Renewable Energy Waste Conversion
Albertville is the first city in the state to convert solid waste into Class A biosolids using renewable biogas. Krebs Engineering designed the national award-winning project.
Municipal Utility Board officials John Wright (left) and Dale Williams (center) with Mark Smith, who led the design project for Krebs Engineering.
Recycling human waste into fertilizer may seem like an indelicate topic for polite society, but it’s an important one nonetheless.
Like most municipalities, the city of Albertville processed sewage sludge and then hauled it to landfills. But starting in 2014, Albertville shifted to a more sustainable, cost-effective method and one that few communities have yet adopted.
Krebs Engineering in Birmingham developed a way for Albertville to control solids hauling and disposal costs by using renewable biogas — methane produced by the fermentation of organic matter — at its wastewater treatment plant.
Krebs Engineering received the American Council of Engineering Companies 2016 Grand Design Award for its “Biosolids Improvements for Energy Recovery” project for the city of Albertville. This national recognition coincides with Krebs Engineering’s 90th anniversary this year.
The employee-owned company has been providing water, wastewater and civil engineering solutions since 1926 and first worked with Albertville in the 1950s at the city’s drinking water treatment plant.
All wastewater — translate that as “sewage” — treatment processes produce biosolids. Most biosolids are digested — meaning they are reduced or stabilized — by using air, heat or lime to decrease odors and control pathogens, those disease-causing organisms such as bacteria, viruses and parasites.
Biosolids treated by using drying technologies are recycled and used as a fertilizer and soil improvement instead of taking up space in already overloaded landfills. The EPA has developed rules for the beneficial reuse, or recycling, of biosolids, which are classified as either the exceptional quality Class A or Class B.
According to Krebs Engineering, the Albertville project, which received a $910,000 energy efficiency grant, is the only facility in Alabama to use renewable biogas to convert costly waste into a useful Class A biosolids product.
Class A must meet certain EPA standards: contain no detectable levels of pathogens, undergo advanced treatment to reduce attracting disease-carrying insects and rodents and have low levels of metals. Krebs Senior Associate Mark Smith says that most wastewater facilities produce Class B biosolids since they require less treatment.
Smith points to several benefits to recycling and reusing Class A and Class B biosolids. They provide nutrient value through nitrogen, phosphorous and trace elements. They help reduce soil erosion and protect water quality. They amend soils and reclaim sites, including mines, and conserve dwindling landfill space.
The production of Class A biosolids by heat drying has advantages lacking in alternative methods, lime stabilization and high temperature digestion. Heat drying reduces the volume of solids to be stored and hauled by about 80-90 percent, compared to high temperature digestion and lime stabilization. Heat drying can utilize biogas or methane that is already being produced as fuel during the digestion process, which provides a sustainable fuel source.
Incinerating biosolids consumes oil or natural gas for power and most of the ash ends up in landfills anyway. Heat drying does not require lime or other chemicals and does not “burn” or combust the biosolids. Minimal space is needed and heat drying allows Albertville to use its existing solids-handling facilities.
Elden Chumley, general manager of the Albertville Municipal Utilities Board, says about 104 dry tons of fertilizer is produced each month in Albertville. Most of that is used on local hay fields and a little goes to landscaping use. Though wood mulch can be added to make compost, Chumley says Albertville is not yet blending its fertilizer.
ABOVE Albertville’s design award-winning wastewater treatment plant converts sewage sludge to reusable materials using renewable biogas for fuel.
Albertville is saving money because of controlled handling and disposal costs, and the fertilizer it produces could someday be a revenue source for the city, says Chumley. That would happen when the new treatment facility is no longer in the experimental stage and is running at full capacity.
Krebs evaluated 20-year life cycle costs to determine that the best direction for Albertville was a biosolids dryer that would produce Class A biosolids. Smith identifies several factors that have made Albertville’s biosolids facility a success.
Key is the city’s ability to control solids handling costs, which were expected to rise indefinitely as available land application became scarcer and hauling costs increased. Albertville also needed to spend an estimated $1 million on new solids handling equipment at its drinking water treatment facility, unless it was able to send these solids to its wastewater facility for treatment and processing.
In addition, the new biosolids drying facility has allowed Albertville to consolidate its wastewater and drinking water solids handling operations at a single facility. And Albertville had the staff needed to operate and maintain the complex equipment and drying process, thus requiring minimal need for outside assistance.
Chumley notes that the area’s many poultry farms, another major source of waste, were also a factor.
Biosolids have been used for fertilizer for decades, including on the White House lawn. Yet despite the benefits there’s concern that using human waste as fertilizer is riskier than using animal, and debate over how much of the toxic compounds are absorbed by plants.
Advocates point out that steps used to process biosolids are designed to kill pathogens. Recycling of biosolids as a fertilizer and soil amendment has been researched extensively by numerous agencies including the EPA.
“In every case it was concluded that this practice, when performed in accordance with federal guidelines and requirements, presents negligible risks to the public and the environment,” Smith says.
Biosolids have yet to catch on in Alabama and nationwide. Lisa McFadden, senior program manager for the nonprofit Water Environment Federation in Alexandria, Virginia, says the barriers are primarily legislative and economic, based on the enormous difficulties that come from having to compete with the established fossil fuel industry.
McFadden believes government initiatives promoting new renewable energy technologies have the greatest potential to help wastewater utilities overcome the economic barriers to energy recovery. She also calls for educational efforts, aimed at regulators, utility managers and other key decision makers.
“In our research about renewable energy technologies, we found that many of the barriers to energy recovery from biosolids are shared with the renewable energy industry at large.”
WEF believes legislative support through reliable financial incentives could turn this around, though for biosolids in particular the barriers can be higher. Current federal and state legislation does not clearly recognize biosolids as a renewable energy source, which McFadden says makes it difficult for biosolids-to-energy projects to benefit from existing state and federal renewable energy incentives.
One of Krebs Engineering’s clients is actively evaluating biosolids treatment alternatives that would enable them to produce Class A biosolids. Another client has expressed an interest in Krebs evaluating Class A biosolids alternatives as part of the planning process over the next one to two years.
Yet most of the company’s clients continue to produce Class B biosolids, which Krebs believes will be the preferred method for the foreseeable future.
Jessica Armstrong and Tyler Brown are freelance contributors to Business Alabama. Armstrong is based in Auburn and Brown in Huntsville.