Is 'green' fuel clogging up our machines?

For, just as the industry has been calling on government to give the arable side a much-needed shot in the arm by introducing a policy to enforce greater use of bio-fuels across all transport sectors, we’ve been blaming an increase in the biofuel element in the red diesel used in our tractors and combines for clogging up their filters and bringing them to a gasping halt.

Responding to the desperately poor prices circulating in the marketplace – with grain being bought for the sort of figures last seen back in the 1980s in a market which simply doesn’t seem to have a bottom – NFU Scotland last week proposed this solution: “One potential use for some of that grain is biofuels. The farming unions agree that the UK Government must increase the amount of bioethanol in petrol sold in the UK.”

Unlike many other countries, the normal inclusion rate of bioethanol in UK petrol is just 5% rather than 10% or more (designated 'E10') in other parts of Europe and beyond. Without this sort of demand pushing the market along, the UK industry – which although it has two fairly major players in the market – has always been prone to seeing production plants mothballed at the drop of a hat, or more correctly in the price of oil.

“The UK Government needs to stop delaying and get on with the introduction of E10 petrol onto UK forecourts,” said the union, keen to drive the market along.

Meanwhile, it would appear that a lot of people are encountering the problems mentioned above with some form of contaminant, or bloom. This is apparently precipitated by the 'bio' part in red tractor diesel, leading to a marked increase in the requirements to change fuel filters.

While at £80 a pop to change a couple of filters, it’s a costly business – but even that might be a small consideration if your tractor comes to a wheezing halt or is shut down into 'limp' mode when you’re hauling a load of tatties along a major road during rush hour.

Okay, I think everyone is well aware that there’s a big difference between biodiesel and bioethanol, and no doubt in the effects which they have – but what lies at the bottom of the red diesel problem seems to be a bit of a mystery.

According to Jamie Smart, the NFUS’s go-to-guy for anything tractor or machinery related, the theory which is widely circulating in the industry hinges on two factors to do with recent inclusions of higher levels of bio-fuel in the diesel: “This has a double effect. Biofuel is hygroscopic – ie, it attracts water, which with the bio fuel itself can cause bacteria to grow in and on the fuel within the tank,” Jamie told me.

Put basically that’s: More bio fuel = more bacteria = problem 1.

The second problem is that the biofuel also tends to act as a solvent, loosening up the muck, rust and other stuff which might have built up over the years in our fuel tanks and fuel systems. “Lots of bacteria plus lots of accumulated muck being released = choked fuel filters.”

However, Jamie said that the sheer number of cases – including instances where people using new fully bunded tanks with filtration systems fitted encountering the same issues – seems to indicate that this might not be the whole answer and that there’s some other underlying problem as well. Discussions are still going on with the fuel supply trade to try to nail the cause.

While the complaint originally seemed to be confined to the Borders and the Lothians, machinery rings around the country which handle a lot of fuel sales have been trying to get more information from their members about the instances in which problems have been encountered to try to get a handle on the extent of the problem. And it does seem to be pretty widespread, with problems now being reported from most parts of the country.

For the technically inclined, the 'bio' fatty acid methyl esters (FAME) proportion added to refined diesel tends to come from sources such as used cooking oil and even rendered fat from knackery waste, which undergo transesterification with methanol.

I believe that the inclusion level of this constituent in these 'greener' fuels has been going up in stages, rising again earlier in the year and it’s this element which acts as the solvent in storage tanks, dissolving any residues which have been hanging around there for some time.

The product also has a greater propensity to absorb water – and the fact that we’re now using ultra-low sulphur diesels, with less sulphur which, while it might be considered a pollutant, acted to stop any bacterial or algal growth in diesel – and so a fairly good growth medium for any bugs hanging about in the tank has been created.

Water can be present either as free water, or as an emulsion of tiny suspended drops within the fuel and the presence of FAME can increase the level emulsion giving the bugs even more chance of breeding up, while free water can increase corrosion and the release of particles from containers.

Water can be absorbed as a contaminant during manufacture or at various stages in the handling process, through leaks or cracks in systems. The exposure of large surface areas of fuel to air with high water vapour content in storage tanks can also lead to substantial absorption of water into the fuel itself and can also lead to condensation on the sides of the tank.

Obviously, if tanks are being filled and emptied regularly, the fast turnover should, in theory, stop any problem, building up – always provided things were reasonably clean in the first place.

But the recent-ish requirement to change over to bunded tanks would, you might have thought, reduced the likelihood of any substantial build up of the sort of stuff which used to slosh about the bottom of the tank in years gone by.

In the majority of cases, newer storage tanks will also be fitted with filters which remove both water and filter-clogging contaminants before they get into the tank of the tractor or the combine. While there might be a degree of logic lying behind this theory, it remains no more than that –and while it might explain the clogging of filters where simple fuel hygiene measures, like checking the tank for contaminants and cleaning it out occasionally, have been ignored, it’s impossible to discount the fairly large number of cases where problems have arisen even after everything’s been done properly.

I spoke to Jamie Baker, at the United Kingdom Petroleum Industry Association (UKPIA) earlier in the week and he said that his organisation was aware of the problems some people were having with agricultural vehicles having issues with their filters. “This is something the fuels sector is aware of and is actively investigating, without any firm conclusions on the cause of the issue,” he told me.

He stressed the importance of looking after storage tanks, but admitted that it didn’t seem to be the answer in every case and 'that enquiries were still on-going'.

Of course, there’s no getting away from the fact that the new high tier, environmentally compliant common rail engines are becoming much more fussy in what they can use. They also have the electronic systems to react by flashing up warnings and shutting down systems before there’s any real chance of anything actually starving the engine.

As you read this, I suspect there might also be an element of “oh, that happened to me too…” going on – and when somebody mentions something, it triggers suspicions in the minds of others and so this story can and probably will grow legs.

But, just as there’s no power without diesel, there’s no smoke without fire – and for the moment the source of the problem remains unresolved.