The science behind the world’s fastest way to measure a biofuel’s true heating value

Have you ever wondered about the scientific work which lies behind a new break-through technology? How you marry advanced technologies like quantitative dual energy X-ray absorptiometry (qDXA) and X-ray fluorescence spectroscopy (XRF) with something as mundane as biofuel? Here’s the in-depth story for all of you science nerds!

Ralf J.O. Torgrip, Principal Scientific Officer

In January 2017, Mantex’ Principal Scientific Officer, Associate Professor Ralf J.O. Torgrip, together with his colleague Víctor Fernández-Cano, published the world’s first peer-reviewed paper on how to use X-rays to measure heating value (as received, LHH) , moisture and ash content in organic materials.

We sat down with Ralf to talk about the science behind Mantex latest product, the Biofuel Analyzer.

So Ralf, how did you get started in X-rays?

It began with me reading a list of Sweden’s most innovative companies in a technical magazine. Mantex was listed as having invented a new technology for measuring physical properties in organic material using X-rays. Since I had worked with, and helped develop, all sorts of industrial measuring technologies, I immediately became interested. The most advanced method at the time was near-infrared (NIR), where you use infra-red light to measure moisture levels on the surface of a material. As it turned out, NIR is quite sensitive to environmental factors and had the problem of being a surface-only measuring technique.

It’s almost magic! – Ralf J.O. Torgrip

So in 2011 I became Mantex’ Principal Scientist and I immediately joined the process to commercialize the technology. With over 25 years of experience of industrial measurement applications, and experience from over 20 different measuring technologies, it was obvious to me that there was an interesting opportunity in this new imaging X-ray technology.

When did you begin to realize that you were on to something significant?

Wood chips is one of the most common biofuels, but many other types of biofuel are also used.

One of the initial challenges was that we wanted to measure all types of biomaterials, not just standard wood chips. To further improve Mantex qDXA technology to measure more heterogeneous bio materials, and to even better handle the background interference, as this really starts to mess with the interesting part of the signal, we decided to add more input.

The solution lay in sensor fusion! By adding X-ray fluorescence spectroscopy (XRF) sensors, we were able to develop a method where we can compensate for background interference and get high-quality qDXA information. The XRF addition also enables us to measure more complex materials, with more complex structures – like biofuels.

Give us a brief (!) explanation on how it actually works!

One of the most common uses of X-ray technology is probably at airports.

It’s almost magic, he he! I like to say that we work on the atomic level, because that’s really what we’re interested in. By counting the number of atoms, i.e. the electron density, in a sample, we’re able to do all sorts of interesting calculations, where the most important one is measuring the effective atomic number.

One of the most familiar uses of X-ray technology is probably at airports.

For example, we all know that when something burns, carbon dioxide (CO2) is created. We also know that there is a relation between a biofuel’s energy content, and the quantity of carbon (C) and oxygen (O) it contains. So if we know the amount of oxygen and carbon, or their ratio, we can calculate the amount of energy the fuel will produce when we burn it – the heating value. And basically, that’s exactly what we do!

Interestingly enough, the qDXA X-ray technology we use, is very similar to the X-ray machines you encounter at airports. But, whereas airport personell visually inspect the generated images looking for contraband, we are more interested in the raw image data.

What are the biggest hurdles in moving from scientific theory to an actual product?

It’s almost always a long journey to take an advanced innovation, which works well in the lab, and turn it into a commercial product. And there are many challenges to solve on the way.

One issue is the how you scale a technology, from the very small samples we are used to in the lab, typically grams, to the large quantities of material used in industrial applications, where we look at kilos or even metric tons.

Purity is another concern. As you develop tools like the Biofuel Analyzer, you initially work with somewhat idealized materials, which are quite clean. However, the real world is anything but!

Reliability is also very important. It takes a long time to get a sensitive instrument, which works quite well in a lab environment, to function reliably in a harsh industrial setting.

What can users, such as bioenergy power plants, expect from this new technology?

The Biofuel Analyzer allows biofuel power plants, like the new Fortum plant in Stockholm, to make on-the-spot decisions about fuel quality. Photo by Holger Ellgaard.

Right now this is probably the fastest and easiest way to measure a biofuel’s heating value. And speed is especially important since it makes it easy to take multiple measurements for on-the-spot decisions, whether it be fuel payments, fuel mixing or some other important aspect of running a bioenergy power plant.

Today, the most commonly used method for heating value determination is bomb calorimetry. It’s very accurate but it can take up to a day or two to process just one tiny sample, weighing a gram or two. The Biofuel Analyzer uses a sample size of 1.5 – 2 kilograms and takes just 60 seconds. It’s a true paradigm shift in this type of measurement technology.

Are there any other advantages?

I think the biggest advantage is that you can now sample large shipments more accurately, such as those arriving on a truck, a boat or on a train. Somewhat contrary to popular belief, there can actually be huge variations within a single biofuel shipment, and you ideally want to be able to test the biofuel’s quality quickly. For this to work in practice, measurements have to be fast and the instrument has to be easy to operate.

Where do you see the Biofuel Scanner going in the future?

We’re currently working on ideas on how we can make heating value measurements even faster. We want to notch it up from manual sampling, to real-time conveyor belt speeds similar to the Flow Scanner, which is our well-established product to measure wood chip moisture content in real-time at pulp mills.

In fact, we currently have a EU-funded (Horizon 2020) project geared at the measurement of all types of commonly used biofuels at any mass-flow rate. The results look very promising.

What are you working on right now?

The new Biofuel Analyzer (prototype).

Right now I’m working on an image analysis which will allow us to automatically measure a fuel’s size distribution. This is important information to our customers since it affects such things as the combustion speed of the fuel. Size distribution will also enable an automated classification of biofuel quality levels – an important factor when you have to put a monetary value on biofuel.

It’s funny, because in this application we are actually somewhat similar to the security guys at the airport – studying X-ray images and trying to interpret what we see. But of course we want to develop a robust and automated solution.

What advice do you have for the PhDs out there who want to know more?

Go read the paper! It’s called Rapid X-ray based determination of moisture-, ash content and heating value of three biofuel assortments and you’ll find it in the Downloads section at

Thanks for your time Ralf!