Features such as low cost, low usage of fossil fuels and use of locally available resources can give some advantages in terms of sustainability. For that reason, these technologies are sometimes used and promoted by advocates of sustainability and alternative technology.
Besides using natural, locally available resources (e.g. wood or adobe), waste materials imported from cities using conventional (and inefficient) waste management may be gathered and re-used to build a sustainable living environment. Use of these cities’ waste material allows the gathering of a huge amount of building material at a low cost. When obtained, the materials may be recycled over and over in the own city/community, using the cradle to cradle method. Locations where waste can be found include landfills, junkyards, on water surfaces and anywhere around towns or near highways. Organic waste that can be reused to fertilise plants can be found in sewages. Also, town districts and other places (e.g. cemeteries) that are subject of undergoing renovation or removal can be used for gathering materials as stone, concrete, or potassium.
The waste materials include
* recyclable plastics such as PE, PP, PVC, PS, SB; PSE, ABS PMMA, PTFE, PA, PC, PUR, EP, UP and PET. ISF has made two documents on how respectively discarded plastics and aluminum can be salvaged and reused in developing countries.
* ferrous waste materials (e.g. cans, …)
* sewage sludge (for use as a fertiliser)
The waste materials can be gathered by waste pickers, or – if possible – with more sophisticated machines such as materials recovery facilities (MRFs),and solid waste processing facilities. The latter may allow better separation of the different metals, plastics, … resulting in a higher – and more efficient- yield. Also, waste pickers -besides usually not being equipped to disassemble the materials – risk being exposed to various poisonings.
Sewage sludge is collected not by hand, but through a sludge processing plant that automatically heats the matter and conveys it into fertiliser pellets (hereby removing possible contamination by chemical detergents, …) This approach allows to eliminate seawater pollution by conveying the water directly to the sea without treatment (a practice which is still common in developing countries, despite environmental regulation). Sludge plants are useful in areas that have already set up a sewage system, but not in areas without such a system, as composting toilets are more efficient and do not require sewage pipes (which break over time).
After collection, the obtained materials often need to be melted and recast in forgeries and/or may require bending, cutting, folding, … in a workshop. Plastics are a special case that are too melted in a workshop, using small, purpose-built hand-operated melting containers. Metalworking tools that can be used to cut or fold the metal are the OpenLathe and Multimachine. Also, some CNC metalworking tools can be appropriate.
In some cases, melting and recasting is not required, as some parts can be simply cut and used as is in different devices. An example is the passive solar collector built from old refrigerator tubing.
“This article is brought to you by Gus Woltmann”.