What is to come after diesel?
The intention is to also use fossil diesel fuel less in the agricultural sector. All of the alternatives have limitations of one form or another: traditional biofuels are politically no longer desirable. Biomethane or electric motors powered by batteries are hampered by their capacity limits. No overarching solution is in sight.
Didn't there used to be a drive type called a 'diesel engine'? What was still the figurehead of Germany's automotive industry just a few years ago now accounts for less than 30% of new registrations. Sales of electric and hybrid cars are soaring, although their numbers are still far lower in absolute terms. More important by far, however, is the fact that investment in diesel technology for cars has all but dried up. According to the will of even major manufacturers, it is to be phased out in 2035.
However, the diesel engine will not be consigned to the scrap heap of history any time soon in tractors, at least in the larger ones. Its performance characteristics are simply too good for that, and the alternatives are not sufficiently mature. In addition, fossil diesel is still simply too cheap. However, that could change, because diesel engines account for two thirds of agriculture's energy-related emissions. This value has to be reduced. Essentially, this can be accomplished using biofuels in 'normal' diesel engines, by means of process technology improvements for avoiding CO2 ('saving fuel') and using alternative drives.
Biofuels are the most obvious method for avoiding the combustion of fossil raw materials, and also the one that has been tried out for the longest. However, theirs is a tale of woe, because the agricultural use of rapeseed oil or biodiesel is not primarily a question of technology but of politics. Technical solutions for rapeseed oil or pure rapeseed methyl ester (B-100) have been around for decades and also function in more modern engines. The products are standardised, do not have to be imported, are easy to store and use in refuelling and are not classified as hazardous substances. However, their raw materials can also be used as foods. Since the 'tank or plate discussion' almost 15 years ago, the production of fuel from cultivated biomass has had a political problem. Nitrous oxide, which is harmful to the environment, is also released as a result of fertilisation during production, thus relativising the advantages.
At the same time, the relative prices of agricultural diesel, biodiesel and rapeseed oil fuel are blurred. On the one hand, politicians want to replace fossil diesel but, on the other hand, they are funding it by means of rebates. Conversely, the tax breaks for the no longer desirable first generation of biofuels are being rolled over from year to year and are (due) to stop at the end of 2021. Two developments could eliminate this blockade. On the one hand, used greases, liquid manure or straw could replace rapeseed, maize or palm oil. On the other hand, a high CO2 price component for fossil diesel would help the alternatives.
The second method is not to replace diesel fuel but to reduce its consumption. Fuel economy is also immediately apparent to farmers; there is no need to use the overarching challenge of climate change. However, this cannot be limited solely to tractors, because CO2 arises in a number of different work processes. Major improvements have already been achieved since the 1990s, mainly as a result of combining tillage and sowing as well as thanks to the use of compact disc harrows. However, there appears to be hardly any scope for further improvement. Quite the opposite: the replacement of glyphosate with mechanical tillage and the renewed increase in the use of ploughs actually represent a step back in climate terms. In connection with process technology, hopes are now being pinned on the continued development of automated processes, which the industry estimates could save up to 15% fuel and therefore reduce CO2 emissions.
The alternative drives remain as the third method. There are essentially two options for this. One is based on modified combustion engines that are powered with methane or (when they become more attractive) synthetic fuels. The other is based on electric motors powered with batteries, directly supplied current or fuel cells. 'Tractor studies' have been on show at various Agritechnica trade fairs for years, but no clear direction is apparent.
Long since communicated, it is claimed that the biomethane tractor from New Holland will actually go on sale in 2021 as what is likely to be the first 'alternative tractor'. The six-cylinder vehicle with 180 hp is immediately recognisable by its gas tanks. Pure methane is injected into its spark-ignition engine's combustion chamber. It is referred to as CNG or compressed natural gas. One potential source of this is biogas, whose 25% CO2 content is separated off. The reason being that fossil natural gas would not offer any progress compared to fossil diesel. Essentially, methane can also be liquefied (LNG, or liquid natural gas). This technology is increasingly being seen in heavy-duty trucks, and is opening up new perspectives for biogas plants. However, this complex liquefaction is hardly worth considering for farms. The disadvantage of CNG is that its energy capacity is only around half that of diesel, resulting in less range and comparatively large tanks.
John Deere has presented a concept study that obtains its power via cables. What appears somewhat bizarre at first glance may perhaps be a viable option for consolidated farms with large fields after all. However, these are more likely to be found in the USA or Russia than in Western Europe. In smaller-scale regions, fuel cells would be a possibility for operating high-powered electric motors. The truck sector is already relatively close to a practical solution. However, handling hydrogen is no trivial matter, and the technology is expensive. Some twelve years ago, an experimental tractor was developed (by New Holland), but this approach was abandoned again in favour of methane tractors.
John Deere has presented a concept study that obtains its power via cables. What appears somewhat bizarre at first glance may perhaps be a viable option for consolidated farms with large fields after all. However, these are more likely to be found in the USA or Russia than in Western Europe. In smaller-scale regions, fuel cells would be a possibility for operating high-powered electric motors. The truck sector is already relatively close to a practical solution. However, handling hydrogen is no trivial matter, and the technology is expensive. Some twelve years ago, an experimental tractor was developed (by New Holland), but this approach was abandoned again in favour of methane tractors.
Conclusion: As long as it is permitted and the CO2 charges remain low, tractors will continue to be operated using fossil diesel. At best, the likelihood of saving fuel by means of production processes and therefore reducing emissions could involve the increased automation of operations, because humans are taken out of the equation as the weakest link. In view of the tank or plate debate, biofuel is only an option when it is manufactured from non-foods. That leaves methane from biogas plants or electricity from batteries. Tractors are already operating with these, but such alternative drives are still a long way off from achieving any kind of breakthrough.
Thomas Preuße, DLG-Mitteilungen