Farmer Jonny Wyatt is utilizing waste warmth from the anaerobic digester (AD) plant on his blended farm close to Thetford, Norfolk, to dry out-of-spec straw to make drier bedding for his livestock.
The ensuing farmyard manure is then fed to the AD plant to supply vitality for the farm and digestate to fertilise the grass for the dairy herd.
The intention is to enhance the environmental sustainability of the farm enterprise, decreasing waste and making the perfect use of the “waste” that’s produced whereas reducing somatic cell counts (SCCs).
- 240 pedigree Holstein and Shorthorn cows
- Autumn-biased calving
- Common lactation 8,500 litres, with 3.4% protein and 4.25% butterfat
- Milk provided to Arla Morrisons
- 303ha (750 acres) arable rotation, rising grass, maize and sugar beet, with land let for potatoes and onions
- 10ha (25 acres) let for outside pig manufacturing
- On-farm anaerobic digester taking slurry, muck and a few maize
- 14 HGV lorries used for sugar beet, grain and straw haulage
Mr Wyatt has agreed a contract with next-door Snetterton Renewable Power Plant to take straw bales that fail its standards for high quality.
The vitality plant has a 43MW energy output produced from straw and woodchip.
He sells straw produced on-farm to the vitality plant and replaces it with the vitality plant’s out-of-spec straw. That is often straw with too excessive a moisture content material, or lacking strings.
As an alternative of a lorry load of straw being rejected and returned to the farm of origin (even when it accommodates just one out-of-spec bale), he now dries it and makes use of it to mattress down his cows. This reduces street miles and makes use of an in any other case wasted product.
The straw is dried in a brand new barn measuring 66x27m. This features a 12x27m bay at one finish for equipment storage.
On the different finish is a Kongskilde Ventus 2400 straw dryer. In-between is an space giant sufficient to retailer undercover all of the straw the farm wants – 3,000t a yr for the farm’s 240 dairy cows and youngstock.
A teleporter is used to feed bales onto an eight-bale conveyor belt which strikes them in direction of the dryer. That is repeated thrice a day.
The straw is dried utilizing warmth generated from the on-farm AD plant. The plant, put in in 2016, generates 0.5MW of electrical energy.
That is sufficient for all of the farm’s wants, with extra offered to the grid.
An underground pipe brings sizzling water, produced from cooling the engine that runs the AD plant, to the brand new barn.
Right here, it enters a warmth exchanger at 86C and the recent air produced is blown by a fan right into a tube. From right here, it’s pressured by means of a collection of probes into the straw bale for a pre-determined variety of minutes.
The bale is then pushed off the dryer prepared for stacking.
Up to now, the bales are arriving on the farm with a median moisture content material of greater than 25%.
“We stock out a visible evaluation after which take a moisture studying utilizing a hand-held probe,” says Mr Wyatt. “The goal for the dried bales is lower than 15% moisture, and it’s taking about 45 minutes for each.”
Beforehand, straw needed to be saved exterior. At occasions, this meant damp straw had for use as cow bedding, resulting in potential rises in SCCs within the milk.
“Micro organism thrives in a moist atmosphere, and this may contribute to excessive SCCs,” he says. “As a result of we run deep-littered yards, we wish to mattress with straw that’s as dry as potential.”
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The herd’s present SCC common has been operating at 170,000 cells/ml for the reason that straw dryer started working. The dairy crew’s intention is to get this all the way down to 100,000 cells/ml, and it’s hoped bedding with persistently dry straw will assist attain this goal.
Yards are bedded with the straw every day and mucked out each 4 weeks. The muck is then fed to the AD plant, together with a mixture of maize and crop residues similar to sugar beet waste, and any very poor-quality straw.
The system fits the cows and the AD plant. “The cows should be mucked out recurrently and the plant works greatest with contemporary muck as a result of it produces extra gasoline,” says Steve Bailey, who manages the plant.
“Nearly all of the gasoline comes from the straw content material of the muck. If the straw begins to interrupt down, cardio – slightly than anaerobic – decomposition is happening,” he says,
“If we have been additional north or west, we’d most likely have cow cubicles, however right here we’ve got entry to straw, so it is smart to mattress with deep litter – which we’ve then used to enhance our sandy soils,” provides Mr Wyatt.
“The AD plant isn’t a bolt-on for a bit of money – it’s an integral a part of our farming system, and every little thing rotates round it,” he says.
Earlier than the AD plant was put in, farmyard manure was tipped in fields and unfold. Now it’s used to feed the plant, and the ensuing digestate is unfold as an alternative.
“With the worth of fertiliser, I’m very glad I’ve acquired it,” says Mr Wyatt. “This season, I’ve purchased in a single load of 29t, however that’s all. We’ll use soiled water and digestate.”
An umbilical system is used on the fields across the farmyard, whereas a brand new tanker will unfold digestate on land additional away.
The price to construct the barn and purchase and set up the straw dryer was £600,000. A grant of £160,000 from the Rural Growth Programme for England helped in direction of the challenge and two members of employees have been taken on to function the dryer.