Waste Management Series: Food Waste Treatment and Disposal
Waste Management Series: Food Waste Treatment and Disposal
Courtesy: Amelia Levin | News Source: fesmag.com
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.
The Disposer Debate
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.
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 2011 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.