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17 July 2013

Creating organic feedstock for energy recovery – the basics on organics separation, collection, and processing

I have been involved in the transfer and recycling business for a very long time, and I’m finding the new push for organics recovery an interesting new wrinkle. From what I gather, there’s a lot of interest, but also many questions, so I thought I would put down a few of my thoughts (with a few pictures) on a the basics, including separation, collection, and feedstock preparation.  I also give a few examples of operating facilities.

Where to separate the organics – source separation vs. processing facilities

Source separation (completely separate organics collection), is a required approach in Europe, where it’s used in both residential and commercial settings. Separation of organics and recyclables can be performed at mechanical biological treatment (MBT) plants in Europe, even with separate collection of organics. In the US, some projects are separating organics and recyclables that are collected as mixed solid waste at recovery facilities (MRFs), as there are not that many separate organics collection programs.

Point of generation inside storage containers are usually plastic, generally, equipped with a lid and made to be easy to clean. Sizes are generally a gallon, up to 5 gallons, and container types vary. Some programs require the use plastic bag liners, which can be either non-degradable or compostable. Typical residential curbside set-out containers are larger, smaller in capacity than typical solid waste set-out carts, and usually have attached hinged lids. I’ve included a couple of pictures of common collection containers.

Collection containersCollection containers

Another interesting option for larger generators is the use of self-contained roll-offs, typically used at commercial facilities and generally positioned at loading docks. These are very good for liquids control compared to a separate compactor/ roll-off configuration.

The MRF approach is being used in a few locations, including San Jose, CA. The use of a rotating drum digester technology is being used at facilities in Delaware County, NY; Nantucket, MA; and Edmonton, Canada.

Types of collection vehicles

European collection trucks, which are similar to US truck bodies, but with a dedicated automated or semi-automated collection mechanism, are widely used. Another option is the FAUN VARIOPRESS, which is being introduced in the U.S. It has fewer parts and a cylindrical truck body (operation is somewhat similar to a concrete ready-mix truck).

US options include dedicated route trucks for organics only; rear, front, and side loaders for organics only; and split body route trucks for multiple waste types, which allow alternate material collection with the same truck on different route days.

Feedstock preparation – processing after delivery

There are two main options for processing organics feedstock – Wet or dry anaerobic digestion facilities. Wet options include DODA® U.S.A., Inc.’s equipment to separate out inorganics and produce a slurry to be digested, and hydropulpers (like a giant industrial blender, which blends organics, and separates heavies and lights, producing a slurry to be digested.) and the Vaughan Rotamix for mixing within a “wet” digester. “Dry” anaerobic digestion pre-processing is typically based on source separation of organics (European style) and can include organics recovery from a MRF operation (part of the overall organics recovery system San Jose, CA style).

Examples of operating facilities

Obviously, we are just in the beginning stages of what I think could turn into a huge market. Here is a sampling of the diversity of organics conversion projects that include energy recovery:

  • TY Lin – Wet Digestion – Covington, NY
  • Clean World Partners – Wet Digestion – Sacramento, CA
  • Zero Waste Energy (ZWE) – Dry Digestion (Fermentation)

–     Small Scale AD – Monterey CA

–     Large Scale AD – San Jose, CA.

I would be most interested to hear from any readers about their views on organics and where it fits into the waste management industry now – and in the future.

Categories: Organics, Transfer/Recycling/Processing Facilities
Posted By Ernest Ruckert, PE at 12:33 PM  |  1 Comment on Creating organic feedstock for energy recovery – the basics on organics separation, collection, and processing

One Response to “Creating organic feedstock for energy recovery – the basics on organics separation, collection, and processing”

  1. John Monaco says:

    It is very sloppy sending GARBAGE through a Trasfer Station.
    You have come over to the dark side? I guess it comes with age and wisdom. Hope you are doing well.
    Pie Alamo :0

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