The Donkey Sanctuary in Britain has lifted the lid on its strategies for recycling about 5200 tonnes of straw-based manure waste each year.
The charity has several collaborative arrangements in place to ensure the waste is repurposed in an environmentally friendly way.
The general farm manager for its eight British sites, Annie Brown, is responsible for the care of 2600 donkeys, who are collectively responsible for the prodigious output.
The charity had been in the habit of composting the manure/straw mix and then spreading the resulting soild conditioner on the land it used for grazing and haymaking.
However, research revealed that its composting process did not reach high enough temperatures to kill all the parasite eggs in the manure.
This posed an increased risk to the health of its residents, so the charity took alternative measures to ensure it minimised 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.
The charity has been investigating other ways of processing the manure. It says finding environmentally friendly ways of managing parasites in its herds is a top priority.
The head of research, Faith Burden, says: “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, home to more than 500 donkeys, is one farm where the recycle initiatives go a step further. The straw-based manure from this site is used in a collaborative project with Rowan and Mathew Carter, from Greendale Business Park and Farm Shop.
The donkey barns get mucked out on a two-week cycle as part of the charity’s parasite control strategy. The manure is transported straight to the storage area at Greendale, where the dirty donkey bedding is used to supplement the cattle bedding for a time.
The Carters supply farm waste from their own cattle sheds as fuel for an 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. The donkey straw waste has proved to be perfect for mixing with the farmyard manure and slurry, enabling the digester to produce methane that is used as an energy source.
The sterile byproduct left after the anaerobic digester has 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. It had the potential to be used on the Donkey Sanctuary’s haymaking fields in the future.
Mathew Carter spoke highly of the venture, saying Greendale was pleased to be able to help Woods Farm dispose of its donkey waste. “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, the charity is confident that a bio-thermic digester is the answer in the push toward an environmentally sound future.
They have commissioned a machine which 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 72 hours. It reduces the manure in volume by 60% or more, and is capable of processing one tonne of manure a day.
The resultant product is so dry that it can be pelletized without further processing. It plans to use it as biofuel for heating.
The innovative machine, 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.