Bearing fruit

A growing number of states and municipalities are implementing food waste disposal bans and aggressive landfill diversion goals. The rush to be in compliance with these new laws and ambitious goals represents an opportunity for many types of facilities, large and small, that can make use of food scraps. Those uses can range from compost and other soil amendments to fuel and energy, and composters, haulers and material recovery facilities (MRFs) are positioning themselves to get a piece of the pie, so to speak.

An online directory of composters in the U.S. and Canada, www.FindaComposter.com, produced by the Biodegradable Products Institute and BioCycle magazine, lists 264 composters that accept food scraps in one form or another.

“It’s not just about aluminum cans, cardboard and milk jugs anymore,” explains Jeff LeBlanc of We Care Organics. “Now we are getting into the harder stuff,” he adds.

Based in Jordan, N.Y., We Care Organics has been producing compost products since 1999. In addition to its Jordan facility, the company operates composing facilities that accept food waste in Marstons Mills, Mass.; Ann Arbor, Mich.; and Wallingford, Conn. It also supplies feedstock to anaerobic digesters in New York state.

The “harder stuff” as LeBlanc puts it describes food waste pretty well, because in addition to being heavy, wet and odorous, it almost always has contaminants in it.

As a basic guide, We Care Organics does not accept plastics, metals or traditional trash from waste generators. “Anything else compostable we can take,” LeBlanc says. That includes waxy cardboard, which he says is attractive to some customers.
 

Quality improvements

LeBlanc says he has been noticing a decline in contaminant levels in incoming material. “Every load has some percent contamination, but at the end of the day it is becoming cleaner and cleaner waste,” he says. LeBlanc attributes the cleaner loads to better education among waste generators and changes in packaging. “The educational level has ramped up at the supermarkets and generators of the waste. They are a lot more focused on what type of waste is being generated to make sure what is being recycled fits the bill.”

LeBlanc says We Care Organics can handle a small amount of contamination but adds, “The problem is, if you get one plastic bag that comes from a grocery store, and that plastic bag gets chewed up into thousands of pieces, and it is not compostable, you will see it. It takes a while for that material to come out of your process.”

We Care Organics does some hand sorting of materials similar to a MRF, according to LeBlanc, and it keeps improving its process for sorting and screening out contaminants. “Having done this for 15 years, we are way better than we were 10 years ago, let alone five years ago,” he says. “The less contaminants we have in the waste product, the more efficient we can be.”

LeBlanc says composting is more forgiving than anaerobic digestion (AD) when it comes to contamination. “AD contaminants can cause a lot of damage with pumps and hoppers and mechanical issues with your mixing system.”

At We Care Organics, food scraps are mixed with wood chips and sawdust to absorb moisture before going through the composting process. The time and temperature is monitored, and the material is cured to achieve the correct balance of carbon and nitrogen. Once that balance is achieved, the materials is screened. The overs are recycled back through the process, and the finished product is sold as We Care compost. Various land applications, such as schools, golf courses and athletic fields, can use We Care compost.

Leblanc says We Care Organics was accepting food waste before a lot of other facilities began accepting it. His advice to newer operations is to focus on the process, product quality and where the finished product is going.

We Care compost is certified by the U.S. Composting Council’s Seal of Testing Assurance (STA) Program, which LeBlanc says is critical. (see sidebar “Seal of approval”)

“The success of food waste scrap will come back down to how the end product is used,” LeBlanc says. “Facilities that have lasted for the last 20 years have lasted because they have very strong product marketing programs. If you don’t care about that, then it will be a short-lived facility. You have to manage your end product.”
 

Organic growth

When Republic Services opened the Newby Island Resource Recovery Park (NIRRP) in July 2012, its purpose was to help the city of San Jose, Calif., achieve its Green Vision goal of diverting 100 percent of its waste from landfills. By implementing a wet/dry collection program for commercial customers and processing 100 percent of the waste collected, the city is well on its way to achieving its goal.

Businesses place food scraps, soiled paper and cardboard and yard trimmings in the wet bin. Clean cardboard, paper, glass, carpet, plastics, wood and metal, are placed in the dry bin.

By April 2013, the city had increased its commercial recycling rate by 22 percent. By the end of 2013, the program had achieved 72 percent recovery and tripled its commercial recycling rate. More than 205,000 tons of material were collected through the program in 2013. More than 74,000 of those tons, or 36 percent, were organics delivered to Zero Waste Energy Development Co. (ZWEDC) for composting and energy recovery.

NIRRP preprocesses organics collected in the wet bins for ZWEDC’s processes. Carl Mennie, Republic Services division manager at NIRRP, describes the system as a “relatively simple process.” First the material is put through a reducer, a low-speed shredder, which opens up the bags. Next, the material is placed on a debris roll screen to shake the fines material out. The overs go to a sort line where the non-organic material is sorted out. (See the diagram below.) This can include everything from plastic bottles to steel and aluminum cans. “Plastics make up the majority of our contamination,” Mennie says.

ZWEDC will only accept material that contains no more than 30 percent paper or fiber and no more than .25 percent glass by weight per load. It divides its organics streams into four levels based on the percentage of contamination defined as follows:

• Organics Stream One (OS1) – organic material with no more than 5 percent contamination by weight per load;
• Organics Stream Two (OS2) – organic material with greater than 5 percent and no more than 10 percent contamination by weight per load;
• Organics Stream Three (OS3) – organic material with greater than 10 percent and no more than 20 percent contamination by weight per load; and
• Organics Stream Four (OS4) – organic material with more than 20 percent contamination and no more than 30 percent contamination by weight per load.

Mennie says, “Most of the material we deliver out of our material recovery facility is in that lowest grade of under 30 percent but above 20 percent.”

Emily Hanson, ZWEDC director of business development, agrees that of the loads received from NIRRP, “Most of them meet Organics Stream Four.” She adds, “We are working cooperatively and giving them feedback on what needs to be cleaned up. Then they can go back to their routes, do outreach and education and make changes to their processing facility to meet our specifications.”

Click the image above to see the full Newby diagram

NIRRP already has made adjustments to its process. Mennie says NIRRP initially used a bag breaker to process organics, but in December 2012 it put in a reducer and a fines line, which he says “gave us significantly better results.”

ZWEDC also receives loads from organics collection routes, which tend to be of higher quality. “Source-separated loads are generally OS1,” Hanson says.

“Materials accepted for composting are generally more flexible than materials accepted for anaerobic digestion.”
 

Generation energy

ZWEDC opened a dry-fermentation anaerobic digestion facility as part of its operation in November 2013, making it one of the first and largest facilities in the country that is using this technology. The company’s fully enclosed facility includes 16 anaerobic digesters and four in-vessel composting tunnels.

ZWEDC defines materials suited for AD as “organic materials that generate methane when anaerobically digested to create biogas as an approved product without negatively impacting digester performance. Suitable materials do not include one-fourth-inch minus preprocessed organic material, wax-coated fiber, stumps, branches, lumber, fibrous plant trimmings such as palm or yucca or contamination or prohibited materials.”

Organics suited for the dry-fermentation AD process are loaded into tunnels and deprived of oxygen for 21 days to induce biogas production, according to ZWEDC. After the digestion process is complete, the remaining material is moved into in-vessel compost tunnels for five days to facilitate the composting process. Acid scrubbers remove the majority of the ammonia, particulates and compounds.

The biogas extracted from the digestion tunnels are routed to two combined heat and power (CHP) generators to produce electricity and heat with a total generation capacity of 1.6 megawatts. The recovered heat supplies all of the thermal demands of the digesters and compost tunnels in the facility, according to Hanson. Two piping chambers provide process piping, controls and instrumentation to the digesters.

Materials that aren’t suitable for the AD process are either used to make compost or are sold to a cogeneration fuel plant for use as fuel.

With a capacity for 90,000 tons of material, ZWEDC is considered the largest facility of its kind in North America. Other large-scale projects that plan to incorporate food waste and organics recycling into an integrated waste management model are in the pipeline in Montgomery, Ala., and in Grove City, Ohio.

As more and more composters, AD facilities and MRFs start to accept food scraps, it appears that generators of food waste will have outlets for this material that offer alternatives to landfilling.

The author is a managing editor with the Recycling Today Media Group and can be reached at ksmith@gie.net.