Thermal depolymerization (TDP) is a process for the reduction of complex organic materials (usually waste products of various sorts, often known as biomass and plastic) into light crude oil. It mimics the natural geological processes thought to be involved in the production of fossil fuels. Under pressure and heat, long chain polymers of hydrogen, oxygen, and carbon decompose into short-chain petroleum hydrocarbons with a maximum length of around 18 carbons.
Similar processes
Thermal depolymerization is sometimes mistaken for similar processes:
- Thermochemical conversion (TCC) is limited to the changing of manure to crude oil.
- Thermal conversion process (TCP) is limited to the changing of manure and vegetable waste to crude oil.
Thermal depolymerization can change many carbon-based materials into crude oil and methane, and is not limited to manure or vegetable waste.
History
Thermal depolymerization, also known as thermal conversion, is similar to the geological processes that produced the fossil fuels used today, except that the technological process occurs in a timeframe measured in hours. Until recently, the human-designed processes were not efficient enough to serve as a practical source of fuel—more energy was required than was produced.
Many previous methods which create hydrocarbons through depolymerization used dry materials (or anhydrous pyrolysis), which requires expending a lot of energy to remove water. However, there has been work done on hydrous pyrolysis methods, in which the depolymerization takes place with the materials in water. In U. S. patent 2,177,557, issued in 1939, Bergstrom and Cederquist discuss a method for obtaining oil from wood in which the wood is heated under pressure in water with a significant amount of calcium hydroxide added to the mixture. In the early 1970's Herbert R. Appell and coworkers worked with hydrous pyrolysis methods, as exemplified by U. S. patent 3,733,255, issued in 1973, which discusses the production of oil from sewer sludge and municipal refuse by heating the material in water under pressure in the presence of carbon monoxide.
An approach that exceeded break-even was developed by Illinois microbiologist Paul Baskis in the 1980s and refined over the next 15 years (see U. S. patent 5,269,947, issued in 1993). The technology was finally developed for commercial use in 1996 by Changing World Technologies. Brian S. Appel (CEO of Changing World Technologies) took the technology in 2001 and expanded and changed it into what is now referred to as TCP and has applied for several patents (see, for example, published patent application US 2004/0192980). A Thermal Depolymerization demonstration plant was completed in 1999 in Philadelphia by Thermal Depolymerization, LLC, and the first full-scale commercial plant was constructed in Carthage, Missouri, about 100 yards (100 m) from ConAgra Foods' massive Butterball turkey plant, where it is expected to process about 200 tons of turkey waste into 500 barrels (21,000 US gallons or 80 m³) of oil per day.
Theory and process
In the method being used by CWT the water improves the heating process and contributes hydrogen from water to the reactions.
The feedstock material is first ground into small chunks, and mixed with water if it is especially dry. It is then fed into a reaction chamber where it is heated to around 250 °C and subjected to 600 lbf/in² (4 MPa) for approximately 15 minutes, after which the pressure is rapidly released to boil off most of the water. The result is a mix of crude hydrocarbons and solid minerals, which are separated out. The hydrocarbons are sent to a second-stage reactor where they are heated to 500 °C, further breaking down the longer chains, and the resulting mix of hydrocarbons is then distilled in a manner similar to conventional oil refining.
Working with turkey offal as the feedstock, the process proved to have yield efficiencies of approximately 85%; in other words, the energy contained in the end products of the process is 85% of the energy contained in the inputs to the process (most notably the energy content of the feedstock, but also including electricity for pumps and natural gas for heating). Alternatively, if one considers the energy content of the feedstock to be free (i.e., waste material from some other process), one could consider the energy efficiency of the process to be 560% (85 units of energy made available for 15 units of energy consumed). The company claims that 15 to 20% of feedstock energy is used to provide energy for the plant. The remaining energy is available in the converted product. Higher efficiencies may be possible with drier and more carbon-rich feedstocks, such as waste plastic.
By comparison, the current processes used to produce ethanol and biodiesel from agricultural sources have energy efficiencies in the 320% range when the energy used to produce the feedstocks is considered (in this case, usually sugar cane, corn, soybeans and the like). As these energy efficiencies include the energy cost to produce the feedstock and the above TDP energy efficiency does not, these values are not directly comparable.
The process breaks down almost all materials that are fed into it. TDP even efficiently breaks down many types of hazardous materials, such as poisons and difficult-to-destroy biological agents such as prions.
Feedstocks and outputs with thermal depolymerization
| Feedstock | Output | Feedstock | Output | Feedstock | Output | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plastic bottles |
|
Turkey offal |
|
Paper (cellulose) |
| ||||||||||||||||||||||||
| Sewage sludge |
|
Medical waste |
|
Tires |
|
Carthage plant products
The yield from one ton of turkey waste is 600 pounds petroleum, 100 pounds butane/methane, and 60 pounds minerals. In addition, the water is recycled back into the system for reuse.
The Carthage, MO plant produces API 40+, a high value crude oil comparable to diesel fuel. It contains light and heavy naphthas, a kerosene, and a gas oil fraction, with essentially no heavy fuel oils, tars, asphaltenes, or waxes present.
| Classification of TDP-40 Oil by PONA [1] | |
|---|---|
| PONA | wt%, D-5443 method |
| Paraffins | 22 % |
| Olefins | 14 % |
| Naphthenes | 3 % |
| Aromatics | 6 % |
| C14/C14+ | 55 % |
| TOTAL | 100 % |
The fixed carbon solids produced by the TDP process have multiple uses as a filter, a fuel source and a fertilizer. It can be used as activated carbon in wastewater treatment, as a fertilizer, or as a fuel similar to coal.
Advantages
The process can break down organic poisons, due to breaking chemical bonds and destroying the molecular shape needed for the poison's activity. It is highly effective at killing pathogens, specifically including prions. It can also safely remove heavy metals from the samples by converting them from their ionized or organometallic forms to their stable oxides which can be safely separated from the other products.
Potential sources of waste inputs
The Environmental Protection Agency estimates that in 2001 there were 229 million tons of municipal solid waste, or 4.4 pounds generated per day per person in the USA. [2] Industrial facilities in the USA create 7.6 billion tons of industrial wastes each year and, as a whole, the USA creates over 12 billion tons of total waste[3].
Limitations
The process only breaks long molecular chains into shorter ones, so small molecules such as carbon dioxide or methane cannot be converted to oil through this process. Neither can thermal depolymerization be used to remove radioactivity from radioactive waste.
Many agricultural and animal wastes could be processed, but many of these are already used as fertilizer, animal feed, and, in some cases, as feedstocks for paper mills or as boiler fuel.
Current status
According to a 2/1/2005 article by Fortune Magazine, the Carthage plant was producing about 400 barrels per day of crude oil. This oil is being refined as No. 2 (a standard grade oil which is used for diesel and residential heating oil) and No. 4 (a lower grade oil used in industrial heating).
Reports in 2004 claimed that the facility was selling products at 10% below the price of equivalent oil, but its production costs were low enough that the plant produced a profit. At the time it was paying for turkey waste. The plant has consumed 270 tons of turkey offal (the full output of the turkey processing plant) and 20 tons of egg production waste daily. In April 2005 the plant was reported to be running at a loss.
Price and design changes
Reports from 2005 summarized some economic setbacks which the Carthage plant encountered since its planning stages. It was thought that concern over mad cow disease would prevent the use of turkey waste and other animal products as cattle feed, and thus this waste would be free. As it turns out, turkey waste may still be used as feed in the United States, so that the facility must purchase that feed stock at a cost of $30 to $40 per ton, adding $15 to $20 per barrel to the cost of the oil. Final cost, as of January 2005, was $80/barrel ($1.90/gal).
The above cost of production also excludes the operating cost of the thermal oxidizer and scrubber added in May 2005 in response to odor complaints (see below).
A biofuel tax credit of roughly $1 per US gallon (26 ¢/L) on production costs was not available because the oil produced did not meet the definition of "biodiesel" according to the relevant American tax legislation. The Energy Policy Act of 2005 specifically added thermal depolymerization to a $1 renewable diesel credit, which became effective at the end of 2005.
Company expansion
The company has explored expansion in California, Pennsylvania, and Virginia, and is presently examining projects in Europe. TDP is also being considered as an alternative means for sewage treatment in the United States. [[2]]
Smell complaints
The pilot plant in Carthage was temporarily shut down due to smell complaints. It was soon restarted when it was discovered that few of the odors were generated by the plant[4]. Furthermore, the plant agreed to install an enhanced thermal oxidizer and to upgrade its air scrubber system under a court order[5]. Since the plant is located only four blocks from the tourist-attracting town center, this has strained relations with the mayor and citizens of Carthage.
According to a company spokeswoman, the plant has received complaints even on days when it is not operating. She also contends that the odors may not have been produced by their facility, which is located near several other agricultural processing plants[6].
As of December 29, 2005, the plant was ordered by the state governor to shut down once again over allegations of foul odors as reported by MSNBC[7].
As of March 7, 2006, the plant has begun limited test runs to validate it has resolved the odor issue.[8].
As of April 22, 2006, the plant is back in operation on a trial basis until July with no new odor complaints.[9]
References
- ^ "A PONA classification of the TDP 40 oil is shown below in Table 2.[..]The oil classification is useful for predicting fuel performance when used in combustion, e.g. as a diesel fuel replacement. The classification is also a useful prediction for fuel refiners or blenders in determining product distribution in a refinery or specialty chemical plant." Converting turkey offal into bio-derived hydrocarbons oil (pdf) (Accessed February 9, 2006)
- ^ "In 2003, U.S. residents, businesses, and institutions produced more than 236 million tons Chart: 2001 Total Waste Generationof MSW[Minicipal solid waste], which is approximately 4.5 pounds of waste per person per day." Municipal Solid Waste - Basic Facts
- ^ "According to an old survey, the Agency estimates that 7.6 billion tons of industrial wastes from 60,000 businesses are generated. Most of these wastes are in the form of waste waters (97%)." Industrial Waste Management - Frequent Questions
- ^ Reported by the Kansas City Star, April 12, 2005. The Kansas City Star website has since archived this article: Kansas City: Search results
- ^ In the circuit court of Jasper country, Missouri, at Carthage
"The company said it has finished installation of a thermal oxidizer and upgraded odor scrubber system that were ordered as part of a consent agreement with the city and the Missouri attorney general's office." City questions RES - ^ "A plant spokeswoman, Julie Gelfand, tells the Pitch that repeated odor complaints have been lodged on days when the plant wasn't in operation or when wind conditions were inconsistent with the complaints." Fowl & Crude
- ^ "A foul-smelling plant that turns turkey byproducts into fuel oil was ordered closed by the governor Wednesday until the company finds a way to clear the air." Turkey-oil plant closed due to foul odors
- ^ "An experimental plant that turns turkey byproducts into fuel oil can resume normal operations for 15 days to test whether new equipment solves a problem with bad smells that prompted the state to shut it down in December. [1]
- ^ "The [Department of Natural Resources] will keep an eye on the plant until July to make sure the smells don't return." No new problems at Carthage Turkey-to-Fuel plant
- Brad Lemley (May 2003). Anything Into Oil. (external link, US$1.00 toll) Discover.
- Brad Lemley (July 2004). Anything Into Oil. (Update) (external link, free for now) Discover.
- Brad Lemley (April 2006). Anything Into Oil. (Further Update) (external link) Discover.
- Yuanhui Zhang, Ph.D., P.E. (PI), Gerald Riskowski, Ph.D., P.E., Ted Funk, Ph.D., P.E. (1999). Thermochemical Conversion of Swine Manure to Produce Fuel and Reduce Waste. University of Illinois.
- Stefan Lovgren (July 2, 2004) Pig Manure Converted to Crude Oil National Geographic write up about the above paper.
- Andrew Kantor (January 22, 2004). CyberSpeak: Killing germs, reducing waste, making oil. USA Today.
- Theo Asir (December 1, 2003). Depolymerization Field Observation Report (observation of Carthage, Missouri plant).
- Mark Kawar (May 9, 2003). From trash to black gold. Omaha World Herald.
- Res-Energy (Accessed 2004). RES Plant Daily Output (PDF, 32.5kb). Renewable Environmental Solutions.
- Fortune Magazine Article (February 2005) update on the Changing World Technologies plant.
- Innovative turkey-to-oil plant eats money, spits out fowl odor, By Karen Dillon, Kansas City Star, 4/12/05. (fee required for archived material)