Biomethane Potential Tests Research Articles

Influence of Molasses Residue on Treatment of Cow Manure in an Anaerobic Filter with Perforated Weed Membrane and a Conventional Reactor: Variations of Organic Loading and a Machine Learning Application.

This study highlighted the influence of molasses residue (MR) on the anaerobic treatment of cow manure (CM) at various organic loading and mixing ratios of these two substrates. Further investigation was conducted on a model-fitting comparison between a kinetic study and an artificial neural network (ANN) using biomethane potential (BMP) test data. A continuous stirred tank reactor (CSTR) and an anaerobic filter with a perforated membrane (AF) were fed with similar substrate at the organic loading rates of (OLR) 1 to OLR 7 g/L/day. Following the inhibition signs at OLR 7 (50:50 mixing ratio), 30:70 and 70:30 ratios were applied. Both the CSTR and the AF with the co-digestion substrate (CM + MR) successfully enhanced the performance, where the CSTR resulted in higher biogas production (29 L/d), SMP (1.24 LCH4/gVSadded), and VS removal (>80%) at the optimum OLR 5 g/L/day. Likewise, the AF showed an increment of 69% for biogas production at OLR 4 g/L/day. The modified Gompertz (MG), logistic (LG), and first order (FO) were the applied kinetic models. Meanwhile, two sets of ANN models were developed, using feedforward back propagation. The FO model provided the best fit with Root Mean Square Error (RMSE) (57.204) and correlation coefficient (R2) 0.94035. Moreover, implementing the ANN algorithms resulted in 0.164 and 0.97164 for RMSE and R2, respectively. This reveals that the ANN model exhibited higher predictive accuracy, and was proven as a more robust system to control the performance and to function as a precursor in commercial applications as compared to the kinetic models. The highest projection electrical energy produced from the on-farm scale (OFS) for the AF and the CSTR was 101 kWh and 425 kWh, respectively. This investigation indicates the high potential of MR as the most suitable co-substrate in CM treatment for the enhancement of energy production and the betterment of waste management in a large-scale application.

Effect of Mechanical Solids Separators on Potential Reduction of Methane Emissions From Dairy Manure Storage

Highlights Four mechanical manure separators were evaluated in on-farm studies. Mass balances and biochemical methane potential tests were conducted to measure on-farm separation efficiencies. Separator performance depended on environmental, material, and design factors. Over 70% solids separation and methane emission reduction potentials were achieved. Abstract. The separation efficiencies of four mechanical solid-liquid separation technologies and their effect on the reduction of methane production potential from dairy lagoons were studied using on-farm separator measurements and laboratory biomethane potential tests. The studied technologies included 1-stage sloped dual-screen, 2-stage sloped dual-screen, 1-stage horizontal scraped screen, and 1-stage sloped single-screen separators. The technologies were evaluated across various seasons on four dairies in California. On-farm sampling and measurements of the influent of flushed manure and the mass of the solids separated, as well as in-laboratory measurements of methane (CH4) production potential, were carried out. A mass balance approach was employed to determine the removal efficiencies of total and volatile solids (TS and VS) and nutrients, as well as methane emission reduction potential. The performance of the separators depended on manure characteristics, system design (e.g., screen size and orientation), separator operation and management (e.g., manure flow rate), and manure processing pit type and configuration. Among the four studied separator systems, the 2-stage sloped dual-screen separator showed the highest average TS and VS removal efficiencies, and methane emission potential reduction of 52.5%, 59.7%, and 55.8%, respectively. The 1-stage horizontal scraped screen separator had the lowest TS and VS removal efficiencies, and methane emission reduction potential of 6.3%, 9.3%, and 4.9%, respectively. The results have potential implications for nutrient and greenhouse gas management strategies and/or policies in agriculture. Keywords: Greenhouse gas, Lagoon, Manure management, Separation efficiency, Settling basin, Solid-liquid separation, Sustainable agriculture.

Biomethane potential test applied to psychrophilic conditions: Three issues about inoculum temperature adaptation

This study aimed to give lights for establishing a psychrophilic BMP test by three approaches for inoculum acclimation under 25 °C. The first test was run using stabilized mesophilic (25 °C) and psychrophilic (15 °C) inoculums to digest cellulose. Second was based on temperature acclimatization of inoculum just by time, from 30 to 10 and 20 °C. The third was running a consecutive BMP under psychrophilic temperatures (23 °C). Cellulose psychrophilic BMP using stabilized psychrophilic inoculum achieve similar results to those obtained at mesophilic conditions with stabilized mesophilic inoculum. Time acclimatization of inoculum improve BMP results respect non-adapted (from 0.47 to 055 Nm3 CH4 kg−1 SV at 20 °C, from 0.31 to 0.44 Nm3 CH4 kg−1 SV at 10 °C). Consecutive BMP under psychrophilic conditions shows better results for inoculum acclimatization to run assays at low temperatures. There is a need to develop and standardize a procedure to run psychrophilic BMP.

Comprehensive analysis of BSY as a biomass for potential energy resource recovery

Beer is one of the most consumed beverages in the globe reaching an average consumption of 23L per person per year. This makes brewing industry one of the leading economic contributors to most countries. Large amount of organic waste that pollute the environment are produced in beer making processes. The brewing by-products may reach 3%–30% of the volume of beer produced. The management and disposal of the by-products represent a significant cost for the brewery industry and a great concern for a sustainable brewery operation. There is need to resolve the waste management and environmental issues associated with this process using innovative, symbiosis and circular economy approach. Bio-circular models increase the need for resource conservation and waste beneficiation. This study explored the use of brewery spent yeast for energy production under anaerobic digestion and to evaluate its suitability as biomass for energy resource recovery with the potential to shift the brewery sector from the linear to the circular economy practice. Waste quantification, characterisation, and waste to energy conversion through biomethane potential test with AMPTS 11 set-up were investigated. It was observed that the brewery spent yeast had good proximate and ultimate results with the optimum biomethane yield obtained at 304,75 Nml. It was established that the brewery spent yeast offered a high prospect as a biomass and for the future energy mix with potential to contribution to sustainable circular economy business model.

Exploring the Possibility to Shorten the Duration and Reduce the Number of Replicates in Biomethane Potential Tests (BMP)

Biochemical methane potential (BMP) tests are the most reliable method for the direct evaluation of the methane yield from a specific feedstock in anaerobic digestion. However, these tests are time-consuming (about 1 month) and quite expensive (need of no less than two or three replicates). This study evaluates the accuracy of the “first-order kinetic”, “logistic” and “Gompertz” models in predicting the BMP values, calibrating the models’ parameters with the data collected in shorter BMP tests (i.e., 5, 7, 10, 14 and 21 days) than usually (28 days or more). Moreover, the influence of the number of replicates (i.e., two or three) on the model prediction accuracy was also evaluated. A database from 32 BMP tests, previously carried out on different substrates, was adopted for these evaluations. The test duration significantly influences the prediction accuracy for two models (Gompertz and first-order kinetic), while the number of replicates is less influencing. The ultimate methane production is not accurate if the models use parameters from short (less than 10 days) BMP tests. The increase in test duration to 21 days gives BMP predictions with errors below 10% for Gompertz and logistic models.Graphical

Biopolymers Produced by Treating Waste Brewer’s Yeast with Active Sludge Bacteria: The Qualitative Analysis and Evaluation of the Potential for 3D Printing

Biopolymers are a suitable alternative for the ongoing problem of plastic accumulation, even though commercialization is difficult, which is reflected in the price of the product. However, costs can be reduced if active sludge bacteria and cheap, accessible substrates such as waste brewer’s yeast are used. Waste brewer’s yeast is a rich source of carbon and nitrogen and is widespread as a substrate in various industries. Thus, the cultivation of active sludge bacteria was performed on waste brewers’ yeast to obtain biopolymers that can be used in 3D printing. FT-IR, TG, and DSC analyses of produced polymers were conducted after extraction, as well as biogas and biomethane potential tests. Results of cultivation under various conditions show that biopolymer content is extremely heterogeneous. However, during cultivation in SBR, signals at 1741.3, 1709.6, 1634.3, and 1238 cm−1 were detected. Further analyses are needed, but when said results are compared to those of consulted scientific articles, there is an indication that at least a small amount of PHA is present in biomass produced in SBR. Biopolymers produced in SBR were used as a material for the 3D printing of a cube. Moreover, testing of the physical properties (Young’s modulus) of a 3D-printed cube was performed. After conducting experiments, it can be concluded that said process, although time-consuming, achieved the goal of printing a stable and rigid 3D-printed cube made from biopolymers. Further optimization of said process should focus on more detailed microbial selection as well as biopolymer extraction. In that way, isolation, purification, and identification techniques will be improved, which could achieve higher biopolymer yield and, thus, make biopolymers more accessible in various industries.

From laboratory to farm-scale psychrophilic anaerobic co-digestion of cheese whey and cattle manure

This paper aims to prove the feasibility of cheese whey (CW) and cattle manure (CM) anaerobic co-digestion, from biomethane potential (BMP) laboratory assays to monitoring a farm-scale digester under psychrophilic conditions, and the impact on surrounding communities. The results show that while CW mono-digestion at 15 °C suffers inhibition, the CW:CM blend (70:30 volatile solids -VS- basis) is favorable at a similar temperature generating 0.24 m3 CH4/kg VS (35 °C yield: 0.60 m3 CH4/kg VS). A farm-scale digester (8 m3) installed in a rural school operated at 17.7 °C reached 0.42 m3CH4/kg VS, 0.31 m3 CH4/m3digester d with an organic loading rate of 0.61 kg VS/m3digester d (CW:DM 54:46). Even with CW's high volatile fatty acids (VFA) load, the digester did not show metabolic activities inhibition: VFA consumption was around 96.45 ± 2.25 %. In the rural school, biogas generation replaced the wood utilization and reduced propane consumption by 33 %. Despite these results, there are issues around psychrophilic BMP test to be reviewed, and user's misperceptions of biogas technology to overcome.

Methane Production Potential from Apple Pomace, Cabbage Leaves, Pumpkin Residue and Walnut Husks

Circular economy aims to eliminate organic waste through its transformation, composting and processing into other products or energy. The main aim of the study was to determine the specific methane yield (SMY) of anaerobic digestion (AD) of four different fruit and vegetable residues (FVR). In addition, the reduction in greenhouse gas (GHG) emissions was calculated based on the assumption that maize will be replaced by the FVR as a feedstock for biogas production. The SMY of four residues (apple pomace, cabbage leaves, pumpkin peels and fibrous strands and walnut husks) was measured in the biomethane potential test (BMP) in wet anaerobic digestion technology. The highest SMY (297.81 ± 0.65 NL kgVS−1) was observed for cabbage leaves while the lowest SMY (131.07 ± 1.30 kgVS−1) was found for walnut husks. The concentrations of two inhibitory gasses (NH3 and H2S) in biogas were low and did not affect the AD process. Only biogas produced from cabbage leaves was characterised by higher NH3 and H2S concentrations resulting from the highest protein concentration in this waste. FVR used as feedstock in biogas production may decrease the area of maize cultivation. Therefore, the GHG emissions from maize cultivation will be reduced. In Poland only, the use of four studied FVR as feedstock for biogas production would contribute to the reduction of GHG emissions by 43,682 t CO2 eq.

Effects of trace elements on digester performance and microbial community response in anaerobic digestion systems

ABSTRACT Trace elements (TE), as micronutrients for microorganisms, have a significant impact on the stability of anaerobic digestion (AD). Studies have been conducted on process stability and performance of the AD of food waste (FW) by supplementing TEs. In this study, mesophilic batch biomethane potential (BMP) tests using FW were conducted to investigate the effect of TEs (Fe, Ni, Co, Se, and Mo) as single and mixed ions. In view of their scarcity, correlations between the microbial community and digester performance such as first-order hydrolysis coefficient (Kh), volatile fatty acids (VFA), methane yield, and methane production rate (MPR) have been developed. Ni2+ at 1 and 1.5 mg/L increased the methane yield by 27% and 23% respectively. Similarly, Co2+ at 0.1 and 0.5 mg/L increased the yield by 21% and 23% respectively, compared to control. Although Se4+ at all concentrations enhanced the methane yield, Fe2+ at only 50 mg/L increased methane yield by 22%. For mixed TEs, the combination of Ni2+ [1 mg/L] +Co2+ was the best and increased methane for all Co2+ concentrations (0.1, 0.4 and 0.5 mg/L) by 16%, 14% and 12% respectively. Firmicutes and Methanosaeta were the most abundant phyla among hydrolytic and methanogenic microbial groups, respectively, constituting 42%-61% and 60-80% of their respective microbial groups. The most significant positive correlations were observed between aceto/acidogenic microorganisms and final VFA concentrations with Pearson correlation factors of 0.91.

Artificial neural network modeling of biochar enhanced anaerobic sewage sludge digestion

Despite the considerable amount of data generated with respect to biochar application in the anaerobic digestion of sewage sludge, there is a research gap for correlations linking biochar physico-chemical parameters to anaerobic digestion performance. In the current study, cumulative methane production (CMP) from anaerobic digestion of sewage sludge amended with biochar is modeled by an Artificial Neural Network (ANN) (2 hidden layers, 12 neurons each) based on data compiled from 51 published biomethane potential tests (BMP). The model reflects the effects of 13 operational parameters covering physico-chemical properties of biochar, sludge characterization and operating conditions. Various types of sewage sludge and biochar under both mesophilic and thermophilic conditions have been successfully modeled with an R2 of 0.9924. An importance analysis is conducted to evaluate the significance of the model input parameters to CMP. Results indicate that operating conditions are more significant to CMP and that CMP is strongly correlated with biochar physical properties and chemical composition where chemical composition has the dominant effect. Overall, this study proves that biochar physico-chemical parameters are correlated to CMP and enables its forecasting under unexamined conditions thus assisting in process optimization, scale up and techno-economic analyses without resorting to BMP tests.

Anaerobic co-digestion of paper sludge: Feasibility of additional methane generation in mechanical–biological treatment plants

In this work, the feasibility of the anaerobic digestion of paper sludge as a co-substrate in anaerobic digestion mechanical–biological treatment (MBT) plants is investigated. In the first phase, the biochemical properties, biomethane potential (BMP), and pollutant contents of 20 different industrial paper sludges are determined. Following the general evaluation in the BMP tests, the second phase of the project involves the semi-continuous co-digestion of six paper sludges in continuous stirred reactors (CSTR). Paper sludges are categorized according to their origin within the pulp and paper mills: Deinking Sludge (DS), Primary Sludge (PS) and Biological Sludge (BS). The analysis of potentially inhibiting elements shows that the concentrations of chlororganic compounds, mineral oil and some heavy metals are highest in DS, while the mean heavy metal loads in all paper sludges are relatively low compared to other industrial sludges. Large differences in total solids (TS) and volatile solids (VS) contents are observed among the different paper sludges investigated, with DS having the highest TS due to the high inorganic contents. The BMP of the investigated sludges ranges from 90 to 355 NL CH4 kg−1 VS. In subsequent semi-continuous co-digestion experiments simulating MBT conditions, three DS and two fiber sludges (a mixture of PS and BS) show good methane generation rates, while one fiber sludge causes inhibition and indicates an increase in viscosity. In general, co-digestion of paper sludge in anaerobic digestion MBT plants can be a viable option for energy production and also facilitates a safe disposal of the paper sludge digestates.

Performance Monitoring of Anaerobic Digestion at Various Organic Loading Rates of Commercial Malaysian Food Waste.

Application of anaerobic digestion (AD) has become common in treating palm oil mill effluent in Malaysia; however, employing AD in treating the organic fraction of municipal solid waste (OFMSW), especially food waste, is still scarce. This study aims to characterize the commercial Malaysian food waste (CMFW) and determine its potential as sustainable bioenergy feedstock through biogas production. The sample was digested via the biomethane potential (BMP) test with the variation of organic loading rates (OLRs), ranging from 0.38 to 3.83 gCOD/L. day, under mesophilic conditions. The digestion process was further evaluated in continuous operation using a 6-L continuous stirred-tank reactor (CSTR). The kinetic properties of the process were also determined. It was found that the CMFW had a significant amount of chemical oxygen demand of 230 g/L and an acidic pH of 4.5 with the carbon to nitrogen (C/N) ratio at 121:1. A maximum methane composition of 81% was obtained at 1.92 gCOD/L in the BMP test with specific methane production (SMP) at 0.952 L. CH4/L.COD fed. The biogas production was well-fitted with the modified Gompertz model with R 2 at 0.9983 and the maximum biogas potential production rate at Rm 0.1573 L/day, whereas in the CSTR operation, a maximum methane composition of 85% was produced at OLR 6 gCOD/L. day with the SMP of 1.13 L. CH4/L.COD fed. The CSTR system was in high stability as the pH was maintained in a range of 6.6–6.7, with an alkalinity ratio of 0.28. This study indicates the CMFW is a sustainable feedstock for biogas production in Malaysia. Toward a circular economy approach, the authorities shall introduce commercial scale CMFW AD as part of managing municipal solid waste issues in Malaysia.

Calcium peroxide pre-treatment improved the anaerobic digestion of primary sludge and its co-digestion with waste activated sludge

Primary sludge (PS) and Waste activated sludge (WAS) as two main sludge streams in wastewater treatment plants are commonly anaerobically co-digested, which though may be differently affected by pretreatment. Previous work has found that calcium peroxide (CaO2) pretreatment effectively enhanced anaerobic digestion of WAS. However, the feasibilities of this strategy on PS anaerobic digestion and co-digestion of WAS and PS are still unclear. Herein, this work provided new insights into these systems. Biomethane potential test demonstrated that CaO2 pretreatment at 0.02–0.26 g/g-volatile suspended solids (VSS) promoted anaerobic digestion of PS. Then the feasibility of CaO2 pretreatment for improving anaerobic co-digestion of PS and WAS mixture was confirmed, with the highest improvement in methane production, VSS destruction and sludge reduction being approximately 37.4%, 38.9% and 19.9%, achieved at 0.14 g/g-VSS of CaO2. Process modelling analysis revealed that CaO2 pretreatment increased both degradable faction and actually degraded fraction in sludge mixture. The changes of sludge characteristics via pretreatment and key enzyme activity in sludge anaerobic co-digestion system demonstrated that increased CaO2 concentration resulted in increased soluble organics release from sludge mixture in the pretreatment stage and inhibited activity of coenzyme F420 responsible for methanogenesis. Further mechanism investigation disclosed that OH−, O2− and OH were main contribution factors, and the order of their contributions were OH− >O2− >OH. This work laid the theoretical foundation and provided guidance for the practical application of CaO2 pre-treatment technology.

Factors That Affect Methane Yield Using Raw Olive Alperujo (Unhydrolyzed) as Substrate in BMP Assays

The olive alperujo (OA) corresponds to the solid waste generated in the olive oil extraction process using the two-phase centrifugation method. OA is produced in large quantities (800 kg OA/ton olives processed) and is characterized by its high moisture content, organic matter, and low pH. In Chile, the olive oil industry is recent, and one of its main challenges is to be able to manage OA to reduce the impact caused by its disposal. In this sense, its valorization as biogas by means of anaerobic digestion is an economically attractive option. For this, it is previously necessary to evaluate the biomethane potential (BMP) of the raw OA using batch assays. This study was focused on evaluating the factors that most affect the methane yield (MY) when using OA as substrate in BMP tests. First, a sweep analysis (Plackett–Burman) was applied to determine those factors that, according to the literature, would have an influence on the BMP tests. Among the factors studied, the most significant were preincubation, OA concentration, and agitation level. Subsequently, a 23 factorial experimental design was applied to evaluate the effect of these factors on MY at different levels. Results show that the OA concentration was the most significant factor affecting MY.

Increasing biogas and methane yield by adding sewage sludge and zero‐valent iron nanoparticles during the single‐stage anaerobic digestion with municipal solid waste

One of the most important problems of the anaerobic digestion (AD) process and the main obstacle to this complex structural conversion is lignocellulose and the difficulty of its biological conversion. One way to disrupt the lignocellulosic composition is using nanoparticles (NPs) with proper concentration. In this study, biomethane potential tests have been used to maximize the biomethane production from anaerobic co-digestion of municipal solid waste (MSW) and sewage sludge (SS) under different mixing ratios (MSW:SS: 100:0, 50:50, 60:40, 80:20 and 90:10) and different concentrations of iron (Fe) NPs (50, 70, 90 and 110 ppm) to speed up the AD process of the substrate, which increases biomethane production. Increasing the SS ratio up to 40% dramatically increased the biomethane yield, in a way that after 18 days of hydraulic retention time, 90% of methane (270 NmL/g VS) was obtained. The results showed that the highest biomethane yield (based on the optimal mixing ratio obtained in the first experiment, MSW:SS: 60:40) was obtained by adding 90 ppm Fe NPs using the statistical analysis (Duncan test) compared to the control (P < 0.05). Also, using iron NPs (Fe NPs) led to an increase in cellulose by 83%, a decrease in lignin by 62% and a decrease in hemicellulose by 32%, indicating an increase in the degradability due to the presence of NPs. Most of the biomethane was produced at 90 ppm Fe NPs concentration, showing an increase of 44% compared to control, and the maximum reduction in total solids and volatile solids were 36% and 28%, observed in this reactor, compared to the control sample.

Co-Processing Lignocellulosic Biomass and Sewage Digestate by Hydrothermal Carbonisation: Influence of Blending on Product Quality

Hydrothermal carbonisation (HTC) can be integrated with anaerobic digestion (AD) for the treatment of digestate, resulting in a solid hydrochar or bio-coal and a process water, which can be recirculated back into AD to produce biogas. The properties of digestate-derived hydrochars do not lend themselves to producing high quality bio-coal and blending with lignocellulosic feedstocks can improve its properties. This study investigates the co-processing of sewage sludge (SS) digestate with three lignocellulosic biomass (grass, privet hedge, and woodchip). The calorific value of the resulting bio-coal is increased following co-processing, although feedstock interactions result in non-additive behaviour. The largest increase in calorific value was observed for co-processing with woodchip. There is evidence for non-additive partitioning of metals during co-processing resulting in only moderate improvements in ash chemistry during combustion. Co-processing also effects the composition of process waters, influencing the potential for biogas production. Experimental biomethane potential (BMP) tests indicate that grass clippings are the most suitable co-feedstock for maintaining both calorific value and biogas production. However, above 200 °C, BMP yields appear to decrease, suggesting the process water may become more inhibitory. Co-processing with wood waste and privet hedge produce the higher CV bio-coal but significantly reduced BMP.

Integration of complete elemental mass-balanced stoichiometry and aqueous-phase chemistry for bioprocess modelling of liquid and solid waste treatment systems − Part 3: Measuring the organics composition

Bioprocesses transform the components of the material entering single or multiple reactor systems from one kind to another without a change in total material exiting the system(s) in the solid, aqueous or gas phases. Provided that the correct measurements are made that can quantify the material content of the bioprocess products (outputs), the material content of the bioprocess reactants (inputs) can be determined from the bioprocess products via stoichiometry. Based on this principle of mass conservation, the augmented biomethane (AugBMP) and biosulphide (AugBSP) potential test procedures are proposed, which change the BMP from a stand-alone test to a bio-reactor on which a range of additional tests are made to determine the composition of biodegradable organics. The AugBSP, which is based on biological sulphate reduction, can replace the inaccurate gas measurements in the BMP with the more accurate aqueous sulphate and sulphide measurements. The suitability of these two procedures is evaluated from a theoretical and modelling perspective. The analytical tests required to determine the composition of influent organics, expressed as CxHyOzNaPbSc, are identified. Examples of the calculation procedure from the test results are given. It is concluded that the augmented BMP (AugBMP) and BSP (AugBSP) test procedures, supplemented by anaerobic digestion dynamic modelling, are as accurate as the analytical measurements for determining the composition of biodegradable organics, and also allow the hydrolysis rate of the biodegradable organics and the unbiodegradable fraction of the organics to be determined. Knowing these characteristics of organics fed to anaerobic digesters is important to predict the anaerobic digester performance and stability.

Biomethane Potential Test Applied to Psychrophilic Conditions: Three Issues About Inoculum Temperature Adaptation

Biomethane Potential Test Applied to Psychrophilic Conditions: Three Issues About Inoculum Temperature Adaptation

Renewable energy potential of anaerobic mono- and co-digestion of chicken manure, goat manure, potato peels and maize pap in South Africa

The energy sector is an essential part of a country’s economy – it drives innovation and advances in industrialisation. Coal is the primary source of energy in South Africa. Coal contributes 95% of energy production; coal-fired power also contributes to greenhouse gas emissions, and is thus a hazard to human health and the environment. This calls for an energy mix that is renewable, sustainable, and affordable and that is carbon neutral (climate action). We investigated the potential of anaerobic mono-and co-digestion of goat manure, chicken manure, potato peels, maize pap, and cow manure inoculum for mesophilic recovery of renewable energy using the biomethane potential test. The substrates were characterised through proximate and ultimate analyses to determine the composition preferable for mono- and co-digestion. The key considerations in the determination of both the yield and production rate of methane from digestion of biomass are the substrate composition and characterisation. A high percentage of volatile solids favoured optimum biomethane production as highly volatile components provide microbes with balanced nutrients that enhance metabolic processes to produce biomethane. The mono-digestion process produced lower biomethane than did co-digestion. Higher production of biomethane by co-digestion was due to the balance of the micronutrients and macronutrients that favoured microbial metabolism and regulation of pH. Significance: The results highlight the need for appropriate techniques in combining energy and waste management. Biogas could provide solutions for some of South Africa’s energy necessities, particularly in rural areas that have abundant biogas.

Bio-Methane Potential (BMP) of Cassava Pulp Waste and Effect of Alkaline Pre-Treatment

Cassava starch processing industry produces cassava pulp as a by-product or waste. In the well-known Duong Lieu village, this waste is released in surrounding environment without treatment causing serious environmental problems. The study aimed to (1) determine the Biomethane Potential (BMP) of the waste and to (2) find out if alkaline pre-treatment would improve it. Different cassava pulp samples were going through BMP test: untreated sample; pre-treated samples at different NaOH doses of 2, 6, 8 wt.% (dry weight-based) and pre-treated samples at different NaHCO3 doses of 2, 4, 6, 8 wt.% (dry weight based). BMP assays were conducted in 590mL bottles at 37oC for 40 days. As the result, BMP of the untreated waste was 281 NmLCH4/gVS and alkaline pretreatment increased BMP of the waste up to 479 mLCH4/gVS by treatment with NaOH 6 wt.% and 450 mLCH4/gVS by treatment with NaHCO3 6 wt.%. In addition, there was a significant reduction of lignin content of the substrate after alkaline pre-treatment. The results show that cassava pulp waste has moderate potential for biogas recovery. In addition, alkaline pre-treatment by either NaOH or NaHCO3 would significantly improve its BMP, possibly thanks to the reduction of lignin content.