Using Horse Manure for Renewable Energy
When land-application or composting of horse manure isn’t viable, due to insufficient land, space, or progressively stringent regulations, one alternative that is increasingly being implemented around the world is to make renewable energy. While the idea of using manure for energy isn’t exactly new (sun-dried manure was used for heat as far back as Ancient Persia and Egypt), the technologies required to turn horse manure into renewable energy in an efficient, economical, and environmentally manner are.
When it comes to turning horse manure into renewable energy there are two main types of technology to choose from; biomass boilers and gasifiers . Biomass boilers are similar to conventional gas boilers that most readers will be familiar with; the key difference being that instead of natural gas or oil, biomass boilers burn biomass, such as wood, to produce heat. Biomass boilers are also much larger than their conventional boiler counterparts, and require a mechanism to fed biomass into the boiler. Gasification involves the partial combustion of biomass in small amounts of oxygen at high temperatures of 900 – 1,400oC. Instead of burning the biomass, gasification converts the chemical energy in biomass into a fuel gas known as ‘syngas’. Syngas, commonly made up of a mixture of hydrogen, methane, carbon monoxide and carbon dioxide, can be utilised in a range of applications to produce renewable heat, electricity or liquid fuels.
Manure Type and Volume
The cornerstone of any successful biomass renewable energy project is feedstock; in this case, horse manure. Understanding the characteristics and volume of horse manure is essential to determining the economic feasibility of producing renewable energy. Stall bedding material, housing climate and management practices can vary between equine facilities. Understanding this and how it can impact horse manure composition, moisture content and volume is essential.
Horse manure that consists primarily of wheat, oat, rye, straw, hay, or dried pasture clippings can be difficult to use for renewable energy production due to its high ash content and low ash-melting temperature (the temperature at which ash becomes sticky, adheres to surfaces and causes corrosion). While not insurmountable, these difficulties require more expensive equipment, making economic feasibility very challenging. Sand-based horse bedding is also undesirable as potential energy content is extremely low.
The moisture content of horse manure is important, as wet manure will likely require some form of drying before it can used in a biomass boiler or gasifier. The amount of drying required will depend upon the type of boiler or gasifier used. While heat from biomass boilers and gasifiers can be used to ore-dry horse manure, any heat used for this purpose reduces the amount of renewable energy that can be used on-site or sold, negatively impacting project economics.
In addition to characteristics, manure volume is also important. Generally speaking, biomass boilers and gasifiers twice the size and that produce twice the amount of renewable energy, are less than twice the cost. Therefore, larger volumes of horse manure generally lead to improved economic feasibility thanks to economies of scale. If you don’t have enough horse manure from your own equine facility, consider working with a close neighbour to combine your manure. Bigger is almost always better.
On-site Energy Needs
If feedstock is the cornerstone of a successful biomass renewable energy project, an equally essential criteria for economic feasibility is on-site energy needs. As mentioned previously, biomass boilers produce heat. If there is no demand for heat on-site or within the vicinity of a biomass boiler, there is little value to be gain from producing it. Furthermore, if the cost of heat is low, even if demand exists, the economics just don’t add up. To overcome this problem, manure could be transported and converted to heat at a site with high heat demand. However, transportation costs can quickly eat into project economics.
Unlike biomass boilers, gasifiers produce syngas that can be utilised in a range of applications to produce renewable heat, electricity or liquid fuels. Electricity can be injected onto the local grid for sale to a local utility, while liquid fuels can be transported for off-site use. However, while gasification might overcome limited on-site energy needs, conversion of syngas into electricity or liquid fuels requires additional, sometimes expensive, technology.
Using horse manure to produce renewable energy can help to minimise odor, reduce run-off (non-point source pollution), and solve other environmental and social nuisances often associated with the land-application or composting of large volumes of horse manure. Using horse manure to produce renewable energy can also enable equine facilities to meet increasingly strict regulations, while helping to improve neighbourly relations, especially in areas where equine facilities are close to urban environments.
Despite the many environmental and social benefits of using horse manure to produce renewable energy, local and regional government approval is still require before a biomass boilers or gasifier can be installed. Determining what these approvals are, who to contact, and how to acquire them can be very challenging, especially in areas where biomass boilers and gasifiers are not commonly used. Allowing adequate project time and resources to get the necessary permitting is vital.
Using horse manure for renewable energy production offers a number of advantages for equine facilities. Renewable energy can be cheaper than propane, electricity or natural gas, while using it for renewable energy can minimize disposal costs. Furthermore, using horse manure for renewable energy can have a number of environmental and social benefits, including helping to minimize odour from land-application, reducing run-off from storage, and replacing use of fossil fuels.
However, while horse manure for renewable energy production can be a good idea, it should be noted that one size doesn’t fit all. What might work/make sense for one equine facility might not work for another seemingly similar facility. What type and volume of manure do you have? What are your on-site energy needs? What are the local regulatory requirements? All these factors must be carefully considered before deciding if horse manure to renewable energy is right for you.
For more information about using horse manure for renewable energy production, or if you have any questions regarding biomass renewable energy, please contact us.