The conversion of waste to energy provides huge opportunities for people living in rural areas. There are several ways of processing organic waste — and certain inorganic wastes — into viable energy, namely biogas, electricity and liquid fuels. These are not “pie-in-the-sky”and untested methods and they are not prohibitively expensive. The construction of these, the management and operation of them, the growing and transporting of fuel feedstock, maintenance, etc … all could provide thousands of jobs and hundreds of millions of dollars in revenue to areas of the country that are desperate for them. In the process, these power plants will help other industries already here and “hog tied” (pun intended).
I will be discussing these different technologies and their economics over the next few articles.
Converting livestock waste to electricity.
There are nearly 20 million hogs in North Carolina, making it the second largest hog producing state in the United States. The state has placed restrictions on the size and number of hog farms due to problems with the current methods of handling the vast amounts of manure. An average hog produces 6 pounds of solid waste per day. The total volume of solid hog waste in North Carolina is roughly 60 million tons per day. There is a similar quantity of chicken, turkey and cow poop here too.
Currently, the waste is held in lagoons, which are prone to rupture and overflow. Collecting and processing that waste in anaerobic digesters will solve the waste-handling issues by converting the solids into methane and generating electricity. There is enough hog manure in this state to power 100,000 average homes for a year.
There is no air or water pollution and the by-products of the processes are pure organic fertilizer, which has beneficial use in agriculture and an excellent market value.
A 1MW power plant can pay for itself in three to four years at current power rates, selling power into the grid, under what is called a Power Purchase Agreement. In addition, the federal government offers a tax rebate on the construction cost and there are Renewable Energy Credits available to add to the wholesale value of the power produced. Combining the wholesale price with credits, it is easy to earn a 30 to 40 percent return on investment.
You would think there would be dozens or hundreds in operation right? Not so. There are only a half dozen in the whole state. By contrast, there are 9,000 in operation in Germany. This is partly due to financing issues — banks will not loan against these — and partly due to the fact that there has been no standard design.
How anaerobic digesters work
Five kinds of bacteria are at work in these large tanks, which can be about 50 feet in diameter and 30 feet tall. The slurry inside is kept at 100 degree and is stirred continuously. The bacteria break down the organics and convert it to methane and carbon dioxide. The gases are collected and burned in a generator. The electricity that is produced can be used on site or sold into the grid.
Virtually anything that will “rot” can be put into a digester. This includes hog and chicken manure, food waste, grass clippings, fats and oils, etc … anything that is “soft and we.t” Wood and paper products are better disposed of in other ways that can also yield an abundant supply of power.
The paradigm of how energy is produced and supplied is changing quickly. In the same way it is possible to own your own solar array and sell power to the utility company, it is totally feasible for an individual or group to own and operate a biogas power plant. They provide jobs and an excellent return on investment. They reduce the need to burn fossil fuels to make power and they do not pollute. In fact, they solve the problem of what to do with all kinds of waste.