An article on treatment of source separated human feces via combined lactic acid fermentation and composting

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  • nadia
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An article on treatment of source separated human feces via combined lactic acid fermentation and composting

Human feces from urine diverting dry toilets can serve as valuable soil conditioners. For a successful agricultural application, an efficient pathogen reduction needs to be ensured, with no negative effects on plants. This study assessed the efficiency of lacto-fermentation combined with thermophilic composting on pathogen removal from human feces and the post-treatment effects on germination and growth of radish (Raphanus sativus) and tomatoes (Lycopersicum esculentum) compared to lacto-fermentation combined with vermi-composting and the control. The NH4/NO3 -N ratio of 3.0 and 3.6, respectively, suggested the obtained compost and vermi-compost was not yet mature. A complete reduction in the concentration of all investigated bacterial indicators (i.e., coliforms, Escherichia coli, Enterococcus faecalis, and Clostridium perfringens) from 5–7 log CFU g¡1 to below detection limit (<3 log CFU/g ) was achieved after lacto-fermentation combined with thermophilic composting. Lacto-fermentation combined with vermi-composting also contributed to pathogen die-off, but coliform bacteria were reduced to only 5 log CFU/g. Fertilization of seeds of radish by compost obtained after lacto-fermentation combined with thermophilic composting led to a higher germination index than by the vermicast obtained by lacto-fermentation and vermicomposting (90% versus 84%). Moreover, significantly bigger average fruit weight and total biomass per tomato plant (p < 0.05) were obtained after compost amendment compared to vermicast or the control. You can download the article to the following link (50 free downloads): www.tandfonline.com/eprint/rwDgWK6X7Uh6UFggdJ9X/full
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  • RossWakelin
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Re: An article on treatment of source separated human feces via combined lactic acid fermentation and composting

Interesting approach.
I have been using a humanure system (not separating urine) for the toilet waste (Throwing in some wood charcoal to ad/absorb nutrients), and bokashi composting for food waste (and throwing in surplus kombucha pellicles from time to time). Recently have been combining the two approaches. Although bokashi talk about "Effective Microorganisms", it seems that it is effectively a lactic acid fermentation,
followed by aerobic curing. So your study is interesting information.

My location (Northern Norway) has lower temperatures than Moldova, which gives advantages and disadvantages. No problem with residual smell, but a long winter with limited activity due to unavoidable freezing. Nevertheless it seems to work (qualitatively), so will start a more systematic monitoring/measuring.
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  • nadia
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Re: An article on treatment of source separated human feces via combined lactic acid fermentation and composting

Dear Ross,
Thanks for your comments. When doing experiments I was very much inspired by the speed of the thermophilic process after lactic acid fermentation. I am interested to further apply combined lactic acid fermentation and thermophilic composting along with urine lactic acid fermentationt in a school with UDDT in Moldova to check if this would work in real field situation. There are many types of organic waste in schools (e.g. kitchen waste, that easily gets spoiled) and also garden waste that could be co-composted with human faeces and toilet paper. This may solve many problems, including the odour, since organic waste is usually burried or damped on the territory of school which is not very pleasant to see or to smell. Of course, one of the limitations for a succesful lactic-acid fermentation is the use of food source for lactic acid bacteria. In the experiments, I have used molasses. However, it seems that press mud can work as well since it is at no cost and even very favorable from the environmental point of view.
An indicator that lacto-fermented waste is good was after seeing the way warthworms were enjoing it. One time I have placed some lacto-fermented waste in a windrow in my garden in order to aerate for feeding Eisenia foetida, but after few days I have realized that the lacto-fermented waste was invaded by the earthworms, which were living there. It is pity I did not take a picture or video on that observation.
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  • Fredineswatini
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  • I am working toward the creation of an NGO in eSwatini (formerly Swaziland) dedicated to building low cost efficient and safe water-less toilet systems in rural and urban areas and creating "humanure" from the collected waste for use in agriculture.
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Re: An article on treatment of source separated human feces via combined lactic acid fermentation and composting

Thanks for the reference Nadia. This is almost the exact approach we are looking to use in our pilot project and the results from this paper are very encouraging.

We are using a 3 stage approach to sanitizing fecal sludge (FS) in both rural and urban environments. Our waste is collected in large 25 liter buckets to which microbial saturated saw dust (we are evaluating EM1 vs lactic acid bacteria) is added after each use , then removed to a safe on site holding area and fermented in the 25l sealed bucket anaerobically for 1-3 months. After this we place the fermented waste into a composting pit for 3-6 months, where we will be looking to raise the temperature to about 60 degrees celcius through thermophillic composting. After this if necessary we will continue with vermi-composting for 1-3 months, but we doubt that will be necessary as all pathogens should have died off with thermophillic composting.

One concern we have is the gasses that will be created in this process both from the fact they could be detrimental to the environment and also that buckets could explode in the holding area. Methane would most likely be created which is a harmful Ghg and I was wondering if anyone had references to studies dealing with the quantities of Ghg created by this anaerobic process using lactic acid bacteria?
The more I learn the less I know but, either wisely or foolishly, I continue.
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  • nadia
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Re: An article on treatment of source separated human feces via combined lactic acid fermentation and composting

Homofermeter lactic acid bactera (LAB) produce lactic acid as a major end product of carbohydrate fermentation. Heterofermenters LAB also produce fermentation end-products as acetic acid, ethanol and CO2.
LAB can be used to reduce methane emission during slurry storage (1). Also LAB are being used as fed-microbial supplements silage innoculants) in ruminant livestock for reducing methane production in ruminants. It is indicated that LAB or their metabolites can shift the rumen fermentation to decrease CH4 production, may inhibit rumen methanogens or inhibit specific rumen bacteria that produce H2 or methyl-containing compounds that are the substrates for methanogenesis (2).

But the potential contribution of LAB to greenhouse gas emissions could be that for example in the case of acidification of slurry, lowering of pH will lead to emission of CO2 from the carbonates which are available in big amount in slurry (3). In addition, the carbon acids can serve as substrates for methanogens. But to my knowledge, there are no comprehensive studies to investigate these issues.

References:
1. www.researchgate.net/publication/3097665...e_from_Brewing_Sugar
2. www.frontiersin.org/articles/10.3389/fmicb.2019.02207/full
3. patentimages.storage.googleapis.com/ee/8...5f85/EP0612704A1.pdf
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