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On page 6 of last week’s edition dated 12 November 2022, we highlighted a new crop being introduced to NI, which it is claimed could be a viable alternative to maize, especially for use in Anaerobic Digestion (AD).
Silphium perfoliatum, is also known as compass or cup plant, and in the UK is being marketed under the name Sunergy.
It is a perennial crop originally native to eastern and central North America, is widely grown throughout Europe (over 10,000ha grown in Germany in 2022), and produces high yields from relatively low inputs.
The sole distributor of Sunergy in the UK is English specialist seed company, Newtone Agriscapes, with Portadown-based ReCon Resources taking on the role as agent in NI and Scotland.
At a recent launch event outside Dungannon, William Robinson, a lead consultant at renewable energy company B9 Solutions, presented analysis on the potential yields, costs and outputs that can be expected from the crop.
While there hasn’t been any local research done on Sunergy, there are numerous research papers emanating from Germany, Poland, Lithuania and the US. Summarising this work, Robinson said he was interested in three parameters – dry matter (DM) yield, volatile solids content and biomethane potential.
Some studies have shown that Sunergy can yield well over 20t DM/ha in good growing conditions, however, Robinson said yield will typically be in the range of 15 to 16.3t DM/ha. “The yield of Sunergy will be higher than two- or three-cut grass and reasonably comparable with maize silage,” said Robinson.
The other two parameters – volatile solids content and biomethane potential – are linked to the suitability of the crop for use in AD.
The review of the literature by Robinson suggests Sunergy will produce similar amounts of biomethane as grass silage, but higher yields mean it there is more gas produced per ha of crop.
When compared to maize, which is widely accepted as being ideal for use in AD, there is a range across the literature, although in summary, Robinson maintained that Sunergy is “getting close to maize silage”.
Costs
He also compared growing costs of Sunergy versus two- and three-cut silage, and maize with and without plastic, assuming that Sunergy has a life of 12 years, while the grass is reseeded every six years.
His analysis suggests that for every fresh tonne harvested, grass costs £41 to £46/t and maize costs £47 to £64/t. However, with Sunergy on a 12-year cycle, it has much lower sowing costs, and as a low-input crop, has a reduced nutrient requirement. Robinson estimates costs of around £16 to £17/t of fresh material for Sunergy.
Biomethane
Where biogas in AD is upgraded to biomethane, payments under the Renewable Transport Fuel Obligation (RTFO) may be available if the resultant fuel is supplied to the transport sector. However, to be eligible, these renewable fuels must now deliver at least a 65% greenhouse gas emissions saving compared to a fossil fuel baseline.
“Maize silage is on the cusp of the sustainability criteria, depending on the site,” suggested Robinson. He said he was “confident” that Sunergy will meet the criteria, given it is a perennial crop. In addition, because of its deep root structure, it should be actively sequestering carbon into the soil.
“We are conducting a full greenhouse gas analysis of the Sunergy crop, and results should be available by the end of the year. But overall, we think it is a very positive outlook for Sunergy,” concluded Robinson.
The big upfront cost with Sunergy is at establishment.
It is a small seed, costs around £500/kg and is typically sown at around 3kg/ha, to give four to five plants per m2.
In much of Europe it is often grown alongside maize as a nurse crop. Sunergy needs to go through a cold phase (winter) to produce stems, so the first significant harvest is not until the autumn of the following year.
In NI, harvesting maize without damaging Sunergy plants could be a challenge, so an alternative is to sow the crop on its own in late summer or early autumn.
“In NI, it might be best sown in August and September, which means you get a crop the following year. On balance we are leaning towards autumn sowing being more beneficial,” said Nick Green from Newtone Agriscapes.
He said the aim is to sow into a stale seedbed treated with a pre-emergent spray.
Drilled
In Europe, the crop is normally precision drilled, with work ongoing by Green to look at different drilling techniques. The first sites in the UK were planted in spring 2022, including in Wales, Kent, Sussex and Warwickshire.
He said Sunergy will grow across a wide range of sites. “What we have seen in England is growers choosing smaller fields not suited to a 40m sprayer or part of fields that are tricky to grow other crops. It is drought tolerant and will cope with wet conditions. It is harvested in the same way as maize,” he said.
The only sites to avoid are areas that potentially lie waterlogged over the winter. It should also not be grown after oilseed rape to prevent a potential sclerotinia carryover.
Biodiversity
With a three-month flowering phase, Sunergy is good for biodiversity, and is popular with beekeepers, said Green.
Once established, the crop is pest and disease resistant, and it can be grown with a single 50m3 application of digestate (4,500 gallons per acre) in the spring, which should be done before stems start to emerge.
While the crop is being marketed with a typical lifespan of 10 to 15 years, Green maintained that there are crops in Germany still holding yield 20 years post-establishment.
In AD, he expects Sunergy to produce 80% of the gas output normally achieved with maize silage.
In Germany and Austria Sunergy is generally grown for use in the AD sector, but in other parts of Europe it is also used as a cattle feed, mainly for dairy cows.
Protein levels in the crop depend on the vegetation phase, and can be as high as 15%, before declining as the season progresses. If being targeted for feed, it should be cut when the plants are in early flower. This would then be followed by a second cut in the autumn for AD.
“For a livestock feed, it is similar to a 50:50 lucerne maize mix,” said Nick Green.
The protein in Sunergy can also be used in the cosmetics industry, while development work is on-going to utilise fibre from the plant in packaging.
In 2021, Lidl confirmed it was introducing paper packaging produced from Silphium (Sunergy) for use in the fruit and veg sector.
Portadown-based recycling company ReCon Resources is the agent for Sunergy in NI and Scotland.
ReCon started out as a farm diversification project, and has now grown into a company employing over 20 people.
Speaking to the Irish Farmers Journal, ReCon managing director Daniel Connolly said he believes Sunergy is an alternative to both maize and grass silage in AD.
“There is less tillage work, less costs, steady yields and it is dependable from year to year. If as a farmer you get a bad maize harvest on your farm, it is usually the same for everyone else, so the price gets driven up,” he said.
He also points out the environmental benefits of the crop. “There are lots of different reasons why you might go down the route of this material. We intend to grow some on our own farm next year,” he added.
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