Mr Remmele, what are the greatest challenges when it comes to developing a tractor that runs on different fuels?
The goal of our project was to develop a tractor capable of working with biodiesel, rapeseed oil, and diesel. These fuels differ very significantly, in terms of their chemical and physical properties. It is therefore important that the fuels – or rather their mixing ratios – are clearly identified. This is the only way to avoid over- or under-performance. Of course, in addition to this, the emission limit values must be complied with under all operating conditions. And then there are the practical requirements: They must be able to cold start and fuel consumption has to be right.
What had to be modified, to meet these requirements?
First, there is the low-pressure fuel system for rapeseed oil, which has a significantly higher viscosity at lower temperatures, compared to diesel and biodiesel. The focus, however, was on modifying the engine control system: It has to store different characteristic diagrams for the different fuels or their mixtures. This is the only way to achieve performance and emission limits.
How does the tractor reliably recognise the fuels?
We chose a two-sided approach to achieve this: On the one hand, John Deere worked on detecting fuel with sensors already installed on the tractor. Our job was to then create a working solution, using sensors that are readily available on the market. All systems must work reliably, both at low temperatures and at very high temperatures. To test this out, we examined several metrics, like viscosity, density, and conductivity, and developed suitable models for them.
How does testing of such a new system work in practice?
We first examine a new machine on our tractor test stand. There, we take power from the power take-off (PTO) shaft. We also use an automated accelerator pedal adjuster. Thanks to this combination, we can request various speed-load cycles from the engine, from our control room. This we do with standardised cycles, which are required by law, to take measurements on the engine test bench. We can then use this to determine fuel consumption, performance curves, and emissions.
After 600 to 1,000 hours of operation, we then bring it back to our tractor test bench and measure how the fuel consumption, performance and, where applicable, emissions have changed.Dr Edgar Remmele
After this incoming inspection, the machine goes into practical field testing at our state test fields. The tractor performs all sorts of work that occurs throughout the year, like any other machine. After 600 to 1,000 hours of operation, we then bring it back to our tractor test bench and measure how the fuel consumption, performance and, where applicable, emissions have changed.
However, the legislators are already thinking ahead, in terms of Stage V Emission Standards, and want to know the emissions coming from machines in the field. That’s why we equipped ourselves with a portable emission measurement system (PEMS) several years ago, to be able to measure the Real Driving Emission (RDE) under actual operations.
In your opinion, what potential do multi-fuel solutions offer to agriculture?
Agriculture has been tasked with reducing greenhouse gas emissions, for example through the Climate Protection Act in Germany. Many greenhouse gas emissions in agriculture come from biogenic processes, which can hardly be reduced: Methane emissions from moorland and animal husbandry, or nitrous oxide emissions from nitrogen fertiliser.
On the other hand, what can easily be reduced are the so-called energy-related emissions, and two-thirds of these come from fuel use. And here I see the chance for biofuels to quickly make a significant contribution to reducing greenhouse gases in the agriculture sector.
The great charm of the multi-fuel solution is that it gives the farmer freedom of choice. In this way, they can counter high fuel price fluctuations by switching back and forth between different fuels – depending on which are currently available or least expensive.
Will biofuels create competition for land that is currently used for food production?
The most important message, from my point of view, is: There’s nothing on the table without something in the fuel tank. After all, we need fuel to produce food. I don’t really see any competition for land, either, because we produce a by-product, like rapemeal cake, when processing oilseeds, for example. This valuable protein feed can, for example, replace soya imports from South America if it were to be produced locally. In this way, we kill two birds with one stone.
What I want to emphasise: At the moment, almost all vegetable oil-based fuels go to the transport sector, and not to agriculture. We operate our cars with 7% biodiesel content. And we will not need biofuels for them in future, because the private transport segment is on its way to electrification. The quantities of biodiesel which will be released in the long term, due to no longer being used in the passenger car sector, would be enough to supply agriculture.