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MY PROJECT
THE FIRST PART

Sewage Energy William Cash November 28, 2010 Submitted as coursework for Physics 240, Stanford University, Fall 2010 Introduction

One of the most popular topics in today's world is finding ways to reduce waste. There is considerable drive to increase recycling, decrease energy consumption, and reduce emissions. However, one form of waste we often ignore is our own human excrement. It's a topic that's often ignored because of taboos, but dealing with human waste is a problem all societies have faced. Failing to remove it properly can often have deadly consequences, as is currently illustrated by the cholera outbreak in Haiti. [1] Thus, significant resources in the forms of money, energy, and manpower are spent on our excrement. Without drastically altering our diets, it's unlikely we'll be alter our biological functions to reduce waste, but there is plenty of unharnessed energy left in our excrement. A significant portion of the energy content of the food we ingest remains after it leaves our bodies, but it is largely ignored in modern waste treatment. This report will explore the possibilities for this untapped energy source. How Much Energy?

A simple theoretical analysis can yield an upper-bound on the amount of energy that can be extracted from human feces. The mass of waste produced depends heavily on the amount of dietary fiber consumed. [2,3] High-fiber diets can produce upwards of four times the wet-stool mass of one deficient in fiber. [3] Age and gender are two other important factors. Adults with a high-fiber diet produce an average of 349 g/day of wet-stool. [3] Thus, a generous estimate of the mass of feces produced by the world's 6.8 billion people is 866 billion kilograms per year. [4] However, only 260 billion kilograms of viable fuel are produced, because water makes up approximately 70% of the stool weight. [5,6] The energy content of dry stool is about 2.3 x 107 J/kg [5]. Thus, a high-fiber population produces 5.98 x 1018 J/year of energy, well short of the 1020 J/year of energy consumed in the world. [7]

Although, we'll never be able to power the world on our own biological waste there is still a significant amount of untapped energy available. In addition, a portion of the world's 1020 J/year is used to treat this waste, but it's hard to estimate how much because the methods of treating the waste vary significantly. In developed nations, centralized plumping transports the waste to large waste-water treatment facilities, but 2.6 billion people still have no form of toilet. [8] About 1% of England's total electricity is spent on wastewater treatment, but in some places excrement can simply be left exposed or even dumped into water sources. [9] Thus, developing methods to harness the energy in feces can benefit both the richest and poorest nations, but the techniques will likely be drastically different. Extracting the Energy

Excrement isn't a fuel you can simply just burn, because it's mostly water. Drying and burning it is possible, but the varied composition of feces will cause poor combustion and numerous emissions. Fortunately, generating methane gas from excrement is a very well understood process. It's used everyday at many wastewater treatment plants and on farms and dairies with animal waste. The waste is broken down by anaerobic bacteria in digester devoid of oxygen. The bacteria feed on the excrement and produce methane gas. This methane is traditionally considered a useless by-product of the digestion process and it is often just burned off. Some wastewater plants use the combustion to heat their facilities and the digester, but the vast bulk of this energy is wasted. This process is very attractive because it can be scaled from individual residences to city-wide networks. Using the Energy

The applications for the generated methane are as varied as the waste treatment procedures around the world. In areas with no centralized plumbing, individual or community digesters are ideal. Not having an existing infrastructure means the systems can be designed to optimize digestion efficiency. The small amounts of methane produced can be used for cooking and heating, as is already being done with some community kitchens in Africa. [10]

Not everyone has been quite as wasteful with the methane produced. Farms around the world are using their animal waste to power their facilities and even sell electricity back to the grid. [11] One might be tempted to combine human waste with food and animal waste treatment digesters, but this should only be done if proper precautions for handling human waste are applied.

Developed nations with centralized plumbing will have to work within the constraints of these systems. A large portion of the clean water consumed (e.g. 30% in the United States) is used for toilets. [12]Unfortunately, a large amount of energy is consumed cleaning and transporting this water, and it's entirely unfeasible to overhaul these infrastructures. Thus, in developed nations the best place to extract some energy is at existing waste treatment facilities.

The quantity of methane produced at these plants is significant enough to be used to generate electricity on a large-scale and cities are beginning to see the value in this. The city of Cleveland is currently constructing a steam-powered electricity plant at it's wastewater treatment facility. The plant will be able to produce 25% of its total electricity demand and expects to pay off the investment in 11 years. [13] San Antonio and San Diego have plans to pipe the collected methane and sell it to utility companies. [12,14] New York City is currently seeking proposals for how to efficiently dispose of its waste for the next twenty years. [15]

Burning methane isn't the only option. The methane can be used to generate hydrogen for fuel cells. A pilot program in California is currently creating enough to fuel 50 cars per day. [12] Disposing of human waste in space has always been a problem. It's currently hauled back to earth at an enormous cost. The first United Nations' satellite is going to test the possibility of generating hydrogen from human waste in space when it launches in 2011. [16] Conclusions

The waste our bodies produce doesn't have to be a significant strain on our already limited resources. Harnessing it as a renewable energy source can also improve sanitation and reduce water pollution throughout the world. It's not a solution to the world energy problem, but the technology already exists and it is being shown to be economically feasible in a variety of situations.

© William Cash. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author. References

[1] S. Tuttle, "Another Way to Die," Newsweek, 8 Nov 10.

[2] D. P. Burkitt, A. R. P. Walker and N. S. Painter, "Effect of Dietary Fibre on Stools and Transit Times and Its Role in the Causation of Disease," Lancet 300, No. 7792, 1408 (1972).

[3] S. M. K Hosseini-Assal and S. D Hosseini. "Determination of the Mean Daily Stool Weight, Frequency of Defecation and Bowel Transit Time: Assessment of 1000 Healthy Subjects," Archives of Iranian Medicine. 3, No. 4, 204 (2000).

[4] "World Development Indicators," The World Bank.

[5] J. L. Murphy et al., "Variability of Fecal Energy Content Measured in Healthy Women," Am. J. of Clinical Nutrition. 58, 137 (1993).

[6] J. B. Wyman et al., "The Effect on Intestinal Transit and the Feces of Raw and Cooked Bran in Different Doses," Am. J. of Clinical Nutrition. 29, 1474 (1976).

[7] "International Energy Annual, U.S. Energy Information Administration.

[8] C. T. Pope, "Rose George's World of Human Waste and Why It Matters," Circle of Blue, 24 Nov 08.

[9] "Energy and Sewage," U.K. Parliamentary Office of Science and Technology, Postnote 282, April 2007.

[10] T. Rosenberg, "Green Strategies for the Poorest," New York Times, 19 Nov 10.

[11] E. Barclay, China Turns to Biogas to Ease Impact of Factory Farms," Yale Environment 360, 11 Nov 10.

[12] L. R. Harrison, "Taking the 'Waste' Out of Human Waste," Chicago Tribune, 3 Nov 10.

[13] M. Scott, "Sewage Turned to Power: Treatment Plant's Incinerators Will Generate Electricity," cleveland.com, 8 Nov 10.

[14] O. R. Soto, "SDG&E Proposes Piping Methane Gas from Waste," SignOn San Diego, 23 Nov 10.

[15] E. S. Rueb, "Turn Piles of Waste Into Piles of Cash, City Asks," New York Times, 5 Nov 10.

[16] J. Welsh, "In the Glorious Future, Could Space Travel Be Poop-Powered?," Discover, 18 Nov 2010.

Journal of Analytical and Applied Pyrolysis

Volume 94, March 2012, Pages 99–107 Cover image Pyrolysis of waste materials using TGA-MS and TGA-FTIR as complementary characterisation techniques

Surjit Singh, Chunfei Wu, Paul T. WilliamsCorresponding author contact information, E-mail the corresponding author

Energy Research Institute, The University of Leeds, Leeds LS2 9JT, UK

Abstract

Pyrolysis of waste materials, biomass wood waste, waste tyre, refuse derived fuel (RDF) and waste plastic was performed using two thermogravimetric analysers (TGA). One TGA was coupled to a mass spectrometer (MS) and the other to an infrared spectrometer (FTIR). The kinetic parameters of the pyrolysed waste materials obtained for TGA-MS and TGA-FTIR were compared using a model based on first-order reactions with a distribution of the activation energies. A further comparison of the volatile species evolved by thermal degradation (TGA) and the subsequent characterisation by the MS and FTIR spectra was performed. The first-order reaction pathways and subsequent activation energies calculated from the differential TGA data presented good repeatability between the TGA-MS and TGA-FTIR. The TGA-MS and TGA-FTIR produced a broad spectrum of qualitative data characterising the volatile gaseous fraction of the waste materials pyrolysed. TGA-MS and TGA-FTIR are shown to be valuable techniques in corroborating the respective thermograms and spectrograms of the volatile species evolved during the pyrolysis of waste materials. However both techniques are prone to interference and careful interpretation of the spectra produced is required. Highlights

► Analytical pyrolysis of wastes using TGA-MS and TGA-FTIR techniques are compared. ► TGA-MS and TGA-FTIR produced a broad spectrum of qualitative data. ► Kinetic parameters determined by TGA-MS and TGA-FTIR show good comparability. ► Careful interpretation of the complex TGA-MS and TGA-FTIR spectra is required. Keywords

Pyrolysis; Waste; TGA-MS/TGA-FTIR; Thermal de-volatilisation; Kinetics

1. Introduction

Waste streams produced from anthropogenic activities in the form of plastic, biomass residue, tyre rubber and refuse derived fuel (RDF) present a major environmental problem. Traditionally the destruction of these wastes via incineration and landfill deposition were regarded as the preferred treatment options. However the worlds reliance on the ever decreasing resources of fossil fuel energy and global awareness in the rise of pollutant emissions particularly carbon dioxide (CO2) has led to more stringent environmental legislation.

Thermogravimetric analysis (TGA) is a well established method in the determination of the weight loss characteristics and its associated reaction kinetics. Pyrolysis thermogravimetric analysis involves the thermal degradation of the sample (typically ∼5–20 mg sample weight) in an inert atmosphere with simultaneous recording of the loss in weight of the sample as the temperature is raised at a uniform rate. The analysis provides net weight loss, and calculation of kinetic parameters is based on simplifying assumptions which do not necessarily correspond to the complex chemical reactions in the thermal degradation of the waste sample. However, the data provide useful comparisons of reaction parameters such as temperature and heating rate. Thermogravimetric analysis of waste materials has been extensively investigated [1], [2], [3], [4], [5] and [6]. In addition, there has been interest in hyphenated TGA techniques to extract further information in regard to the evolved species from the thermal degradation process of waste pyrolysis using TGA. For example, Zhu et al. [7] used coupled TGA-Fourier transform infra-red spectrometry (TGA-FTIR) to investigate the pyrolysis of medical waste. Yang et al. [8] used TGA-FTIR to investigate oil palm waste and Guintoli et al. [9] also used TGA-FTIR to analyse the products from the pyrolysis of agricultural waste. Ischia et al. [10] used thermogravimetric analysis coupled to a mass spectrometer to investigate the pyrolysis of sewage sludge.

This paper reports the characterisation and assessment of the volatile species evolved during the thermal degradation of several waste materials, biomass wood waste, refuse derived fuel (RDF), waste plastic and waste tyre by use of TGA-FTIR and TGA-MS. The two methods are compared in terms of the use in identifying the volatile species from the pyrolysis of the wastes. 2. Experimental

The refuse derived fuel (RDF) samples used for the experimental work were obtained from Malaysian Nuclear Agency, which have been at first shredded and milled into particles up to 3 mm dimension. The RDF sample is the same as that used by Miskolczi et al. [11]. According to the investigations conducted by Miskolczi et al. [11] the RDF consists of 59.8% plastics, 33.7% papers and other wastes (rice, stems, wood, tin foil and other wastes, from households). The waste tyre rubber used in this present study has previously been investigated [12] and was supplied by SRC Ltd. (Cheshire, UK) in pre-sieved size ranges (<250 μm). The method used was ambient shredding which involves chopping the waste tyre rubber (WTR) by rotating knives followed by sieving to get the required range for our experiments. The biomass (pine wood waste) was sourced from Liverpool Wood Pellets Ltd. (Liverpool, UK). The biomass was supplied in the form of pellets of approximately 12–20 mm in length with a diameter of 10 mm. The pine wood waste pellets were produced by compressing saw dust. The waste plastic used in this present study was derived from post-consumer municipal solid waste (MSWP). The MSWP was collected, sorted, fractionated and sourced from the Fost Plus Company (Belgium). The collected MSWP fraction was flaked to approximately 5 mm size range and was separated into a low density fraction through air separation. This lower density fraction was used in this research. The Fost Plus plastic consists of mainly high density polyethylene and polyethylene terephthalate [13].

The pyrolysis (thermal decomposition) of biomass (pine wood waste), refuse derived fuel (RDF), waste plastic and waste tyre were studied by means of thermogravimetric analysis (TGA) coupled to a Fourier transform infrared spectrometer (FTIR) and a TGA coupled to a mass spectrometer (MS). A Shimadzu TGA-50H thermo-gravimetric analyser (TGA) interfaced with a Nicolet Magna IR-560 (FTIR) and a Mettler Toledo DSC-1 Star (TGA)-Thermostar in series with a mass spectrometer (MS) were the instruments employed for this pyrolysis study. A solid sample of approximately 15–20 mg was placed within a small alumina sample basket with a circular base (6 mm diameter and 3 mm height) for both the TGA-MS and TGA-FTIR. The thermo-balance was provided with an electric oven that can operate up to 1500 °C by a temperature controller. A thermocouple was located close to the alumina sample basket for temperature monitoring and for oven control. The solid weight loss, together with other process variables such as temperature, and gaseous species detected by the MS and FTIR respectively were continuously monitored.

The pyrolysis program for the thermogravimetric analysis of the waste materials was identical for both the TGA-MS and TGA-FTIR. The initial heating rate was set at 25 °C min−1 up to a temperature of 110 °C under nitrogen for the TGA-MS and a helium atmosphere for the TGA-MS with a hold time of 10 min respectively. The proximate and ultimate analysis of the waste materials is presented in Table 1. The heating rate was then increased to 900 °C at 25 °C min−1 and held at 900 °C for 10 min. The gaseous phase volatiles released in the TGA from the thermal degradation of waste materials were transferred via a heated line that was interfaced to either the MS or FTIR. The MS was operated under a vacuum and detected the characteristic fragment ion intensity of the volatiles according to their respective mass to charge ratios (m/z). The FTIR operates by the volatile gases passing into a cuvette, where they are exposed to a source of IR light. The IR light is separated into different wavelengths by a modulator. A detector measures the absorption of light at different wavelengths within the IR region by the characteristic functional groups present within the volatile species. Fig. 1 illustrates the experimental system for both TGA-MS and TGA-FTIR.

Table 1. Proximate and ultimate analysis and heating values of the waste materials. Material	HHV (MJ kg−1)	Carbon (%)	Hydrogen (%)	Nitrogen (%)	Sulphur (%)	Oxygen (%)	Moisture (%)	Ash (%)	Volatiles (%)	Fixed Carbon (%) Waste tyre rubber (WTR)	36	77.6	7	0.43	1.4	7.7	0.2	8.3	71.5	28.5 Biomass (Pine wood waste)	27	69.2	3.9	1.7	0.6	5.8	2.9	15.7	30.3	69.7 Refuse derived fuel (RDF)	29	58.5	21.5	0.5	0.1	19.5	4.1	15.5	80.4	19.6 Municipal solid waste plastic (MSWP)	45	77.1	11.5	0.2	0.0	11.2	0	0.0	100.0	0.0 Table options

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Fig. 1. TGA-MS and TGA-FTIR experimental arrangement. Figure options

The thermogravimetric analysers were used to determine the kinetic parameters of the thermal degradation of the waste materials. The integral method (Coats and Redferm integral method [14]) was used to study the activation energy of the non-isothermal degradation of hydrocarbon samples. A detailed description of processing using non-isothermal kinetic data by using a modified Coats–Redfern method has been presented as following:

The basic kinetic equation is: equation(1) View the MathML source Turn MathJax on where α is the conversion of the waste material, defined as following: equation(2) View the MathML source Turn MathJax on where m0 is the initial sample weight, m is the sample weight at time t, and m∞ is the final sample weight.

The reaction rate constant, k is given by the Arrhenius equation: equation(3) View the MathML source Turn MathJax on where A is pre-exponential factor (min−1); E is apparent activation energy (kJ mol−1); T is reaction temperature (K); R is gas constant, it equals to 8.314 × 10−3 kJ mol−1 K−1.

The reaction temperature can be expressed with: equation(4) T=T0+β⋅t Turn MathJax on where T0 is the initial temperature (K) and β is the heating rate (K min−1).

Eq. (1) is changed as follows: equation(5) View the MathML source Turn MathJax on f(α) is presented as: equation(6) f(α)=n(1−α) Turn MathJax on where n is the reaction order.

A combination of Eqs. (5) and (6), with the further integration, it becomes: equation(7) View the MathML source Turn MathJax on because View the MathML source, Eq. (7) can be reduced to: equation(8) View the MathML source Turn MathJax on The left side of Eq. (8) can be plotted against 1/T from which the slope of the straight line is activation energy (E). In this work, a reaction order of n = 1.0 was used to calculate the kinetic parameters, since a first order reaction model matches well with the experimental data as reported by other researchers [15], [16] and [17].

3. Results and discussion 3.1. TGA results

The thermograms representing the derivative weight loss (mg °C−1) for the TGA-MS (Fig. 2A–D) and TGA-FTIR (Fig. 3A–D) show good repeatability. The mass loss rates of the waste materials show a similar trend under the same pyrolysing heating rates employed for both TGA-MS and TGA-FTIR, as is to be expected. The TGA-MS and TGA-FTIR thermograms for the WTR show major thermal events occurring approximately between 230 and 470 °C, with the respective peaks of weight loss at ∼375 and 437 °C. Waste RDF presents three thermal events with the first observed between 0 and 100 °C, this peak is indicative of the inherent moisture within the waste material being released. The proceeding peak is the most significant of the three representing the greatest weight loss (240–380 °C), this is followed by a smaller peak at a temperature between 400 and 500 °C. The biomass both exhibit a single peak denoting thermal decomposition at the temperature ranges of 400–500 °C and 200–400 °C, respectively. The waste plastic exhibits thermal decomposition denoted by the two temperature peaks of ∼300 °C and ∼470 °C respectively. The biomass residue presents a single peak of weight at the temperature range of 200–400 °C. The thermograms in Fig. 3B (biomass) and D (RDF) show a similar final mass to the thermograms in Fig. 2B (biomass) and D (RDF). The final masses for the biomass are presented as ∼5.6 mg (Fig. 2B) and ∼4.8 mg (Fig. 3B). The final masses for RDF are ∼5.8 mg (Fig. 2D) and ∼5.5 mg (Fig. 3D) respectively. This further demonstrates good repeatability between the TGA instruments Shimadzu TGA-50H-FTIR (Fig. 2A–D) and Mettler Toledo Star TGA DSC-1-MS (Fig. 3A–D). Researchers have presented findings that suggest thermal decomposition occurring under pyrolysing conditions for biomass and industrial wastes follows a similar behaviour to that of coal with respect to the volatile species evolved [18], [19], [20], [21] and [22]. Therefore initial thermal decomposition can be broadly seen as a two stage thermal degradation process consisting of primary decomposition and secondary reactions [23]. During the primary steps of decomposition weak aliphatic bonds (non-aromatics) within the fuel matrix are broken. The fragments that do not condense at room temperature undergo further decomposition producing CO2, light aliphatic gases (C2–C5) and H2O. Others [24], [25], [26], [27] and [28] note that the secondary phase of pyrolytic thermal decomposition results in CH4, CO, H2 and light volatile nitrogenous species (NH3, HCN and HiNCO). Hence volatile nitrogen is expected to be present as all the waste samples (waste tyre, RDF, biomass and waste plastics) contain fuel-bound nitrogen. It is noted that the volatile-nitrogen in the form of NH3 and HCN evolved during pyrolysis was not expected to be the most significant gaseous species. Hence, extensive experimental research into the pyrolysis of waste materials by other authors [28], [29] and [30] have shown CO, CO2, H2, H2O and light hydrocarbons (C1–C4) as being the dominant gaseous constituents.

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Fig. 2. TGA-MS thermogram (DTGA (mg °C−1), mass loss (mg) and MS spectrogram (H2■, CH4, NH3, HCN , CO , NO , H2S , CO2). (A) Waste tyre rubber (WTR), (B) biomass, (C) municipal solid waste plastic (MSWP) and (D) refuse derived fuel (RDF).   Figure options

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Fig. 3. TGA-MS thermogram (DTGA (mg °C−1), mass loss (mg) ). (A) Waste tyre rubber (WTR), (B) biomass, (C) municipal solid waste plastic (MSWP) and (D) refuse derived fuel (RDF). Figure options

3.2. Species identification and discussions from TGA-FTIR and TGA-MS

The FTIR spectrum for biomass, RDF, waste tyre and waste plastic display a variety of peaks between the wave numbers of 500–4000 cm−1 (Fig. 4A–D). The initial peaks at 500 cm−1 and the proceeding smaller peaks ranging from 3500 to 4000 cm−1 are characteristic of water and the source is likely to be the inherent moisture within the biomass and RDF waste as reported by other researchers [22], [31], [32] and [33]. Waste tyre rubber and waste plastic do not show significant peaks at 500 cm−1 and 3500–4000 cm−1, suggesting that little moisture is present, as no DTG peaks are observed below 100 °C (Fig. 2 and Fig. 3). Pyrolysis studies carried out by [34], [35], [36], [37] and [38] have also demonstrated little or no presence of inherent moisture within tyre derived rubber.

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Fig. 4. TGA-FTIR thermograms representing absorbance with respect to time (min) and wave number (cm−1). (A) Waste tyre rubber, (B) biomass, (C) municipal solid waste plastic (MSWP) and (D) refuse derived fuel (RDF) (Time 30 min = 325 °C, 50 min = 525 °C, 70 min = 725 °C, 90 min = 900 °C). Figure options

Table 2 displays the absorption bands of the gaseous species detected during the pyrolysis of the waste materials in this present study. Table 2 further presents a comparison between the present pyrolysis study and pyrolysis work conducted by other researchers using TGA-FTIR. It is noted that the pyrolysis of waste materials by other researchers presents CO, CO2, H2O and CH4 as the main gaseous species produced during pyrolysis [22], [31], [32], [33], [39], [40], [41], [42], [43], [44] and [45].

Table 2. Gaseous species characterised according to their wave numbers (cm−1) and functional groups for the present pyrolysis study and historical pyrolysis studies. Reference	Sample	Wave number range (cm−1)	Peak (cm−1)	Species	Functional group	Vibration Present study	Biomass, waste tyre, waste plastic, RDF	2250–2400	2350	CO2	Cdouble bond; length as m-dashO	Stretching Tao et al. [31]	Waste mixtures of paint and tar slag	2400–2260 Han et al. [22]	Wheat–straw	2230–2400, 586–725	2357 Fu et al. [39]	Maize stalk, cotton stalk and rice stalk	2240–2402 Jiang et al. [32]	Dye stuff production waste		2359 Giuntoli et al. [33]	Biomass residue Dry distiller's grains with solubles (DDGS) and chicken manure	2295–2400	2300, 2400 Hardy et al. [40]	Metal-chelate gel	3715, 3615, 2330, 667	2268, 2395 Ferrasse et al. [41]	Sewage sludge		2364

Present study	Biomass, waste plastic	2000–2250	2110, 2200	CO	Csingle bondO	Stretching Tao et al. [31]	Waste mixtures of paint and tar slag	2260, 1990 Han et al. [22]	Wheat-straw	2112, 2181	2181 Fu et al. [39]	Maize stalk, Cotton stalk and Rice stalk	2112, 2181	2181 Jiang et al. [32]	Dye stuff production waste	2174	2177 Giuntoli et al. [33]	Biomass residue Dry distiller's grains with solubles (DDGS) and chicken manure	2100–2250	2110, 2180 Hardy et al. [40]	Metal-chelate gel		2110, 2180 Ferrasse et al. [41]	Sewage sludge		2364

Present study	Biomass, waste tyre, waste plastic, RDF		2930	CH4	Csingle bondH	Stretching Tao et al. [31]	Waste mixtures of paint and tar slag		3014 Han et al. [22]	Wheat-straw		2870 Fu et al. [39]	Maize stalk, Cotton stalk and Rice stalk Jiang et al. [32]	Dye stuff production waste	2800–3100	3014 Giuntoli et al. [33]	Biomass residue Dry distiller's grains with solubles (DDGS) and chicken manure	2800–3200	2900, 3000, 3100 Zhu et al. [7]	Medical waste	3115–2675	2819

Present study	Biomass, waste tyre, waste plastic, RDF	3500–4000		H2O	Osingle bondH	Stretching Tao et al. [31]	Waste mixtures of paint and tar slag	1300–2000, 3500–4000 Han et al. [22]	Wheat-straw	3500–4000	3700 Fu et al. [39]	Maize stalk, Cotton stalk and Rice stalk	3500–4000 Jiang et al. [32]	Dye stuff production waste	3600–4000	3854 Giuntoli et al. [33]	Biomass residue Dry distiller's grains with solubles (DDGS) and chicken manure	3500–4000 Zhu et al. [7]	Medical waste	3500–4000	3566.7 Hardy et al. [40]	Metal-chelate gel	3500 Ferrasse et al. [41]	Sewage sludge		1508

Present study	Biomass, waste tyre, waste plastic, RDF	1600–1900		CH3COOH	Csingle bondO(H) Zhu et al. [7]	Medical waste		1800, 1200 Ferrasse et al. [41]	Sewage sludge		1792, 1799 Marcilla et al. [42]	Ethylene-vinyl acetate co-polymers		3580, 1798, 1381 1175 Hardy et al. [40]	Metal-chelate gel		3580, 1785, 1390, 1270,1180, 1070, 995

Present study	Biomass, waste tyre, waste plastic, RDF		1400, 1745	HCOOH	Csingle bondO(H)	Stretching Han et al. [22]	Wheat-straw		1180 Fu et al. [39]	Maize stalk, Cotton stalk and Rice stalk	900–1900 Yang et al. [43]	Palm oil wastes		1250 Zhu et al. [7]	Medical waste		1800, 1100

Present study	Biomass, waste tyre, waste plastic, RDF		1100, 1300	C6H5OH (Phenol)	Osingle bondH Han et al. [22]	Wheat-straw		1360, 3610 Yang et al. [44]	Hemicellulose, cellulose and lignin		1108 Jang et al. [45]	Bisphenol A polycarbonate		1500, 1597

Present study	Biomass, waste tyre, waste plastic	2900–3000		CH3OH (Methanol)	Osingle bondH Tudorachi et al. [78]	poly(succinimide) and sodium poly(aspartate)		3230 Jiang et al. [32]	Dye stuff production waste		2974,1058 Yang et al. [44]	Hemicellulose, cellulose and lignin	3000–3600 Ferrasse et al. [41]	Sewage sludge		2960 Table options

3.2.1. CO from TGA-FTIR and TGA-MS

CO which is represented by the functional group Csingle bondO at the absorption band between 2240 and 2060 cm−1 (Table 2) was present for only biomass and waste plastic. The Csingle bondO functional group is representative of carbon monoxide as detailed by several authors [22], [31], [32], [33], [39], [40] and [41] (Table 2). It was anticipated that the FTIR spectra should detect CO for RDF and waste tyre. Authors [46], [47], [48] and [49] have observed increased levels of CO with high temperature pyrolysis. It is further suggested that the lack of CO is due to spectral interference from other species present within the waste tyre and RDF.

It has been identified by Bak [50] that H2O, CO2 and N2O can cause distortion in the detection of CO. In contrast the TGA-MS spectrum for waste tyre shows a strong presence of CO only second in its respective intensity to that of NH3 (Fig. 2A). In the case of RDF the CO exhibits the greatest intensity of all the gaseous species evolved (Fig. 4D). Therefore the MS spectrogram for waste tyre and RDF supports the assumption that an absorption peak of CO should be displayed by the FTIR spectra (Fig. 4A and D). The likely source of this interference is thought to be due to the presence of moisture and CO2 in the case of RDF. The absence of the CO IR absorption band between 2000 and 2250 cm−1 (Table 2) for the waste tyre FTIR spectra (Fig. 4A) may be due to spectral interference by CO2 which exhibited IR absorption in the range of 2150–2400 cm−1 for the waste tyre (Table 2). 3.2.2. CO2 from TGA-FTIR and TGA-MS

The waste tyre, RDF, biomass and waste plastics all display absorbance peaks in the region of 2268–2395 cm−1. This is representative of CO2 due to its indicative asymmetric stretching of the carbonyl group (Cdouble bond; length as m-dashO) [7], [22], [32] and [40]. The presence of CH4 and CO2 is observed for all waste samples in the MS and FTIR spectra. It is noted that the CO2 presented by the MS spectra has a considerably lower intensity when compared to CH4, NH3 and CO for all waste samples (Fig. 4A–D). 3.2.3. 2800–3200 cm−1 from TGA-FTIR

Waste tyre shows a strong absorbance peak in the region of 2800–3200 cm−1, biomass is also seen to show a peak within this region, however it is noted that this peak in contrast to waste tyre is considerably smaller. This demonstrates the presence of the functional groups such as acetic acid, formic acid, CH4 toluene and phenol that possess characteristic absorption bands within the region of 2800–3200 cm−1 (Fig. 4A and B, Table 2). 3.2.4. Nitrogen related species from TGA-FTIR and TGA-MS

Fig. 2A–D representing the TGA-MS spectrograms show that the dominant gaseous species in the waste samples are represented by CO and NH3 with HCN being prominent for waste plastic (Fig. 2C). This therefore presents a further confliction between the TGA-FTIR and TGA-MS spectra for the waste samples, because the TGA-FTIR spectra do not show the nitrogenous derivatives of either NH3 or HNC as being present for any of the waste samples.

Literature has further shown that volatile nitrogenous species (NH3, HCN and HiNCO) to be present in significantly lower yields [22], [31], [32], [39], [41] and [42]. It is noted that NH3, HCN and HiNCO may undergo further reduction or oxidation to N2 or NO respectively. However this is dependent on the extent of the limited availability of O2 within the pyrolysing process.

The nitrogen content (wt.%) of the waste samples investigated within this present study ranged from 0.7 to 1.0 (Table 1), this is significantly lower compared to waste materials pyrolysed by others [32], [33] and [51]. Pyrolysis of dyestuff production waste possessed a nitrogen content of 3.39 wt.% [32], however at the pyrolysis temperature of 850 °C the dominant gaseous species determined were CO, CO2 and H2O. In other studies [33] and [50] the pyrolysis of sewage sludge and dry distillers grains with soluble (DDGS) contained nitrogen contents of 6.7 wt.% and 4.5 wt.% respectively. In both studies the yield of gaseous products was composed of the non-condensable gases CO, CO2 and CH4. Domínquez et al. [51] was not able to detect NH3, HCN and HiNCO, whereas Giuntoli et al. [33] observed these species in significantly lower yields to CO, CO2 and CH4. Giuntoli et al. [33] notes that lower temperatures favour the release of NH3, whereas intermediate temperatures (<400 °C) show a greater preference for HiNCO and higher temperatures (>650 °C) resulting in the evolution of HCN. Aylón et al. [38] demonstrated that the pyrolysis of waste tyres results in a gas composed mainly of H2, CO2, CO, N2 and CH4 with the majority of the gaseous species being H2 (30.0 vol.%) and CH4 (23.3 vol.%).

With respect to the TGA-FTIR spectra the present study was not able to detect NH3, HCN and HiNCO in any significant levels revealing a similar trend to previous tyre pyrolysis work [47] and [52]. Buah et al. [3] characterised the products yielded from the pyrolysis of RDF and found the main gaseous products to be CO, CO2, H2 and CH4. Further the main weight loss of RDF occurred in two stages within the lower temperature range of 240–380 °C and higher temperature range of 410–500 °C. Williams et al. [53] pyrolysed waste plastics derived from municipal solid waste (MSW) at a range of temperatures between 500 and 700 °C. The gas analysis showed the presence of H2, N2, CO, CO2, hydrocarbons (C1–C5). Again the gas analysis of the studies by Williams et al. [53] and Buah et al. [3] did not reveal NH3, HCN and HiNCO.

The TGA-FTIR spectra for waste tyre, RDF, biomass and waste plastics does not display characteristic peaks associated with the presence of NH3 at its respective absorption bands of 930, 964, 1623 and 3330 cm−1[40]. It is further seen that the FTIR spectrum detects the presence of cyuranic acid (HiNCO) for the samples of waste biomass and RDF at the absorbance wave number of 2300 cm−1. The detection of HiNCO at 2300 cm−1 is in agreement with previous studies [33] and [34]. However it is also noted that the Cdouble bond; length as m-dashO functional group which absorbs IR at 2300 cm−1 is characteristic of CO2 as well. Therefore based on the low inherent nitrogen content (wt.%) of the waste samples (Table 1), it is probable that the spectrum at 2300 represents both HiNCO and CO2. The FTIR spectrum is limited in providing quantitative information on the respective concentration of HiNCO and CO2.

It suggested that the elevated levels of NH3 and HCN detected by the TGA-MS are not representative. This is based on the following factors such as the thermal decomposition behaviour of volatile nitrogenous species [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28] and [54], pyrolysis studies [1], [2], [3], [11], [12], [13], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52], [53], [55], [56], [57], [58], [59], [60], [61], [62], [63], [64], [65], [66], [67], [68], [69], [70], [71], [72], [73], [74], [75], [76], [77] and [78] and a comparison of TGA-MS and TGA-FTIR spectra for the present study. The error in the TGA-MS spectra is likely to be due to ion interference from other ionic species that possess the same mass to charge ratio (m/z) as NH3 (17). The quadrapole of the mass spectrometer is susceptible to interfering ionic species therefore great care in the analysis of the spectra is required. It is noted that the hydroxyl ions possess the m/z ratio of 17 which is identical to NH3. Therefore it is suggested that the overly high values of NH3 detected by the MS may in fact be due to the hydroxyl ions present within the waste materials. This would explain the distortion of the MS spectra with respect to the compressed levels of the gaseous species H2, CO2 and CH4 normally expected to be the main gaseous products produced [28], [29] and [30]. A likely source of the hydroxyl groups within the waste materials is thought to come from the inherent moisture present, alcohol, alkyl and carboxyl derivatives. This is supported further by the TGA-FTIR spectra (Fig. 4A–D) and historical pyrolysis studies (Table 2) which present characteristic peaks in the wave number range of 4000–3400 cm−1 indicating the presence of water vapour. The dissociation of the moisture present within the waste samples along with the absorption peaks for alcohol, alkyl and carboxyl derivatives as shown in Table 2 provide further sources of the hydroxyl functional group. Thus TGA-MS and TGA-FTIR present to invaluable tools in the characterisation of waste materials. It is noted that careful consideration by the operator is required in order to ascertain credible data from the respective spectrograms produced. 3.3. Kinetics analysis

Activation energy of each sample from non-isothermal analysis by TGA-MS and TGA-FTIR was presented in Table 3 and Table 4 respectively. High correlation was obtained for the calculation of the activation energy, thus a reasonable kinetic results were expected in this work. Similar activation energy for waste tyre, waste plastics and biomass was obtained, while comparing the TGA-MS results with the TGA-FTIR results. However, higher activation energy was obtained for the TGA-MS analysis of the RDF sample. Since the activation energy was 97.8 kJ mol−1 for the RDF degradation by TGA-MS analysis in the temperature range from 240 to 380 °C, while only 63.7 kJ mol−1 was obtained for the TGA-FTIR analysis of the RDF sample (Table 3 and Table 4).

Table 3. Kinetic results from TGA-MS analysis. Material	Temperature range (°C)	Temperature peak (°C)	Maximum rate of weight loss (% °C−1)	Activation energy, E (kJ mol−1)	Correlation coefficient, r   Refuse derived fuel (RDF)	240–380	345	0.137	97.8	0.996 410–500	474	0.042	36.4	0.996

Waste tyre rubber (WTR)	310–410	377	0.120	95.3	0.998 420–500	437	0.057	80.0	0.996

Municipal solid waste plastic (MSWP)	270–360	326	0.014	42.2	0.995 410–500	478	0.497	294.8	0.995

Biomass (Pine wood waste)	220–400	367	0.167	83.9	0.998 Table options

Table 4. Kinetic results from TGA-FTIR analysis. Material	Temperature range (°C)	Temperature peak (°C)	Maximum rate of weight loss (% °C−1)	Activation energy, E (kJ mol−1)	Correlation coefficient, r   Refuse derived fuel (RDF)	240–380	342	0.116	63.7	0.998 410–500	468	0.036	27.4	0.999

Waste tyre rubber (WTR)	310–410	374	0.148	99.3	0.999 420–500	438	0.100	80.7	0.999

Municipal solid waste plastic (MSWP)	270–360	321	0.030	47.4	0.990 410–500	481	0.423	277.9	0.990

Biomass (Pine wood waste)	220–400	361	0.196	83.8	0.999 Table options

As shown in Table 3 and Table 4, the highest weight loss rate (>0.4% °C−1) was found for the degradation of waste plastics at the temperature range of 410–500 °C. Maximum rate of weight loss of biomass was 0.167% °C−1 for TGA-MS analysis and 0.196% °C−1 for the TGA-FTIR analysis, respectively, at the temperature of 220–400 °C. Waste tyre and RDF were found to have similar maximum rate of weight loss (<0.15% °C−1).

The activation energy (around 83.9 kJ mol−1) of the biomass degradation in the non-isothermal TGA analysis was consistent to the results that have been reported by other works [79] and [80], where 85.4 kJ mol−1 of activation energy was reported for the degradation of wood chip and 84.5 kJ mol−1 was reported for the degradation of peanut shell [79] and 88 kJ mol−1 of activation energy was reported for the degradation of bagasse (all the works were carried out by TGA analysis in N2 atmosphere). Similar activation energy for TGA analysis of RDF was reported by Seo et al. [81], where 78.4 kJ mol−1 of activation energy was obtained in the temperature between 224 and 360 °C, and 37.5 kJ mol−1 was reported in the temperature range of 360–455 °C. The result of activation energy for TGA analysis of waste plastics was also in agreement with the reported results [82]. 4. Conclusions

In this present study the pyrolysis of the waste materials biomass, RDF, waste tyre and plastic were pyrolysed by way of a TGA instrument which was interfaced to an FTIR and MS for the detection of the volatile species evolved. The main aim of the study was to determine the information both techniques could provide regarding the pyrolysis of waste materials. TGA-MS and TGA-FTIR have demonstrated to be complementary instruments capable of providing valuable qualitative analysis of the gaseous volatile species evolved during pyrolysis. Both TGA-MS and TGA-FTIR are prone to interference, ionic species with the same m/z ratio and functional groups with similar absorption bands cause spectral overlap respectively. Comparing the spectrograms of the two techniques proved a valuable tool in confirming and corroborating the validity of the results produced. The TGA-FTIR revealed a range of organic species (moisture, carbonyl aromatic and alcohols) containing the hydroxyl functional group. The OH ion has the same m/z ratio as NH3. Therefore it is suggested that the high intensities of NH3 for TGA-MS are due largely to OH interference. The pseudo high intensities of NH3 would explain the relatively lower intensities of H2, CO2 and CH4 presented in the MS spectrogram. The TGA-MS also showed CO as a major constituent during pyrolysis, which is in agreement with previous pyrolysis work. The TGA-MS spectrogram was able to validate the absence of CO within the TGA-FTIR spectra for the waste tyre and RDF is inaccurate and may be due to CO2 and H2O, known interferants that can cause spectral masking of CO. The kinetic parameters obtained for the pyrolysis of the waste materials employing TGA-MS and TGA-FTIR were in complete agreement, validating the pyrolysing conditions used by both TGA instruments. Acknowledgement

We thank the UK Engineering and Physical Sciences research Council (EPSRC) for support for the research via Grant EP/D053110/1 and EP/F021615/1. References

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Project Generating electricity from waste water

The market for new ways to generate sustainable energy is booming.

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In addition to wind and solar energy, the so-called biofuels are becoming increasingly common. Generating energy through burning, vaporising, or fermenting biomass such as leftover plant material, vegetable waste, and manure are well-tried methods. A new shoot on this branch of energy production is the microbial fuel cell, which is capable of directly generating energy from substances such as waste water. At the present time, this has only been done in the lab, but the first results and applications of this new technology are very promising.

If an electrode is placed in waste water, bacteria automatically begin to grow on it. These bacteria are capable of transforming the organic compounds present in the water into electricity. This process purifies the waste water, which in and of itself is a useful application. But researchers from Wageningen UR and Wetsus, a water technology institute, who are working with each other as part of the Microbial Fuel Cell project , are more interested in generating electricity.

They are testing organic materials which may act as catalysts on the process. They are also improving the design of the model to enable generating electricity on a larger scale. How a microbial fuel cell works

A microbial fuel or biofuel cell requires:

Two electrodes Bacteria such as those present in waste water or manure A conducting wire with resistor (such as a light bulb)

One electrode (the anode) is suspended in the waste water and connected by means of conducting wire to the other electrode (the cathode), which is placed in an oxygen-rich environment. The anode and cathode are separated by a membrane, so that no oxygen can reach the anode and thus slow down the process.

The bacteria already present in the waste water convert the organic compounds in the waste water into:

CO2 Protons Electrons

The electrons generated in this manner travel via the conducting wire with resistor to the cathode, and along the way they can be used to power a light bulb, for instance. Once at the cathode, the electrons recombine with the protons and with oxygen to create pure water.

Links:

Microbial Fuel Cell Wetsus Magneto Special Anodes Paques BV    Femto Invest BV As the saying goes, one person’s trash is another person’s treasure. Researchers at the University of Western England (UWE) have demonstrated that a rather universal waste could be a valuable resource for us all. At team of researchers at the UWE Bristol Robotics Lab have published a paper in the Royal Chemical Society’s journal “Physical Chemistry Chemical Physics” that demonstrates how urine can be used as fuel for microbial fuel cells (MFCs).

The fuel cells work using a biofilm made up of bacteria on the anode side. These microbes digest the nutrients present in the urine, and create ions that can migrate through a semi-permeable membrane to reach the cathode and create an electrical current. The microbes consume the nitrogen, potassium, and phosphorous present in the urine. They can also break down other microbes – such as pathogenic bacteria – and other organic compounds such as sugars and proteins.

To maintain balanced consumption of the materials, additional oxygen and carbon compounds may need to be added. The end products of the process are water, carbon dioxide, and electricity. As a bonus, the effluent is treated to the point where it can be safely discharged back into the environment without further treatment. The bacteria in the biofilm grow, and the resulting “daughter cells” that are shed as part of this growth can be separated out from the effluent and used as a nitrogen-rich fertilizer.

The MFCs used in this process are tiny, and can take three days to process 25 ml of urine while producing a current of about 0.25mA. As a result, it would take hundreds – or thousands – combined in a single device to provide a viable system.

Fortunately, there is no shortage of “fuel” for these systems. According to estimates, the human population on the planet produces about 17 billion liters a day, while farm animals alone could contribute an additional 38 billion liters per day. This could be used to generate significant amounts of electrical power; the processed effluent and the fertilizer produced as a byproduct would be bonuses for the environment.

3/// The researchers started by taking some of the bacteria from ‘sludge’ from a wastewater treatment plant and used them to populate the fuel cells. After the bacteria had acclimatised to their new environment the researchers then started to effectively feed them urine (yum!).

Using pure urine as a ‘fuel’ the bacteria were not only able to produce reasonable amounts of electricity, they were also able to reproduce, meaning that as bacteria in the fuel cell died, new bacteria were able to take their place leading to a constant supply of electricity as long as urine was supplied to the bacteria (in fact the experiment had been running for over two years by the time the authors published their paper).

There are other advantages to the system too. As well as producing electricity from the urine, the process effectively treats it, producing a cleaner wastewater than went into the system. Even better, this wastewater contains the right ingredients at the right balance to be used as a good fertiliser, so using the urine even more effectively.

The researchers have calculated that if you consider all of the people and all of the farmed animals in the world the total amount of urine produced every single day is approximately 38 billion litres! So a great potential source of ‘fuel’ - the challenge for the researchers now is how to get the urine to the fuel cells.

Since producing the paper the scientists have successfully applied for funding from the Bill & Melinda Gates Foundation under the Grand Challenges Explorations programme for their project “Urine-tricity: Electricity from Urine and Sludge” to investigate the potential for using this system in developing countries to both treat wastewater and produce electricity at the same time[3]. In these countries the ability to turn abundant waste products into electricity would be a great help to both the economy and the people themselves.

But it’s not just in developing countries that this system has potential. Everyone alive produces the ‘fuel’ source daily and work is already being done to investigate how these fuel cells could be most efficiently used in countries like the UK too. Who knows, maybe one day there will be a stack of these fuel cells in our own houses ready to process our own wastewater! 4////

Dear all, I would like to introduce to you a research grant by the Bill & Melinda Gates Foundation that I am leading here at the University of the West of England:

Title of grant: Urine-tricity: Electricity from urine Subtitle: Generating electricity directly from urine, using Microbial Fuel Cells. Name of lead organization: University of the West of England, Bristol; Bristol Robotics Laboratory

Primary contact at lead organization: Ioannis Ieropoulos Grantee location: Bristol, United Kingdom Developing country where the research is being or will be tested: Durban, S. Africa

Short description of the project: The MFC is an energy transducer, with live (non-pathogenic) microorganisms as the bio-catalyst. It consists of two half-cells:- an anode (negative terminal) and a cathode (positive terminal) that are typically materialized in two different chambers. Microbes typically grow on the anode and continue with their normal metabolic processes. In the presence of an electrode and under the pressures of redox potential difference and consequent electrophilic attraction, they interact with the electrode and make it part of their natural anaerobic respiration, i.e. directly or indirectly transfer electrons onto the electrode. Microorganisms inside the anode of an MFC form a biofilm of fixed thickness, dictated by the ability and rate of electron transfer for respiration. These microorganisms form a stable semi-solid matrix onto the electrode surface, which becomes permanently stuck, robust and resistant, even at high flow rates. New daughter cells or other microbes, which have no access to the electrode, will remain in the anode until being flushed out. A very important feature of MFCs is the inherent link between electricity generation and waste (sludge or urine) break-down. This means that the higher the energy output levels, the better is the waste compound breakdown and the higher is the production of water at the cathode [2 incoming electrons and 2 protons per single water molecule]. Although different approaches can be employed for optimizing the MFC technology, the challenge of scaling up for practical applications remains unsolved. It has nonetheless been shown that higher energy density levels and optimum biofilm/electrode surface area–to–volume ratios, reside within smaller scale MFCs. This will be the scientific basis for the proposed work to succeed.

Goal(s): The goal of this project is to recover useful levels of electrical energy directly from urine, and thus convert an existing – entirely unexploited – waste into a sustainable fuel for the future, with concomitant clean water production.

Objectives: (i) high power production from MFC stack; (ii) high (collective) clean water production from the MFC stack; (iii) kill-rates of introduced pathogens as a result of normal MFC stack operation and (iv) modification of existing prototype urinal/latrine to integrate with MFCs.

Start and end date: Start date, 1 May 2012; End date, 30 April 2013; final report due 15 June 2013 Grant type: GCE R7 Funding for this research currently ongoing (yes/no): yes Research or implementation partners: no (not yet)

Links, further readings – results to date: These are some of the most recent publications, and report on the work of my EPSRC Fellowship and of our PhD students.

1. Physical Chemistry Chemical Physics, The first self-sustainable microbial fuel cell stack. DOI: Phys. Chem. Chem. Phys. pubs.rsc.org/en/Content/ArticleLanding/2012/CP/C1CP23213D

This communication reports for the first time the direct utilisation of urine in MFCs for the production of electricity. Different conversion efficiencies were recorded, depending on the amount treated. Elements such as N, P, K can be locked into new biomass, thus removed from solution, resulting in recycling without environmental pollution.

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2. International Journal of Hydrogen Energy, Miniature microbial fuel cells and stacks for urine utilization. DOI: dx.doi.org/10.1016/j.ijhydene.2012.09.062

3. ChemSusChem, Microbial fuel cells for robotics: energy autonomy through artificial symbiosis. onlinelibrary.wiley.com/doi/10.1002/cssc.201200283/abstract

The development of the microbial fuel cell (MFC) technology has seen an enormous growth over the last hundred years since its inception by Potter in 1911. The technology has reached a level of maturity that it is now considered to be a field in its own right with a growing scientific community. The highest level of activity has been recorded over the last decade and it is perhaps considered commonplace that MFCs are primarily suitable for stationary, passive wastewater treatment applications. Sceptics have certainly not considered MFCs as serious contenders in the race for developing renewable energy technologies. Yet this is the only type of alternative system that can convert organic waste—widely distributed around the globe—directly into electricity, and therefore, the only technology that will allow artificial agents to autonomously operate in a plethora of environments. This Minireview describes the history and current state-of-the-art regarding MFCs in robotics and their vital role in artificial symbiosis and autonomy. Furthermore, the article demonstrates how pursuing practical robotic applications can provide insights of the core MFC technology in general.

4. Bioresource Technology, MFC-cascade stacks maximise COD reduction and avoid voltage reversal under adverse conditions. DOI: dx.doi.org/10.1016/j.biortech.2013.01.119

5. Journal of Power Sources, Current Generation in Membraneless Single Chamber Microbial Fuel Cells (MFCs) Treating Urine, DOI: dx.doi.org/10.1016/j.jpowsour.2013.03.095

6. Bioresource Technology, Maximising electricity production by controlling the biofilm specific growth rate in microbial fuel cells. DOI: dx.doi.org/10.1016/j.biortech.2012.05.054

7. Bioelectrochemistry, The overshoot phenomenon as a function of internal resistance in microbial fuel cells. DOI: dx.doi.org/10.1016/j.bioelechem.2011.01.001

Presentation at the FSM-2 Conference: www.susana.org/images/documents/07-cap-d...gland-bristol-uk.pdf

Paper at FSM2 Conference: www.susana.org/docs_ccbk/susana_download/2-1624-ieropolous.pdf

PART TWO Science News ... from universities, journals, and other research organizations Save Email  Print  Share Replacing Fossil Fuels: Utilizing Sea Wave to Generate Electricity

Dec. 3, 2012 — Researchers Dr Ismail, Dr Muhammad Murtadha and Baharin Abu Bakar from Universiti Teknologi MARA, Malaysia have carried out a conceptual study on mathematical modelling for sea wave in electricity generation. Share This: 27

This conceptual study focused on using Oscillating Wave Column (OWC) which is considered as the most efficient way to utilize sea waves, the largest power source on earth, to generate electricity. Previous studies have revealed that global wave power is estimated to be 1TW (1 terrawatt=1012W).

Countries where numerous seafronts surround the country could tap into an alternative source of power generation which could be generated by the waves during the different seasons of the year. In addition, the findings of this study could be adapted to evaluate the capability to produce electricity on shore such as from lakes and rivers with undulated waves.

Researchers began the study with the derivation of mathematical equations for each component in the electrical generation system after taking into consideration the sea wave as the input to facilitate the workability of the entire system. The team of researchers verified the validity of the developed mathematical equations for each stage of the research. This was done to establish its workability. Electrical and mechanical relationships were derived to relate the workability of each component in the system for the purpose of electricity generation. Numerous experiments were conducted to optimize the results in this study which would eventually lead to the generation of electricity. The results obtained from the experiments indicated that the proposed model appears practical could be implemented.

PART THREE

Oct. 8, 2013 — Bacterial cells use an impressive range of strategies to grow, develop and sustain themselves. Despite their tiny size, these specialized machines interact with one another in intricate ways. Share This: 1

In new research conducted at Arizona State University's Biodesign Institute, Jonathan Badalamenti, César Torres and Rosa Krajmalnik-Brown explore the relationships of two important bacterial forms, demonstrating their ability to produce electricity by coordinating their metabolic activities.

In a pair of papers recently appearing in the journal Biotechnology and Bioengineering, the group demonstrates that the light-sensitive green sulfur bacterium Chlorobium can act in tandem with Geobacter, an anode respiring bacterium. The result is a light-responsive form of electricity generation.

"Geobacter is not light responsive in its own right because it's not a photosynthetic organism," says Badalamenti, lead author of the two new papers. In contrast, photosynthetic Chlorobium is unable to carry out the anode form of respiration necessary for electricity production. "But when you put these two organisms together, you get both a light response and the ability to generate current."

The electrons Geobacter acquires from its photosynthetic partner Chlorobium can be measured and collected in the form of electricity, using a device known as a microbial fuel cell (MFC) -- a kind of biological battery.

Microbial fuel cells may one day generate clean electricity from various streams of organic waste, simply by exploiting the electron-transfer abilities of various microorganisms.

The research was carried out at the Swette Center for Environmental Biotechnology, which is under the direction of Regents' Professor Bruce Rittmann. The goal of the Center is to exploit microorganisms for the benefit of society. These efforts typically involve the use of bacteria to clean up environmental pollutants or to provide clean energy. In the case of MFC research, bacteria can assist in both of these activities, generating useable electricity from energy-rich waste.

In the new studies, the researchers explore the possibility of enhancing electricity production in MFCs by examining the function of light-responsive Chlorobium, a photosynthetic green sulfur bacterium. The resulting experimental configuration, in which light responsive bacteria play a role in energy generation, is known as a microbial photoelectrochemical cell (MPC).

To explore the behavior of photosynthetic bacteria in a MPC, the team first used a clever means of selectively enriching phototrophs such as Clorobium in a mixed culture, by poising the device's anode at a particular electrical potential that was favorable for phototrophic growth, yet unfavorably low for the growth of non-photosynthetic anode respiring bacteria.

The researchers then noted an intriguing result: electricity production measured at the anode was linked to phases when the MPC was in total darkness and dropped during periods when the bacterial culture was exposed to light.

The group detected the presence of Chlorobium in the enrichment cultures using pyrosequencing and reasoned that the observed negative light responsiveness was either due to photosynthetic Chlorobium directly transferring electrons to the anode during dark phases or instead, transferring these electrons to a non-photosynthetic anode respiring bacterium like Geobacter, through an intermediary reaction.

Phototrophic organisms like Chlorobium are not known to carry out direct anode respiration. As Krajmalnik-Brown explains: "The follow up sceintific question was to disern if we had discovered a novel phototrophic anode respiring bacteria or if the phototroph was giving something to the anode respiring bacteria Geobacter and that was the response we were reporting."

In subsequent experiments, pure cultures of either Chlorobium or anode-respiring Geobacter were examined as well as co-cultures combining the two. In the case of Chlorobium alone, light responsive electricity generation was not observed. Similarly, pure Geobacter cultures failed to produce electrical current when deprived of an electron donor like acetate in the medium.

Only when the photosynthetic Chlorobium were combined with anode respiring Geobacter in co-culture experiments did electricity generation occur and it did so in a negative light-responsive manner -- increasing in periods of darkness and falling off during light phases.

The experimental results of the co-culture study suggest the following scenario: Chlorobium bacteria gather energy from light in order to fix carbon dioxide and fuel their metabolism. During dark phases however, they sustain themselves by switching from photosynthesis to dark fermentation, using energy they have stored. Acetate is produced as a metabolic byproduct of this dark phase fermentation.

During periods of darkness, anode respiring Geobacter gains electrons from the acetate produced through Chlorobium metabolism, transferring them to the MPC anode, thereby producing the observed rise in electrical current. "In this second study, we deliberately removed any sources of electrons that were present in the growth medium," Badalamenti says. When the two bacterial communities were forced to interact, it was clear that Chlorobium was helping to provide food for the Geobacter, in a light-responsive manner.

The authors note that one of the attractive advantages of their study is that electricity generation measured at the anode can be used as a highly accurate surrogate for the complexities of bacterial metabolism taking place in the MPC culture. "Unlike having to measure metabolites or cell growth either microscopically or through chemical intermediates, we are able to construct a co-culture system in which one of the readouts is electricity," Badalamenti says. "We can then monitor metabolism in the system in real time."

Further questions concerned whether the presence of Chlorobium may provide benefits for Geobacter in naturally occurring cultures, not confined to MFC devices. In anode-free experiments the group showed that the very survival of Geobacter in the absence of alternative sources of electrons was contingent on the presence of Chlorobium-derived acetate.

In addition to establishing a mechanism for light-responsive electricity generation in MFCs, the research points to the power of similar co-culture studies for elucidating a range of energy-producing microbial interactions. Share this story on Facebook, Twitter, and Google:

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Story Source:

The above story is based on materials provided by Arizona State University. The original article was written by Richard Harth.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal References:

Jonathan P. Badalamenti, César I. Torres, Rosa Krajmalnik-Brown. Coupling dark metabolism to electricity generation using photosynthetic cocultures. Biotechnology and Bioengineering, 2013; DOI: 10.1002/bit.25011 Jonathan P. Badalamenti, César I. Torres, Rosa Krajmalnik-Brown. Light-responsive current generation by phototrophically enriched anode biofilms dominated by green sulfur bacteria. Biotechnology and Bioengineering, 2013; 110 (4): 1020 DOI: 10.1002/bit.24779

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MLA Arizona State University (2013, October 8). Working together: Bacteria join forces to produce electricity. ScienceDaily. Retrieved October 11, 2013, from http://www.sciencedaily.com­ /releases/2013/10/131008102549.htm

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Coculture model for current production in the dark. A: In the light, Chlorobium photosynthetically accumulates glycogen (red particles) using electrons derived from sulfide oxidation. B: In the dark, Chlorobium ferments glycogen to acetate, which is consumed by Geobacter to produce electric current. (Credit: Image courtesy of Arizona State University

PART FOUR Ethanol Not a Major Factor in Reducing Gas Prices

Oct. 10, 2013 — If you have stopped at a gas station recently, there is a good chance your auto has consumed fuel with ethanol blended into it. Yet the price of gasoline is not substantially affected by the volume of its ethanol content, according to a paper co-authored by an MIT economist. The study seeks to rebut the claim, broadly aired over the past couple of years, that widespread use of ethanol has reduced the wholesale cost of gasoline by $0.89 to $1.09 per gallon. Share This: 1

Whatever the benefits or drawbacks of ethanol, MIT's Christopher Knittel says, price issues are not among them right now.

"The point of our paper is not to say that ethanol doesn't have a place in the marketplace, but it's more that the facts should drive this discussion," says Knittel, the William Barton Rogers Professor of Energy and a professor of applied economics at the MIT Sloan School of Management.

The 10 percent solution?

The vast majority of ethanol sold in the United States is made from corn. It now constitutes 10 percent of U.S. gasoline, up from 3 percent in 2003.

It is another matter, however, whether that increase in ethanol content produces serious savings at the pump, as some claim. Knittel and his co-author, economist Aaron Smith of the University of California at Davis, contest such an assertion in their paper, which is forthcoming in The Energy Journal, a peer-reviewed publication in the field.

The claim that ethanol lowers prices derives from a previous study on the issue, which Knittel and Smith believe is problematic. That prior work involves what energy economists call the "crack ratio," which is effectively the price of gasoline divided by the price of oil.

The crack ratio is something energy analysts can use to understand the relative value of gasoline compared to oil: The higher the crack ratio, the more expensive gasoline is in relative terms. If ethanol were a notably cheap component of gasoline production, its increasing presence in the fuel mix might reveal itself in the form of a decreasing crack ratio.

So while gasoline is made primarily from oil, there are other elements that figure into the cost of refining gasoline. Thus if oil prices double, Knittel points out, gasoline prices do not necessarily double. But in general, when oil prices -- as the denominator of this fraction -- go up, the crack ratio itself falls.

The previous work evaluated time periods when oil prices rose, and the percentage of ethanol in gasoline also rose.

But Knittel and Smith assert that the increased proportion of ethanol in gasoline merely correlated with the declining crack ratio, and did not contribute to it in any causal sense. Instead, they think that changing oil prices drove the change in the crack ratio, and that when those prices are accounted for, the apparent effect of ethanol "simply goes away," as Knittel says.

To further illustrate that the previous study was touting a correlation, not a causal relationship, Knittel and Smith conducted what are known in economics literature as "antitests" of that study's model. By inserting unconnected dependent variables into the model, they found that the model also produced a strong correlation between ethanol content in gasoline and, for instance, U.S. employment figures -- although the latter are clearly unrelated to the composition of gasoline.

The previous work also claimed that if ethanol production came to an immediate halt, gasoline prices would rise by 41 to 92 percent. But Knittel does not think that estimate would bear out in such a scenario.

"In the very short run, if ethanol vanished tomorrow, we would be scrambling to find fuel to cover that for a week, or less than a month," Knittel says. "But certainly within a month, increases in imports would relax or reduce that price impact."

Informing the debate

The differing assessments of ethanol's impact have garnered notice among economists and energy policy analysts. Scott Irwin, an economist at the University of Illinois at Urbana-Champaign who has read the paper, calls it a "convincing and compelling" rebuttal to the idea that expanding ethanol content in gasoline drastically lowers prices.

"The paper dispensed once and for all with that conclusion," Irwin says. Still, he adds, there remains an open debate about the marginal effects of ethanol content in gasoline, and more empirical work on the subject would be useful.

"A case can be made that it can be a positive few cents," Irwin says, adding that "reasonable arguments can be made on either side of zero" regarding ethanol's price impact. In either case, Irwin says, his view is that the effect is currently a small one.

Knittel has posted, on his MIT Sloan web page, a multipart exchange between himself and Dermot Hayes, an Iowa State University economist who is a co-author of the prior work. After an initial finding that ethanol reduced gasoline prices by $0.25 per gallon, Hayes and a co-author produced follow-up studies, examining about a decade after 2000, and arrived at the figures of $0.89 and $1.09 per gallon, which gained wider public traction.

Knittel acknowledges that policy decisions about gasoline production are driven by a complex series of political factors, and says his study is not intended to directly convey any policy preferences on his part. Still, he suggests that even ethanol backers in policy debates have reason to keep examining its value.

"Making claims about the benefits of ethanol that are overblown is only going to set up policymakers for disappointment," Knittel says.

PART FIVE Producing Hydrogen from Water With Carbon/Charcoal Powder

Aug. 28, 2013 — In the latest advance in efforts to find an inexpensive way to make hydrogen from ordinary water -- one of the keys to the much-discussed "hydrogen economy" -- scientists are reporting that powder from high-grade charcoal and other forms of carbon can free hydrogen from water illuminated with laser pulses. Share This: 23

A report on the discovery appears in ACS' Journal of Physical Chemistry C.

Ikuko Akimoto and colleagues point out that traditional approaches to breaking down water, which consists of hydrogen and oxygen, involve use of expensive catalysts or electric current passed through water. Since economical production of hydrogen from water could foster a transition from coal, oil and other fossil fuels, scientists have been searching for less expensive catalysts. Those materials speed up chemical reactions that otherwise would not work effectively. Based on hints from research decades ago, the scientists decided to check out the ability of carbon powder and charcoal powder, which are inexpensive and readily available, to help split hydrogen gas from oxygen in water.

Akimoto's team tested carbon and charcoal powders by adding them to water and beaming a laser in nanosecond pulses at the mixtures. The experiment generated hydrogen at room temperature without the need for costly catalysts or electrodes. Its success provides an alternative, inexpensive method for producing small amounts of hydrogen from water.