Sustainability: Food Waste-to-Energy Study

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The City of Tempe and ASU’s Julie Ann Wrigley Global Institute of Sustainability are teaming up for a study that will analyze food waste, fats, oils and grease from large Tempe food industries, restaurants, and dining halls to determine the feasibility of turning this material into renewable energy. David McNeil, Tempe’s Environmental Services Manager, will tell us more.

Ted Simons: Tonight's look at Arizona sustainability focuses on how the city of Tempe is teaming with ASU for a study that will analyze ways to turn food waste into renewable energy. Joining us now is David McNeil, Tempe's environmental services manager. Thank you so much for joining us tonight.

David McNeil: Thank you for having me.

Ted Simons: Converting food waste to renewable energy. Explain, please.

David McNeil: Well, the -- this process happens -- it is a process called anaerobic digestion. Bottom line, when you think of taking rich organic matter and turning it into energy, it's done through a process where -- that's depleted of oxygen, and microbes that essentially digest food, organic matter in the absence of oxygen, produce gas. Same thing happens in the large intestines. Same thing that happens in that type of facility happens in our large intestines. Organic matter, bugs create gas, but in this case, we're talking about an industrial scale type of process where gas is created and you capture that gas and you can use it as renewable energy in several different ways.

Ted Simons: Removing oxygen. Digestive bacteria, you break it down. Biogas is produced. How much biogas can be produced by, I don't know, a chicken sandwich. Give me the idea of food waste and how much gas can be produced.

David McNeil: I think that varies depending on the source. Different types of food waste have different concentrations of organic matter and different energy potential. And that's one of the thing that this study will look at. We will survey the different food sources available to us in Tempe, and try to quantify how much gas we can produce. With those results, we can determine exactly what type and size of facility we might construct, how much gas we can produce, the value of that gas, and how long it would take to pencil out an investment.

Ted Simons: So the idea to look at is going as far as building a facility, or using an existing facility to focus and concentrate or collect.

David McNeil: These are two opportunities. In fact, what the study and partnership with ASU will do in the end will kind of pencil out three different options, and it might be using existing infrastructure, but more than likely, constructing new infrastructure at different locations, using varying forms of technology that are out there. And determine exactly what that facility would look like. It might not be that it would provide an adequate return right now.

Ted Simons: Right.

David McNeil: But the information we gather over the next eight to 12 months will ultimately allow us to revisit this opportunity in the future as energy prices change, as technology prices change, and as costs associated with capturing and the logistics behind capturing this food waste change.

Ted Simons: Is it a little bit -- waste water treatment plants as well?

David McNeil: That's precisely where it is happening already. Many communities nationwide who use existing or excess capacity in sludge digesters. When you take wastewater as sewage treatment, separate the water and sludge component. Take the sludge, put it in an anaerobic digester and bacteria break it down to lessen the quantities, more easily disposed of and that creates gas. Many cities in the nation are actually inserting food and grease, other organic matters into that process to boost the energy production.

Ted Simons: We hear about -- diesel engines -- different kind of process?

David McNeil: Different process. Typically that happens when you've got a vegetable oil that you capture before it is actually part of the waste stream, and it requires much less processing.

Ted Simons: Okay.

David McNeil: But very similar.

Ted Simons: No microbes, no digestive anaerobic whatever it is.

David McNeil: Right.

Ted Simons: How are you going to procure all of this food waste?

David McNeil: Well, you know, that's one of the things that we are going to look at through the study. One of the things that is unique about Tempe, in terms of -- being able to look at this opportunity, as many people don't think of Tempe as an industrial city but we really do have a lot of industry. We have roughly a third of the number of large industries that the city of Phoenix has despite only having a tenth of the population and area. Among those industries that we have, roughly a quarter of them have some sort of food component or food-based large industry. We have a number of targeted businesses or areas where we can look for food waste and what we intend to do over the next eight months is not only quantify how much waste is out there, but analyze it through chemistry analysis, determine what the energy potential or energy content is, and also look at its security -- secure ability from an institutional standpoint. In other words, can we get commitments from some of the food-based businesses to give us this waste over a 20-year period. If we build a facility, third party investing in a facility, we need a commitment to have this waste stream coming into a facility for an extended period of time.

Ted Simons: What happens, dairy area, coca-cola bottling plant, what happens to the waste now?

David McNeil: That waste is typically carried off site. I think that some of those industries are shipping it off to folks who do some sort of recycling, but it's, to my understanding, it's quite a distance away. I know some of the waste is sent to Buckeye, some to Maricopa. The opportunity to not only turn it to renewable energy but in a closed system within Tempe would be a great opportunity and some of our businesses have asked us when we're going to explore these.

Ted Simons: Interesting. That's encouraging. Again, as far as the biogas, once you get it done and once you have the -- the gas is there. It is available for use. Available for use as what?

David McNeil: Well, that's another thing the study will look at. I think that we believe that the lowest hanging fruit is compressed natural gas. And using it on site. If we can capture this gas and process it minimally, and compress it and use it in things like regional transit vehicles or city vehicles that now run on compressed natural gas, that would be -- we believe more efficient and have a better return than doing things like generating into kilowatts or electricity or putting it on the regional gas pipeline. We believe use in Tempe will ultimately prove to be a better, more efficient use than sending it elsewhere.

Ted Simons: That makes sense to me. Time line for the study, what have you got there?

David McNeil: Over the next eight months, you know, eight to 10 to 12 months, we plan on having not only a map, which will point to where our food waste sources are, how much waste there is in each of these locations, what the energy content is, but also, you know, having a map that will give us an opportunity to look at different citing options and what different combinations of this waste could produce in terms of energy. We plan to have that report, that product done by I would say mid fall.

Ted Simons: All right. By then we will ask you back and get more information. Good to have you here. Thanks for joining us.

David McNeil: Thank you for having me.

David McNeil:Manager, Tempe's Environmental Services;

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