An adobe house under construction in a Lakota Sioux community in South Dakota, with assistance from the Yestermorrow Design-Build School. Material for these adobe blocks came from the earth that was moved to make the driveway.
Photo courtesy Yestermorrow
Using materials from local or regional sources is high on the list of many green designers and builders. Several high-profile projects, such as the new laboratory designed for Montana State University, have made it a priority to source materials from within a limited radius of the site, and many small-scale owner-builders do likewise.
Using local materials has the obvious benefit of reducing the significant environmental impacts of transporting materials long distances. In the eyes of many, it has some less tangible benefits as well, such as encouraging vernacular building styles, supporting the local economy, and connecting users directly with the impacts of their choices.
There are also some trade-offs that can come with the decision to use local materials, however. Large, centralized plants may make more efficient use of raw materials; they may have more sophisticated pollution controls; and they are more likely to generate by-products in sufficient quantity to justify investment in symbiotic industries that can utilize them. Companies that prefabricate components—or entire buildings—often argue that they generate less waste material than contractors who cut and assemble everything on site. Finally, the material’s performance over its useful life in a building is important, especially with components of the building shell, which can affect energy use for the life of the building. To determine whether a local material really is the best choice for a specific application, we need to consider these trade-offs. This article provides some fodder for that process.
1.Includes all trucks used to carry freight. Efficiency for tractor-trailer trucks alone is higher.
Sources: Truck, railroad, and barge data from The Transportation Energy Data Book: Edition 15
, Stacy Davis, editor, Oak Ridge National Lab, Oak Ridge, Tennessee. Ship data (for oceangoing vessels) from the Total Emission Model for Integrated Systems by the Institute for Applied Ecology, Germany.
The energy efficiency of various modes of transport is generally expressed in terms of the amount of energy required to haul one ton of material one mile (Btu/ton-mile or kJ/tonne-km). Alternately, for a given fuel, comparisons can be made in terms of ton-miles per gallon (or tonne-km/liter).
Table 1 shows average energy data by transportation mode. The energy used for transporting materials depletes reserves of fossil fuels, contributes to the global problems of spills and contamination that come with the extraction and transport of those fuels, and, most significantly, releases pollutants into the atmosphere. In addition, from a lifecycle perspective, fuel consumed carries the additional burdens of the energy used to extract, transport, and process that fuel.
The air pollutants that traditionally have been of concern in connection with internal combustion engines are carbon monoxide, nitrous oxides, and particulates. In the U.S., as in many other countries, federal emission control requirements have dramatically reduced emission levels of these pollutants over the past two decades. With more recent concern about global warming, a new category of pollution is taking center stage: greenhouse gases. The most prominent greenhouse gas is carbon dioxide (CO2), which is an inevitable by-product of the burning of fossil fuels.
Whether based on a gut-level intuition or on carefully considered choices, the preference for local materials is strong among some builders. Arizona-based straw-bale construction pioneer Matts Mhyrman reports having been offered bales from Oregon at a lower price than the cost of local bales. Mhyrman refused the deal because, in his words, “the true cost of transporting the bales wasn’t included in the price.” Mhyrman was expressing a common sentiment that the real cost to society of fossil fuel use for transportation is much higher than the actual monetary cost in purchased fuel and road use taxes. These costs include lost productivity and health from air pollution and the likely effects of global warming. Of course, environmental problems related to transportation are not limited to fossil-fuel use. Roads compromise wildlife habitat and use up arable land, while traffic creates noise pollution. (For more on the adverse environmental impacts of transportation see EBN Vol. 5, No. 1, “Transportation Planning: It’s Time for Green Design to Hit the Road.”)
Transportation and embodied energy
Energy use and pollution are inevitable in the manufacture of any building product. In order to determine how much emphasis to place on avoiding the transportation of materials, it makes sense to begin by getting a sense of how significant a fraction of a material’s total embodied energy comes from the transportation component. Of course, reducing energy use and the resulting air pollution isn’t the only reason to reduce transportation, but it is perhaps the most important single factor.
Source: Jamie Meil, JKM Associates, using the Athena™ database of building material lifecycles in Canada developed by Forintek, Inc. Data include energy used to transport raw materials and energy used to deliver finished products to construction sites.
Source: “Comparative Energy Evaluation of Plastic Products and Their Alternatives for the Building and Construction and Transportation Industries,” report by Franklin Associates for the Society for the Plastics Industry, 1991.
Transportation occurs at several stages in the manufacture of a product. Raw materials are collected and transported to the primary processing site. In some cases, there are intermediate products, which are moved to secondary or tertiary manufacturing locations. Finished products are then delivered to central distribution points and from there either to local supply outlets or directly to building sites.
One of the more careful studies of these flows on a national scale is the Athena project by Forintek in Canada (see Table 2).
Many factors affect the particular steps a product or material might take along this chain or the distance it will travel. Just because a material originates from a local source, one can’t assume that it hasn’t traveled a long way for processing. Some domestic granite, for example, is shipped to Italy for finishing, even if it will ultimately be used on a building near the quarry. And some oak and birch veneers are shipped to Indonesia or Malaysia for laminating onto lauan cores before being returned to the U.S. for sale as “domestic” plywood.
A 1991 study by Franklin Associates of Prairie Village, Kansas, also provides information on transportation energy use (Table 3).
The transportation data is presumably based on typical U.S. distances and modes of transport for each material, but the actual assumptions were unfortunately unavailable. Like the Forintek figures, these data include energy use for both raw material and finished product transport.
A recent German study analyzing the energy use in the lifecycle of a prefabricated house provides some data on energy use for transportation as a percentage for a whole structure’s energy use. The researchers, Runa Hellwig and Hans Erhorn of the Fraunhofer-Institut für Bauphysik in Stuttgart, separated out the raw materials preparation and delivery stage from the factory production and site erection stages of construction. They found that transportation constituted 21% of the energy used in the first stage, and 38% in the second. Combining both stages, transportation energy was found to account for 24% of the total production and construction energy. Putting these numbers in a larger context, the researchers also estimated energy use over the home’s projected 80-year life (based on Germany’s relatively stringent energy codes), and the energy use for its eventual demolition. As might be expected, heating energy use for 80 years dwarfed all the other figures. Transportation from both production stages taken together contributed only 1.6% of this total lifecycle energy load.
Studies done by students in the Center for Building Performance at Carnegie Mellon University’s Architecture Department found that transportation of materials and products constituted about 20% of total energy use for construction of the Center’s “Intelligent Workplace” demonstration project. This figure omits the transportation of raw materials to the original product manufacturers, however, because accurate information on the sources of those raw materials was not available. Looking at some specific materials, the students found that transportation of relatively local steel represented 18% of its total production energy, while for steel from further away the portion was 23%. For a glazing product, which came from a distance in several stages, transportation accounted for about 35% of the embodied energy.
The numbers from these studies vary somewhat due to differing methodologies and different circumstances in each country. In general, however, the studies suggest that the fraction of product manufacturing energy attributable to transportation is in the range of 3% to 5% for the very high embodied-energy materials (plastics, aluminum) and 10% to 30% for other materials (Tables 2 & 3). Given that the very high embodied-energy materials represent a very small fraction of the total mass of materials that go into a building, the range of 20% to 25% for transportation energy as a portion of total construction energy is a reasonable estimate.
As carbon emissions are directly proportional to fossil-fuel energy use, transportation also represents one-fifth to one-quarter of total CO2 emissions from the manufacture of buildings. Due to the nature of diesel fuel emissions, the portion of some air pollutants attributable to transportation is actually much higher. According to the modeling done at Carnegie Mellon, transportation accounted for 65% of the nitrous oxide emissions in product manufacture and construction, and over half of the particulate emissions.
Much of the transportation impact is in the short hauls
With a few notable exceptions, such as some rammed-earth and adobe projects, all materials used in buildings are transported at least a short distance to the building site.
These short hauls generally represent a disproportionately large share of total transportation impacts, however, for several reasons. First, short hauls are almost always done in trucks, as opposed to rail or ship. Second, because the trucks used for short hauls are smaller than those used for long hauls, proportionately more of the energy is used for moving the truck itself. And third, because short hauls are typically over secondary roads with a lot of stopping and starting, efficiency is reduced. Given all these factors, the total environmental impact of hauling materials 1,000 miles by train to a supply yard may be less than the impact of hauling materials 100 miles by truck to a job site.
When it comes to making specific choices, it may help to look at actual data for the materials in question. For example, flyash, a by-product of coal combustion, is often suggested as a replacement for at least some of the cement in concrete. If one assumes that flyash has no embodied energy (as a waste product of another industry, no energy was invested for the purpose of producing it) and that cement production requires 5,800,000 Btu/ton (6,700 MJ/tonne), one could transport the flyash 2,000 miles (3,200 km) by truck or 17,000 miles (27,000 km) by rail for the same amount of energy. In some cases, a high embodied-energy local material, such as cement, may not be preferable, at least in energy terms, to a low embodied-energy material from afar.
There are many less tangible arguments for preferring local resources. Some suggest, for example, that sourcing materials locally makes the impacts of extracting and processing the resources immediately visible to the user. If one sees the forest being cleared or the hillside being mined, this theory says, one is likely to consider those impacts more carefully in making design decisions.
While it makes sense that such direct feedback would be more influential than the impacts of some distant mine or logging operation, history is littered with examples of local resources being wiped out by the local people. These resources fall prey to a combination of general shortsightedness—not looking ahead to the consequences of our actions, as exemplified in Garret Hardin’s “The Tragedy of the Commons”—and the frontier mentality, which holds that if this local resource is depleted, we can always move on to the next virgin source. What’s needed, according to research architect Pliny Fisk of Austin, Texas, is sustainability thinking in conjunction with the direct feedback of local material use. The bad news, according to Fisk, is that no past or present culture studied by anthropologists has been found to exhibit a truly sustainable approach to resource use. The demise of the population on Easter Island, described in EBN Vol. 4, No. 5, is but one example of local resources being depleted to the point of catastrophe.
Another argument for local materials is that they are inherently consistent with the indigenous architecture of a region. Regional architectural styles evolved before the advent of large-scale transportation, at a time when local materials were the builders’ only palette. Just like our massive transportation infrastructure, the widespread construction of climate-blind, energy-hogging buildings has developed with the advent of cheap fossil fuels.
From the wide-porched houses of the deep south to the massive adobe buildings of the Southwest and the south-facing, wood-framed saltboxes of the Northeast, there are examples in every region of climate-responsive structures, all of which were originally built almost entirely of local materials. While using local materials won’t necessarily lead to more climate-responsive and energy-efficient buildings, there is certainly a connection to be nurtured. At the same time, it doesn’t make sense to ignore the recent developments in insulation, window glazing, and other modern materials that contribute to energy-efficiency in buildings, even if some of these materials are not manufactured locally.
Economies: global or local?
Aside from all the transportation impacts discussed above, using locally produced materials tends to keep money circulating in a local economy, rather than having it drawn off to a remote location. In the global market, money is drawn to investments that provide the biggest return for investors, rather than the needs of particular communities. Most environmentalists feel strongly that the increasing pressure towards globalization of markets is not good for many small communities, nor for the global environment. Although they strongly support the Clinton Administration on most issues, the mainstream environmental groups took issue with Clinton’s commitment to the North American Free Trade Agreement (NAFTA) and the General Agreement of Tariffs and Trade (GATT).
Steelmaking requires a relatively large scale for efficiency.
Photo: American Iron and Steel Institute
Environmentally, however, there are some strong arguments in favor of large-scale, centralized production in some industries, at least if one accepts as a given the need to manufacture the products in question.
Energy-intensive industries such as steel and glass manufacturing are more efficient and less polluting in midsize-to-large plants than they tend to be in small, community-scale or backyard operations. And the manufacture of some energy-saving products, such as low-e coatings on window glass, requires sophisticated equipment that is not economically viable on a small scale.
Another disadvantage of localized production is that wastes and by-products of a process may not be generated in sufficient quantities to justify the cost of collecting them for use in other processes, as might occur at a large facility. Often the value of these wastes as raw materials is relatively low, and the expense of collecting and transporting them from multiple locations is prohibitive. For example, steel slag is used to make mineral wool insulation, a process that might not occur if steel were produced in smaller, more distributed facilities.
Finally, the sophisticated pollution control equipment required to trap many air and water emissions is often only economically viable on large facilities. For example, the wood dryers at plants making oriented-strand board are increasingly being fitted with electrostatic precipitators that can remove nearly all the pollutants from the dryer exhaust. These precipitators cost hundreds of thousands of dollars to install and operate, so they are not an option for small-scale drying operations.
In contrast to these possible advantages of large-scale production, however, is the fact that the trend towards increasing centralization of manufacturing tends to go hand-in-glove with the increasing use of energy and automation instead of human labor and skill. As Paul Hawken points out in The Ecology of Commerce, this trend is precisely opposite to the long-term needs of society, which are to employ more people while using less materials and fuel. For these trends to change, a shift is needed in the economic incentives that businesses face.
Some people see the efficiency of large, centralized manufacturing processes as a critical component of a more sustainable future, while others believe that the best hope for the future lies with a retreat from the global economy. Ultimately, neither approach, taken as dogma, is likely to result in an optimal solution for a building. Efforts made to utilize locally available materials can significantly reduce energy use and pollution, especially for massive materials such as stone and concrete. Given the overriding importance of the energy performance of a building over its lifetime, however, it doesn’t make sense to sacrifice efficiency in building operations in order to use a local material. These decisions are best made in the context of the overall lifecycle of the material—and building—in question.
•All else being equal, using locally produced materials is clearly preferable from an environmental standpoint to using materials from a great distance.
•Consider the palette of materials available early in the design process to avoid being locked into a design for which the most readily available local materials are not appropriate.
•Consider locally produced/available wastes as potential materials for building projects. Examples include salvaged wood, salvaged tile, concrete rubble for backfilling, and materials made from recycled paper, such as cellulose insulation.
•Don’t assume that products from local sources haven’t traveled a long way. Check on the route a product will take from source to building site if you have reason to suspect it may not be direct.
•When using materials that come from a large distance, try to choose those that are transported by rail or ship over those hauled by truck.
•Due to the greater impact of short hauls and smaller vehicles, measures that can reduce the number of trips to and from a building site, and consolidate deliveries in fewer and larger loads, can significantly reduce air pollution and other impacts.
•Ensure that any vehicles over which the construction project has authority are operating efficiently and with optimum pollution controls.