Environmental concerns with composite decking boards

As an eco-friendly approach becomes the norm in architecture, environmental groups encourage using composite decking boards for Broadwalk projects. However, contrary to what these groups assert, buying composite decking has a negative effect on the environment. Purchasing lumber, like Black Locust, actually is a more sustainable option. We hope our article will help you make a well-informed decision regarding your own home deck or those of others for whom you build quality decks.

#1 concern: Renewability of composite decking

Stating the obvious: composite decking boards are not organic products. The term “composite” means the material is composed of several artificial materials. These materials include polypropylene and polyvinyl and are obtained as byproducts of oil refineries. 

Oil refineries’ manufacturing process is notoriously unfriendly towards the environment.

The reason why most people believe composite decking boards to be sustainable is due to the fact that these products put waste to use. This on its own, certainly sounds environmentally friendly and they might rightfully claim to use recycled material. The problem is that the very same waste comes from extremely damaging environmental processes.

#2 concern: End-of-life biodegradability

Let’s take a step back from the concerns surrounding the manufacturing of composite decking products and consider what happens when the deck is destroyed or needs to be replaced. Manufacturers pride themselves on these decks lasting a lifetime.

Black Locust Lumber material
Black Locust Lumber material is biodegradable

Unfortunately, these non-biodegradable composite decking boards are unable at his time to be properly recycled.

The natural wood fiber within the composite material cannot be separated from the plastic composition. Currently, until a technology to separate these components is developed, the composite decking becomes entombed in the landfills.

Physical Properties Comparison of Black Locust lumber and Trex composite decking boards

Black Locust Trex Composite wood
specific gravity0.69 0.91 to 0.95 
density (Lbs/ft3 )43
max tensile strength (perpendicular to grain) (psi)1,700854
max crushing strength (psi)10,8001,806
modulus of rupture (psi)19,4001,423
modulus of elasticity (MPa)14,1001,2
decay resistance1 – very resistant 2 – resistant 3 – moderately resistant1-21
manufacturing and delivery processfelling, milling, shipping, air, and kiln drying,producing a composition of 50% wood and 50% plastic fibers 
Construction Material Properties: Physical Properties Comparison of Black Locust lumber and Trex composite decking boards. Source: ASLA (November 1, 2011) 

Alternative: Black Locust lumber as a sustainable alternative to composite decking boards

Black Locust lumber is a sustainable alternative to composite decking in both renewability and biodegradability.

Black Locust lumber is unique as the tree can be harvested for commercial production at 35 years. The longevity of lumber from the same tree can easily reach 50-100 years in service. Black Locust Lumber with NO toxic chemicals or unnecessary surface treatments can stand the test of time naturally.

Black Locust seedling
Black Locust seedlings allow the tree to reproduce extremely quickly

Black Locust wood decking also has the advantage of being able to be disposed of in an environmentally-friendly manner whenever it has reached the end of its life span. In contrast, at the present time, with composite decking boards, Black Locust wood decking can be repurposed for alternative use.

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