Solid Waste & Recycling Magazine

Feature

MBT

A new approach to managing municipal solid waste is coming closer to reality in Canada. A mechanical/biological technology (MBT) known as the ArrowBio Process is being proposed for Grey County, Ontari...


A new approach to managing municipal solid waste is coming closer to reality in Canada. A mechanical/biological technology (MBT) known as the ArrowBio Process is being proposed for Grey County, Ontario by BioWaste Treatment Technologies, a firm that has established a willing host agreement to build in Southgate Township, (about an hour and a half north of Toronto).

Biowaste principals Victor Sibilia and myself have backgrounds in waste management. Sibilia was the founder and operator of EnviroTire in Brampton, which processed 1.75 million tires a year into re-usable crumb rubber. In addition to being a government relations consultant, I co-founded Wood Waste Solutions– a wood recycling company that now operates out of Bolton.

Both of us came across the ArrowBio technology independently and recognized that it took a very different approach to diverting organics and recyclables from landfill. Developed in Israel — where there are no curbside recycling programs — the technology is designed to process unsorted municipal waste, recover the recyclables, remove contaminants and then anaerobically digest the remaining organic waste into biogas, digestate and excess water. The two-stage process diverts upwards of 85 per cent of waste from landfill while generating green energy.

The process

The technology developers, Arrow Ecology in Israel, are experts in water treatment systems. They recognized that water is an excellent medium to separate municipal waste based on each component’s specific gravity, as well as to biodegrade the remaining organic materials into energy-rich biogas, clean water and a stabilized soil amendment product. The process exploits the same science that anaerobically digests sewage sludge.

The water washes clean the recyclable materials, enhancing their market value. It also provides a flow regulation property that makes the continuous processing resilient to changes in input composition, while containing all odors and by-products within a network of tanks and pipes.

In the first stage, the waste (containing biodegradable and non-biodegradable materials) is dumped on a tipping floor where it’s visually screened for unsuitable waste, such as bulky goods. Material is then directed into a large tank full of recycled water that contains biological agents. The various materials in the waste stream are separated via gravitational settling, screening, and hydro-mechanical shredding. Separation is based primarily on the principle that inorganic materials, such as metals and glass, have a specific gravity that’s greater than water, while plastics and biodegradable organic matter have a specific gravity that’s equal to or less than water.

The heavy components sink to the bottom of the tank and are conveyed to a trommel screen that opens any plastic bags with cutting blades and returns the small fractions to the settling tank. Using cutting blades rather than a shredder insures that any hazardous materials such as batteries or cleaning product containers are not released into the solution. The heavy fractions are then conveyed over a magnet and an eddy current, separating the ferrous and aluminum metals; the remaining materials are hand sorted to recover glass, detergent containers or other specified materials. The residue from this side of the operation is typically inert waste that can be safely landfilled.

The light fractions, such as mixed plastics, are floated across the tank by a paddle wheel and conveyed up a belt to a picking station where PET, HDPE and film plastics are air classified into three streams of recyclable products that can be bailed and marketed. Since plastics don’t absorb water (compared to biodegradable material), they’re lighter and separate easily.

The biodegradable material that remains in the floatation tank enters the filtration systems where pulverization creates a watery organic solution. This energy-rich solution contains biodegradable material, organic matter, paper and other substances that can now be treated in the bioreactors.

Biological treatment

The carbon-rich organic fluid then undergoes two processes, both of which are orchestrated by naturally occurring microorganisms in highly controlled environments. The bio-liquid first enters acetogenic bioreactors for several hours of preliminary treatment. There, biological hydrolysis splits certain molecules into their component, readily-metabolized parts, (e. g., simple sugars and organic acids).

This organic liquid is then pumped to the methanogenic reactor for digestion. The process uses an advanced variant of anaerobic digestion that, with respect to solid waste processing, is unique to the ArrowBio Process. “Upflow Anaerobic Sludge Blanket” (UASB) digestion, thoroughly degrades the biological materials into finished soil amendment products and a methane-rich biogas.

The biogas is collected at the upper part of the methanogenic reactor and is re-circulated by compressor and re-injected into the reactor close to its bottom, providing agitation without mechanical devices. Excess biogas is routed out of the system to power the facility, while the balance can be sold as green energy for transportation and power plants (substantially less polluting than alternative fossil fuels). In Ontario, it’s anticipated that the biogas will qualify for the Province of Ontario’s new Feed in Tariff (FIT) program and generate revenues of $0.14 a KWh.

The process re-circulates water throughout the system; excess water is polished to meet community standards and released to the water shed or used for irrigation. The resulting di-gestate is thoroughly degraded so that it does not smell; in Israel it’s used as a soil amendment product. In Canada it may be necessary to further process this material to meet local compost standards.

Installations

It’s a great benefit for municipalities considering a new technology to be able to visit plants that are up and running. Currently, two ArrowBio plants are in operation. The original plant, just out side of Tel Aviv, has been processing 20,000 to 25,000 tonnes per year for the past seven years. Last June a new plant with a capacity of 300 tonnes per day was completed in New South Wales, Australia and is now fully operational. BioWaste Treatment Technologies plans to build a plant similar to the Australian one (or about 90,000 tonnes per year) in the Dundalk Industrial Park. Project financing is contingent on securing sufficient waste volumes under long-term contracts; the local municipalities are considering whether to assign their unsorted municipal waste to BioWaste for a tipping fee of $50 a tonne.

Local municipalities are mindful that the US border will be closed to much of Ontario’s municipal waste in 2010. In addition, waste diversion continues to be a priority for municipalities intent on preserving valuable landfill space. Getting organics out of the waste stream is essential to meeting diversion targets of 60 per cent or more. Being able to accomplish this (and more) without the added expense and disruption of a source-separated organics (SSO) program could be a major factor in their decisions to commit their waste to Biowaste to be managed in an ArrowBio MBT plant.

NOTE: A video of the technology is available at: www.youtube.com/watch?v=gZVqQ8f6LiI

Arthur Potts is President of BioWaste Treatment Technologies Limited in Toronto, Ontario. Contact Arthur at arthur@biowastetreatment.ca

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The two-stage process diverts upwards of 85 per cent of waste.


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