Hybrid rye proves a cheaper alternative to maize for anaerobic digester feedstock

Article taken from the Farmers Guardian

When Farmgen’s first anaerobic digestion plant at Carr Farm, Wharton, near Preston, came online in summer 2011, the original plans were to grow maize, wholecrop wheat or triticale as a feedstock.

One of these crops would be used at a 60 per cent inclusion rate alongside waste vegetable matter from carrots, turnips, cow slurry and chicken litter from a sister company’s 40,000-head poultry unit at Drylholme.

The decision made by development manager Gary Bonnette, who had a background in the food industry and was charged with growing the first crops, was to adopt maize as the key crop for the 800kW Carr Farm AD plant.

At first, the 240 hectares (600 acres) they grew appeared to be an ideal source of high dry matter to partner the chicken manure and the plant operated at 80 per cent efficiency in its first year.

However, having grown a similar acreage in autumn 2012, Mr Bonnette was left with 36ha (90 acres) in the ground over winter.

“We plan for up to 12,000 tonnes of feedstock a year – 40-60 per cent of which was due to come from maize,” he says.

“However, in the end we were about 7,000t short, purely because of a season when no variety could met its potential this far north and our type of land.

“We only put a pre-emergence herbicide on the maize due to the poor weather conditions, so production costs were low, but it only yielded 11t/acre.  That is against a budget of 15t/acre, so we were forced to look at other feedstock sources.

“We have an abundance of grass at Warton and Dryholme, which we did, in part, utilise, but too much (above 15 per cent) causes issues with nitrogen in the digester.

“Fortunately, we negotiated good prices on locally-grown carrots and potatoes and acquired about 8,000 tonnes.

“This, with additional dairy waste from local farmers and cheese companies, ensured we had enough feedstock."

Mr Bonnette started to look at other crops to replace the maize on-farm and, following a meeting at Myerscough College, he teamed up with Agrovista and agronomist John Ball to try hybrid rye.

Taking a risk

“At first, John had 50 acres of the hybrid rye available [KWS Magnifico].  On the back of his advice and field trials he had seen over the previous season, we took the lot, acting as a guinea pig in this part of the country.

“Hybrid rye’s appeal was the potential to get it off and into the clamp in late July or early August, while still getting a similar textbook DM yield to that of maize.  We were not disappointed,” says Mr Bonnette.

While some fields did 45t/ha (18t/acre), with an average yield of 41t/ha (16.4t/acre), KWS Magnifico provided 690t – 700t of feedstock in the clamp.

“It was also about half the price to grow compared to maize and we left nothing in the ground,” he says.

“Most importantly, the hybrid rye had similar starch and DM levels to the previous year’s maize.  While we found we were lucky to get 156-170cu.m/t of methane for every tonne of maize, the hybrid rye was delivered about 160cu.m/t, so compares well.”

Mr Ball, who walked the crop for Farmgen, says he was delighted by the performance, especially as it was drilled late in February because of the weather and land conditions.

“Plant breeder KWS suggests the optimum drilling date is in mid-October and the latest drilled crops they had seen in trials were drilled at the end of December,” he says.  “Our crop just shows how aggressive the hybrid rye can be.

“While I would not advocate such a late drilling, and we were fortunate to get a window in the weather to get it in, rye does have a lower vernalisation requirement than wheat, so it was a calculated risk which paid off.”

Unlike rye grown for grain, which has strong potential on lighter land, KWS Magnifico’s earlier harvest and high biomass suited Farmgen’s stronger soils.

“Yield is everything to the biogas producer, outweighing quality to a large extent, particularly if you are mixing it with other fast-acting material such as chicken manure in the digester,” says Mr Ball.

The Farmgen crop was harvested in the last week of July, coming in at virtually the same time as wholecrop wheat.

Gas yields

“Ideally we would have liked it earlier, but maturity was probably three to four weeks behind where it would have been had we drilled it in the autumn,” says Mr Ball.

“The proof of the puddings is in the eating and gaseous yields look good,” says Mr Bonnette.

“Inputs costs are also low.  At Warton we spent £554/acre on maize and at Silloth, nearly £600/acre, compared to hybrid rye at just £234/acre, including labour and digestate.

“All we had to do for the rye was a bit of buck-rating at clamping, so it is a ‘win-win’ compared to the maize model.”

Looking forward, Farmgen can see other benefits to its farm rotation from being able to get a biogas crop in the clamp in June or July.  Mr Ball says the early cropping from hybrid rye would also provide an ideal entry for oilseed rape in the rotation.

“In Germany, they dual crop with maize, following an early cut crop of rye with a short-season ultra early maturing variety such as Ramirez.  This could be an interesting option to explore, but the season would have to be with us,” he says.

Having seen rye’s performance, Farmgen will be looking to grow it on a much larger area in 2014, although it will have to fit in with the farm’s rotation, particularly cereals, oilseed rape and possibly potatoes.

“With cattle no longer featuring on the farm, it has replaced some of the grassland, which has been burned off and turned around in September.

“On this ground, pre-em herbicide use will be key to helping the rye outcompete the weed,” says Mr Ball.

“If we need to spend £50/acre to get the crop established after grass, controlling slugs and leatherjackets as well, that is nothing compared to the potential benefits of extra yield from early drilling in the grand scheme of things,” says Mr Bonnette.


22 November 2013

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