bioenergy – Livestock and Poultry Environmental Learning Community

Purpose

Deriving the most value from the harvesting of organic wastes, particularly waste produced through farming operations, can be quite challenging. This paper describes an approach to overcome the challenges of realizing the best value from harvested farming wastes through aggregation. Included in this description is an overview of the first swine waste-to-energy project in North Carolina based on aggregation of the value stream rather than aggregation of the feedstock, or manure. Also included in the description are an overview of the challenges encountered, approaches to overcome these challenges, and the solutions developed for this breakthrough approach that will foster further development of successful ventures to maximize the value derived from recycled farming wastes.

What did we do?

Increasingly, our civilization is turning to bioenergy sources as an environmentally-friendly, sustainable alternative to harvesting long-buried fossil fuel sources to supply our energy needs. As the land that farmers have cultivated for years becomes encroached more and more by non-farming land uses, society seeks innovations to address its concerns for our future food needs produced in a manner that addresses environmental concerns associated with modern food production, including nutrient recovery, water conservation and reuse, and controlling odors and emissions from agricultural wastes and manures. Collectively, these innovations have been described as ‘sustainable farming’ approaches.

North Carolina is a significant agricultural producer, and as such, a large producer of agricultural wastes. This state also became the first state in the Southeast to adopt a Renewable Energy Portfolio Standard, and is the only state in the U.S. to require a certain percentage of that renewable energy must be generated from agriculture waste recovery, with specific targets for swine and poultry waste. Naturally, the plentiful resources coupled with a regulatory driver for renewable energy worked together to create attention and efforts toward cost-effective and efficient means of supplying our energy needs through organic waste recovery, or bioenergy approaches.

We are only beginning to see a surge in commercial development for the recovery of additional value stream from the waste, such as through the recovery of nutrients, enzymes, and monetized environmental attributes associated with pollution abatement. While many forward-thinking farmers have learned that their waste is valuable for supplying renewable energy, it has been unfortunately difficult for an individual farmer to implement and manage advanced value recovery systems primarily due to costs of scale. Rather, it seems, success may be easier achieved through the aggregation of these products from several farms and through the collaborative efforts of project developers, product offtakers, and policy. A shining example of such aggregation and collaboration can be observed from the Optima-KV swine waste to pipeline renewable gas project, located in eastern North Carolina in an area of dense swine farm population.

The Optima-KV project combines, or aggregates, the biogas created from the anaerobic digestion of swine waste from five (5) adjacently located farms housing approximately 60,000 finishing pigs. The Optima-KV project includes the construction of an in-ground anaerobic digester at each farm. The resulting biogas is captured from each farm, and routed to an adjacent, centralized biogas upgrading facility, or refinery, where the biogas undergoes purification and cleaning to pipeline quality specifications. The renewable natural gas produced from this system will be sold to an electric utility subject to the requirements of the North Carolina Renewable Energy Portfolio Standards, and will result in reduced emissions from both the receiving electricity generating unit and the farms, reduced emissions of odors from the farms, and reduced fossil fuel consumption for the production of electricity. The upgraded biogas (RNG) will be transmitted to the electricity generating unit through existing natural gas pipeline infrastructure.

What have we learned?

The innovative design, permitting, and financing for the project is very different than a conventional feedstock aggregation approach, and thus much has been learned. To deliver the RNG to the end user, in this case, multiple contracts with multiple utilities were Graphic showing how it works required, which presented challenges of negotiating multiple utility connections and agreements. This learning curve was steepened as, at the time of the inception of Optima KV, the state of North Carolina lacked formal pipeline injection standards, so the final required quality and manner of gas upgrading was established through the development of the project.

The project is currently in the beginning stages of construction, and completion is expected by the end of 2017. Given this schedule, the Optima KV project will provide the first pipeline injection of gas – from any source – in the state of North Carolina (all natural gas presently consumed in the state is sourced from out of state).

Future Plans

North Carolina’s potential for agricultural waste-to-energy projects is enormous, given its vast agricultural resources. Combining the potential from agriculture with the bioenergy potential from wastewater treatment plants and landfills, it is estimated to be third in capacity behind only California and Texas. The unique approach to aggregation of value streams from multiple sources, as exhibited by this project, will open the doors for similar aggregation strategies, including the anaerobic digestion of mixed feedstocks such as food waste, poultry and swine waste, animal mortality, fats, oils and grease and energy crops.

Corresponding author, title, and affiliation

Gus Simmons, P.E., Director of Bioenergy, Cavanaugh & Associates, P.A.

Corresponding author email

gus.simmons@cavanaughsolutions.com

Additional information

http://www.cavanaughsolutions.com/bioenergy/

1-877-557-8923

gus.simmons@cavanaughsolutions.com

https://www.biocycle.net/2016/11/10/anaerobic-digest-67/

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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

March 5, 2019March 20, 2019

Biofuels and Bioproducts from Wet and Gaseous Waste Streams: Challenges and Opportunities

Proceedings Home | W2W Home

Purpose

To provide an initial characterization of the wet and gaseous organic feedstocks available in the continental U.S., and to explore technological possibilities for converting these streams into biofuels and bioproducts.

What did we do?

The Bioenergy Technologies Office (BETO) of the U.S. Department of Energy commissioned an in depth resource assessment by teams at the the National Renewable Energy Lab (NREL) and the Pacific Northwest National Lab (PNNL). Concurrently, BETO conducted a series of workshops, informed by an extended literature review and several rounds of peer review to ascertain the states of technologies for making biofuels and bioproducts from these resources. These efforts resulted in a January 2017 report that is available here:

https://energy.gov/eere/bioenergy/articles/beto-publishes-analysis-biofu…

What have we learned?

Terrestrial feedstocks are currently the largest resource generated for the bioeconomy, estimated at 572 million dry tons for 2017 (Billion Ton 2016), and have traditionally constituted the primary focus of the Bioenergy Technologies Office (BETO). However, the resource assessment conducted by the National Renewable Energy Lab and Pacific Northwest National Lab indicates that wet waste feedstocks (Summarized in Table ES-1) could also make significant contributions to the bioeconomy and domestic energy security goals.

Summary of Annual Wet and Gaseous Feedstock Availability

Table 1. Annual Resource Generation

1 116,090 Btu/gal. This does not account for conversion efficiency.

2 The moisture content of food waste varies seasonally, ranging from 76% in the summer to 72% in the winter.

3 Methane potential. This does not include currently operational landfill digesters (>1,000 billion cubic feet [Bcf] annually) and may double count potential from wastewater residuals, food waste, and animal waste.

4 DDGS = Dried Distillers Grains with Solubles

BCF- Billion cubic feet

When combining the primary waste streams of interest: sludge/biosolids, animal manure, food waste, and fats, oils, and greases, a supplemental 77 million dry tons per year are generated. Of this total, 27 million dry tons is currently being beneficially used (e.g. fertilizer, biodiesel, compost), leaving 50 million dry tons available for conversion to biofuels, bioproducts or biopower. Gaseous waste streams (biogas and associated natural gas) contribute an additional 734 trillion Btu (TBtu), bringing the total energy potential of these feedstocks to over 2.3 quadrillion Btu. Additionally, these streams contain methane, the second most prevalent greenhouse gas, which constituted 12% of net U.S. emissions in 2014 according to the U.S. Environmental Protection Agency’s (EPA) greenhouse gas inventory. Thus, there is significant potential to valorize these energy dense streams while simultaneously reducing harmful emissions.

As illustrated by example in Figure ES-1, wet and gaseous waste streams are widely geographically distributed, frequently in areas of high population density, affording them unique current and emerging market opportunities. The size of publicly owned treatment works, landfills, rendering operations, and grease collectors overlay with the largest population centers nationwide. Therefore, when compared to terrestrial feedstocks, these waste streams are largely aggregated and any derivative biofuels, bioproducts, or biopower are close to end markets.

Figure ES-1. Spatial distribution and influent range of 14,581 US EPA 2012 Clean Water Needs Survey (CWNS) catalogued treatment plants

At the same time, however, this close proximity to populations markets often correlates with more stringent regulatory landscapes for disposal. Therefore, the value proposition presented by these waste streams commonly includes avoiding disposal costs as opposed to an independent biorefinery that requires stand-alone profitability. Aided by these and related factors, public and private entities are actively exploring and deploying novel solutions for waste stream valorization. Potential competition between biofuels, bioproducts, and other beneficial uses will likely be a key element of future markets, and clearly merits further analytical and modeling investigation.

Future Plans

This report concludes that wet and gaseous organic waste streams represent a significant and underutilized set of feedstocks for biofuels and bioproducts. They are available now, in many cases represent a disposal problem that constitutes an avoided cost opportunity, and are unlikely to diminish in volume in the near future. As a result, at least in the short and medium term, they may represent a low-cost set of feedstocks that could help jump start the Bioeconomy of the Future via niche markets. While much modeling, analysis, and technological de-risking remains to be done in order to bring these feedstocks to market at significant scales, the possible contributions to the overall mission of the Bioenergy Technologies Office merit further attention.

Corresponding author, title, and affiliation

Mark Philbrick, Waste-to-Energy Coordinator, Bioenergy Technologies Office, U.S. Department of Energy

Corresponding author email

mark.philbrick@hq.doe.gov

Other authors

see report

Additional information

Future activities are contingent upon Congressional appropriations.

Acknowledgements

see report

March 5, 2019March 20, 2019

Money to Burn: How to Capitalize on BioCNG at Your Wastewater Plant

Purpose

Across the globe, units of government are struggling with the balance of deriving clean energy with economics and environmental protection. This struggle has led to the development of many renewable energy innovations and inventions, such as rapid improvement in the cost and efficiencies of photovoltaic solar (PV) systems and the development of large off-shore wind turbine systems. The challenges imposed on energy utilities associated with managing grid variability leads emphasis on the development of ‘baseload’ alternative energy systems, like bioenergy systems. We should recognize, however, that we have a bounty of organic wastes generated by society each day, and systems that are able to recycle these organic resources into energy are capable of more consistent energy generation, as compared to the intermittency of solar and wind. In this regard, such bioenergy systems hold promise for balancing our energy needs.

What did we do?

Bioenergy systems based on the utilization of organic wastes, such as municipal wastes, food wastes, and crop residues provide the additional benefits of supporting improved pollution prevention and waste treatment systems.

Of the organic wastes available for us in bioenergy systems, one may be directly correlated to the increasing energy needs and clean energy desires of the global population – waste organics associated with municipal wastewater treatment. Municipal wastewater treatment strategies vary by geography, climate, and level of development across our globe. However, in all cases, opportunities exist to utilize these waste as feedstocks for the creation of biogas that may be used to fuel electricity generators, farm implements, and the transportation needs of our population.

****the above writing doesn’t explain the work that was conducted as requested

What have we learned?

Many municipal and industrial wastewater treatment plants (WWTP) across the U.S. already utilize anaerobic digestion as a primary treatment process to reduce sludge or reduce organic loading, expressed as Biochemical Oxygen Demand (BOD), to subsequent aerobic treatment processes. However, most of these facilities presently flare the biogas that is produced from the digestion process. Most often, these managers report the following reason for lack of implementation of energy harvesting. WHAT REASON???

We continue to seek clean, renewable energy sources across the globe to reduce our dependency on fossil fuels for improved air quality and economic stability. While solar, wind, and other renewable energy sources play a vital role in a diversified energy strategy, the development of bioenergy systems that continuously operate in ‘base load’ fashion is very important for grid stability. Additionally, unlike solar and wind, bioenergy systems that convert organic wastes into fuels have opportunities to positively impact transportation fuel needs. The development of systems that harvest biogas from anaerobic digesters employed at municipal wastewater plants can serve to fill a portion of this need, and create improved revenues for the wastewater treatment utility. Often, anaerobic digesters serving municipal wastewater treatment plants are operating well under their optimum capacity, creating opportunities for municipalities to engage in partnerships with private sector waste generators, such as food and beverage processors, restaurants, and farmers.

Many commercial fleets are converting to natural gas fuel to realize the cost savings and participate in programs that reward cleaner air quality through reduced emissions. Each commercial waste truck that is converted to natural gas from diesel has a comparable impact to removing 325 cars from the road. Currently the costs of natural gas-fueled vehicles are slightly higher (10-15%) than conventionally-fueled vehicles. However, as the costs of fossil fuels rise, and more CNG vehicles are manufactured, the costs are likely to become very similar.

****An explanation of the table below would be useful.. You should use this document to outline how you conducted the study and what you found, most of the information contained is introductory in nature.

Table 1.

Future Plans

Unlike fossil fuels, which are finite in quantity, bioenergy and biogas systems convert the organic wastes that are generated each day into fuel; often in only a few days’ time. In this regard, bioenergy systems offer a truly infinite resource for renewable energy, while providing the added benefit of pollution reduction and additional revenues to support existing wastewater treatment infrastructure systems.

Author

Gus Simmons, Director of Bioenergy, Cavanaugh & Associates, P.A. gus.simmons@cavanaughsolutions.com

Additional information

www.cavanaughsolutions.com

1-877-557-8924

Acknowledgements

Clean Water Needs Survey, 2008

Loyd Ray Farms, Yadkinville, NC

Duke University Carbon Offsets Initiative

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

March 5, 2019March 20, 2019

Above the Dirt: A Look into North Carolina’s Clean Energy Future through Waste-carbon Harvesting

Why Study Organic Wastes as Energy Sources?

Compare the Potential: The United States has tremendous organic resources available, such as food waste, crop residues, animal manures, and human waste. Americans need only look out the window of their home or office to see the reasons why – we live in a very ‘green’ country. In most states, we have a temperate climate with ample resources that promotes our ability to inhabit and cultivate; which means we create organic wastes. However, Americans have been slow to realize the huge potential that may be derived from these organic resources in the form of bioenergy. Why have we spent so much time evaluating the energy resources buried deep in our soils, rather than recognizing the opportunity right in front of us, above the dirt?

What did we do?

This presentation provides an overview for establishing infrastructure systems that capture, purify, and transport the biogas that may be derived from these organic resources to create an infinite energy reserve to draw from, creating jobs and bolstering our economy. Potential uses for energy products that may be derived from organic wastes are discussed, as well as the barriers, challenges, and economics of waste to energy systems. The presenter’s home state of North Carolina is examined in more detail, describing and comparing the potential for harnessing the energy value from wastes that lie above the dirt.

The Potential:

To understand the infinite possibilities and advantages of the use of bioenergy nationwide, let’s first explore the possibilities in just one state, North Carolina. According to Census Bureau migration patterns in 2013 across the U.S. showed that North Carolina remains in the top 3 fastest-growing states in the nation. While predominantly an agricultural state, N.C. has an abundance of potential to be derived from organic resources in the form of bioenergy. N.C. places second in the U.S. for the production of pigs and turkeys and it ranks fourth in the production of broiler chickens. This generates an abundance of organic wastes, particularly in animal manures, which as people are beginning to understand, gives our state of North Carolina the potential to be a leader in supplying renewable energy.

Map of permitted hogs

According to sources such as the Environmental Protection Agency (EPA), the U.S. Department of Agriculture (USDA) and the Renewable Energy Laboratory (NREL), the organic waste resources in North Carolina – stemming from municipal waste (solid waste and sewage) and agriculture (animal manures) – are among the richest in the nation. Imagine the Potential: North Carolina can harvest energy value from crop residues, food waste and crops to produce infinitely renewable energy that can also improve air and water quality impacts. Anaerobic digestion is one common approach to harvesting the energy content of these organic wastes and other feedstocks.

Biomass resource of the United States, methane emissions from manure management map

What have we learned?

The development of bioenergy systems is one of the ways in which we can be good stewards of our earthly resources. By reusing the carbon readily at hand above the ground – which is often already creating a negative environmental impact in the form of waste – these bioenergy systems can provide for our fuel and energy needs while simultaneously achieving improvements in environmental quality. There are many ways in which we can accomplish the reuse of carbon through the harvesting of energy value associated with organic wastes. There are over 16,000 permitted municipal WWTP’s in the U.S., and about 10% utilize anaerobic digestion. Coupled with the thousands and thousands of farms, landfills, and biotechnology manufacturing facilities, our ability to develop renewable biogas fuels for transportation and electrification is astounding.

NC "all bioenergy" facilities map (with NG pipelines)

Future Plans

As a country we need to step away from how we have always done things (buying foreign sources of oil, and using fossil fuels, and relying solely on power plants) and be receptive to innovative approaches that improve climate action initiatives and foster stewardship of our earthly resources so that we can do better environmentally and plan so there be enough water, energy and food for the future. These recommendations start on a state to state level, and progress through our country, and across the world. We need to take better care of our environment, and uses our resources to reduce pollution and greenhouse gases, and harvest the energy from our wastewater and agricultural sources that lie above the dirt.

Author

Gus Simmons, P.E., Director of Bioenergy, Cavanaugh & Associates, P.A. gus.simmons@cavanaughsolutions.com

Additional information

www.cavanaughsolutions.com

1-877-557-8924

Acknowledgements

Duke Energy Carbon Offsets Initiative

NREL – www.nrel.gov/gis

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

March 5, 2019July 6, 2020

Life Cycle Greenhouse Gas Emissions of Dairy and Bioenergy Systems

Why Study Greenhouse Gas Emissions from Dairy Systems?

Animal agriculture presents multiple challenges for sustainability and the dairy sector alone contributes 30% of agricultural greenhouse gas (GHG) emissions. Bioenergy systems have been implemented to reduce GHG emissions and contribute to energy independence goals, but the production of bioenergy must be done with caution to avoid the generation of additional emissions during feedstock production and harvesting. This research used life cycle assessment (LCA) techniques to evaluate the integration of dairy and bio-energy systems to address global warming. The first place for integration is the dairy feed preparation level, where potential co-products of the biofuel industry (e.g. dry distillers grains with solubles and soybean meal) can be included in the dairy ration. A lifecycle approach should be considered to evaluate changes in GHG emissions related to the production of these added dairy feeds. This is important because the embedded emissions and energy resources related to upstream processes (e.g. manufacturing of seeds, fertilizers, pesticides, and fuels) and downstream processes (e.g. transportation and harvesting) can result in added greenhouse gases. The second point where dairy and bioenergy systems can be integrated happens at the waste management level, where manure is digested in an anaerobic digestion (AD) system to produce renewable energy. Different cow feeding scenarios, management practices, and anaerobic digestion pathways are modeled to identify practices that minimize GHG emissions at the dairy farm.

Figure 1. Cradle-to-farm gate boundaries

What did we do?

The effect of integrating bioenergy and dairy systems on GHG emissions was evaluated. First, a reference milk-producing system representative of Wisconsin (WI) was modeled using a partial LCA approach from cradle-to-farm gate. To integrate bioenergy products to the modeled farm, the boundaries of the system were defined and included corn and soybean production for ethanol and biodiesel, respectively. This was necessary in the analysis since co-products dry distillers grains with solubles (DDGS) and soybean meal (SBM) are part of the dairy diet in numerous farms of WI. In addition, the production of biogas through anaerobic digestion (AD) from the collected manure was evaluated as a second opportunity to integrate bioenergy systems with dairy systems. Given that this integrated system is multi-functional (producing milk, meat, ethanol, biodiesel and biogas); the GHG emissions were assigned to milk by system expansion, a method recommended by the International Organization for Standardization (ISO) to assign the environmental impacts of multi-functional systems among co-products. This method can be applied when a co-product clearly replaces the production of an external product (in our paper ethanol replaces gasoline and biodiesel replaces fossil diesel). Results indicate that GHG emissions for the reference system are 1.02 kg CO2-eq per kg of milk (corrected for fat and protein (FPCM). When analyzing the integration of ethanol and biodiesel (and after applying system expansion) GHG emissions are reduced to 0.86 kg CO2-eq per kg of FPCM in a diet that maximizes DDGS. The installation of a digester further reduced GHG emissions to 0.63 kg CO2-eq/kg FPCM, highlighting the importance of this system to achieve both energy and climate change goals.

Given the important role that AD systems have to reduce greenhouse gases, we explored different AD scenarios based on manure management practices, co-digestion strategies, and energy conversion processes in order to achieve further emission reductions. AD is the main focus of this part of the study; therefore, a new functional unit was defined as 1 GJ of produced electricity. A base-case pathway was compared against seven alternative AD pathways. In the base-case, manure is collected with a skid steer, digested in a plug-flow digester, biogas is used for electricity production without heat recovery, and digestate is separated in a screw press and land-applied by surface broadcast. The alternative AD pathways are defined in Table 1.

Table 1

For the base-case, GHG emissions are 243.3 kg CO2-eq/GJ of produced energy. Results show that the AD pathway has a substantial influence on the estimates of environmental impacts and GHG emissions range from 178 to 267 kg CO2-eq/G J of produced energy (Figure 2).

Figure 2.

What have we learned?

The dairy industry will continue to dominate agricultural activities in WI for the foreseeable future and the emerging bioenergy industry will need to be integrated into existing agricultural systems. System models like this one have potential to help farmers and policy makers identify synergies between dairy production and renewable energy development. GHG emissions of a reference dairy system representative of WI are compared to a system that integrates dairy and bioenergy production. Diet scenarios that maximize DDGS content are the most effective in reducing GHG emissions. Reductions in GHG emissions come mainly from the credits of avoided emissions and primary energy from displaced fossil fuels after system expansion. GHG emissions are further reduced when implementing AD to process the manure generated in the farm.

The second part of the study focused on improving the sustainability of AD systems by evaluating different manure management practices, co-digestion strategies, and energy conversion processes. GHG emissions can be reduced 31% by management practices alone, 24% if heat from the electricity generation process is recovered, and 4% by co-digesting manure with corn stover. Replacing sand with digested solids for cow bedding contributes to reduce GHG emissions as it avoids the manufacturing of this resource. Co-digesting corn stover with manure is an effective strategy to reduce GHG emissions as this feedstock requires only harvesting as opposed to switchgrass that needs to be added to the already existing crop mix requiring additional planting as well as harvesting. Finally, results show the major improvement in GHG emissions when heating the digester with recovered heat from the generator, highlighting the potential of this pathway to reduce environmental impacts without adding major technical or economic challenges to the farmer.

Future Plans

There is potential to expand the current analysis by using the survey data collected as part of this study. For example, it would be interesting to compare management practices coming from small and large dairy farm operations.

We still need to develop our knowledge on the sustainability impacts of co-digesting manure with other waste streams, such as cheese whey and whey permeate. These pathways can provide useful information to dairy processing plants about alternative uses of whey as an energy source with and without protein separation, which could be a decisive factor when making investment decisions.

It will be important to quantify other environmental services of AD systems, such as water quality preservation and odor reduction.

Authors

Aguirre-Villegas Horacio Andres. Postdoctoral Research Associate. Department of Biological Systems Engineering, University of Wisconsin-Madison aguirreville@wisc.edu

Larson Rebecca. Assistant Professor. Department of Biological Systems Engineering, University of Wisconsin-Madison. Reinemann Douglas J. Chair and Professor. Department of Biological Systems Engineering, University of Wisconsin-Madison

Primary author: Horacio Aguirre-Villegas, aguirreville@wisc.edu, 217-898-0345

Acknowledgements

This study is part of the Green Cheese Project, funded by Wisconsin Focus on Energy, Environmental and Economic Research and Development Program and the National Institute of Food and Agriculture, United States Department of Agriculture, under ID number WIS01604

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.