December 22, 2010 | General

Biosolids Composting In The United States – 2010 Update

BioCycle December 2010, Vol. 51, No. 12, p. 35
BioCycle and the North East Biosolids & Residuals Association joined forces to update the list of biosolids composting facilities around the country, identifying a total of 265 projects. Part I
Ned Beecher and Nora Goldstein

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BIOCYCLE first published a survey report on biosolids composting in the United States in 1983. Twenty-seven years ago, the survey identified a total of 61 “full-time” projects, with another 29 expected to begin within a year. The national survey skipped a year and was conducted again in 1985, and then annually through 1998 (see “Biosolids Composting In The United States,” January 1999). By that point, there were 321 projects in the U.S., with 274 operating facilities.
In May of this year, following an inquiry about the number of biosolids composting operations in the U.S. – and not being able to provide an accurate estimate – we decided to conduct the nationwide survey once again. The process took a number of months, but the results are encouraging. BioCycle’s 16th Nationwide Survey, done in collaboration with the North East Biosolids & Residuals Association (NEBRA), identified a total of 265 biosolids composting projects in the United States, with a total of 258 in operation.
Table 1 summarizes the composting methods utilized at the operating biosolids composting facilities. Similar to the 1998 data, the most utilized composting method is aerated static pile (total of 108), followed by windrow composting (83). There are 46 facilities using in-vessel systems, with the remainder employing aerated windrows (windrows built on a floor with aeration trenches), static piles, enclosed aerated static piles (engineered technology using tarps and forced aeration) or vermicomposting. And interestingly, the number of projects in construction is almost identical (6 in 1998 and 5 in 2010).
The primary difference between the 1998 and 2010 data is the number of projects in development (permitting, design/bidding, planning, consideration and pilot). In 1998, BioCycle found a total of 47 projects in development. In 2010, only one project is in planning and there is one pilot. The difference could be attributed in large part to the 12-year gap in data gathering. Conducting a survey annually creates the ability to track projects through the various stages of development. It also provides an opportunity to create a fairly extensive network of contacts within the biosolids composting community – state agencies, municipal governments and consulting engineers, as well as individual project managers.
In 2010, BioCycle and NEBRA focused initially at the state agency level, contacting state biosolids coordinators and asking them to review the list of biosolids composting projects identified in their state in 1998. Most states were able to update the listings, noting facilities still in operation, those no longer operating and any new projects. In almost every case, data was only provided on operating facilities versus projects in development. We also contacted projects directly to confirm and elaborate on the information we had. Assistance also was provided by the U.S. EPA regional biosolids coordinators. Finally, BioCycle queried equipment vendors for project updates. We greatly appreciate everyone’s assistance in providing information. We also welcome feedback on the 2010 data, e.g., facilities missed or ones included that are no longer in operation. Please send updates to Celeste Madtes.

Table 2 provides the state-by-state breakdown of biosolids composting projects in the U.S. The “Guide To Table 2” sidebar explains what the abbreviations stand for as well as provides the full company names of the vendors cited. In the second column of Table 2 (“Status”), when a company name is noted after the term “Operational,” it indicates that this private entity owns and operates the facility or is the operator contracted by the municipal agency. If no company name is listed, the facility is owned and operated by the public agency.
Based on the survey data, we estimate that 7.8 percent of the biosolids generated in the U.S. are composted. This number is based on the actual dry tons/year provided by facilities (477,009 dry tons/year), plus an estimate to account for the facilities not providing tonnage data (82,546 dry tons/year). That total was used as the basis to calculate our national estimate of 562,000 dry tons/year of biosolids composted. A national survey on biosolids end use and disposal, conducted by NEBRA in collaboration with several other entities (see “Biosolids Management In The U.S.,” March 2008), calculated that a total of 7,180,000 dry tons of biosolids were generated in the U.S. in 2004. This national number was used to calculate the BioCycle/NEBRA estimate of 7.8 percent.
In terms of geographic distribution of projects, 44 of the 50 states have biosolids composting projects. The six states with no biosolids composing reported are Alabama, Illinois, Louisiana, Minnesota, Mississippi and Nebraska. (Wisconsin does not have a full-scale project, but a pilot is being conducted by the Appleton Wastewater Treatment Plant in conjunction with the Outagamie County Department of Solid Waste.)
Of the 44 states reporting biosolids composting projects, the number per state breaks down as follows: 26 states have less than 5 projects; 9 states have between 5 and 10 projects; 7 have between 10 and 20 projects. Two states have more than 20 projects – New York (25) and Washington (24).
Aside from a few states, there is no obvious link between the climate and the composting method. Many years ago, the trend was toward windrow composting in the Central and Southwest states, and in-vessel and aerated static piles in the Northeast, Mid-Atlantic and the Pacific Northwest. While climate still plays a role, other factors such as emissions regulations, siting and public perception, advancements in process control and availability of bulking agents may dictate technology decisions. For example, air quality management districts in California have been tightening their rules on VOCs and related emissions from composting facilities over the past decade. As a result, some facilities in climates that typically lend themselves to open-air windrow composting – but located in air districts with severe noncompliance – are utilizing aerated static piles with negative air flow and biofiltration, or enclosed aerated static piles with proprietary aeration and cover technologies.
The most common bulking agents (amendments) used in biosolids composting are wood chips made from yard trimmings or recycled wood waste. Some facilities report using sawdust; several also blend in ash from boiler plants or incinerators.

While gathering information from project managers, we noted consistent enthusiasm about the biosolids compost product. This enthusiasm carried over to facility websites (mostly found by searching on the city or town, then clicking on “wastewater treatment”). Links to “compost” showed detailed instructions on using the compost, described various blends available and their various applications, pricing, hours of operation and photos of the product being used and the results.
While some facilities give their compost away at no charge, most sell the compost and blends at varying prices. For example, the city of Denton, Texas, which composts about 3,200 dry tons/year of biosolids, sells its finished compost in bulk for $25/cubic yard (cy). The price range reported by facilities is from $6 to $30+/cy. The value of biosolids compost is well-recognized in professional markets, commanding fairly high prices, typically in various soil blends and engineered soils. End uses include golf course design, athletic field construction, high-profile landscaping projects and state Departments of Transportation roadside applications (e.g., for vegetation establishment, slope stabilization and plantings).
Having a paying market for the biosolids compost is an expected outcome of most projects today. For example, one fairly new project in Stafford County, Virginia, operated by the Rappahannock Regional Solid Waste Management Board, set out these market establishment goals for its finished product, Rappa-Grow: “To produce a high quality soil amendment made from biosolids and shredded yard waste; To sell 20 five-gallon buckets of finished compost each week for the first year, ultimately diverting 4,000 tons of biosolids and selling up to 1,000 tons of compost annually; and To teach 225 residents how to compost and divert more than 100 tons of organic waste from the landfill each year.”
In one state, a satisfied biosolids compost user (a grower) sent a brief note to the treatment plant commending the nice results experienced in using the city’s biosolids compost.”‘If you told me the compost would help this much I would think you were blowing smoke,” he wrote. “But I guess I can’t think that way. I soil tested the field. The organic matter and the calcium change are awesome!”

Findings of the BioCycle/NEBRA survey of biosolids composting projects in the U.S. indicate that this management method for wastewater treatment solids is holding its own. The total number of projects is slightly lower in 2010 than in 1998, but new facilities are opening and some existing ones are expanding. “Growth in the biosolids composting market continues to be steady,” says Tim O’Neil, president of Engineered Compost Systems in Seattle, Washington. “We continue to see more of a market for biosolids composting in places with reasonable access to amendment to mix with the biosolids. One of the biggest challenges we see is competition from cogeneration – burning wood for energy.”
O’Neil adds that although there is flexibility in the types of bulking agent used for composting with biosolids, the bottom line is the biology of the system. “You can skimp, but only to a certain point,” he says. “We have people who use a relatively low ratio of carbon amendments to biosolids. Having a system that is thermally efficient means that they can hit PFRP (Process to Further Reduce Pathogens), but it doesn’t mean they will have a nice smelling compost. With agitated systems, you can get away with a little less amendment, but with static systems you need the bulking agent for the structure.”
In many parts of the country, land application of Class B biosolids is still a lower cost option than composting. In other places, relatively low landfill tipping fees are drawing in more biosolids, especially when access to land application sites decreases due to land development and/or public opposition to current beneficial use practices.
What is abundantly clear from the conversations we had with composting facility operators is that they are having a positive experience with their facilities, both in terms of their operations and the quality – and widespread popularity – of their end products. Whereas in 1998 there were more stories related to challenges with odor emissions, this survey did not find that being reported. The level of knowledge about how to effectively control odors and troubleshoot other operational challenges (e.g., too wet, too dry) is high, and there are plenty of veteran composters in most states who can assist their colleagues when problems arise. Clearly, the successful track record of facilities operating for decades builds greater confidence in the process and product. Additionally, vendors of composting equipment, who also now have decades of experience under their belts with biosolids composting, are an ongoing source of assistance – as are new products and technologies to improve process control and product quality.
One trend to track is more regionalization of biosolids composting, with larger facilities designed to process biosolids from other treatment plants in their area. Part II in the January 2011 issue will explore that trend in more depth based on interviews with several of these larger projects.

Sharing the experience of the City of Ishpeming, Michigan is not only a positive note to end on, but a sign of what we believe will be happening more over the next few years. Ishpeming needed to find another biosolids management alternative when a long-term agreement with an area landfill came to an end in 2009. “We had a good arrangement for many years with a local landfill,” says Deborah Pellow, Director of Wastewater Treatment for the City of Ishpeming. “We took their leachate and treated it at a reduced cost, and they took our biosolids for free. We were notified in early 2009 that the arrangement would end in 2010, as the landfill would be treating its leachate on site in aerated lagoons.”
City officials had decided before this point that they wanted to switch to a process that yielded a Class A, Exceptional Quality biosolids product. It had focused its evaluations on biosolids drying systems. Ultimately, they decided to go with in-vessel composting, using Engineered Compost System’s stationary vessels (the full story will be included in Part II). From a cost perspective, says Pellow, a rough calculation shows that composting is about half the cost of what the city would have paid in tipping fees to continue disposal at the landfill. “Plus, we have a product that is very reusable and we can sell it,” she exclaims.

Ned Beecher is Executive Director of the Northeast Biosolids & Residuals Association ( Nora Goldstein is Editor of BioCycle.

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