Thermal depolymerization
From Freepedia
Thermal depolymerization (TDP) is a process for the reduction of complex organic materials (usually waste products of various sorts, often known as biomass) 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.
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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 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.
A new approach that exceeded break-even was developed by Illinois microbiologist Paul Baskis in the 1980s and refined over the next 15 years. The technology was finally developed for commercial use in 1996 by Changing World Technologies. Brian Appel (CEO of Changing World Technologies) took the technology in 2001 and expanded and changed it into TCP and has applied for a patent. 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
Previous methods to create hydrocarbons from depolymerization expend a lot of energy to remove water from the materials. This hydrous pyrolysis method instead uses water to improve the heating process and contribute 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 required to process materials could be supplied by using 15% of the petroleum output. Alternatively, one could consider the energy efficiency of the process to be 560% (85 units of energy produced 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).
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 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Plastic bottles |
| ||||||||
| Turkey offal |
| ||||||||
| Sewage sludge |
| ||||||||
| Medical waste |
|
Carthage plant products
The yield from one ton of turkey waste is 600 pounds petroleum, 100 pounds butane/methane, and 60 pounds minerals.
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 treatement, as a fertilizer, or as a fuel similar to coal.
Limitations
The process only breaks long molecules into shorter ones. Longer molecules are not created, so short molecules such as carbon dioxide or methane can not be converted to oil through this process. Nevertheless, it is interesting that the turkey-processing plant is creating fuel from atmospheric carbon dioxide which was collected by the growing plants which provided food for the turkeys.
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. However, it cannot remove radioactivity from radioactive waste nor can it eliminate toxicity from heavy metals — both would require transmuting elements, which chemical reactions cannot do.
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]
Many agricultural and animal wastes could be processed, but many of these are already used as fertilizer, animal feed, and in some cases as feedstock for papermills or as boiler fuel.
Current status
According to a recent article by Fortune Magazine, the Carthage plant is currently 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 gasoline) 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 becomes effective at the end of 2005.
Company expansion
The company has explored expansion in three states but is presently examining projects in Europe, and is being considered as an alternative means for sewage treatment in the United States.
Smell complaints
The pilot plant in Carthage, Missouri was temporarily shut down due to smell complaints, but was soon restarted when it was discovered that many of the smells were not actually generated by the plant. (reported by the Kansas City Star, April 12, 2005). Furthermore, the plant agreed[4] 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. If it cannot be resolved, this could lead to NIMBYism, making it difficult to implement this technology widely.
Although there were complaints of a "smell" coming from the plant, complaints were still being placed even when the plant wasn't operating. The complaints stopped when the complainers were identified. Investigators are looking into the case believing that the tipsters were biofuel competitors to the TCP plant.
External links
- Changing World Technologies
- Renewable Environmental Solutions
- Discussion of various aspects, including energy efficiency
References
- 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.
- 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.
- 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. (registration required)
