Wood vs. plastic vs. metal furniture and other items, is the wood product generally most environmentally friendly?

Question

Consider a bed or a chair, one made of wood, another of plastic, another of metal. All else being kept similar between the materials to the extent feasible, is the wood product generally the most environmentally friendly?

Each material has a method of production, a supply chain and equipment and fuel and waste involved. Wood is the most renewable resource, as the wood can regrow and forests provide lots of benefits. Depending on forest management, the supply chain and overall effects of using the wood might not even be bad, aside from probably using tons of fossil fuels if it's not an artisan craft.

Plastic and metal on the other hand both require more extensive processing I imagine, and both are less renewable resources. Metal is finite (though plentiful for many types) and I imagine more costly environmentally to mine and extract vs. growing, living forests. Plastic is not only using fossil fuels in production processes, but also in the very materials plastics are made up of.

In terms of environmentally friendly, there are a lot of angles to look at it. Lower impact on air quality, less net carbon in atmosphere, socio-economic aspects of production and supply chain, environmental externalities (positive and negative) from the different material options.

Answer 1

Wood is the best choice for furniture from an environmental perspective, and substituting wood where possible for other products would have a net environmental benefit.

2003 review of available studies

A good starting point is a review produced by the Australian government in 2003 which looked at about a dozen different studies including life cycle analyses (LCAs) of both furniture and building materials:

• Review of the Environmental Impact of Wood Compared with Alternative Products Used in the Production of Furniture Australian Government Forest and Wood Products Research and Development Corporation. 2003.

From the abstract:

• In all the examples studied, wood has been found to have the lowest environmental impact compared to other materials.
• Timber from sustainable forestry practices is a renewable resource whereas the production of plastics and metals is not.
• The incineration of timber for energy production can be regarded as CO2 neutral.
• The use of other materials in the production of timber furniture (such as metal and plastic trimming, glues, varnishes etc) drastically increases the environmental burden of the furniture.

Furniture and construction materials industries in Switzerland

• Life Cycle Impacts and Benefits of Wood along the Value Chain: The Case of Switzerland Florian Suter, Bernhard Steubing, and Stefanie Hellweg. 2016.

This study aggregates LCAs from all wood products produced in Switzerland, and all feasible products that wood could replace. First the authors categorize how wood is used:

In Switzerland, most of the wood is utilized in energy (approximately 50%) and paper production (approximately 25%). The remaining share goes into the production of various commodities, namely, buildings (approximately 10%), furniture (approximately 3%), and packaging (approximately 3%).

Going further, they identify

52 processes that produce 40 wood-based products covering the different sectors of the wood market up to semifinished products.

For each process and product, the production impacts of wood and a substitute product were compared. (Paper was not included in this comparison due to limited availability of equivalent substitutes.)

End-of-life treatment (EOL) for each product was also estimated based on research on waste streams from Zurich (Switzerland's largest city, with a metro area population of 1.8 million). For each product, an average percent sent to landfills, recycled, or incinerated was calculated.

Finally, the LCAs and EOLs for all products and substitutes was compiled:

Interpreting the chart:

The chart shows the climate impact of wood use in three scenarios. Positive numbers show increasing global warming potential (GWP), and negative numbers show reduced GWP -- in this case, negative numbers are better.

The three scenarios (minimum benefit, likely benefit, and maximum benefit) represent different levels to which wood is used to substitute for other products. The blue line shows the net effect of wood use in each scenario.

Within each chart, the rows represent:

• Impacts from the production of wood products
• Impacts from wood product EOL treatment
• Net impacts from using wood in place of other products
• Net impacts from EOL treatment of those wood products compared to the products they replaced

Each color represents a different product that wood is replacing.

From this it is clear that even when wood replaces only a fraction of the alternatives, the net benefit is a decrease in total greenhouse gas emissions.