My PhD thesis on lactic acid fermentation of human excreta for agricultural application

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A PhD thesis on lactic acid fermentation of human excreta for agricultural application

The PhD thesis entitled "Lactic acid fermentation of human excreta for agricultural application" was defended at IHE Delft, Institute of Water Education on 29 of September 2017. This thesis is organised into 6 chapters: the introductory part, literature review and 3 research chapters as well as one discussion chapter. The introductory part gives background information of the study topic, scope and outline of the research.

The second chapter is a literature review and describes the main nutrient and resource challenges faced by conventional sanitation, the rate of soil degradation and the loss of organic matter in the soil as well as the need for sustainable build-up of soil organic matter, including the application of combined excreta and biochar, the fertilising value of human excreta as well as advantages and disadvantages of the use of biochar in agriculture. Furthermore, the chapter discusses the challenges related to agricultural reuse of excreta such as hygienization aspects, loss of nutrients, carbon matter and odour issues as well as the potential for lactic acid fermentation to overcome these challenges. The chapter also addresses the limitations of lactic acid fermentation, post-treatment of faeces via thermophilic composting and vermi-composting, the role of biochar supplementation as well as agricultural effects of lacto-fermented excreta.

The third chapter evaluates the efficiency of lactic acid fermentation and thermophilic composting versus lactic acid fermentation and vermi-composting for pathogen removal and the effects on plant germination and growth. The results obtained from this chapter showed that combined lactic acid fermentation with thermophilic composting are more efficient in pathogen removal and plant growth than combined lactic acid fermentation with vermi-composting.

In the fourth chapter, the effects of lacto-fermented faeces and biowaste, supplemented by biochar on soil quality (soil nitrate, phosphorus potassium and humus content, moisture content as well as bulk density) and corn productivity (growth, yield and yield components) was examined in a two year field experiment. A comparison was made with no fertilization, lacto-fermented mix without biochar, stored human faeces, cattle manure, urine as well as nitrogen, phosphorus and potassium mineral fertilizers. The lacto-fermented mix of faeces and bio-waste, supplemented by biochar significantly improved plant height (p < 0.05) compared to all fertilizers during the first production year and compared to the control, stored faeces and vermi-compost during the second year. This fertilizer also achieved a significantly higher corn yield compared to all other fertilizers during the first and second production year, except for the lacto-fermented mix without biochar and the mineral fertilizer, which showed no significant yield difference (p>0.05). It also reduced the bulk density of the soil during both years and increased the soil potassium content during the first production year. The yield components (rows per ear and kernels per ear) were improved significantly when supplied with the lacto-fermented mix of faeces and bio-waste, supplemented by biochar that might have attributed to potential prevention of nitrate leaching in the root zone during dry spells, followed by rain flushes.

Chapter 5 discusses the potential of the improvement of the fertilizing value of urine and the prevention of a pH increase and ammonia loss by urine lactic acid fermentation using low cost LAB inoculum. The results showed that the urine lactic acid fermentation has led to effective acidification to pH < 4 and a reduction by 1/3 of the ammonium content compared to the stored urine. Moreover, lacto-fermented urine reduced twice the perceived odour strength and improved seed germination, thus showing a potentially higher fertilizing effect than untreated, stored urine.

Chapter 6 examines the potential applications of the research results in urine diverting dry toilets (UDDT) in Moldova for the primary and secondary treatment of both the urine and faeces fractions. The aspects on product quality requirements for potential full applications and the input materials are given. Furthermore, an entrepreneurial model is proposed for the application of compost obtained from lactic acid fermentation of faeces, kitchen and garden waste. In this model, nutrient rich, lacto-fermented urine is used for the irrigation of a short rotation copice (willow), grown for heating of schools. Faeces treated via combined lactic acid fermentation and thermophilic composting is applied as growth medium for ornamental plants. Potential revenue streams from sale of products (willow plantation and ornamental plants) are highlighted.

The thesis can be downloaded from the website
www.un-ihe.org/news/ms-nadejda-andreev-awarded-doctoral-degree

A hard copy of the book can be ordered at
www.crcpress.com/Lacto-Fermentation-of-H...p/book/9781138049895
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  • F H Mughal
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Re: A PhD thesis on lactic acid fermentation of human excreta for agricultural application

Dear Ms. Nadejda Andreev,

Congratulations to you for achieving your Doctoral degree, and for producing excellent and robust dissertation! I notice that you defended your dissertation just a week back, which shows your rightfully-deserved enthusiasm and zeal!!:)

Just a few minor points for you to respond:

• The field work was carried out in village Boldurești, Nisporeni district (Moldova). What are the average day time temperatures during summer and winter in Bolduresti?
• You say: “When lactic acid fermentation is combined with thermophilic composting with addition of biochar…” Was mesophilic temperature range attempted at?
• Composting is an aerobic process. You used the words “passive aeration.” Could you kindly define passive aeration, in this particular context?
• What would be the cost of producing soil conditioner – say 10 kg of soil conditioner.
• Moving on, how do you intend to utilize your hard work and valuable research?


Kind regards,

F H Mughal

F H Mughal (Mr.)
Karachi, Pakistan
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  • nadia
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Re: A PhD thesis on lactic acid fermentation of human excreta for agricultural application

Dear Mr. Mughal,

Thank you very much for reading the thesis. Here are my answers to your questions:

The field work was carried out in village Boldurești, Nisporeni district (Moldova). What are the average day time temperatures during summer and winter in Bolduresti?

The average day time temperature during summer and winter in Nisporeni district, where the village Bolduresti is located is reflected in Chapter 4, table 4.1, p.74. During summer the average minimum is 13 and average of maximum is 29 ° C. During winter the average minimum temperature is - 9 and maximum is approximately 0 ° C.

• You say: “When lactic acid fermentation is combined with thermophilic composting with addition of biochar…” Was mesophilic temperature range attempted at?

When the process included combined lactic acid fermentation and thermophilic composting, the mesophilic temperature was ranging between 28.5 to 39.5 during the first two days in 2013 and 21.3 to 42.7 °C during the first 4 days during 2014. After approximately 7-11 days of thermophilic temperature of 50-70 °C the temperature dropped to mesophilic temperature of 42-46 °C and then gradually to 25-27°C during a period of approximately 11 days. The sanitizing temperature of 55 °C and above was not achieved in the case only thermophilic stage was used without lactic acid fermentation.

• Composting is an aerobic process. You used the words “passive aeration.” Could you kindly define passive aeration, in this particular context?

It is true that composting is an aerobic process. Passive aeration I mean that no turning or mixing is required during composting. What was interesting to see is that I have placed the lacto-fermented material in a metallic box which was a former fridge and the temperature was rising during the 3 rd day already, it was a very intense decomposition going on. The only oxygen that entered there was through opening of the door of the composting reactor. I guess this is related to the substrate which is reach in enzymes released by lactic acid bacteria and also labile carbon from the addition of molasses. Some studies (Haruta et al., 2002) indicate that the symbiotic interactions between aerobic and facultative anaerobic bacteria can speed up considerably the composting process of slowly degradable lignocelluloses. It is an important area for further studies, what is happening during the lacto-fermentation process, what causes the temperature increase so quickly. The mechanisms are not very clear to me.
Haruta, S., Z. Cui, Z. Huang, M. Li, M.Ishii and Y. Igarashi. 2002. Construction of a stable microbial community with
high cellulose-degradation ability. Apply Microbiology Biotechnology, 59: 529-534.

• What would be the cost of producing soil conditioner – say 10 kg of soil conditioner.

Interesting question, thank you. For the moment not easy to say this, since we did not make such calculations. It would probable depend on the availability of waste materials, biochar, molasses. In chapter 6 of the thesis some calculations were made on approximate cost of urine lactic acid fermentation it is approximately 3 euro per ton of urine. It would be probable profitable is we use lactic acid fermentation for obtaining of urine bio-fertiliser and compost, considering the much higher quantity of urine.

• Moving on, how do you intend to utilize your hard work and valuable research?

I would love very much to apply the results in urine diverting dry toilets in Moldova. And try some entrepreneurial models with fertilization of willow and growing of decorative bushes using fecal derived compost and lacto-fermented urine.
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Re: A PhD thesis on lactic acid fermentation of human excreta for agricultural application

Dear Ms. Nadejda Andreev,

Thank you for providing a useful and enlightened response. I was happy to read it. You have made an innovative use of fridge!!:)

While the soft copy is for free, the hard copy has been priced at GBP 69.99. Such a useful research work like this should have been priced at a lower cost; but then, I understand, the printing costs are high these days.

Anyway, I wish you good luck and success in your future endeavors and research work.

Best wishes,

F H Mughal

F H Mughal (Mr.)
Karachi, Pakistan
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