Disposal Company Expands Composting Operations


Courtesy of BioCycle Magazine

Since 1997, Texas Disposal Systems, Inc. (TDS) - an independently owned solid waste company located near Austin, Texas - has operated a composting division, Texas Organic Products (TOP). In our previous BioCycle report ( -Composting Is Alive and Well In Central Texas, - October, 1997), we described how TOP evolved after starting an initial grinding and static pile composting operation at our permitted municipal solid waste landfill site. Today, composting is done on a separate 30 acre site next to the landfill. A wide variety of feedstocks are received; end products include mulch, organic topsoil blends, and compost.

The facility was designed and constructed with the convenience of customers and staff in mind. Regular clients include landscapers, building contractors, trucking firms, trash haulers and the general public. Many of the landscape customers and homeowners who drop off loads of yard trimmings also are large users of our end products, allowing for -one-stop shopping.

The new site was constructed with clay soils excavated from a landfill cell expansion. The initial phase included six acres of brush grinding, wood chip storage and a six-acre compost pad. The uppermost two feet of clay soils under the compost pad were compacted to meet the Texas Natural Resource Conservation Commission's groundwater protection criteria. The working surface of the compost pad is 12 inches of compacted cement-stabilized roadbase. All stormwater from the pad flows by gravity to a clay-lined retention pond capable of storing water from a 100-year, 24-hour storm event. Pond water is routinely pumped into a tanker truck and applied to windrows to maintain ideal moisture levels. Six additional acres of pad surface area are scheduled to be completed later this year, bringing the total working surface area for grinding and composting to 18 acres of the 30-acre site.

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Feedstocks are solicited by TDS staff in the Austin and San Antonio offices. TDS has one designated position focused on special wastes for both the landfill and TOP composting operations. All feedstocks must pass through the TDS landfill gate house for initial inspection. Tipping fees are charged for all incoming materials. The gate attendant makes the decision on whether the load should go to the landfill or the composting facility; only source separated organic feedstocks are accepted for composting. While the tipping fee at the gate is the same for all loads, the internal rate for source separated roll-off loads of compostables hauled to the landfill by TDS is considerably less.

Prior to completion of the new composting facility, only clean, untreated woody materials were accepted, such as brush, yard trimmings, dimensional lumber, etc. Now additional carbon materials are accepted, including shredded office paper from a local federal employer and Austin phone directories. All woody and bulky materials are put through a Morbark 1200 tub grinder.

Because of the high volume of carbonaceous feedstocks, there was a need for more moisture and nitrogen in the initial compost mixes. TDS staff sought food processing residuals and other liquids that normally would be discharged to a sanitary sewer or solidified prior to landfilling elsewhere (the TDS landfill does not have a solidification operation). Now the facility routinely receives out of date and/or expired containerized and bulk liquids from local soft drink manufacturers, beer and wine distributors, grocery store warehouse operations, and a local dairy. It also gets food processing residuals from a frozen food manufacturer and dead animals from local veterinary clinics, municipalities, and the general public.

Containerized liquids are dumped onto the compost pad on an upgrade that slopes down toward a horseshoe of wood chips. Shredded paper and phone directories are in the middle of the horseshoe. The containers are crushed with a front-end loader, placed in a roll-off and then disposed in the TDS landfill. The liquids are absorbed into the paper media, which is then mixed with the wood chips and put into a windrow. Bulk liquids are either directly applied onto windrows or surface applied to beds of wood chips and paper. The addition of these materials to the composting process significantly decreases overall processing time and results in a much more marketable end product.

Feedstocks are combined into windrows in predetermined proportions and incorporated using a Scarab turner. Temperatures are monitored daily and records maintained to verify that the minimum time/temperature criteria for -Process to Further Reduce Pathogens - have been met. Materials usually remain in active windrows for six to eight weeks, followed by curing in large static piles, and finally, screening to three-eighths inch or less through a McCloskey Bros. six-by-21-foot trommel screen. Oversized material from the screening operation is recycled into new windrows. Overall, the TOP facility receives about 100,000 cubic yards (cy)/year of woody materials. Food processing residuals comprise another 4,800 cy/year.

Odor control is a top priority. Feedstocks having high odor potential are immediately incorporated into windrows. Piles exhibiting odors after incorporation are topdressed with compost screening -overs - as a biofilter, which has been a very effective solution. A recycle spray system was installed on the stormwater retention pond to maintain aerobic conditions and prevent odors associated with anoxic conditions. Thus far, maintaining a higher than normal carbon to nitrogen level has significantly helped in minimizing odor problems.

Currently, only bulk materials are sold, but bagging is being considered due to high demand for mulch and compost blends from many of the landscaping and retail nursery customers. Freshly ground mulch is sold to customers who typically use it for natural walkways, erosion control, etc. The majority of wood chips, however, are allowed to slowly compost in large static piles prior to further processing. While most of the composted mulch is incorporated into windrows, a smaller portion is reground to two inches or less and sold as a composted mulch.

Soil recovered from land clearing projects is screened to a half-inch particle size and combined with composted mulch in windrows at a 3:2 ratio. The mixture is watered as necessary, composted and then screened to a particle size of three-eighths inch or less. The material has a high clay content, but is very popular for the establishment of new lawns and ornamental beds.

A garden mix is produced by combining screened composted products and washed river sand in a windrow. This mix is used for raised flower beds and vegetable gardens, or other applications where a higher organic content, loose well drained soil is desired. It is the only product not made from 100 percent recycled materials. Our staff is evaluating using recycled mixed cullet glass sand in place of the washed river sand.

About 24,000 cy/year of screened compost is produced. In addition, the operation yields 12,000 cy/year of composted topsoil, and 12,000 cy/year of composted mulch.


Products are marketed on a three-tiered pricing structure: distributor, wholesale and retail. Distributors typically include soil blenders and organic nurseries that purchase in large volumes. Wholesale customers include landscapers, home builders, bagging companies, trucking companies, etc. The material also is sold in bulk on a retail level, both at the composting facility and at the -Eco-Depot, - a TDS-owned and operated solid waste transfer station located west of Austin. Some product deliveries are made on backhauls using TDS roll-off container trucks that would normally leave the facility empty, thereby generating another revenue stream.

Marketing methods include radio and television advertisements, our website, booths at home product and gardening shows, recycling events, and distribution of printed brochures describing the various end products. The TOP division manager takes every opportunity to make presentations to gardening clubs, schools, recycling groups, and other interested organizations to help get the message out. Organized tours are common at the facility, resulting in many new customers. Visitors also enjoy touring the TDS wild game park located in the buffer zones surrounding the landfill and composting operations.

At a time when many solid waste disposal companies are backing away from recycling and/or composting, TDS has shown that a composting program can beneficially coexist with landfilling and waste collection operations. Besides the obvious benefits of preserving future landfill capacity and shared resources (administrative and marketing staff, and equipment, for example), the TOP composting operation also has demonstrated that it can be a success from both financial and public perception standpoints.

Jim Doersam is manager and Bob Gregory is chief executive officer of Texas Disposal Systems, Inc. For more information, visit the TDS website.

By Jim Doersam and Bob Gregory


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