Standfirst
New developments in silage clamp construction allied to high oxygen barrier (HOB) films are significantly increasing silage production's efficiency and minimising waste and the associated carbon footprint of milk production.
Building a new clamp rather than relying on baled silage can help dairy farmers reduce costs, minimise the use of plastic on-farm and lower their carbon footprint significantly, according to forage production specialists.
Over 20 years, costs of ensiling each tonne of silage would be halved, the use of plastic would be nearly 20 times less, and associated CO₂ production would be reduced by almost 95%, says Will Wilson of forage systems specialists Silostop Agri.
“Modern high oxygen barrier films (HOBs) combined with the latest technology in clamp building are giving producers a real opportunity to move their forage production forward and make the most efficient use of home-grown feed materials whilst minimising environmental impacts.
“It’s a great example of new technology making established practices significantly more efficient and aligned with processors' and consumers' desires to see farming reduce its carbon footprint.
“Many of the practices producers have relied on are becoming increasingly unacceptable in the modern era of more sustainable production, and excessive plastic use is just one of those.
“When the alternatives to this deliver greater efficiencies on-farm whilst reducing labour, costs and CO₂ production, it’s an ideal outcome for all the links in the food supply chain from producer to consumer.”
He says that constructing a 10m x 45m x 3m clamp reveals some interesting comparisons to baled silage.
“Such a clamp is going to cost around £80,000 to build and at 0.7t/m³ it will hold around 1000 tonnes of grass silage, so every tonne stored costs approximately £80 in build costs."
“Over 10 years, that’s going to be £8/t stored and over 20 years, it will be £4/t."
“Wrapping a 700kg bale including contractors charges is around £7/bale which equates to about £10/t – significantly more than the £8/t over the first ten years of the newly built clamp."
“So over a 20-year period – well within the serviceable life of a modern silage clamp – you’ll be storing your silage for much less than the same operation using big bales.”
Table 1. Relative fixed costs of producing 1000 tonnes of silage/year as clamped silage and big bales
|
System type |
Cost/tonne (over 10 years) |
Total costs (for 1000t/year over 10 years) |
Cost/tonne (over 20 years) |
Total costs (for 1000t/year over 20 years) |
|
Clamped silage (based on construction of new £80,000 10 x 45 x 3m clamp) |
£8/tonne |
£80,000 |
£4/tonne |
£80,000 |
|
Baled silage (based on wrapping and contractor costs) |
£10/tonne |
£100,000 |
£10/tonne |
£200,000 |
New HOB films are key.
The numbers get even more attractive when you factor in plastic use, says Lucy Johnson of silage film specialists Silostop.
“You should be able to cover 22 x 700kg bales with six layers of film for every 24kg roll of wrap, so that’s about 1.09kg of plastic per bale or 1.54 kg per tonne.
“So 1000 tonnes of wrapped bales will require 1540kg of plastic per year costing around £4500/year at £75/roll.
“Looking at the clamp situation, a roll of 50m Silostop orange HOB film weighing 26kg will cover our 1000 tonnes of clamped silage. Sidewall film will add a further 44kg, so that’s 70kg."
“You’ll also need 2 x 12m anti-UV covers weighing 120kg in total, but these will last for six years, so that is 20kg/year of plastic.
“So that is a total of 90kg of plastic produced 1000 tonnes of forage in a clamped situation compared to 1540kg of plastic for the equivalent weight of baled silage – over 17 times more."
“Cost-wise, the plastic required for the big bales will cost £4425/year @ £75/roll whereas the HOB film and covers for the clamp will cost approx. £870 for 1000 tonnes of silage at current prices – less than 20% of the costs for the bagged approach.
“Assuming both types of film require the same amount of energy to produce and release the same amount of greenhouse gases in the production process, the HOB film will have a carbon footprint approx 95% less than for the plastic required for the big bales.”
Table 2. Relative costs of film used when producing 1000 tonnes/year of silage as clamped silage and big bales
|
System type |
Cost/tonne |
Total costs for 1000t for one year |
Total costs for 1000t/year over 10 years |
Total costs for 1000t/year over 20 years |
|
Clamp silage– 10 x 45 x 3m clamp (based on Silostop HOB orange film, side wall film and anti-UV covers) |
£0.87tonne |
£870 |
£8,700 |
£17,400 |
|
Bagged silage (based on six layers of film on 700kg bales) |
£4.50/tonne |
£4500 |
£45,000 |
£90,000 |
Table 3. Relative weight of film used when producing 1000 tonnes/year of silage as clamped silage and big bales
|
System type |
kg/tonne of plastic used |
Total plastic for 1000t for one year |
Total plastic for 1000t/year over 10 years |
Total plastic for 1000t/year over 20 years |
|
Clamp silage – 10 x 45 x 3m clamp (based on Silostop HOB orange film, side wall film and anti-UV covers) |
0.09kg/tonne |
90kg
|
900kg
|
1800kg
|
|
Bagged silage (based on six layers of film on 700kg bales) |
1.54kg/tonne |
1540kg |
15,400kg |
30,800kg |
Significant advantages
She says the numbers associated with clamped silage over the baled equivalent are impressive, but they are not the only advantages.
“The general direction of travel in dairying is for better use of resources and proper waste management, so unnecessary use of big bale silage is contrary to this.
“Bales are normally stored on porous hard-standing or soil, so effluent management is more difficult than with a properly designed and managed clamps."
“Baled silage also takes up more space on the ground as they can only really be stored three-high as a maximum. Even at three high, the bottom bales are compressed and this can allow air ingress and effluent leakage as the wrap moves."
“Baled silage also has more variability in terms of quality and is harder to evaluate for rations unless each separate field is marked and fed accordingly. Clamped silage has more even quality as the forage is mixed thoroughly during the ensiling process."
“Wrapped bales are very vulnerable to bird damage both in field and in the stack and don’t forget all waste plastic on-farm must now be recycled by law."
“Furthermore, waste companies do not tend to like bale wrap as it is thin plastic with high contamination levels due to the silage and soil contained, so it can be very expensive to deal with.”
High-input practices out-dated
Silostop’s Will Wilson agrees, saying with more dairy companies factoring the carbon footprint of the milk they are buying, high energy, high input practices will come under greater scrutiny in the future
“A farm’s carbon footprint is increasingly being benchmarked by dairies and milk buyers, with plastic use figuring in these totals more and more."
“Historically, such things have been fairly low on the agenda for many milk producers, with other important management decisions taking priority."
“The expansion in herd size over recent years has meant cow accommodation and manure storage have often been seen as more important than the extra forage storage capacity needed for this, but things are changing."
Home-grown forage is becoming even more important in the dairy profitability equation and is seen as one of the most important ways to reduce input costs in the future, with poor forage management less tolerated than ever, he believes.
“Overfilled clamps or poor compaction levels, for example, are not only bad news for cows, they are dangerous to operators and shorten the longevity of the clamps themselves and I think this is being recognised."
“We are definitely starting to see the better producers realising good clamps are as important as any other piece of infrastructure on the farm and critical to the economics of production."
“They do represent a longer term investment than bagged silage, but the ROI is significant and quickly achieved, particularly when used with the newer technology HOB films which reduce plastic use significantly and improve forage quality.”
“Add in the tax efficiency of using Capital Allowances for construction and Countryside stewardship grants available for roofing silage clamps and I think we’re going to see construction of new clamps becoming increasingly popular in the future.”
