You cant evaluate material flows, by evaluating products, like a car of a building. As argue din the previous article. But in general this is what sustainable approaches suggest, and in special the ‘circular’ trend: if you recycle the product endlessly, it all becomes circular. Not so. This is the narrow view of the product focus, while impact on material flows stay out of sight. The impact can however differ a lot, depending where and when in the cycle is interfered. Which becomes visible when analyzing such a material cycle, like stones for building.
The most basic way of building with stones is to cut these out of nearby rocks or mineral layers: it takes some labor, but you end up with a ready made stone. And start piling up. Which can done directly on each other without binding agent, as practiced in many cultures around the world, the best known example maybe being the Inca’s in Peru, especially in Machu Pichu: perfection in piling. But also the Romans knew how to do this: the aqueduct in Segovia Spain, still in use until 1995, is made of loosely stacked stones .
A next version is adding some binder, for instance with a more rough stone, using clay or loam to create solid walls Half the countryside in France has been built like that, and still exists. Or with stones from marl or limestone, deposits from years of ocean life , binded by a local mix of clay and lime and silt like in southern Holland .
The next level is even working without stones, and directly apply loam , as in the adobe way. Loam is eroded rock in specific particles, caused and spread by rain and rivers over the lowlands. Nature has done the work, and you can model complete cities with that. Many cultures in Africa still work like that, and old examples exist like Bam in Iran, or Shibam in Souther Yemen: 9 stories high, and already 500 years old! Amazing. Still today, over 1,5 billion people live in adobe houses!
The loam can be directly applied to make casted walls, or make bricks first, drying in the sun and later stacked as walls.
Another approach is not to use clay and loam “ purely natural’ , but to burn the bricks first. This introduces methods requiring to apply ( and depleting) a second resource: fuels. From eroded rock, rock is recreated, now directly in the desired shape ( bricks in different sizes, roof tiles etc) .
Which works with clay, but not with for instance sand , a more coarse material. This requires a different binding process, for instance (fuel) burned and treated lime stone to make cement, together with other additives you can again make rock. Without additional heat, which has been invested in the binder process.
A recent variation is to work with fine particles, and let nature do the work again, to make a building material, in stead of using a baking or binder process: its fungus and/or enzymes that are “programmed” or forced, to grow as “bio-stones”.
This shows that there are different ways leading to the same result. Each with their specific material need and/or additional energy input. Its depending on different moments in the cycle in which resources pass through the human inhabited environment. At the start ( at least for us) from rocks, pushed up by tectonics, or somewhere on the road, with eroded dust on its way to the ocean to become part of a new cycle. Along the way we can interfere at several moments, add labor, or fuel, or have nature do the work.
Every method has its advantages and disadvantages, has its own level of overall ‘exergy loss’ ( loss of potential to do work). Cutting rocks or using adobe , originally uses only one material, with added labor force. Sometimes in combination with solar power ( for drying etc) . Bricks use the same base material, but add resources from a second source, wood, coal, later gas, to burn the stones and replace the handwork. Labor starts disappearing as a source.
Sand and cement bricks cant be made by labor, they require external energy , today more usually not for bricks but mostly to create solid walls directly .
The Bio-stones that are piloted now, again try to use natural forces, with mankind helping nature develop in the right direction. Though most of these processes are somehow ‘high tech again’ requiring input of more sources.
As long as no more of a resource cycle is used as naturally flows through the ‘ built environment’ there is no real problem. The brick industry in the Netherlands used river sediment , erosion material from the Alps, the amount limited to what passed through the rivers, and more or less part of a closed cycle . To add fuel, a second source is withdrawn from its natural course. If for instance wood from a well maintained forest, this can still also be part of the natural closed cycle approach. Adding fossil fuels breaks the balance, and flows are disrupted beyond recovery rates. Usually stocks that won’t regenerate. ( besides other nasty effects as land loss by excavations and creating artificial lakes, and climate change by CO2 releases beyond natural balance capabilities.
If more is distracted as suppleted, the source dries up. Which is what happened several times in China, for instance with clay bricks: forbidden in the North part of China, since volumes became so huge that fertile soil was used. The agriculture was in danger. Using more as naturally replenished creates problems…
And adding a second source speeds up the building potential, at the same time speeds up the depletion of resources, even in two resources. And as the speed goes beyond natural cycle speeds, problems occur. In fact : sustainability, keeping the resource cycles going, requires time…
Except the stony brick style of construction, there are other materials, which have their own cycles, like regrowable materials and metals. Regrowable are the most interesting, regrow can somehow be controlled, and applying for construction requires little extra energy. Metals are in fact not appropriate for construction of buildings. These require enormous amounts of energy ( for which alternatives exist with much less impact) , and the natural cycle is of a very low geological speed, that its hardly suitable to fit in closed cycle approaches. They can only be depleted . So we should reserve these for only those applications that have no alternative material solution. We see already that metal stocks are getting diluted, and as a result require ever more energy to mine. The metal sectors are already looking for alternative moment in the cycle to intercept molecules. Like from oceans. [1]
And by the way, replacing the second required source, fossil fuels, by renewable energy has it limits as well: those will increase the speed of depletion of materials, for conversion devices and suitable applications like wind turbines, solar panels and electric cars for instance. If we want to continue constructing buildings, not deplete stocks and stay within CO2 emission levels, we will , in the Netherlands bur for sure in a world with a extra few billion people, have to find the appropriate option within above described cycles.
Which will require that for the original extraction of resources from global stocks, a environmental load has to be added to any activities impact, especially within so called popular ‘circular’ approaches. The original impact has not disappeared with recycling or a second use, its only prolonged use of the original resources, so that the included original impact can be divided over a longer time period. The same function is provided with a lower time related impact. Or in other words, the sources get longer time for recovery . Its also clear that the way and the moment of interception in cycles has a large effect on the maintainability of cycle flows ie the impact. Using erosion materials and processing with labor and solar energy has huge advantages, as more as half the global population knows. Straw, loam wood construction (and soon bamboo) can also be applied here in The Netherlands for instance, many examples exist, historically and modern, and would substantially lower the impact from construction, and get closer to closed cycle approaches. Nevertheless, for these ‘regrowable materials” as for all other materials, applies: Sustainable materials do not exist, only the use of materials can be sustainable . Or better: the use can be ‘maintained’: of resources in cycles that is, not of products….
[1] https://www.huffingtonpost.com/richard-steiner/deep-sea-mining-new-threa_b_8334428.html
