The Zanker Road Landfill, Rethink, Reinvent, Renew

Posted on June 18th, 2010 by Sally B. Woodbridge
Environmental |

The Zanker Road Landfill, Rethink, Reinvent, Renew!

You may not think of landfills as harbingers of a “green” future, but if you check the web site of the Zanker Road Landfill or, even better, visit the landfill sites on Zanker Road in San Jose you will think differently.

An unsorted mound of debris at the Zanker Road Landfill

Historically, landfills have been the repositories of rubbish, defined as waste, refuse or litter of no value. But about ten years ago as municipal dumps filled up, the importance of finding ways to re-use the debris from construction and demolition grew rapidly and rubbish began to acquire commodity status and a bigger market.

Today, Zanker Road Resource Management, Ltd., which was formed in 1985 to operate the Zanker Road Landfill (ZRL), receives up to 2,600 tons  of materials per day from around the Bay Area.

In 1999, after completing a nine-year permitting process, the Zanker Materials Processing Facility began operations. The ZMPF is divided into several processing areas devoted to different kinds of waste: demolition debris, mixed debris, and wood waste. The Facility, which can process unsorted demolition debris at the rate of 135 tons per hour, separates the materials into manageable and marketable products. These products are then directed to other on-site recycling operations or shipped directly to end product users.

The 240-foot-long Conveyor Sorting System, which includes elevated work stations for employees, disc-screens, and magnets, is located above large concrete storage bunkers that hold recovered materials. The sorting system is capable of sorting 30 to 40 tons per hour; it removes a variety of materials and creates up to 16 products from a typical mixed waste stream.

The green tubular mechanism shown on the right is part of the conveyor screening system described below.

During the sorting process the mixed construction and demolition debris is removed from the soil, and the residue is loaded into a tank of water. Wood floats to the surface where it is collected and dried. Metals and rubble drop to the bottom of the tank where magnets remove the metal.

Using heavy equipment, the wood is loaded into a grinder. The shredded wood is then screened and separated into wood chips and fines similar to sawdust. The site of this operation is shown above.

The accumulated  wood chips are either sent to markets as fuel for electric generation facilities or colored and sold as landscape mulch, shown below. The fines are sold as soil amendments and blended with other products on site to produce top soil. All products are sold to landscapers, contractors or the general pubic.

CONCRETE

The ZRL concrete plant discussed below, was one of the first in the nation to convert concrete debris into aggregate products suitable for foundations and road construction. Zanker adopted the knowledge and skills developed in the 1960s by the crushed stone and mining industry and became the first plant in the Bay Area dedicated to recycling concrete debris.

The concrete recycling process begins when clean and reinforced concrete is unloaded at the site. The material is then screened to remove oversized pieces which are re-circulated through the crushing circuit.

Ferrous materials, compounds containing iron, that would compromise the value of the products are removed by the belt magnet equipment shown above, which is operated by nine staff members, four of whom operate the machinery. The other five employees sort the material, removing plastics, wood, trash and other contaminates.

Known as the Air  Knife, the machine shown above uses high volume air blowers to separate plastics and wood from the concrete debris.

The green machine called the “rocket”, shown above, was invented by the Zanker staff. It uses 2000 gallons of water per minute to separate wood and other floating materials from the heavier concrete and metals. The wood flows with the water out of the front of the Rocket on to a conveyor system to be sorted.  The heavy materials are conveyed out of the back of the Rocket and past a magnet which removes metals and a sorter that removes trash. The water is screened and reused.

Products made from the recycled concrete includes a 3/4″ class II base rock, recycled fill sand, pea gravel and drain rock. These materials are sold to contractors and the general public.

That mountains of construction and demolition debris like the one shown above are being transfomed into useful products is a cause for celebration! If you want to know more about this  phenomenal process visit the Zanker Road Landfill on the ground and on its web site, z-best.com.