August 16, 2011 | General

Anaerobic Digest

BioCycle August 2011, Vol. 52, No. 8, p. 20

Bordentown, New Jersey
If Rutgers EcoComplex Assistant Director David Specca had his way, every landfill capable of capturing methane would have an incubator greenhouse attached. The EcoComplex – which conducts research involving all aspects of landfill gas (LFG) recovery and utilization – is home to a 46,000 square-foot greenhouse (more than an acre) that serves as training ground for start-up businesses. Methane from the nearby Burlington County Landfill is piped underground to the greenhouse to generate heat and power. Future plans include using LFG-based carbon dioxide to enrich the aerial environment for growing plants. Current tenants are: Seaburst Farms (hydroponic basil), EcoWalls (verticle hydroponic gardens), FourSeasons Orchids and Bodhitree Farm (hydroponic heirloom vegetables). “There’s a lot of interest in this type of agriculture,” says Specca, adding that such a model provides the community with jobs, job training and local produce while generating power for the grid as well as the greenhouse and stimulating the local economy.
The greenhouse operation was originally funded with grant money for Rutgers University research. The project also received a $750,000 grant from the New Jersey Department of Environmental Protection and New Jersey Board of Public Utilities to study methane gas capture and use of microturbines for cogeneration of electricity and heat. The LFG drives a 250 kW microturbine. The electricity is split between the grid and the greenhouse and during the cooler months, heat is sent to the greenhouse. “In the winter when we have the lights operating, we can use it all,” says Specca. “In the summer, we only use about 50 kW to keep the exhaust fans running.”
The university takes care of all maintenance and pays the utilities, charging tenants a fixed rate. “Since those are all known costs, they can focus on growing and maintaining their crops and on the marketing end of their businesses,” says Specca. The goal is to have tenants standing on their own two feet within three years but they are allowed to stay as long as five. “That’s three years they have to gather solid information – such as the cost of production, market pricing and demand,” he adds. “That is information they can take to the bank in order to build their own facility.”
Los Angeles, California
The nonprofit Climate Action Reserve (CAR) – a national offsets program working to ensure integrity, transparency and financial value in the U.S. carbon market – recently updated its Organic Waste Digestion Project Protocol (OWD) in order to be more in line with the agency’s Organic Waste Composting Project Protocol (OWC). Adopted June 29, 2011, Version 2.0 of the new OWD includes food-soiled paper waste as an eligible waste stream, updates guidance on acceptance and documentation of source separated grocery store waste streams, improves quantification of avoided landfill emissions, updates waste characterization study guidelines and adjusts the climatic regions for determination of decay rates. “Going forward we are trying to keep OWD and OWC as similar as possible, since they deal with the same waste streams and baseline scenarios,” explains Max DuBuisson, CAR’s Policy Manager.
The reserve has issued CRTs (Climate Reserve Tonnes – 1 CRT is equal to one metric ton of carbon dioxide equivalent (CO2e) emissions reductions) for only one OWD project, the Cottonwood Dairy in Atwater, California. “They were one of our first projects in the reserve, and were originally registered as a livestock project,” says DuBuisson. “We have only had a couple of other OWD projects submitted, and neither has gone through verification yet. It seems to be a pretty difficult project type to get working, but we are optimistic that there will be more activity.” A complete draft of the new protocol is at:
Minneapolis, Minnesota
In the Minneapolis suburb of Shakopee, the New England Fertilizer Company (NEFCO) is in the final stages of building an anaerobic digestion facility at the Metropolitan Council’s Blue Lake Wastewater Treatment Plant. “After a phased start-up this fall, the facility should be fully up and running late this year or early in 2012,” says Tim O’Donnell, spokesman for Metropolitan Council Environmental Services, a regional planning agency serving the Twin Cities. The 11-year old Blue Lake Plant currently sends solids removed from wastewater through a large, natural gas-fueled heat dryer operated by NEFCO. The dryer produces fertilizer pellets that NEFCO applies to nearby farmland. The facility under construction will add an anaerobic digestion step to the process, breaking down organic matter into solids, liquids and gas before the solids go through another dewatering step, then into the heat dryer.
Recovered methane gas will replace at least 70 percent of the natural gas now required to fuel the heat dryer, saving the plant $800,000 to $900,000 annually in energy costs. The process will also reduce the volume and mass of the solids going to the heat dryer by approximately 30 percent. By reducing the load to the heat dryer, the current capacity will be enough to handle increasing wastewater flows to the plant through 2020 and perhaps beyond.
The new $28 million facility includes four 1.5-million-gallon digester tanks and covers; a two-story, 21,000-square-foot digester operations building and a 5,000-square-foot chemical-handling building. Modifications will be made for the heat dryer to utilize methane from the digesters, including equipment to reduce moisture in the methane and to increase its pressure. During periods when methane production exceeds the heat dryer’s needs, excess gas will be used to heat the digester operations building and preheat the solids before they are digested, according to O’Connell. Scrubber water that heats up while controlling odors from the dryer exhaust stack also will be used to preheat the solids.
Sonoma County, California
By mid 2012, the Sonoma County Water Agency plans to be offsetting as much as 30 percent of its energy needs with power produced from chicken manure from area farms by installing an anaerobic digester on agency property. The agency provides water and wastewater services to residents of both Sonoma and Marin counties. “We’re the biggest energy user in our county,” Sonoma County Water Agency Public Information Officer Amy Bolten told attendees at a recent Local Clean Energy Leadership Summit in Washington, D.C. “We decided we wanted to become carbon-free by 2015 and embarked upon a wide portfolio of various renewable energy projects.”
The agency is working with BioStar Systems, the Missouri-based manufacturer of the technology, on what’s been dubbed the Farm to Fuel project. Besides electricity, biogas and heat, the project is expected to generate 130 jobs – 36 of them permanent – while managing the waste of more than 2 million chickens. OHR Energy out of Santa Fe Springs, California, is also a partner on the project. American Recovery and Reinvestment Act funds were used to cover 30 percent of construction and installation costs.
The water agency committed to a 20-year power purchase agreement, with OHR and BioStar securing financing for the rest of the project. “A private developer can take care of things we can’t,” Bolten told the Sustainable City Network, which cosponsored the D.C. event presented by Climate Communities. “The combination of their lower reduced capital cost and our ability to bring a really solid, ongoing government revenue stream has produced a really nice, solid project.”
Karachi, Pakistan
Karachi Electric Supply Company (KESC) is planning a $70 million 30MW biogas project and has hired Canadian consultant Highmark Renewables International as the developer. The facility is to be located at the Landhi Cattle Colony. Animal waste will be combined with food waste to produce methane to run the power generators. Initially, the project will consume 600 tons/day of animal waste for an output of 5 MW, eventually processing 3,000 tons/day of manure for an output of 30 MW while generating 400 tons daily of digested solids for reconditioning of depleted soils. The liquid by-product will be applied to agricultural lands as a fertilizer. Highmark shipped a small-scale model of its recently patented Integrated bioMass Utilization System [IMUS] to the site to perform tests under real-world conditions.
Poplars, Staffordshire, United Kingdom
Waste management and recycling specialist Biffa has completed construction of the UK’s largest anaerobic digestion facility solely for treating food waste. The facility is located next to a landfill also operated by Biffa and has the capacity to treat up to 120 metric tons/day of organics. The $38.92 million facility will generate 6 MW of electricity. Feedstocks will include source separated food waste from caterers, food and drink manufacturers, hotels, residential homes, restaurants and supermarkets. Solid and liquid waste will be emptied into a bunker and crushed. After packaging is removed, the organic material will enter into a suspension tank before being pasteurized at 158°F for at least one hour in accordance with UK Animal By-Product Regulations. The waste will enter into one of five digester tanks with the produced methane powering one of three 2 MW gensets.

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