Managing Organics at the MRF

Oct. 28, 2013

Peter Klaich, environmental consultant and a former member of the board of directors for the US Composting Council, says managing organics has taken on increasing importance of late.

“The driving factors are the increased emphasis on sustainability,” says Klaich. “The state regulations in Massachusetts, Vermont, and Connecticut banning institutional commercial and industrial organics from landfills and the onslaught of new technology are always the driver for new market arenas.”

Waste to energy is “coming on like a freight train,” he adds. “There are anaerobic digesters being built all over the country, initially in the most environmentally sensitive areas. The state of Ohio has an excellent infrastructure and they’re diverting the organics throughout the state.”

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Case in point: Quasar Energy Group, based in Ohio. The company recycles energy from organic wastes through anaerobic digestion facilities it designs, constructs, owns and operates. The company has a laboratory and engineering facility at The Ohio State University’s Ohio Agricultural Research and Development Center.

Managing organics goes beyond the facilities to affecting the upstream and downstream processes, Klaich points out.

“Getting the energy and nutrients out of the pre- and post-consumer food residuals is becoming of the utmost importance from an energy generation standpoint and also from a soil augmentation standpoint for the United States,” says Klaich.

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One example that Klaich says is going to “change the fabric of organic diversion in the United States” is at the Blackwell Inn and Conference Center on the Ohio State University campus, which has piloted a new piece of equipment called Grind-to-Energy, which separates organic material from the wastestream.

An InSinkErator unit grinds the food material into small particles before they are taken to the anaerobic digester, operated by Quasar Energy Group. The organic waste is converted to electricity, clean natural gas, and fertilizer.

“It eliminates labor, grinds the food up, doesn’t use up any water, puts it into a polypropylene tank and is then extracted from a vacuum vehicle and taken down 10 minutes from the school to an anaerobic digester,” he says.

Developed by Ohio State’s Facilities Operations and Development Department with the support of the Energy Services and Sustainability office with participation from the Fawcett Center and Faculty Club, the program diverts 20 tons of organic material-or 80% to 85% of the waste it produces-from the landfill a month from the Blackwell Inn.

Additionally, collections have been reduced from 22 times a week for trash and recycling to seven times a week for trash, recycling, and organics. Additionally, the hotel eliminated trash liners in the kitchen.

“Everyone is looking at this area [energy] intensely,” notes Eric Herbert, the CEO of Zero Waste Energy (ZWE). “There are a lot of conferences on it. How that organic fraction is going to be presented to systems and treated depends on where you are in the world.”

To date, much of it has been landfilled.

“The objective seems to be let’s not put it in the landfill, but let’s treat that separately, extract the energy, and reuse the materials,” says Herbert. “I believe that as time goes on, those collection and processing programs will keep evolving. Rather than a lot of source-separated programs and then a huge amount of material going directly to the landfill, we’ll see more complete treatment of all of the waste before it goes to a final disposal location, which will tend to change the dynamics of some source-separated programs or reallocate how those programs are put together.”

Zero Waste Energy (ZWE) is a development company that designs, builds, and operates integrated solid waste facilities throughout North America. ZWE recovers material for recycling and reuse, transforming organic waste into green energy through an anaerobic digestion (AD) dry fermentation process developed in Germany for which ZWE is an exclusive distributor.

“There will always be an organic fraction in the wastestream, and whether it’s source-separated or picked out of the mixed waste MRF, that material is always going to be suitable for our AD systems,” says Herbert.

ZWE’s website points out the common practice in the United States and Canada is using the wet anaerobic digestion process to produce biogas. The systems generally use high-moisture wastestreams such as manure and wastewater treatment plant solids, require preprocessing and a wastestream containing a very low (8% to 10%) solids content.

Anaerobic digestion dry fermentation has been used successfully in European facilities, Herbert says.

ZWE helps customers implement either mixed-waste processing and/or anaerobic digestion of the organic fraction, compost systems and also Refuse Derived Fuel (RDF) and gasification, he adds.

The management of organics is “very much in its infancy,” Herbert notes. “Right now, a lot of places are not doing anything, some are having separate collections and are doing some amount of composting and mulching of that material and some places are now just taking that organic fraction and doing a little more advanced treatment on it, including anaerobic digestion and more advanced composting.”

The objective of ZWE is to manage the organic fraction, whether it’s coming out of a source-separated program or the MSW fraction.

“We also combine it with other compost systems, including an in-vessel composting (IVC) system to make sure we can fully treat it and provide for the sale of the product,” says Herbert.

ZWE’s technology is based on a biological treatment through Kompoferm and Smartferm dry AD. The technologies are designed to keep a high proportion of the waste stream out of the landfill.

“The technologies are the same,” says Herbert. “It’s a dry anaerobic digestion process which takes the material as it is and puts it into a bunker that is sealed. Then we use a combination of anaerobic conditioning and a recirculating liquid that contains the biology to work the material in an anaerobic condition and produce biogas during that period of time.

“That biogas is used in the production of electricity or the most interesting and most applicable use is having it cleaned up and used as CNG as a transportation fuel for operating fleets.”

The system can handle contaminated materials in terms of the organics, “but at the end of the day, it’s a biological treatment of the municipal solid waste, whether it’s source-separated or an organic fraction,” says Herbert.

“We produce biogas off of it in very controlled condition in 21 days and that material is removed and further taken into compost and sold separately. It’s very efficient in terms of its space usage. We’ve been able to do a number of things based upon the technologies and have a very efficient, well-understood, well-documented system.”

In contrast to wet anaerobic digestion, ZWE’s Kompoferm does not require preprocessing and dry solids can be in excess of 50% of the input. It operates on a 21-day batch average cycle time. Digesters are biologically self-heated through the air system and recirculation of the liquid percolate through the material optimizes energy usage.

The liquid percolate contains the necessary biological constituents to negate the use of previously digested material needed to be used to start subsequent batches. Odor is controlled through the injection of oxygen into the digester at the end of the process. The digestate emerging at the end of the process contains a moisture content low enough to be composted through ZWE’s IVC system.

The IVC is a fully enclosed system that accomplishes in fewer than 28 days the natural aerobic breakdown of biodegradable waste designed to create a high-quality compost product, meeting the Process to Further Reduce Pathogens for retail sale or bulk sales.

The 28-day batch average cycle time is designed to be 50% less than traditional aerobic compost processes and includes the active composting process and the aeration and circulation system to expedite pathogen kill and control odors.

As with the digesters, the composters are biologically self-heated through the air system and recirculation of the liquid percolate through the material optimizes energy usage. The IVC system uses a smaller footprint than traditional systems. The material produced at the end of the process contains a low-moisture content and produces premium grade, mature compost.

Smartferm is a semi-mobile, pre-fabricated dry fermentation plant based on Kompoferm technology, a process that diverts more than 99% of organic waste. The system is suited for decentralized production of electricity and heat and is scalable up to 30,000 tons of waste per year.

Fermentation residues are produced for post-treatment, compost, RFD and a landfill fraction. The biogas produced for the generation of electricity and heat yields 75 to 150 kW of electrical and 115 to 200 kW of thermal power. The Smartferm technology is manufactured in the US by a ZWE partner, Dover ESG.

Private/public partnerships are one approach to managing waste.

At the start of this year, ZWE and the Monterey Regional Waste Management District (MRWMD) introduced the company’s first dry anaerobic digester utilizing Smartferm technology in a pilot program to process organic waste to turn into electricity and high-quality compost for agriculture use.

MRWMD manages the solid waste stream from the greater Monterey Peninsula region, an area of approximately 853 square miles and 170,000 residents and visitors. In 1996, the district’s services expanded to include a MRF operation.

Since 1983, the district has operated a landfill-gas-to-energy program converting methane gas to renewable energy. It produces 5 mW of electricity, sufficient to fulfill its own energy needs with enough surplus power sold to the grid to power 4,000 local homes.

During the past four years, the MRWMD has been composting food scraps in response to requests from the local hospitality community’s interest in a more sustainable use for its organic waste.

The Smartferm at the MRWMD is equipped to process up to 5,000 tons per year, creating 100 kW of electricity or up to 3,200 BTU per ton of biogas with 58% to 60% methane content.

The MRWMD district will sell the energy created from the dry AD to the neighboring Monterey Regional Water Pollution Control Agency.

“Zero Waste Energy owns the plant. It’s on their property. They’re supplying the material. We’re charging them based on a per-ton basis. It’s a nice collaborative effort to put this first system in place,” says Herbert.

The driving factors to create the partnership are rooted in what Herbert says are MRWMD’s “very sophisticated joint powers authority and a very knowledgeable general manager, William Merry.”

“We came up with a way to put the project together for them because they really wanted a way to see how anaerobic digestion would work on some of their material streams,” says Herbert. “They have a source-separated collection program amongst a number of haulers in their area where they are collecting restaurant foodwaste, and they also have a program of yardwaste. They wanted to treat that restaurant waste more fully, which is what we’re doing.”

MRWMD is in the process of expanding its recycling facility to do more mixed solid waste processing, Herbert says.

“They wanted to understand more about how that organic fraction might be treated, so we view the project as an opportunity for us to try a number of different of types of materials on the digesters and have it as an experiment, a full-scale demonstration and understanding of how those different wastes would be treated so they can look at a longer-term, bigger system for their organic waste handling.”

With landfill capacity dwindling in the United States, cities are looking for ways to extract more from the waste stream, points out Brian Wells, sales operations and marketing manager for Bulk Handling Systems (BHS), a part owner and investor in ZWE.

“They have made some progress with recyclables, but that still leaves more than 70% of the waste to deal with,” he says.

Wells agrees that strategically managing organics is in its infancy in the US.

“There are communities with separate collections for greenwaste and fewer with dedicated foodwaste programs,” he says. “Given that organics in municipal solid waste can be 30% to 40% of the total wastestream, it’s becoming critical that this gets addressed.”

Compulsory source segregation programs have proved problematic in the US, where people are not as comfortable with being told what to do, whereas in Europe, such practices are more readily embraced, Wells says.

“Cities need to find ways to get participation rates closer to 100%, which means single-bin collection programs,” he adds. “This is now possible with advanced MRF equipment packages, where organic waste can be separated from other materials.

“Once collected, these organics are perfect for dry anaerobic digestion systems where they are biologically processed to produce pipeline-quality natural gas. This gas is then compressed and used to fuel the collection vehicles. It’s a closed loop system. The resulting byproduct can then be composted in more traditional ways, producing agricultural soil amendment products.”

Single-stream recycling depends on availability and participation, and valuable commodities such as recyclables that end up in the wastestream and foodwaste are missed, points out Peter Raschio, BHS marketing coordinator.

“As a result, communities are using their diminishing landfill space to throw away value,” he says, adding that MSW operations are responding by targeting MSW streams, extracting recyclables and organics, and closing the loop on recovery by using organics to create compost and biogas that can fuel their fleets or create electricity.

The BHS family of companies (BHS, NRT, Nihot) has technologies that are applied individually and in integrated systems to process organics. BHS screening technology separates material by size. The BHS Tri-Disc is an in-line disc that is designed to provide consistent sizing and optimal material agitation in a smaller footprint. By the time organic material arrives at the MRF, the majority ends up in 2 inches or smaller, as sized by the Debris Roll Screen.

Optical sorting technology from NRT, including TruSort X-ray, is used to remove items such as glass, plastics, aggregate materials, and metal that can degrade the value of compost.

Nihot’s air separation technology is mostly used on the back end to remove plastic film and other contaminants from compost.

The world’s largest MRF is Republic Services’ Newby Island MRF in San Jose, CA, the Newby Island Resource Recovery Park (NIRRP). The 110 tons-per-hour multi-stream system was designed, manufactured, and installed by Bulk Handling Systems (BHS).

The facility recovers more than 80% of the waste generated from 8,000 commercial sites in San Jose, as well as recyclables from 85,000 households, with the capacity to process 420,000 tons of material annually.

There are four wastestreams in San Jose: organics, commercial dry waste, commercial single-stream, and residential single-stream. The new service includes recycling organic waste in an effort to help the city achieve its sustainability goals, one of which is to become a Zero Waste city.

The NIRRP is capable of sorting thousands of tons of mixed wet and dry materials, features an onsite clean natural gas fueling station and many other sustainable features and serves as a single location for San Jose’s waste, recycling and collection needs. Solar and wind power will be implemented by 2015.

The system consists of four processing lines designed to process 400,000 tons per year, enabling Republic to sort through wet and dry trash, organics, and recyclables in an effort to divert as much material as possible from the landfill.

The result: Yardwaste and foodwaste scraps are transformed into nutrient-rich, certified organic compost used by local businesses, residents, school districts and parks. The Newby Island Organics Facility markets more than 100,000 cubic yards of compost, mulch and wood chips each year.

The NIRRP contains an onsite gas-to-energy facility that provides clean fuel to operate the San Jose/Santa Clara Water Pollution Control Plant. It also generates enough clean energy to power more than 3,000 homes by capturing and converting landfill gas.

San Jose’s website points out that impacts are designated as upstream (preconsumer, resource extraction, production of goods) and downstream (post-consumer, end of life, and waste management).

Envision Waste uses the dirty MRF process, also called mixed waste processing, says Steve Viny, CEO. The company accepts MSW with no prior sorting and source-separated yard waste for free and composts the material.

“Quite a bit of yard waste ends up in the trash,” says Viny. “Many cities have found rather than try to separate it and have a separate haul to bring it to us for free, it’s more cost effective for them to put the yardwaste in the same truck with MSW.”

Once the waste reaches Envision Waste, the organic fraction is mechanically extracted and placed into a Class 1 compost facility along with inorganic matter such as plastic ware and glass. The mixture is bulked with shredded wood and placed into windrows, which are turned with a specially designed windrow turner and monitored for temperature and oxygen. The composting process can take nine to 12 weeks.

“We have a concrete pad that’s sloped to control water run-on and water runoff,” Viny says. “We screen the material and use it for a variety of uses, landfill alternative cover for the most part. The compost has broken glass and it doesn’t pass the inert test to market it to Ma and Pa homeowner.”

Organic materials are getting more attention now than ever before, Viny notes.

“There are many states that prevent source-separated yardwaste from being placed in a landfill,” he says. “In the 1980s, yardwaste was placed in the same truck as household waste and was buried in landfills for disposal. Many states began bans where yardwaste, tree trimmings, leaves, and that type of thing could not be placed at the landfill if they were separated at the source. If they were commingled with household waste, you could dispose of those in the landfill. If they were picked up separately with a separate yardwaste collection route, then they had to be taken to a compost facility.”

There is more attention now being given to foodwaste, Viny says.

“Foodwaste has a high moisture content,” he says. “A tomato, for example, is a lot of water and a little bit of pulp. Foodwaste has more attention on recovering the material not just as compost, but for digesting it, recovering the gasses and using them for energy.”

European technologies have inspired the wet and dry technologies used in the United States for dealing with organics, Viny says.

“Both are used in an anaerobic fashion in a closed vessel to recover the gas to use as energy. The remaining material becomes compost after it’s rendered inert,” he adds.

But it’s been a matter of economics. Until recently, landfill prices were low. But now, “landfill prices have been escalating and by the same token, technology prices have been falling, so we’re getting closer to where the lines intersect,” Viny says.

“It really depends on what location you’re in in the country, the amount of waste generated, what the generation rates would be, what the landfill prices would be, and what the energy costs are,” he points out. “In an area with a scarcity of landfill space and high tip fees and also an area with high energy fees, those would typically be where organics management would make the most sense.”

Those operations with a digester have two ways to feed it, Viny says.

“One way would be to have a separate organics collection,” he says. “The second would be to extract mixed organics from a dirty MRF or a mixed-waste processing facility. Either method would work.”

Viny says he believes some of the driving factors in organics management is that the cost of labor, employee benefits, fuel and waste collection vehicles has outpaced inflation.

“When you look at the escalation of those costs and then look at adding another collection route, you can see where it’s not cost-effective,” he says. “Our company’s position is that it makes more sense than ever before to embrace the dirty MRF setup where you basically receive all of the waste, extract organics, extract recyclable commodities and make a fuel product. By receiving 100% of the wastestream, you’re able to employ mechanical technology and some labor and get very, very high recovery rates. That’s where we’re headed.”

Another method is multiple collection routes.

“You could have a collection route for rubbish, a collection route for recyclables, a collection route for yardwaste and a collection route for foodwaste,” Viny says. “Personally, we think that running four collection routes in four trucks around the same neighborhood doesn’t make a lot of sense.”

As for the future prospects for organics management, Viny believes there’s a public misconception.

“People believe recyclables coming from a mixed-waste processing plant are somehow of a lower quality than they would be from a MRF,” he says. “That’s clearly not the case. I also think some people believe source separation is going to lead to higher and better results than mixed-waste processing.”

The traditional MRF from the 1980s entailed a multibin truck going throughout neighborhoods collecting separated waste, including newspapers, cardboard, tin cans, aluminum cans, glass, and plastics by grade. They did not have compaction and were inefficient, Viny says.

The next generation was the two-stream MRF, where all of the beverage containers were combined together and all of the fiber was combined together, and through mechanical or hand-sorting it would be separated into single commodities.

“The most current iteration is the commingled MRF, where you take all of your recyclables together and use a series of disk screens to separate out the limp objects, fiber from the rigid objects, and then mechanically separate the beverage containers and they grind up fiber.”

The technology for single-stream MRFs is “about as advanced as it’s going to get,” Viny says. “There will be some advances on individual pieces of equipment, like the infrared, but magnets, eddy currents, conveyor belts-those things are pretty well established.”

Viny says there’s a fallacy that single-stream MRF require multiple collections.

“You have to have a separate collection for rubbish, for recyclables, a tertiary collection for yardwaste, and if you want to add foodwaste, it’s a fourth,” he says. “What we think is going to happen is the cost of those four collections is so prohibitive that communities will start to look at dirty MRFs only from the standpoint of minimizing the collection routing.

“There’s a huge cost, and those costs were being subsidized. Once the technology is there to combine it all, Americans are going to want the highest amount of volume reduction and the most independency from the landfill at the lowest cost. The only way you can do that is to minimize the volume.”

Many of the MSW MRF projects with which Van Dyk Recycling Solutions is working focus on organics being mixed in with the MSW, notes Brian Schellati, the company’s director of business development.

In the past, the company would be designing systems that would screen out the 2- or 3-inch-minus fines in the material, which would have most of the wet organic material such as foodwaste and yardwaste mixed in.

“In the last couple of years, we haven’t been asked to separate out the food- and yardwaste from that 2- or 3-inch minus fines,” Schellati says. “In a lot of our more recent designs and projects, we do have a lot of further processing specific to those 2- or 3-inch fines material.”

As such, that has added equipment downstream of the fines screen, whether it’s a trammel or some type of horizontal screen, he points out.

Some of the new equipment Van Dyk Recycling Solutions is using in addition to the traditional magnet separation and eddy current is Titech sensor-based sorting, which serves as an X-ray sensor to inject inerts from the fine material, says Schellati.

“You’re left with two fractions,” he points out. “You positively inject the inert material-which is glass, stones, and anything inert-and the other fraction is the fairly clean organic material, which still has some contamination. Nothing is perfect, but it removes 80 to 90% of the contamination.”

Van Dyk Recycling Solutions’ projects have been executed in three different ways.

“Some people are mixing it back in with the drier carbon-based material and using that as a fuel for gasification-type projects, so they actually put the wet organics back in with the dry organics and use it as a fuel or it’s being used in either anaerobic digestion or composting,” says Schellati.

One company, the Z-Best Composting Facility in Santa Clara County, CA, composts the three-inch minus material it receives from an MSW MRF and cleans it up with the Titech.

Recology, a California company that offers resource recovery, is focused on screening out the 2- or 3-inch minus fines to be used in an anaerobic digestion process, using a screen from Van Dyk Recycling Solutions, Schellati points out.

Source separation is a favored practice in some places throughout North America. Case in point: the Kent Solid Waste Commission in New Brunswick in Canada operates a wet/dry source separation program in an effort to reduce the amount of waste that goes to the landfill.

The program requires residents to separate wet waste and dry waste. Wet waste-yard and food scraps-is disposed of in transparent green plastic bags and dry waste-plastic, cans, glass, paper, cardboard, and metal-in blue transparent plastic bags.

The bags are picked up and hauled to the transfer station in Bouctouche and then sent to the Westmorland-Albert Solid Waste Corp.

There, the program has been in place since 1999. The program is now available to more than 100,000 households.

Once the waste arrives at the site, it is weighed and directed to the appropriate area. All waste originating from wet/dry communities is sent to the wet/dry plants for processing.

Dry waste is received on the dry plant tipping floor, loaded onto a conveyor, and sent through the presort station. Bulky items and non-transparent bags are removed from the waste stream. The remaining blue bags are passed through a mechanical bag opener. Large pieces of cardboard are also recovered at the presort station.

After the bags have been opened, the waste passes through the first sorting station, where employees manually sort out large objects, including cardboard, bulky items, and reject materials. Cardboard is directed to a recycling bin; bulky items and reject material are stored for delivery to the landfill cell. The waste moves onto a fine screen to remove small debris and is transported to the second sorting station, where cardboard, plastic film, glass, sneakers, coffee cups, and cell phones are manually recovered.

The waste is sent through the material separator after the second sorting station, which divides it into a flat stream composed mostly of paper products and a round stream that includes mostly containers and plastics.

Flats are directed to the third sorting station, where plastics or other contaminants are removed. Rounds are directed to the fourth sorting station, where milk cartons, mixed plastics, clear plastics, PET, and all redeemable containers, including nonferrous metals, are extracted. A magnetic separator removes all ferrous materials from the remaining waste. Reject materials from the third and fourth sorting stations are directed to trailers for disposal in the landfill cell.

Wet waste is diverted to the wet plant tipping floor, loaded onto a conveyor and sent through a bag opener. The waste is introduced to a rotating trommel screen. Materials larger than 70 mm are retained by the screen and rejected to landfill.

Organic material falls through and passes under a magnet to remove ferrous metals. It is then shredded, mixed with bulking agents such as wood shavings, and directed to one of eight silos for primary composting.

The decomposing material is computer-controlled for air, moisture, and temperature levels and is regularly turned by machinery, which pushes the material a few meters each day until it reaches the end of the silo.

By that time, it has been 90% composted and is discharged to the refining system where foreign materials are removed from the finished compost before it is directed to a maturing pad outside the wet plant. The total process to usable compost takes six to eight months.

The compost has been used onsite during cell closure projects and is occasionally used as daily cover on the landfill face. Recyclable materials are sold to various markets for the fabrication on new products.

Mixed paper is recycled to produce the linerboard. Cardboard is recycled to produce linerboard and medium cardboard in corrugated cardboard boxes. Stretch film and filler plastic are recycled to produce plastic lumber. Newsprint can be recycled to produce drink trays, egg cartons, fruit trays, fruit cartons, fast food trays, newsprint, paper liner for gyprock, cat box litter, and insulation.

No. 2 natural plastic can be recycled to produce No. 2 natural plastic, and aluminum cans are recycled to produce new aluminum cans. The majority or commingled plastic is used in the carpet or plastic lumber industries.

After all traces of wax have been removed from milk cartons, they are recycled into high-end writing paper. PETT plastics are recycled for the clothing and carpet industry. Sneakers are shipped to Nike’s Recycling Center in Wilsonville, OR, and recycled into athletic surfaces such as equestrian flooring, playground surfaces and basketball courts.

Sierra International is actively involved in numerous projects installing waste-to-energy facilities utilizing processes that produce ethanol, biodiesel and electricity from MSW.

“The strong and growing trend to handle MSW is moving toward Refuse Derived Fuel (RDF),” says Richard Harris, sales director for the recycling and solid waste division of Sierra International Machinery.

Harris recently toured the largest landfill in Europe, located in Rome, Italy.

“All commercial and municipal waste is delivered to a totally automated transfer station. The waste is processed automatically,” he says. “Approximately 40% of the wastestream is organic and is removed early in the process and composted. All metals and inert material is removed and recycled. The balance of the trash is directed into a waste gasification process where electricity is generated. The only residue remaining is granulated minerals.”
About the Author

Carol Brzozowski

Carol Brzozowski specializes in topics related to resource management and technology.

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