The Book on Biogas

A national database sheds light on treatment plant digester methane and the role it plays in the nation’s renewable energy initiatives.
The Book on Biogas
The Biogas Data website home page.

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Digester methane (biogas) is gaining huge favor as a renewable fuel — it has come to be seen as part of the nation's effort to conserve fossil fuels and reduce greenhouse gas emissions. But how many wastewater treatment plants produce biogas? And what do they do with it? What is this fuel's true potential?

A research project led by the North East Biosolids and Residuals Association (NEBRA) and the Black & Veatch consulting engineering firm set out to answer those questions. Using seed money supplied by the Water Environment Federation (WEF), and with help from numerous collaborators and advisors, the research team collected information on biogas generated at treatment plants in all 50 states and assembled it in a database now available to the public at

It's the first step in what project organizers hope will be an ongoing effort to develop comprehensive data on biogas and its viability as a resource. The results already are of interest to biogas project developers, engineering consultants, policymakers, and others who rely on solid data to conceptualize, design and develop renewable energy and resource recovery projects at treatment plants.

Co-principal investigators on the project were Ned Beecher, NEBRA executive director, and Lori Stone, biosolids global practice and technology leader with Black & Veatch. Beecher talked about the database in an interview with Treatment Plant Operator.

How would you sum up the basic aims of this data-gathering project?

Beecher: There were two basic objectives — first, to assess biogas potential in existing anaerobic digestion systems at U.S. wastewater treatment plants; and second, to summarize the current uses of this biogas and potential future opportunities for its use.

How did this project originate?

Beecher: WEF put out a request for proposals. Lori Stone at Black & Veatch brought it to my attention. There has been considerable interest in renewable energy generation, and when it comes to wastewater treatment plants, there has been a lot of focus on anaerobic digestion and biogas. WEF recognized that there was a lack of reliable data in those areas.

The U.S. EPA and the Combined Heat and Power Partnership collaborated on a 2011 report on the potential of biogas from anaerobic digestion. It was a pretty good report, and its purpose was excellent, but people in the field recognized that the data was incomplete.

Here at NEBRA, we would frequently get calls from people looking for data on anaerobic digestion, and we knew of a number of private companies and technology vendors who wanted to work in that field. They all seemed to be out trying to do their own data collection. But because this was not a very mature field, there was no single consolidated database.

How did you go about collecting the data that is now available on the website?

Beecher: It was an arduous process. We knew from previous experience that there was no quick and easy way to do it. Essentially, our approach was to choose a data collector in each state who would likely know who the best resources in that state would be and might even know some of the data directly.

We handled the New England states out of the NEBRA office. In California, the state's Association of Sanitation Agencies biosolids person did the work. The Northwest Biosolids Management Association handled Oregon and Washington. Then we split up the states where we didn't have obvious contacts. NEBRA ended up doing a lot of it.

Generally, the protocol was to start with the biosolids coordinator in the state government, or with someone well positioned to know about biogas at wastewater facilities in the state. Often, that was a consulting engineer. We would talk to them and determine who the best sources were, and then go to those sources.

Was there any information available to use as a starting point?

Beecher: We were able to start with a database built on EPA Clean Watershed Needs Survey information, and with work that InSinkErator had done to identify facilities with anaerobic digestion. InSinkErator had hired an intern in 2011 who created a spreadsheet that identified a lot of anaerobic digestion facilities using information from websites. That was a step up from what had existed before, but the fact remains that many city websites are unreliable, because they don't get updated very often.

Once we had a sense of which facilities in a state had anaerobic digestion, we called the larger anaerobic digestion facilities in that state and asked them to confirm that our list was complete. Then we called those facilities and collected the data from them. The Mid-Atlantic Biosolids Association created an online data entry system. Another tool at our disposal was a Survey Monkey online survey that allowed facilities to enter their own data if they wanted to.

Did you end up with a complete list of all anaerobic digestion facilities in every state?

Beecher: For the most part, yes, but time didn't permit us to be as thorough as we might have liked. We certainly accounted for all the large anaerobic digestion facilities. In our final report, we present a graph that shows our confidence level for each state. For example, Texas and Maryland are two states where we have lower levels of confidence. On the other hand, for Alaska and Maine, each of which has only one anaerobic digestion facility, we're 100 percent confident we've identified them all. And there are a number of other states where our confidence is quite high.

What information did you gather from the facilities you contacted?

Beecher: In meetings with the project team and an advisory group that WEF put together, we defined the data that we considered the most essential and that we thought we could get fairly easily. We called this Phase 1 data.

For example, we asked: Do you have anaerobic digestion or send your solids to an anaerobic digestion facility? Do you take in outside waste and feed it directly into the digesters? How do you use the biogas? Is it burned in boilers for digester heating? For building heating? Do you use it to generate electricity? If so, with what generating technology?

Did you ask about the volumes of biogas produced and consumed?

Beecher: We did not collect that data, although that is something people really want to know. We didn't collect that because we knew it would be too hard to get in a first pass. A lot of facilities don't measure it. It takes a lot of planning to figure out how to collect that information and how to separate estimates from actual measurements. But we now have the contact information of the people who know the most about biogas at each plant, so we can go back with follow-up questions.

What are some of the basic findings from the research?

Beecher: We identified 1,238 plants in the U.S. that have anaerobic digestion and produce biogas or send their solids to an anaerobic digestion facility. That's a fairly small percentage of the 15,000 to 16,000 permanent wastewater treatment facilities in the nation, and it's because many of those are smaller package plants.

Only about 300 plants use biogas to generate electricity. About two-thirds of the plants that produce biogas put it to use for energy in some form. The most common use is for digester heating. About one-third of the plants flare some gas, and a few just release it directly to the atmosphere, which is not necessarily a good thing. Those are smaller facilities, of course.

One surprising finding was that there are some pretty small facilities with anaerobic digestion — plants with flows from 1 to 5 mgd, and even some with less than 1 mgd. And some of them even use the gas to generate electricity.

What would you say is the real value of all this information? To whom is it useful and for what purposes?

Beecher: It addresses a need among people in the field, whether they be policymakers or commercial vendors, who are interested in understanding the market potential of biogas. Now they have access to data that, while not perfect, is quite a bit more accurate than what was around before.

Furthermore, the biosolids and wastewater coordinators at the treatment plants that have anaerobic digestion are finding the data useful for networking — for being able to understand who is doing what with biogas. They can look up who else in their state is using it that they may not have known about, and they can see what's going on in other states. This helps them share best practices and get advice. That's a benefit we really hadn't foreseen.

You mentioned that you've collected Phase 1 data. Do you envision a Phase 2?

Beecher: The parties to the project are discussing what to do going forward. We were fortunate last year to receive quick seed funding from Cambi, NYSERDA and the National Biosolids Partnership to create the initial website. Now we're looking for funding to support online database enhancements. At this point, the website presents some nice data, but doesn't have a download feature or reporting functions, which would be nice to have. We have the beginnings of a back-end data entry system that we would like to complete, so that eventually organizations would be able to enter their own data, subject to our approval. That would help keep the data current.

Might a Phase 2 involve collecting data on biogas volumes?

Beecher: That will be a primary goal if we go ahead with Phase 2. There's great interest in that. That's going to take some discussion around how we go about designing that question — we want to be sure we get it right.


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