The Donkey Sanctuary is working collaboratively to dispose of its donkey manure in an environmentally friendly way.
Annie Brown, General Farm Manager for the eight UK sites, is responsible for the care of 2,600 donkeys and says: “Our donkeys produce around 5,200 tonnes of straw-based manure waste each year which all has to be disposed of."
Our research team has recently found that due to the inevitable build-up of parasite eggs in the manure there is an increased risk to the donkeys’ health if we continue to compost the manure and then spread the resultant soil conditioner on the grazing and haymaking pasture land.
This is because our composting process does not reach high enough temperatures to kill all the parasite eggs. Once this problem was identified we stopped spreading the composted manure onto our fields so that we minimise the transfer of parasite eggs onto the pasture.
The composted manure has since been exported to local farmers who reap the benefit of the manure by ploughing it into their arable land, where the parasite eggs can do no harm. We have since been investigating other ways of processing the manure.
Finding environmentally friendly ways of managing parasites in our donkey herds is a top priority.
Faith Burden, Head of Research says: “Finding environmentally friendly ways of managing parasites in our donkey herds is a top priority. By controlling parasite contamination levels in the environment by careful manure management we are able to decrease the amount of de-worming drugs given to our donkeys thus reducing drug resistance and reducing the amount of chemicals released in to the environment. Working collaboratively with other farms enables us to benefit our donkeys, our natural environment and of course the farms themselves."
Woods Farm is home to more than 500 of our donkeys. To recycle the straw based manure from this site we have collaborated with Rowan and Mathew Carter from Greendale Business Park and Farm Shop.
Our donkey barns get mucked out on a two-week cycle as part of our parasite control strategy and the manure is transported straight to the storage area at Greendale; this dirty donkey bedding is used to supplement the cattle bedding.
The Carters supply farm waste from their cattle sheds as fuel for the anaerobic digester on the Greendale site, the digester produces methane which is converted to electricity that powers the Greendale Farm Shop and Restaurant.
The anaerobic digester needs constant feeding with a carefully balanced mixture of straw, farmyard manure and cereals such as maize. Our donkey straw waste has proved to be perfect for mixing in with the farmyard manure and slurry; enabling the digester to produce methane that is used as an energy source.
The sterile digestate, the product that is left after the anaerobic digester had extracted the methane, could potentially be used as fertiliser and will enable Greendale to put something back into their land, minimising the need for use of artificial fertilisers and could potentially be used on the Donkey Sanctuary’s haymaking fields in the future.
Mathew Carter says: “By collaborating with The Donkey Sanctuary we are helping them to dispose of their donkey waste from Woods Farm and after hearing from Annie about the fantastic work that the Sanctuary does around the world we are keen to support them further by having a collecting box in our Farm Shop and we are investigating the idea of re-homing a pair of donkeys from them.”
Elsewhere at The Donkey Sanctuary as part of our quest to be as environmentally friendly as possible we are confident that a bio-thermic digester is the answer.
The machine we have commissioned is hopper fed and works with an auger that moves a consistent stream of chopped manure through the oven which turns and cooks the manure at 70 degrees centigrade over a period of 72 hours until it is reduced in volume by 60% or more and is capable of processing one tonne of manure per day.
The resultant digestate from this process is so dry that it can be pelletized without further processing and ultimately we plan to use it as biofuel for heating.
This innovative machine, which was originally developed to minimise landfill and process black bag waste, is due to be installed at Trow Farm in December 2015; it will be able to process all the manure from the main Slade House Farm site and potentially the manure from the other local Donkey Sanctuary farms.