Available online at www.sciencedirect.com ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2017) 000–000 ScienceDirect ScienceDirect www.elsevier.com/locate/procedia Energy (2017) 000–000 655–660 EnergyProcedia Procedia142 00 (2017) www.elsevier.com/locate/procedia 9th International Conference on Applied Energy, ICAE2017, 21-24 August 2017, Cardiff, UK Assessment of Bioenergy Production from Solid Waste The 15th International Symposium on District Heating and Cooling Iqra Samuna, Rashid Saeeda, Mohsin Abbasa, Mohammad Rehanb, Abdul-Sattar a, demand-outdoor Assessing the feasibility of using the heat Nizamib,* Zaki-ul-Zaman Asam † Department of Environmental Sciences, Universitydistrict of Gujrat, Gujrat, Pakistan temperature function for a long-term heat demand forecast a Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah, Saudi Arabia b Abstract a I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France study aims to examine the biogas potential for animal manure, wheat straw, food waste and rice straw. Batch c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France This experiments were performed at a laboratory scale using biomethane potential (BMP) assays for a period of 50 days. The biogas yield was observed higher when using rice straw (0.51 m3/kg VSadded) as a substrate, as compared to wheat straw (0.44 m3/kg VSadded) and animal manure (0.31 m3/kg VSadded) substrates. Around 12-25% of biogas was produced inAbstract the initial phase of 5 days for manure, wheat straw, and rice straw feedstocks. During the middle phase of 33 days for these feedstocks, 68-80% of biogas was produced. Less than 8% of biogas was produced during the final phase of District heating networks are commonly addressed in thefrom literature as onewas of the mostlowest effective solutions for added decreasing the ) among last 12 days of the experiment. The biogas production food waste found (0.17 m3/kg VS emissions the fromco-digestion the building of sector. require high investments which are returned through theand heat allgreenhouse substrates.gas Therefore, foodThese wastesystems and animal manure is more appropriate with wheat straw sales. Duethan to the changed climate conditions higher and building policies, heat demand in the future could decrease, rice straw mono-digestion for achieving biogasrenovation production. prolonging the investment return period. main of this paper isbytoElsevier assess the feasibility of using the heat demand – outdoor temperature function for heat demand ©The 2017 Thescope Authors. Published Ltd. forecast. The district of Alvalade, in committee Lisbon (Portugal), used as aConference case study.onThe district is consisted of 665 Peer-review under responsibility of thelocated scientific of the 9thwas International Applied Energy. buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, To estimate the error, obtained heat demand values were Keywords: Bioenergy; Solid waste; Waste to energy; Anaerobic digestiondeep). (AD); Biogas compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation 1.(the Introduction scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the The sustainable management of solid waste has become a strategic issue in most of the developing countries due to decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and low budgetsscenarios and poorconsidered). administrative practices [1]. function A significant portion of the wasteper is decade either not collected renovation On the other hand, intercept increased for solid 7.8-12.7% (depending on or the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. *©Corresponding author. Published Tel.: +966-598293542; 2017 The Authors. by Elsevierfax: Ltd.+966-12-6951674. E-mail address: anizami@kau.edu.sa; nizami_pk@yahoo.com Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and †Cooling. Corresponding author. Tel.: +92-300-0952675. E-mail address: zaki.asam@uog.edu.pk Keywords: Heat demand; Forecast; Climate change 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 9th International Conference on Applied Energy. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 9th International Conference on Applied Energy. 10.1016/j.egypro.2017.12.108 656 2 Iqra Samun et al. / Energy Procedia 142 (2017) 655–660 Author name / Energy Procedia 00 (2017) 000–000 disposed of in the landfills untreated. As a consequence, solid waste is often smoldered, covered or dumped in streets, channels, riverbanks, and seashore [2]. This unregulated disposal of waste results in several environmental and public health problems in the form of surface and groundwater contamination through leachate, and diseases like malaria, cholera, and typhoid through vectors, rodents, and flies [3]. In addition, the emission of greenhouse gases (GHG) such as methane (CH4) and carbon dioxide (CO2) are causing climate change [4]. In developed countries, solid waste is often viewed as an asset of recyclable materials, energy, and revenue, if wisely managed [5-8]. An efficient way to manage the solid waste is to produce energy and value-added products from waste. There are different thermal, biological and chemical conversion technologies to recover energy and fuels from various waste sources, including anaerobic digestion (AD), fermentation, gasification, pyrolysis, hydrolysis, and incineration [9,10]. However, AD provides a coordinated system of renewable energy production, resources utilization, organic waste treatment and nutrient recycling along with improved farming and environmental benefits. Furthermore, AD brings a variety of business sectors such as power, heat, and transportation energy at one platform [11]. The utilization of biogas in stoves and gas lamps at homes is practiced in many developing countries, whereas creating power from biogas or using it as a compressed natural gas (CNG) after upgrading is common in developed countries [12]. AD is a controlled biological degradation process that permits efficient production and utilization of biogas [11]. The biogas consists of approximately 60% CH4 and 40% CO2 [11-13]. Besides the biogas, a nutrient-rich digestate is produced that can be used as an organic fertilizer to improve the fertility of soils and plants growth and development [13]. AD is accomplished by certain kinds of anaerobic bacteria such as acidogenic, acetogenic and methanogenic. Therefore, the process includes a complex series of reactions that degrade the organic materials to carbon molecules, then into CO 2 and finally in CH4 [14-16]. Different studies have been carried out to enhance the rates of biogas production as well as the potential of biogas. For example, the energy crops are developed with an ambition to increase the biogas yield [12-16]. Similarly, the various pretreatment methods such as optimum temperature, thermochemical pretreatment, and wet oxidation methods are evolved [11,15,16]. These pretreatment techniques make the process faster, enhance the CH4 production, make utilization of new and locally accessible substrates, and prevent processing problems such as high electricity requirements for mixing of feedstocks [11]. Recently, the pretreatment of animal manure by separating the high concentrated solid is getting significant attention to enhance CH4 production per waste volume and ultimately per unit of digester volume [11-13]. The transportation of animal slurry from the farm to the biogas plant adds an extra cost to the AD plants. Therefore, the co-digestion of animal manure with the organic fraction of municipal solid waste (OFMSW) and agricultural residues such as wheat straw and rice straw could reduce the overall process cost and increase the CH4 yield per unit of digester volume [11,15,16]. This study aims to examine the biogas production of locally produced wastes including rice straw, wheat straw, food waste and manure. Laboratory-scale batch experiments were performed to determine the total biogas production per kg of volatile solids added (m3/kg VSadded). The challenges and future perspectives on utilizing various waste sources for optimized biogas production are also discussed. 2. Material and Methods 2.1 Preparation of feedstocks The feedstocks used in this study were manure, wheat straw, food waste and rice straw (Figure 1). Rice straw and wheat straw were collected from a local farm located around 1 km North of University of Gujrat, Pakistan. Food waste was collected from the local hotels of Gujrat city, and manure was collected from a local farm located near University of Gujrat, Pakistan. Rice straw and wheat straw were already shredded into small pieces when received from the farm. Whereas, the food waste was shredded into small pieces with the help of a chopper. All these materials were stored in closed containers at room temperature till used. The inoculum was collected from a village called Chak Dadan in Gujranwala district of Pakistan and was stored at room temperature in a closed container until it was used. Iqra Samun et al. / Energy Procedia 142 (2017) 655–660 Author name / Energy Procedia 00 (2017) 000–000 Manure Wheat straw Food waste Rice straw 657 3 Figure 1. Feedstocks used in the batch experiments of AD 2.2 Experimental setup Biomethane potential (BPM) assays bottles of 500 ml each were used for all batch experiments in this study. Different feedstocks were placed in the BMP bottles after determining their dry solid (DS) and volatile solid (VS) contents followed by the addition of inoculums according to pre-decided feedstocks to inoculum ratios (Table 1). These ratios were decided to keep the same DS contents at the start of the experiment in all BPM bottles for different materials. There were 5 samples in total including the blank sample. All 5 samples were tested in triplicate in BMP bottles (Figure 2). A ratio of 5 g DS:100 g inoculum was used for each feedstock type. The BMP bottles were purged with nitrogen gas to remove any air within the bottles. Afterward, the bottles were fully closed by the rubber stoppers and metal screw caps. The effect of inoculum on gas production was estimated using a blank sample by adding 100 g of inoculum without any feedstock. All of the BMP bottles were operated at the mesophilic temperature range (37.5 °C). Table 1. Different feedstocks and their rations with inoculum Feedstocks Feedstock to inoculum ratio Equivalent dry solids (5 g DS : 100 g) (DS) in BPM Equivalent volatile solids (VS) in BPM Manure 19.16 g 5.0 g 2.3 g Wheat straw 5.5 g 5.0 g 4.91 g Food waste 35.15 g 5.0 g 4.54 g Rice straw 5.34 g 5.0 g 4.20 g 2.3 Analytical methods All of the feedstocks were analyzed for DS and VS contents before being digested in the BPM bottles (Figure 2). Similarly, the DS and VS contents of the digestate were measured at the end of the experiment when there was no further biogas production. In all assays, triplicate samples were taken. The DS contents were measured by drying a known mass of the sample (Ws) in an oven at 105 °C for 24 hours. After drying, the dry mass (WDM) was measured 658 4 Iqra Samun et al. / Energy Procedia 142 (2017) 655–660 Author name / Energy Procedia 00 (2017) 000–000 and accordingly the DS contents by the expression of DS (%) = 100 × WDM / Ws. The VS contents were determined by burning the dried samples at 550 °C in a muffle furnace for 12 hours. After, the weight of ash (W ash) was measured and accordingly the final VS contents by using the expression of VS (%) = (100 × (WDM - Wash)/ WDM. At the start of the experiment, the VS content of the feedstocks (VSs) was determined, whereas, the VS of the digested mixture (VSm) and inoculum (VSi) were determined after 50 days of the experiment. For feedstock’s VS contents, the standard expression of VSs - (VSm - VSi) was used. The biogas yield was measured daily in initial 2 weeks, then in the 3rd week measurement was decreased to 2 days using a syringe technique [11]. The frequency was further reduced to every 3rd day in the 4th week and afterward in the 5th week 2 times and once in the last weeks. The composition of biogas was measured using a Gas Chromatograph (GC). Figure 2. BMP bottles stored in oven at 37.5 °C 3. Results and Discussion 3.1 The variations in biogas production The biogas production from animal manure, wheat straw, food waste, rice straw and inoculum was measured for 50 days. In most cases, the quantity of biogas produced from triplicate samples showed variation. The variation of biogas production (between triplicates) from different substrates during the batch experiment can be seen in Figure 3. Overall, it was observed that the biogas production was more when the bottles were regularly mixed during the digestion process. This indicates the need for a regular mixing to enable bacterial communities to digest the organic matter more efficiently. In addition, it was observed that there are three different phases of degradation. In the start, after 5 days, there was a rapid biogas production because easily degradable organic matter was digested. After 30 days, the biogas rates become less, which indicate the degradation of the complex organic matter by microorganisms. This phase was continued till the last days with little increase in cumulative biogas (Figure 3). After 40 days of digestion period, microorganisms depleted the available organic matter and entered into a stationary phase characterized by very low degradation of residual biodegradable material (Figure 3). 3.2 Biogas production from manures, wheat straw, food waste, and rice straw The cumulative biogas production from all feedstock sources including; manure, wheat straw, food waste and rice straw, are shown in Figure 3. The total amounts of biogas produced by rice straw were 0.51 m3/kg VSadded, wheat straw was 0.44 m3/kg VSadded, animal manure was 0.31 m3/kg VSadded, and food waste was 0.17 m3/kg VSadded in 50 days (Figure 3). It was observed that the biogas production rates, except for food waste, were slow at the beginning. After few days, the production rate increased and then started to level off for the last few days of the experiment. The biogas yields period was broken into three phases; initial phase (first 5 days), middle phase (day 5-38) and final phase (day 38-50). Around 7-25% of biogas was produced in the initial phase of 5 days for manure, wheat straw, and rice straw feedstocks. During the middle phase of 33 days for these feedstocks, 68-80% of biogas was produced. Less than 16% of biogas was produced during the final phase of last 12 days of the experiment. This shows that the retention time should be shorter for the duration of digestion. For manure feedstock, 11.9% of biogas was produced during the initial phase, 80.1% in middle phase and 8.0% in the final phase. The highest amount of 25.2% biogas was produced Iqra Samun et al. / Energy Procedia 142 (2017) 655–660 Author name / Energy Procedia 00 (2017) 000–000 659 5 during the initial phase for wheat straw feedstock, 67.8% for middle phase and 7.0% for the final phase. Similarly, the rice straw feedstock produced 21.6, 71.0 and 7.4% of biogas during the initial, middle and final phases respectively. Manure 8.0% 80.1% 11.9% Wheat straw 7.0% 67.8% 25.2% Food waste 76.1% 16.5% 7.4% Rice straw 7.4% 71.0% 21.6% Figure 3. Biogas production (m3/Kg VSadded) from animal manure, wheat straw, food waste and rice straw The food waste produced the lowest amounts of biogas as compared to other feedstocks (Figure 3). On the 5th day, it produced a total biogas of only 0.01 m3/kg VSadded, which slowly increased and reached up to 0.14 m3/kg VSadded by day 38 and the maximum amount of 0.17 m3/kg VSadded by day 50. The microorganisms might have consumed the accessible organic matter after few days and entered into a stationary phase characterized by low production of biogas 660 6 Iqra Samun et al. / Energy Procedia 142 (2017) 655–660 Author name / Energy Procedia 00 (2017) 000–000 [11,16]. The possible reasons of lower biogas production from food waste, as per the number of studies could be due to a higher release of volatile fatty acids (VFAs) in leachate and larger particle size [11-16]. 3.3 Future Perspectives Rice straw and wheat straw have a high biogas potential, and the use of these substrates would increase the biogas production and ultimately the CH4 yield of the biogas. The cost effective and efficient utilization of biomass in biogas plants has an incredible potential in Pakistan, particularly when the country is facing massive energy crises. Biogas plants rely on a constant supply of feedstocks round the year for an economic process output. Therefore, it is critical to explore alternative substrates with high biogas yield potential. The procedure of scattering of new biomass technologies could be supported by building up awareness of the environmental issues among the local population. The reinforcing and adequacy of research institutes of the country are additional elements for the success of waste to energy. Moreover, a focus should be given on the system level, including the potential in certain areas and regions based on the availability of feedstocks, how large should a treatment facility be in respect to the transportation, and what is the best utilization of the biogas, including its techno-economic assessment [16,17]. 4. Conclusions The biogas production of different substrates such as animal manure, wheat straw, food waste and rice straw was successfully carried out at laboratory scale batch experiments. Biomethane potential (BMP) assays were used to determine the biogas yields for a total duration of 50 days at mesophilic temperature (37.5 °C). The biogas production in all feedstocks followed the standard curve of biogas; production started in initial days, achieved highest peaks and then leveled off. In rice straw (0.51 m3/kg VSadded) and wheat straw (0.44 m3/kg VSadded), biogas productivity was observed higher. Whereas, from animal manure (0.31 m3/kg VSadded) and food waste (0.17 m3/kg VSadded), the average biogas production was lower. Therefore, co-digestion of animal manure and food waste are more suited with wheat straw and rice straw than mono-digestion for achieving higher biogas production. References [1] Ouda OKM, Raza SA, Nizami AS, Rehan M, et al. Waste to energy potential: A case study of Saudi Arabia. Renew Sust Energ Rev 2016;61:328-340. [2] Sadef Y, Nizami AS, Batool SA, Chaudhary MN, Ouda OKM, Asam ZZ, Habib K, Rehan M, Demibras A. Waste-to-energy and recycling value for developing integrated solid waste management plan in Lahore. Energy Sources Part B 2016;11:571-581. [3] Rahmanian N, Bt Ali SH, Homayoonfard M, Ali NJ, Rehan M, Sadef Y, Nizami AS. Analysis of physiochemical parameters to evaluate the drinking water quality in the state of Perak, Malaysia. 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