Composting Gets Wet

Jan. 4, 2014

From the 1920s until 1976, when Congress passed the Resource Conservation and Recovery Act, most household garbage was sent to what were then described as “dumps.” By 1986 there were 7,683 dumps in the United States. In 2009, the number of dumps, rechristened “landfills,” dropped to 1,908.

Despite the 75% decline in the number of disposal facilities, the US Environmental Protection Agency insists that total capacity has increased because the new municipal solid waste landfills, dubbed “megafills,” can accommodate significantly more garbage.

Although these larger facilities have significantly increased capacity, space is finite. According to “The State of Garbage in America,” a biennial assessment of America’s trash capacity compiled by BioCycle, an industry publication, available landfill space varies widely from state to state. Arkansas reports sufficient capacity for 600 years without the need to open another facility, but Massachusetts and Rhode Island estimate only 12 years of capacity remaining, and New York has only 25 years left, despite shipping most of New York City’s trash to other states.

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations.  6 Tips for Excellence in Landfill Operations. Download it now!

According to the EPA, in 2003 roughly 56% of the country’s trash was disposed of in landfills. A 1996 Environmental Defense Fund report estimates that 24 million tons of leaves and grass clippings could be composted to conserve landfill space. Foodwaste is the third largest component of generated waste, after yardwaste and corrugated boxes, and second only to yardwaste in discarded waste. The amount of foodwaste in the wastestream has increased by 1.2 million tons in the past 25 years. Although it’s one of the lowest increases of any component in the wastestream, it’s a significant number, a number that should be easy to reduce by diverting food and other types of wet waste to compost programs.

Beyond the Big Picture
But because of a misconception about potential issues caused by incorporating foodwaste, many municipal and commercial composting facilities have been reluctant to expand operations to include this form of wet waste.

Getting customers to participate can also be a challenge. “The super greenies already compost,” posits BioBag’s Jennifer Wagner, “but others don’t like the extra work and the “˜ick factor’ of foodwaste. It’s a huge challenge for the industry, a big hurdle.”

Agreeing with her about the reluctance to pay more attention to wet waste, Todd Dunderdale, sales and marketing director for Komptech USA Inc., says, “Historically, no one wanted to handle waste. We used to have scavengers do that job-typically, immigrants or the poor.”

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations. 6 Tips for Excellence in Landfill Operations. Download it now!  

Today’s hindrances to adding wet materials to composting operations include complications created by collection and concern about odor, pests, pathogens, water contamination, and public complaint.

Reluctant or not, we must address this wastestream. According to the EPA’s Municipal Solid Waste in the United States: 2007 Facts and Figures, Americans generated more than 254 million tons of waste in 2007. BioCycle magazine’s annual report, The State of Garbage in America 3, puts that figure closer to 413 million tons.

Whatever the exact number, it’s commonly agreed that 89% of what was sent to landfills could have been recycled and/or composted, but only 33% was. According to the US Composting Council, at an average waste disposal cost at $43 per ton, it would cost $6.12 billion to treat the EPA’s smaller estimate of trash, leaving 142 million tons of reusable resources unnecessarily buried or burned and greenhouse gasses and emissions generated from doing so.

The composting council advises viewing compost feedstock as a usable product instead of as waste that requires disposal. The council emphasizes that the composting process is “an environmentally sound and beneficial means of recycling organic materials, not a means of waste disposal.”

The purpose of composting is to decompose organic substances efficiently, without odor, and to convert them into stabile product through a rotting period that is as brief as possible, with emissions as low as possible. Biological treatment includes pretreatment, a closed, intensive rotting process and a post-rotting stage for stabilization.

End products can include biogas and liquid fertilizer. Clean energy produced from decomposed organic material is getting attention in a world suddenly concerned with rising energy costs and environmental protection.

The use of refuse-derived fuel has been prompted by regulations banning the landfilling of untreated waste, but there are other environmental-and economic-benefits to diverting organic material from the landfill. Incorporating foodwaste and yardwaste into composting programs creates a more nutrient-rich end product that becomes a valuable soil amendment that in turn reduces the need for chemical fertilizers.

Buried organics generate methane, a greenhouse gas 21 times more potent that CO2; diverting them reduces harmful greenhouse gas emissions. In addition to lowering emissions, composting conserves diminishing landfill space. According to the composting council, up to 70% of the MSW wastestream is organic material, with yard waste alone making up 20%.

Decreasing the amount of wet material in the wastestream also results in a significant reduction in tipping fees paid to landfills.

The Evolution of Composting
Most composting programs began with leaves and yardwaste, states Lori Scozzafava, executive director of the US Composting Council. Leaves fall at the same time, so it’s natural to collect them separately. “Traditionally, they were turned with bucket loaders,” she elaborates. “With more sophistication, there was a move to windrow turners for proper aeration.”

Next came grass, which posed new challenges because it is “very wet,” Scozzafava says. “There are issues in collection and composting. It heats up quickly when bagged and goes anaerobic quickly…which causes odor issues.” The facility needs a “level of sophistication” and must appropriately aerate in order to maintain proper temperature. She advises mixing in leaves to reduce odor and heat.

Now there’s interest in foodwaste, Scozzafava says. But “foodwaste is very different than a leaf program,” she cautions. Grass is a homogenous product, but food is mixed. New technology and the evolution of sophisticated processes are necessary to effectively manage it. Oxygen and water must be monitored to ensure adequate amounts are available.

The type of feedstock, space, and climate dictate the requirements. “There are differences in vegetation across the country that affect composting. In Florida, palmetto branches are more common than deciduous trees. In Arizona there is little yard debris.

Even collection can affect composting, Scozzafava notes. In order to control contamination, collection should occur more frequently where temperatures are high.

Because so many diverse factors can affect a site, the composting council has surveyed processes to develop a model for states to use in creating regulations. “We’re trying to standardize effects through permitting to create a uniform approach,” Scozzafava explains. The goal is to speed up the process because water runoff and air emissions affect the community. “We want the compost facility to be a good neighbor.”

To improve neighborly relations, the council offers training courses to instruct managers on the biological process so they can produce a stable product. For example, they learn that static piles benefit from forced aeration and that synthetic and organic layers help control the biological processes in covered piles.

Education is working. Scozzafava describes the move to include foodwaste in collection programs a “quantum leap” and mentions successful programs in cities like New York City, Cedar Grove, and Montgomery City, MD.

The Smell of Success
“Landfill space is diminishing,” confirms Komptech’s Todd Dunderdale. As it does, he predicts, permitting will become more difficult. He sees that as an opportunity to bring technology to the forefront. “We have solutions. Look to Europe. They’re ahead of the curve, with disposal rates near zero.” He ascribes that low rate in part to higher tipping fees. “The dumping rate is $300 per ton. That’s driving recycling.” In addition, as more companies use recycled materials, they become more valuable.

The “big push” now is foodwaste, Dunderdale indicates. Foodwaste makes up 30% of the wastestream, but has many uses. It is used for anaerobic digestion. Composted, it becomes bio-mulch or waste energy. When the liquid is separated from the solid, gas can be siphoned to create electricity. The rest is liquid fertilizer or liquid biofuel.

Numerous useful end products notwithstanding, collection is a “major problem,” Dunderdale says. “It’s a global economy, but we haven’t thought beyond collection. The problem is dealing with it. Processing is also a challenge. You have to have the right form, size, and contaminative.”

Komptech is an Austria-based manufacturer of equipment to process material for composting, specializing in removing contamination. Its product range includes shredding and separation technology. “When dealing with the wastestream, you must have the right equipment for the process,” Dunderdale explains. “For example, you can’t use a hay burner to grind greenwaste.”

The right shredding and separation technologies allow heavily contaminated market waste and expired food to be recycled alongside biowaste and food residue. After treatment, the substrate can be used in a wet fermentation process.

Screening and windsifting technology separates material designated for the landfill. After things like plastics and glass are removed, waste is shredded and mixed with air at an 80:20 or 4:1 ratio. Windrow turners provide the best aeration to mix the material in order to release the microorganisms, Dunderdale believes. “Odors are eliminated with microorganisms. Composting has no odor if you’re doing it right, but a lack of moisture or air, or too much heat can produce odor.”

Compost piles need structure for air flow and heat release. “It should be kept at 130 to 165 degrees for 15 days, turned five times in 15 days,” Dunderdale advises. However, if the level of moisture is high, the screens become sticky and wet, making it difficult to operate efficiently.

Optimally, proper composting procedures save landfill space, reduces methane emissions and provide organic material that benefits agriculture and increases water retention of the soil.

Success Stories
When the landfill in Edmonton, AB, filled up, the city needed a new plan. “The nearest landfill is 70 miles away,” Dunderdale says. “A 140-mile round trip, plus transport costs and tipping fees, got expensive, so they built a recycling facility on the landfill.”

Economics frequently drive the move to compost, but Dunderdale says municipalities often wait until the last minute before considering their options. One option that’s fading away is opening new landfills. “The cost of entry is too high for new landfills,” he explains. He says compliance with EPA regulations can mean startup costs of $20 million, leading to high tipping fees and more labor costs-and that doesn’t include the hurdles of the permitting process and public hearings.

The cost of oil is another economic driver. “There’s a lower cost to process wet materials than to put them in a landfill,” Dunderdale asserts. “You can save money on fuel and maintenance if you screen more and grind less.”

San Francisco found that out when it implemented its “Zero Waste by 2020″ program. Reaching the goal means no discards will be sent to the landfill; instead, all discards generated in the City by the Bay will be reused, recycled, or composted.

In 2000, San Francisco sent 872,731 tons of material to the landfill, diverting only 46%. After implementing the Mandatory Recycling and Composting Ordinance in 2009, which requires residents to separate recyclables, compostables, and landfill trash, the city’s disposal dropped to 475,800 tons-a 78% diversion rate.

The following year, further reductions in material sent to the landfill (444,000 tons) resulted in an 80% landfill diversion rate. “Everything gets easier,” Dunderdale comments, “but it takes education to overcome culture.” When good intentions aren’t enough, municipalities may have to turn to mandates like San Francisco did.

Good intentions must make economic sense. When Barnes Nursery Inc., a family-owned nursery, garden center, landscaping company and composting facility located in Huron, OH, added wet materials to its composting program, the company learned that the more foodwaste a facility agrees to manage, the higher the technology need must be. The company also discovered that large volumes of mixed food residuals would eventually be problematic at an outdoor windrow composting site that does not have improved surfacing and a closed area to manage putrescent waste.

The composting facility, which is open to the public, processes approximately 20,000 tons of materials, including about 8,500 tons of yardwaste, 500-1,000 tons of food residuals, wood, and aggregate materials. It produces compost and soil and mulch products that are sold in its retail center. In 2007 it began processing food residuals. Materials are managed via turned windrows, using grinders, conveyors, bucket loaders, and screeners.

The Class II composting facility collects food residuals from supermarkets, resorts, hospitals, schools, and food processing plants. Yardwaste and woodwaste were also collected. Because the Barnes plant experienced odor problems, it now covers the material upon arrival, shreds it right away, places the material in a windrow, and covers it with a biofilter of shredded yardwaste. Foodwaste that is “overbulked” with too much carbon becomes too dry to generate the necessary temperatures for decomposition, so getting the “recipe” right has also been a challenge, adding to odor issues.

But one of the more discouraging challenges is the cost of doing business. In addition to paying the state a licensing fee based on maximum daily allowable waste, Barnes Nursery must pay a $5 per ton fee on food residuals diverted from the county landfill to allow the county to recoup revenues lost as a result of diversion. The county loses money by supporting waste reduction.

As reported in the composting council’s publication, Best Management Practices for Incorporating Food Residuals into Existing Yard Waste Composting Operations, Sharon Barnes says it’s essential to find a win-win situation for all involved in diversion programs: the generators, the haulers, the landfill, and the composter. Otherwise, diversion programs won’t be sustainable.

It’s in the Bag
One of the often forgotten benefits of composting programs, Dunderdale points out, is that they create businesses in recycling. BioBag is a small company that manufactures certified compostable bags and films for the collection of organic waste for the purpose of composting. Made from plants, vegetable oils and Mater-Bi, the bags can be consumed by microorganisms in the soil, which allows them to be composted along with organic waste in municipal composting facilities.

In conjunction with Novamont North America, a company that finds new ways of using bioplastics-renewable raw materials made from plant matter-for specific applications that require biodegradable materials with low environmental impact, BioBag works with communities to implement “wet” composting programs.

So far, 200 communities have implemented such programs, says BioBag’s Jennifer Wagner. San Francisco’s green bin for organic waste is the preferred model, she says, but different communities handle it differently, with some offering drop-off collection.

“Different programs are rolling out,” confirms Rhodes Jepsen, marketing manager for Novamont. But it can become overwhelming. “A lot of communities try to recycle all materials.” Some, however, cautiously prohibit some things such as meat, dairy, and paper. Jepsen believes they may be confusing curbside collection with home composting, which doesn’t include animal products because, typically, it can’t achieve the high heat needed to kill pathogens and often attracts wildlife. “Curbside collection can handle any biological material. The direction is to allow everything.”

Even so, it can also be frustrating to get participation. “It requires a major behavior change,” Jepsen acknowledges. “The first landfill crises occurred in the 1990s in Europe; they had to get organics out. Organic waste is a huge portion: Half of all waste can be compostable.”

Yet, residents resisted, displeased with the use of a kitchen container to separate foodwaste. “There’s a misconception about having more odor and rodent problems, even though the same material is being put out,” Wagner says. “Even green-minded people can be resistant.” She relates the tale of “PTA moms” in New York City who implemented a composting program at the school, but wouldn’t do it at home, out of fear of rats.

To increase participation and ease concerns, they came up with the bag. The bags breathe, allowing heat and moisture to evaporate. That makes them less smelly, Wagner says. There is also less moisture, less weight, and less mold production. The compostable bag creates an aerobic environment.

Some communities, like Toronto, ON, permit plastic bags in order to achieve a high capture rate and high participation, but using them means they have to screen out residue and contamination. “There’s still a stigma against plastic,” Wagner points out, citing it as one explanation for low participation at dog parks in Ithaca, NY, where attempts to divert dog waste from landfills by providing plastic bags for pickup are only minimally successful.

It’s also difficult to operate a compost facility in areas with low landfill fees. “It costs $10 per ton in Ohio,” Jepsen says. “They need political incentives.”

Conversely, on the east and west coasts, where $200-per-ton tipping fees are common, composting is an economic savings, even when the cost of an additional truck for pickup of wet materials is added in. For regions with low tipping fees, the costs of composting aren’t feasible. “An extra truck, separate bins, sample compostable bags, extra pickup days…it doesn’t always make sense,” Wagner says.

Some commercial accounts-namely, restaurants-require daily pickup. For residential accounts, different municipalities are trying various approaches, such as rotating weeks for trash and compostable pickup or using split-body trucks. Admitting that “split-body trucks have mixed success,” Wagner mentions dropoff programs for areas not so dense.

Customer feedback on every program is “across the board,” Wagner says. How to get people to participate is the question. It’s the reason Wagner and Jepsen, representing BioBag and Novamont, work as consultants to cities. “San Francisco was the first city in the US to implement a program,” Wagner says. “Princeton is starting from scratch.” Princeton, NJ, uses a subscription program ($65 a year for weekly green service) but provides a free cart.

Whatever particular program is most effective for each community, the EPA is working to promote more integrated solid waste management practices in answer to soaring waste management costs, diminishing landfill space, and the escalating need for more environmentally responsible practices. 
About the Author

Lori Lovely

Winner of several Society of Professional Journalists awards, Lori Lovely writes about topics related to waste management and technology.

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