Getting the best feedstock for your AD plant is vital

Friday 14 October 2016

An engineer by background, Stephen Temple was always going to make some changes on the family farm when he returned to work alongside his father in 1998. His plan was to make the farm as self-sufficient and self-contained as possible, while adding value to the established dairy herd, and looking for ways to add to the unit’s income.

With a background in helping to build the first AD plant in Malawi, it was hardly surprising that one of his first decisions was to install an anaerobic digester at Copys Green Farm in Wighton, Norfolk. And it was one with a combined heat and power unit that could sell electricity to the national grid, while also supplying the farm… one that could be used to heat the dairy, farmhouse and drinking water for the cows, provide hot water for the cheesemaking enterprise, and be used for grain drying.

“We use carbon-neutral fuel wherever possible,” says Stephen. “We’re currently using methane from the biogas plant for generating up to 170 kW of electricity for the grid, and for our own use. We also use the supply for the farm office, house and three nearby farm cottages. We heat our grain using a 200 kW radiator to heat the incoming air.

“We’ve replaced a van and an 18,000 miles/year diesel car with fully electric Nissan Leaf and Tesla cars – and all our farm equipment is selected on the basis of energy efficiency. We export to the grid more than twice the amount of energy we buy as diesel fuel, and have recently equipped four farm staff houses with PV panels and two with wood pellet boilers.”

The farm size was more than halved on his father’s death, with the 1300 acres reducing to 500 acres, as the remaining 800 acres had been on a tenancy which was taken back in hand. So it became even more important to look at making every acre work, and look at diversification to ensure the farm had a future.

A brave decision was to switch the award-winning Holstein herd to a Brown Swiss herd – cows that produce a better protein structure within the milk for the cheese-making business run by his wife Catherine. The Temples have been making cheese with a growing reputation to the past 15 years, with seven different varieties now in big demand.

“We run just over 100 cows, and have about 100 youngstock,” he says. “There are only four first-cross Holsteins left on the farm now, the rest are pure Brown Swiss. Calving is year-round, which suits the needs of the farm cheese business, and any surplus milk is sold to Arla.

To make the switch he imported 74 in-calf pedigree heifers from Bavaria, and with milking twice a day, average yields top 8000 litres/cow. Two of his herd are classified as Excellent and 28 as VG.
Work started on the digester in 2008, with the first gas produced in 2009. Roughly a quarter of the electricity generated is used by the farm, with three quarters exported to the grid.

“We’re trying to use as much electricity ourselves as possible,” says Stephen. “We’ve switched to electricity for our irrigation pumps – from diesel – and our energy beet is chopped by electricity. Being able to supply the dairy herd with warm drinking water in the winter is a bonus, and we’re able to dry our grain for just £12 a day.”

Key to the whole enterprise has been ensuring high energy, top quality, feedstock is used in the AD plant. Stephen was also determined to ensure the farm was self-sufficient in feedstock – he did not want to be buying-in feedstock or carting ‘fuel’ from other areas.

“Maize silage is key to the whole farm operation,” he explains. “Not only is it essential in the TMR fed to the dairy herd and young stock over the winter, it’s a key part of energy supply for the digester.”
One of the problems facing Copys Green Farm is the closeness of the North Sea – just over 2 miles – and the high winds that sweep across the farmland.

“It’s been really hard to protect the silage in the outdoor clamps,” he says. “In the past we had to accept a degree of spoilage as the wind would whip under the plastic and let oxygen into the clamp. Then I saw some advertisments for Silostop, and the scientist inside me saw that the oxygen barrier technology made absolute sense. Since we started using it, we haven’t looked back.”

Silostop, a unique orange film that clings to the silage forming a tight seal, contains oxygen barrier technology that eliminates any spoilage as long as the clamp is kept airtight.  “We’ve seen our wastage reduce from the top foot across the whole clamp, to just an inch or two, and plan to eliminate that this year by placing large round bales across the top to complete the seal.

“Before we would have had to dump the spoilt silage. Now even the small amount of waste is still good enough to feed to the digester.  “I see absolutely no point in making good silage, and then watching it go to waste once it’s in the clamp. We’re always evaluating other products, but always come back to Silostop."

“We need high energy digester feed, and the maize silage fulfils a key part of the mix, along with whey from the cheese making process, farmyard manure, fodder (energy) beet and wholecrop rye. If we let oxygen get into the clamp, we’re losing the energy value before we start to use it.”

His view is supported by Neil Groom, technical director for Grainseed, the company that supplies him with the Silostop film. “My job is to make sure that farmers get the most out of their silage,” he says. “I can’t understand why every farmer isn’t using the Silostop products. It makes absolute sense to protect the energy value of the crop, and the amount of crop you can feed. It costs a lot to grow, harvest and get it into the clamp. Why not make sure you look after it over the feeding period?”

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