Anaerobic Digestion Of Slaughterhouse Waste Research Articles

Potential of Biogas and Organic Fertilizers Production through Anaerobic Digestion of Slaughterhouse Waste in Ouagadougou, Burkina Faso

Potential of Biogas and Organic Fertilizers Production through Anaerobic Digestion of Slaughterhouse Waste in Ouagadougou, Burkina Faso

Influence of the Construction Materials Properties of the Biodigester on the Biogas Production and Electricity Generated by the Slaughterhouse Waste

The objective of this study was to carry out a comparative analysis of the influence of the properties of the construction materials of the biodigester based on three different materials (steel, plastic PVC, and concrete) to predict the rate of biogas production from the anaerobic digestion of slaughterhouse waste. The input parameters were substrate temperature, ambient temperature, biogas temperature, biodigester temperature, specific biogas production rate, and material properties. A thermal model was developed using MATLAB® software to predict biogas production, with readily available input data for an unheated, uninsulated, and partially buried biodigester. The results obtained showed that the temperatures and the average daily biogas productions were higher for the steel biodigester (1.5 ± 0.12 m3/day at 36 ± 2℃) than those produced from the PVC (1.3 ± 0.1 m3/day at 31 ± 1.5℃) and concrete (1.2 ± 0.05 m3/day at 27 ± 2℃) biodigesters. Moreover, the production of electricity for a steel biodigester (14.64 kWh) was found to be greater than that produced from the PVC (12.81 kWh) and concrete (10.98 kWh) biodigesters. The results showed that the properties of the construction materials of the digester had a significant influence on the temperature and production of biogas, and therefore on the production of electricity. On the other hand, among the three materials studied, steel was the material, which yielded the best results. The proposed model gave rRMSE values between 7.4 and 8.3% and R2 between 0.92 and 0.96.

Anaerobic digestion of slaughterhouse waste in batch and anaerobic sequential batch reactors

Anaerobic digestion of slaughterhouse waste in batch and anaerobic sequential batch reactors

Estimating the potential of energy generation by anaerobic digestion of slaughterhouse wastes toward sustainable waste management strategy: a case study

ABSTRACT While producing and consuming vast amounts of energy, Iran has lagged behind its peers in the use of renewable energies, such as bioenergy. The present study was an attempt to estimate the potential of energy generation by the anaerobic digestion of organic matter produced in Iranian slaughterhouses, recruiting a waste-management and greenhouse gas (GHG) emission reduction approach. Accordingly, the type and amount of slaughterhouse wastes (SHWs) produced in different provinces were identified, and then the potential of methane (CH4) production at the provincial and national scales was estimated. The results showed that, theoretically, there was the potential for producing 111 million cubic meters per year (m3/yr) of CH4 from SHWs, which, if fed into combined heat-power (CHP) plants, could ideally produce 1,004 gigawatt-hour (GWh) of electricity. This would also enhance the share of renewable resources in Iran’s total energy supply by 4%. Exploiting biogas produced by anaerobic digestion instead of traditional fossil fuels would thus reduce Iran’s annual carbon dioxide (CO2) emissions by 482,000 tonnes. Correspondingly, the economic analysis of the energy and social costs of CO2 emissions revealed that energy generation by the anaerobic digestion of SHWs could lead to an annual cost-saving of about $102 million.

A review of anaerobic digestion of slaughterhouse waste: effect of selected operational and environmental parameters on anaerobic biodegradability

A review of anaerobic digestion of slaughterhouse waste: effect of selected operational and environmental parameters on anaerobic biodegradability

Effect of mixing ratios of natural inorganic additives in removing ammonia and sulfide in the liquid phase during anaerobic digestion of slaughterhouse waste

In this study, the efficacy of inorganic additives in the removal of total ammonia nitrogen (TAN) and sulfide in the aqueous phase of slaughterhouse waste undergoing anaerobic digestion in the batch reactor was investigated. A mixture of natural inorganic additives processed from the anthill and red rock soil samples collected from Arusha, Tanzania were used as adsorbents in different ratios. These materials were chosen in regard to their abundance in the local environment, surface properties, and elemental composition. Before analysis, the materials were pulverized and calcined at 700 and 900 °C for 2 h in a furnace and then sieved to 250 μm fine particle size. XRD analysis revealed that the anthill soil sample is endowed with major mineral phases of quartz and hematite while red rock soil contains albite, pyroxene, and quartz as predominant phases. The anthill and red rock soil samples calcined at 900 °C displayed higher BET surface areas of 815.35 and 852.35 m2/g, respectively. The mixture of anthill soil and red rock soil in a ratio of 3:1 had a higher TAN removal efficiency of 92% at a contact time of 30 min compared to other ratios. On the other hand, a ratio of 1:2 showed a higher sulfide removal efficiency of 79% at a contact time of 60 min. Adsorption isotherm studies revealed that the Jovanovich model fitted better to the experimental data than the Langmuir and Freundlich models. The results demonstrated further that inorganic additives have a synergistic effect on stimulating methanogenesis as well as eliminating ammonia and sulfide during anaerobic digestion of slaughterhouse waste. Our findings demonstrate that anthill and red rock soils can be exploited as affordable, ecofriendly, and efficient adsorbents for mitigation of TAN and sulfide from the liquid phase and sustenance of methanogenesis.

Life-cycle assessment of treating slaughterhouse waste using anaerobic digestion systems

The meat industry in the US generates considerable amount of slaughterhouse waste (SHW), which is typically converted into more useable products through the rendering process. Although rendering generates sellable fat and meal commodities, it has large environmental impacts because it is energy intensive. Anaerobic digestion (AD) is a promising technology for treating SHW and reducing environmental impact through biogas production to generate heat or electricity, as well as by enabling nutrient recovery and pathogen reduction. This study compared the life-cycle energy use and global warming impact of treating SHW with traditional rendering with AD to produce heat and electricity. The study also considered the co-digestion of SHW with the organic fraction of municipal solid waste (OFMSW) and sewage sludge. A cradle-to-grave life-cycle assessment (LCA) method was used to quantify the energy use and greenhouse gas (GHG) emissions of these systems for treating SHW. We compared three scenarios: (1) AD of SHW, (2) Co-AD of SHW with OFMSW, and (3) Co-AD of SHW with sewage sludge to reference systems of simple rendering and composting. The study findings revealed that the total cradle-to-gate energy use and GHG emissions by treating SHW with AD and co-AD were 0.5−6.7 GJ/1000 kg-SHW and 400−834 kg-CO₂-eq/1000 kg-SHW, whereas for the rendering control scenarios total cradle-to-gate energy use and GHG emissions were 1.9 GJ/1000 kg-SHW and 96.4 kg-CO₂-eq/1000 kg-SHW, respectively. However, considering all the benefits of treating SHW with co-AD, including the displacement of fossil fuel and electricity and nitrogen fertilizers generated as system outputs, these systems perform better than the rendering process. Compared to the reference systems, the GHG reduction potential of treating SHW with co-AD varied between 426.8 and 524.0 kg-CO₂-eq/1000 kg-SHW. Among all input parameters, methane (CH₄) leak from the AD system, and nitrogen fertilizer displacement were the most sensitive parameters affecting the results. By implementing AD of SHW in meat industries in the southeast US, the energy production and GHG emissions reduction potential were estimated to be 22–29 × 10⁶ GJ and 1.6–2.0 × 10 9 kg-CO₂-eq per year, respectively. The results indicate that the AD of SHW can substantially reduce GHG emissions of the US meat industry as well as produce bioenergy to provide energy security in the US. • Co-AD of SHW with a co-substrate can produce energy of 6.03–7.60 GJ/1000 kg-SHW. • Co-AD of SHW with sewage sludge can reduce up to 524.0 kg-CO₂-eq/1000 kg-SHW. • Methane leak and fertilizer displacement substantially impact GHG emissions of AD. • AD of SHW in the southeast US can reduce GHG emissions by 2.0 × 10⁹ kg-CO₂-eq/year.

Evaluating the level of ammonia and sulfide in the liquid phase during anaerobic digestion of slaughterhouse waste operating at mesophilic scale digester—the impact of inhibition and process performance

The performance of experimental batch-reactor loaded with slaughterhouse waste at mesophilic temperature was investigated as well as the inhibition of both ammonia and sulfide concentration in the aqueous phase. The digester was operated for 68 days by evaluating the process stability basing on controlling parameters such as pH, volatile fatty acids and alkalinity in relation to the methane produced. The maximum CH4 content of 69.6% was achieved at 0.37 VFA/Alkalinity ratio and pH of 7.51 during day 37 of anaerobic digestion. However, a sudden increase of ammonia nitrogen in the digester from day 44 to day 68 decreased the methane content about 62.15% from 65% to 24.6%. Similarly, as the amount of sulfide content decreased in the liquid phase, gaseous H2S was elevated up to 132 ppm in the 68th day. During this time, it was observed that the ratio of VFA/Alkalinity decreased to 0.16, with a very low concentration of VFA, which was 150.92 mg/L. This phenomenon indicated that all the acids produced were consumed by methanogens and ammonia inhibition was at the highest rate due to the increase of ammonia nitrogen concentration in the last days of digestion. Furthermore, among of peculiar characteristic shown by slaughterhouse waste is the ability to maintain the pH above 7 without the addition of any buffering agent throughout the AD process. Meanwhile, the evaluation of the level of both ammonia and sulfide in the aqueous phase revealed that the inhibitory effect of ammonia concentration was higher than sulfide concentration.

Anaerobic co-digestion of poultry slaughterhouse wastes with sewage sludge in batch-mode bioreactors (effect of inoculum-substrate ratio and total solids)

High amounts of organic matter and protein in slaughterhouse wastes make them a viable choice for anaerobic digestion and biogas production. The purpose of this study was to investigate potentials of biogas production from poultry slaughterhouse residues (waste and sludge) in a batch-fed anaerobic co-digestion process. In the first phase of the study, laboratory-scale experiments were conducted using 1-liter reactors at 34 °C with a retention time of 50 days in order to optimize digestion parameters; i.e. inoculum-substrate ratio (ISR) and total solids (TS). Based on these experiments, the ISR of 4 and the TS of 5% were determined as optimal settings for digestion over a retention time of 50 days. The highest biogas and methane yields in these experiments were respectively reported by 0.631 and 0.462 m3/kg-VSadded, achieved with 66% removal of volatile solids (VS). The optimized parameters obtained from the first phase were also used for verification at a larger scale (20 liters), wherein biogas and methane yields were found to be 0.574 and 0.402 m3/kg-VSadded; respectively. Moreover, results showed that optimal anaerobic digestion of slaughterhouse wastes in 20-liter digester could lead to 63% removal of VS and 88% reduction of chemical oxygen demand (COD) over a retention period of 42 days. The findings also indicated that decreasing ISR and increasing TS could bring about reduced pH as well as accumulation of fatty acids and ammonia, which could severely undermine yields of methanogenesis process.

Biomethane production potential of slaughterhouse waste in the United States

Anaerobic Digestion (AD) is a promising technology to treat slaughterhouse waste (SHW) for the bioenergy production, nutrient recovery, and pathogen reduction. Three scenarios of estimating the biomethane potential from SHW of the US and the individual States have been conducted in this study. The US meat producers discharged 18.4 million metric ton (MT) SHW in 2016, which can potentially generate 22.7 × 109 kWh of biomethane. In Texas State, up to 2.3 × 109 kWh year−1 of energy can be potentially produced from AD of SHW and up to 106.3% of natural gas currently used in the Nebraska State for electricity generation can potentially be replaced with biomethane produced from the AD of its SHW. The technical challenges using SHW as the feedstock of AD process in the US have been summarized, including nitrogen and sulfur inhibition, foaming, sterilization, digestate disposal, supply chain etc. In addition, case studies were conducted by proposing an AD plant treating SHW from a typical slaughterhouse in a U.S. State that mostly processes the broiler, swine, and bovine. In our case studies, a net energy of 17,009–85,278 kWh d−1 is estimated to be generated from such AD plant. Therefore, producing biomethane from SHW can significantly promote bioenergy production in the US, thus enhancing the quick reach of bioenergy development targets set at the Federal and State levels, while overcoming the technical and management barriers of using SHW.

Modeling of anaerobic digestion of slaughterhouse wastes after thermal treatment using ADM1

According to the European legislation, thermal treatment of category 2 slaughterhouse by-products at 140 °C, 4–5 bar for 20 min is obligatory for their hygienization prior to disposal. This process is known as “rendering”. The product of the rendering process is rich in lipids and proteins making it an appropriate feedstock for biogas plants. The mathematical modeling of biogas production from slaughterhouse wastes after the rendering process has been studied adjusting the anaerobic digestion model (ADM1). For this purpose, two mesophilic (38–39 °C) continuous stirred tank reactors (CSTRs) have been operated in parallel under a hydraulic retention time of 21.5 ± 2.14 d, while the organic load was increased from 50 to 149.6 g COD L−1. Recirculation of the mixed liquor suspended solids (MLSS) took place in one of the CSTRs, resulting in a different solids’ concentration in it. The ADM1 was calibrated by estimating key kinetic parameters, such as the maximum specific consumption rate constant and the half-saturation constants of volatile fatty acids and verified. The degradation kinetics of this type of waste seemed to be faster, as a result of its emulsification through rendering, while the coefficient yields of the acidogens were lower than the default values of ADM1. The structure of the model was proven suitable for predicting the response of both bioreactors under small or medium step transitions, but not for abrupt impulse disturbances in the organic loading rate.

Comparison of existing models to simulate anaerobic digestion of lipid-rich waste

Models for anaerobic digestion of lipid-rich waste taking inhibition into account were reviewed and, if necessary, adjusted to the ADM1 model framework in order to compare them. Experimental data from anaerobic digestion of slaughterhouse waste at an organic loading rate (OLR) ranging from 0.3 to 1.9kgVSm−3d−1 were used to compare and evaluate models. Experimental data obtained at low OLRs were accurately modeled whatever the model thereby validating the stoichiometric parameters used and influent fractionation. However, at higher OLRs, although inhibition parameters were optimized to reduce differences between experimental and simulated data, no model was able to accurately simulate accumulation of substrates and intermediates, mainly due to the wrong simulation of pH. A simulation using pH based on experimental data showed that acetogenesis and methanogenesis were the most sensitive steps to LCFA inhibition and enabled identification of the inhibition parameters of both steps.

Bioavailability of essential trace elements and their impact on anaerobic digestion of slaughterhouse waste

Slaughterhouse waste is an energy rich feedstock suitable for anaerobic digestion processes. However, chemical characterization showed a deficiency in essential trace elements which are critical for optimal performance of the process. Hence this study investigated the degree of bioavailability of trace elements in four semi-continuous lab-scale AD tests accepting slaughterhouse waste under mesophilic conditions (38°C) and a moderate organic loading rate of 2.2kg/m3d. Parameters, such as volatile fatty acid (VFA) concentration, COD removal rate and specific methane yield were compared to the results of sequential extraction analysis. The highest methane yield (250–275Nm3/t COD), lowest accumulation of VFA (<500mg/l) and high COD removal rate (75–80%) was obtained when the total concentration of 11.4mg/l Ni, 25.4mg/l Co and 4.8mg/l Mo was present in the reactor, of which 62% of Ni and Co, and 68% of Mo were bioavailable for microbial uptake. Based on these results it can be recommended that a supply of 2.5g/t Ni, 3.5g/t Co, 0.6g/t Mo and 0.05g/t Se provide optimal conditions for anaerobic digestion of slaughterhouse waste.

Influence of Inoculums/Substrate Ratios (ISRs) on the Mesophilic Anaerobic Digestion of Slaughterhouse Waste in Batch Mode: Process Stability and Biogas Production

Batch digestion experiments were conducted to determine the effects of inoculums/substrate ratio of three different ratios (ISRs) 0.3, 0.5 and 1. The substrate chosen in this study was slaughterhouse waste from Adrar city (south west of Algeria). The inoculation was made by sludge issued from wastewater treatment plant. During this study, several parameters of anaerobic digestion were measured, such as pH, VFA, AT and volume of the produced biogas. pH variation and VFA/TA values have shown high stability of anaerobic digestion process.

Study of thermal pre-treatment on anaerobic digestion of slaughterhouse waste by TGA-MS and FTIR spectroscopy

Thermogravimetric analysis coupled to mass spectrometry (TGA-MS) and Fourier-transform infrared spectroscopy (FTIR) were used to describe the effect of pasteurization as a hygienic pre-treatment of animal by-products over biogas production. Piggery and poultry meat wastes were used as substrates for assessing the anaerobic digestion under batch conditions at mesophilic range. Poultry waste was characterized by high protein and carbohydrate content, while piggery waste presented a major fraction of fat and lower carbohydrate content. Results from anaerobic digestion tests showed a lower methane yield for the pre-treated poultry sample. TGA-MS and FTIR spectroscopy allowed the qualitative identification of recalcitrant nitrogen-containing compounds in the pre-treated poultry sample, produced by Maillard reactions. In the case of piggery waste, the recalcitrant compounds were not detected and its biodegradability test reported higher methane yield and production rates. TGA-MS and FTIR spectroscopy were demonstrated to be useful tools for explaining results obtained by anaerobic biodegradability test and in describing the presence of inhibitory problems.

Continuous biomethanization of agrifood industry waste: A case study in Spain

The anaerobic digestion technology is a biological treatment widely used to reduce the pollution load of wet waste biomass. In this work we present the results obtained by performing extensive experiments of anaerobic digestion of slaughterhouse waste, tomato industry waste and olive oil industry waste in continuous mode, which were designed to demonstrate that anaerobic digestion is an effective technology from an environmental and economic point of view.Biogas yields obtained are between 35.22 and 5.45Nm3 biogas/m3 olive oil industry waste and tomato industry waste respectively and the slaughterhouse wastes achieve intermediate production, 30.86Nm3 biogas/m3 municipal slaughterhouse waste and 22.53Nm3 biogas/m3 Iberian pig slaughterhouse waste. Moreover, it possible to degrade between 63.46 and 75.3% of the initial organic matter.If these results are analyzed, the environmental, energetic economic benefits of anaerobic digestion can be quantified. Biomethanation of all these wastes generated annually in Extremadura could prevent the emission of 134,772t of equivalent carbon dioxide, generate an energy similar to that provided by 2826toe and reach payback times from 3.29 to 3.75 years for anaerobic digestion plant designed to treat the wastes generated by a medium-sized industry. So, we have fulfilled all the planned aims.

Anaerobic digestion of slaughterhouse waste: Main process limitations and microbial community interactions

Fresh pig/cattle slaughterhouse waste mixtures, with different lipid-protein ratios, were characterized and their anaerobic biodegradability assessed in batch tests. The resultant methane potentials were high (270-300 L(CH4) kg(-1)(COD)) making them interesting substrates for the anaerobic digestion process. However, when increasing substrate concentrations in consecutive batch tests, up to 15 g(COD) kg(-1), a clear inhibitory process was monitored. Despite the reported severe inhibition, related to lipid content, the system was able to recover activity and successfully degrade the substrate. Furthermore, 16SrRNA gene-based DGGE results showed an enrichment of specialized microbial populations, such as β-oxidizing/proteolitic bacteria (Syntrophomonas sp., Coprothermobacter sp. and Anaerobaculum sp.), and syntrophic methanogens (Methanosarcina sp.). Consequently, the lipid concentration of substrate and the structure of the microbial community are the main limiting factors for a successful anaerobic treatment of fresh slaughterhouse waste.

Slaughterhouse fatty waste saponification to increase biogas yield

A thermochemical pretreatment, i.e. saponification, was optimised in order to improve anaerobic biodegradation of slaughterhouse wastes such as aeroflotation grease and flesh fats from cattle carcass. Anaerobic digestion of raw wastes, as well as of wastes saponified at different temperatures (60 °C, 120 °C and 150 °C) was conducted in fed-batch reactors under mesophilic condition and the effect of different saponification temperatures on anaerobic biodegradation and on the long-chain fatty acids (LCFAs) relative composition was assessed. Even after increasing loads over a long period of time, raw fatty wastes were biodegraded slowly and the biogas potentials were lower than those of theoretical estimations. In contrast, pretreated wastes exhibited improved batch biodegradation, indicating a better initial bio-availability, particularly obvious for carcass wastes. However, LCFA relative composition was not significantly altered by the pretreatment. Consequently, the enhanced biodegradation should be attributed to an increased initial bio-availability of fatty wastes without any modification of their long chain structure which remained slowly biodegradable. Finally, saponification at 120 °C achieved best performances during anaerobic digestion of slaughterhouse wastes.

Anaerobic digestion of solid slaughterhouse waste: study of biological stabilization by Fourier Transform infrared spectroscopy and thermogravimetry combined with mass spectrometry

In this paper, Fourier Transform infrared spectroscopy (FTIR) along with thermogravimetric analysis together with mass spectrometry (TG-MS analysis) were employed to study the organic matter transformation attained under anaerobic digestion of slaughterhouse waste and to establish the stability of the digestates obtained when compared with fresh wastes. Digestate samples studied were obtained from successful digestion and failed systems treating slaughterhouse waste and the organic fraction of municipal solid wastes. The FTIR spectra and TG profiles from well stabilized products (from successful digestion systems) showed an increase in the aromaticity degree and the reduction of volatile content and aliphatic structures as stabilization proceeded. On the other hand, the FTIR spectra of non-stable reactors showed a high aliphaticity degree and fat content. When comparing differential thermogravimetry (DTG) profiles of the feed and digestate samples obtained from all successful anaerobic systems, a reduction in the intensity of the low-temperature range (approximately 300 degrees C) peak was observed, while the weight loss experienced at high-temperature (450-550 degrees C) was variable for the different systems. Compared to the original waste, the intensity of the weight loss peak in the high-temperature range decreased in the reactors with higher hydraulic retention time (HRT) whereas its intensity increased and the peak was displaced to higher temperatures for the digesters with lower HRT.

Anaerobic digestion of solid slaughterhouse waste (SHW) at laboratory scale: Influence of co-digestion with the organic fraction of municipal solid waste (OFMSW)

Mesophilic anaerobic digestion of slaughterhouse waste (SHW) and its co-digestion with the organic fraction of municipal solid waste (OFMSW) have been evaluated. These processes were carried out in a laboratory plant semi-continuously operated and two set-ups were run. The first set-up, with a hydraulic retention time (HRT) of 25 days and organic loading rate (OLR) of 1.70 kg VS m −3 day −1 for digestion, and 3.70 kg VS m −3 day −1 for co-digestion, was not successful. The second set-up was initiated with an HRT of 50 days and an OLR of 0.9 kg VS m −3 day −1 for digestion and 1.85 kg VS m −3 day −1 for co-digestion. Under these conditions, once the sludge had been acclimated to a medium with a high fat and ammonia content, it was possible to decrease the HRT while progressively increasing the OLR to the values used in the first set-up until an HRT of 25 days and OLRs of 1.70 and 3.70 kg VS m −3 day −1, for digestion and co-digestion, respectively (the same conditions of the digesters failures previously). These digesters showed a highly stable performance, volatile fatty acids (VFAs) were not detected and long chain fatty acids (LCFAs) were undetected or only trace levels were measured in the analyzed effluent. Fat removal reached values of up to 83%. Anaerobic digestion was thus found to be a suitable technology for efficiently treating lipid and protein waste.