June 19, 2013 | General

Anaerobic Digest

BioCycle June 2013, Vol. 54, No. 6, p. 15

Eureka, California: Permitting Toolkit For Food Waste Digesters

The Humboldt Waste Management Authority (HWMA) is a Joint Powers Authority comprised of five municipalities and Humboldt County. The HWMA has been steadily progressing through the stages of developing a stand-alone food waste digester (capacity to be determined). When it came to permitting the digester at the site selected (in the city of Eureka, directly adjacent to its wastewater treatment plant), Juliette Bohn, Project Manager at HWMA, applied for and received U.S. EPA Region 9 grant funds to hire consultants to prepare a California Environmental Quality Act (CEQA) Initial Study. The project site evaluated in this study “proved to be an interesting permitting test case as it is located in the California Coastal Zone, is adjacent to the Humboldt Bay, contains wetlands, has historic native use, and is in close proximity to a coastal recreational trail,” explains Bohn. This combination resulted in the involvement of several different regulatory agencies with unique requirements for project development.
“Pursuit of the initial permitting helped to further the HWMA Regional Organic Waste Digester project,” adds Bohn. “Development of the Project Description and impact analysis allowed all regulatory agencies to comment on the concept of the project at the selected site.” HWMA received no written objections to either the Project Description or the full CEQA Initial Study, therefore it certified and adopted the Mitigated Negative Declaration and Mitigation Monitoring and Reporting Program in April 2011.
Completing this permitting milestone provided the HWMA Board with the confidence to take the next key permitting and project steps that included a geotechnical analysis to assess the soil structure at the site, preparation of a Wetland Mitigation Monitoring and Reporting Plan, preparation of a waste characterization study to quantify the food waste in the member agencies’ waste stream, and use the resultant information to develop a Request for Proposals for the design and installation of the food waste digester. The design is not only crucial for the next phase of project development, but is also needed to pursue the remaining permits.
As part of its EPA grant, Bohn wrote “Permitting Toolkit for Food Waste Anaerobic Digesters,” based on HWMA’s experience with the initial permitting steps and the CEQA environmental review process. The toolkit includes a timeline of the key permitting steps taken, an overview of the current regulatory environment, a list of potential impacts and mitigation measures, and a description of the lessons learned during this process. As for siting, Bohn has learned a number of lessons. “In the ideal world, choose a site that has as minimal overlapping regulatory jurisdictions as possible,” she writes. “And look for industrial-zoned sites with existing impacts.” Download toolkit, ad/hwma-permitting-toolkit.pdf.

Sheboygan, Wisconsin: Net Zero Energy Wastewater Treatment

In 2010, the Sheboygan Regional Wastewater Treatment Facility (WTF) was one of the most energy efficient treatment facilities in Wisconsin. Despite this, the city wanted to do better, initiating its most ambitious and successful energy production and energy recovery project yet, enabling the facility to regularly produce more energy than it requires and achieve Net Zero Energy status. Two key elements to achieve this status were anaerobic digestion improvements to increase effective digestion capacity and biogas production, and 400kW of additional microturbine capacity to convert the large quantity of biogas released to heat and electricity. The city chose energy efficient linear motion mixers (designed to provide homogeneous mixing by creating a turbulent liquid-core of micro and macro eddy currents) to increase biogas production.
Previously, biogas from the three primary digesters passed through the secondary digester to get to the distribution system. This arrangement had become a major bottleneck, impeding the beneficial use of the biogas, and was modified so that each of the four digesters connected independently to a common header for distribution to utilization equipment. The Capstone microturbines include paralleling switchgear that synchronizes the output with the electric utility. The power output is adjusted to match the utility power (sine waves) so they are in sync, allowing the microturbines to “parallel” with the utility power grid to supplement the plant’s power usage and export power to the utility grid when the generated power exceeds the plant power requirements. This capacity enabled the WTF to regularly produce more electrical energy than it requires, exporting excess renewable electricity to the utility grid. In recognition of this Net Zero Energy achievement, the Sheboygan WTF received the 2013 Grand Award from the American Council of Engineering Companies of Wisconsin. “This project is the culmination of concerted efforts to achieve net zero energy with biogas-derived electricity,” said awards judge Rick Niederstadt. “This is a monumental achievement.” Unison Solutions, Inc. and Energenecs were part of the team supplying the biogas conditioning skids and Capstone turbines for the project.

Sacramento, California: Energy Commission 2013-2014 Investment Plan Good For Green Fuels

The California Energy Commission (CEC) unanimously adopted the 2013-2014 Investment Plan Update to support the development and use of green vehicles and alternative fuels, including biomethane from conditioned and compressed anaerobic digester biogas. The update sets funding priorities for use of about $100 million in annual state funds under the CEC’s Alternative and Renewable Fuels and Vehicle Technology (ARFVT) program, created by Assembly Bill 118 (Air Quality Improvement Program). “This investment plan provides a solid foundation for the continued transformation of California’s transportation sector, “ said CEC Chair Robert Weisenmiller. Funding priorities through the ARFVT program support fuel and vehicle development to help attain the state’s climate change policies. Renewable fuels include biomethane and diesel substitutes, such as cellulosic ethanol derived from woody materials and biodiesel from waste grease. Currently California’s transportation sector accounts for nearly 40 percent of the state’s greenhouse gas emissions.

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