A NEWLY installed methane digester will produce enough power to meet half the cost of running the dairy barn and robotic milkers on a Bungaree farm.
The digester was being installed when Dairy News Australia visited in November and can process 24,000 litres of eﬄuent a day. Once the gas has been extracted, the separated liquid and dry matter-now odourless-can be spread on the farm. Mark Trigg-one of four partners in the dairy and potato seed operation, along with his father Ron, cousin Tony and Dave Lee- said the dairy barn and digester complemented each other.
The Triggs built a 500-head dairy barn in 2014 and installed DeLaval milking robots in March last year. About 220 of the 300-head herd live in the barn and are so comfortable they do not venture outside. The barn design sees the manure continuously scraped from a central laneway and into an underground pit. This was previously collected and spread on pasture, but Mark Trigg said the smell was becoming problematic.
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“Eﬄ uent has been an issue. In summer time it gives oﬀ a fair aroma,” he said.
“We knew about methane in the pig industry for a long time so thought why can’t we do it?
“Essentially, we’re trying to value add manure so we can generate power and recoup power costs.”
Research led them to Ballarat company Gekko Systems-which primarily designs and produces equipment for the mining sector- which designed, built and installed the prototype device.
The current system, located next to the barn, comprises 10 cargo containers. Eﬄuent is pumped from the pit under the barn to six containers, where it is warmed to 36 degrees. Bugs produce the gas, which is stored in a separate container and used to generate power.
Once the process is ﬁnished, the eﬄuent is run through a screw press to separate it, and liquids and solids will be stored in a new dry bunker and 100,000 litre pit. Mr Trigg said the ﬁnal product was organic and odourless and would be spread three times a week.
The system includes a 35kVA generator, which should cover 50 per cent of the running costs of the barn, or the equivalent of $10,000-$15,000 to $30000 a year.
“We have a 60kVA generator there that just handles (running the barn), and that costs about $4000 a month,” Mr Trigg said.
New living arrangements
The family purchased the 160m by 40m barn from China and installed it themselves in 2014.
“It roughly worked out to be the same price to buy steel in Australia-galvanised and packed from China,” Mr Trigg said.
He said a choice had to be made between the barn or upgrading their 36-stand rotary and improving the farm’s laneways. The barn gave the additional benefits of sheltering the cows through very wet winters and hot summers.
“They can be knee deep in mud in winter and we can have 30-degree weeks in summer,” Mr Trigg said.
They used straw bedding for the ﬁrst year- working through 12 big square bales a week- before installing foam mattresses with a rubber cover.
Mr Trigg said sand bedding was ideal but they could not ﬁ nd a dry source of sand. Keeping it dry and clean would also increase the workload signiﬁcantly.
Manure from the generator can also be used but they are undecided on this at this early stage.
“We would like to see mattresses made a bit more comfortable but mastitis can increase with organic matter. However, if you can get better cow comfort, it could be worth it.”
Mr Trigg said getting cows used to robots was easier than the transition from the paddock to the free stall.
“Within ﬁve days 70 per cent of the herd were in their bed. For the ﬁrst couple of days they walked up and down.”
Cows are so comfortable now they don’t want to leave.
“We did maintenance on two robots so took half the herd out and they bellowed for three days, wanting to come back in.”
Cows leave the barn when dried oﬀ. With four robots installed, the barn is limited to 240 cows but there is space to add another four boxes. High production cows are producing more than 60litres a day and the average in the barn is 35litres, although this has peaked at 38.
Mr Trigg said production had risen, incidents of mastitis were similar and there was more emphasis on foot trimming. Sexed semen is utilised to build the herd to 500 cows.
All-year calving has also been introduced and the robots are providing information to help them ﬁne tune their AI program.
“We’re trying a few diﬀerent things,” Mr Trigg said.
“We try not to calve too many cows between June-August, and Christmas time. If they are over 300 days in milk and still doing 30-plus litres, there’s no rush to get them in calf.”
There is provision to expand the digester to cope with the extra manure in future years. Barn changes feed mix The 220 cows get 11 tonnes of feed a day.
The mix of maize silage, grass silage, canola meal, wheat and minerals (bi-carb, lime, pellets and salt) is fed four times a day. All fodder and wheat is grown on the 400ha property, as well as 60ha of seed potatoes.
“We never used to grow cereal crops but we can now,” Mr Trigg said.
“We grow 500 to 600 tonnes of wheat now the cows are in the barn and oﬀ land that was previously pasture. We had 4 tonne cereal crops last year. It’s a fair saving not buying wheat in.”
As seed potatoes can’t be planted in the same paddock within ﬁve years, wheat is planted after potatoes, followed by Italian rye-grass or annual rye-grass, followed by maize.
“We’ve started growing maize again the last few years,” Mr Trigg said.
“We were growing lucerne but you get more bulk and energy in maize.”