Compost microorganisms not only convert organic material into humus, but they also degrade toxic chemicals into simpler, benign, organic molecules. These chemicals include gasoline, diesel fuel, jet fuel, oil, grease, wood preservatives, PCBs, coal gasification wastes, refinery wastes, insecticides, herbicides, TNT, and other explosives. (59)
In one experiment in which compost piles were laced with insecticides and herbicides, the insecticide (carbofuran) was completely degraded, and the herbicide (triazine) was 98.6% degraded after 50 days of composting. Soil contaminated with diesel fuel and gasoline was composted, and after 70 days in the compost pile, the total petroleum hydrocarbons were reduced approximately 93%.60 Soil contaminated with Dicamba herbicide at a level of 3,000 parts per million showed no detectable levels of the toxic contaminant after only 50 days of composting. In the absence of composting, this biodegradation process normally takes years.
Compost also seems to bind lead in soils, making it less likely to be absorbed by living things. One researcher fed lead-contaminated soil to rats, either with compost added, or without. The soil to which compost had been added showed no toxic effects, whereas the soil without compost did exhibit some toxic effects. (61) Compost seems to strongly bind metals and prevent their uptake by both plants and animals, thereby preventing transfer of metals from contaminated soil into the food chain. (62) Plants grown in lead contaminated soil with ten percent compost showed a reduction in lead uptake of 82.6%, compared to plants grown in soil with no compost. (63)
Fungi in compost produce a substance that breaks down petroleum, thereby making it available as food for bacteria.(64) One man who composted a batch of sawdust contaminated with diesel oil said, “We did tests on the compost, and we couldn’t even find the oil!” The compost had apparently “eaten” it all. (65) Fungi also produce enzymes that can be used to replace chlorine in the paper-making process. Researchers in Ireland have discovered that fungi gathered from compost heaps can provide a cheap and organic alternative to toxic chemicals. (66)
Compost has been used in recent years to degrade other toxic chemicals as well. For example, chlorophenol contaminated soil was composted with peat, sawdust, and other organic matter, and after 25 months, the chlorophenol was reduced in [table of microorganisms that remove metals]concentration by 98.73%. Freon contamination was reduced by 94%, PCPs by up to 98%, and TCE by 89-99% in other compost trials.(67) Some of this degradation is due to the efforts of fungi at lower (mesophilic) temperatures.(68)
Some bacteria even have an appetite for uranium. Derek Lovley, a microbiologist, has been working with a strain of bacteria that normally lives 650 feet under the Earth’s surface. These microorganisms will eat, then excrete, uranium. The chemically altered uranium excreta becomes water insoluble as a result of the microbial digestion process, and can consequently be removed from the water it was contaminating (see Table 3.7).(69)
An Austrian farmer claims that the microorganisms he introduces into his fields have prevented his crops from being contaminated by the radiation from Chernobyl, the ill-fated Russian nuclear power plant, which contaminated his neighbor’s fields. Sigfried Lubke sprays his green manure crops with compost-type microorganisms just before plowing them under. This practice has produced a soil rich in humus and teeming with microscopic life. After the Chernobyl disaster, crops from fields in Lubke’s farming area were banned from sale due to high amounts of radioactive cesium contamination. However, when officials tested Lubke’s crops, no trace of cesium could be found. The officials made repeated tests because they couldn’t believe that one farm showed no radioactive contamination while the surrounding farms did. Lubke surmises that the humus just “ate up” the cesium.(70)
Compost is also able to decontaminate soil polluted with TNT from munitions plants. The microorganisms in the compost digest the hydrocarbons in TNT and convert them into carbon dioxide, water, and simple organic molecules. The method of choice for eliminating contaminated soil has thus far been incineration. However, composting costs far less, and yields a material that is valuable (compost), as opposed to incineration, which yields an ash that must itself be disposed of as toxic waste. When the Umatilla Army Depot in Hermiston, Oregon, a Superfund site, composted 15,000 tons of contaminated soil instead of incinerating it, it saved approximately $2.6 million. Although the Umatilla soil was heavily contaminated with TNT and RDX (Royal Demolition Explosives), no explosives could be detected after composting, and the soil was restored to “a better condition than before it was contaminated.” 71 Similar results have been obtained at Seymour Johnson Air Force Base in North Carolina, the Louisiana Army Ammunition Plant, the US Naval Submarine Base in Bangor, Washington, Fort Riley in Kansas, and the Hawthorne Army Depot in Nevada.(72)
The US Army Corps of Engineers estimates that we would save $200 million if composting, instead of incineration, were used to clean up the remaining US munitions sites. The ability of compost to bioremediate toxic chemicals is particularly meaningful when one considers that in the US there are currently 1.5 million underground storage tanks leaking a wide variety of materials into soil, as well as 25,000 Department of Defense sites in need of remediation. In fact, it is estimated that the remediation costs for America’s most polluted sites using standard technology may reach $750 billion, while in Europe the costs could reach $300 to $400 billion.
As promising as compost bioremediation appears, however, it cannot heal all wounds. Heavily chlorinated chemicals show considerable resistance to microbiological biodegradability. Apparently, there are even some things a fungus will spit out.(73) On the other hand, some success has been shown in the bioremediation of PCBs (polychlorinated biphenyls) in composting trials conducted by Michigan State University researchers in 1996. In the best case, PCB loss was in the 40% range. Despite the chlorinated nature of the PCBs, researchers still managed to get quite a few microorganisms to choke the stuff down.(74)
COMPOST CAN FILTER POLLUTED AIR AND WATER
Compost can control odors. Biological filtration systems, called “biofilters,” are used at large-scale composting facilities where exhaust gases are filtered for odor control. The biofilters are composed of layers of organic material such as wood chips, peat, soil, and compost through which the air is drawn in order to remove any contaminants. The microorganisms in the organic material eat the contaminants and convert them into carbon dioxide and water.
In Rockland County, New York, one such biofiltration system can process 82,000 cubic feet of air a minute, and guarantee no detectable odor at or beyond the site property line. Another facility in Portland, Oregon, uses biofilters to remediate aerosol cans prior to disposal. After such remediation, the cans are no longer considered hazardous, and can be disposed of more readily. In this case, a $47,000 savings in hazardous waste disposal costs was realized over a period of 18 months. Vapor Phase Biofilters can maintain a consistent Volatile Organic Compound removal efficiency of 99.6%, which isn’t bad for a bunch of microorganisms.(75) After a year or two, the biofilter is recharged with new organic material, and the old stuff is simply composted or applied to the land.
Compost is also now used to filter stormwater runoff. Compost Stormwater Filters use compost to filter out heavy metals, oil, grease, pesticides, sediment, and fertilizers from stormwater runoff. Such filters can remove over 90% of all solids, 82% to 98% of heavy metals, and 85% of oil and grease, while filtering up to eight cubic feet per second. These Compost Stormwater Filters prevent stormwater contamination from polluting our natural waterways.(76)
Biofilter — used to clean contaminated air
COMPOST DEFENDS PLANTS FROM DISEASES
The composting process can destroy many plant pathogens. Because of this, diseased plant material should be thermophilically composted rather than returned to the land where reinoculation of the disease could occur. The beneficial microorganisms in thermophilic compost directly compete with, inhibit, or kill organisms that cause diseases in plants. Plant pathogens are also eaten by micro-arthropods, such as mites and springtails, which are found in compost.(77)
Compost microorganisms can produce antibiotics which suppress plant diseases. Compost added to soil can also activate disease resistance genes in plants, preparing them for a better defense against plant pathogens. Systemic Acquired Resistance caused by compost in soils allows plants to resist the effects of diseases such as Anthracnose and Pythium root rot in cucumbers. Experiments have shown that when only some of the roots of a plant are in compost amended soil, while the other roots are in diseased soil, the entire plant can still acquire resistance to the disease.(78) Researchers have shown that compost combats chili wilt (Phytophthora) in test plots of chili peppers, and suppresses ashy stem blight in beans, Rhizoctonia root rot in black-eyed peas,(79) Fusarium oxysporum in potted plants, and gummy stem blight and damping off diseases in squash.(80) It is now recognized that the control of root rots with composts can be as effective as synthetic fungicides such as methyl bromide. Only a small percentage of compost microorganisms can, however, induce disease resistance in plants, which again emphasizes the importance of biodiversity in compost.
Compost stormwater filter
Studies in 1968 by researcher Harry Hoitink indicated that compost inhibited the growth of disease-causing microorganisms in greenhouses by adding beneficial microorganisms to the soil. In 1987, he and a team of scientists took out a patent for compost that could reduce or suppress plant diseases caused by three deadly microorganisms: Phytophtora, Pythium, and Fusarium. Growers who used this compost in their planting soil reduced their crop losses from 25-75% to 1% without applying fungicides. The studies suggested that sterile soils could provide optimum breeding conditions for plant disease microorganisms, while a rich diversity of microorganisms in soil, such as that found in compost, would render the soil unfit for the proliferation of disease organisms.(81)
In fact, compost tea has also been demonstrated to have disease-reducing properties in plants. Compost tea is made by soaking mature (but not overly-mature) compost in water for three to twelve days. The tea is then filtered and sprayed on plants undiluted, thereby coating the leaves with live bacteria colonies. When sprayed on red pine seedlings, for example, blight was significantly reduced in severity.(82) Powdery mildew (Uncinula necator) on grapes was very successfully suppressed by compost tea made from cattle manure compost.(83) “Compost teas can be sprayed on crops to coat leaf surfaces and actually occupy the infection sites that could be colonized by disease pathogens,” states one researcher, who adds, “There are a limited number of places on a plant that a disease pathogen can infect, and if those spaces are occupied by beneficial bacteria and fungi, the crop will be resistant to infection.” (84)
Besides helping to control soil diseases, compost attracts earthworms, aids plants in producing growth stimulators, and helps control parasitic nematodes.(85) Compost “biopesticides” are now becoming increasingly effective alternatives to chemical bug killers. These “designer composts” are made by adding certain pest-fighting microorganisms to compost, yielding a compost with a specific pest-killing capacity. Biopesticides must be registered with the US EPA and undergo the same testing as chemical pesticides to determine their effectiveness and degree of public safety.(86)
Finally, composting destroys weed seeds. Researchers observed that after three days in compost at 55°C (131°F), all of the seeds of the eight weed species studied were dead.(87)
COMPOST CAN RECYCLE THE DEAD
Dead animals of all species and sizes can be recycled by composting. Of the 7.3 billion chickens, ducks, and turkeys raised in the US each year, about 37 million die from disease and other natural causes before they’re marketed.88 The dead birds can simply be composted. The composting process not only converts the carcasses to humus which can be returned directly to the farmer’s fields, but it also destroys the pathogens and parasites that may have killed the birds in the first place. It is preferable to compost diseased animals on the farm where they originated rather than transport them elsewhere and risk spreading the disease. A temperature of 55°C maintained for at least three consecutive days maximizes pathogen control.
Composting is considered a simple, economic, environmentally sound, and effective method of managing animal mortalities. Carcasses are buried in, well, a compost pile. The composting process ranges from several days for small birds to six or more months for mature cattle. Generally, the total time required ranges from two to twelve months depending on the size of the animal and other factors such as ambient air temperature (time of year). The rotting carcasses are never buried in the ground where they may pollute groundwater, as is typical when composting is not used. Animal mortality recycling can be accomplished without odors, flies, or scavenging birds or animals.
Originally developed to recycle dead chickens, the animal carcasses that are now composted include full-grown pigs, cattle, and horses, as well as fish, sheep, calves, and other animals. The biological process of composting dead animals is identical to the process of composting any organic material. The carcasses provide nitrogen and moisture, while materials such as sawdust, straw, corn stalks, and paper provide carbon and bulk for air impregnation. The composting can be done in temporary three-sided bins made of straw or hay bales. A layer of absorbent organic material is used to cover the bottom of the bin, acting as a sponge for excess liquids. Large animals are placed back down in the compost, with their abdominal and thoracic cavities opened, and covered with organic material (sawmill sawdust has been shown to be one of the most effective organic materials with which to compost dead animals). After filling the bin with properly prepared animal mortalities, the top is covered with clean organic material that acts as a biofilter for odor control. Although large bones may remain after the composting process, they are easily broken when applied to the soil.(89)
Backyard composters can also make use of this technique. When a small animal has died and the carcass needs to be recycled, simply dig a hole in the top center of the compost pile, deposit the carcass, bury it over with the compost, and cover it all with a clean layer of organic material such as straw, weeds, or hay. You will never see the carcass again. This is also a good way to deal with fish, meat scraps, milk products, and other organic materials that may otherwise be attractive to nuisance animals. However, one should have thermophilic compost in order to do this, and one can greatly increase the likelihood of his or her backyard compost being thermophilic by adding the nitrogen and moisture that humanure provides.
I keep some ducks and chickens on my homestead, and occasionally one of them dies. A little poking around in the compost pile to create a depression in the top, and a plop of the carcass into the hole, and another creature is on the road to reincarnation. We’ve also used this technique regularly for recycling other smaller animal carcasses such as mice, baby chicks, and baby rabbits. After I collect earthworms from my compost pile to go fishing at the local pond, I filet the catch and put it in the freezer for winter consumption. The fish remains go straight into the compost, buried in the same manner as any other animal mortality. We have five outdoor cats, and they wouldn’t be caught dead digging around in thermophilic humanure compost looking for a bite to eat. Nor would our dog – and dogs will eat anything, but not when buried in thermophilic compost.
COMPOST RECYCLES PET MANURES
Can you use dog manure in your compost? I can honestly say that I’ve never tried it, as I do not have a source of dog manure for experimentation (my dog is a free-roaming outdoor dog, and he leaves his scat somewhere out of sight). Numerous people have written to ask me whether pet manures can go into their household compost pile, and I have responded that I don’t know from experience. So I’ve recommended that pet manures be collected in their own separate little compost bins with cover materials such as hay, grass clippings, leaves, weeds, or straw, and perhaps occasionally watered a bit to provide moisture. A double bin system will allow the manures to be collected for quite some time in one bin, then aged for quite some time while the second bin is being filled. What size bin? About the size of a large garbage can, although a larger mass may be necessary in order to spark a thermophilic reaction.
On the other hand, this may be entirely too much bother for most pet owners who are also composters, and you may just want to put pet and human manures into one compost bin. This would certainly be the simpler method. The idea of composting dog manure has been endorsed by J. I. Rodale in the Encyclopedia of Organic Gardening. He states, “Dog manure can be used in the compost heap; in fact it is the richest in phosphorous if the dogs are fed with proper care and given their share of bones.” He advises the use of cover materials similar to the ones I mentioned above, and recommends that the compost bin be made dog-proof, which can be done with straw bales, chicken wire, boards, or fencing.
ONE WAY TO RECYCLE JUNK MAIL
Composting is a solution for junk mail, too. A pilot composting project was started in 1997 in Dallas-Ft. Worth, Texas, where 800 tons of undeliverable bulk mail are generated annually. The mail was ground in a tub grinder, covered with wood chips so it wouldn’t blow away, then mixed with zoo manure, sheep entrails, and discarded fruits and vegetables. The entire works was kept moist and thoroughly mixed. The result – a finished compost “as good as any other compost commercially available.” It grew a nice bunch of tomatoes, too.(90)
What about newspapers in backyard compost? Yes, newspaper will compost, but there are some concerns about newsprint. For one, the glossy pages are covered with a clay that retards composting. For another, the inks can be petroleum-based solvents or oils with pigments containing toxic substances such as chromium, lead and cadmium in both black and colored inks. Pigment for newspaper ink still comes from benzene, toluene, naphthalene, and other benzene ring hydrocarbons which may be quite harmful to human health if accumulated in the food chain. Fortunately, quite a few newspapers today are using soy-based inks instead of petroleum-based inks. If you really want to know about the type of ink in your newspaper, call your newspaper office and ask them. Otherwise, keep the glossy paper or colored pages in your compost to a minimum. Remember, ideally, compost is being made to use for producing human food. One should try to keep the contaminants out of it, if possible.(91)
Wood’s End Laboratory in Maine did some research on composting ground up telephone books and newsprint, which had been used as bedding for dairy cattle. The ink in the paper contained common cancer-causing chemicals, but after composting it with dairy cow manure, the dangerous chemicals were reduced by 98%.(92) So it appears that if you’re using shredded newspaper for bedding under livestock, you should compost it, if for no other reason than to eliminate some of the toxic elements from the newsprint. It’ll probably make acceptable compost too, especially if layered with garbage, manure, and other organic materials.
What about things like sanitary napkins and disposable diapers? Sure, they’ll compost, but they’ll leave strips of plastic throughout your finished compost which are quite unsightly. Of course, that’s OK if you don’t mind picking the strips of plastic out of your compost. Otherwise, use cloth diapers and washable cloth menstrual pads instead.
Toilet paper composts, too. So do the cardboard tubes in the center of the rolls. Unbleached, recycled toilet paper is ideal. Or you can use the old fashioned toilet paper, otherwise known as corncobs. Popcorn cobs work best, they’re softer. Corncobs don’t compost very readily though, so you have a good excuse not to use them. There are other things that don’t compost well: eggshells, bones, hair, and woody stems, to name a few. We throw our eggshells back to our chickens, or into the woodstove. Bones go into the woodstove, or to the cats or dog. Hair goes out to the birds for nests, if not into the compost pile.
Compost professionals have almost fanatically seized upon the idea that wood chips are good for making compost. Nowadays, when novice composters want to begin making compost, the first thing they want to know is where they can get wood chips. In fact, wood chips do NOT compost very well at all, unless ground into fine particles, as in sawdust. Even compost professionals admit that they have to screen out their wood chips after the compost is finished because they didn’t decompose. They insist on using them anyway, because they break up the compost consistency and maintain air spaces in their large masses of organic material. However, a home composter should avoid wood chips and use other bulking materials that degrade more quickly, such as hay, straw, sawdust, and weeds.
Finally, never put woody stemmed plants, such as tree saplings, on your compost pile. I hired a young lad to clear some brush for me one summer and he innocently put the small saplings on my compost pile without me knowing it. Later, I found them networked through the pile like iron reinforcing rods. I’ll bet the lad’s ears were itching that day – I sure had some nasty things to say about him. Fortunately, only Gomer, the compost pile, heard me.
59 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
60 – Haug, Roger T. (1993). The Practical Handbook of Compost Engineering. p. 9. CRC Press, Inc., 2000 Corporate Blvd. N.W., Boca Raton, FL 33431 USA.
61 – US EPA (October 1997). Innovative Uses of Compost – Bioremediation and Pollution Prevention. EPA530-F-97-042.
62 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
63 – Cannon, Charles A., (1997). Life Cycle Analysis and Sustainability Moving Beyond the Three R’s – Reduce, Reuse, and Recycle – to P2R2 – Preserve, Purify, Restore and Remediate. As seen in the 1997 Organic Recovery and Biological Treatment Proceedings, Stentiford, E.I. (ed.). International Conference, Harrogate, United Kingdom. 3-5 September, 1997. P. 253. Available from Stuart Brown, National Compost Development Association, PO Box 4, Grassington, North Yorkshire, BD23 5UR UK (firstname.lastname@example.org).
64 – US EPA (October 1997). Innovative Uses of Compost – Bioremediation and Pollution Prevention. EPA530-F-97-042.
65 – Logan, W.B. (1991). “Rot is Hot.” New York Times Magazine. 9/8/91, Vol. 140, Issue 4871. (p.46).
66 – Compost Fungi Used to Recover Wastepaper. Biocycle, Journal of Composting and Recycling, May 1998. p. 6 (Biocycle World). JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.
67 – Young, Lily Y., and Cerniglia, Carl E. (Eds.) (1995). Microbial Transformation and Degradation of Toxic Organic Chemicals. Pp. 408, 461, and Table 12.5. Wiley-Liss, Inc. 605 Third Avenue, New York, NY 10518-0012.
68 – Palmisano, Anna C. and Barlaz, Morton A. (Eds.) (1996). Microbiology of Solid Waste. P. 127. CRC Press, Inc., 2000 Corporate Blvd., N.W., Boca Raton, FL 33431 USA.
69 – Logan, W.B. (1991). “Rot is Hot.” New York Times Magazine. 9/8/91, Vol. 140, Issue 4871. (p.46).
70 – Lubke, Sigfried. (1989). Interview: All Things Considered in the Wake of the Chernobyl Nuclear Accident. Acres U.S.A. December 1989. (p. 20) [also contact Uta and Sigfried Lubke, A4722 Peuerbach, Untererleinsbach 1, Austria]
71 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
72 – Cannon, Charles A., (1997). Life Cycle Analysis and Sustainability Moving Beyond the Three R’s – Reduce, Reuse, and Recycle – to P2R2 – Preserve, Purify, Restore and Remediate. As seen in the 1997 Organic Recovery and Biological Treatment Proceedings, Stentiford, E.I. (ed.). International Conference, Harrogate, United Kingdom. 3-5 September, 1997. P. 254. Available from Stuart Brown, National Compost Development Association, PO Box 4, Grassington, North Yorkshire, BD23 5UR UK (email@example.com).and Schonberner, Doug (1998). Reclaiming Contaminated Soils, as well as Block, Dave (1998). Composting Breaks Down Explosives. Biocycle, Journal of Composting and Recycling, September 1998, 36-40.
73 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
74 – Block, Dave (1998). Degrading PCB’s Through Composting. Biocycle, Journal of Composting and Recycling, December 1998. p. 45-48. JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.
75 – US EPA (October 1997). Innovative Uses of Compost – Bioremediation and Pollution Prevention. EPA530-F-97-042.
76 – US EPA (October 1997). Innovative Uses of Compost – Bioremediation and Pollution Prevention. EPA530-F-97-042.
77 – Rynk, Robert, ed. (1992). On-Farm Composting Handbook. Northeast Regional Agricultural Engineering Service. Ph: (607) 255-7654. p. 83.
78 – Hoitink, Harry A. J. et al., (1997). Suppression of Root and Foliar Diseases Induced by Composts. As seen in the 1997 Organic Recovery and Biological Treatment Proceedings, Stentiford, E.I. (ed.). International Conference, Harrogate, United Kingdom. 3-5 September, 1997. p. 95.
79 – US EPA (October 1997). Innovative Uses of Compost – Disease Control for Plants and Animals. EPA530-F-97-044.
80 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
81 – Logan, W.B. (1991). “Rot is Hot”. New York Times Magazine. 9/8/91, Vol. 140, Issue 4871. (p.46).
82 – US EPA (1998). An Analysis of Composting as an Environmental Remediation Technology. EPA530-B-98-001, March 1998.
83 – Trankner, Andreas, and Brinton, William (date unknown). Compost Practices for Control of Grape Powdery Mildew (Uncinula necator). Woods End Institute, PO Box 297, Mt. Vernon, Maine 04352 USA.
84 – Quote from Elaine Ingham as reported in: Grobe, Karin (1998). Fine-Tuning the Soil Web. Biocycle, Journal of Composting and Recycling, January 1998. p. 46. JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.
85 – Sides, S. (1991). Compost. Mother Earth News. Issue 127, Aug/Sept 1991 (p.50).
86 – US EPA (October 1997). Innovative Uses of Compost – Disease Control for Plants and Animals. EPA530-F-97-044.
87 – Biocycle, Journal of Composting and Recycling, October 1998. p. 26. JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.
88 – US EPA (October 1997). Innovative Uses of Compost – Disease Control for Plants and Animals. EPA530-F-97-044.
89 – Brodie, Herbert L., and Carr, Lewis E. (1997). Composting Animal Mortality. As seen in the 1997 Organic Recovery and Biological Treatment Proceedings, Stentiford, E.I. (ed.). International Conference, Harrogate, United Kingdom. 3-5 September, 1997. Pp. 155-159.
90 – McKay, Bart (1998). Com-Postal-Ing in Texas. Biocycle, Journal of Composting and Recycling, May 1998. p. 44-46. JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.
91 – Garbage: the Practical Journal for the Environment. May/June 1992, p.66, Old House Journal Corp., 2 Main St., Gloucester, MA 01930.
92 – Logan, W.B. (1991). “Rot is Hot.” New York Times Magazine. 9/8/91, Vol. 140, Issue 4871.
93 – Biocycle, Journal of Composting and Recycling, November 1998. p. 18. JG Press, Inc., 419 State Ave., Emmaus, PA 18049 USA.