What exactly is a harvester?

Some people might have heard at some point from the harvester of John Deere Forestry: the Harvester 1270G. Some of them even took the chance to climb into the massive vehicle of 22 tons when it was exposed on the International Green Week in 2019. What exactly is the deal with this impressive machine ,- particularly in connection with vegetable oil fuel often mentioned with it?

Let’s start with the background: even for those who haven’t seen it live it’ll appear reasonable that an off-road vehicle of such weight and with a length of almost 8m [~26 feet] shows significant fuel consumption. Additionally, forest territories are very sensitive which is why fossil fuels can/should never be filled in on site. Not to mention the greenhouse gas emission caused by fossil fuels! Thus, there is the need of an efficient fuel with a considerabley high energy density and low ecologic impact. Given the experience that the Technology- and Funding Center (TFZ) in Straubing had already made with different tractors of the emission category IV operated with rapeseed oil fuel, the team of scientists and engineers decided to try this alternative to diesel also with the harvester.

In July 2017, the research and development project started under the leadership of the TFZ, the John Deere European Technology Innovation Center (ETIC), the Bavarian State Forests (Bayerische Staatsforsten) and the Donauwald Forest machineries (Donauwald Forstmaschinen). Up to that point, the harvester had been operated with diesel only,  but as already mentioned, apart from the emissions in sensitive areas, the refueling process outside the forest implies an enormous time-based expenditures.

Hence, the aim was to run the engine 100% on rapeseed oil, which required not only a changeover at the injection nozzles, but also the development of a software application for the engine control unit in order to optimally burn rapeseed oil fuel. In addition, of course, the exhaust after-treatment system had to be adapted to the new conditions, and the solidification range of the alternative fuel between 0 and - 10°C requires temperature control of all rapeseed oil-carrying lines, fuel filters and feed pumps considering the colder temperatures in forests. This challenge was soon solved with a frost-proof, mobile tank system, which can also be used in the forest and is supplied by the auxiliary heating.
The delivery including the intermediate storage for the vegetable oil was carried out during the entire test period by the oil mill Mara Pflanzenöle GmbH & Co. KG (Marktzeuln, Upper Franconia), which was a particular challenge especially when the wood harvester was relocated. Thanks to the organizational skills of MARA and the smooth cooperation with nearby farmers though, this was also carried out without any problems.

At the end of December 2018 the first meaningful statements could finally be made:

Considering the temperature sensitivity of rapeseed oil, the expected change in performance delivery was in the starting behavior, especially in the colder months. With a rating scale of bad over medium to good, the starting behavior in winter was rated between bad and medium, which, however, can partly be explained by the fact that the auxiliary heating system did not start up and failed completely on one occasion. With regard to productivity, however, no significant differences in performance were found between the two engines, nor between the specific volumetric and energetic consumption of diesel and rapeseed oil.
A further test criteria is the quality of the engine oil after a certain period of use (present analyses were collected after 500 operating hours). However, the results of the tests were satisfying in every respect, as the vegetable oil content in the engine oil was always below 3% during the tests and the content of wear parts also always remained at a very low level. The ratio between the acid and base number did not show any excessive acidity of the engine oil, because even after 500 operating hours, there was still an abundant alkaline reserve.
After a total of 3,500 operating hours, of which 2,100 were absolved with rapeseed oil, the engine, exhaust filter and low-pressure fuel system were inspected. To the satisfaction of the research team, no complaints in the form of excessive wear, blockages, cracks or deposits were found.
The harvester operated with rapeseed oil has also always been exemplary in terms of emission behavior, complying with the limit values (nitrogen oxides, carbon monoxide and hydrocarbons).

In summary, it can be stated that the use of the wood harvester with vegetable oil is technically possible - even at temperatures as low as -17 °C - through appropriate conversion. In terms of both productivity and engine efficiency, there is no difference to the operation with diesel fuel. Not only does the emission behavior comply with the exhaust gas stage IV, but over a period of about 1.5 years it was possible to avoid about 120,000 kg of greenhouse gas emissions and the handling of about 41,000 l of diesel fuel into the forest. This corresponds to a greenhouse gas reduction of up to 87.5 % compared to fossil fuel due to the rapeseed oil fuel produced in a decentral oil mill in Bavaria.
The only challenge that needs to be overcome, however, is the adaptation of fuel logistics and storage - especially when relocating, since the operation of diesel can be accomplished more flexibly due to the established infrastructure. Thus, it absolutely depends on upcoming political movements whether they will soon give cause and motivation to produce and use a reliable, renewable and low-emission fuel in a natural way.

In this respect, the Branchenplattform, together with the TFZ under Dr. Edgar Remmele, Dr. Peter Emberger and Dr. Klaus Thuneke, as well as with its partners with shared interests, is increasingly advocating tax relief for vegetable oil, especially in agriculture and forestry, beyond the end of 2020.

More information to be found on: https://www.tfz.bayern.de/en/056073/index.php