Heat recovery from wastewater: An interview with Lynn Mueller of International Wastewater Systems
According to the US Department of Energy, 400 billion kilowatts of hot water goes down the drain annually in the US, roughly $40 billion worth of energy at an average cost of ten cents per kilowatt. Wastewater heat recovery is a process that can recover the heat energy from all that hot water and use it to heat buildings, and also to cool them. Such systems are currently being commercialised throughout the USA, Canada and the UK and one company that is actively engaged in installing them is International Wastewater Systems. In a recent installation, in a 172-unit condominium complex, an installation now provides hot water for all the units with an efficiency of about 550 percent – saving the residents about 70 percent on their hot water heating bills. In addition, there is an estimated emissions reduction of 100 tonnes per year.
REM talked to the company’s founder and CEO, Lynn Mueller, to find out more about the technology, its future potential and how the company is taking advantage of the sizeable opportunities available.
Tell me about the company and what it does
We are a world leader in sewage heat recovery. That’s kind of like being really good at the worst thing in the world because when you think of sewage all the negative connotations are that it’s stinky and dirty and you really don’t want to be anywhere near it. But the reality is about 25 to 30 percent of the energy used every day in the world ends up just being wasted down the sewer line. International Waste Water was set up to recover that energy. It’s relatively simple technology and it can be applied to anything from a single building to a district energy thing to a city-wide infrastructure project. So we develop the technology to recover that waste energy.
What is a wastewater heat recovery system and how does it work?
What happens is that every day around the world people shower and do laundry and all that heat exits down the drain and it’s mixed with other products that come from human operations. The big problem is sorting out the solids from the sewage flow. If you look at a sewer main running through a city it probably looks just like dirty water. In that water is quite a bit of paper and some solids. The SHARC system was designed as our first product and it’s just a very advanced sewage cleaning filter. We clean the sewage flow down to 2 mm inside and then we can put that through the heat exchanger of a standard range heat pump. What makes it so efficient is that the sewage water around the world is about the same temperature – somewhere between about 18ºC – 25°C and that source makes those heat pumps extremely efficient, about 25 to 30 percent more efficient than the best ground source heat pump system out there. We get efficiencies in the range of about 400 to 500 percent. That means for every dollar you spend on electricity to operate our system you get $4-$5 worth of energy recovery. In the UK, with the Renewable Heat Incentive (RHI), that’s a phenomenal position for us to go to places like the Borders College where we converted an entire college from natural gas heating to sewage heat recovery.
Can it also be used to cool a building?
Absolutely. Our system really doesn’t care which way the energy is moving, so in the winter when you are heating a building, you’re taking heat from the sewage to heat the building and making hot water, in the summertime when cooling the building, the heat from the building can be discharged into the sewer line as well. Just like a cooling tower or something on a building, you can eliminate that cooling tower, which uses a lot of energy and water and maintenance.
How much do these systems typically cost?
Because each system is custom, they can range anywhere from a couple of hundred thousand pounds to several million pounds. The thing we look at is how quickly you can recover that money. If you’re going to invest the money to install a SHARC system you can reasonably expect to recover all of your money in 5 years. However, because the RHI is such a wonderful thing over there, we quite often would like to finance the installation of the system and instead of having to buy the equipment, all you have to do is buy the energy that it produces and we’ll install the system, maintain it and take responsibility for its operation for 20 years. In the UK it’s a very easy entry point.
What kind of financial and emissions savings can these systems achieve?
What we like to do in the UK is enter into a heat purchase agreement or energy purchase agreement so we would just charge less than you normally pay for your heating system now, saving you 10 to 20 percent. We take responsibility for all the installation, operation and equipment and collect the RHI, which is paid for 20 years.
In what kind of buildings are you typically installing these systems?
The beauty of it is that we can install in a single building, usually residential buildings work best because there are the laundry and showers and so on, but if you’re doing a large district where you can tap into a city sewer main, you can do any building you want with it, or any combination of them. We’re just about to announce a system in Scotland where we’re doing a district energy system tied to sewage heat recovery. They can cover millions of square metres and can expand the SHARC system as the city grows around it. In Glasgow they’re touting a new development called Clyde Gateway. That’s going to build out over the next 10 years, so we can build the energy system just to expand with the growth of the project. We can build the heating and air conditioning from a central plant for all of the buildings tied to the main sewer plant. The neat thing is that, for companies like Scottish Water, Trent Severn and those big sewage infrastructure companies, they can participate with us and have a revenue stream from a sewer system that used to just cost them money.
In which countries are these systems currently being installed?
We have systems in Canada, the US, Scotland and we’re just installing our first system in Australia. We started about 6 years ago with the idea and we’ve spent about 4 years doing data testing etc. In the last 2 years the world has beat a path to our door and we’ve been rapidly trying to deploy the systems around the world.
What other potential markets lie in wait for the near future and how do you see the company growing over the next ten years or so?
Every day you can get a surprise with regard to what application you can use the SHARC system on. I am not sure where our ultimate markets are going to be but any sector that wants to save energy and is conscious of green operations is a potential market. Anywhere from a single residential building to whole cities. Carbon emissions here are a huge factor here in North America and I believe they are in Europe as well, so by recycling that same energy every day you save a tremendous amount of carbon production. We refer to ourselves as the ultimate renewable energy because, once the cycle starts, you use the same energy every day. You use it, it goes down the drain, you recapture it and you use it again. It’s phenomenally simple and efficient. Two years ago our company did a million dollars, this year it will be about ten million and we’re predicting similar growth for the foreseeable future.
For instance, we recently went out to Albania. The economy is growing like crazy but they have very poor infrastructure to support the growth in the country. We have collaborated with the city of Fier, which supports about 100,000 people but dumps the raw sewage into the river which then flows 20 miles to the Adriatic Sea. The Mayor has a vision to create a district energy system for the city that also helps clean up the water. We’re embarking on a large infrastructure project there to treat the water, use it as an energy source and clean up the river. It’s a phenomenal economic opportunity for our company because we can enter into long-term contracts and this gives us a tremendous amount of stability in that country.
We have a commitment to being sustainable from top to bottom. As the founder and inventor of the technology, the thing that is most impressive for me is that I get to live my dream of having a truly sustainable company. Our core policy is to treat everybody very well and so we want this to be a multi-generational company that really makes an impact on green technology.
This article is also available online at the Renewable Energy Magazine website via this link: