The costs of managing horse manure were found in a Swedish study to be similar to feeding costs.
University of Gävle Researchers Åsa Hadin, Karl Hillman and Ola Eriksson set out to examine the prospects for increased energy recovery from horse manure, carrying out a case study in a Swedish municipality. The trio examined management practices, environmental impact and costs.
The researchers, writing in the journal Energies, said a transition to renewable energy sources and a circular economy had increased interest in renewable resources not usually considered as energy sources or plant nutrient resources.
“Horse manure exemplifies this, as it is sometimes recycled but not often used for energy purposes,” they said.
They looked at how the collection and transport of horse manure to a biogas plant would compare to on-site unmanaged composting. Their work included a simplified economic analysis.
The municipality in northern Sweden used for the study has about 100,000 inhabitants. Eighty-one horse-keeping sites were enlisted, which were home to 623 horses. The researchers found that 84% of the properties had 10 horses or fewer.
Most (69%) kept their horses stabled. Fifteen percent used loose housing in combination with stables, and 15% used loose housing exclusively. One horse keeper used paddocks extensively.
It was found that horse manure management was characterized by indoor collection of manure most of the year and storage on concrete slabs or in containers, followed by direct application on arable land.
Softwood was most commonly used as bedding, which accounted for only 13% of the total mix.
It was found that anaerobic digestion (that’s digestion in the absence of oxygen) would reduce the potential environmental impact in comparison to unmanaged composting.
While transport of the manure to the plant constituted an increase in potential environmental impact, it was still worthwhile once the low environmental impact of anaerobic digestion was factored in.
However, it was found that the costs of manure management or horsekeepers would likely increase for anaerobic digestion as compared to unmanaged composting on site.
They also found that the costs of manure management were of the same magnitude as feeding costs.
“Due to the conclusion that environmental impact is reduced if horse manure is transported to an expected biogas plant, further research could address energy companies’ willingness to use horse manure as a biogas feedstock,” the researchers said.
“Depending on their answers, continued research might consider horse keepers’ willingness to adapt to energy companies’ requests to, for example, change bedding or perform thorough sorting at the site to ensure good quality of feedstock.”
Prospects for Increased Energy Recovery from Horse Manure—A Case Study of Management Practices, Environmental Impact and Costs
Åsa Hadin, Karl Hillman and Ola Eriksson
Energies 2017, 10(12), 1935; doi:10.3390/en10121935 http://dx.doi.org/10.3390/en10121935