Destruction Technologies Research Articles

The role and value of herbicide-resistant lupins in Western Australian agriculture

Herbicide resistant weeds are having a major impact on Australian agriculture. The most important of these is ryegrass ( Lolium rigidum). In response to this new problem, ‘genetic engineering’ techniques are being used to create new types of ‘transgenic’ lupins which are resistant to non-selective herbicides to which the ryegrass is not resistant. In this study the economic value of such a herbicide-resistant lupin variety is investigated using a multiperiod bioeconomic model. The model represents a common cropping system of Western Australia in which winter crops of wheat and lupins are grown in alternate years. The ryegrass population is modelled as being completely resistant to traditionally-used selective herbicides. The net profits for a wide range of weed control measures (both chemical and non-chemical) used separately and in combination with a transgenic lupin were compared with the current options available to farmers. The best integrated strategy involving a transgenic, glufosinate-resistant lupin was found to have a similar profitability to a system based on current lupin varieties employing paraquat for in-crop spraying. However, if a glyphosate-resistant lupin were to be developed and used in conjunction with technology for physical collection or destruction of weed seeds, it was estimated that farm profits would increase by 33%.

Catalysis-assisted plasma technology for carbon tetrachloride destruction

Catalysis-assisted plasma technology is a new concept developed to decompose carbon tetrachloride (CCl/sub 4/), one of the greenhouse gases. A laboratory-scale plasma reactor used a packed-bed reactor with 1 to 3 mm spherical BaTiO/sub 3/ pellets. One configuration of the system used a two-stage process in which the packed-bed reactor was followed by a 1% Pt/Al/sub 2/O/sub 3/ catalyst reactor. The other configuration employed a unique one-stage catalysis/plasma process in which the BaTiO/sub 3/ pellets were coated by active catalysts such as Co, Cu, Cr, Ni, and V. The power supplies used for these experiments were either a 50 Hz neon transformer or an 18 kHz invertor neon transformer. Experiments were performed to characterize the catalytic plasma reactor performance on CCl/sub 4/ destruction. Special attention was focused on the enhancement of the CCl/sub 4/ destruction and the reduction of byproduct CO production by catalyst selection in the one-stage reactor. >

Pyrolytic destruction of polychlorinated biphenyls in a reductive atmosphere

This paper discusses the development of an innovative technology for the pyrolytic destruction of halogenated hydrocarbons in a reductive environment. The technology developed demonstrated the potential for resource recovery, as reaction products could be commercially used. The process was specifically directed at the dehalogenation of polychlorinated biphenyls (PCBs), a class of chlorinated compounds most difficult to thermally decompose due to the high strength of their carbon-chlorine bonds. PCBs have extensive industrial applications, and are regarded as pollutants of serious environmental concern due to their persistence and insidious health effects. Pyrolysis experiments were conducted under controlled laboratory conditions in batch reactor systems with Aroclor 1254 (a mixture of PCB congeners) to evaluate the process feasibility, and to determine the destruction and removal efficiencies (DREs). The pyrolysis was conducted under a variety of operating conditions to investigate the effect on DREs due to changes in process variables such as reactor residence time, reaction temperature, and reactant (methane) concentration. Under optimal conditions — a residence time of 7 minutes, reaction temperature of 1000°C, and stoichiometric excess methane — a DRE of over 99.999% was achieved. The reaction products were dehalogenated hydrocarbons, hydrogen chloride, and soot. The dehalogenated compounds formed were identified as aliphatic and aromatic hydrocarbons by gas chromatography/mass spectrometry (GC /MS). The study also included a scientific analysis of free-radical reactions and associated mechanisms involved in the decomposition of the halogenated hydrocarbons. Achievement of the highest DREs suggests that the process needs further investigation as a method for dehalogenation of chlorinated hydrocarbons with the potential of product recovery for commercial use.

Destruction of Iron-Complexed Cyanide by Alkaline Hydrolysis

Iron-complexed cyanide compounds are found in various industrial wastes, and are resistant to destruction by conventional technologies used to treat cyanide-bearing wastes. This study evaluated hydrolytic destruction of iron-complexed cyanide in leachates from land disposal of spent carbonanceous material used to line aluminum reduction cells. The investigation showed that iron-cyanide complexes may be hydrolyzed under alkaline conditions at elevated temperatures and pressures, e.g. in the range of 165-180 °C and 100-150 psig. The hydrolysis reaction is apparently first-order with respect to total cyanide. The reaction yields stoichiometric amounts of ammonia and formate, and Fe3O4(s). The rate of the reaction is especially temperature dependent, and for the case of spent potlining leachate, the hydrolysis rate may be estimated by an Arrhenius kinetic expression for hydrolysis of simple cyanide. The rate of the hydrolysis reaction for iron-complexed cyanide is compared to that for other metal-cyanide complexes. It is shown that waste composition may affect the hydrolysis rate, and that the instability of certain metal-cyanide complexes with respect to alkaline chlorination does not correlate with instability with respect to alkaline hydrolysis. Alkaline hydrolysis is an appropriate technology for destruction of iron- and other metal-cyanide compounds in wastes at high concentrations.

EPA To Evaluate New Technologies For Cleaning Up Hazardous Waste

Government agencies and waste treatment companies have begun an ambitious program to rate costs and performances of new technologies to destroy or detoxify hazardous industrial wastes at sites around the country. Data reaped from this program will help future users choose among these technologies for full-scale, final destruction or neutralization of wastes on site. Congress ordered this evaluation program as part of the Comprehensive Environmental Response, Compensation & Liability Act of 1986, the law that reauthorized Superfund. The Environmental Protection Agency must choose and evaluate at least 10 such technologies each fiscal year. Although late passage of the law last year will prevent EPA from completing 10 evaluations in the current fiscal year, the agency will have several projects well under way, as well as a slate of 10 ready to go in fiscal 1988. This year's projects will include incineration and pyrolysis, fixation in unleachable matrices, and destruction by microorganisms. To qualify for t...

The advanced electric reactor: A new technology for hazardous waste destruction

The Advanced Electric Reactor (AER) is a new kind of device intended for the destruction of hazardous wastes. It is capable of a wide range of operating conditions for treatment of solid, liquid or gaseous feed materials. This paper describes the AER, and gives the results of a series of tests on PCBs and CCl 4, as well as of leaching tests on feed and treated materials. The advantages offered by the AER are discussed, and future applications are described.

Irradiation enhancement of biomass conversion

The vast supply of cellulosic agricultural residues and industrial by-products that is produced each year is a prospective resource of biomass suitable for conversion to useful products such as feedstock for the chemicals industry and feedstuffs for the livestock industry. Conversions of such biomass is poor at present, and utilization is inefficient, because of physio-chemical barriers to biological degradation and (or) anti-quality components such as toxicants that restrict biological usages. Improvements in biodegradability of ligno-cellulosic materials have been accomplished by gamma-ray and electron-beam irradiation at intermediate dosage (∼ 50 Mrad; .5 MGy); but applications of the technology have been hampered by questionable interpretations of results. Recent research with organic wastes such as sewage sludge and straw suggests opportunity for important applications of irradiation technology in enhancement of biomass conversion. Data from experiments using irradiated straw as feed for ruminants are presented and discussed in relation to research on prospective usage of sewage products as feed for ruminants. Findings are discussed in regard to prospective applications in industrial fermentation processes. Possible usage of irradiation technology for destruction of toxicants in exotic plants is considered in regard to prospective new feedstuffs.

Management of toxic substances and hazardous wastes.

This paper describes the extent of the hazardous and toxic chemical waste problems in Canada and discusses the management, treatment, and disposal methods commonly used in North America and Europe. The treatment and disposal techniques covered are biological, physical-chemical, incineration technologies, and secure land disposal. Some of the available and emerging technologies for destruction of polychlorinated biphenyls are also described.