TractorsA bridge to the battery

To reduce CO2 emis­sions from agri­cul­tural machinery, there are several possible approaches using alter­na­tive drive tech­nolo­gies. But all of them come with advan­tages as well as disad­van­tages. Func­tioning tech­nology is already avail­able for trac­tors adapted to use biofuels.

Although farm machinery accounts for a compar­a­tively small propor­tion (just 6m tonnes) of total carbon dioxide emis­sions from agri­cul­ture (66m tonnes), we still need to say goodbye to diesel fuels as quickly as possible in order to contribute more to climate protec­tion.

Unques­tion­ably, fossil fuels offer the highest possible energy density that we can use on a tractor. Yet, despite the latest advanced engine tech­nolo­gies, these fuels have the highest CO2 emis­sions compared to other types of propul­sion. For example, a signif­i­cant reduc­tion in emis­sions could be achieved by using hydrogen, methane, rape­seed oil or fully elec­tric motors.

However, this posi­tive result is often offset by signif­i­cantly lower energy density. This means that either the fuel tank or the battery must be signif­i­cantly larger, or the working time of the tractor, at high loads, is so short that it is not suit­able for use as an alter­na­tive to tradi­tional machines.

Possi­bil­i­ties and limits of alter­na­tive drive systems for trac­tors

A compar­ison of different drive types for trac­tors shows that diesel has the highest energy density but produces the most CO2 emis­sions. Although alter­na­tive fuels like methane, hydrogen or elec­tricity can signif­i­cantly reduce CO2 emis­sions, they have a low energy density, and there­fore are not yet suit­able for powering large trac­tors. A good compro­mise is the use of rape­seed oil as fuel.

Elec­tric propul­sion is a goal worth striving for

An elec­tric drive would provide high flex­i­bility, lower weight, and a smaller instal­la­tion space, in rela­tion to the power produced – if we only look at the motor. On the other hand, the batteries them­selves are still far too heavy and too low in power to be suit­able for wide­spread use. However, battery tech­nology is expected to make great strides over the next few years.

Biofuels repre­sent a promising bridging tech­nology that is avail­able to use today. In partic­ular, rape­seed oil presents a good alter­na­tive, in rela­tion to diesel, as it offers 93% energy density, and emis­sions savings of 91% (with decen­tralised gener­a­tion and consump­tion).

Battery-powered large trac­tors are still very heavy due to the batteries’ low energy density, and there­fore are still not suit­able for prac­tical field use.

Rape­seed oil is a sustain­able solu­tion

Rape­seed is grown on many farms. There­fore, the oil extracted from it is readily avail­able to many agri­cul­tural compa­nies. Rape­seed cake, a by-product of cold pressing, has a high protein content and is there­fore valu­able animal feed. A posi­tive side effect is that the rape­seed cake can partially replace imported soyabeans – with all their nega­tive side effects, from cultivation to trans­port and other costs.

In this respect, rape­seed repre­sents an extremely sustain­able solu­tion, provided that the quan­tity produced covers the farm’s own needs. This is because it only partially competes with food produc­tion. This fuel coun­ters the often crit­ical ques­tion of “tank or plate” with the answer “tank and plate”.

The multi-fuel tractor can work with diesel, biodiesel, chem­i­cally unmod­i­fied P100 vegetable oils and hydro­genated vegetable oils (HVO).

Multi-fuel tractor project

Prof. Peter Pickel is the Future Tech­nolo­gies Manager at John Deere’s Euro­pean Tech­nology Inno­va­tion Centre in Kaiser­slautern.

However, in order to be able to use rape­seed oil and other biofuels, the machines must be adjusted. The drive system of a tractor has to be modi­fied, in terms of engine perfor­mance, exhaust gas treat­ment, engine lubri­ca­tion, and starting behavior in cold weather.

At John Deere, we have addressed this chal­lenge with our multi-fuel tractor project. It can work with diesel, biodiesel, chem­i­cally unmod­i­fied P100 vegetable oils and hydro­genated vegetable oils (HVO). Mixtures of those biofuels can also be used.

Thanks to the installed sensors, the system auto­mat­i­cally recog­nises the fuel being used. In inten­sive tests – including in co-oper­a­tion with the Tech­nical Univer­sity of Kaiser­slautern – we were able to prove that the engine works without any perfor­mance impair­ments or addi­tional fuel consump­tion. In addi­tion, the engine complies with the applic­able emis­sions restric­tions – Level V for mobile working machines.