Tag: anaerobic digestion

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On-Site Analytical Laboratories to Monitor Process Stability Of Anaerobic Digestion Systems

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Abstract

The anaerobic digestion of complex materials is a highly dynamic, multi-step process, where physicochemical and biochemical reactions take place in sequential and parallel ways.  The stability of the process depends on a delicate balance between the formation and consumption of products. When the concentration of a particular substance reaches the homeostatic equilibrium of certain organism or group of organisms, such balanced is disrupted, and the process becomes upset. If measures to correct the source of the problem are not taken, substrate stabilization and biogas production will progressively decrease, and eventually stop. Recovery of a digester can take several weeks to months, during which, energy generation and waste treatment are not possible, resulting in increased operational costs for the facility. To detect process perturbations and prevent major digester upsets, periodic monitoring is essential.

In this study, analytical laboratories were installed on selected on-farm anaerobic digestion systems in New York State, to periodically monitor key process parameters and to evaluate performance and stability of the operations.  Preliminary results showed that analytical labs were critical to detect process upsets efficiently, particularly in co-digestion systems, where loading rates and influent characteristics are usually variable. The laboratory is rather optional in manure-only operations, where the influent consists of a steady and predictable waste.

Authors

Rodrigo Labatut, Cornell University ral32@cornell.edu   

Curt Gooch, Cornell University

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Converting Onion Waste into Energy as a Co-digestant with Dairy Waste

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Lab scale anaerobic digesters constructed from PVC pipe used to evaluate co-digestion of manure with onion waste

Ninety liter (90 L) anaerobic digesters (anaerobic filters) were constructed from PVC pipe.  The digesters were filled with lava rock.  A thermocouple is placed in the center of each digester to be used in controlling temperature.  Each digester is controlled by a datalogger by reading temperature and turning on or off pumps to circulate water around digester maintaining temperature at 35 oC.  Biogas is collected in a tipping bucket and recorded on datalogger.

Abstract

Consumers demand high quality fruits and vegetables. As a result, packing sheds around the country cull or remove bad fruits and vegetables prior to packing then in boxes for shipment to stores. The culling process produces millions of pounds of waste fruits and vegetables annually. This culled fruit or vegetable then has to be disposed of in some form or fashion. Therefore, a project was designed to investigate the feasibility of using culled onions in conjunction with dairy waste to produce methane gas. The experiment used 90 liter downflow anaerobic filters to process a 50/50 mix of onion juice and dairy waste. Results from this study indicate the co-digestion of culled onions and dairy waste provides a good way to dispose of the waste onions while at the same time producing a renewable energy that can potentially be used in the packing shed where the onions are separated. The 50/50 blend of onion waste and dairy waste has consistently returned an average of 15 liters of biogas (70-75% methane) per 3 liters of mixed waste entering the digesters with a cleaning efficiency over 85%.

Why Look at Food Waste for Co-Digestion with Manure?

Culled onions or any fruit and vegetable has to be disposed.  Some of these are fed to animals, but some are thrown on fields and potentially tilled into the soil.  However, if they are piled and allowed to decay in place the liquid produced during the decaying process can have a high chemical oxygen demand (COD).  If this liquid is allowed to run into waterbodies they could be polluted or if allowed to infiltrate could be transferred to a waterbody through underground movement.  Therefore, this project investigated the characteristic of liquid produced from decaying onions as well as the feasibility of using waste onions along with dairy waste to produce methane gas in anaerobic digesters.  If feasible, the culled onions (or other fruits and vegetables) could be used as a source of energy verses a disposal issue.

What Did We Do?

The experiment had two parts.  The first part placed whole onions in a steel tank on a 2 foot bed of sand where the onions could naturally decay.  The liquid along with any rainwater was collected in portions and tested for its pH and Chemical Oxygen Demand.  Additionally, waste onions were juiced and mixed with dairy wastewater in a 50/50 mixture and used as feedstock for an anerobic filter digester.  Temperature was controlled in the mesophilic range and biogas was measured.

What Have We Learned?

As expected, the decaying onions release a liquid that over time increases the COD profile of the liquid draining from the decaying pile.  It is expected that if onions were continually piled on the same spot, the COD and pH of the liquid would equalized at a COD value measured to be approximately 80 g/L and the pH would drop to approximately 3.5 (these numbers based on some previous studies and bench scale observations).  The data also suggest that, and as would be expected, onions decay faster in the summer months as opposed to winter months in Georgia.  It was also found that a 50/50 mix of onion waste and dairy wastewater fed to a pilot scale mesophilic anaerobic filter fed at 3 liters per day and a retention time of 7 days will produce approximately 15 liters of biogas daily with a methane composition of 70-75%.  The treatment level of the influent was also found to average greater than 85%.

The Chemical Oxygen Demand (COD) of liquid collected from the bottom of a tank full of decaying onions increases over time. Likewise, the pH of the liquid decreases. If these onions are disposed of in a wet area or area adjacent to a waterbody, the stre

The Chemical Oxygen Demand (COD) of liquid collected from the bottom of a tank full of decaying onions increases over time.  Likewise, the pH of the liquid decreases.  If these onions are disposed of in a wet area or area adjacent to a waterbody, the stream would be affected by the high COD and low pH liquid.
Biogas production from the mixed 50/50 onion/dairy waste fed at a rate of 3 liters per day. The methane composition of the biogas ranged from 70-75%. Treatment efficiencies of the waste, based on COD reduction, averaged greater than 85% (over 20 g L-1 i

Biogas production from the mixed 50/50 onion/dairy waste fed at a rate of 3 liters per day.  The methane composition of the biogas ranged from 70-75%.  Treatment efficiencies of the waste, based on COD reduction, averaged greater than 85% (over 20 g L-1 influent to less than 2 gL-1 in effluent).

Future Plans

Future plans will be continue the investigation of using waste onions (and other fruit and vegetables) as a feedstock for anaerobic digesters.  This feedstock, which is very available in onion growing regions seasonally, liquid from the onions can be stored over time (as observed in other research project) to provide a year round feedstock for the production of methane gas.  As we now know that the decaying onions release a liquid that has a high COD, using the onions for production of energy may reduce potential problems with water pollution as well as provide growers with additional income streams.  Plans will be to continue this work and look at optimizing the feed rate and mix ratios.

Authors

Gary Hawkins, University of Georgia, ghawkins@uga.edu

Additional Information

A few articles have been written about the project, research papers will be written in the near future.

Acknowledgements

The Vidalia Onion Research Committee and the USDA-AFRI Speciality Crops Initative

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Coupling Dairy Manure Anaerobic Digesters with Commercial Greenhouses – An assessment of Technical and Economic Feasibility

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Abstract

Despite all of the positive environmental benefits of anaerobic digestion, the economics are not sufficient for widespread adoption by US farmers when selling surplus power to the grid.  Often farms are only paid the wholesale price (2 to 3 cents/kWh) for electricity, making it difficult to justify generating it in the first place.  In addition, typically in the Northeast, approximately 40% of the energy from a digester goes unused (excess heat).  Therefore, promising value-added technology/business partnerships need to be evaluated and demonstrated, such as partnering anaerobic digestion with commercial greenhouses. 

Greenhouses are an ideal end user of the waste heat and surplus electricity produced by a digester.  In the Northeast and other similar climates, heat and electricity represent a major expense for greenhouse growers.  Greenhouses can make use of excess heat to provide the necessary growing conditions for year-round production and excess electricity can be used to run supplemental lighting to keep production constant year-round.

To facilitate the adoption of digester/greenhouse unions, we are developing a comprehensive computer model of both the energy output of farm-based digesters, the energy requirements of the associated farm, and the energy required by greenhouses, in terms of timing and magnitude.  We will use existing and project-developed data collected from five Northeast digesters and three greenhouse operations to aid in developing and validating the model.  The model will be complex enough to handle varying biomass inputs and required outputs, and the economics of operation.  We will use the model to run several real-world “what ifs” and use the outputs for making recommendations to existing anaerobic digesters considering coupling with greenhouses. System economics are also going to be included.

Authors

Curt Gooch, Cornell PRO-DAIRY cag26@cornell.edu

Tim Shelford, Cornell PRO-DAIRY

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Online Bioenergy Training for Extension Educators

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Purpose

The online Bioenergy Training Center provides educational training resources for Extension educators focused not only on the technical feasibility of bioenergy generation, but also on approaches and processes that assist communities in understanding the comprehensive implications of bio-based alternative energy. The intended outcome of the courses is to bring viable bioenergy projects into communities by providing Extension educators with tools and knowledge they can use to make this happen.

What Did We Do?

Developed three peer-reviewed, research-based online modular courses. Content was developed by experts from across the North Central Region. Included in one of the modules is a bioenergy and renewable energy community assessment toolkit.
Screen shot of the front page of the Bioenergy Training web site.

What Have We Learned?

The curriculum went live on the web in February 2013. We have not received any feedback on it to date. However, based on the reviews of individuals who used the bioenergy and renewable energy community assessment toolkit in 2012, it does a very good job of helping developers and communities objectively assess renewable energy projects.

Future Plans

Use the curriculum as a foundation for distance learning courses targeting other audiences.

Authors

M. Charles Gould, Extension Educator, Michigan State University, gouldm@msu.edu

Over 50 individuals participated in some aspect of curriculum development.

Additional Information

The Bioenergy Training Center web site is being revamped. It will be posted here at a later date.

Acknowledgements

Curriculum materials and training programs of ‘The Bioenergy Training Center’ were made possible through a grant from the National Water Resources Program, National Institute of Food and Agriculture, U.S. Department of Agriculture. NIFA/USDA Agreement No. WISN-2007-03790. Project Title: “Energy Independence, Bioenergy Generation and Environmental Sustainability: The Role of a 21st Century Engaged University”.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Feasible Small-Scale Anaerobic Digestion – Case Study of EUCOlino Digestion System.

 

* Presentation slides are available at the bottom of the page.

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Abstract

While large-scale farms have typically been the focus of anaerobic digestion systems in the U.S., an emerging need has been identified to serve smaller farms with between 50 and 500 head of cattle. Implementing such a small, standardized, all-in-one system for these small farm applications has been developed. Small-scale digesters open the playing field for on-farm sustainability and waste management.

Unloading the first biodigester unit.

This presentation on small-scale digestion would discuss the inputs, processing, function, and outputs of BIOFerm™ Energy Systems’ small agitated plug flow digester (EUCOlino). This plug-and-play digester system has the ability to operate on dairy manure, bedding material, food waste, or other organic feedstocks with a combined total solids content of 15-20%. A case study would be presented that describes the site components needed, the feedstock amount and energy production, as well as biogas end use. Additional details would include farm logistics, potential sources of funding, installation, operation, and overall impact of the project.

This type of presentation would fill an information gap BIOFerm™ has discovered among dairy farmers who believe anaerobic digestion isn’t feasible on a smaller scale. It would provide farmers who attend with an understanding of the technology, how it could work on their specific farm and hopefully reveal to them what their “waste is worth”.

Why Study Small-Scale Anaerobic Digestion

To inform and educate attendees about small-scale anaerobic digestion surrounding the installation and feasibility of the containerized, paddle-mixed plug flow EUCOlino system on a small dairy farm <150 head.

Biodigester unit being installed at Allen Farms.

What Did We Do?

Steps taken to assist in financing the digestion system include receiving grants from the State Energy Office and Wisconsin Focus on Energy. Digester installation includes components such as feed hopper, two fermenter containers, motors, combined heat and power unit, electrical services, etc…

What Have We Learned?

Challenges associated with small project implementation regarding coordination, interconnection, and utility arrangements.

Future Plans

Finalize commissioning phases and optimize operation.

Authors

Amber Blythe, Application Engineer, BIOFerm™ Energy Systems blya@biofermenergy.com

Steven Sell, Biologist/Application Engineer, BIOFerm™ Energy Systems

Gabriella Huerta, Marketing Specialist, BIOFerm™ Energy Systems

Additional Information

Readers interested in this topic can visit www.biofermenergy.com and for more information on our plants, services and project updates please visit us on our website at www.biofermenergy.com. You will also see frequent updates from us in industry magazines (BioCycle, REW Magazine, Waste Age). BIOFerm will also be present at every major industry conference or tradeshow including the Waste Expo, Waste-to-Worth and BioCycle– stop by our booth and speak with one of our highly trained engineers for further information.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Feasibility of Installation of Anaerobic Digesters at Cattle Operations and Demonstration of a Decision Support Tool

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Abstract

An online decision support tool for determining feasibility of anaerobic digestion has been developed (http://www.erams.info/AD_feasibility/). This decision support tool is specifically targeted to cattle operations in the arid west and provides general information on anaerobic digestion (AD), recommendations on the technical and economic feasibility of AD based on producer provided information on management practices, recommendations on appropriate AD technology based on user defined criteria for the system, guidance on technology provider selection, and required maintenance for operation of an AD system. The goal of the tool is to enable and empower producers to make informed decisions about AD based on unbiased information rather than relying on the biased information often provided by technology providers. In this workshop, the drivers for technical and economic feasibility for on farm AD installation will be discussed and the online decision support tool will be demonstrated.

Why Look at Anaerobic Digestion for Cattle Operations?

Anaerobic digestion is a waste management tool with many advantages, including generation of energy for on-site use. However, careful consideration must be given regarding technical and economic feasibility for installation on cattle operations. A web-based decision tool has been developed to provide technical and economic guidance to producers on feasibility of on-farm anaerobic digestion (http://www.eramsinfo.com/erams_beta/AD_feasibility/).

Home Page of Web-based Decision Support Tool

What Did We Do?

Based on commonalities found from feasibility studies conducted throughout the state of Colorado, a web-based decision tool has been developed to provide technical and economic guidance to producers on feasibility of on-farm anaerobic digestion (http://www.eramsinfo.com/erams_beta/AD_feasibility/)

What Have We Learned?

For use of conventional anaerobic digestion technology at dairy facilities, manure should be collected on concrete by scraping or flushing. Anaerobic digestion of manure collected on dry lots is not feasible with conventional technology.  Economics are favorable when on-site energy use is high and the energy produced by the digester is primarily used on-site.

Future Plans

We will continue to develop and improve the existing web-based tool. We are also working on developing an anaerobic digestion technology suitable for dry lot collected manure.

Authors

Sybil Sharvelle, Assitant Professor, Colorado State University, Department of Civil and Environmental Engineering, sybil.sharvelle@colostate.edu

Jeffrey Lasker, Research Assistant, Colorado State University

Lucas Loetscher, Research Assistant, Colorado Sate University

Additional Information

http://www.eramsinfo.com/erams_beta/AD_feasibility/

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Next Generation Technology Swine Waste-to-Energy Project

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Abstract

* Presentation slides are available at the bottom of the page.

The Loyd Ray Farms project is the first swine waste project in the State of North Carolina to generate and transfer renewable energy credits (RECs) to a public utility.  Utilizing an anaerobic digester as primary treatment, this waste treatment system is designed to meet the Environmental Performance Standards set forth by NC law for new and expanded swine facilities through the use of nitrification/denitrification and further treatment. The system implemented at this farm utilizes anaerobic digester technology to turn raw animal waste into biogas.  The biogas is used to fuel a microturbine, generating electricity to power the environmental treatment system, and about half of the farm. Related: Manure value & economics

The farm is a finishing swine operation that houses approximately 9,000 pigs near Yadkinville, NC.  The concept for this approach was conceived by the team in 2006, followed by economic and performance modeling, permitting, and construction of the commercial-scale system.  The project was commissioned on May 27, 2011.  Funding for construction was provided by Duke Energy and Duke University, with support from USDA-NRCS and the NC Division of Soil and Water Conservation.  Google provides operational funding support in exchange for a portion of the carbon offsets created.

Loyd Ray Farms is the only innovative Swine waste system in North Carolina that generates Renewable Energy Credits for an electric utility,  which generates enough power for  the treatment system and has enough surplus electricity to power about half of the farm.  Cavanaugh collaborated in this study with Duke University, Duke Energy,  and Google with funding from NC Soil & Water Conservation and USDA/Natural Resources Conservation Service.

Forefront: Tatjana Vujic of Duke University views the meter readings

The project began as a conversation about greenhouse gas emissions, sources for renewable energy, and sustaining the state’s swine industry among Duke Energy, Duke University, Google, and Cavanaugh.  That conversation led to a project that is getting attention around the world, for its successes in combining strategies to address the concerns for generating renewable energy from agricultural sources, sustaining agriculture, and addressing farming’s relationship to climate change.

The system’s goals: generating about 500 megawatt-hours of electricity annually, reducing greenhouse gas emissions equivalent to 5,000 tons of carbon dioxide annually, reducing ammonia and odor emissions from the farm, and improving the quality of treated wastewater on the farm.”

Is Manure to Energy Important?

We will discuss the successes and challenges in partnered efforts by farmers, electric utilities, and other stakeholders in the marrying of renewable energy generation with enhanced environmental treatment and green house gas emissions reduction, including the economics of such effort.

What Did We Do?

Waste generated by the animals is flushed into an anaerobic digester where bacteria consume the waste and respire energy-rich biogas.  The biogas fuels a microturbine that generates electricity, and excess gas is flared.  After digestion, the liquid waste is further treated to achieve the Environmental performance Standards set forth by North Carolina for Innovative Swine Waste Treatment Systems.

The process by which the stakeholders came together in a partnership, the technologies and approaches selected, and the successes/challenges that can be gleaned for advancing future projects.  The Loyd Ray Farms project is the first Swine Waste-to-Energy project in the State of North Carolina to place RECs on the North Carolina Utilities Commission REC Tracking System, and is the first swine farm in North Carolina to transfer RECs to Duke Energy.  Coupling techniques to improve the environmental treatment system employed at the farm, the Loyd Ray Farm project is also the first ‘Innovative Swine Waste Treatment System’ permitted that utilizes an anaerobic digester as a primary form of waste treatment.

Presenters

William G. “Gus” Simmons, Jr., P.E. Cavanaugh & Associates, P.A., gus.simmons@cavanaughsolutions.com

Gus Simmons, lead designer, M. Steve Cavanaugh, Jr., and Marvin Cavanaugh, Sr. during the commissioning of the system.  Cavanaugh developed the concept for Duke University in an effort to create a cost-effective solution that converts swine waste into renewable energy while achieveing a superior level of waste treatment and a reduction in the carbon footprint created by the conventional waste management system.

Gus Simmons, P.E., is the Director of Engineering at Cavanaugh & Associates, a consulting firm specializing in stewardship through innovation.  An NC State University graduate with a BS in Biological & Agricultural Engineering, Gus  has worked for a major agricultural producer where he was Director of Environmental Affairs and Engineering Services, managing engineering and construction for facilities in the US and Europe.  Gus has designed, permitted, and managed over 5,000 acres of wastewater irrigation in NC, and thousand of acres of wastewater irrigation in the Western US. He has assisted many municipalities and private entitites with the development and implementation of reclaimed water systems and reuse irrigation systems, and has actively participated in alternative wastewater management strategies for the NC Pork Industry.  His recent sucessess include the engineering design of an anaerobic digester for animal waste to energy project in Yadkinville, NC which has gained world-wide recognition for its successes in generating RECs and greenhouse gas credits.

Additional Information

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Anaerobic Digester Workforce Training Curriculum Development

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Purpose

The Cornell University PRO-DAIRY Anaerobic Digester Workforce Development Project is a project funded by the New York State Energy Research and Development Authority, aimed at developing and delivering high quality educational programs targeted to a range of workforces within the dairy farm-based anaerobic digestion (AD) sector of the clean energy field.  One of the barriers to growth of the AD industry in New York State, as identified by current AD operators, is the lack of a trained, skilled workforce to service and maintain different aspects related to the AD and biogas systems.  These courses are aimed at developing a workforce to support this need, and to eliminate this barrier to growth.

What Did We Do?

Six technical short-courses were developed, intending to provide educational training to persons who are involved in the planning and implementation of dairy farm-based anaerobic digestion systems and to those currently or who would soon be managing an operating system.  The short-courses developed are:

 

· Introduction to Farm-based Anaerobic Digestion

· Technical Feasibility of On-farm Anaerobic Digestion

· Economic Feasibility of On-farm Anaerobic Digestion and Economic Assessment Model Instruction Guide

· Practical Considerations and Implementation of Anaerobic Digestion System from Planning and Design to Construction

· Technician’s Start-Up and Operation

· Biogas Clean-up and Utilization Systems Selection, Operation and Maintenance

 

What Have We Learned?

We have learned that it is difficult to deliver technical training for jobs and a workforce that do not yet exist.  Training was mostly targeted at dairy farms currently or expecting to operate an AD and biogas system, and those that advise these farms.  The authors feel that although participant numbers were usually lower than expected, continuing to offer these courses will eventually eliminate a technical expertise barrier, helping aid growth in the field.

Future Plans

Although funding for this project has ceased, efforts will continue to serve technical schools that have interested parties that may be suitable candidates to enter the field and participate in the training programs.  As demand exists, courses will be offered to farms and their advisers across the State.

Authors

Jennifer Pronto, Research Assistant, Cornell University, jlp67@cornell.edu

Additional Information

http://www.manuremanagement.cornell.edu/Pages/Funded%20Projects/AD_Workforce_Development_Project.html

Acknowledgements

The New York State Energy Research and Development Authority was the funding organization for this project.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Potential Air Quality Impacts of Anaerobic Digestion Of Dairy Manure

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Abstract

Anaerobic digestion (AD) of livestock manure is better known for the economic return derived from biogas for energy rather than for its, inherent, environmental benefits. The effect of AD of dairy manure on the emissions of odor, ammonia (NH3), and greenhouse gases (GHG) including: carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), during manure storage and also in subsequent land applications will be presented.  Air samples were collected in 10-L Tedlar bags, at pertinent locations within the AD system, and shipped immediately to the lab for odor analyses by a trained odor panel using the “Dynamic Dilution Forced-choice Olfactometer.” Measurements of GHG emissions from both AD and non-AD manure storages were made using a floating chamber and a photoacoustic gas analyzer (INNOVA model 1412).  Emissions of GHG were determined using the standard closed chamber method from field plots applied with AD and non-AD manure. Although odor analyses of collected air samples indicated increased detection threshold (D/T), odor strength (intensity) and unpleasantness (hedonic tone) decreased after AD of manure. Data indicated significantly higher fluxes of GHG from land applied with non-AD manure than from land applied with AD manure. Injection of non-AD manure further increased CH4 flux from applied manure. More than 50% emissions of CO2 and CH4 were observed during the first 3 days after manure was land applied. Emissions of GHG from the anaerobic lagoon holding AD manure, during all four seasons, were significantly lower than from the anaerobic lagoon with non-AD manure. In contrast, the reverse was observed with NH3 emissions suggesting potential increased emissions of NH3 during storage of post AD manure.

Authors

Pius Ndegwa, Washington State University          ndegwa@wsu.edu

H.S. Joo, Biological Systems Engineering, Washington State University, PO Box 646120, Pullman, WA 99164; J.H. Harrison, E. Whitefield, Animal Sciences, Washington State University, 2606 West Pioneer, Puyallup, WA 98371; A.J. Heber, J.Q. Ni, Agricultural & Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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Operation of Internal Combustion Engines on Digas for Electricity Production

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Presentation Summary

The purpose of this research is to review engine performance and technology issues relating to generating electricity from digester gas in reciprocating internal combustion engines. Research performed at the Colorado State University (CSU) Engines & Energy Conversion Laboratory (EECL) and published material from other organizations is utilized.

Digester gas (digas) can be used effectively in internal combustion engines for electricity production to offset operating costs and/or sell to the electric utility. Stationary industrial engines are generally employed for this purpose. Four application areas where systems have been successfully demonstrated are sewage processing plants, animal waste facilities, landfills, and agricultural waste processing systems. Digas is generated through anaerobic digestion, or biomethanization, for all these cases. There are many common engine technical issues within these areas, although the digas generation systems employed in each case are different. In this presentation issues pertinent to running engines on digas are explored. The focus is on animal waste facilities, but the presentation draws upon the other application areas for technical insight related to engine technology. Specific stationary engine types are discussed. High engine efficiency and power density are important to the economic viability of anaerobic digestion systems. Engine operational and design changes to maintain high efficiency and power density for digas fueling are analyzed. Management of engine maintenance problems is also key to economic viability. Corrosive gases contained in digas, such as hydrogen sulfide (H2S), are evaluated.
Figure 1 Methane number measurement of various gaseous fuels.

The term biogas is a broad term encompassing both digas and producer, or wood, gas. These gases are very different in their combustion properties. Producer gas is generated in a gasifier by oxidizing biomass in an oxygen-starved environment. Producer gas contains high concentrations of hydrogen (H2) and carbon monoxide (CO), a small concentration of methane (CH4), and high diluent concentrations (CO2 and N2). In contrast digas is primarily CH4 (50-80%) and CO2 (20-50%). One of the main property differences between digas and producer gas is the methane number, which is indicative of the tendency of the fuel to knock. Figure 1 shows methane number measurements of various gaseous fuels made at the CSU EECL[1]. Note that producer gas (wood gas on plot) has a methane number from 60-70, while digas gas has a methane number of almost 140. Consequently, digas is much less likely to knock than producer gas and can be operated with higher compression ratios and higher power densities. Digas is also more knock resistant than natural gas.
Figure 2 Guascor SFGLD-240, rated at 330 kWe at 1200 rpm on 500-600 Btu/SCF digas.

There are three different types of stationary engines that can be used to generate electricity from digas, which are (1) compression ignition (diesel) engines, (2) spark ignition stoichiometric engines, and (3) spark ignited lean-burn engines. Diesel engines (1) are employed by fumigating the intake air with digas. The amount of diesel used is reduced as more digas is added, resulting in dual fuel operation. Limitations on diesel displacement and the necessity of storing two different fuels are drawbacks of this approach. Spark ignition stoichiometric engines have similar operating characteristics to most automotive engines in the United States. They utilize NSCR, or 3-way, catalysts for emissions reduction that required precise air/fuel ratio control. Lean-burn natural gas engines are more efficient than stoichiometric engines and can achieve low emissions without exhaust aftertreatment. Thus, option (3) is the most desirable; it is the approach typically implemented for digas utilization in most large installations. Figure 2 shows a Guascor SFGLD-240 installation by Martin Machinery.

Lean-burn natural gas engines can be used without modification for digas installations. However, in this case the engines typically are de-rated, require additional maintenance, and suffer from reduced engine life. Some engine manufacturers offer engines specifically designed for digas, which has several advantages. Digas has unique properties that necessitate design changes to natural gas engines to achieve rated power and minimize maintenance costs. To maintain rated power the flow capacity of the fuel system must be increased, since the energy content of digas is approximately 60% that of natural gas. This is due to the high concentration of CO2 diluent[2]. Other operational changes often made are advanced timing due to slower combustion and richer equivalence ratio[3]. To maintain the same NOx level the equivalence ratio is richer because the diluent in the fuel reduces combustion temperatures. Though not typically done, higher compression ratio pistons can be added to take advantage of the higher methane number of digas, which results in improved efficiency. Corrosion resistant materials and improved crankcase ventilation are design changes often made to combat the effects of corrosive contaminants in the fuel.

Digas can contain trace levels of gases other than CH4 and CO2 such as hydrogen, carbon monoxide, nitrogen, oxygen, ammonia (NH3) and H2S. Digas H2S levels from hog and cattle digesters of ~2000-5000 ppm are typical. These levels are above engine manufacturer H2S limits (250-1000 ppm)[4]. H2S must be reduced below the respective engine manufacturer limit if the engine warrantee is to be valid. When sulfur compounds are combined with water, acids are produced in the engine oil. These acids attack the metals in the engine, causing corrosive wear. Scrubbers can be used to reduce H2S in the fuel below manufacturer limits. Two commercially available H2S scrubber technologies are iron oxides and bio-trickling. H2S reacts with the iron oxide to form insoluble iron sulfides. The material can be regenerated with air to produce pure sulfur. Iron sulfides and/or pure sulfur must be disposed of[5]. Bio-trickling involves a filter media that provides an environment for establishment of a bacteria biofilm. The H2S comes in contact with the biofilm, is solubilized, and subsequently oxidized by the microbes. Sulfur and sulfate compounds are formed as by-products and purged with recirculating water. The by-products are collected and disposed of. Bio-trickling requires more expertise to set up, but requires less maintenance long term[6]. 

 

[1] Malenshek M., Olsen D.B., “Methane number testing of alternative gaseous fuels”, Fuel, Volume 88, pp. 650-656, 2009.

[2] John C.Y. Lee, Peter Lau, and Thomas Teo,, “Sustainable Application of Reciprocating Gas Engines Operating on Alternative Fuels”,

Caterpillar Inc. publication, October 2008.

[3] Reinbold, E. and von der Ehe, James, “Development of the Dresser Waukesha 16V150LTD Engine for Bio-Gas Fuels”, ASME Internal Combustion Engine Division 2009 Spring Technical Conference, ICES2009-76079, May 3-6, 2009.

[4] Guascor Power, “Anaerobic Digestion Gas Fuel Specifications – Landfill and Digester Gas”, Product Information IC-G-D-30-003e, Sept 2011.

[5] Steven McKinsey Zicari, “Removal of Hydrogen Sulfide from Biogas Using Cow-Manure Compost”, MS Thesis, Cornell University, 2003.

[6] Personal Communications, 1-10-2013, Marcus Martin, Martin Machinery LLC.

Authors

Daniel Olsen, Colorado State University daniel.olsen@colostate.edu

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

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