Guide to equipment and systems for businesses, institutions and venues that manage food waste on-site.
Businesses, institutions and venues that generate large volumes of food waste have an increasing number of options to manage this organics stream, starting with tools and knowledge to prevent and reduce what is generated in the first place, followed by donation of excess and prepared foods that are still edible. Then comes the question of what to do with the rest. And depending on where these facilities are located, they may not be allowed, by law or regulation, to throw it away with their trash.
Many generators opt to source separate their organics, which are collected for composting and/or anaerobic digestion. But over the past decade, the marketplace has also responded with equipment and systems to manage food waste on-site. The equipment falls into three broad categories:
Dehydrators: Use heat (thermal process) to evaporate the liquid in the food waste; Output is a dry biomass often described by vendors as ready-to-use soil amendment or plant fertilizer.
Liquefiers (also sold as aerobic biodigesters): Utilize fresh water and often biological additives (e.g., enzymes or microbes) that reduce the biochemical oxygen demand (BOD) to meet municipal wastewater limits for discharge to the sewer. BOD is a measure of the amount of oxygen required to finish breaking down the organic material left in the residual liquid.
In-vessel &#;accelerated composting&#; units (4-7 days process): Typically require an amendment such as sawdust; Output described by vendors as ready-to-use compost.
All three of these categories are essentially pretreatment systems for food waste, i.e., they biologically or thermally treat the food waste versus only mechanically reducing the volume via maceration or slurrying (preprocessing). In each case, a final management step is required, either curing the dehydrated biomass or compost output until it is biologically stable, or utilizing the municipal wastewater treatment plant in the case of the liquefiers.
Each technology is a volume and/or weight reduction step, which minimizes or eliminates the need for frequent food waste collection. In a state like Massachusetts, which has a disposal ban for commercial organics (generating 1 ton or more/week), utilizing an on-site system may help a generator stay under the 1 ton/week threshold, and thus continue to utilize disposal for what remains.
Based on our research, only a few vendors of in-vessel composting systems designed for use on site at a business, institution or venue, state that finished compost (meets a scientifically robust test for stability) is produced in 7 days or less. The majority state that their process meets pathogen and vector attraction reduction in the vessel (55°C for 3 days), but that additional curing/maturation is needed prior to use. The latter is what is recommended, and thus space should be available on-site or off-site for the curing phase.
For businesses, institutions and venues with space constraints for collection bins, reducing the volume of food waste can be a significant advantage. Dehydrators and liquefiers have built in shredders or grinders to size reduce the food waste prior to treatment. Usually, this equipment is installed in the kitchen prep or dishwashing area, so staff does not need larger wheeled containers to transport food waste to the unit.
Both types of equipment need power hook-ups; the liquefiers also utilize fresh/potable water. As noted, most liquefiers discharge to the municipal sewer. Dehydrators will have process wastewater that must be managed. Some systems can be fed continuously; others operate in batch mode (cycles). Vendors of liquefiers should provide documentation on the BOD and total solids of the treated food waste to ensure it meets the discharge limits set by the wastewater treatment plant. (Prior to purchasing or leasing liquefiers, food waste generators should check with the local wastewater authority to see if this equipment is allowed).
The Center for EcoTechnology, which manages the Massachusetts Department of Environmental Protection&#;s RecyclingWorks program, surveyed vendors of on-site food waste management equipment to provide basic details about their machines. The final document serves as an initial guide to these systems, including dimensions, power requirements, capacity, additives, etc. It does not, however, list daily water usage (for liquefiers), or properties of the outputs, such as BOD levels or product maturity.
Food waste generators in the market for this type of equipment can reference BioCycle&#;s two-part article series on dehydrators and liquefiers (biodigesters) in October and January (tables available in print version only).
The California Department of Resources Recycling and Recovery (CalRecycle) has excellent guidance documents on food waste dehydrators and liquefiers. In California, state regulations do not define dehydrated food waste any differently than unprocessed food waste; it is considered a solid waste and must be handled as such. CalRecycle&#;s guidance on dehydrators states the following:
&#; Dried food waste is not compost or a compost product. Food waste dehydrators do not use a biological process to reduce pathogens and decompose food waste into a stable substance.
&#; If it becomes wet again, the dried food waste can reabsorb water. At this point it will have similar characteristics to unprocessed food waste, meaning it can attract vectors and create odor.
To the best of our knowledge, there is no independent, third party evaluation of any on-site food waste management systems. Therefore it is critical to ask vendors for reference installations that can be toured. The Composting Collaborative is preparing a checklist of questions for food waste generators to ask during these site visits.
Nora Goldstein is Editor of BioCycle. Charlotte Dreizen is a Project Associate with GreenBlue, a nonprofit that seeks to advance the sustainable materials economy. GreenBlue and BioCycle, along with the US Composting Council, are founding partners of the Composting Collaborative, an initiative to unite composters, consumer-facing businesses, and policymakers, among others, to share best practices and resources, as well as generate innovative solutions to shared challenges. CompostingCollaborative.org
Waste collection systems range from the smallest undersink garbage disposers to larger, remote pulping systems that include a built-in grinder to send trash through pipes with water. This creates a slurry or sludge that then goes down the drain to the sewer system/water treatment plant.
In some cases, larger operators might use a pulper/disposer aided by a water-assisted scrapper (fitted under standard sinks) in the dish room to rinse off and collect food waste from plates into a tank with greater speed and efficiency than by hand. Waste collectors can double or triple scrapping outputs without adding labor in the dish room and reduce food waste solids by 50 percent to 60 percent. They can also reduce water use at the prerinse stations because waste collectors use recirculated water with optional built-in shut-off timers.
While operators typically use them in conjunction with disposers or pulper systems, scrappers can also work in conjunction with compost programs instead of sending the food waste down the drain. Operators can elect to fit grinders with a lift-out basket to dispose solids in compost bins rather than sending them to a digester to become a slurry that would go down the drain.
Installing a durable, high-powered commercial disposer to send pulverized scraps, bones and more down the drain where it&#;s treated at a local facility is one of the easiest and most inexpensive ways operators can dispose of their food waste. It also helps divert organic material from landfills.
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But it&#;s not always simple.
The lines of the debate around disposers remain heavily divided. Proponents of disposers say they offer a simple, inexpensive way for operators to avoid throwing food in the trash and are especially helpful in parts of the country where composting is challenging or costly. They can also cut down tremendously on hauling fees.
Critics of the equipment, however, argue that municipalities should take a closer look at their water treatment facilities to ensure they can continue to withstand increasing waste loads from commercial operations over time. Some water treatment facilities these days seem to have trouble with this scenario. Critics of disposers in commercial applications, including those in California, also cite the enormous amount of power and water consumption that disposers create because of the need for all the water treatment.
Some environmentalists, and disposer critics, argue that instead of having wasted food literally go down the drain, why not try to recapture that waste and turn it into something good, such as a soil amendment, to further try and close the food waste loop? In fact, that's a positive development in the area of waste management.
Many anaerobic digestion (AD) facilities also reuse food waste by converting it to a slurry that can be treated or turned into a soil amendment, while capturing methane to create natural energy sources. To add more complexity to the mix, should an operator choose to send its food waste to an anaerobic digestion facility, it&#;s in their best interest to ensure that the AD facility then responsibly handles the slurry the process creates. This slurry, when treated with the right enzymes, can serve as a soil amendment to help grow more sustainable vegetables. It&#;s important, however, for the operator sending the food waste to the AD system to ensure that the slurry doesn&#;t just go down the drain either, assuming &#;closing the loop&#; is of importance to the operator. According to a study report by the Environmental Protection Agency and the East Bay Municipal Utility District, food waste produces three times the biogas compared to sewage sludge, and the biogas produced from AD systems exceeds the cost of processing the food waste and disposing of the residual bio solids.
New York City alone operates 14 water treatment facilities, each of which features an anaerobic digester. Still, reports show that New Yorkers continue to seem reluctant to install disposers in the past 20 years since the ban was lifted, partially due to cost, but also because many might not realize they&#;re actually legal.
Some foodservice professionals consider pulpers a more eco-friendly alternative to garbage disposers. These units grind up waste and remove water to reduce a foodservice operation&#;s waste stream.
Pulpers can link to on-site dehydrators, which remove more water to create a lightweight, powdery substance that reduces hauling fees, but that can also be sent to a composter for further treatment to become a soil amendment. That extra step is key if an operator wants to take the most environmentally friendly route.
Large commercial pulpers utilize big cutting disks, a water press, a recirculating trough system and a 7 to 10 horsepower motor to consolidate and remove wet waste from disposables. There are two pulper categories. Close coupled, or standalone systems, are less expensive and don&#;t require a custom build. The pulping and water extraction are facilitated at the same place. This results in a less complicated installation and less cleaning overall because there are no remote lines that have to be maintained.
Remote systems make up the other pulper category. They utilize a macerating chamber that grinds food waste, then pumps it to a water press in a remote location, such as a back dock, pulp collection room or somewhere away from the input area. Operators can fit this type of system with several macerators hooking into one water press. The discharge unit can be placed by the dumpster to save labor and additional grinding tanks can be added if there is more than one dish room. Operators also can have several grinding stations go to one discharge station when using a remote pulper. It&#;s important not to place plastics in the machine &#; only organics &#; to ensure the pulped material can be used as a soil amendment if that is the desired output.
Use of commercial garbage disposers remains a thorny issue among some environmental and municipal camps, but when used in conjunction with more AD systems at wastewater treatment plants, they can actually create more resources in the form of natural energy and soil amendments. Regardless, disposers alone are just one of the growing number of tools out there to divert food waste from landfills, which is the overarching goal of getting as close to &#;zero waste&#; as possible.
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