Anaerobic Digest

BioCycle May 2016, Vol. 57, No. 4, p. 15

Camden, New Jersey: Biosolids Digester Upgrades

Anaergia Inc. announced it has entered into an agreement with the Camden County Municipal Utilities Authority (CCMUA) to design and supply equipment for new anaerobic digesters and to design, build and operate a 3.8 megawatt (MW) cogeneration system at CCMUA’s Delaware No. 1 Water Pollution Control Facility (WPCF). The CCMUA serves Camden County, which is 226 square miles in area, with a population of about 500,000; 37 municipalities are in the County. The new equipment will also enable the facility to receive and process postconsumer fats, oils and grease and similar wastes. Equipment to be supplied by Anergia includes its Omnivore™ high solids AD technology incorporating high efficiency mechanical mixers and thickeners, a biogas conditioning system and the 3.8 MW combined heat and power (CHP) system. Under the agreement, the heat and electricity generated will be utilized within the WPCF, and Anaergia will operate and maintain the biogas conditioning and CHP systems for a period of 20 years. “The system will both reduce our biosolids treatment and disposal cost, and provide the Delaware No. 1 Facility with renewable energy to significantly reduce the amount of electricity obtained from the grid,” notes Andrew Kricun, Executive Director and Chief Engineer of CCMUA.

Washington, D.C.: EPA Releases Updated Version Of Warm Model

The U.S. Environmental Protection Agency (EPA) released an updated version (Version 14) of its Waste Reduction Model (WARM), which contains a new material management pathway and revisions to existing numbers and methodology. The majority of the updates in WARM Version 14 involve the addition of the anaerobic digestion materials management pathway. EPA added energy and emissions for anaerobic digestion of organic materials, including food waste, yard trimmings, and mixed organics. These emission factors include energy and emissions associated with transporting materials, operating the digester, avoided utility emissions from biogas combustion, avoided fertilizer application and fugitive emissions and soil carbon storage resulting from application of digestate to agricultural soils.

The anaerobic digestion pathway in WARM includes options for the user to model either a wet or dry AD system. WARM also allows the user to model application of digestate to agricultural soils with and without curing. EPA revised the method for calculating energy and emissions from transport of materials to landfills, combustors, composting facilities, and anaerobic digesters. Each pathway uses a consistent source for transportation impacts per mile and ton of waste transport.

EPA made regular updates to various factors in the model using current data sources. The latest 2014 statistics on the carbon content of fuels, landfill methane generation distribution (by type of landfill), and landfill gas recovery and flaring rates have been incorporated from EPA’s Inventory of U.S. Greenhouse Gas (GHG) Emissions and Sinks: 1990-2014. The non-biogenic carbon content of mixed municipal solid waste was updated using EPA’s annual waste disposal data. Various aspects of the U.S. average electricity mix were updated based on the U.S. Department of Energy’s Energy Information Administration’s 2015 Monthly Energy Review while state electricity grid emission factors were updated based on the 2015 update to the Emissions and Generation Resource Integrated Database. EPA updated material properties for biodegradable materials used in modeling anaerobic digestion and landfilling based on recent papers and research; properties include carbon content, carbon storage factors, and methane yield. These updates resulted in changes to the majority of emission factors in WARM.

London, England: ADBA Unveils Cost Competitiveness Task Force

The Anaerobic Digestion and Bioresources Association (ADBA), the United Kingdom (UK) trade association for the biogas industry, has unveiled its Competitiveness Task Force to establish the means to reduce the cost of producing energy generated from anaerobic digestion. According to ADBA, the AD industry outside of the wastewater sector has grown by over 600 percent in the past five years. The association appealed to academic researchers to focus on delivering major improvements that would result in putting the cost of AD on par with the cost of energy from nuclear power. The call came at ADBA’s two-day Research & Innovation Forum 2016 in early April. “Falling incentives and unworkable funding caps hinder renewable technologies’ efforts to scale and improve their cost competitiveness,” explains ADBA’s Chief Executive, Charlotte Morton. “With ever-limited support from government, therefore, the AD industry is seizing the initiative by challenging the expertise of the UK’s world class researchers to help find innovations which will revolutionize performance even more, such as new sources of input, improvements in operational performance and more valuable outputs, to reduce the overall cost of production.”

The Competitiveness Task Force aims to reduce the cost of producing its energy by at least five per cent each year between now and 2020, adds Morton. Five key elements will be instrumental to reduce “levelized costs” to £100/MWh by 2020 (US $142.47/MWh), notes the ADBA: Additional investment in research to hone, adapt and upgrade AD technology to improve efficiency; Government action to implement segregated food waste collections to unlock valuable new feedstock; Recognition of value of digestates; Increased public and business awareness of AD to drive up recycling rates and secure additional investment; and Policy certainty that ensures further growth and investment.

Boardman, Oregon: USDA Awards Loan Guarantee To AD Project

The U.S. Department of Agriculture (USDA) Rural Development announced plans to support an anaerobic digestion project under development by Novus Energy LLC in Boardman, with an $11 million loan guarantee awarded under its Biorefinery, Renewable Chemical, and Biobased Product Manufacturing Assistance Program. This program assists in development, construction and retrofitting of new and emerging technologies for advanced biofuels, renewable chemicals, and biobased product manufacturing by providing loan guarantees for up to $250 million. Novus is working with an Oregon lender, Old West Federal Credit Union, to finance the project. USDA anticipates finalizing loan terms with Novus and Old West by summer. The total cost for the plant is expected to be $20.2 million.

Novus is expected to use residuals from onion and potato processing plants, dairy manure, seasonal plant by-products and other waste supplied by local growers and processors as the primary feedstock. Daily, the plant is expected to generate 3.8 million cubic feet of renewable natural gas, 350 gallons of liquid fertilizer, and 11.2 tons of soil amendment.

Minnetonka, Minnesota: Natureworks Launches Biogas To Lactic Acid Lab

NatureWorks LLC, a bioplastics company, has teamed with Calysta Energy™ to open an 8,300 square foot, $1 million laboratory dedicated to researching commercially viable methods to convert the methane in biogas to lactic acid, a building block of bioplastic materials, such as the company’s Ingeo™ lactides and biopolymers. The methane to lactic acid research project began in 2013 as a joint effort between NatureWorks and Calysta to develop a fermentation biocatalyst. In 2014, laboratory-scale fermentation of lactic acid from methane utilizing a new biocatalyst was proven, and the U.S. Department of Energy awarded $2.5 million to the project. The opening of the new laboratory in 2016 at NatureWorks headquarters marks another step in the journey from proof of concept to commercialization.

“A commercially viable methane to lactic acid conversion technology would be revolutionary,” notes Bill Suehr, NatureWorks Chief Operating Officer. “It diversifies NatureWorks away from the current reliance on agricultural feedstocks, and with methane as feedstock, it could structurally lower the cost of producing Ingeo. It is exciting to envision a future where greenhouse gas is transformed into Ingeo-based compostable food serviceware, personal care items such as wipes and diapers, durable products such as computer cases and toys, films for wrapping fresh produce, filament for 3D printers, deli packaging, and more.”

Beijing, China: ARG Reduction In Digested Swine Manure

Swine farms and their adjacent farmlands are potential hot spots for antibiotic-resistant genes (ARGs). Researchers with the Chinese Academy of Science investigated the on-site occurrence of ARGs distributed in the process of anaerobic digestion (AD) followed by land application of swine digestate. Two typical swine farms, in southern and northern China respectively, with AD along with land application of digestate, were explored to learn about ARG distributions. The researchers report in a scientific paper, “Distribution of antibiotic resistance genes (ARGs) in anaerobic digestion and land application of swine wastewater,” published recently in Environmental Pollution (Volume 213) that ARGs were highly abundant in the raw swine wastewater. AD effectively reduced the number of all detected ARGs (0.21–1.34 log [logarithmic] removal value), but the relative abundance with different resistance mechanisms showed distinctive variation trends. A log removal value (LRV) is a measure of the ability of a treatment process to remove pathogenic microorganisms. An LRV of 1 is equivalent to 90 percent removal of a target pathogen; an LRV of 2 is equivalent to 99 percent removal and an LRV of 3 is equivalent to 99.9 removal and so on.

The reduction efficiency of ARGs was improved by stable operational temperature and longer solids retention times (SRT) in the digester. ARGs in soil characterized the impact from the irrigation of the digested effluent. The total quantity of ARGs in soil fell by 1.66 LRV during idle periods in winter compared to the application period of summer in the northern region, whereas the total amount was steady with whole-year application in the southern region. Further research should examine some persistent and elevated ARGs in AD and digestate land application, note the researchers.

Charlotte, North Carolina: Agricultural AD Project Taking Shape

Charlotte (NC)-based electric power holding company Duke Energy recently signed a deal with Carbon Cycle Energy (C2e), a Boulder, Colorado-based developer of anaerobic digestion facilities, to use biogas from a swine manure digester to be located in eastern North Carolina to generate renewable electricity at four power stations. C2e will build and own the facility; under its 15-year contract, C2e will deliver more than 1 million MMBtus of pipeline quality renewable natural gas (RNG) per year, which Duke Energy calculates should yield about 125,000 MW-hours/year of renewable energy — enough to power about 10,000 homes for a year. The RNG will be delivered to the Duke power plants via existing pipelines of Piedmont Natural Gas.

The renewable energy credits (RECs) generated annually will help Duke Energy satisfy state mandates for electricity produced from swine and poultry waste. Under North Carolina’s Renewable Energy Portfolio Standard (REPS), Duke Energy companies must meet specific compliance targets for swine and poultry waste. The utility is already buying electricity generated from other facilities in the state.

Petaluma, California: Energy Commission Invests In Biogas Project

The California Energy Commission (CEC) approved a $3 million grant for design, construction and operation of an anaerobic digestion system at the City of Petaluma’s Ellis Water Recycling Facility to produce 150,000 gasoline gallon equivalents (GGE) of renewable natural gas (RNG). The facility will receive about 710,000 gallons/month of high strength liquids from food and beverage processors, which is expected to double current methane production at the plant. Existing acid digester tanks at the plant will be repurposed to receive and blend the high strength waste with wastewater solids. The RNG will be used as a fuel replacement in up to 19 diesel waste hauling trucks, displacing consumption of approximately 21,200 gallons of diesel annually.

The funding is provided under the CEC’s Alternative and Renewable Fuel and Vehicle Technology Program. In addition to the $3 million contribution, the city of Petaluma will provide over $12 million in funding. Also included in the project are a biogas purification unit and a compressed natural gas fueling station. The entire project is expected to reduce greenhouse gas emissions by roughly 3,000 metric tons/year of CO2 equivalents. The treatment plant also will have the ability to recycle processing water for crop irrigation, and use the by-products of the process (liquid fertilizer and solid residues) as an agricultural soil amendment.

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