SciELO - Scientific Electronic Library Online

 
vol.111 issue5-6Eutrophication and cyanobacteria in South Africa's standing water bodies: A view from space author indexsubject indexarticles search
Home Pagealphabetic serial listing  

South African Journal of Science

On-line version ISSN 1996-7489
Print version ISSN 0038-2353

S. Afr. j. sci. vol.111 n.5-6 Pretoria May./Jun. 2015

http://dx.doi.org/10.17159/sajs.2015/20140151 

RESEARCH ARTICLE

 

Characteristics of potential gasifier fuels in selected regions of the Lake Victoria Basin

 

 

Geoffrey O. MosioriI; Charles O. OnindoI; Paul MugabiII; Susan B. TumwebazeII; Samuel BagaboIII; Rukundo B. JohnsonIV

IDepartment of Chemistry, Kenyatta University, Nairobi, Kenya
IIFaculty of Forestry & Nature Conservation, Makerere University, Kampala, Uganda
IIIIntegrated Rural Development Initiatives, Kampala, Uganda
IVFaculty of Economics and Management, National University of Rwanda, Kigali, Rwanda

Correspondence

 

 


ABSTRACT

All countries in the Lake Victoria Basin depend mostly on hydroelectric power for the provision of energy. Gasification technology has a high potential for reducing biomass energy consumption whilst increasing access to modern energy services. The key aspect for the failure of gasification operations in the Lake Victoria Basin is inadequate adaptation of gasification equipment to fuel characteristics, lack of fuel specification and inappropriate material choice. We therefore investigated the thermo-chemical characterisation of six biomass fuels, namely Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis, Pinus patula and sugarcane bagasse from selected regions of the Lake Victoria Basin. Ultimate analysis was done using a Flash 2000 elemental analyser. Moisture content, ash content and volatile matter were determined in oven and muffle furnaces while heating values were determined using a Gallenkamp calorimeter. The mean percentage levels obtained indicate that all six biomass fuels had a mean range for nitrogen of 0.07±0.2-0.25±0.07%, for carbon of 40.45±0.61-48.88±0.29%, for hydrogen of 4.32±0.13-5.59±0.18% and for oxygen of 43.41±1.58-51.1±0.64%. Moisture content ranged between 25.74±1.54% and 56.69±0.52%, ash content between 0.38±0.02% and 2.94±0.14%, volatile matter between 74.68±0.49% and 82.71±0.19% and fixed carbon between 14.35±0.33% and 24.74±0.27%. Heating values ranged between 16.95±0.10 MJ/kg and 19.48±0.42 MJ/kg. The results suggest that all six biomass fuels are potential biomass gasification materials.

Keywords: gasification; biomass; renewable energy; East Africa


 

 

Introduction

Modern energy, such as electricity, is crucial in order to achieve the Millennium Development Goals of poverty reduction, improved education and environmental sustainability.1 Currently, about one-third of the world's population, or two billion people, have only intermittent access to modern energy services. The energy sector in the Lake Victoria Basin is dominated by traditional biomass-based fuels, which contribute over 70% to the total energy consumption.2,3 As a result of the use of poor technology (e.g. three stones and charcoal stoves), many regard biomass energy as inferior. Women and children inhale fumes while cooking indoors and spend considerable time collecting firewood.2,4,5 Hydroelectric power and energy from petroleum products is prohibitively expensive and mostly restricted to urban areas. In order to alleviate poverty in the Lake Victoria Basin, the rural-based households (over 80%) will need access to modern energy services.2

Biomass in the form of trees, shrubs, agro and forest wastes, grasses and vegetables is abundant in the Lake Victoria Basin and is renewable. Fortunately, the basin is located on the equator and as a result of this proximity receives an abundant insolation averaging 4.5 kWh/m2/day.6 This insolation provides the necessary conducive environment for vast growth of biomass. What is really required to increase rural household energy security is to catalyse rural industrialisation. Biomass gasification for energy production is one such system.7,8 Gasification technology involves incomplete combustion of biomass resulting in the production of combustible gases consisting of carbon monoxide, hydrogen and traces of methane.8-12 Gasification is the most efficient way known to date of converting biomass into energy; it converts 60-90% of the energy in the biomass into energy in the gas, compared to traditional systems which utilise 10-30%.13,14

 

Method and materials

Study area

Biomass samples were obtained from the forests located in the Lake Victoria Basin in Kenya and Uganda. In Kenya, eight regions were chosen: Malava Forest in Kakamega County, Kibiri Block Forest in Vihiga County, Ombo Forest in Migori County, Kodera Forest in Rachuonyo County, Kakamega Forest in Kakamega County, Port Victoria natural forest in Busia County, Aloso Block Forest in Migori County and Sony Sugar Company in Migori County. In Uganda, samples were obtained from the Wakiso District. These forests were purposely selected because they are managed by forest services in both Kenya and Uganda.

Sampling procedure and collection

Breast-height (1.3 m from the ground) stem wood samples were collected from each species. Cupressus lusitanica was collected from Kakamega, Ombo, Kodera and Port Victoria Forests, Pinus patula was collected from Kibiri and Kodera Forests, Pinus caribaea from Kodera (Kenya) and Wakiso (Uganda) Forests, Calitris robusta from Aloso Forest and Eucalyptus grandis from Wakiso Forest. The samples were cut into small wood chips. Sugarcane bagasse was collected from the Sony Sugar Company and was sampled from the top, middle and bottom of the heap of sugarcane bagasse. The sugarcane bagasse samples were subsequently placed in three 50-kg gunny sacks and transported for analysis.

Determination of moisture content

Moisture content was determined in accordance with ASTM Standard D3173-87.15 Nine replicates were obtained from each biomass sample. The sample was placed in a convection oven at 105±3 °C for 4 h, removed and cooled to room temperature in desiccators with P2O5 as the drying agent. The dish containing the oven-dried sample was weighed and the weight recorded. The sample was placed back into the convection oven at 105±3 °C and dried to constant weight. Percentage weight loss was taken as the moisture content of the original sample.

Ash determination

Ash determination was done in accordance with ASTM Standard D3174-97.16 The nine dried samples (10 g) were placed into crucibles and placed in a furnace set to 575±25 °C for 4 h, after which the crucibles containing the samples were removed and cooled in desiccators. The weight of the crucible and the sample was then recorded to the nearest 0.1 mg. The ash content (%) was calculated as:

where W1 is the mass of the empty dry crucible, W2 is the mass of the dry crucible plus the dry sample of biomass and W3 is the mass of the dry crucible plus the cooled greyish-white ash.

Volatile matter determination

Determination of volatile matter content was done in accordance with ASTM standards.17 Approximately 10 g of the dried sample was weighed into crucibles with a closely fitting cover and placed into a muffle furnace maintained at 950±20 °C. After 7 min of heating, the crucibles were removed, cooled in desiccators and weighed. Nine samples of each feedstock were used. Volatile matter (%) was calculated as:

Volatile matter = 100 x (I - F)/I, Equation 2

where l is the initial weight of the sample (g) and F is the final weight of the sample (g).

Calculation of percentage fixed carbon

Fixed carbon was calculated using the volatile matter and ash amount according to McKendry18 as follows:

% FC = 100 - (% VM + % ash), Equation 3

where FC is the fixed carbon and VM is volatile matter.

Energy content

The energy content was determined in accordance with ASTM Standard D2015-96.19 A Gallenkamp auto bomb calorimeter (model number SG97/10/070, Fistreem International Limited, Leicestershire, UK) was used.

Higher heating values derived from theoretical equations

Equations 4-6 were used to estimate the higher heating values (HHV) of the biomass samples and the results were compared with the experimental values.

HHV= 0.196 x FC + 14.119 Equation 420

HHV= 0.4373 x C - 1.6701 Equation 521

HHV= -0.763 + 0.301 x C + 0.525 x H + 0.064 x O Equation 622

Ultimate analysis

The carbon, nitrogen and hydrogen contents were determined using a Flash 2000 elemental analyser (model number 31712052, Thermo Fisher Scientific, Delft, the Netherlands) according to ASTM Standard E775.23

Calculations for synthesis gas composition

Equations 7-9 developed by Gopal24 were used to predict the percentage volume of CO, CO2, and H2:

Data analysis

Data were subjected to statistical analyses including a one-way analysis of variance (ANOVA) and Student-Newman-Keuls (SNK) test. These methods are useful in providing interdependence of the variables and significant differences.25

 

Results and discussion

Proximate analysis

A summary of the proximate analysis is presented in Table 1.

Table 1 shows that the moisture contents of the six biomass samples were significantly different (p<0.05, SNK test). The moisture content of wood typically varies between 10% and 60% while that of sugarcane bagasse ranges between 40% and 60%.26,27 In this study, the moisture contents of Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis and Pinus patula were in the range of 10-60%. The moisture content of sugarcane bagasse was in the range of 40-60%. Brammer and Bridgewater28 reported that a moisture content of up to 20% and 50% is acceptable for downdraught and updraught gasifiers, respectively, whereas fluidised bed gasifiers have been reported to gasify materials with moisture contents of up to 70%.29

Sugarcane bagasse showed significantly higher levels of ash compared with Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis and Pinus patula. All six biomass feedstocks qualified for use in biomass gasification as they had an ash content less than 5%.30 All the biomass feedstocks investigated can be used in downdraught gasifiers as they contained less than 6% ash31,32 and sugarcane bagasse can be used in updraught gasifiers as the minimum ash content was 1.4% and the maximum was 25%.31,32

Sugarcane bagasse had a higher percentage mean of volatile matter than did Cupressus lusitanica. The percentage of volatile matter of Pinus caribaea, Calitris robusta, Eucalyptus grandis and Pinus patula did not differ significantly from one another (p>0.05, SNK test). Woods typically have a volatile matter of 72-78%.33,34

Cupressus lusitanica had a higher fixed carbon content than sugarcane bagasse. Sugarcane bagasse had the lowest fixed carbon content. The fixed carbon contents of Pinus caribaea and Pinus patula did not differ statistically (p>0.05, SNK test). According to McKendry18, wood has a fixed carbon content of about 20%. Anjireddy and Sastry35 showed that sugarcane bagasse had a fixed carbon content of 15.8%.

Ultimate analysis

A summary of the ultimate analyses is presented in Table 2.

Table 2 shows the percentage weight of nitrogen of the six biomass feedstocks; the mean percentages of nitrogen did not differ significantly (p>0.05, SNK test). According to Jenkins et al.36, all biomass material contains 0.2-1% nitrogen. To avoid corrosion and emission of NOx to the atmosphere during combustion, according to Obernberger et al.37, all biomass material must contain less than 0.6% nitrogen. Our six biomass samples contained less than 0.6% nitrogen, which qualifies them as suitable feedstock for gasification processes.

There was a significant difference in the percentage weight of carbon among the six biomass fuels (p<0.05, SNK test). The percentage mean carbon contents of Cupressus lusitanica, Calitris robusta and Pinus patula were significantly higher than that of sugarcane bagasse. According to Demirbas13 and BTG38, the carbon content of typical biomass must range from 42% to 54%. The six biomass fuels were within this range.

Table 2 shows the percentage weight of hydrogen of the six biomass samples. The hydrogen contents of Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis and Pinus patula were not significantly different from one another, but sugarcane bagasse had a significantly lower percentage of hydrogen (p<0.05, SNK test).

Turn et al.39 reported 4.98% hydrogen for bagasse and Cheremisnoff40 found that typical woods have about 6% hydrogen. BTG38 reported hydrogen in the range of 5.5-6.2%. These reports are in agreement with our results.

The mean percentage oxygen of Pinus caribaea, Eucalyptus grandis and sugarcane bagasse were significantly higher than that of Pinus patula (p<0.05, SNK test; Table 2). The mean percentage oxygen of Calitris robusta and Cupressus lusitanica was not significantly different (p>0.05, SNK test). Raveendran et al.41 reported an oxygen percentage of 47.1%, which is similar to our results. BTG38 showed that typical biomass materials have an oxygen percentage of 40-51%. The results from this study therefore are in agreement with those of previous studies.

Heating values

The energy content of the biomass feedstocks is presented in Table 3.

Table 3 shows a significant difference in the energy contents of the six biomass fuels (p<0.05, SNK test). Pinus patula and Cupressus lusitanica had higher energy contents than Eucalyptus grandis and sugarcane bagasse. The energy contents of Pinus caribaea and Calitris robusta did not differ significantly. Nonde42 reported heating values of wood fuels of between 18 MJ/kg and 20 MJ/kg. Howlett and Gamache43 also reported values of 17.7-21.0 MJ/kg for foliage materials. These values are within the range of our results. The measured heating values were also in agreement with the predicted values. The heating value determines the suitability of biomass for pyrolysis, carbonisation, liquefaction and gasification. The heating value is a function of the chemical composition, in particular, the carbon content. Variation in the heating values among different species and different plant components shows differences in the chemical composition, which is used to demonstrate the quality of the fuel.

Predicted synthesis gas

The predicted synthesis gas composition is presented in Table 4.

The predicted synthesis gas composition from the gasification of Eucalyptus grandis was 16.52±0.43% H2 and 25.13±0.65% CO. These values were slightly higher than those reported by Gopal24 who found 16.1% H2 and 24.0% CO. For sugarcane bagasse, the predicted composition was 15.04±0.54% H2 and 24.47±0.88% CO, which is similar to those reported by Gopal24 who found 15.4% H2 and 23.4% CO. The Energy and Resources Institute44 found that typical biomass produces 18-22% CO and 13-19% H2. Sharma45 concluded that feedstocks which produced 15% CO and 13% H2 were considered acceptable for gasification.

Table 5 gives a comparison of selected properties of the selected biomass feedstocks in the Lake Victoria region.

Cupressus lusitanica from the Ombo Forest had a higher moisture content than that from the Kodera Forest (p<0.05, t-test). Pinus patula from the Kodera Forest had a higher moisture content than that from the Kibiri Forest. Cupressus lusitanica from the Kakamega Forest had a significantly higher percentage of nitrogen than that from the Kodera, Ombo and Port Victoria Forests (p<0.05, SNK test). There was no significant difference in the percentage of nitrogen in Pinus caribaea from the Kodera and Wakiso Forests (p>0.05, t-test). This variation in the percentage of nitrogen among the regions and species is mainly because of differences in environmental factors, nutrients and water.46

There also were significant differences in the percentage of carbon in Cupressus lusitanica (p < 0.04, SNK test). The percentage of carbon in Cupressus lusitanica from the Kakamega, Ombo and Port Victoria Forests was significantly higher than that from the Kodera Forest. There was also a significant difference in the percentage of carbon in Pinus caribaea from Kodera and Wakiso Forests (p< 0.05, t-test). The differences in the percentage of carbon among different regions can be attributed to soil physiology.46 The percentage of hydrogen in Cupressus lusitanica from Kodera and Ombo Forests was significantly higher than those from Kakamega and Port Victoria Forests (p<0.05, SNK test).

 

Conclusion and recommendations

The six biomass fuels had low ash content, low nitrogen content and high energy content and are therefore suitable for gasification. Significant variations were also observed in the selected thermo-chemical properties of the biomass from different regions within the Lake Victoria Basin. The predicted synthesis gas composition of the biomass fuels was more than 15% CO and 13% H2. It is recommended that an actual gasification can be carried out to compare the amount of synthesis gas generated with that estimated from the thermodynamic equilibrium model.

 

Acknowledgements

We are grateful for financial support received from the Inter University Council for East Africa through the Lake Victoria Research Initiative (VicRes).

Authors' contributions

G.O.M. wrote the manuscript; C.O.O. was the project leader; PM., S.B.T., S.B. and R.B.J. collected the samples for analysis.

 

References

1. Modi V. McDade S, Lallement D, Saghir J. Energy and the Millennium Development Goals. New York: Energy Sector Management Assistance Programme, United Nations Development Programme, UN Millennium Project and World Bank; 2006.         [ Links ]

2. East Africa Community (EAC). East Africa Community regional strategy on scaling-up access to modern energy services in the East African Community [document on the Internet]. c2009 [cited 2011 Oct 21]. Available from: http://www.eac.int/energy/index.php?option=com_docman&task=doc_download&gid=14&Itemid=70        [ Links ]

3. Ministry for Planning and National Development (MPND). Integrated assessment of the energy policy with focus on the transport and household energy sectors. Nairobi: MPND; 2006.         [ Links ]

4. Bailis R, Ezzati M, Kammen DM. Mortality and greenhouse gas impacts of biomass and petroleum energy futures in Africa. Science. 2005;308:98-103. http://dx.doi.org/10.1126/science.1106881        [ Links ]

5. Reddy AKN, Williams RH, Johansson TP. New opportunities in energy demand, supply and systems. In: Amulya K, editor. Energy after Rio - Prospects and challenges. New York: UNDP; 1997. p. 63-108.         [ Links ]

6. Ministry of Energy and Mineral Development (MEMD). Energy efficiency and renewable energy directory. 2nd ed. Kampala: MEMD; 2005.         [ Links ]

7. Keyun D. State of the art of the utilization of agricultural residues and other biomass and identification of priority projects in China in agricultural biomass for sustainable rural development. Bangkok: ESCAP; 1993.         [ Links ]

8. Nouni MR, Mullick SC, Kandpal TC. Biomass gasifier projects for decentralized power supply in India: A financial evaluation. Energ Policy. 2007;35:1373- 1385. http://dx.doLorg/10!1016/j.enpol.2006.03.016        [ Links ]

9. Ravindranath NH, Somashek HI, Dasappa S, Jaysheela Reddy CN. Sustainable biomass power for rural India: Case study of biomass gasifier for village electrification. Curr Sci India. 2004;87:56-89.         [ Links ]

10. Adnan M, Murat D, Colin R, Howarth M, Ling J, Teoman A. Combustible gas production from sewage sludge with a downdraft gasifier. Energ Convers Manage. 2001;42:157-172. http://dx.doi.org/10.1016/S0196-8904(00)00053-4        [ Links ]

11. Dasappa S, Paul PJ, Mukunda HS, Rajan NKS, Sridhar G, Sridhar HV. Biomass gasification technology - A route to meet energy needs. Curr Sci India. 2004;87:908-916.         [ Links ]

12. Stassen HEM. Small-scale biomass gasifiers for heat and power: A global review. World Bank Technical Paper Series. Washington DC: UNDP ESMAP; 1995. http://dx.doi.org/10.1596/0-8213-3371-2        [ Links ]

13. Richey CB. Downdraft channel biomass gasifier. US Patent 4, 452, 611, 1984.         [ Links ]

14. Demirbas A. Combustion characteristics of different biomass fuels. Prog Energ Combust. 2004;30:219-230. http://dx.doi.org/10!1016/j.pecs.2003.10.004        [ Links ]

15. Reed TB, Das A. Handbook of biomass downdraft gasifier engine systems. Golden, CO: SERI; 1998.         [ Links ]

16. American Society for Testing Materials (ASTM). Standard test method for moisture in the analysis sample of coal and coke. Standards D3173-87. In: Annual book of ASTM standards, Section 5, Vol. 05.05. West Conshohocken, PA: ASTM; 1998. p. 301-302.         [ Links ]

17. American Society for Testing Materials (ASTM). Standard test method for ash in the analysis sample of coal and coke. Standards D3174-97 In: Annual book of ASTM standards, Section 5, Vol. 05.05. West Conshohocken, PA: ASTM; 1998. p. 303-305.         [ Links ]

18. American Society for Testing Materials (ASTM). Standard classification of coal by rank. Standards D388-99. Philadelphia, PA: ASTM; 1999.         [ Links ]

19. McKendry P. Energy production from biomass (part 3): Gasification technologies. Bioresour Technol. 2002;83:37-63. http://dx.doi.org/10.1016/S0960-8524(01)00118-3        [ Links ]

20. American Society for Testing Materials (ASTM). Standard test method for gross calorific value of coal and coke by the adiabatic bomb calorimeter. Standard D2015-96. In: Annual book of ASTM standards, Section 5, Vol. 05.05. West Conshohocken, PA: ASTM; 1998. p. 239-247.         [ Links ]

21. Demirbas A. Calculation of higher heating values of biomass fuels. Fuel. 1997;76:431-434.         [ Links ]

22. Tilman DA. Wood as an energy resource. New York: Academic Press; 1978.         [ Links ]

23. Jenkins BM, Ebeling JM. Correlations of physical and chemical properties of terrestrial biomass with conversion. In: Proceedings of the IGT symposium: Energy from Biomass and Waste IX; 1985 Jan 28 - Feb 01; Lake Buena Vista, FL, USA. Chicago, IL: IGT; 1985. p. 371.         [ Links ]

24. American Society for Testing Materials (ASTM). Standard test method for elemental analysis. Standards E775-8. In: Annual book of ASTM standards, Section 5, Vol. 05.05. West Conshohocken, PA: ASTM; 1998. p. 306-308.         [ Links ]

25. Gopal G. Parametric study of a commercial-scale biomass downdraft: Experimental and equilibrium modeling [Master's dissertation]. Auburn, AL: Auburn University; 2010.         [ Links ]

26. Miller JC, Miller J. Statistics for analytical chemistry. 2nd ed. Chichester: Ellis Harwood Ltd; 1988.         [ Links ]

27. Quaak P Knoef H, Stassen H. Energy from biomass. A review of combustion and gasification technologies. World Bank Technical Paper No. 422. Washington DC: World Bank; 1999.         [ Links ]

28. Faaij A, Doorn JV.Curvers T, Waldheim L, Olsson E, Wijk AV et al. Characteristics and availability of biomass waste and residues in the Netherlands for gasification. Biomass Bioenerg. 1997;2:225-240. http://dx.doi.org/10.1016/S0961-9534(97)00003-2        [ Links ]

29. Brammer JG, Bridgewater AV. Drying technologies for an integrated gasification bio-energy plant. Renew Sust Energ Rev. 1999;3:243-289. http://dx.doi.org/10.1016/S1364-0321(99)00008-8        [ Links ]

30. Holmberg H, Ahtila P. Comparison of drying cost in biofuel drying between multi-stage and single-stage drying. Biomass Bioenerg. 2004;26:515-530. http://dx.doi.org/10.1016/j.biombioe.2003.09.007        [ Links ]

31. Food and Agricultural Organization of the United Nations (FAO). Wood gas as engine fuel. FAO Forest Paper 72. Rome: Mechanical Wood Products Branch, Forest Industries Division, FAO; 1986.         [ Links ]

32. Van Swaay WPM, Van dee Aarsen FG, Bridgewater AV, Heesink ABM. A review of biomass gasification. A report to the European Community. Paris: DGXII JOULE program; 1994.         [ Links ]

33. BTG (Biomass Technology Group). BTG: Energy from biomass. A review of combustion and gasification technologies. World Bank Technical Paper No. 422. Washington DC: World Bank; 1995.         [ Links ]

34. Food and Agriculture Organization of the United Nations (FAO). Wood gas as engine fuel. Rome: FAO; 1986. Available from: http://www.fao.org/3/a-t0512e.pdf        [ Links ]

35. Turare C. Biomass gasification - Technology and utilization. Glucksburg, Germany: ARTES Institute, University of Flensburg; 2002.         [ Links ]

36. Anjireddy B, Sastry R. Biomass gasification processes in downdraft fixed bed reactors: A review. Int J Chem Eng Appl. 2011;6:425-431.         [ Links ]

37. Jenkins BM, Baxter LL, Miles TR. Combustion properties of biomass. Fuel Process Technol. 1998;54:17-46. http://dx.doi.org/10.1016/S0378-3820(97)00059-3        [ Links ]

38. Obernberger I, Brunner T, Barnthaler G. Chemical properties of solid biofuels - Significance and impact. Biomass Bioenerg. 2006;14:30973-30982.         [ Links ]

39. BTG (Biomass Technology Group). Thermochemical conversion of biomass to energy. Vienna: UNIDO; 1987.         [ Links ]

40. Turn SQ, Keffer V, Staackmann M. Analysis of Hawaii biomass energy resources for distributed energy applications. Prepared for the State of Hawaii, Department of Business, Economic Development and Tourism. Honolulu: Natural Energy Institute; 2002.         [ Links ]

41. Cheremisnoff PN. Waste incineration handbook. Oxford: Butterworth- Heinemann; 1992.         [ Links ]

42. Raveendran K, Ganesh A, Khilar KC. Influence of mineral matter on biomass pyrolysis characteristics. Fuel. 1995;74:1812-1822. http://dx.doi.org/10.1016/0016-2361(95)80013-8        [ Links ]

43. Nonde E. Forest research utilization: A Powerpoint presentation on Kaputa bio gasifier project. Lusaka: Forest Department; 2009.         [ Links ]

44. Howlett K, Gamache A. Forest and mill residues as potential sources of biomass. Report 7347. Maclean, VA: The Mitre Corporation/Metek Division; 1997.         [ Links ]

45. The Energy and Resources Institute (TERI). RETs II theme - Thermal applications of biomass gasifier in SMiEs. Project Report No. 2005BE28. New Delhi: TERI; 2006.         [ Links ]

46. Sharma KA. Equilibrium modeling of global reduction reactions for a downdraft (biomass) gasifier. Energ Convers Manage. 2011;49:832-842. http://dx.doi.org/10.1016/j.enconman.2007.06.025        [ Links ]

47. Michigan Forest Forever Teacher Guide. Plant physiology [homepage on the Internet]. c1998 [cited 2012 Oct 10]. Available from: from http://www.mfftg.com/plantphysiology        [ Links ]

 

 

Correspondence:
Geoffrey O. Mosiori
Department of Chemistry, Kenyatta University
PO Box 43844, Nairobi 00100
Kenya
Email: geosiri2006@yahoo.com

Received: 02 May 2014
Revised: 13 June 2014
Accepted: 02 Sep. 2014

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License