Transportation

Transportation from the movement of building materials represents only a small fraction of total fossil fuel consumption of a structure. For a typical wood-frame house in Minnesota (see graphic in Manufacturing section of this course), construction transportation constitutes only 3.6 percent of total fossil fuel
consumption.¹¹

In the case of wood, typically, harvested logs are transported by road to the mill, though often further transport by rail and ship is necessary. Timber is relatively light compared to other materials and can require less energy to transport than concrete and steel.

Limestone, the main ingredient in cement, is very common around the world, and the concrete industry claims that because it can be processed locally, the amount of energy needed to transport the cement from the plant to the construction site is minimal. According to the Concrete Joint Sustainability Initiative, the average distance in the U.S. between a ready-mixed concrete plant and a project site is 14.2 miles.¹² Wood and steel products, on the other hand, typically travel hundreds or even thousands of miles. Concrete transportation is mainly by truck, including transport for cement, admixtures and aggregate. Ready-mixed concrete is delivered to the job site in a liquid-concrete carrier, which typically has the same characteristics as a medium-heavy truck.

Most iron ore, the key ingredient in steel, is extracted in Australia and Brazil, carried to dedicated ports by rail, and then shipped to steel plants in Asia and Europe. Iron ore and coking coal are primarily shipped in huge bulk carriers that can hold a cargo of 154,300 tons or more. Due to its weight, steel is high in embodied energy when transported over large distances.

While it may seem somewhat counterintuitive, transportation impacts are not a function of distance—a product travelling a long distance in a highly efficient mode will actually have a smaller environmental footprint than a product with fewer miles to travel in an inefficient carrier. According to Helen Goodland, Managing Partner of Brantwood Consulting (a green building technical advisory firm in Vancouver), road transport is by far the most carbon-intensive option, and is about six times more energy-intensive than rail transport, and 15 times more than sea transport. Goodland cites LEED®'s values of shipping by truck (1,381 BTU/ton-mile); rail (242 BTU/ton-mile); and ship (90 BTU/ton-mile). "So shipping 1 ton of wood from Seattle to Seoul (roughly 5,000 miles) is about the same energy-wise as driving 1 ton of steel from San Francisco to Los Angeles (380 miles) in a truck," she says.

A report on Japan's Woodmiles system corroborates the same principle, maintaining that "0.62 miles of truck travel is equivalent to 20 miles of ocean travel on a bulk carrier."¹³ The report, which is concerned with the transport of lumber from Canada to Japan, states that instead of doubling Japan's self-sufficiency in logs, a faster way to attain the same CO2 reduction would be to shift some of Japan's imports from Canadian logs to Canadian sawn lumber, which is less dense and lighter to transport. In addition, the report indicates that while transportation impacts are not a function of distance but of mode of transport, the type of product being transported is also a key factor. Transport of wood is ultimately offset by the carbon sequestration properties of wood.

Renewable Versus Recyclable

Recycled wood can add beauty and aesthetic appeal to furniture design. Source: Wood Anchor, http://www.woodanchor.com

A natural resource is renewable if it can be naturally replaced at the rate at which it is consumed. When the sand and gravel in concrete are mined from an area, they will not be replenished naturally in a reasonable time. Likewise, iron ore, the primary ingredient in steel, will not be replaced in a timely manner. Of the three building materials, wood is the only renewable resource.

Recyclability is another matter. All three materials are recyclable. Steel is said to be the world's most recycled material; in the U.S. more than 80 million tons of steel are recycled each year and the overall recycling rate for 2011 was 92 percent.¹⁴ Steel mills use one of two types of furnaces to make new steel—both recycle old steel into new steel, but each is used to create different products for varied applications. According to the Steel Recycling Institute, the basic oxygen furnace uses a minimum of 25 percent steel scrap to make new steel used in flat-rolled steel products like cans and appliances. The electric arc furnace process melts virtually 100 percent steel scrap to make new steel used to make steel plate, rebar and structural beams. When one ton of steel is recycled, 2,500 pounds of iron ore, 1,400 pounds of coal and 120 pounds of limestone are conserved; however, the worldwide demand for steel outstrips the supply from demolished or scrapped steel. Steel can also be reused. The industry claims that steel frames with bolted connections can easily be dismantled and reused. Entire structures are easily demountable and can be dismantled and reconstructed in a different location in a matter of days, without creating any dust and dirt, and very little noise.

Concrete, too, is said to be 100 percent recyclable. Increasingly, recycling is becoming an accepted way of disposing of concrete structures that were once routinely shipped to landfills. Typically, concrete is collected and put through a crushing machine, often along with asphalt, bricks, and rocks. In reinforced concrete, the rebar is removed with magnets, and the remaining concrete chunks sorted by size. Smaller pieces of concrete can be used for gravel for new construction projects, or in shoreline protection or even as a road base.