The SlurryCarb® facility commissioned in June in Rialto, Calif., is designed to process 245,000 Mg (270,000 ton) of biosolids from five Southern California municipalities — Orange County Sanitation District; the Sanitation Districts of Los Angeles County (LACSD); and the cities of Riverside, San Bernardino, and Rialto. The expected output is 54,000 Mg (60,000 ton) of renewable fuel, called E-fuel, that is expected to generate 823,000 million kJ/yr (780,000 million Btu/yr). Based on average U.S. household consumption, this is enough energy to power 8000 homes.
Independent evaluation by Environmental Resources Management (Annapolis, Md.) concluded that the use of E-fuel would reduce annual greenhouse gas emissions by more than 73,000 Mg (80,000 ton).
The Rialto facility is one of several new installations designed with sustainability in mind.
“The biosolids market is currently in the early phases of repositioning itself to the new world of global warming, carbon credits, green energy, and sustainability,” said Peter Brady, president of Alpine Technology Inc. (Austin, Texas) and co-chair of the Water Environment Federation (Alexandria, Va.) Residuals and Biosolids Committee. The “rule of thumb,” he said, is to “follow full-scale site performance data over a period of time and several projects.”
Some pioneers are testing and evaluating these new technologies as part of their environmental ethic.
Biosolids to E-fuel
“SlurryCarb uses heat and pressure to carbonize the organic matter and rupture the cell membranes to release bound water,” said Brian Dooley, director of marketing at EnerTech Environmental Inc. (Atlanta). “The reacted slurry gives up its water much more easily, meaning that the water can be removed mechanically [with a centrifuge] instead of being boiled off. This results in significant energy savings compared to conventional biosolids drying.”
The Rialto facility is in what customer Steve Maguin, chief engineer and general manager of LACSD, describes as “full-scale testing.” He said the process is competitive with conventional disposal methods, and he thinks it has “great potential.” It gets water out of biosolids “without using a lot of energy,” he said. “We think [it’s] going to be very cost-effective.”
Mike Sullivan, monitoring section head at LACSD and former biosolids manager, explained that solids go into the reactor at about 26% and come out the same, “but the viscosity changes to a substance like motor oil,” he said.
Sullivan noted that, in part, LACSD’s movement in this direction is to “transition away from options that are disappearing.”
Mitsubishi Cement (Henderson, Nev.) is Rialto’s first E-fuel customer. “They want to take all that we can give them,” Dooley said.
On the end-user side, E-fuel compares to a low-grade coal, without the costs of digging up coal and transporting it. Net emissions from burning the fuel are “essentially zero,” according to Dooley. He added that minimal to no modification is needed to convert existing customer equipment designed for coal.
On the environmental side, odor is minimal, Dooley said. Bacteria and pathogens are removed (E-fuel is a combustible fuel, but it’s rated “Exceptional Class A” biosolids), so air quality concerns are minimized.
California Statewide Communities Development Authority tax-exempt bonds financed the $160 million facility. The state required an environmental impact report, air and solid waste handling permits, and a water quality management plan.
Clients pay a biosolids fee ranging from about $77 to $88/Mg ($70 to $80/ton). “There are a lot of variables that go into cost,” Dooley said. They include type of biosolids, percent solids, and criteria imposed by the municipality’s infrastructure, including whether heat is available and logistical factors, such as the availability of onsite storage bins.
It takes about 640 Mg/d (700 ton/d) to produce 150 Mg (170 ton) of E-fuel.
While the total E-fuel to be produced is “a drop in the bucket” in terms of replacing coal entirely, it’s a flexible biosolids management solution, “and it works on a range of organic waste,” Dooley said.
EnerTech is addressing carbonization gas generation by adding additional piping to collect gas and is tracking down pinhole leaks in the system’s heat exchanger, with the goal of making the facility fully operational by year’s end.
Also in June, Clean Water Services, which serves a population of 500,000 in the Portland, Ore., area, opened a struvite recovery facility at its Durham wastewater treatment facility through a partnership with Ostara Nutrient Recovery Technologies Inc. (Vancouver, British Columbia).
Clean Water and Ostara share revenue from commercial sale of the fertilizer byproduct, which is marketed as Crystal Green®.
“Cities and municipalities throughout the U.S. are increasingly faced with stricter regulations to stop the release of phosphorus,” said Robert F. Kennedy Jr., Ostara board member and partner, and senior advisor to VantagePoint Venture Partners. “Until now, there has been no viable method to economically remove this phosphorus (or struvite) from the wastewater stream.”
Ostara estimates that about 200 facilities in North America and another 200 throughout the world are candidates. “That number is certainly growing as nutrient limits are developed,” said Ahren Britton, Ostara chief technology officer. He noted that 1360 kg/d (3000 lb/d) of struvite is needed to make an installation viable.
The solution is designed to be cost-effective and generate revenue. For every 450 kg (1000 lb) of struvite, 55 kg (120 lb) of phosphorus is produced. Durham produces about 4000 kg/d (9000 lb/d) of struvite, removes 90% of phosphorus, and will produce 450 Mg (500 ton) of Crystal Green (which is 12% phosphorus) annually. Since startup in May, Durham already has produced 70 Mg (80 ton) of product.
Roy Rogers, Clean Water’s Washington County (Ore.) commissioner for more than 30 years, said the Durham facility has difficult maintenance problems, and Ostara offered reduced electrical and chemical usage and showed a revenue stream. “We looked at it purely from a business perspective,” he said.
The product is a slow-release, environmentally friendly fertilizer, the only one on the market with 5-28-0 +10% magnesium. It’s already being used at Oregon State University (Corvallis) and has opportunities in the container nursery industry, turf and golf courses, and specialty agriculture.
When liquid leaves Durham’s centrifuge, it is sent through the Ostara reactor, and magnesium (ferric chloride or alum) is added to precipitate phosphorus out. Liquids move on to treatment.
Durham has treated about 380,000 L/d (100,000 gal/d) of centrate with phosphate recovery at 80%, Britton said.
“After the system has run for a while, we should see a 15% to 30% reduction in the phosphorus concentration of the biosolids,” said Mark Poling, waste-
water treatment department director at Clean Water Services. “We are currently seeing a 20% reduction in the primary effluent phosphorus. The ammonia loading on the plant is reduced by about 5% to 10%.”
For the end user, the product is recycled and pure. “It’s an inert mineral,” Britton said, and once it’s washed and dried, “it smells like rocks,” he added.
According to Ostara, more than 90 million Mg (100 million ton) of phosphorus is mined and processed into fertilizer. Recycling phosphorus that naturally accumulates in wastewater treatment plants could reduce that amount.
The installation cost Clean Water $2.5 million, but this amount is expected to be recovered in 5 years through Crystal Green revenues and operational cost savings of approximately $500,000 per year, according to the district.
Clean Water Services also has a patent pending for its “Waste Activated Sludge Stripping To Remove Internal Phosphorus” technology that incorporates Ostara’s reactor.
“We believe there will be a market for municipalities to use the technology,” said Nate Cullen, senior engineer at Clean Water. “Removing the magnesium before it reaches the anaerobic digesters will greatly reduce the deleterious downstream struvite formation while increasing the amount of fertilizer produced ... and [it] will also reduce operating costs.”
“The biggest challenge was to take business risks without it being risky,” Cullen said. “Ostara’s initial proposal was a ‘treatment fee’ model, where they would finance, construct, and operate the facility, and we would pay for every pound of phosphorus removed. With this approach, Ostara would take all the risk. Although appealing, we determined this approach did not make good economic sense for us.”
The district proposed facility ownership and operation, where Ostara would buy the fertilizer produced. Clean Water must produce fertilizer for the payback. “But it is a risk that we have control over; the more fertilizer we produce, the shorter the payback will be,” Cullen said.
In Ostara’s fee-based model, municipalities pay a fee for the duration of a 10- to 15-year contract. Installation costs between $1.5 million and $10 million, depending on plant size, Britton said.
According to Brady, emerging alternative technologies and public–private partnerships are not changing the picture of biosolids management for municipalities in any “new or significant way” but can be useful because they “question old assumptions and draw attention to what is of emerging importance.”
Brady recommends that interested municipalities “get a consultant with a staff of experienced experts and look at their recent projects” and consider that “proven technologies can be configured for a new situation.”
The marketplace is nevertheless hungry for resources that will meet carbon footprint reduction goals, so the use of emerging technologies is likely to expand and evolve.
“We’re going to be reusing biosolids in one way or another,” Maguin concluded.
“Wastewater is not something that’s being discarded anymore,” Rogers said. “It’s a valuable resource.”