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Farming in the post-diesel era

Diesel for agriculture remains cheap, but in the low-carbon era it won't last forever. Colin Stewart talks to experts about some sustainable replacements.

The pressure we all experience to cut carbon emissions at home, in the workplace and on the road is no less urgent in agriculture. Once, during a country drive, I wondered how big machines digging elds or harvesting crops would work when the oil ran out, and what we'd do for food when they did. Concerns about climate change have instead brought laws aimed at cutting carbon emissions to full international obligations such as the Kyoto Protocol. Mr Campbell, Team Leader, Environment & Design at SAC Consulting, part of the college explains. 

There are already options available to replace fossil fuels, but incentives to switch are limited by the current tax regime, according to Jim Campbell of SRUC, Scotland's rural College. Agricultural vehicles use rebated' red diesel, so they incur much less fuel duty than road vehicles, and savings from using alternative fuels are limited. 

Most of the technologies are already out there but have yet to be adopted because in most cases they do not add up nancially. 

Of course farms are already producing and using renewable energy on a large and growing scale and a substantial body of expertise has developed in the sector. We're at the start of a big switch to sustainable energy to drive farm machinery according to Will Watts, a director of RAW Energy, which consults on and develops renewable energy assets. But, he says, there's a long way to go. 

Recently in New Zealand we saw farmers herding sheep on Ubco E-bikes and quad-bikes. The move to electricity for a 250,000 combine harvester will take longer, but the Tesla Semi EV truck launch in November shows electricity works for larger machinery as it does for EVs, where the take-up has surprised many.

For Mr Watts, whose company is based at the Farm491 agritech and innovation centre at royal Agricultural University, Cirencester, a turning point came on the day last year when more than half Britain's energy was generated from renewable sources, coinciding with the longer-term adoption of smart-grid technologies. Britain is blessed with great conditions for on and oshore wind energy production and continued innovation in storage makes electric steadily more attractive. 

While range anxiety aecting EV cars is not a problem for farmers, long re-charge waiting times will be, especially in intensive periods such as harvest. 

Biodiesel and biomethane are very eective fossil fuel replacements as they work in existing vehicles with little or no modication, but their suitability will depend on the crop types produced, legal limitations on fuel crops and whether biomethane is available from anaerobic digestion assets on a property. Ultimately fuel will be viewed by government and others on how it integrates into sustainable farming, alongside other factors such as food production, carbon budget, soil management and resource preservation.

How innovation is powering change in farm machinery

Biodiesel

This is generally produced from oilseed rape, which is grown across the UK. It can be used as a direct substitute for mineral diesel or mixed as a blend. Some engine manufacturers are reluctant to provide engine warranties where higher proportions of biodiesel are used a procedure that can also make it harder for catalytic converters to achieve emission targets. 

Electric vehicles

Since many farmers also own renewable energy assets there is some interest in this. Disadvantages include re-charge time - in a busy harvest, hooking up for several hours is a major consideration. As battery technology improves and re-charge times reduce, electric will become a real option, though it would require a major commitment to change from diesel. Trailed and mounted equipment could also go electric, with power transferred from tractor by cable rather than to shafts and hydraulic lines. John Deere, among others, has a prototype. For smaller vehicles see Ubco www.ubcobikes.com. 

Biogas 

Aimed at farmers with their own AD plant, Valtra oers dual-fuel' tractors that will run on either diesel or biogas or a mixture of the two. They operate on biogas as they do on diesel (possibly at slightly reduced power) so introducing them into a eet is straightforward. New Holland also has a biogas prototype. 

Hydrogen

The most abundant element in the universe remains problematic to produce commercially. Steam reforming' is cheap but produces large amounts of greenhouse gases. Hydrolysis is intensive and costly. However, there's a worldwide rush to produce this gas cleanly, and any breakthrough will interest farmers with renewable assets or resources and no access to the grid to export electricity. While hydrogen must be compressed to a high pressure for road-going vehicles, farm tractors operating close to base could be refuelled regularly. Hydrogen can also be used in a converted internal combustion engine on a vehicle tted with a high-pressure tank. New Holland has a tractor powered by a fuel cell running on hydrogen