken concrete, and recycled plastic landscape timbers for retaining walls. Don't use railroad ties, which have been treated with a harmful wood perservative called creosote.
• Terraces, which are two or more retaining walls set into steep slopes. Terraces make it possible to create a flower or vegetable garden if your yard has a steep grade. Stronger materials may be needed for steep terraces, otherwise use the same materials listed for retaining walls.[3]
• Planting beds or islands can be mulched with organic wood chips or bark mulch. Smaller areas can be mulched with recycled glass, which is beautiful but pricey.
• Edging can be made from brick, stone, or recycled plastic.

Concrete

Concrete is a mixture of Portland cement, aggregate (sand and gravel or crushed stone), and water (which binds the cement together). The manufacture of Portland cement is very energy-intensive and releases lots of carbon dioxide—a greenhouse gas—along with toxic mercury, lead, and arsenic. If you must use concrete, reduce its environmental impact by substituting fly ash, a byproduct of coal-fired energy production, for up to 50 percent of the cement in the concrete. Concrete walkways are a good choice for people with impaired mobility and for wheel chair access due to their stable surface. Otherwise, consider using recycled broken concrete, or at least concrete pavers, which reduce runoff. Recycled glass pavers can also be used as a substitute for concrete pavers: they only take about half the energy to manufacture.[4][2]

Bricks

Bricks are made from naturally occurring clay, formed and dried in kilns. In the US, the kilns use natural gas, but companies in some developing countries use wood-fired kilns, which are significant sources of air pollution. Try to find local brick, or at least US-made brick. The harder the brick, the better it is for outdoor use. For brick walls, use bricks sold as "building brick type SW" (for "severe weathering"). For walkways, use bricks called "pavers" which are especially hard and dense. Using recycled bricks is a great idea, but make sure they're hard bricks designed for outdoor use. Bricks that are too soft will absorb water and crack or flake when the absorbed water freezes.[4][2] Terra-cotta and adobe are also molded clay-based products, but they're dried in the sun. Both are eco-friendly but porous and are best suited to use in very dry climates.[1]

Stone

Crushed stone extracted from inland quarries is usually less harmful to the environment than gravel operations, which can disturb sensitive land near lakes and streams. Also, almost 100 percent of the stone from a quarry is used, while significant waste occurs with gravel operations. Try to find stone products from local sources that aren't quarried near lakes and streams.[4] Most eco-friendly: gather your own stone. If you live in an area with rocky soil, your garden will provide lots of stones, from gravel to large boulders. Where do you think all those New England stone walls came from?

Landscape timbers

Most wood used for outdoor residential purposes since the 1970s is pressure-treated wood impregnated with chromated copper arsenate (CCA). CCA, a chemical wood preservative made up of chromium, copper, and arsenic, keeps wood from rotting. CCA-treated wood, which has a greenish cast, is used in landscape timbers, decks, children's play sets, picnic tables, residential fencing, patios, walkways, and boardwalks.[5] CCA-treated wood leaches arsenic and has been linked to serious health problems: Children are particularly at risk. (See Related health issues). Due to the toxic properties of CCA, the US Environmental Protection Agency (EPA) banned the use of the preservative in residential applications in 2004 (with a few exceptions).[5][6]

A healthier alternative to CCA is ammonium copper quaternary (ACQ). ACQ is registered for use on lumber, landscape ties, fence posts, decking, wood shingles, and other outdoor applications. If you must use pressure-treated wood, check out ACQ and other alternatives to CCA. Even when using outdoor wood treated with EPA-approved chemicals such as ACQ, follow the EPA's safety precautions. Your best bet is to avoid the use of wood for purposes such as landscape timbers where wood comes into contact with the ground. For above-ground outdoor applications, choose a naturally durable species that's grown locally and certified by the Forest Stewardship Council (FSC) as being sustainably harvested.

Sealing CCA-treated wood

What can you do if you have CCA-treated wood in your existing landscape timbers, deck, or other outdoor structure? The EPA and the Consumer Product Safety Commission (CPSC) conducted two-year studies to determine whether applying different wood sealants to CCA-treated wood could affect the amount of CCA residue that a person would be exposed to. The studies suggest that application of penetrating stains and coatings to decks or other residential CCA-treated wood at least once a year can reduce potential arsenic exposure.[5] Of course, removing CCA-treated wood is the best option, if replacement cost is not a factor. It's also worth checking for CCA-treated wood if you're buying a home.

Wood chips and bark mulch

Buy natural wood chips and bark mulch, which are byproducts of lumber milling and decompose naturally, adding organic matter to the soil without any harmful chemicals. Don't use mulches colored with artificial dyes, rubber "playground" mulches, or "bark mulches" containing old asphalt roofing. Don't use mulches containing cocoa bean shells if you or your neighbors have pets. To find out why, see Related health issues. For more information on types of mulches and how to use them see Apply mulches.

Using eco-friendly landscape materials helps you go green because…

• Water-permeable gravel, stone, and mulches let rainwater enter the water table where it can be used by plants, rather then emptying into stormwater drains.
• Using FSC-certified wood saves old-growth forests and prevents deforestation.
• Using recycled plastic "lumber" keeps plastic that's already in the environment out of landfills, and eliminates the manufacturing hazards of new plastic.

Using water-permeable paving materials and mulches keeps our water, soil, and plants healthier. Concrete or asphalt walkways and other hardscaped surfaces keep rain from being absorbed into the soil, where it can be used by plants and filtered by the soil before entering the water table. Instead, the unfiltered runoff goes down the drain and directly into lakes, streams, and rivers. Permeable paving and mulches let rainwater seep into the earth, as nature intended.[7]

Using FSC-certified wood keeps forests, soil, water, and wildlife healthier. FSC-certification takes into account environmental, social, and economic criteria,[8] such as harvest rates and clearing sizes; natural forest conditions; rare, threatened, and endangered species; adequate conservation zones; chemical use (minimized); protection of streams and lakes; and the health of workers, communities, and indigenous peoples.[9]

Using recycled plastic landscape materials can lessen the amount of ever-accumulating plastic—in landfills and in the ocean. In the 50 years or so since its invention, over one billion tons of plastic have been produced and except for a tiny amount of incinerated plastic, every single bit of this one billion tons of plastic is still in the environment.[10] Not only do plastics end up in landfills, they also cover large areas of the ocean with floating refuse, including an area of the Pacific Ocean—10 million square miles, or about the size of Africa—which has been dubbed the Great Pacific Garbage Dump: it's filled with industrial flotsam, 90 percent of which is plastic.[11]

Related health issues

CCA-treated wood contains chromium, copper, and arsenic, all of which were found to leach into the soil, and are absorbed and stored by plants—especially a problem if used around food crops. Even more problematic is the fact that arsenic is easily transferred to children and pets who come into contact with CCA-treated wood. Arsenic is a known carcinogen, and repeated exposure increases the risk of lung, liver, skin, and other cancers. If you have landscape timbers, decking, picnic table, or a child's play set made from CCA-treated lumber, never try to burn it: You'll risk breathing in toxic arsenic in the smoke.[12]

Recycled railroad ties used as landscape timbers contain toxic creosote, which is made from a wide range of chemicals, but is usually from coal tar. The EPA has classified creosote as a probable carcinogen. Studies showed an increased risk of cancer and respiratory problems in manufacturing workers repeatedly exposed to creosote. Skin contact can cause rashes and irritation and in an extreme case, cancer.[13] Creosote is not approved by the EPA for residential use.[14]

Mulches

Rubber "playground" mulch was shown by The Connecticut Agricultural Experiment Station to outgas and leach high levels of benzothiazole; butylated hydroxyanisole; n-hexadecane; and 4-(t-octyl) phenol. About two dozen other chemicals were found at lower levels. The toxins released from recycled crumb rubber used in rubber mulch can cause severe irritation of the respiratory system; severe irritation of the eyes, skin, and mucous membranes; systemic effects on the liver and kidneys; neurotoxic responses; allergic reactions; cancers; and developmental effects.

Mulches made from old asphalt roofing waste were tested by Oregon's Oregon Department of Environmental Quality (DEQ) in 2004. The results showed levels of contaminants in quantities of concern for human health and aquatic life, specifically unsafe levels of polycyclic aromatic hydrocarbons (PAHs) and arsenic. Arsenic and several of the PAHs are classed as probable human carcinogens by the EPA.[15]

Cocoa bean shells, sold as mulch, are a byproduct of chocolate production. Dogs are sensitive to theobromine and caffeine, chemicals called methylxanthines. Dogs who eat cocoa bean shell mulch could develop methylxanthine toxicosis, the signs of which are similar to those in chocolate poisonings. Vomiting and muscle tremors are the most common symptoms. Other symptoms include rapid heart beat, hyperactivity, and diarrhea.[16] Horses are also sensitive to theobromine, but cattle are less so. Cats are somewhat sensitive, but are "more discriminating in their diets" [than dogs].[17]

For more information on the health risks of mulch products see Related health issues in Apply mulches.

External links

• NBC Nightly News - Sustainable logging uses "waste not" ethic Watch this NBC Nightly News segment on how one company practices sustainable logging and produces FSC-certified wood. See for yourself the difference between what a clear-cut and a sustainably managed forest looks like.
• Beyond Pesticides -Chromated Copper Arsenate (CCA) Treated Wood If you think your home or landscape contains CCA-treated lumber, read this detailed fact sheet and find out everything you need to know: how to identify CCA-treated wood, testing your soil for CCA, and the health and environmental risks of CCA.
• Debra Lynn Dadd - Green Living Q&A For more information about the safety of pressure treated wood, and why the EPA issues safety guidelines even for ACQ-treated wood, read this informative discussion.