Anerobic Digestion
Grass
We grow grass as our main feedstock for the AD Plant. It is a hybrid ryegrass with mid-season diploid and tetraploid varieties that ensure a high D-Value is maintained. We take 4 cuts of silage from crop this each year.
It is reseeded every 4-5 years depending on how the yield is. We have moved away from ploughing to direct drilling grass seed. This locks carbon into the soil and maintains a healthy top soil. Ground compaction is eliminated with the use of a subsoiler.
Harvest & Clamp
We harvest the silage crop with our own silage equipment. Grass is mowed with a set of Kuhn triple mowers and the grass is spread out. It is left for 24 hours before it is raked into a 9.5m row with our Kuhn rake. The grass is harvested with a New Holland FR780 forage harvester. The grass is chopped to between 6 and 10mm. It is all brought back to the clamp with the help of a few contractors. Buckraking is carried out with a New Holland T7270 tractor with a 3m front-mounted push-off buckrake. It is consolidated with a 4 tonne Rhino compactor on the back of the tractor.
Spreading The Digestate
Once the silage has been harvested digestate spreading starts straight away. Thompson Brothers Contractors carry out this service. They spread it with a 12m dribble bar. The digestate is brought to the field with slurry tankers and blown up the umbilical pipe to the spreading tractor. He uses GPS on the tractor to avoid overlapping. This is the best system to avoid ground compaction ensuring a quick regrowth.
Sow Fertiliser
All of our land is tested each year. The digestate is tested to see what the nutrient value of it is. This then determines if there is any extra fertilizer required to feed the crop of silage. It usually involves putting on about 125kg of nitrogen per hectare in the form of CAN27. The fertilizer is spread with a New Holland T7210 and a Vicon Geospread spreader. This has a spread with of 24 meters. All of our fields are mapped using New Holland PLM software so the spreader knows where the boundaries of each field are. It is fitted with sectional control which avoids spreading beyond boundaries and avoids overlaps in the field.
Lactose
We use Lactose as a feedstock for the AD Plant. This is a left over product from cheese production. Three lorry loads are delivered to the site each week. It is a liquid product that has a 28% sugar content so provides a great source of readily available energy.
Cattle Slurry
Every week we bring in three 4500gallon tanker loads of cattle slurry from a local dairy farmer. This provides the plant with valuable bacteria that keeps the digester healthy. Think of it as a pro-biotic for your stomach.