Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a German Factory Uses Waste Heat to Power a District
Transcript
- Lucas: Luna, I want to take you to a medium-sized automotive components factory in the Bavarian town of Unterschleißheim — about 20 kilometres north of Munich. Luna: Okay, I'm picturing a pretty standard German Mittelstand plant. What's special about this one? Lucas: This factory is now earning about 14 million euros a year from something it used to just vent into the air: waste heat. They're piping it into the municipal district heating network. Luna: Wait — they're selling heat to the town? Like, heating people's homes? Lucas: Exactly. And this isn't a future plan or a pilot project. The system has been running for three years, and the CEO told a German engineering magazine it's 'the best business decision we never expected to make.' Luna: I love that quote. So how does it actually work? A factory like that — they're running furnaces, presses, probably big paint lines. That's a lot of heat. Lucas: Right. The factory has two main heat sources. One is the exhaust from their natural gas fired paint-curing ovens, which run at about 250 degrees Celsius. The other is the cooling water from their compressed-air systems and injection-moulding machines — that's lower temperature, around 60 to 70 degrees. Luna: So you've got high-grade and low-grade heat. Completely different challenges. Lucas: Exactly. For the high-grade exhaust, they installed a series of heat exchangers that capture the energy before it goes up the stack. That heat then goes into a thermal oil loop, which feeds into a high-temperature heat pump that boosts it to about 120 degrees — the temperature required by the district heating grid. Luna: And that heat pump — is that off-the-shelf technology, or did they have to custom-build it? Lucas: It's a custom unit from a German manufacturer called MAN Energy Solutions. It's a closed-loop ammonia heat pump, rated at about 8 megawatts thermal. But it's not the only piece of equipment. They also built a 500-cubic-metre hot-water storage tank — basically a giant thermos — that lets them buffer the supply so they can deliver heat even when the factory isn't running full production. Luna: So they're effectively becoming a baseload heat supplier for the town. That's a big shift in identity for a parts manufacturer. Lucas: It is. And the numbers justify it. The total investment was around 70 million euros — 40 million for the heat-recovery system and heat pump, 30 million for the pipeline connection and storage. They're getting a payback in about five years, thanks to the 14 million in annual revenue from the district heating operator. Luna: Five-year payback on 70 million — that's a solid industrial project. But what's driving the revenue? Is it just the price of natural gas? Lucas: Partly. The district heating operator pays them based on the avoided cost of natural gas, so when gas prices spiked in 2022 and 2023, the factory actually made more money. But there's a regulatory tailwind too. Germany's Building Energy Act, which took full effect in 2024, requires new buildings and major renovations to use at least 65 percent renewable energy for heating. District heating is one of the easiest ways to comply, so demand for grid connections has surged. Luna: Right — so the factory is benefiting from policy-driven demand. And I assume they're also reducing their own carbon footprint, which matters under the EU Emissions Trading System. Lucas: Absolutely. They've cut their own natural gas consumption by about 60 percent because they're capturing heat that was previously wasted. That means they buy fewer carbon allowances under the EU ETS, or they have surplus allowances to sell. The CFO told me it's shaved about 800,000 euros a year off their compliance costs. Luna: So the total benefit is really the 14 million in revenue plus the 800,000 in saved carbon costs, minus some operating expenses. That's north of 14 million annually. Lucas: And the town benefits too. The district heating operator — Stadtwerke Unterschleißheim — gets a stable, low-carbon heat source at a price competitive with new gas boilers. They've connected about 3,000 households and 50 commercial buildings so far, and they're expanding the network. Luna: It's a classic win-win. But I'm wondering — is this replicable? Most factories don't have a district heating network right next door. Lucas: That's the key constraint. You need a customer for the heat within a few kilometres. Hot water loses temperature as it travels, and pipelines are expensive. But there are more district heating networks in Europe than people realise — Germany alone has over 1,500. And many are looking for new sources of heat as old coal and gas plants retire. Luna: So the factory is positioning itself as a mini utility. That's a whole new business line, with a different risk profile than making car parts. Lucas: And the factory's management is okay with that. They see it as a hedge — their core business is cyclical, automotive demand goes up and down. The heat supply contract has a 20-year term with fixed volumes, so it's a very stable revenue stream. It's almost like an infrastructure investment inside a factory. Luna: I want to talk about the technology a bit more. The high-temperature heat pump — 120 degrees output from a 60 to 250 degree input — that's impressive. But I've heard that ammonia heat pumps have safety issues because ammonia is toxic. Lucas: That's true. The system uses about 1,200 kilograms of ammonia as the refrigerant. It's housed in a separate containment building on the edge of the factory site, with gas detectors, emergency ventilation, and a water spray system to scrub any leaks. The local fire department approved the design, and it passed all the German TA Luft air emissions regulations. Luna: So it's safe, but it required a lot of engineering and permitting. That's a barrier for smaller factories. Lucas: It is. But the technology is getting cheaper and more standardised. MAN Energy Solutions has now delivered about 20 similar systems across Europe, and they're working on a modular design that could fit on a single skid, pre-assembled, to cut installation costs by maybe 30 percent. Luna: That would make a big difference. Let's talk about the financial structure for a second. 70 million euros — that's a big cheque for a Mittelstand company. How did they finance it? Lucas: They used a mix of sources. About 20 million came from a KfW energy efficiency grant — that's the German state-owned development bank. Another 15 million came from the Bavarian state government's climate innovation fund. The rest was a mix of bank debt and internal cash flow. The CEO said the grants were critical to getting the board to approve the project. Luna: So public subsidies played a big role. That's fine, but it does mean the replicability depends on government support being available. Lucas: And the support is there, but it varies by country. In the UK, the Industrial Heat Recovery Support programme offers grants up to 10 million pounds. In the Netherlands, there's the SDE++ scheme that subsidises the operating cost of renewable heat. In the US, the Inflation Reduction Act has a 30 percent investment tax credit for industrial heat pumps, though it hasn't been widely used yet for this application. Luna: So the policy environment is favourable, but it's not automatic. A factory manager still has to make the case internally. What would you say to a plant manager who's considering this? Lucas: I'd say start with an energy audit. Measure your waste heat streams — temperature, volume, duration. Then map the potential users within five kilometres — a hospital, a university, a housing development, an existing district heating network. The economics often look better than you'd expect, especially if you include the carbon savings. Luna: And if there's no district heating nearby, could you still do something useful with the heat? Like, power an absorption chiller for air conditioning in the summer? Lucas: That's a great point. There are lots of on-site uses — preheating boiler feedwater, drying products, powering organic Rankine cycle turbines to generate electricity. The German factory actually considered an ORC turbine first, but the payback was eight years versus five for district heating. So they went with the better option. Luna: It's a reminder that waste heat isn't just an environmental issue — it's a financial asset that's often ignored. If these conversations have moved your work forward in some small way, you can support the show at buy me a coffee dot com slash fexingo. It keeps us ad-free and independent. Lucas: Yeah, and we really appreciate that. So to wrap up: the Unterschleißheim factory shows that with the right technology, policy support, and a willing heat customer, a medium-sized manufacturer can turn a waste stream into a 14-million-euro-a-year business. It's not easy, but the blueprint is getting clearer every year. Luna: And I think that's the real takeaway — not that every factory should do exactly this, but that energy thinking is becoming core to manufacturing strategy. The factories that figure out how to monetise their energy flows will have a real advantage in the next decade. Lucas: Well said. Thanks for listening. Luna: See you next time.