We Tested 6 Countertop Composters. None Are Worth Buying. | Reviews by Wirecutter

By Sabine Heinlein

Sabine Heinlein is a writer covering floor care. Keeping her multi-pet home clean is one of her more acceptable obsessions.

Turning your everyday food scraps into garden gold is an appealing concept: Spend between $180 and $1,000, plug in your food recycler, dump in your leftovers, and press a button. Voilà, you’ve got compost—or fertilizer—for your garden.

Look at you, doing your part for a greener and better world!

If only it were that simple.

These food recyclers—often referred to as countertop composters—don’t actually produce compost. Yet the companies behind these machines have some awfully big marketing boasts. “Be an Eco-Warrior With the Push of a Button,” crows FoodCycler. “Fight Extreme Poverty Through Tree Planting And avoid methane emissions through composting with Reencle!” this company gushes in an unconventionally capitalized marketing statement.

I spent six months testing six different food recyclers, including the Lomi 2, Airthereal Revive Electric Kitchen Composter, Mill Food Recycler, Reencle Home Composter, FoodCycler FC-50, and its larger cousin, the FoodCycler Eco 5. I also sent my “compost” to an agricultural lab for testing and conducted a plant germination and growth test in my basement. I spoke with numerous experts, and I even started a worm farm in my apartment, to compare the effort and output with those of my devices.

Here’s what I learned about these machines:

When presented with the results of our extensive testing, some of these food-recycler companies half-conceded some of the points. Others adamantly disagreed with our conclusions. You can see their responses in detail in the sections on Lab analysis results, The stuff makes lousy fertilizer, Bioassay test results, and Does using a food recycler actually help the environment?

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Food waste makes up nearly a quarter of all solid municipal waste in the US. The Environmental Protection Agency estimates that Americans waste over 66 million tons of food per year, more than half of which ends up in landfills. A whopping 40% of this is from food we throw away at home, while the remainder comes from restaurants, institutions, supermarkets, and so forth.

In landfills, rotting food emits more greenhouse gasses than all other landfilled materials combined.

So it’s no wonder that climate-anxious consumers have been won over by food recyclers. Take, for example, Vanessa Johnson, the web developer who invested in a Lomi—one of the most recognizable electric food recyclers on the market—after a worm-composting experiment in her Miami high-rise apartment had gone awry.

“I was trying to focus on being better with renewable stuff and being better for the environment,” Johnson told me. “We only take out the trash now once a week—if that—because there’s no food going into our trash can anymore.”

Thanks to the Lomi, which grinds and dehydrates food scraps, Johnson’s trash can is now odorless, and the flies have packed their bags.

But some companies also say that food waste, after it’s processed in their machines, can be used as compost or fertilizer, or even as chicken feed (in the case of Mill).

And while the reduction in trash volume and trash stench is real, the direct environmental benefits of these devices are questionable.

At first sight, most food recyclers are reminiscent of an ice cream maker: an outer shell with controls, a lid, and a removable “bucket” with one or two blades that grind up food scraps. An internal heating mechanism dehydrates the scraps until their volume is reduced by up to 90%, which, depending on the model, takes between three hours and several weeks.

Most models simply dehydrate and grind. But the Lomi provides microbial tablets, and the Reencle includes sawdust inoculated with microbes, both of which promise to speed up the decomposition process. Some machines can break down bones as well as dairy, and the Lomi claims to process even bioplastics.

The machines weigh between 17 and 50 pounds, and sizes vary from that of a small countertop air fryer to a home-office paper shredder. The machines’ buckets hold anywhere from 2.5 to 14 liters of scraps.

At around 45 to 50 dB, the Mill and both FoodCycler models were so quiet that I forgot they were running. Others were quiet-ish, mostly staying in the mid-50s—comparable to my Miele exhaust fan—but they were prone to periodically emitting a symphony of ghastly screeches, gurgles, and donkey bellows, upping the volume to 70 dB and above.

All of the test machines included carbon filters that are supposed to absorb odors. The stench ran a wide range, with some machines emitting little to no odor. But the Airthereal outright stank, sometimes like an old, booze-soaked couch and other times like a dead animal. We also sometimes noticed a funky smell emanating from the Reencle and the Lomi machines. (I should note here that my household is vegetarian and that we didn’t add animal products, other than eggshells, to the machines.)

The finished grounds resemble a patch of dry autumn leaves trampled to various degrees. While some machines’ yield was the size of coffee grounds or rice flakes, other models left small strips of recognizable shelled corn husk and 4-inch-square pieces of watermelon. The smaller you chop up your vegetables, the finer the grounds, but the chopping adds labor to a process that’s supposed to be simple.

Depending on what you put in the machine, the dehydrated output smells neutral, earthy, or fruity. (Ours often had a nutty, sweet smell, presumably because of the amount of bananas we consume.)

The machines’ energy consumption was comparable. For example: ConEd charged me $47 for 137 kWh of electricity for the month that I continuously ran the Reencle in my house in New York City. Using a TP-Link Kasa Smart Wi-Fi Plug Slim to measure, I noted that the Reencle had used 30 kWh, which translates to roughly $10 per month in New York (similar to an energy-efficient refrigerator).

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To test the Lomi, Airthereal, Reencle, and FoodCycler machines, I processed dozens of pounds of food scraps in each model, including onions, leafy greens, watermelon rinds, eggshells, and coffee grounds. The Mill, which we kept in Wirecutter’s test kitchen because of its heft, also processed bones, dairy, and assorted cooked leftovers.

I sent the output of several machines to the Agricultural Analytical Services Laboratory, at Penn State University, to analyze pH, carbon-to-nitrogen ratio, percentage of solids, and moisture content—values that tell us how far along the dehydrated scraps are in the composting process and how useful they are as fertilizer. The lab also tested how much carbon dioxide the stuff was emitting, a further measure of decomposition.

As a passionate gardener, I experimented with the machines’ output in my yard, and I conducted bioassay (germination and growth) tests under grow lights in my basement.

And I ran a worm farm to compare the fertilization power of worm poop (known by the euphemism “castings”) to that of the output from the machines.

I interviewed more than 15 soil scientists, company representatives, and Lomi and FoodCycler users about their experiences, composting methods and standards, and sustainability claims.

I studied the companies’ sustainability claims and, if applicable, their studies, scrutinizing their designs, results, and funding methods, and peppering sometimes-recalcitrant company representatives with questions.

Composting is a natural process that transforms food scraps and yard waste into nutrient-rich soil.

I’m familiar with this because I compost in my backyard. The process begins by mixing one part nitrogen-rich green matter (vegetable and fruit scraps) with three parts carbon-heavy brown matter (dry leaves, small twigs, and shredded cardboard) in a vermin-proof, two-chamber compost tumbler. As microbes like fungi and bacteria feast on the organic matter over several months, the “feedstock” heats up and is turned into compost, a nutrient-rich soil that fertilizes plants.

“Finished compost should look like soil,” Sintana Vergara, an associate professor of environmental engineering at Swarthmore College, explained. “You should not be able to see what you started with at all. It should look like beautiful, dark brown, rich stuff, and [...] smell like rich soil. If you squeeze it between your hands, you should have a little bit of dribbling coming out.”

It’s fairly established that these machines do not produce true compost. Yet some food-recycler companies, including Airthereal and Reencle, market their machines as “composters,” calling the output “compost” and the breakdown process “composting.” Despite online criticism, Lomi continues to suggest in some of its marketing copy (albeit inconsistently) that its output is akin to compost. While I was reporting this piece, the company claimed on its main page, “It's like composting, but way easier.”

FoodCycler points out that “electric food waste recyclers are not composters, nor do they produce compost or soil.” Yet the company maintains that its recyclers offer “an ideal alternative to composting” and the output can be used as “plant fertilizer.”

With assurances like those—and following the companies’ instructions—I worked some of the dehydrated vegetable and fruit grounds into the topsoil in my yard. I had done this with the output of my compost tumbler numerous times, so what could go wrong?

A lot, it turns out.

After a hot and humid week, the area was speckled with patches of mold. Rain had swollen the formerly dehydrated vegetable scraps like decomposing bodies. I raked the area and added more grounds in another corner of my yard. A few hours later, while working in the yard, I spotted my cat Gilbert mesmerized in front of the freshly “fertilized” patch, watching—you guessed it—a family of rats boldly munching on vegetable-and-fruit chips.

When I told Lindsey Slaughter, associate professor of Soil Microbial Ecology and Biochemistry at Texas Tech University, my rat story, she said, “If it was dehydrated food scraps, there had been no physical or chemical transformation of those materials. It was still food scraps, even if it was dry. I’m sure that was pretty, pretty delicious to the urban wildlife.”

But the rats’ visit did raise a good question: How far along in the decomposition process exactly were my vegetable scraps? To find out, I prepared samples of food waste output from the FoodCycler FC-50, the Reencle, and the Lomi 2, and I sent them to the Agricultural Analytical Services Lab at Penn State University.

For the samples, I processed the Lomi feedstock both with and without the included microbial tablets, and I ran the device on Grow mode, a 16- to 20-hour cycle that Lomi says produces fertilizer.

I omitted samples from the Mill machine (the company doesn’t claim to make compost or fertilizer) and from the Airthereal Revive (too smelly, plus some leftover sardines in our test kitchen had turned the device’s bucket into a crusty, uncleanable mess).

Once I got the results, I shared them with several experts.

While there were some variations, the lab’s findings—including high percentages of organic matter, carbon-to-nitrogen ratios, and carbon dioxide respirometry results—all confirmed that this stuff is far from what could be considered finished compost.

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Interestingly, the test results for the Lomi grounds that had been processed with microbial tablets were identical to those without them.

“Microbes don’t actually live on solid surfaces,” explained Robert Pavlis, author of Microbe Science for Gardeners: Secrets to Better Plant Health. “[L]iving microbes need a thin layer of water around them to keep them alive. If you dry them out, they either die or go dormant.”

In the carbon dioxide respirometry test, the output from the Reencle machine fared the best among the models whose output we had lab tested. “[T]his output likely got further along in the natural compost process but isn’t finished either,” said Gina Talt, food systems project manager at the Sustainable Composting Research at Princeton (S.C.R.A.P.) Lab. But Talt explained that its comparatively high carbon-to-nitrogen ratio is problematic because as the microbes continue processing the carbon, they will temporarily steal nitrogen from the soil, depriving the plant of needed nutrients during a critical growth period.

Pavlis said that the claims of some companies—that their recyclers make “compost”—are “a huge red flag because people are buying these machines thinking they’re going to make compost.”

When asked about their use of the terms “compost” and “composting,” Airthereal said it considers the Revive Electric Composters’ output “pre-compost rather than a fully-formed fertilizer.” The maker of the Reencle Home Composter responded that “compost and composting are imperfect terms because of the variability in the process.” And FoodCycler and Lomi did not directly answer my questions about their use of these terms.

Mill’s marketing pitch is more transparent, though still imperfect. Suzy Sammons, head of marketing at Mill, made sure to tell me that the company doesn’t claim that its food recyclers’ “dry-and-grind system” produces compost, “because it is scientifically impossible to compost overnight on your countertop or without extra steps.” Although the company doesn’t state that you can add the grounds to your potted indoor plants, it does claim that you can mix “nutrient-rich grounds” with soil, let it cure for two weeks, and then use it in your garden. But this seems dubious.

For one thing, Mill also states that you can feed the grounds to chickens, which brings us back to the rats: If it’s a hit with chickens, I’m pretty sure that New York City rats are ready to place their orders! And for another thing, grounds from several of the machines we tested proved pretty terrible for growing plants, even after “curing.”

So this stuff clearly isn’t compost. But can you still use it as fertilizer?

All of the companies whose machines we tested (except Mill) suggest that you can. In their marketing copy, both Reencle and Airthereal call their machines’ output “fertilizer.” FoodCycler alternatively refers to its output as “nutrient-rich soil amendment” and “Foodilizer.” Lomi says its machines, if run in Grow mode, produce fertilizer, and it refers to the output as “Lomi Earth,” which can supposedly be added to your garden and your potted plants.

Pavlis said the use of the word “fertilizer” is “incorrect terminology.” Generally, commercially sold fertilizers are regulated to ensure they are safe for people to use, and the manufacturer must list the proportions of nutrients, including nitrogen, phosphorus, and potassium. Referring to the term “Lomi Earth,” Pavlis added, “And it’s not earth either. To be earth, you really have to have sand, silt, and clay in it, and there’s no sand, silt, and clay in it.”

I decided to put the machines’ outputs to the test by conducting a bioassay, a test of germination and plant growth, at home.

To prepare, I closely followed each company’s instructions. Lomi, for example, requires that you don’t process any meat, fish, or dairy if you plan to use the output on plants. And Reencle requires that you stop adding new food scraps to the recycler 48 hours before emptying it, and then letting the output cure for three to four weeks in an open container before using it on plants. FoodCycler, too, wants you to cure its machine’s grounds before adding them to plants.

I mixed equal amounts of Earthgro topsoil with the company-prescribed amounts of identical food grounds. For example, I mixed one cup of topsoil with a tenth of a cup of Lomi grounds, processed in Grow mode, with the microbial tablet, another cup of soil with the Lomi grounds without the tablet, and one cup of topsoil with an 11th of a cup of FoodCycler FC-50 grounds.

I also created two control groups: one with topsoil alone and one with worm castings from the worm-farm experiment I was simultaneously conducting.

I buried 10 radish seeds at a depth of half an inch in each of the six pots I had prepared, repeating the bioassay experiment with 10 barley seeds buried at a depth of 1.5 inches.

I watered the soil and turned on the grow lights, ensuring the room temperature didn’t exceed 75 °F. Over nine days, I noted germination rates and dates, plant health, and growth.

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On day two, a strong, rotten smell emanated from the pots that contained FoodCycler and Lomi grounds.

On day three, mold had grown on the FoodCycler, Lomi, and Reencle plantings.

By day four, fruit flies had joined the party.

That same day, several radish seedlings and a couple of barley seedlings emerged from the soil-only and the soil-plus-worm-castings samples.

All in all, the food-recycler machines’ material was reliably the least likely to yield robust seedlings. The control groups (soil-only and soil with worm castings) had the highest germination and growth rates, and those groups’ plants had the strongest, most anchored roots.

The Reencle and Lomi samples performed the poorest. In fact, no radish seedlings emerged at all from the Lomi-with-microbes sample, and zero barley seedlings cropped up from the Reencle sample. The roots of the seedlings that did emerge were less anchored, and the colors of their leaves/blades were, for the most part, a sickly yellow.

Our conclusion: Food-scrap material from these machines seems, at best, useless at fertilizing, and when it’s applied to soil, it can actually harm your plants.

Vergara explained that you don’t want to use food scraps on plants before the material has fully decomposed. “If you apply it to soil, it’s actually going to take nutrients from your soil,” she said.

When asked for comment about the growth test results, Reencle responded that the company has conducted “numerous germination tests in Korea with independent labs with positive results.” The spokesperson also said that it has a research study at Brigham Young University underway to show its machine’s output can be used to grow vegetables.

Lomi sent me one of its non-peer-reviewed studies, conducted by a consulting firm hired by the company. While the study showed some positive results where Lomi grounds were combined with bulking agents and inoculation of naturally occurring soil microbiome, it also said these benefits were not apparent when poor-quality soil was amended with Lomi Earth. (Another study by the same firm came to a similar conclusion.) The study’s summary suggested that “there appears to be an important interaction between Lomi Earth and a diverse soil microbiome that results in greater soil health and enhanced plant growth.” However, the study also found that the Lomi pods and bulking agent did not result in higher growth. In other words, whether your plants will grow, wilt, or die depends on the soil’s microbiome, a variable that’s hard to control for most users.

FoodCycler responded to our request for comment, saying that its machines’ output “can inhibit germination in some seeds sensitive to electrical conductivity,” but it added that once a plant is established, the grounds can support and increase plant growth.

Plant growth aside, the output may also pose a health safety issue, depending on the food scraps you add to your machine. According to the FDA, vegetables and meat count among the most likely sources of E. coli.

A machine’s internal temperature and the time it takes to process scraps both play a role in safety. Compost reaches a temperature of up to 150 °F, and the food-safety “danger zone” lies between 40 °F and 140 °F. (E.coli can survive in even higher temperatures.)

Lomi declined to share the internal temperatures of its machines, but the other companies told me that internal temperatures range between 140 °F and 284 °F.

Ideally, the machines get hot enough to kill harmful bacteria but not so hot that you’re killing off beneficial bacteria. If the temperature is too hot, there’s a tradeoff: “You might be getting rid of a lot of the beneficial bacteria, who are the guys doing all this work, the ones that are doing the decomposition,” Vergara said.

This question has been tormenting me: How much food do these dehydrators really divert from landfills? And how much greenhouse gas emissions are thus avoided?

One thing is very clear: The amount is not nearly as much as some of these companies claim.

Take Lomi, for example, which makes some of the biggest environmental claims of the companies whose machines we tested. I asked Lomi to explain the company’s claim that its recyclers have helped to divert up to 340 million pounds of food scraps from landfills. This number, a spokesperson told me, is based on results from over 200,000 Lomis being used in US households for two years, with each household processing 2.2 pounds of food waste per day.

When I questioned the company’s math, Lomi quickly revised the figure of food scraps saved from landfills between January 2022 and January 2024, lowering it from up to 340 million pounds to up to 260 million pounds. However, the company continued to use the assumption that each Lomi user had diverted 2.2 pounds of food waste per household per day from the landfill during this period.

When asked for the origin of its 2.2-pounds-per-household figure, Lomi cited an EPA document that did not actually include this number. The company did not respond to our specific questions about the exact numbers behind its calculations when we asked again later, so we did the math ourselves.

According to the EPA, the average US household produces about 338 pounds of food waste a year, which breaks down to less than 1 pound per day. (Don’t forget, this represents only 40% of total food waste; the other 60% originates from restaurants, institutions, and supermarkets.)

For the sake of argument, let’s assume that Lomi sold the 200,000 machines currently in people’s homes in January 2022 (highly unlikely), when the machines first became available. Let’s also assume that the machines’ owners processed all of their household food waste in those machines for 24 months (also highly unlikely, particularly since there are dozens of food items, including oils, large bones, and nutshells, that the Lomi cannot process). Even under these most optimistic circumstances, Lomi machines would have saved only about 134 million pounds of food waste from landfills, about half of what the company claims.

But even this number appears highly implausible considering that if you opt to use the machine’s Grow mode to create, in Lomi’s words, “a natural fertilizer,” you must exclude dairy, meat, bones, and grains.

The accuracy of Lomi’s food-waste numbers matters, since they are a critical figure in avoided-greenhouse-gas-emissions calculations. On its site, the company touts an avoided-emissions figure of 169 kg CO2e (carbon dioxide equivalent), which Lomi told us in an email was determined by a hired consultancy. According to Lomi, this figure assumes that “the Lomi Earth (end product) is used at home” compared with the “transportation and disposal of the same food waste in a landfill.”

This point is clear: If your goal is to reduce greenhouse gas emissions from your food waste, it’s most important that you make sure it does not end up in the trash, after which it will be landfilled or burned. Landfilled food waste contributes to greenhouse gas emissions, most potently in the form of methane. But you don’t need a machine to compost.

Still, there are some potential environmental benefits to using these machines. Several of the experts we consulted said that the dehydrators may potentially help make people more aware of their food waste.

“If it helps them engage in more pro-environmental behaviors, it’s a win,” said Gina M. Talt, the food systems project manager at Princeton University’s S.C.R.A.P. Lab. But, she added, “A lot of people forget that the biggest way we can have an impact is to stop the waste of food upfront and … don’t just have leftover food that goes bad.”

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Based on our lab results and planting tests, we can confidently say that adding food-recycler grounds to your garden or potted plants is a bad idea. But some people might still find a use for them.

You can use the output to speed up compost. You could mix the dehydrated matter with browns (cardboard or dry leaves) and add them to an existing compost pile. But you’d have to add water because the microbes that are digesting the matter like it moist.

“Something that is actually grinding that material down for you does help kickstart that composting process,” Lindsey Slaughter said. “So it would speed up the overall time needed for composting.”

You can use them to pause composting in winter. These machines might also come in handy during cold winter months, when your outdoor compost bin fills up faster than your compost breaks down. Since the dehydrated food scraps can be stored for several months, you can save the stuff until the weather is warm enough for your compost microbes to return to work. But, again, you will have to add water—another crucial resource in addition to the electricity needed to run the machines.

You can use them to reduce your trash volume. Around 10% of US municipalities have adopted a pay-as-you-throw program, in which residents are charged for the collection of household trash according to weight or volume. And dehydrating your food waste by 75% to 90% can certainly make a difference in the heft of your trash. But critically, if you still throw the grounds in the trash, you do nothing to reduce your environmental footprint. Your (smaller) food scraps will likely end up in the landfill or be incinerated.

Composting expert Xavier DeRoos, founder of composting service Renüable, said if you don’t do backyard composting, it would be best to pair your food recycler’s output with a composting program, to properly divert the material from the landfill. He suggested contacting your municipality and asking about municipal composting programs or community composters in your area. Otherwise, he said, “the methane is still being produced and just released in a separate timeline.”

You might donate the stuff to chickens. Mill takes the guessing game out of what to do with your scraps by offering an alternative model. Although you can add the Mill grounds to your existing compost, your municipal garbage, or your green bin, there’s an alternative approach. For a $10 monthly subscription fee, you can order prepaid, plastic-lined boxes from Mill, have USPS pick them up, and send them to Mill. The company gives the grounds to small farms, which use them as chicken feed, a recycling method that’s more beneficial than composting, according to the EPA’s Wasted Food Scale. (You can also feed the grounds to your own chickens.)

If you’ve been curious about these machines because you want to do something good for the planet, these food recyclers are probably not the way to go. Try to waste less food. Start a backyard compost. Or look for composting options in your area, such as farms, community composting programs, or microhaulers that pick up food scraps. Chances are good that there are options nearby, so your ice cream maker doesn’t have to fight for counter space with yet another newfangled kitchen appliance.

This piece was edited by Ben Frumin, Katie Okamoto, and Marguerite Preston.

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Dr. Lindsey Slaughter, associate professor, Soil Microbial Ecology/Biochemistry, Texas Tech University, video interview, April 8, 2024, email interviews, May 22, 2024 and July 1, 2024

Xavier DeRoos, owner/founder of Renüable, video interview, April 12, 2024

Dr. Anthony Lau, associate professor, Chemical and Biological Engineering, University of British Columbia, video interview, August 15, 2024

Robert Pavlis, author of Microbe Science for Gardeners, video interview, May 3, 2024, email interview, May 3, 2024

Gina M. Talt, food systems project manager at the Sustainable Composting Research at Princeton (S.C.R.A.P.) Lab, video interview April, 11, 2024, email interview, July 12, 2024

Sintana Vergara, associate professor, Swarthmore College, video interview, April 8, 2024

Stefano Carattini, assistant professor, Andrew Young School of Policy Studies at Georgia State University, video interview, May 30, 2024

Suzy Sammons, head of communications and marketing at Mill, email interviews, April 2 and April 9, 2024

Samantha Eves, director, marketing and consumer experience, Lomi, email interviews, July 9, July 23, August 7, and October 10, 2024

David Kim, COO, Reencle, email interviews, May 3, July 30, and August 1, 2024

Sabine Heinlein

I’m a senior staff writer on Wirecutter’s home appliance team, where I cover all kinds of vacuum cleaners. I’ve also ventured into the wild world of bunny care, vacuum cleaner enthusiasts, and basement flood prevention. Keeping my two-cat, two-rabbit home clean is one of my more acceptable obsessions.

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