2015 Excellence in Environmental Engineering and Science™ Competition Winner

E3S Superior Achievement Award

2015 Superior Achievement Award Winner

Bioconversion of Wastes (Wastewater Sludge, Glycerol) to Biodiesel

Entrant: Institut national de la recherche scientifique, INRS-ETE, University of Québec, Canada
Engineers in Charge: R.D. Tyagi, Ph.D, and Rao Y. Surampalli, Ph.D., P.E., BCEE
Location: Quebec, Canada
Media Contact: Dr. R.D. Tyagi, 418.654.2617

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Entrant Profile

Tyagi R.D.: Ph.D. (Biochemical Engineering), Professor and Canada Research Chair, INRS- ETE, Quebec University, Academician of European Academy of Sciences and Arts. 'International Water Association' Specialist medal for outstanding research contribution. Honored with four ASCE awards (2 'State of ART Awards'; 'Wesley Horner Award' and 'Rudolph Hering Medal'. He has over 30 years of experience in advances environmental biotechnology by creating high value-added products from wastewater sludge, he has 9 patents, more than 500 scientific publications, 9 books and 95 book chapters. Currently supervising 10 Ph.D, 3 M.Sc, and 4 Research associates.

Surampalli R.Y.: Ph.D degrees in environmental engineering from Iowa State Universities, respectively. He is a registered professional engineer and also board certified environmental engineer (BCEE) of the American Academy of Environmental Engineers (AAEE) since 1985. He has more than 450 technical publications, including 12 patents, 11 books, 61 book chapters, more than 200 refereed (peer-reviewed) journal articles more than 200 presentations at national and international conferences, edited 12 refereed conference proceedings, and given over 80 plenary, keynote or invited presentations worldwide.

Yan Song: Ph.D. (Water Science, INRS, University of Quebec). Research Associate.

Zhang Xiaolei: Ph.D. (Water Science, INRS, University of Quebec). Research Associate. BEZAWADA Jyothi, (Water Science, INRS, University of Quebec). Research Associate.

Doctorate students:
AYED Dhouha
RAM Saurabh Kumar
YELLAPU, Sravan Kumar

Project Description

The dramatic increase in demand for transportation fuels and the increase in environmental concerns, coupled with diminishing crude oil reserves, have increased the emphasis on renewable energy. Biodiesel, one of the promising alternative and renewable fuels, has been viewed with increasing interest and its production capacity has been well developed in recent years, and increasing attention has been given to biodiesel production from oleaginous microorganisms as the traditional feedstock (plant oils) is getting unaffordable. However, the economic reports showed that the cost of microbial oil (> 10 $/gal) production is so high to be comparable with plant oils (< 4.5 $/gal). The major cost (greater than 50% of total cost) is from the utilization of raw materials including carbon source and nutrients. Therefore, the biodiesel producers are looking for using cheaper raw materials like renewable resources such as wastewater sludge and/or crude glycerol.

Therefore, there is an urgent need to develop economical and sustainable process for crude glycerol and/or wastewater sludge utilization in order to further facilitate biodiesel production on a commercial scale.

Wastewater sludge is naturally produced in large quantity all over the world. The current solutions of sludge management are incineration, land application, and landfilling, which cause greenhouse gas emissions. Sludge contains abundant nutrients that are essential for the growth of microorganism. The use of wastewater sludge as raw material to cultivate oleaginous microorganisms would reduce the cost of lipid production and mitigate the sludge disposal pressure.

In our project, first, highly active yeast and filamentous fungal strains were isolated from soil/wastewater sludge, then they were used to develop a process for lipids production using crude glycerol and/or wastewater sludge as raw material (sterilized or non-sterilized).

Municipal wastewater sludge (primary, secondary, and mixed) and pulp and paper industrial secondary wastewater sludge were utilized for oleaginous microorganism cultivation to develop a process for lipids production. Suspended solids concentration effect on the lipid accumulation was evaluated. Lipid separated from the microorganisms was converted to biodiesel by transesterification. The biodiesel majorly contained C16 (20%-30%) and C18 (60%-70%). Its composition is similar as the biodiesel converted from animal fats including butter, lard, and tallow. The results showed that 1 tonne of dry sludge produced around 210 kg of biodiesel (≈61 gal). Based on the results, energy balance and GHG emissions of the process were evaluated. One tonne of dry sludge for biodiesel production could bring 4 - 6 GJ of energy gain and 6 -18 tonne of GHG emissions reductions. The cost estimation showed that per gallon of biodiesel produced from sludge was around 3.5 US $, which is comparable with plant oil based biodiesel (4.3 US $/gal) and petro-diesel (3.2 US $/gal). It indicates that per tonne dry sludge which produces around 61 gallons biodiesel creates 213.5 US $. However, it would cost around 100 US $ to disposal per m3 sludge which generally contains 80% water. It equals to that 500 US $ is required to dump one tonne of dry sludge. Sludge utilization for biodiesel production provides environment and cost profits.

During biodiesel production, a by-product called glycerol is generated in a ratio of 100 kg glycerol/per kg biodiesel produced. It is normally mixed with methanol, un-transesterified oil, water, and catalyst, and thus called crude glycerol which has a 30% to 80% of glycerol content w/w. Crude glycerol generation in the process has gradually become an issue due to biodiesel production boom. Purification of crude glycerol is becoming unfavorable due to the rapid decrease of refined glycerol price. Glycerol is simple carbon source and readily to be used by microorganisms. Usage of crude glycerol as carbon source for oleaginous microorganism will create a clean cycle of biodiesel production (crude glycerol → lipid → biodiesel + crude glycerol). In addition, the pressure from crude glycerol management would be greatly reduced.

The addition of crude glycerol to sludge was investigated as medium for oleaginous microorganism cultivation. The biodiesel contained 40% - 45% of C16 w/w and 50% - 60% of C18, which is similar as palm oil based biodiesel. One tonne of dry sludge and one tonne of glycerol produced around 380 kg of biodiesel (112 gal). Assuming that there was 210 kg of biodiesel was from sludge, thus 180 kg of biodiesel was due to the one tonne of glycerol addition. It indicates that the biodiesel yield from glycerol is 0.18 g/g glycerol. It is comparable with the yield of using glycerol synthetic medium (0.19 g/g glycerol) in which chemicals were utilized as nitrogen, phosphorous, and mineral source. It reveals that sludge is an efficient medium for oleaginous microorganism production.

The combination of sludge and crude glycerol in biodiesel production seems to provide more economic advantages than solo sludge utilization.

There is residual biomass generated after lipid separation. With sludge and sludge added glycerol as medium for oleaginous microorganism cultivation, 500 kg and 600 kg residual biomass, respectively, were produced per tonne of sludge utilized. It showed that the sludge quantity is largely reduced after biodiesel production. Even though, the residual biomass has to be dumped, the disposal cost will be reduced by half (50%). In fact, the residual biomass is lipid free but contains nitrogen, phosphorous, and other elements and is good for agricultural plant growth.

Thus, this study provides efficient way of managing the wastewater sludge, and simultaneously generated bio-energy. It reduces waste quantity and decreases the waste handling cost. Experiments were performed in shake flasks, then scaled up to 15 L fermenter and 2000L pilot plant. The performance is stable. In this study, our own lab isolated oleaginous microorganisms were employed for biodiesel production from sludge. Crude glycerol in combination with sludge has also given very good results.

The implications of this highly original research are doubly significant. On one hand, residual biomass and/or by-products from industry (which are normally difficult and expensive to dispose of) can be converted into bio-energy, offers concrete solutions to environmental concerns and on the other hand, the production cost of bio-energy became economic.

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Biodiesel production from lipid accumulated in microorganisms cultivated with wastewater sludge.

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