Construction material recycling is critical to reducing the total quantity of the waste stream. In areas where new construction or renovation is brisk, the impact on local landfills and other solid waste facilities is major.
Percentages of total solid waste in the landfill attributed to construction activity vary from 15% on the low side to 30% or higher in communities that are growing or rehabbing buildings rapidly. In addition to these impressive quantities that can be kept out of the landfill, another advantage of reducing building material waste is that behavior change on the part of just one industry and relatively few individuals can make a major impact on the total quantity of municipal waste.
Like all recycling, an even better alternative is direct salvage and reuse. This topic is discussed near the end of this page.
Obviously this topic is closely interwoven with green home construction. Leftover drywall, lumber, and metal studs and other items can be recycled, although not every city will have a convenient recycling plant able to handle these materials. Recycling of the large quantity of boxes that accompany new construction is feasible in almost all new construction projects, however.
If demolition occurs prior to new construction, the options may be even greater. Concrete foundations, wooden structural members and doors, and walls from the demolition process can be recycled. Storm damage may limit the feasibility of recycling in a particular demolition situation, but at other times a little extra care in the demolition process will reduce the amount of landfill capacity needed.
Asphalt shingles are estimated to account for about a third of
construction wastes reaching landfills. Both the torn-off and worn-out
shingles and the leftover new shingles from re-roofing jobs can be
ground and then analyzed for incorporation into a hot asphalt mixture
used for most paving jobs of any size.
This is a particularly important example, since asphalt shingles might contain as much as 35% asphalt cement in them, a key ingredient required for new asphalt paving. Asphalt from demolished driveways can be recycled also. Even if the existing driveway will be refurbished, almost any asphalt plant with the will to do so can incorporate the "millings," which means the part of the asphalt pavement shaved off the top prior to re-paving, into the hot mix for new asphalt.
Recycled concrete is acceptable as a source of aggregate, an important ingredient in making new concrete. Recently standards for incorporating recycled concrete have been set by the American Society for Testing and Materials (ASTM) and American Association of State Highway and Transportation Officials (AASHTO).
Sources for concrete that could be recycled include former concrete roads, curb and gutter systems, airport runways, or building foundations. There seems to be less experience with recycling concrete than asphalt, so significant learning on the part of the industry still is needed. Crushed concrete also can be used as aggregate alone, what most of us would call gravel at our homes.
Recycled drywall is used in the manufacture of new drywall.
Alternatively, it can be an ingredient in cement or fertilizer. There is
a fairly low rate of drywall scrap recycling, but if you've ever done a
major home remodeling project, you probably can testify to the fact
that there are actually a number of leftover odd pieces. To date most
of these are headed for the landfill, and the contractor must pay for
All of the above depend on education and persuasion of construction contractors and "do-it-yourselfers" about the importance of recycling to society, or to their pocketbooks if the contractor can do their own recycling. Homeowners also can be helpful through taking advantage of local opportunities to recycle building materials.
In addition to the recycling option, some leftover construction material or waste from a demolition process is suitable for re-use without any further processing. Where feasible, the practice of re-use and re-purposing benefits the private sector. This practice reduces the quantity of new materials needed, saving both the costs of mining or manufacturing of the construction materials and the energy involved in transporting those items.
The problem with advocating for re-use is that many contractors do not want to take the time to sort out materials suitable for re-use and then allocate the space to store them until the appropriate situation comes along. In some fast growth communities, it may be worthwhile for the public or non-profit sectors to invent an online system or finding a warehouse for swapping these odd lots of building materials to facilitate re-use.
In many communities Habitat for Humanity offers ReStore, a place where building supply stores, contractors, demolition companies, and individuals donate surplus salvaged items and construction materials, which Habitat in turns resells in a retail format at a fraction of the cost of new supplies.
Architectural salvage ventures should be encouraged in cities where there is a considerable amount of demolition of older buildings that may be sources of unique doors, stained glass windows, mantles, millwork, pulpits, bars, and many other building elements. When we say they should be encouraged, we mean that the public sector needs to go out of its way to help the salvage operation obtain permits and gain traction.
Other local versions of construction material recycling may be in operation in your area. In Portland, latex paint recycling leads to blending of paints for re-sale. Metal recycling is plentiful in any large community.
Like many less familiar materials recycling ventures, lack of information about how and where interested parties can recycle, as well as the small inconveniences involved, contributes to a low rate of recycling.
For more information, the Construction Materials Recycling Association offers specialized sites for concrete, drywall, and shingles. New recycling enterprises are emerging at a fast pace, so it is worth checking them out.
We don't want to leave the impression that the only value of construction material recycling is reduction of volume in the landfill. We should emphasize that the very best policy would be to reduce energy use, greenhouse gas emissions, and our carbon footprint in general through not manufacturing or transporting unnecessary items, refusing to demolish what can be renovated or adaptively reused, and then recycling what cannot possibly be reused.
So even though we're on a page that advocates for construction material recycling, preventing waste generation is perhaps an even more important strategy.