Why heat is a challenge in the fight against climate change, and what we can do about it

Heat comprises half of the world’s total energy consumption – which is significantly more than electricity (20%) and transportation (30%). Unsurprisingly, heat contributes more than 40% of global energy-related carbon dioxide (CO2) emissions.

Yet most climate efforts have been focused on decarbonizing electricity and cars. It was only last year, after Vladimir Putin’s invasion of Ukraine and the ensuing energy crisis, that attention and efforts on decarbonizing heat really accelerated.

This might be the hardest battle – but also the biggest untapped opportunity – in the climate fight.

Where is heat being used?

On average, about 60% of home energy demand in the United States is used for heating, with that number reaching approximately 80% in Europe.

Fortunately, the required heat here is low temperature, so electric heat pumps and renewable electricity are making headway towards reducing emissions.

In commercial and professional settings, the use of heat is even broader. Beyond just supplying warm air and water in offices, heating also becomes critical. Think about the fast food burger you had; the roasted beans for your latte; the laundering of your bedsheets and towels at a hotel; the scalding steam and hot water that sanitizes everything from dishes to scalpels at a hospital.

Industry the biggest user of heat

But the biggest user is industry, which uses 50% of all heat, where it is an essential component of manufacturing, including refining raw materials, smelting metals and producing chemicals.

Heat is also used in the production of everything from paper to rubber, to the huge variety of food and beverage products, such as baking bread, brewing beer and pasteurizing milk. Indeed, the four materials on which of human civilization thrives – ammonia, cement, steel, plastics – all heavily use heat in their production.

To really highlight the challenges of decarbonizing commercial and industrial heat, let’s look at how green products are manufactured.

A completed solar panel has heat just about everywhere in its production lifecycle before it arrives on your roof. The core component is the silicon wafer, the formation and purification of which takes place at 1,400-1,700°C to create the silicon ingot. This silicon then needs to be doped to increase conductivity, typically above 800-1,000°C in a diffusion furnace.

To protect this solar cell, it is then sandwiched between protective layers of glass and resin, where heat is applied to cure the resin, and the glass itself was produced with sand and other materials melted together in a furnace reaching over 1,700°C.

The electrical components of the panel were soldered at over 400°C and bonded, and if there are ceramic insulators, those were made through firing and sintering at over 1,000°C. The plastic and cardboard packing used in the shipping of the final solar product were also made with heat at around 200°C; with plastics are often extruded, moulded and even thermoset with heat, and paper pulp decomposed and dried with heat.

It’s not just solar. The cement in our wind turbines has been through pyroprocessing in a 1,400-1,500°C kiln. The copper in the wires of your electric vehicle were likely heated in the steps of annealing, forming and tempering, let alone all the metals and plastics composing the car body.

Here’s the issue: these temperatures are high. Indeed, 70% of all industrial heat is above 100°C and almost half of industrial heat is above 400°C.

Unfortunately, the laws of thermodynamics prohibit electric heat pumps from efficiently producing high-temperature heat. Because the price of fossil fuels is often three to five times cheaper than delivered electricity at the end of the grid, businesses cannot economically switch over.

Although renewable power is becoming cheaper to produce, the gap for the end customer is unlikely to close, as the grid itself is a significant component of cost. In the US, transmission and distribution costs are already 44% of the total cost of delivered electricity. For commercial and industrial heat, there is usually no efficiency and economic savings for going all electric.

So the vast majority of this heat is generated through the burning of fossil fuels today. What can we do to reach net zero?

Heat solutions under development

One option is to relocate your business and factory to an area with a consistent and cheap supply of zero-carbon electricity 24/7. This is why Iceland’s biggest export is aluminium, due to the volcanic country’s abundant and affordable geothermal power.

Electric arc furnaces can use renewable electricity to reach high temperatures, but they have limitations, such as the being only able to heat conductive materials like metals.

Biofuels are another option. Organic fuel sources such as wood chips, sawdust and agricultural waste can be burned in boilers or furnaces. This can have good synergies with biomass-heavy industries.

For example, many paper and pulps mills burn their unused wood waste to produce clean heat and food processing companies often have biomass and biogas as part of their decarbonization strategy for renewable heat.

Hydrogen can burn at around 2,000°C, so hydrogen can also provide a low retrofit solution to commercial and industrial heating equipment. However, traditional production of hydrogen emits plenty of CO2.

So we’d need to produce hydrogen through water electrolysis powered by zero-carbon electricity, AKA green hydrogen, or from natural gas and biogas with pre- or post-combustion carbon capture, AKA turquoise or blue hydrogen.

However, clean hydrogen is not yet affordable, and hydrogen is an uniquely challenging fuel to transport and distribute. These challenges will need to be solved before hydrogen is widely used.

Carbon capture and storage (CCS) involves capturing CO2 from the smokestack, and storing it underground. CCS can be applied to large point sources of carbon emissions such as major industrial factories.

However, capturing and compressing carbon requires energy, reducing the overall energy efficiency. And the geological formations where CO2 can be reliably sequestered without leakage is often located very far away from businesses and factories, and CO2 is a gas and thus also expensive to transport and store.

Lastly, thermal storage is being researched as a means of storing excess renewable electricity produced during periods of high generation, such as solar at noon. The challenge lies in finding a low-cost storage medium with fantastic insulation that can keep the heat hot enough over hours and days.

The recovery of heat from storage and its transportation to the factory and into the target material that requires the heating is also difficult, especially for high-temperature applications where steam cannot be used. Finally, the complexity cost of retrofitting a thermal storage solution is another challenge.

No easy way to decarbonize industrial heat

So, there’s no silver bullet for decarbonizing commercial and industrial heat yet. But I’d like to end with a word of encouragement.

The market size and CO2 impact of decarbonizing heat easily matches what we’ve seen already with the solar, wind and electric car revolutions.

Heating is a massive, vital, and varied energy service for which there is no single catch-all decarbonizing solution.

We’ll need different innovations to decarbonize the many grades and applications of it – each of which will have the potential to become a new industry. There will be many winners here, so let’s get started.