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Design and cost-benefit analysis of a novel anaerobic industrial bioenergy plant in Pakistan
Renewable Energy 90 (2016) 242e247
Contents lists available at ScienceDirect
Renewable Energy journal homepage: www.elsevier.com/locate/renene
Design and cost-benefit analysis of a novel anaerobic industrial bioenergy plant in Pakistan Rizwan Rasheed a, *, Naghman Khan b, Abdullah Yasar a, Yuehong Su b, Amtul Bari Tabinda a a b
Sustainable Development Study Centre, Government College University Lahore, Pakistan Department of Architecture and Built Environment, University of Nottingham, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2015 Received in revised form 2 December 2015 Accepted 1 January 2016 Available online xxx
The design and Cost-benefit analysis (CBA) of a novel anaerobic bioenergy plant is presented. This plant can digest various feed sources including animal-manure, vegetable-fruit wastes, poultry wastes, sugar molasses etc. The fixed dome multi-digestor system enables a continuous feed and flow mechanism. It is also equipped with a biogas purification, compression and storage system. This medium scale bioenergy plant is the first of its kind in Pakistan. It has a total installation cost of US$105,000 and annual operation and maintenance cost of US$23,400. The average energy production is 142,380 kWh per annum. With a current average energy cost of US$0.315 per kWh from all sources in Pakistan, the cost-benefit ratio is 1.2 at an internal rate of return (IRR) of 19.76%, and short payback period. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Biogas Bio-fuels Bioenergy generation Pakistan
1. Introduction Pakistan, with its population of approximately 184 million people (growing at 2.2% perannum) has a high rural population. Agriculture accounts for 25% of GDP and employs over 40% of the workforce [1]. Pakistan has a rapidly developing economy with a young population, and significantly rising energy and electricity demand, both towards transportation and industrial/domestic electricity consumption [2]. The installed generating capacity as of 2011 is 21,036 MW. Electricity demand is growing at 9% annually while supply is only at 7%, with an even higher discrepancy in summer [3]. Pakistan has a mix of electricity generation sources including thermal (gas and oil), hydroelectric and nuclear power. Renewables and coal play a minor role at the moment but are expected to increase significantly in the future, as reported [4]: the key renewable resources identified are biomass, wind and solar energy. A more recent study [5] presented an in depth analysis of the biomass potential in Pakistan. Pakistan's livestock inventory is 159 million animals producing almost 652 million kg of manure daily from cattle and buffalo only, which could in theory be used to generate 16.3 million m3 of biogas daily and over 20 million tons of
* Corresponding author. E-mail address: [email protected] (R. Rasheed). http://dx.doi.org/10.1016/j.renene.2016.01.008 0960-1481/© 2016 Elsevier Ltd. All rights reserved.
fertilizer annually. The study also cites a government program to install 10,000 domestic biogas units over the next five years, thus saving millions of $ annually in substituting fossil fuel costs. There are however significant barriers and obstacles to fully develop this potential [6e9]. The development of biogas, although started in the 1980s, remains an economic issue and a comparison with mostly natural gas and LPG will determine its growth. This paper presents a cost and benefit analysis of novel design of bioenergy plant on an industrial scale. It is the first plant of its kind in Pakistan, despite a few industrial scale bioenergy projects having been designed and implemented in the sub-continent and reported in literature [10,11] for cottage/small scale industries like milling, grinding, cutting, water pumping and in some related manufacturing activities. A study in rural India [12] reported that most rural people are not ready to accept the use of electricity generated from biomass sources, due to cost and logistical problems. A study conducted in twelve African countries on 38 bioenergy installations has indicated that economies of scale were not prominent for the small to institutional scale bioenergy plants which is opposing the general, conventional financial mindset of the industry that bigger bioenergy installations are advantageous in-terms of economies of scale. It was also concluded by the study that the technology of bioenergy is mostly independent of geographical setting of such plants [13,14]. A comparative Indian economic study [15] of 1e6 m3
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243
sized biogas plants, which were of the conventional single digester with fixed dome or floating drum design, found that the installation and operational cost increased proportionally with the installed capacity of the biogas plant, irrespective of the biogas plant type. These plants have low biogas outputs of 1 m3/25 kg i.e. 40 m3/tonne of cow-manure as compared to our novel multidigester and lagoon based continuous flow design which produced 80e90 m3/tonne of biogas with cow-manure. Of course, the financial payback period decreases dramatically with the increase in installed capacity. The present research follows the above said studies in assessing the systems and cost-benefit analysis of our new industrial scale bioenergy plant and this forms part of continuing research. Comparative economic studies and life cycle cost-benefit assessments are also being conducted similar to those applied in Refs. [13] and [15].
2500 MHz frequency for which a set of electronic magnetrons of 5600 V are installed over the dome of the digestion well 1 (Fig. 1). Microwaves are only used for shorter specific time intervals of 5e10 min for rapid temperature enhancement, initiation of methanogenesis and faster decomposition of substrate molecules when fresh feedstock is inducted on daily basis.
2. Plant design analysis
2.4. Water scrubbers and filtration system
The current bioenergy plant design is a modified and mixed form of a fixed dome anaerobic digester (AD), continuous stirring tank reactor (CSTR) and lagoon. This design establishes a continuous feed and flow system with the ability to handle single to multiple-mixed organic feedstock, from animal manure to poultry waste and sugar molasses etc. It also has the provisions of bioenergy purification, compression and storage. A schematic of this plant is shown in Fig. 1. The actual plant picture is presented in Fig. 2. The salient design features are elaborated in the following sections.
The bioenergy scrubbing and filtration system consists of two sub-systems. The first one, prior to the compression and storage is based on three interconnected filtration chambers made of fibreglass reinforced polymer (FRP) material in cylindrical shape each having size: 2.01 m (height) 1.21 m (diameter). These are attached with gas collection piping system (Fig. 3 and part-h) for the removal of CO2 with the help of special water scrubbers, using 5 mm FRP composite inner dish type filters, with 10 C water and incoming gas pressure at 2.24 MPa (325 psi). Secondly, activated carbon filter is used to eliminate certain sulphides and siloxanes from biogas [16], and silica gel filter is utilized for the removal of water contents subsequently. These filters have a useful life of 3e5 years. The cross-sectional view of the gas filtration unit is shown in Fig. 4. Air cooled medium at 6 C is used for water-moisture removal (Figs 2 and 3 part-j).
2.1. Multistage anaerobic digester (AD) with lagoon This experimental plant uses a fixed dome type multistage (three) anaerobic digesters each of 4.26 m (height) 4.26m (diameter) size. These are interconnected with an underlying lagoon of the size of 26.03 m (length) 1.52 m (width) 1.7 m (height) to manage the continuous feed intake, slurry outflow and enhance the gas output (Fig. 3, part-b). The lagoon is directly connected with the mechanically stirred inlet tank to allow different input feedstock. All the digesters and lagoon are built of concrete. The fixed dome digesters are covered with seamless, antirust, lightweight and durable FRP (fibreglass reinforced polymer) composite domes (top covers). The gas collection (output) points are located right over each dome, and interlinked with a common piping for gas collection. 2.2. CSTR and microwave system Digester No 1 and 3 also function as CSTR (continuous stirring tank reactors), as these are equipped with mechanical agitators, driven by an electrical motor (2 HP; 1100 RPM; 460 V). Digester 1 is also provided with an experimental microwave system of
2.3. Temperature control system The optimal temperature of the whole system is fully sustained in the range of 35e37 C by temperature sensors and thermostat valves based on hot water circulation, obtained from the CHPcooling circuit of the electricity generator.
2.5. Compression and storage system The compression and storage system is located ahead of purification sub-system 1, where the CO2 free biogas is compressed at up-to 2400e3000 kPa with the help of a hydraulic compression unit and then conveniently stored in the high pressure storage vessels. (Fig. 2 and 3 part-i). 2.6. Power generation set The electrical power generation set of 150 kW (i.e. 188 kVA approx.) is located after the gas purification sub-system 2 from where it is fed with dry and pure CH4 gas via storage vessels and pressure regulators for the power generation. The NG generator can operate with purified biogas.The gas consumption capacity of this generator set is about 58 m3/hr. i.e. ~600 kJ/s.
Fig. 1. Schematic of Creative bioenergy plant.
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Fig. 2. Multi-digester and lagoon type Bioenergy plant at Lahore, Pakistan. *Note: Figure 2 is intended to be reproduced in colour on the Web (free of charge) and in black-and-white in print. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. Novel bioenergy plant system and parts overview.
3. Cost and benefit analysis 3.1. Operational data The feedstock capacity of plant is 24 tons, initially 20 tons of feedstock was inducted. The 30 days of digestion are required to acclimatize the initial biomass, and then 4 tons of feedstock on daily basis was being added. The average output of this plant has been recorded as 80 m3/ton i.e 320 m3 biogas (CH4) per day with a single feed stock i.e. cow-manure. Similar quantities of biogas were produced and reported in a study using animal manure [17]. At 60vol% methane, the calorific value is approximately 21,521.4 kJ/ Nm3. On average with a single feedstock of cow-manure, an electrical power of up to 4 kWh per m3 of biogas i.e. 16 kWh/4 m3 and 384 kWh energy per day i.e. 11,520 per month was produced using the 150 kW generator having a 38% efficiency (Table 1). Higher gas production rates are possible and experiments are being done in the use of vegetable wastes and sugar molasses [18,19]. The current cost and benefit analysis however is calculated on the basis of project capital costs (Table 2), annual operational and maintenance (O&M) costs which are calculated on the basis of 4 months monitoring study (February to May 2014; Table 1) based on two types of feedstock i.e. pure cow-manure was used for the first two months and cow-manure plus vegetable potato waste in the ratios of 50%e
50% respectively was used for the later months. Specific elements of all expenditures (cash outflow), income (cash inflow) and financial indicators employed for the study are presented in Table 1. 3.2. Project capital cost analysis The project capital costs mainly include the design, engineering, equipment, installations, testing and commissioning costs. for a total of US$ 105,000 as detailed in Table 2. 3.3. Operational and maintenance cost analysis This mainly includes the annual average feedstock (cow-manure and/or potato waste) cost US$ 15,000, wages, salaries, overheads, maintenance and administrative expenses etc. US$ 8400 per annum as detailed in Table 3. 3.4. Financial indicators Four financial indicators have been employed for the economic viability and assessment of the novel industrial scale bioenergy plant. These indicators are; a) net present value (NPV); b) internal rate of return (IRR); like NPV the IRR also reflects the time value of money; c) benefits to costs ratio (B/C ratio) is the ratio among the
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Fig. 4. Cross sectional view of gas filtration unit.
Table 1 Novel bioenergy plant e Monitoring data (FebruaryeMay 2014). Months
Feedstock used
February March
Cow-manure 120 tonnes @ 4 tonne/day Cow-manure 120 tonnes @ 4 tonne/day Average output permonth with cow-manure only ¼ 9600 April Cow-manure 60 tonnes and potato waste 60 tonnes @ 2 þ 2 tonne of each/day May Cow-manure 60 tonnes and potato waste 60 tonnes @ 2 þ 2 tonne of each/day Average output per month with cow-manure þ potato waste ¼ 10,176 Cumulative average output/month ¼ 9888 Forecasted average output/year ¼ 118,656 ± 10%
Biogas produced (m3/month)
Electricity produced(kWh/month)
9448 9753
11,337 11,703 11,520 11,982 12,438 12,210 11,865 142,380 ± 10%
9987 10,365
Table 2 Novel bioenergy plant -project capital costs. Description of item
Cost (US$)
Design & Engineering Preliminary supplies & services Bio-gas plant reactors, gas scrubbers filtration, compressor, storage vessels/cylinders fabrication and civil works etc. Generator set complete with gas de-moisturizing and de-sulphurizing units including construction, fabrication and civil works Transportation, Erection, Testing and Commissioning Management costs, insurance, and other misc. costs Duties and taxes Total Project Capital Cost
2500 5500 26,100 46,000 13,900 5400 5400* 104,800
*Custom duties are calculated @ 5% of the cost of imported equipment and components, no VAT is assumed leviable fore renewable energy projects. Withholding tax on local-preliminary supplies (e.g. sand, crush stone, bricks and cement etc.) and local services for such projects is leviable and calculated @ 6%.
Table 3 Novel bioenergy plant e annual operational and maintenance (O&M) costs. Description of item
Cost/Month (US$)
Cost/Year (US$)
Average cost of 120 tons feedstock; cow-manure @ US$ 10.00 per ton, potato waste @ US$ 10.85 per ton (including freight, transportation and seasonal price variation of ± 20%) Salary and wages Miscellaneous over heads, maintenance and administrative expenses Total O&M Cost
1250
15,000
500 200 1950
6000 2400 23,400
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R. Rasheed et al. / Renewable Energy 90 (2016) 242e247
net present monetary value of benefits and net present monetary value of costs, for a project acceptability and this ratio must be greater than one; and d) payback time (payback period) [20e22]. Typical values and figures of all of these indicators for this creative bio-gas plant are presented in the Table 4. 4. Discussion The novel industrial scale bioenergy system illustrated in Fig. 3 has been successfully launched in the local industry. The initial financial investment of the project is US$ 105,000 including the cost of 150 kW power generation set and O&M cost is US$ 23,400 per year (Tables 1 and 3). The life of the plant is considered as 20 years and the discount rate at 10% per annum, which is set out by the company itself in view of the national economic scenario and local interest rates. This rate allowed computing the present value of financial flows that will take place during future till the project lifecycle. An average price of US$ 0.315 per kWh of energy (electricity) from utility and diesel oil based on self generation has been taken into account for comparison of income and expenditure. On average 11,865 kWh per month of energy (electricity) have been generated during the period of study from FebruaryeMay 2014, with two types of feedstock i.e. pure cow-manure and mix of cowmanure and potato waste. That equates to income (earnings) to US$ 3737 per month and US$ 44,850 per annum. Financial indicators employed for full economic assessment of the project are presented in Table 4. The net present value of the plant has been found to be US$ 57,417. The internal rate of return for this specific project is 19.76% and the benefit to cost ratio is 1.2; which are fairly promising. As further analysed in Fig. 5 the payback time for the plant is 12 years and 8 months, which is slightly high due to inclusion of cost of the power generation set, which is half of the plant's overall project capital cost. These figures are competitive with this size of bioenergy projects as reported in literature [15,17and18] and economic performance of the large scale bioenergy projects can be improved if the investment on major equipment like for fermentation and the generator could be curtailed [17].Where B ¼ benefits in USS$ per year; C ¼ costs in US$ per year; t ¼ 1,2, …, n; i ¼ discount rate (considered at 10%); and life of the bioenergy plant is 20 years. These financial indicators are projected over a life span of 20 years for this plant. Thus such projects appear to be financially and economically feasible as depicted in Fig. 6 where a sensitivity analysis curve shown a direct relationship between the cash inflows and the net present value (NPV). As higher the production and cash inflow the greater the net worth and more successful is the project.
Fig. 5. Novel bioenergy plant e Payback time analysis.
Fig. 6. Sensitivity analysis - Cash inflows vs. NPV.
vegetable wastes etc. The average yearly energy productivities interms of biogas and electricity i.e. 118,656 m3 and 142,380 kWh are highly encouraging in an energy deficient country like Pakistan. The economics and financial indicators of the project especially the net present value of 57,417, cost to benefit ratio of 1.2 and internal rate of return (IRR) of 19.76% have made it reasonably vigorous. This can also thrust a major shift in the energy production, distribution and consumption patterns for rural and commercial communities in Pakistan and is the subject of continuing research.
5. Conclusions Acknowledgements This paper has presented cost-benefits analysis of a new design of industrial scale bioenergy plant in Pakistan. It has been shown its novelty and effectiveness in-terms of multi-digester wells, underground lagoon with ability to continuously utilize 4 tonnes per day of various single or mixed feedstocks like cow-manure and Table 4 Creative bioenergy plant e financial indicators. P BC NPV (US$) IRR (%) t¼n B/C ratio t¼1 ð1þiÞt ¼ 0 Pt¼n Pt¼n BC B=ð1þiÞt t¼1 t¼1 ð1þiÞt Pt¼n t t¼1
57,417
19.76
1.2
The authors wish to acknowledge support from GC University Lahore, University of Nottingham, technical and financial support from The Creative Group of Companies, Lahore Pakistan, The British Council and Charles Wallace Trust. References
Payback time
C=ð1þiÞ
12 years 8 months
Where B ¼ benefits in USS$ per year; C ¼ costs in US$ per year; t ¼ 1,2,….,n; i ¼ discount rate (considered at 10%); and life of the bioenergy plant is 20 years.
[1] Pakistan Economic Survey (2011). Ministry of Finance, Government of Pakistan. [2] World Bank Report (2011). Rural Energy & Development for Two Billion People. [3] Pakistan Energy Yearbook (2011). Hydrocarbon Development Institute of Pakistan, Ministry of Petroleum and Natural Resources, Government of Pakistan. [4] M.H. Sahir, A.H. Qureshi, Assessment of new and renewable energy resources
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[5] [6]
[7]
[8]
[9]
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[12] [13]
potential and identification of barriers to their significant utilization in Pakistan, Renew. Sustain. Energy Rev. 12 (2008) (2008) 290e298. S.S. Amjid, M.Q. Bilal, M.S. Nazir, A. Hussain, Biogas, renewable energy resource for Pakistan, Renew. Sustain. Energy Rev. 15 (6) (2011) 2833e2837. U.K. Mirza, N. Ahmad, K. Harijan, T. Majeed, Identifying and addressing barriers to renewable energy development in Pakistan, Renew. Sustain. Energy Rev. 13 (4) (2009) 927e931. A.A. Shah, S.M. Qureshi, A. Bhutto, A. Shah, Sustainable development through renewable energy-The fundamental policy dilemmas of Pakistan, Renew. Sustain. Energy Rev. 15 (1) (2011) 861e865. M.H. Sahir, A.H. Qureshi, Specific concerns of Pakistan in the context of energy security issues and geopolitics of the region, Energy Policy 35 (2007) (2007) 2031e2037. A.A. Shah, R.S. Rashidi, A. Bhutto, A. Shah, The real life scenario for diffusion of renewable energy technologies (RETs) in PakistaneLessons learned through the pilot field study under physical community, Renew. Sustain. Energy Rev. 15 (5) (2011) 2210e2213. P. Rajabapaiah, S. Jayakumar, A.K. Reddy, Biogas electricityethe Pura village case study, Renew. Energy Sources Fuels Electr. (1993) 787e815. Sinha, C. S. (1990). Techno-economics of Selected Energy Technologies and a Model for Their Optimal Integration in Rural Areas. Ph.D. thesis, Indian Institute of Technology, New Delhi. V.K. Vijay, R. Prasad, J.P. Singh, V.P.S. Sorayan, A case for biogas energy application for rural industries in India, Renew. energy 9 (1) (1996) 993e996. B. Amigun, H. von Blottnitz, Capacity-cost and location-cost analyses for biogas plants in Africa, Resour. Conservation Recycl. 55 (2010) (2004) 63e73.
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ve, R. Dewil, Principles and potential of the [14] L. Appels, J. Baeyens, J. Degre anaerobic digestion of waste-activated sludge, Prog. energy Combust. Sci. 34 (6) (2008) 755e781. [15] K.J. Singh, S.S. Sooch, Comparative study of economics of different models of family size biogas plants for state of Punjab, India, Energy Convers. Manag. 45 (2004) (2004) 1329e1341. [16] R. Dewil, L. Appels, J. Baeyens, Energy use of biogas hampered by the presence of siloxanes, Energy Convers. Manag. 47 (13) (2006) 1711e1722. [17] X. Wang, Y. Chen, P. Sui, W. Gao, F. Qin, X. Wu, J. Xiong, Efficiency and sustainability analysis of biogas and electricity production from a large-scale biogas project in China: an emergy evaluation based on LCA, J. Clean. Prod. 65 (2014) 234e245. [18] C. Zhang, H. Su, J. Baeyens, T. Tan, Reviewing the anaerobic digestion of food waste for biogas production, Renew. Sustain. Energy Rev. 38 (2014) 383e392. ska, Evaluation of a long-term po[19] A. Oniszk-Popławska, M. Matyka, E.D. Ryn tential for the development of agricultural biogas plants: a case study for the Lubelskie Province, Poland, Renew. Sustain. Energy Rev. 36 (2014) 329e349. [20] S. Kothari, N.S. Rathore, N.L. Panwar, Techno economics of greenhouse for cultivation of aswagandha under composite climate of Udaipur, Agric. Eng. Today 25 (3 and 4) (2001) 36e40. [21] Kandpal, T. C., & Grag, H. G. (2003). Financial Evaluation of Renewable Energy Technology. Macmillan India Ltd., Delhi. [22] N.L. Panwar, S. Kothari, S.C. Kaushik, Cost-benefit and systems analysis of passively ventilated solar greenhouses for food production in arid and semiarid regions, Environ. Syst. Decis. 34 (1) (2014) 160e167.
Contents lists available at ScienceDirect
Renewable Energy journal homepage: www.elsevier.com/locate/renene
Design and cost-benefit analysis of a novel anaerobic industrial bioenergy plant in Pakistan Rizwan Rasheed a, *, Naghman Khan b, Abdullah Yasar a, Yuehong Su b, Amtul Bari Tabinda a a b
Sustainable Development Study Centre, Government College University Lahore, Pakistan Department of Architecture and Built Environment, University of Nottingham, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2015 Received in revised form 2 December 2015 Accepted 1 January 2016 Available online xxx
The design and Cost-benefit analysis (CBA) of a novel anaerobic bioenergy plant is presented. This plant can digest various feed sources including animal-manure, vegetable-fruit wastes, poultry wastes, sugar molasses etc. The fixed dome multi-digestor system enables a continuous feed and flow mechanism. It is also equipped with a biogas purification, compression and storage system. This medium scale bioenergy plant is the first of its kind in Pakistan. It has a total installation cost of US$105,000 and annual operation and maintenance cost of US$23,400. The average energy production is 142,380 kWh per annum. With a current average energy cost of US$0.315 per kWh from all sources in Pakistan, the cost-benefit ratio is 1.2 at an internal rate of return (IRR) of 19.76%, and short payback period. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Biogas Bio-fuels Bioenergy generation Pakistan
1. Introduction Pakistan, with its population of approximately 184 million people (growing at 2.2% perannum) has a high rural population. Agriculture accounts for 25% of GDP and employs over 40% of the workforce [1]. Pakistan has a rapidly developing economy with a young population, and significantly rising energy and electricity demand, both towards transportation and industrial/domestic electricity consumption [2]. The installed generating capacity as of 2011 is 21,036 MW. Electricity demand is growing at 9% annually while supply is only at 7%, with an even higher discrepancy in summer [3]. Pakistan has a mix of electricity generation sources including thermal (gas and oil), hydroelectric and nuclear power. Renewables and coal play a minor role at the moment but are expected to increase significantly in the future, as reported [4]: the key renewable resources identified are biomass, wind and solar energy. A more recent study [5] presented an in depth analysis of the biomass potential in Pakistan. Pakistan's livestock inventory is 159 million animals producing almost 652 million kg of manure daily from cattle and buffalo only, which could in theory be used to generate 16.3 million m3 of biogas daily and over 20 million tons of
* Corresponding author. E-mail address: [email protected] (R. Rasheed). http://dx.doi.org/10.1016/j.renene.2016.01.008 0960-1481/© 2016 Elsevier Ltd. All rights reserved.
fertilizer annually. The study also cites a government program to install 10,000 domestic biogas units over the next five years, thus saving millions of $ annually in substituting fossil fuel costs. There are however significant barriers and obstacles to fully develop this potential [6e9]. The development of biogas, although started in the 1980s, remains an economic issue and a comparison with mostly natural gas and LPG will determine its growth. This paper presents a cost and benefit analysis of novel design of bioenergy plant on an industrial scale. It is the first plant of its kind in Pakistan, despite a few industrial scale bioenergy projects having been designed and implemented in the sub-continent and reported in literature [10,11] for cottage/small scale industries like milling, grinding, cutting, water pumping and in some related manufacturing activities. A study in rural India [12] reported that most rural people are not ready to accept the use of electricity generated from biomass sources, due to cost and logistical problems. A study conducted in twelve African countries on 38 bioenergy installations has indicated that economies of scale were not prominent for the small to institutional scale bioenergy plants which is opposing the general, conventional financial mindset of the industry that bigger bioenergy installations are advantageous in-terms of economies of scale. It was also concluded by the study that the technology of bioenergy is mostly independent of geographical setting of such plants [13,14]. A comparative Indian economic study [15] of 1e6 m3
R. Rasheed et al. / Renewable Energy 90 (2016) 242e247
243
sized biogas plants, which were of the conventional single digester with fixed dome or floating drum design, found that the installation and operational cost increased proportionally with the installed capacity of the biogas plant, irrespective of the biogas plant type. These plants have low biogas outputs of 1 m3/25 kg i.e. 40 m3/tonne of cow-manure as compared to our novel multidigester and lagoon based continuous flow design which produced 80e90 m3/tonne of biogas with cow-manure. Of course, the financial payback period decreases dramatically with the increase in installed capacity. The present research follows the above said studies in assessing the systems and cost-benefit analysis of our new industrial scale bioenergy plant and this forms part of continuing research. Comparative economic studies and life cycle cost-benefit assessments are also being conducted similar to those applied in Refs. [13] and [15].
2500 MHz frequency for which a set of electronic magnetrons of 5600 V are installed over the dome of the digestion well 1 (Fig. 1). Microwaves are only used for shorter specific time intervals of 5e10 min for rapid temperature enhancement, initiation of methanogenesis and faster decomposition of substrate molecules when fresh feedstock is inducted on daily basis.
2. Plant design analysis
2.4. Water scrubbers and filtration system
The current bioenergy plant design is a modified and mixed form of a fixed dome anaerobic digester (AD), continuous stirring tank reactor (CSTR) and lagoon. This design establishes a continuous feed and flow system with the ability to handle single to multiple-mixed organic feedstock, from animal manure to poultry waste and sugar molasses etc. It also has the provisions of bioenergy purification, compression and storage. A schematic of this plant is shown in Fig. 1. The actual plant picture is presented in Fig. 2. The salient design features are elaborated in the following sections.
The bioenergy scrubbing and filtration system consists of two sub-systems. The first one, prior to the compression and storage is based on three interconnected filtration chambers made of fibreglass reinforced polymer (FRP) material in cylindrical shape each having size: 2.01 m (height) 1.21 m (diameter). These are attached with gas collection piping system (Fig. 3 and part-h) for the removal of CO2 with the help of special water scrubbers, using 5 mm FRP composite inner dish type filters, with 10 C water and incoming gas pressure at 2.24 MPa (325 psi). Secondly, activated carbon filter is used to eliminate certain sulphides and siloxanes from biogas [16], and silica gel filter is utilized for the removal of water contents subsequently. These filters have a useful life of 3e5 years. The cross-sectional view of the gas filtration unit is shown in Fig. 4. Air cooled medium at 6 C is used for water-moisture removal (Figs 2 and 3 part-j).
2.1. Multistage anaerobic digester (AD) with lagoon This experimental plant uses a fixed dome type multistage (three) anaerobic digesters each of 4.26 m (height) 4.26m (diameter) size. These are interconnected with an underlying lagoon of the size of 26.03 m (length) 1.52 m (width) 1.7 m (height) to manage the continuous feed intake, slurry outflow and enhance the gas output (Fig. 3, part-b). The lagoon is directly connected with the mechanically stirred inlet tank to allow different input feedstock. All the digesters and lagoon are built of concrete. The fixed dome digesters are covered with seamless, antirust, lightweight and durable FRP (fibreglass reinforced polymer) composite domes (top covers). The gas collection (output) points are located right over each dome, and interlinked with a common piping for gas collection. 2.2. CSTR and microwave system Digester No 1 and 3 also function as CSTR (continuous stirring tank reactors), as these are equipped with mechanical agitators, driven by an electrical motor (2 HP; 1100 RPM; 460 V). Digester 1 is also provided with an experimental microwave system of
2.3. Temperature control system The optimal temperature of the whole system is fully sustained in the range of 35e37 C by temperature sensors and thermostat valves based on hot water circulation, obtained from the CHPcooling circuit of the electricity generator.
2.5. Compression and storage system The compression and storage system is located ahead of purification sub-system 1, where the CO2 free biogas is compressed at up-to 2400e3000 kPa with the help of a hydraulic compression unit and then conveniently stored in the high pressure storage vessels. (Fig. 2 and 3 part-i). 2.6. Power generation set The electrical power generation set of 150 kW (i.e. 188 kVA approx.) is located after the gas purification sub-system 2 from where it is fed with dry and pure CH4 gas via storage vessels and pressure regulators for the power generation. The NG generator can operate with purified biogas.The gas consumption capacity of this generator set is about 58 m3/hr. i.e. ~600 kJ/s.
Fig. 1. Schematic of Creative bioenergy plant.
244
R. Rasheed et al. / Renewable Energy 90 (2016) 242e247
Fig. 2. Multi-digester and lagoon type Bioenergy plant at Lahore, Pakistan. *Note: Figure 2 is intended to be reproduced in colour on the Web (free of charge) and in black-and-white in print. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. Novel bioenergy plant system and parts overview.
3. Cost and benefit analysis 3.1. Operational data The feedstock capacity of plant is 24 tons, initially 20 tons of feedstock was inducted. The 30 days of digestion are required to acclimatize the initial biomass, and then 4 tons of feedstock on daily basis was being added. The average output of this plant has been recorded as 80 m3/ton i.e 320 m3 biogas (CH4) per day with a single feed stock i.e. cow-manure. Similar quantities of biogas were produced and reported in a study using animal manure [17]. At 60vol% methane, the calorific value is approximately 21,521.4 kJ/ Nm3. On average with a single feedstock of cow-manure, an electrical power of up to 4 kWh per m3 of biogas i.e. 16 kWh/4 m3 and 384 kWh energy per day i.e. 11,520 per month was produced using the 150 kW generator having a 38% efficiency (Table 1). Higher gas production rates are possible and experiments are being done in the use of vegetable wastes and sugar molasses [18,19]. The current cost and benefit analysis however is calculated on the basis of project capital costs (Table 2), annual operational and maintenance (O&M) costs which are calculated on the basis of 4 months monitoring study (February to May 2014; Table 1) based on two types of feedstock i.e. pure cow-manure was used for the first two months and cow-manure plus vegetable potato waste in the ratios of 50%e
50% respectively was used for the later months. Specific elements of all expenditures (cash outflow), income (cash inflow) and financial indicators employed for the study are presented in Table 1. 3.2. Project capital cost analysis The project capital costs mainly include the design, engineering, equipment, installations, testing and commissioning costs. for a total of US$ 105,000 as detailed in Table 2. 3.3. Operational and maintenance cost analysis This mainly includes the annual average feedstock (cow-manure and/or potato waste) cost US$ 15,000, wages, salaries, overheads, maintenance and administrative expenses etc. US$ 8400 per annum as detailed in Table 3. 3.4. Financial indicators Four financial indicators have been employed for the economic viability and assessment of the novel industrial scale bioenergy plant. These indicators are; a) net present value (NPV); b) internal rate of return (IRR); like NPV the IRR also reflects the time value of money; c) benefits to costs ratio (B/C ratio) is the ratio among the
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Fig. 4. Cross sectional view of gas filtration unit.
Table 1 Novel bioenergy plant e Monitoring data (FebruaryeMay 2014). Months
Feedstock used
February March
Cow-manure 120 tonnes @ 4 tonne/day Cow-manure 120 tonnes @ 4 tonne/day Average output permonth with cow-manure only ¼ 9600 April Cow-manure 60 tonnes and potato waste 60 tonnes @ 2 þ 2 tonne of each/day May Cow-manure 60 tonnes and potato waste 60 tonnes @ 2 þ 2 tonne of each/day Average output per month with cow-manure þ potato waste ¼ 10,176 Cumulative average output/month ¼ 9888 Forecasted average output/year ¼ 118,656 ± 10%
Biogas produced (m3/month)
Electricity produced(kWh/month)
9448 9753
11,337 11,703 11,520 11,982 12,438 12,210 11,865 142,380 ± 10%
9987 10,365
Table 2 Novel bioenergy plant -project capital costs. Description of item
Cost (US$)
Design & Engineering Preliminary supplies & services Bio-gas plant reactors, gas scrubbers filtration, compressor, storage vessels/cylinders fabrication and civil works etc. Generator set complete with gas de-moisturizing and de-sulphurizing units including construction, fabrication and civil works Transportation, Erection, Testing and Commissioning Management costs, insurance, and other misc. costs Duties and taxes Total Project Capital Cost
2500 5500 26,100 46,000 13,900 5400 5400* 104,800
*Custom duties are calculated @ 5% of the cost of imported equipment and components, no VAT is assumed leviable fore renewable energy projects. Withholding tax on local-preliminary supplies (e.g. sand, crush stone, bricks and cement etc.) and local services for such projects is leviable and calculated @ 6%.
Table 3 Novel bioenergy plant e annual operational and maintenance (O&M) costs. Description of item
Cost/Month (US$)
Cost/Year (US$)
Average cost of 120 tons feedstock; cow-manure @ US$ 10.00 per ton, potato waste @ US$ 10.85 per ton (including freight, transportation and seasonal price variation of ± 20%) Salary and wages Miscellaneous over heads, maintenance and administrative expenses Total O&M Cost
1250
15,000
500 200 1950
6000 2400 23,400
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net present monetary value of benefits and net present monetary value of costs, for a project acceptability and this ratio must be greater than one; and d) payback time (payback period) [20e22]. Typical values and figures of all of these indicators for this creative bio-gas plant are presented in the Table 4. 4. Discussion The novel industrial scale bioenergy system illustrated in Fig. 3 has been successfully launched in the local industry. The initial financial investment of the project is US$ 105,000 including the cost of 150 kW power generation set and O&M cost is US$ 23,400 per year (Tables 1 and 3). The life of the plant is considered as 20 years and the discount rate at 10% per annum, which is set out by the company itself in view of the national economic scenario and local interest rates. This rate allowed computing the present value of financial flows that will take place during future till the project lifecycle. An average price of US$ 0.315 per kWh of energy (electricity) from utility and diesel oil based on self generation has been taken into account for comparison of income and expenditure. On average 11,865 kWh per month of energy (electricity) have been generated during the period of study from FebruaryeMay 2014, with two types of feedstock i.e. pure cow-manure and mix of cowmanure and potato waste. That equates to income (earnings) to US$ 3737 per month and US$ 44,850 per annum. Financial indicators employed for full economic assessment of the project are presented in Table 4. The net present value of the plant has been found to be US$ 57,417. The internal rate of return for this specific project is 19.76% and the benefit to cost ratio is 1.2; which are fairly promising. As further analysed in Fig. 5 the payback time for the plant is 12 years and 8 months, which is slightly high due to inclusion of cost of the power generation set, which is half of the plant's overall project capital cost. These figures are competitive with this size of bioenergy projects as reported in literature [15,17and18] and economic performance of the large scale bioenergy projects can be improved if the investment on major equipment like for fermentation and the generator could be curtailed [17].Where B ¼ benefits in USS$ per year; C ¼ costs in US$ per year; t ¼ 1,2, …, n; i ¼ discount rate (considered at 10%); and life of the bioenergy plant is 20 years. These financial indicators are projected over a life span of 20 years for this plant. Thus such projects appear to be financially and economically feasible as depicted in Fig. 6 where a sensitivity analysis curve shown a direct relationship between the cash inflows and the net present value (NPV). As higher the production and cash inflow the greater the net worth and more successful is the project.
Fig. 5. Novel bioenergy plant e Payback time analysis.
Fig. 6. Sensitivity analysis - Cash inflows vs. NPV.
vegetable wastes etc. The average yearly energy productivities interms of biogas and electricity i.e. 118,656 m3 and 142,380 kWh are highly encouraging in an energy deficient country like Pakistan. The economics and financial indicators of the project especially the net present value of 57,417, cost to benefit ratio of 1.2 and internal rate of return (IRR) of 19.76% have made it reasonably vigorous. This can also thrust a major shift in the energy production, distribution and consumption patterns for rural and commercial communities in Pakistan and is the subject of continuing research.
5. Conclusions Acknowledgements This paper has presented cost-benefits analysis of a new design of industrial scale bioenergy plant in Pakistan. It has been shown its novelty and effectiveness in-terms of multi-digester wells, underground lagoon with ability to continuously utilize 4 tonnes per day of various single or mixed feedstocks like cow-manure and Table 4 Creative bioenergy plant e financial indicators. P BC NPV (US$) IRR (%) t¼n B/C ratio t¼1 ð1þiÞt ¼ 0 Pt¼n Pt¼n BC B=ð1þiÞt t¼1 t¼1 ð1þiÞt Pt¼n t t¼1
57,417
19.76
1.2
The authors wish to acknowledge support from GC University Lahore, University of Nottingham, technical and financial support from The Creative Group of Companies, Lahore Pakistan, The British Council and Charles Wallace Trust. References
Payback time
C=ð1þiÞ
12 years 8 months
Where B ¼ benefits in USS$ per year; C ¼ costs in US$ per year; t ¼ 1,2,….,n; i ¼ discount rate (considered at 10%); and life of the bioenergy plant is 20 years.
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