Mulching with recycled rubber tires

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Photo courtesy of Vagawi

Every year, approximately 1 Billion tires are replaced due to wear and tear. Many of these tires end up in landfills, but the majority are burned or converted into Tire Derived Fuel. A growing number of tires are being recycled after they have reached the end of their useful lifespan.

Recycling tires is a tricky process, because tires are a hodgepodge of many different things:

A typical passenger tire contains 30 types of synthetic rubber, eight types of natural rubber, eight types of carbon black, steel cord, polyester, nylon, steel bead wire, silica and 40 different kinds of chemicals, waxes, oils and pigments. They typically contain 85% hydrocarbon, 10-15% iron (in the bead wire and steel belts) and a variety of chemical components.

Discarded tires are mostly inert, but their effects on the environment are largely unknown. When discarded in landfills, they pose a significant fire risk and they take up a lot of space. Even before they reach the landfill, a lot of tire rubber flakes off into the environment from normal wear and tear. The effects of this worn tire rubber haven’t been widely studied.

Old tires are a cheap and plentiful resource, so many different ideas have been proposed to put old tyres to practical use. In the 1970’s, several attempts were made to build artificial reefs out of discarded tyres. Those plans didn’t work out very well, because chemicals in the tires repelled marine life. Now, millions of tires are rolling around on the ocean floor and even causing damage to natural coral reefs.

More recently, tire recycling companies stepped in and found commercial uses for tire scraps. More than 80% of dead tires end up getting turned into Tyre Derived Fuel. When tires are burned along with coal and wood scraps, they can actually reduce emissions of some pollutants.

There are other uses for recycled tires – they’re used as an ingredient in road construction, as a replacement for pavement, to make rubber flooring, and as artificial mulch. A blend of liquid asphalt and “Fine Grind” tire rubber lasts about 25% longer than other road surfaces, which cuts down on maintenance costs for highways nationwide. Crumb rubber is also widely used on running tracks and playgrounds for children. It provides excellent cushioning and prevents injuries for children and adults alike. Rubber chips are also offered as mulch.

Rubber mulch is a controversial product. Some gardeners swear by it as a long lasting weed suppressant and low maintenance landscape surface. Other gardeners steer clear of rubber mulch, due to concerns about chemical leaching, fire hazards, and smell.

Here are some of the benefits of using rubber mulch instead of wood mulch:

  • More durable (rubber lasts 5+ years vs 1-2 years for wood mulch)
  • Uniform look and color
  • Does not attract termites or other insects
  • No risk of mold or fungus infestation
  • No effect on wood allergies
  • Resistant to flooding and high winds
  • Cushy and comfortable to walk on
  • Helps dispose of used tires
  • Here are some of the problems with rubber mulch:

  • Some brands contain metal wire or nylon scraps
  • Smells like rubber, especially on hot or humid days
  • Potentially flammable (but so is wood mulch)
  • Risk of chemical contamination
  • Breaks down into inorganic components
  • Heats unevenly in the sun, killing sensitive roots
  • May contain carcinogens
  • The jury’s still out, but recycled rubber mulch seems safe to use in certain applications. What do you think? Do you have any experience using rubber mulch in your garden or greenhouse?

    Here’s another way you might want to consider to recycle old tires – they make great insulation for earth friendly homes. Crumb rubber also shows promise as a water filtering medium. In Arizona, state law makers are exploring another way to dispose of old tires: filling abandoned mine shafts to eliminate dangerous pitfalls. A few million years from now, who knows – those mine shafts might fill up with black gold!

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    Photo courtesy of Road Dog

    An Introduction to Earthships

    earthship1.jpgWhen it comes to housing there are many different shades of green in the world.  On one end of the scale are the conventional homes that are built more energy efficient and maybe use a few more earth friendly materials.  At the other end of the scale lies the Earthship.

    Earth ships came about in the 1970’s when Mike Reynolds wanted to create a home that would

    • A. Use materials that were readily available and reuse existing materials

    • B. Generate their own utilities off the grid

    • C. Be able to be built by the average person with no specialized skills

    The result was a U shaped structure built from old tires rammed with earth.  Scrap tires are available just about everywhere and usually for free. Once put in place a team of two people go to work filling the tires with dirt and using a sledge hammer to compact the dirt into the tires.  Once filled, the tires generally way as much as 300 pounds so filling them in place is essential.  The earth filled tires are very structurally sound and resist fire.

    Non-load bearing walls are made using alternating rows of empty cans and cement which are then covered with plaster or adobe. 

    Earthships are designed to catch and use water from rain and snow.  The roof channels the water into a cistern where it is then filtered and pressurized to be used throughout the house.  Grey water is run through an organic filtration and processing system and then used to flush the toilets and black water is sent to a solar enhanced septic tank.

    Electrical power is provided by Photovoltaic panels and windmills that charge a bank of golf cart batteries.  The DC power is fed to an inverter to run appliances, computers, etc.  This electricity is not used for climate control however.

    The thing that fascinates me with the design is the heating and cooling of the Earthship.  During colder times sunlight is let in to heat the structure and the structure itself stores the heat for when the sun goes down.  During warmer months the cool of the earth is used to dissipate heat and the sun is blocked so that the interior is kept comfortable.  Many articles I found say that the cool flows out of the ground into the house, which of course is nonsense.  Cool is the lack of heat; it doesn’t flow anywhere it just give heat a place to go.  But the important thing here is that no electricity is used in heating and cooling the house.

    Interested, and want to learn more? Try these links.

    Mike Reynolds’ company, Earthship Biotecture sells plans, kits, and video to aide people in building their own Earthship and Earthship Hybrid homes.

    This site has a pretty detailed account of building an earthship in Colorado.

    Here’s another site that details the construction techniques.