Process heating is typically a carbon-intensive process. Some industry experts estimate that industrial heat accounts for around 9.4% of global carbon emissions — more than the emissions produced by all cars and planes combined.
While there is a growing conversation around decarbonization and carbon mitigation, strategies for decarbonization in industrial heating are sometimes not discussed, despite the sector’s environmental impact.
With the right strategies, it’s possible to reduce or even eliminate the emissions that industrial heating processes produce. Both emerging and well-established heating technologies can help heating engineers and consultants reduce a facility’s carbon footprint.
Where Does Process Heating Produce the Most Carbon?
Not all approaches to process heating are as environmentally impactful as each other — some are significantly more carbon-intensive than others.
Any system that generates heat at a facility likely produces carbon emissions. Fuel-based heating systems often contribute the most to a facility’s heating-related carbon emissions. The combustion of fossil fuels that powers these systems naturally produces emissions of greenhouse gases like carbon dioxide, methane, and nitric oxides.
Many facilities also use particularly high-emission fossil fuels, meaning that they produce more emissions from burning fossil fuels than they would otherwise.
Natural gas, for example, accounted for 38% of fuel consumption in New Zealand and produced half of all fuel-related greenhouse gas emissions. Wood-derived fuel, by comparison, accounted for 23% of fuel consumption but produced just 1% of emissions.
Strategies for Reducing Process Heating Carbon Emissions
For process heating professionals wanting to reduce the carbon impact of a facility, there are two options available — either efficiency upgrades and retrofits, which will reduce emissions produced by existing systems, or the replacement of current systems with low-carbon-impact heating technology.
Efficiency upgrades may allow a process heating professional to both improve site heating and reduce carbon emissions.
Low NOx boilers, for example, can also be low-CO2 boilers, depending on the strategy that the manufacturer has used to reduce the boiler’s emissions of nitrogen oxides.
With the right upgrade — like a flue gas heat recovery system or a combustion optimization system — a facility’s boilers can be made more efficient and produce less carbon dioxide, in addition to producing less NOx than conventional boilers. Improving efficiency through the use of technology like site IoT or MaaS tools may also help businesses reduce a boiler’s carbon cost.
Simply replacing boilers can sometimes be an effective way to reduce heat-related carbon emissions. Tighter regulations have led to serious innovations in the boiler market, meaning many available boilers will be significantly more efficient — and less carbon-intensive — than older, existing boiler systems.
On-site carbon capture and storage systems can further reduce the amount of carbon that facilities produce by capturing CO2 and other greenhouse gases after they are produced by a heating system and before they are released into the atmosphere.
For example, wet scrubbers are popular air pollution control devices that use water or water-based solvents to absorb pollutants.
Taking Advantage of Low- or Zero-Carbon Heating Systems
In situations where full replacement of existing heating systems is possible — or in new facilities — process heating professionals may be able to take advantage of low-carbon heating solutions. These solutions naturally produce the least amount of emissions, or even none, depending on the solution.
Most researchers and authors on low-carbon heating focus on a handful of potential solutions:
- Biomass and biofuel
- Hydrogen fuel
- Electrical heating
Some consideration is usually also given to nuclear power — likely not feasible as an on-site heating solution — and to post-combustion carbon capture, use, and storage (CCUS). CCUS can allow facilities to capture and re-use carbon emissions in heating processes.
Biomass and Biofuel
Biomass is a broad term, covering multiple types of organic materials that can be processed and burned to generate heat. Common sources of biomass include construction waste, wood, and agricultural waste, crops, sewage, and manure. This biomass may be combusted directly or processed into biofuel. Most process heating applications of biomass use either wood biomass or liquid- and gas-based biofuel.
Wood boilers are an example of a heating system that can take advantage of biomass. Specialized fuel-based heating systems can use biofuel. Existing systems may also be able to use a mixture of petroleum heating oil and biofuel to enable the use of biofuels without changes to existing systems.
The inefficiency of biomass may make it impractical for some industrial applications. Biomass and biofuel are also not entirely clean. While burning biofuel likely won’t produce significant amounts of carbon, it will generate methane, which quickly dissipates in the atmosphere but is 25-times as potent a greenhouse gas as carbon dioxide.
Hydrogen is emerging as a zero-carbon fuel source and an alternative to fossil fuels. Fuel cells containing a mixture of hydrogen and other fuel sources, like nitrogen, have been suggested as a way to provide facilities with low- or zero-carbon on-site heating.
Right now, hydrogen fuel is likely both too expensive and too infrequently used to be practical. At the moment, most hydrogen is also produced by a process that requires the combustion of natural gas. Other zero-carbon methods of hydrogen production exist but are not widely used.
In the future, as hydrogen production and transportation technology evolves, however, it will likely become a valuable alternative to fossil fuels in industrial heating.
In some cases, businesses make the switch to electric process heating in order to reduce their carbon footprint. If the business’s facility relies on grid power, however, it’s likely that they are still relying on fossil fuels and generating carbon emissions, just indirectly.
In areas where there have been investments in renewable energy sources, electric heating may be a more effective solution. Also, the use of electric heating allows a facility to reduce its carbon emissions passively over time as local utilities replace fossil fuel-burning power plants with renewable energy.
How to Reduce Carbon Emissions in Process Heating
While industrial heating can generate significant carbon emissions, good practices and new technologies can help professionals reduce or eliminate the associated carbon costs.
Upgrades like boiler flue gas recirculation and CCUS systems can improve a site without requiring the replacement of facility equipment. Replacing equipment with greener technology — like new boilers or electric heating systems — can sometimes eliminate carbon costs altogether.