Thermophilic composting Microbes tend to specialize in the temperatures they prefer. In California soils and in our bodies mesophiles are most abundant. Pathogens are mesophiles. Between 110°F and 155°F, thermophiles dominate. Above about 160°F dieoff begins. Reliable pathogen kill occurs above 131°F. Heat greatly accelerates microbial efficiency.
Documented outbreaks, CSPI 2006
September 14, 2006 E. coli O157:H7 outbreak announced Nationwide recall of produce packed by Natural Selection Foods More than 200 illnesses Over 100 hospitalized 31 suffer hemolytic uremic syndrome (acute kidney disease) 3 deaths Market drop Spinach 41% - $77,000,000 Salad products 8% Linked to an August 14 spinach harvest in San Benito County A spinach farm located on a cattle ranch The crop was grown organically, but marketed as conventional Had received pelletized chicken compost which received intense scrutiny
E. coli O157:H7 victims Kyle Algood, age 2 NY Times
Compost? Wildlife? Water? Cal Dept Health Services and FDA (March 2007): Compost ruled out
Pathogenic E. coli E. coli O157:H7 waterborne and foodborne outbreaks documented bloody diarrhea may cause acute kidney failure, death Can survive if reintroduced into compost Low infectious dose Other pathogenic E. coli “traveler’s diarrhea” transmitted by contaminated food, water may be minor to severe
November 3, 2006 FDA announces that fresh tomatoes served in restaurants had sickened 183 people in 23 states with Salmonella typhimurium One of four such outbreaks during the period
Salmonella causes diarrhea, fever, cramps hours after infection illness lasts 4-7 days can also cause typhoid fever 40,000 cases reported annually; 1000 deaths annually 0.1% population excretes Salmonella at a given time most common bacterial pathogen in wastewater primarily foodborne (beef, poultry, milk, eggs), but also transmitted by water Arrows indicate Salmonella cells invading pig epithelium
Shigella bacteria causes diarrhea (often bloody), fever, cramps hours after infection illness lasts 5 -7 days infect only humans 18,000 cases reported annually primarily transmitted by direct contact with infected individual also transmitted by contaminated food, water, recreation low infectious dose (~10 organisms) Macrophage infected with Shigella
Giardia protozoan parasite causes diarrhea, abdominal cramps, nausea for 4-6 weeks 1-2 week incubation period transmitted by contaminated food/water can be transmitted from animals to humans antibiotics are available
Cryptosporidium protozoan parasite causes diarrhea, abdominal cramps, slight fever for 1 week 2-10 day incubation period transmitted by contaminated food/water, person-person can be transmitted from animals to humans no antibiotics are available can cause very severe illness in individuals with weakened immune systems
Ascaris Human roundworm 8-12 week incubation period causes digestive and nutritional problems, abdominal pain
Concentrations of Pathogens in Stools of Infected Individuals from Gerba, 1995
Survival in the Environment Depends on: type of microorganism Parasites>viruses> bacteria temperature
Survival of Microorganisms in the Environment
Title 14 – Sampling – 8 weeks Glassy winged sharpshooter eggs, Olive fruit fly larvae Compost sampling No pests lasted more than 14 d No pests survive more than 4 d at the 30 and 100 cm depths. Neither of the pests survived 100 cm after 2 d. Armillaria mellea, Phytophthora cinnamomi, Sclerotinia sclerotiorum, and Tylenchulus semipenetrans S. sclerotiorum survived at the pile surface and at 10, 30, and 100 cm within the pile for the entire 8 weeks in both fresh green waste (FGW) and aged green waste (AGW). A. mellea and T. semipenetrans did not survive more than 2 days in FGW, P. cinnamomi persisted for over 21 days in FGW.
GAP Metrics – Industry standard “Do not use crop treatments that contain raw manure for lettuce or leafy green produce.” “Verify that the time and temperature process…” “Maximize the time interval between the crop treatment application and time to harvest.” “Segregate equipment used for crop treatment applications or use effective means of equipment sanitation before subsequent use.” June 2007
Precautionary Principal Buyer’s attorneys and insurance companies hold influence “Is it possible for compost to vector disease?” “Is compost absolutely necessary to grow crops?” “That’s good. One less thing.”
Title 14 - Sampling Compost sampling 1 composite sample for each 5000 cu yd Composite of 12 samples from different depths Fecal coliforms (<1000 MPN/dry g) Salmonella (<3 MPN/4 g)
Title 14 - Temperature Turned windrow – 5 turns over 14 days at 55ºC Monitored at 12 – 24” Static pile – 3 days at 55ºC with 6 – 12” insulation Monitored at 12 – 18” Daily readings for every 120’ or 200 cu yds
GAP Metrics – Industry standard Follow CIWMB requirements for compost process Requires E. coli O157:H7 analysis
Safety Long track record Not controversial, but regularly investigated Used all over the world without problems Samples do occasionally reveal pathogens Best available alternative Cross-contamination Acute vs. chronic concern
The Seven HACCP Principals (1) Assess hazards (2) Identify reliable safety measures (Critical Control Points) (3) Assign acceptable performance parameters (critical limits) (4) Monitor, (5) Maintain, (6) Verify, and (7) Document program performance.
Critical Control Point (CCP) Identification CCPs are opportunities to eliminate a significant hazard Must be both essential and effective
Urban Yardwaste is a blend of everything green that is disposed of. Yardwaste recycling is mandated Dead plants are disposed of in yardwaste Pathogens reside in dead plants Composting is not necessarily a part of yardwaste recycling Pathogen spread in yardwaste products is a concern.