The 3 levers to decarbonize industries: their feasibilities and levels of efficiency


What do we talk about when we talk about decarbonizing industries? 

In a previous article on “green” investments and savings, we were addressing the importance of not overlooking the environmental impacts of big polluters (i.e industries and businesses), while too focusing on the carbon footprints of each individual. 

As 85% of global greenhouse gas (GHG) emissions are coming from transportation, industries, and energy, it is necessary that we move the focus of the discussion from individual carbon footprints to that of industries and businesses. 

three most carbon intensive industries: chemicals, cement and steel
Graph combined from the report of BPI France and The Shift Project

As can be seen from the graph, the chemicals, cement and steel industries account for 69% of all emissions from the industries sector. From here on, we call these industries “carbon-intensive industries”.

So, what are industries and what are their inputs and outputs in general? In the graph below, the centerfold of industries is their production activities. At the moment, the production model stays linear, in which the inputs are natural resources, energetic resources, humans, and machines in order to produce the outputs which are goods and services – while emitting unwanted side products such as industrial wastes and GHG emissions (which is 91% are CO2, and HFC, N2O and other gases as the rest).

linear industrial production process
Our current linear industrial production process

In these production activities, there are two types of emissions: combustion emissions (resulted from the heating of gases and raw materials, etc.) and process emissions(resulted from chemical transformation of raw materials, leaks of gases, etc.).

The exact proportion of these types of emissions varies throughout different industries. Below is a graph demonstrating the 2 types of emissions in the most carbon-intensive industries, in the case of France. 

breakdown of CO2 emissions between process and combustion emissions in France in 2018
Breakdown of CO2 emissions between process and combustion emissions in France in 2018. (Source). 

As seen in the graph above, industries such as steel, non-ferrous metals, glass, and bricks require a large number of combustion emissions due to the high level of heat needed to melt, shape and mold these metals. 

Meanwhile, industries such as cement and lime emit a larger amount of process emissions. In the case of the lime industry, this is due to the release of CO2 trapped in limestone in order to obtain lime as the final product.

The process of making lime
The process of making lime. As noted in the graph: these “process” CO2 emissions account for nearly 2/3 of lime’s total CO2 emissions (Source)

Therefore, depending on different industries and production activities, we either aim at reducing combustion emissions or process emissions. In the next part of the article, we would examine the 3 most discussed levels to decarbonize carbon-intensive industries, namely: decarbonized energy mix, waste heat recovery and electrification, and carbon capture and hydrogen production process.

At the same time, we cannot stress enough the necessity of looking at the whole system and proposing systemic solutions, because as we know it, there is no one single magic solution that can help us drastically reduce the emissions from our carbon-intensive industries.

3 levers to decarbonize industries: the feasibilities and levels of efficiency

Lever 1: Phase out fossil fuels and opt for a decarbonised energy mix

The energy mix is a problem that needs to be solved on a country level, due to the specifications of each country’s geography, geographical and natural advantages as well as the maturity of decarbonized energy technologies. 

We explained these dynamics in previous articles – examining the pros and cons of the most popular energy sources of our times (coal, oil, natural gas, nuclear power, hydropower, wind & solar power) as well as the lesser-known ones (biomass, biogas, syngas, biomethane, geothermal, solar thermal). We invite you to give them a look in order to have a detailed view of the matter.

In the analysis “The World’s Projected Energy Mix, 2018-2040” from Visual Capitalist, the author resumed the global projected energy mix between 2018 and 2040, based on stated policies scenario (i.g: existing public policy frameworks and announced policy intentions) in the graphic below:

The World’s projected energy mix, 2018-2040
The World’s projected energy mix, 2018-2040 (Source)

The most interesting thing drawn from this graphic is that there is no proper“energy transition”, one that industries, businesses and their Big4 consultants are eagerly propagandizing. We are definitely not phasing out fossil fuels to replace them with decarbonized energy. We are simply continuing to increase the production of all sorts of energy to meet up with increasing demands of production.

Lever 2: Reduce waste heat and electrification for industrial heating

While 66% of the energy used by industry is to produce heat, only up to 40% of produced heat is directly used (and 60% of them is lost during the process). The question of how to harness this huge amount of industrial waste heat, thus, is a puzzling yet interesting one. 

heat loss in furnace
Around 20% to 40% of heat is actually useful. In any furnace, heat loss will happen. (Source)

In this research “Waste heat recovery technologies and applications”, researchers at the Brunel University London presented 19 different methodologies and state of the art technologies used for industrial waste heat recovery, with concrete examples in the steel and iron industries, food industry and ceramic industry. Below is an example of one Waste Heat Recovery system – the heat recovery steam generator (HRSG)

the heat recovery steam generator
“The heat recovery steam generator (HRSG) is a complex system used to recover the waste heat from the exhaust of a power generation plant. It consists of several heat recovery sections such as an evaporator, superheater, economizer, and steam drum (for converting water to steam), which are very large in size. […] It is reported that with the use of HRSG for steam production, a system efficiency of as high as 75–85% can be achieved” (Source)

On the other hand, at the moment, only 18% of the electricity used by industry is used to produce heat, the rest is still fossil fuels-based. In a previous article, we discussed the absurdity of producing electricity (high-level energy) to produce heat (low-level energy) on a household level. On an industrial level, if electricity is produced by decarbonized method (i.e nuclear), it might be interesting to replace the burning of fossil fuels with electricity for industrial heating?

half of the fuel consumed for energy can be electrified with technology available today
According to McKinsey, “Almost half of the fuel consumed for energy can be electrified with technology available today”, up to high-temperature heat of below 1000°C.” Yet, in the same report, it is said that “electric furnaces for industrial heat demand up to approximately 1,000°C are technologically feasible but are not yet commercially available for all applications.”. So I guess there is only 18% + 15% = 33% fuel consumed for energy that can actually be electrified at the moment of the writing. (Source)

Moving away from electricity, solar furnace can also be an interesting alternative, who allows heating up to 3500°C. We have addressed this technology in our previous article called “Lesser-known renewables”, which we invite you to take a look to learn the details of this technology.

solar furnace france
The solar furnace in Pyrénées-Orientales, France (Source)

Level 3: New technologies such as carbon capture & storage and utilization of hydrogen

“Carbon capture and storage” is yet another most hyped notion in recent years. Even Elon Musk set out a prize of $100 million dollars to seek the best carbon capture technology that can pump out 1000 tons of CO2 per year.

Elon Musk $100M carbon capture tree meme
Just saying

The graph below explains the main mechanism of Carbon capture, utilization and storage (CCUS), which could be mainly used to capture combustion emissions:

carbon capture process
Carbon capture, utilization and storage: CO2 emissions are “captured” when being emitted from factories, compressed to be transported to the storage site, and then permanently stored underground. (Source)

At the moment, there are 19 operational CCUS facilities worldwide, mainly in North America. In Europe, CCUS facilities are projected to be built in the North Sea area (with a heavy concentration of industrial areas and offshore storage).

Currently, the technology is not yet matured and therefore economically too expensive ($58.30 per metric ton of CO2) in comparison with the price of carbon offsets (varies widely from <$1 per ton to >$50 per ton). It is also worth noting that CCUS only works in specific contexts: when one can capture combustion emissions in highly concentrated areas and when there are storage sites nearby. It makes much less sense to capture a certain amount of CO2, put it on a boat run by fossil fuels to travel some thousand miles, and store it in some offshore sites.

CCUS indeed has a role in reducing the combustion emissions – in the Clean Technology Scenario of the International Energy Agency (IEA), CCUS technologies “contribute 13% of the cumulative emissions reductions needed to 2060”, which makes it “the third-largest contribution, behind energy efficiency (39%) and renewables (36%)”, while nuclear and fuel switching “account for 5% and 7% respectively.”

But what about process emissions? It depends on the production process of each industry. In the case of the steel industry, “green steel” is becoming the next big thing. “Green steel” itself means different things, according to different companies that develop the technologies. But in general, it is steel made with the lowest carbon footprint currently possible, for example, using hydrogen rather than coal.

In the graph below, you can compare the two ways of making steel, between the traditional “blast furnace route” but adjusted with CCUS technology and the “green steel”, through a process of hydrogen reduction. Both approaches have their limitations – as listed below – yet both are promising technologies in order to reduce emissions of the steel industry, an industry that will not cease to exist anytime soon.

Here’s a comparison of two chemical formulas of the two processes (for our geekiest readers)

direct reduced iron process
The DRI process (Direct reduced iron), which “has 35–40% lower CO­ emissions than conventional steelmaking” (Source)


Reducing emissions of the industrial production process – the process that is at the heart of our industrial activities – is a must to meet the Paris Agreement objectives. At the same time, other industrial activities that potentially bring more profound impacts should also be discussed and tackled. 

For example, the design of alternative industrial and business models that are less-energy and less resource-demanding (i.e circular economy and circular industrial models), or the design of economic and financial models that favour the growth of well-being of humans and other living things, instead of constant economic growth (i.e Economy for the common good)

energy efficiency, circular economy, digital transition, energy alternatives, CO2 capture and valorisation, economic and financial models
Areas in green boxes are ones that we believe could make profound and positive changes to the environmental shift, which are energey efficiency, energy alternatives, circular economy and economic and financial models. The graph is made from the original illustration of ALLICE (a French alliance dedicated to energy efficiency and decarbonization of industry) (Source)

We will write about these profound changes in terms of business, economic and financial models in the upcoming articles. Stay tuned!

*** A huge thanks to my colleagues Auriane Clostre & Anne Coroller at Stim who had given a wonderful presentation of these 3 levers in one of our internal Climate & Environment Meetups, which had inspired me to write this article to sum up their analysis and propositions 🙂

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