Thanks again for the reply.

I could be wrong, as it was a long time ago that I worked on bioaerosols, but I think that the maximum emissions are not found in fresh material, but once the windrow has been composting for a while. When you turn it then, you tend to create quite a plume of them.

Thanks Joe! Indeed we are concerned about bioaerosol emissions and therefore ensure that workers wear masks when working with fresh wastes. We have used thermocouples in the past and found that there is a diurnal pattern of temperatures but it is does not oscillate enough to warrant measuring temperatures at a certain time of day. Good idea on sampling only from the outside of the pile. We try to take composite samples from thoughout the pile for microbial analysis and we turn all of our piles now at least 4 times to ensure mixing and speed the decomposition process.

Take care,
Sasha

Dear F H Mughal,

This is Sasha Kramer from SOIL. Thanks so much for your thoughtful questions about our composting operation. I will try to answer them one by one. In terms of documented risks to workers, we do know that the drums of waste are filled with pathogens when first emptied and thus constitute a significant exposure risk to workers. We mitigate this risk by ensuring that all of our team have hygiene training and are provided with appropriate protective equipment which includes gloves, masks and uniforms. The site does not smell except during dumping of the drums. After the dumping the waste is covered with dry carbon material (sugarcane bagas) to prevent flies and odours. Our compost sites in Cap-Haitien and Port-au-Prince are located in the same area as the municipal landfill sites and far from any residential areas, so we do not get complaints from neighbors, though we have had this issue in the past when we had sites closer to residential areas.

Thanks again and please do let us know if you have other questions.

Good work, Sasha. I think batch testing is the only way to go, I'm pleased that you are not just measuring temperatures in the middle of the windrow.

I do think F H Mughal's point above is a good one. There has been much concern in large composting sites about microbial bioaerosol emissions affecting workers, and obviously the major risk in the process is going to be to workers who are directly handling large amounts of sewage sludge.

I don't know how reasonable it is to consider worker exposure to bioaerosols, but it might well be a concern.

edit: and another little point, you could consider using some kind of thermocouple to measure temperatures constantly, as there may well be a diurnal pattern of temperature change in your windrow.

If you are short of resources, of course, taking samples exclusively from the outside of the windrow will give the best indication of die-off throughout the material.

Hi Joe,

This is Sasha Kramer from SOIL. Thanks so much for your excellent question. In response to the first part, we do take temperatures from 3 points in the pile: the middle, 6 inches from an edge and 6 inches from the corner. We have also collaborated with the US Centers for Disease Control and Prevention to test the compost throughout the process for E. coli and Ascaris. You can find the report on our website here: www.oursoil.org/cdc-releases-report-on-soil-composting-process/, the article is also attached below. CDC determined that within 3.5 months both Ascaris and E.coli are killed in the composting process. We also test each batch of compost for E. coli and fecal coliforms in our lab in Cap Haitien using an IDEXX machine. No compost is sold until it tests negative for both indicator organisms. In addition we have tested the compost in several independent laboratories in the Dominican Republic. Finally, we are now working with Gary Anderson's lab at Lawrence Berkeley National Laboratory to look at DNA profiles for microbial communities in the compost over time, we hope this will give us more direct information on pathogen die-off. You can read more about this collaboration at: www.oursoil.org/lawrence-berkeley/ I hope that this answers your question. Please don't hesitate to ask if you would like more information.

Is there any data on the health risk to the workers, working at site; and some information on odours and smell, and complaints from the adjacent localities?

What are the land requirements, relative to the municipal landfills?

F H Mughal

I don't understand how you know the material is safe enough to sell based on temperatures in the middle (which are always going to be hottest) and unshown data regarding pathogens. Surely you could only know that it is safe with batch testing.

After the January 2010 earthquake in Haiti nearly 1.5 million people in the capitol were living in camps without access to sanitation. In response to the crisis, international agencies installed thousands of toilets within weeks. However, the absence of waste treatment facilities in the country further complicated the sanitation response. The first treatment facility constructed post-earthquake was a thermophilic composting site designed to treat the wastes from 20,000 earthquake victims living in
camps. Despite multiple hurricanes, a cholera epidemic, and political unrest, the SOIL composting facilities have treated over 500,000 gallons of human waste in the past three years, converting it to pathogen free compost, over 10,000 gallons of which has been sold for use in agriculture and reforestation projects. The experience of thermophilic composting in Haiti is unique in scale and duration and can have global implications for waste treatment in both emergency and development contexts.