NI Branch Talk - CNHi Methane Tractor & on-farm biogas

Northern Ireland I Agr E Branch members and guests recently enjoyed presentations at AFBI Hillsborough on both the biogas production research there and the commercial development story of the world’s first methane powered tractor from New Holland. 

Dr Gary Lyons , AFBI described the features and performance of their Anaerobic Digestion plant. It was initially set up in 2008 to process slurry from the dairy herd and now includes the co-digestion of 7,000 cubic metres of slurry with 1,000 tonnes of grass silage each year.  Co-digesting 20 t of slurry with 1.5 t silage  doubled biogas production to 216kWh per tonne of input.                                                                                                 

Slurry is pumped from a reception pit to the 650 cubic metre insulated digester tank which is heated to 39 degrees C.  The process produces 600-1,000 cubic metres of biogas /day which is scrubbed through a carbon column to remove excess hydrogen sulphide before collection in a bulk gas-holder vessel. 

The gas is then used to fuel a 95kW CHP “Combined Heat and Power” electricity generator unit. The electricity is used on the site complex and heat from the engine’s cooling system is directed to maintain digester temperature and provide heat for the site’s buildings district heating system. A biogas boiler site is used to provide heat when the CHP is not operational. Records kept for the first 7 years of operation confirm that the AD plant used 43,000 tonnes of slurry, 1,400 tonnes of grass silage and 40 tonnes of concentrates to produce 1,200,000 cubic metres of biogas, 1,100,000 kWh of electricity (worth around £1 m in ROC payments and purchase offsets at present values),  3,600,000 kWh of heat and 43.000 tonnes of fibrous digestate. The latter is a valuable retained source of plant nutrients, for return to the land, with the advantages of the plant available N fraction being increased by around 20%  and a reduction in the slurry pathogenic organisms.

Operational updates to improve performance during that time have included the installation of a higher capacity macerator and small recirculating mixer to prevent fibre crusting. A recent plant overhaul involved sludge removal from the base of the digestion tanks and installation of a Landia Gas Mix system on the main digester. Output is now around 1,000 cubic metres / day.   

The plant’s main income is via the “ROC” (Renewable Obligation Certificates official scheme which encourages and rewards energy production from renewable sources) payments and is about 11 times greater than its costs of service and maintenance. However, there are additional costs of managing the feedstock and digestate, plant service, maintenance and waste management fees.    

Fortunately AFBI have a further 8.5 years to run on the ROC scheme and the plant is expected to maintain its reliable ongoing service-life for more than 10 years.

Potential future options for the AFBI plant include supplying electricity to the grid , supporting green hydrogen gas production, trading carbon credits or providing fuel for farm vehicles such as the methane powered tractor. To power a tractor the gas would need to be cleaned / concentrated to contain at least 83% methane and held at a specified pressure in a special storage tank. The AFBI example of 1000 cubic metres of biogas /day could produce, after on-site energy demands, 424 cubic metres of refined methane fuel to power the T6.108 tractor for 15 hours at maximum working capacity. There are also some commercially run AD plants in Northern Ireland now producing methane, from various sources of organic feedstock, which can be further refined and compressed for use as fuel for vehicle engines.   

Mr Brian Magee, Northern Ireland Area Sales Manager for Case New Holland (CNH) was joined by his colleague Mr George Mills  (based in SE England.) Their joint presentation described how their company’s commitment to its Clean Energy Leader Strategy has led to production of the world’s first 100 % methane powered tractor. This implements CNH’s policy of introducing their “energy-circle” concept where harvested field crops (and other farm “waste” products) feed an anaerobic digester to produce bio methane. When processed this subsequently powers the tractors used to do the field work, in establishing and harvesting the next crop, to provide the feedstock for continuing bio methane production fuelling the tractors again for the next crop. 

Development of the methane powered tractor  

From 2006 CNH started with biodiesel in the process of trying  alternative fuel options. A hydrogen fuel-cell powered tractor prototype was produced and tested in 2009. A methane-powered version of the popular T6 series tractor was first shown in 2013 at its Basildon development base where both the T6 and T7 New Holland tractor ranges are built for export to 120 countries. By 2017 the NH T6.180’s methane-powered version was chosen to start production, from 2022, as the world’s first commercially available methane-powered tractor.  Its engine is a re-engineered version of the current diesel 6.7 litre 6 cylinder FPT unit with a special cylinder head, to facilitate gas injection to the individual cylinders, and spark plug ignition. The air / fuel mixture is precisely controlled and there is an air to air turbo intercooler to increase efficiency. Drive-by engine noise is reduced by 5dBA which is a reduction of more than 50%. Noise in the cab is also reduced to under 70 dBA.

A cleaner exhaust

The exhaust gas passes through a maintenance-free 3- way catalyst without the need for exhaust gas recirculation or SCR treatment.  By comparison with the diesel version, exhaust pollution is further reduced :- particulates by 98% , non -methane hydrocarbons by 90%, carbon monoxide by 75%, carbon dioxide by 11% and nitrogen oxides by 62%. 

Engine power (145 / 175 hp boost) and Torque (740 Nm) is equivalent to that of the current T6.180 diesel version. At current fuel prices, running cost is reduced by up to 30%.

CNH Industrial is a sister company to the manufacturers of both FPT engines and IVECO trucks. Their methane powered HGVs are now in common use with long distance hauliers across Europe. FPT have more than 20 year’s experience of supplying around 50,000 natural gas engines to a range of world industries. 

On-farm testing

The methane powered T6.180 tractor has now been test-driven on farms across the UK (including N Ireland ) and in world markets. All the working features including transmission, hydraulics and pto are unchanged and, as expected, operators have reported their satisfaction in using it. The cab design and drivers’ visibility remains the same. 

Several saddle tanks (total capacity 183 litres) are mounted close to the chassis, in place of the original 230 litre diesel tank, and, to extend working range, there is an optional front mounted 270 litre tank. This also provides the equivalent of a 850 kg front ballast weight and it can be removed if the user wants to use front linkage implements or a fore loader.  

One of the sites for pre-production trials on a commercial farm was the farming / contract enterprise of Sell Farms at Vange in Essex just a few miles from the Basildon factory site. The range of machinery used there includes a 3500 g slurry tanker,  18t silage trailers, a 9m grass rake, a straw chopper, a forage diet-feed mixer, a fertiliser spreader and some cultivation implements. Examples of typical working times achieved from a full methane top-up included  around 4 hours on intensive loader work, 8 hours on trailer work and up to 11 hours powering a straw chopper. 

The most fuel efficient work with the methane tractor involved  low draught / top work at around 1500 rpm engine speed.

For continuous heavy cultivation work, away from the yard, the diesel version still has a range advantage being capable of working at full power without refuelling for more than 9 hours from a full 230 litre fuel tank.   

Fuel processing, storage and supply

Some customers, such as those in municipal work, can fuel their methane powered engines from the same mains natural gas stations used by HGVs.  Mobile specialist tankers can also fuel  customers’ vehicles on sites in more remote areas. For the farming sector, those with access to AD plants are now keen to know how the gas produced can be processed and stored economically for use in their own tractors. For this purpose, since 2021, New Holland have been working closely with UK based Bennamann Ltd and they now hold a minority stake in this company. It provides a specialist service of collecting and processing local fugitive methane for storage and subsequent transfer to a vehicle’s fuel tank. They can use their mobile “BioCycle” filtration and compression unit to process the output from a farm-based AD plant. The cleaned and liquefied methane is stored in their patented mobile “Inventer Tank” storage unit from which a methane tractor can be refuelled with 435 litres in 5 minutes. The single-nozzle NGV1 gun is the same as used to refuel gas-powered HGVs. An artic trailer-based mobile delivery service carrying similar tanks is now available in the UK and further developments here are likely.

A new era 

In terms of cleaning exhaust gas emissions, reduction of reliance on imported fossil fuels, utilisation of eco-friendly on-farm energy generation and the commercial availability of the world’s first methane powered tractor marks a welcome significant new era in how the agriculture industry can apply science and engineering to improve the environment. 

The detailed question and answer session, which followed, reflected the knowledge, enthusiasm and commitment of the presenters. We thank them all for making it such an inspiring, enjoyable meeting and AFBI for the use of their venue.