Technology

Making a Difference

The Benefits of Recycling
Compost Production Requires Aerobic Treatment and Heat
Dual Direction Negative Aerated Static Pile
Gore Cover In-Vessel System


Since the 1980's, Cedar Grove Composting has played a key role in transforming our communities' waste into a premium, recycled product. This has been accomplished via significant investments that have advanced the technology of making compost.

The Benefits of Recycling

The benefits include:

• Diversion of organics from landfills: With municipalities working under mandates to reduce the waste entering landfills by as much as 70%, composting is proving to be practical, environmentally friendly, and cost effective way to meet those goals.
• Reduced greenhouse gas production at landfills/feedlots: Composting organic waste decreases the amount of methane gas generated in landfills/open waste sites.
• Composting reduces pathogenic organisms, harmful insects, and weed seeds being released into the environment: The relatively high temperature at which compost is "cooked" kills harmful bacteria such as E-coli and salmonella, weed seeds, and insects.
• Decreases the need for commercial fertilizers: By using compost, you reduce the amount of commercial fertilizer used, reducing the reliance on petroleum-based fertilizers.
• Compost enriches the soil: Compost adds nutrients, helps maintain the correct soil Ph, increases water retention, reduces water runoff, and increases the nutrients actually available to the plants.

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Compost Production
Requires Aerobic Treatment and Heat

Cedar Grove Composting is driven to produce the finest compost which meets the definition of the U.S. Composting Council: "Product resulting from the controlled biological decomposition of organic material that has been sanitized through the generation of heat and 'processed to further reduce pathogens' (PFRP), as defined by the U.S. EPA (Code of Federal Regulations Title 40, Part 503, Appendix B, Section B), and stabilized to the point that it is beneficial to plant growth".

To accomplish this, Cedar Grove's composting technology has continued to evolve, from a simple windrow process in 1989 to dual-direction negative aerated static pile system with exhaust biofilters in 1996 to a partnership with Gore cover systems in 2003.

Since 1989 Cedar Grove Composting has been recycling yard trimmings to put organic matter back to work in our landscapes. At Cedar Grove grass, leaves, and brush from a variety of yard waste collection programs are composted to produce high-quality soil amendments. Cedar Grove compost is:

• Made from yard waste, plus small amounts of wood waste and grocery-produce waste
• Made entirely from organic waste materials, without chemical additives
• Thoroughly decomposes to produce a stable soil amendment
• Composted at over 130 degrees F to destroy weed seeds and plant pathogens
• Processed at a permitted facility in compliance with state and local environmental and public health regulations
• Tested for pathogens, pesticide residues and other contaminants to ensure that it is safe for human health and the environment

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Dual Direction Negative Aerated Static Pile

Cedar Grove Composting's Process Pictogram

Cedar Grove Composting implemented this technology in 1996, producing premium compost via a controlled scientific process:

• Yard trimmings and other "green" waste is received at Cedar Grove Composting's Maple Valley facility. High-speed hammer mill grinders shred incoming material. Conveyors then move shredded material to one of seven primary aeration zones.
• Material is stacked up to 17 feet on concrete pads that have been studded with air holes connected to variable speed blowers. These blowers provide sufficient air to encourage the growth of naturally occurring microbes that degrade the material, transforming it into finished compost.
• A temperature feedback system monitors fan speed and temperature within the cells to track the composting process. Temperatures climb above 130 degrees F. to eliminate weed seeds, pesticide and herbicide residues and plant pathogens. Material remains on the primary cells for up to 21 days.
• As the initial heat cycle declines, conveyor transfers the material to the secondary composting cells. These cells are fitted with dual-direction blowers that are used in both negative and positive modes to continue the composting process. Material sits on one secondary cell for 30-45 days and then is transferred to an adjacent cell where it remains for another three weeks.
• Next, material is moved to curing piles where it remains for between 6 and 18 months.
• After proper aging, the material is screened and blended into a mix for bags or bulk use.

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Gore Cover In-Vessel System

In 2002, Cedar Grove Composting began implementing a technology upgrade incorporating a Gore Cover In-Vessel System.

The Gore Cover, manufactured by Gore Creative Technologies Worldwide, utilizes positive aeration, control and a specially designed cover to create an enclosed system that controls odors, microorganisms and creates a consistent process unaffected by outside environmental conditions. Medium pressure aerators connect to on-floor aeration pipes or in-floor aeration ducts. Stainless steel probes inserted into the pile monitor oxygen and temperature parameters. The data is relayed to and stored in a computer. This data controls the aerators to keep pile conditions consistent

After a pile is constructed, the Gore Cover, a specially developed Gore-Tex membrane laminated between two polyester layers, is pulled over the pile. The Cover protects the pile from weather conditions, but allows release of CO2. These controlled conditions allow consistent product to be produced without the risk of damp pockets, resulting in anaerobic conditions and, therefore, increased odors.

The Gore Cover controls odor emissions in three ways:

• Prevention of anaerobic pockets,
• The Cover acts as a physical barrier against gas escape from the decomposing pile
• Controlled condensation on the interior of the cover.

A fine film of condensation develops during the composting process that collects on the inside of the cover. The moisture helps to dissolve the gases. The condensation then drips back onto the pile, where they continue to be broken down by the composting process.

Material movement will consist of unloading and mixing material in the tipping building and grind onto the zone with a portable grinder as is currently done with Zone 7 and the post-consumer foodwaste pilot projects.

The new system will shorten the time required to produce finished, premium compost, as follows:

• First zone - Four weeks - Material stays on the initial placement zone in-vessel
• Second zone - Two weeks - Material moved to another in-vessel zone with minimized addition of water. Water addition is nominal because the in-vessel system retains the initial moisture within the system and only releases minimal amounts.
• Third Zone - Two weeks - The final move is to a third uncovered zone.
• Screening - Material will be screened then ready to sell within 15 days.

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