Options evaluated include storage (1) for transportation off-site, and aerobic in-vessel systems (2, 3) that create a ready-to-cure material or, in some cases, a ready-to-use soil amendment that can be applied on-site.

August 18, 2015 | Community Composting, Composting

Evaluating On-Site Organics Management Options

A 2015 organics disposal ban in the Metro Vancouver Region of British Columbia, led to creation of a guide for businesses and institutions considering managing their organics on-site.

Terry Fulton and Veronica Baker
BioCycle August 2015
Options evaluated include storage (1) for transportation off-site, and aerobic in-vessel systems (2, 3) that create a ready-to-cure material or, in some cases, a ready-to-use soil amendment that can be applied on-site.

Options evaluated include storage (1) for transportation off-site, and aerobic in-vessel systems (2, 3) that create a ready-to-cure material or, in some cases, a ready-to-use soil amendment that can be applied on-site.

In 2015, the Metro Vancouver region in the lower mainland of British Columbia, Canada, instituted an organics disposal ban. Metro Vancouver is a regional government representing 21 municipalities, one Electoral Area, and one Treaty First Nation, and is responsible for managing the solid waste produced by 2.4 million residents. Its organics disposal ban targets food scraps being disposed by residents and businesses. From January until July 2015, an extensive education campaign was used to raise awareness and encourage compliance with the ban.
Starting July 1, 2015, the regional government is enforcing the ban at its disposal facilities. Loads containing more than 25 percent visible organics by volume are issued a 50 percent surcharge on the tipping fee. Although the organics disposal ban applies to all sectors, this 25 percent threshold effectively targets the largest generators first, such as restaurants and food retailers. Pending political direction, Metro Vancouver may decrease this threshold over time. Monitoring during the six-month education period showed that 99 percent of the region’s customers are in compliance with the 25 percent limit.
For a restaurant or grocery store, a pamphlet introducing a new organics disposal ban can be the start of a logistical challenge. Without the proper tools, businesses are uncertain just how much “doing the right thing” will cost them. Staff training, hauling contracts and new disposal procedures all become part of a long stream of questions that foodservice establishments are asking, and answers can be hard to find. With the onset of the organics disposal ban, Metro Vancouver sought to provide businesses with appropriate tools and resources, including an on-site organics management review. Metro Vancouver retained the services of Tetra Tech Inc. to conduct a desktop review of options available for storage, hauling, and automated processing of organic material on-site for establishments producing between 10 to 1,000 metric tons (11 to 1,100 tons) of food waste per year. The review evaluated and compared on-site organics management options available in North America and used successfully in various industries, but excluded technologies that discharged a slurry to sewer without recovering materials or energy.

Available Options

Because of the abundance of available technologies, Tetra Tech grouped them into four overarching options: Storage, Pretreatment, Aerobic In-Vessel, and Anaerobic Digestion. Storage is what most users are already familiar with — they have bins, organics are put in the bins, and they get taken away. Specialized storage options, such as a compactor equipped with a biofilter, make this even easier for organics by providing capacity for larger volumes and designs that are better suited to dense organics.
Pretreatment and other processing options increase the commitment to managing more of the organics processing on-site. Pretreatment rapidly reduces the volume of organics by removing the largest component: water. Excess water can be removed through a mechanical process (dewatering), or by heating the organic material to accelerate evaporation and stimulate biological activity (dehydration). These technologies are effective for establishments that are short on space or time, as they can fit in a dishwashing area and the process is generally measured in hours or days, not weeks or months like other processing options.
For those aiming for the next level of on-site organics management, aerobic in-vessel systems are available to help businesses create a ready-to-cure material or, in some cases, ready-to-use soil amendment that can be applied on-site. The downside is that aerobic in-vessel systems require more time and space; staff would need to be trained to ensure the system is operating efficiently and might spend an hour or two each day on keeping the system running smoothly. The “black gold” payoff is sweet, however; for businesses with landscaping, gardens or green roofs this can be an excellent option to close the loop.
For those who want other benefits — such as electricity — small anaerobic digesters can process food scraps while simultaneously creating energy-rich biogas. Not only do these systems help manage organics, they can reduce reliance on grid electricity and save a business money. There’s always a catch of course as these systems have a higher capital cost compared to other options. The on-site options review assessed the medium and large options most readily available in the North American marketplace.
For both aerobic and anaerobic in-vessel systems, Tetra Tech’s study reviewed three sizes (Table 1): small (approximately 10 metric tons/year or four 32 gallon containers per week), medium (approximately 100 metric tons per year or one 6 cubic yard (cy) container per week) and large (approximately 1,000 metric tons/year or one 40 cy compactor per week).

Decision Making Steps

To give businesses a starting point, Tetra Tech provided the following set of questions for a business to ask, to help them choose which option best suits their needs:
How much organic material do we produce?
What type of organic material do we produce?
How much space do we have?
How much labor is required?
What sort of corporate sustainability benefits can we expect?
How close will we get to producing compost?
How much will it cost?
The amount of organics produced is the first determining factor for filtering options. If an establishment fills a 40 cy compactor of organics each week, obviously a small in-vessel system wouldn’t be sufficient (Table 1). Most options are scalable to some extent, but in general, smaller producers are more likely to be looking at storage or pretreatment and larger producers may need to look at higher capacity systems.

Figure 1. Type of organic material and on-site management options

Figure 1. Type of organic material and on-site management options

The amount alone doesn’t dictate what options might be applicable; the type of organic material is also important. Some systems have limitations on what type of material can be accepted (Figure 1). Bioplastics and yard and garden debris in particular can cause problems in some systems. Harder items, such as bones, may negatively impact mechanical parts in some systems. When determining acceptable materials, it is best to confer directly with the chosen technology provider, and, if the organic material will be sent to a local processor, what’s accepted at that facility should also be verified.
Space is the most important selection factor for businesses located in a dense urban core. Good intentions aside, if the system can’t fit into the space you have, with room to load, unload, and store any input, output or bulking agent material, it’s not going to be viable. Pretreatment options are well suited to a small footprint as they take up less space compared to other technologies reviewed. Our report estimated that a dehydration unit uses about 10 square feet (sq. ft.), and a dewatering unit uses 2 sq. ft. Aerobic in-vessel systems can take up as little as 20 square feet (and up to >300 sq. ft.), and new anaerobic systems are starting to make their way into the smaller market, but generally, the in-vessel composting and digestion options require more space. By comparison, a 64-gallon rolling cart uses 5 sq. ft., a yard container uses about 30 sq. ft., and a roll-off container uses about 160 sq. ft.
While some businesses might have space, do they have time to maintain an on-site system? Most staff are accustomed to throwing material into a bin — but what happens when a system needs to be installed and maintained? Minimal effort is required for basic operation of a pretreatment unit, where starting the process may be as easy as pressing a button. However aerobic in-vessel and anaerobic in-vessel systems often require careful monitoring of process parameters, addition of bulking agent or moisture, and routine maintenance to keep things running smoothly. The larger systems may even require a full time operator.

Figure 2. Sustainability benefits

Figure 2. Sustainability benefits

Not all benefits are strictly tangible; some businesses are more interested in how they can help the environment, or how they can be perceived to help the environment. With this consideration in mind, more involved on-site processing options may be preferred. While pretreatment may reduce overall greenhouse gasses by reducing hauling, aerobic in-vessel systems are producing a usable end product and may eliminate the need for hauling altogether. Anaerobic digestion can also generate energy. In general, the more complex the process, the more sustainable benefits result and can be leveraged for public relations value (Figure 2).
For some businesses, especially those with a use for soil amendment, how close they will get to producing compost is an important factor. For pretreatment, most technologies produce a biomass which may look like compost, but lacks some of the “maturity” provided by an active composting process with a curing phase to follow. Aerobic in-vessel systems generally produce a “ready-to-cure” material, although some now claim to produce ready-to-use soil amendment. Anaerobic in-vessel systems are more complex with a solid digestate that may need further processing as well as a liquid component and biogas.
With these questions, businesses can essentially select what option works for them by a process of elimination. This leaves the final, and for many, the most important question: How much will it cost? While the marketplace is rapidly changing with newly emerging options, when looking strictly at capital and maintenance costs, storage is cheapest and anaerobic digestion systems are the most expensive. However, the cost of hauling adds another important layer for consideration, and the business case for many of these options becomes apparent.

Figure 3. Comparative analysis

Figure 3. Comparative analysis

For an overall comparison of all of these factors at a glance, Tetra Tech created a summary of key factors, ranked from mediocre to best, in a consumer report-style matrix (Figure 3).

Practical Example

So how would this work? Imagine a small restaurant in a busy downtown core. To begin to follow the decision making process, they measure their source separated organic material and determine that about two 32 gallon rolling carts per week are generated, which works out to about 700 kilograms per week (1,500 pounds) of organic material. Based solely on weight, the primary options that could be considered are storage, pretreatment, and small or medium aerobic in-vessel systems.
The back alley behind the restaurant is already tightly packed, as is the kitchen, so the restaurant can only fit smaller options, which effectively eliminates in-vessel composting. Another eliminating factor is the time required for in-vessel composting. With a small staff and a busy lunchtime rush, staff don’t have much time to operate an in-vessel system and therefore would most likely consider either storage or pretreatment.
The restaurant owner prides herself on being environmentally conscious and would like to choose an option that would help reduce her restaurant’s environmental impact. She doesn’t simply want organics hauled away, nor does she want them going down the drain. That means pretreatment will likely be the option of choice. A pretreatment system could reduce volume by up to 70 to 90 percent with a corresponding reduction in frequency of hauling. Cost savings could be even greater if the restaurant were to partner with other establishments nearby to reduce capital cost of a pretreatment system.
All types of businesses could follow these same steps and determine different options suitable to their situation. Then, by contacting individual distributors, they could price out different options and more specific features, and soon have their own organics management systems up and running. The full report, “On-Site Organics Management Options Review,” was published in Fall 2014 and is available on Metro Vancouver’s food scraps landing page under each sector’s Tools and Resources link. Although the report was designed with commercial establishments in mind, this guide may also come in handy for multi-family buildings containing at least 50 units. With this decision-making tool in hand, a business’s perception of the organics disposal ban can shift from logistical headache to a new opportunity to reduce waste and benefit from positive publicity.
Terry Fulton is an Environmental Engineer with Tetra Tech’s Solid Waste Practice. Veronica Baker is a Project Engineer with Metro Vancouver (BC’s) Solid Waste Services Department.
Table 1. Organics generation and bin sizes, quantities

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