There is a tremendous amount of dairy manure waste generated by dairy farms each year that must be managed, estimated to be in the range of 694,950 tons per day generated in the US. However, there are limited options for disposing of this material, specifically manure coming from dairy Concentrated Animal Feeding Operations (CAFOs). Due to the high density of cows in such facilities, an extremely large quantity of manure is produced daily, resulting in often strong smells and continual odors that are objectionable to many people living near the facilities. Currently, the waste is usually stored in lagoons due to the relatively high percentage of water in the waste. However, lagoons and other current methods do not eliminate odor problems from dairy farming operations. Additionally, current disposal/storage methods, along with land farming, in many cases, run the risk of contaminating the air, land, and water in and around these CAFOs. Among other thing, excessive application of manure upon fields results in unwanted runoff into water supplies. Farmers often have to pay to have the excess manure hauled to landfills.
At the same time, in the global economy, increasing quantities of fossil fuels are utilized each year for electricity production, heating, steam generation, transportation and other needs. There are continual efforts by various environmentally-minded groups to encourage the decreased consumption of fossil fuels to preserve the limited quantity of the fuels, as well as to decrease the quantity of pollutants produced by burning fossil fuels. While these efforts have had some success, there is always the need for additional processes and products which utilize energy sources other than fossil fuels.
Anaerobic digestion has been used as an initiative to manage dairy manure waste and to produce a methane biogas. The methane biogas can be converted into electricity. One aspect of the use of methane for this purpose is that since the source of supply of the gas is often remote from the electricity distribution infrastructure, much of the gas is wasted. However, despite the generation of methane through anaerobic digestion, there is still a need to dispose of the solid waste resulting from anaerobic digestion.
Additionally, many dairy farms have used dried manure waste solids as bedding for dairy cows. However, when the dried manure bedding is soiled with urine or additional fecal matter, the bedding facilitates bacteria growth. The use of dried manure waste solids as dairy cow bedding leads to poor animal health, and farmers have reacted by giving the dairy cows more antibiotics to combat ailments contracted from the bedding. As a result of dried manure waste solids bedding contamination, dairy and beef food supplies are exposed to bacteria and antibiotics through the cows. Alternatively, many dairy farms have explored the use of inorganic materials, such as sand, for bedding to minimize bacterial growth and to readily drain moisture. However, sand is more costly to use, and there is a need to optimize the use of sand as bedding at a lower cost. Also, the grade of sand used previously for animal bedding has been found to be overly coarse, which irritates the animals.
At the same time, there is always a need to improve the complete water footprint of the agricultural supply chain and community. Wastewater recovered from dairy waste manure processing can be recycled for use in irrigation or on farms. To do so, however, the wastewater needs to be disinfected to cure airborne microbial issues. Alternatively, if not recycled, the wastewater also is treated before it can be discharged safely, to reduce CAFO contribution to lake and river pollution. Nitrogen and phosphorous are two nutrients present in animal waste and in excessive amounts cause an explosion of toxic algae in lakes and rivers. Activated carbon can be used as a filter for the process wastewater. However, there is a shortage of activated carbon. Thus, activated carbon can also be very costly, and there is a need for production of activated carbon from within the agricultural supply chain.
There is a need for products and processes which can utilize the dairy waste byproduct from anaerobic digestion for producing energy in a sustainable, renewable, and efficient manner, while reducing the depletion of natural resources.