Chemical Education Today
Reports from Other Journals
Research Advances by Angela G. King
Horseradish, Peroxide Mixture May End War of the Noses In 1993, 18% of hog operations had more than 5000 animals, now 53% do. At the same time, more people are moving from the city to rural areas. The confluence of more people and more pigs has sparked a slew of complaints and much litigation. In 2004, for instance, a state appeals court in Nebraska, a major pork-producing state, ruled that a hog farm must compensate its neighbors for enduring smells some described as “a suffocating stench.” In response to complaints, the $50 billion industry that employs 800,000 people nationwide has tried—with mixed results—various solutions including building windbreak walls, pumping the manure directly into the ground, and adding manure-eating bacteria to the waste. “The problem of odors from farm manure has never been solved. Yet it is a problem that needs to be addressed given the strain it puts on the increasing number of people living
nearby,” says Jerzy Dec, a senior research associate at Penn State University. “Our new approach is a very simple method that doesn’t really take a lot of time, money, or effort to do.” In laboratory studies, Dec and his colleagues mixed horseradish root—purchased at a vegetable market—with hydrogen peroxide or calcium peroxide. Horseradish root contains large amounts of peroxidase, an enzyme that when combined with peroxide destroys phenols, a common source of odors in manure, through oxidative coupling. This approach had previously been applied to treatment of industrial wastewater. Additionally, researchers evaluated how well the system reduced the concentration of volatile fatty acids (VFAs), indole and skatole, compounds that are also associated with the stink of animal manure. The enzymatic deodorizer was tested by adding 3 g of minced horseradish roots and H2O2 or CaO2 to 30 mL of swine slurry. After two hours the samples were assayed. A panel of six trained odor evaluators randomly sniffed treated and untreated manure samples. Overall, the panelists found the samples treated with the horseradish mixture had odors about 50% less intense than untreated ones. Chemical analysis was carried out through gas chromatography of the treated slurry extracts. GC indicated the deodorizing effects lasted for at least 72 hours, although the enzymatic system only removed phenolic odorants from the slurry. This indicates that there is a direct correlation between the concentration of phenolic compounds in swine slurry and the odor intensity and unpleasantness. In pilot-scale tests, the horseradish mixture effectively deodorized more than 50 gallons of hog manure, Dec says. Larger tests are planned. Dec suspects the mixture will also work well on other animal waste. Although the researchers used horseradish root, they believe other plants that are good sources of peroxidase, such as potatoes, white radish roots, and soybean hulls, could be used.
More Information
Figure 1. Odor intensity (top graph) and pleasantness (bottom graph) of swine slurry samples 2 h after treatment. NoHR&HP = untreated control; HR = horseradish only; HP = hydrogen peroxide only; HR&HP = full treatment. Reprinted with permission from J. Agric. Food Chem. 2005, 53, 4880–4889. Copyright 2005 American Chemical Society.
1594
Journal of Chemical Education
•
1. Govere, Ephraim M.; Tonegawa, Masami; Bruns, Mary Ann; Wheeler, Eileen F.; Heinemann, Paul H.; Kephart, Kenneth B.; Dec, Jerzy. Deodorization of Swine Manure Using Minced Horseradish Roots and Peroxides. J. Agric. Food Chem. 2005, 53, 4880–4889. 2. This enzyme can be used in a general chemistry kinetics lab. See Hamilton, Todd M.; Dobie-Galuska, A. A.; Wietstock, S. M. The o-Phenylenediamine–Horseradish Peroxidase System: Enzyme Kinetics in the General Chemistry Laboratory. J. Chem. Educ. 1999, 76, 642–644. 3. Other applications have been covered in this Journal. See Rob, Abdul; Ball, Andrew S.; Tuncer, Munir; Wilson, Michael T. Novel Applications of Peroxidase. J. Chem. Educ. 1997, 74, 212. 4. The safety of hydrogen peroxide has been described in this Journal. Young, Jay A. Hydrogen Peroxide, 3%. J. Chem. Educ. 2003, 80, 1132.
Vol. 82 No. 11 November 2005
•
www.JCE.DivCHED.org
Chemical Education Today
Reports from Other Journals 5. Additional information on the size and impact of the hog industry can be found in the most recent report of the National Pork Producers Council at http://www.nppc.org/about/ pork_today.html (accessed Sep 2005).
Even Low Levels of Benzene Are Hemotoxic When humans are exposed to benzene, it is mainly absorbed through the lungs. While 40% of the absorbed portion is exhaled unchanged, 24 hours after inhalation benzene can still be detected in exhaled air. For over a hundred years, scientists have known that chronic benzene exposure leads to a wide range of medical ailments, including anemia, lymphopenia and transitory leukocytosis. There is also a causal relationship between chronic benzene exposure and lung cancer. Now researchers from China and the United States have collaborated to study the effects of exposure to low levels of benzene. The team measured lymphocyte subsets and colony formation from progenitor cells, and conducted standard blood-count analyses in a large cross-sectional study with detailed exposure assessment. They also studied the effects of genetic variance in enzymes that either metabolize benzene to damaging quinones and free radicals (cytochrome P450E21 and myeloperoxidase) or protect against the resulting molecules (NAD(P)H:quinine oxireductase). The study monitored the individual exposure to benzene and toluene of 250 shoe workers from Tiajin, China, and 140 unexposed age- and sex-matched people from the same region. The subjects’ exposure to aromatic solvents was monitored for a period before phlebotomy and they were divided into four groups based on the measured benzene levels (controls,
