Ponnapat is originally from Thailand and studied Industrial Engineering at KU Leuven, specialising in Chemical Engineering. After his master’s degree, he completed a postgraduate programme in Innovation Management. In 2020, he joined the group of Prof. Karel Van Acker as a research assistant. Ponnapat later completed my PhD on the environmental and economic assessment of steel slag mineral carbonation and now continue this work as a postdoctoral researcher.
What is the problem with steel slags and why do you need to carbonate them?
Steel slags are by-products of steel production. In many countries, they are still landfilled, which can lead to heavy metal leaching. Carbonation offers a way to valorise these materials. It forms a stable carbonate layer on the slag surface, reducing the risk of leaching.
Carbonated slags are already used in concrete, but during my PhD I explored their potential in agriculture. Turns out, carbonated slags can provide nutrients such as phosphorus and act as a liming agent to regulate soil pH. This creates an opportunity to replace part of conventional fertilisers while safely reusing an industrial by-product.
What does your typical work day look like?
I mainly work on Life Cycle Assessment (LCA) and Techno-Economic Assessment (TEA). In simple terms, I try to answer two questions: Is this technology sustainable? and Will anyone actually be able to afford it?
We start by working with technology developers to understand the process and map it out step by step. Then we build models, calculate material and energy flows, and connect everything to environmental and economic databases.
Sometimes the data we need does not exist yet. In that case, we become a bit like detectives, collecting information from different sources and building our own models. In the end, our goal is to identify the hotspots and show where the biggest environmental impacts and costs come from, and how they can be reduced.
What are the main findings of your work on steel slag carbonation?
Carbonation is interesting because it stabilises the slag while also capturing CO₂, making it a form of CCUS technology. However, the process eventually reaches a point where additional carbonation becomes inefficient. The longer you carbonate the slag, the more CO₂ you capture, but the more energy you consume.
My work focused on identifying that sweet spot. By combining environmental and economic modelling, I found the optimal balance between CO₂ capture, energy use, and cost. For one of the systems we studied, that point was around 33 hours of carbonation.
As an LCA/TEA researcher, what advice would you give to technology developers?
Start early! LCA and TEA are most valuable when they are integrated into technology development from the beginning. They help identify hotspots and guide design decisions while there is still flexibility to improve the process.
The goal is not simply to evaluate a technology, but to help make it more sustainable and economically viable.
Is the social dimension also included in sustainability assessments?
Yes, we are now starting to include it. Through Social Life Cycle Assessment, we can evaluate risks such as unfair wages, child labour, workplace accidents, and gender inequality across supply chains.
What makes this work interesting is that numbers alone are not enough. Results need to be interpreted together with stakeholders and local context. Sustainability assessment is therefore as much about collaboration as it is about data.
How would you describe yourself as a researcher: environmentalist, modeller, or programmer?
Neither! I am a chemical engineer. I spend a lot of time working with models and data, but I would not call myself a programmer. Most of my automation happens in Excel 😊
Do you ever use decision-making tools from your research in your personal life?
No, in my personal life, I am spontaneous and prefer to go with the flow!
