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Welcome to The Executive Exchange, a premier podcast series for on-the-go senior executives. Each episode features short, impactful podcasts where industry leaders share key insights and experiences from the water industry.
[00:00:00] Piers Clark: Welcome to the Exec Exchange, 15-minute podcast in which a leader from the water sector shares a story to inspire, inform, and educate other water sector leaders around the globe.
[00:00:09] Piers Clark: My name is Piers Clark, and my guest today is Scott McClelland, the General Manager at Encina Wastewater Authority. And today we're gonna be talking about how they have been able to make a 100% renewably-powered wastewater treatment plant at scale.
[00:00:27] Piers Clark: Scott, brilliant to have you with us today.
[00:00:30] Scott McClelland: Glad to be here.
[00:00:31] Piers Clark: Now, we like to start by asking our podcaster to share a little bit about their background. Walk me through what have you done to get to being general manager of Encina Wastewater Authority?
[00:00:43] Scott McClelland: I grew up here in the San Diego area and I was a swimmer, lifeguard, the quintessential Southern California kid.
[00:00:49] Scott McClelland: I graduated with a Bachelor's of Science degree in Environmental Engineering from Cal Poly, San Luis Obispo. And I started designing water and wastewater treatment plants. And I spent 10 years designing for a big multinational consultant. One of them worked on Thames Water for a while.
Ultimately, one of my clients, which was a water utility at the time thought that it might be a good idea that I come work for them, and I decided, "Well, I'll give it a try." So I've spent the last 23 years in the utilities business now, and I've got about 33 years of experience in the water, wastewater field.
[00:01:22] Scott McClelland: I've been a GM at Encina for five years now. I came to Encina about 10 years ago as the assistant general manager.
[00:01:30] Piers Clark: Excellent. Let's now talk about Encina. Where are you? How many people do you serve? And you're wastewater only, correct?
[00:01:38] Scott McClelland: Encina Wastewater Authority is a bit of an unusual entity. It's called a Joint Powers Authority, and of course, in California we've got names for all kinds of things. Basically, it's six agencies within the North San Diego county region, and so we serve about 380,000 people in the region that's about 40% of the San Diego regional economy. And I look at this in the larger context of what does that mean from an economic perspective, because wastewater treatment plants in particular are really part and parcel to the economic engine of the region.
[00:02:12] Piers Clark: Brilliant. Now, the topic we're going to talk about today is the wastewater-energy nexus and how impactful wastewater treatment can be on the energy balance of a water treatment plant.
[00:02:23] Piers Clark: First of all, let's frame the challenge.
[00:02:26] Scott McClelland: The real challenge is in the wastewater sector as a whole, we consume a lot of energy to do a variety of different treatment processes there. In the consumption of that energy, we are effectively disposing of energy through a variety of different ways. And so you think about a typical wastewater treatment plant. It's got blowers running, and it's got a bunch of pumps and chemical feed systems, and those are all power consumers as well.
[00:02:51] Scott McClelland: Most wastewater plants, particularly the size of Encina, have anaerobic digestion systems, and they're producing biomethane and biogas there. And I hate to say this but a lot of plants flare that, and that's effectively, if you will, money going up in smoke.
[00:03:08] Scott McClelland: So when you think of that in the context of wastewater operations implementing cogeneration systems, which Encina has done using that biogas to produce electricity since 1982. But what we haven't been able to do is really get to that 100% renewable energy goal that I know a lot of plants would like to get there.
[00:03:29] Scott McClelland: And it actually is a lot easier than you might think, particularly considering some of the new technology that's on the market today that's very high efficiency and very low emissions.
[00:03:39] Piers Clark: And it's particularly pertinent, of course, in a world where we have incredibly volatile energy prices. Actually, what you're describing is a way of getting energy independence from the grid. Doesn't matter what's happening with the price of oil, you have energy security. So I know that, Encina, you've got a project called CLEAR, C-L-E-A-R, the CLEAR project, which encompasses a number of technologies.
[00:04:05] Piers Clark: So let's talk about the CLEAR project, and I know you were nervous about sharing the anagram, but let's get that out the way first. What's the acronym that's behind the name CLEAR?
[00:04:14] Scott McClelland: The 'CLEAR' stands for Cogeneration Low Emissions Augmentation and Retrofit . And so really what that project is about is we were handed a requirement from our local air pollution control district to effectively clean up our emissions and that was the impetus.
[00:04:32] Scott McClelland: And so we took that mandate and we looked at that with regard to what Encina has from an energy resource availability and what the market actually could support as far as our going to the next step and actually getting to that 100% renewable energy platform.
[00:04:50] Scott McClelland: It's a resilient, reliable, off-grid solution but it's not just cogeneration systems. It's linear generators, it's batteries, it's microgrid controllers, it's gas-conditioning systems. And so it truly is a very complicated system with lots of moving parts, but when you get it right, everything's working in unison, you have a fantastic system.
[00:05:14] Piers Clark: I get that it's going to be too big a scheme for us to cover in the few minutes we've got chatting here, but imagine you're a utility executive on the other side of the world listening to this thinking, " Well, I'd like to make my wastewater treatment plants 100% energy independent."
[00:05:28] Piers Clark: What are the big items that they need to know about, that they need to adopt and bring on board to be able to achieve what you're achieving at Encina?
[00:05:36] Scott McClelland: It really all starts with biogas resources, the raw material, if you will, that you create the energy from. A lot of wastewater plants that I mentioned earlier, they have anaerobic digesters. You can enhance the gas production within those anaerobic digesters by adding FOG, fats, oils, and grease which we do here at Encina.
[00:05:55] Scott McClelland: You can add beer waste which has been a tremendous, shall we say, adrenaline kick to the bugs in the anaerobic digester system.
[00:06:03] Piers Clark: So high calorific feed stocks that you can find in your local area that you can bring into the digesters to co-digest with human waste, correct?
[00:06:12] Scott McClelland: Correct, yes. There is actually technology out there called microbial hydrolysis processor, MHP, which enhances that even further, and you can get better solids destructions in the digesters and get an even cleaner gas off of that as well.
[00:06:27] Scott McClelland: So there's a variety of different ways of increasing that biogas availability, which is really key to actually being able to get to that 100% power generation. And every 200 cubic feet of anaerobically digested biogas is about one megawatt worth of power.
[00:06:45] Scott McClelland: So it's an easy go-by to kind of say, "Okay, well, how much can I really generate there?"
[00:06:50] Piers Clark: And just going with that waste that's brought in, you're charging for it? You're charging a gate fee on the commercial waste, the beer waste and FOG?
[00:06:58] Scott McClelland: Yes. We do have a tipping fee associated with the FOG.
The FOG comes in clean, we charge a little bit less than if it comes in just straight off the grease traps. And the beer waste is even cheaper still because it's pretty much all carbohydrate and volatilizes really quick.
[00:07:12] Piers Clark: And what does it do to the amount of sludge that you're producing at the back end of the digester that then needs to be disposed of, and how are you disposing of those?
[00:07:21] Scott McClelland: We have really not seen any increase in biosolid sludge due to the addition of FOG and beer waste. Again, you're talking about lipids and carbohydrates. They volatilize really quickly, so you don't really see an increase in that.
[00:07:35] Scott McClelland: Encina takes the anaerobic digested sludge and we run it through a heat dryer system. It's an Andritz unit. It's a triple pass rotary kiln. And we create actually a very fine fertilizer pellet. And Encina also has a branded fertilizer, it's called Pure Green, that we beneficially have used on croplands, mostly ag crops for grass and cattle feed grass.
[00:07:58] Piers Clark: And are there any regulatory issues in California around co-digested waste as opposed to normal wastewater biosolids?
[00:08:06] Scott McClelland: Yes. It's licensed in the state of California and the state of Arizona as a fertilizer. We have a trademark with it. It's a 550 fertilizer. It's not a complete fertilizer, but it's got a lot of humic and fulvic acid in it, and the plants love it. I use it in my yard, and my avocados are big.
[00:08:24] Piers Clark: Yeah, there's nothing like proof being the advocate yourself.
[00:08:28] Piers Clark: So I've got it. You've got your digesters. Get the most out of the digesters with the feedstocks that you're putting in, ideally finding ones which will act as rocket fuel and be hopefully fully volatilized, fully converted, therefore you don't get more biosolids at the end. And then you mentioned that microbial enzymatic hydrolysis. There's quite a few ways that people do hydrolysis in digesters, but that's one of a number of them.
[00:08:51] Piers Clark: What else would we need to look at?
[00:08:52] Scott McClelland: So I think the other side of this is really the efficiency of the post-biogas production and the biogas scrubbing and polishing and the actual consumption of the biogas.
[00:09:03] Scott McClelland: And so if you're just using typical cogeneration engines, which are reciprocating engines, you're getting maybe 30, 31% efficiency off of that. And what you also need to do is look at other systems out there so you can actually realize a 40 to 45% energy efficiency off of a linear generator system. Particularly we're contracted with Mainspring Energy out of the Silicon Valley area to produce energy in their units. We're getting four 250 kilowatt units for that. And so that increases the actual available energy. Again, the efficiency of the unit is much higher than a reciprocating engine.
[00:09:41] Scott McClelland: You could go another step and produce effectively an RNG, renewable natural gas, which is pipeline standard gas, and you can run that gas through a fuel cell if you really wanted to go to another layer of efficiency and get to almost 55% efficiency on that power generation with that.
[00:09:58] Piers Clark: I like this idea of you gotta think about not just how much gas can you produce, but what do you do with that gas.
[00:10:03] Piers Clark: Do you need to clean it?
[00:10:05] Scott McClelland: Yeah, absolutely. Particularly linear generators which are a very robust machine as far as what fuels they can burn and the quality of those fuels. You always, like any other biogas that you're using, you've got to scrub it for sulfur, and you've got to scrub it for siloxanes at a bare minimum.
In the linear generators, the fuel cells, you gotta get the carbon dioxide out of that gas stream. And those are also critical to us meeting our emissions requirements, that was the primary driver for the project.
[00:10:32] Piers Clark: Of the five letters in the CLEAR acronym, two of them are for low emissions, so it's gotta be there, isn't it?
[00:10:37] Scott McClelland: Exactly. And that's a part and parcel to the success of the project. It's not just about generating 100% of our own power. It's really about generating that cleanly and meeting those emissions requirements that we have from the state as well.
[00:10:51] Piers Clark: Excellent. I love this idea of get the maximum amount of gas, and then clean it up.
[00:10:56] Piers Clark: What sort of things could you do beyond that then?
[00:11:00] Scott McClelland: Once you've kind of met your biogas or energy needs for your plant, you can go back to utilizing that MHP process and really increase the FOG, and the beer waste, and maybe the green waste that even comes in, because MHP is a very effective cellulose digester. That provides you a cleaner and even more gas out of it.
[00:11:21] Scott McClelland: And what Encina is looking for in the near future is, because of digester capacity constraints and our need for additional digestion capacity, we'll probably be realizing about 200% of our own biogas needs in the near future.
[00:11:37] Scott McClelland: And so that excess energy can be applied to a variety of different things, and one of which is actually the purification of water, particularly in Southern California and where everything is about direct or indirect potable reuse right now.
[00:11:50] Scott McClelland: You can use that excess energy that you produce in the wastewater treatment facility to offset the cost of the water. And I'm not talking about a little bit, I'm talking about 30 to 40% of energy offset. That's a big number.
[00:12:04] Scott McClelland: When you're talking $2,800 an acre foot for water, and I apologize for the English units, it's a lot of money. And that's how you can drive down the actual cost of production for purified water.
[00:12:14] Piers Clark: Excellent. I love this sort of virtuous circle of what you can do with your surplus energy to feed back into the water cycle to make it all balance.
[00:12:22] Piers Clark: Scott, we're running out of time, and we like to finish with a slightly cheeky question, which is to ask you to get in a time machine, go back 30, 40 years to when young Scott was there, down at the beach with his surfer shorts on and his surfboard.
[00:12:37] Piers Clark: What advice would you give young Scott McClelland?
[00:12:42] Scott McClelland: When I think about this, I really go back to something that one of my bosses told me early in my career, and that is, "You never really know what you're capable until you get out of your comfort zone."
[00:12:53] Scott McClelland: And so you need to look for opportunities to expand that envelope of experience, try new ideas, and learn what works and what doesn't work. And maybe change the process so that you're successful in the future. And so that's my advice to myself.
[00:13:08] Scott McClelland: And I'm glad my boss 20 years ago told me something like that, 'cause I haven't forgotten and I've tried to practice that where I can.
[00:13:15] Piers Clark: You have been listening to the Exec Exchange with me, Piers Clark, and my guest today, Scott McClelland, the general manager at Encina Wastewater Authority.
[00:13:23] Piers Clark: I hope you enjoyed it. Thank you to our sponsors, and until next time, keep asking questions, keep sharing, and keep safe.