Biogas Production Research Articles

Environment, Soil, and Digestate Interaction of Maize Silage and Biogas Production

In this study are presented the possibilities of using maize silage for biogas production. An experiment with maize silage took place over three years (2016–2018) in two localities, Ilandža, Alibunar municipality (L1—Locality 1) and Dolovo (L2—Locality 2), Serbia, and using two variants: a control with no digestate (C) and a variant with digestate, which was organic manure from biogas facilities (AD). In the AD variant, 50 t ha−1 of digestate was introduced into the soil just before sowing the maize. The following traits were examined: plant height (PH), biomass yield (BMY), biogas yield (BGY), and methane yield (MY). The effects of the studied factors (year, fertilization, and locality) on the biogas yield were significant (p < 0.5). The most favorable year for biogas production was 2016 (207.95 m3 ha−1), while the highest values of maize plant height, biomass, and methane yield were recorded in 2018 (2.48 m, 51.15 t ha−1 dry matter, and 258.25 m3 ha−1). The digestate exerted a significant influence (p < 0.5) on the values of all the tested maize parameters in all three experimental years. The biomass yield was positively associated with the plant height, biogas, and methane yield (r = 0.62 *; r = 0.70 *; r = 0.81 **) and positively but nonsignificantly associated with temperature (r = 0.42) and precipitation (r = 0.12). The application of the digestate before sowing improves the anaerobic digestion of maize silage and biogas production.

Interval Analysis of Volatile Solid (VS) and Biochemical Oxygen Demand (BOD) in Batch Anaerobic Fermentation of Selected Agrowaste

This study investigated the degradation of volatile solids (VS) and biochemical oxygen demand (BOD) during the anaerobic digestion of selected agro-waste, specifically cassava peels, maize husks, pig slurry, and the composite. The objective was to evaluate the biodegradability of these feedstocks, in line with their potential for biogas production. The Research was conducted at the National Centre for Energy Research and Development (NCERD) laboratory, University of Nigeria Nsukka (UNN). Batch reactors were used to conduct experiments over a period of 45 days. The digesters were operated under controlled conditions, and samples were analyzed at three (3) different points: 24 hours, peak of gas production (day 30), and at the end of the digestion (day 45). The results demonstrated that all the substrates exhibited a reduction in VS and BOD in the course of digestion. However, the most significant reduction in VS and BOD occurred around the peak of gas production. This entails that this period is critical for microbial activity and biogas yield. Corn husks had high initial VS and BOD values of 4.73±0.22 % and 92.80±3.26 mg/L respectively. However, that did not translate to higher biogas production compared with the composite that had initial values of 4.34±0.19 % and 88.00±5.50 mg/L respectively. By the end of the digestion, an average VS reduction of 65% and a BOD reduction of 70% were observed across all substrates, indicating a substantial degradation of organic material. Biogas production was better in the composite (72.580±4.53 %), an indication that higher VS and BOD do not automatically translate to higher gas yield. Thus, factors like multiple substrate interaction affect gas yield and process efficiency.

Temperature effect of biogas production from a greenhouse biogas digester

Globally, energy challenges are increasing with population growth. Many countries solely depend on fossil fuels (oil, coal, natural gas, etc.) for energy generation for different processes. Fossil fuels fall under non-renewable energy sources, are polluters of the environment, and get depleted faster, thus making it challenging to sustain a continuous energy supply. Therefore, there is a need for alternative sources of energy to mitigate the hazards associated with the utilization of fossil fuels. The present study aims to monitor the performance of a three-meter cubic (3 m3) greenhouse biogas digester, focusing on the temperature effect in biodegrading cow dung materials for gas generation. The study was conducted under mesophilic temperature conditions, pH, and hydraulic retention time for 30 days. Results revealed that slurry temperatures of about 33.5 ℃ and ambient temperatures of about 35 ℃ resulted in a remarkable peak biogas yield of 0.3 m3 on the 23rd day of the month. After the optimum yield of the biogas, the performance declined and was ascribed to the non-supply of the new feedstock, and the environment in the reactor became acidic, hence hindering the biodegradation process. Ultimately, the total biogas yield obtained from the study was 2.58 m3, equivalent to 15.48 kWh of energy. This amount of bio-generated energy was twofold the average daily electricity consumption of middle-income South African households. It was demonstrated that temperature was a major factor influencing the performance of the assembled biogas digesters and, thus, should be closely monitored for appreciable biogas production. This study is envisaged to pave the way for the future affordable and environmentally friendly biogas production process.

Theoretical Assessment of Agro-Waste for Biogas Production Based on Novel Methodology Related to Biochemical Potential

Agricultural and waste biomasses present viable solutions for utilization in the energy sector, achieving sustainable and long-term transformation into energy and fuel. However, it is important to carefully evaluate the competing applications for these feedstocks, considering both short- and long-term stability. Biomass for biogas production in agriculture and waste management is used due to its availability and ease of handling. Considering everything mentioned, evaluating the most suitable raw materials for biogas production is crucial for meeting sustainability criteria and promoting biomass as an energy source. In this paper, an examination of different biomass sources as possible feedstock to produce biogas by applying a theoretical approach to the proximate and final analysis results of those materials is presented. Based on data from the raw material analysis, the theoretical biochemical methane potential (TBMP) for the considered samples was calculated. Furthermore, the mass and energy balance for the case study biogas plant was also performed. According to the obtained results, the considered feedstocks show the validity of their use for biogas production considering the fulfillment of the raw material minimum quantity, mandatory residue arrangement, and achieving higher efficiency of the energy conversion process.

Mathematical Modeling of Biogas Production in Sanitary Landfills

Objective: The objective of this study is to evaluate the biogas production potential in sanitary landfills using the Verhulst mathematical model, which is employed to represent natural phenomena constrained by a saturation point. Theoretical Framework: It was based on references on energy use from waste, possible conversion routes, in addition to mathematical models that estimate the energy potential for biogas generation. Method: The methodology adopted for this research involves the use of data collected in an experimental cell, subsequently applying the De Verhulst model through a regression with minimization of errors using the Least Squares Method (LSM). Results and Discussion: The results indicated that the developed model correlates well with the observed data, demonstrating its suitability as a predictive model for biogas production. Research Implications: The research contributes to the construction of a theoretical framework for the adaptation, elaboration and use of mathematical models to predict the energy potential in the generation of biogas in landfills. Originality/Value: This study contributes to the literature by using a population growth model (Verhulst) to predict landfill biogas production.

Opportunities for biogas production from algal biomass

Energy security is a critical global challenge in the transition to sustainable development. Anaerobic digestion (AD) offers a promising renewable energy solution that mitigates environmental impacts. Algae, as biomass feedstock, have shown significant potential for bioenergy production; however, their complex chemical composition poses challenges to the efficiency of the AD process. To address these limitations, various pretreatment methods have been applied to enhance biogas production. In this study, we performed a comprehensive meta‐analysis to evaluate the effects of different pretreatments on methane (CH₄) yields from both microalgae and macroalgae. Our results demonstrate that biological, physical, and combined chemical–physical pretreatments significantly improve CH₄ production in microalgae, with increases of up to 141%, 125%, and 151%, respectively. For macroalgae, physical pretreatments were the most effective, leading to a 129% increase in CH₄ yield. We also estimate that utilizing just 10% of the global algal biomass production (3.6 Mt) could generate over 5.5 TWh y−1 of energy. This potential could be doubled with the application of appropriate pretreatment strategies. These findings highlight the role of algae in advancing renewable energy production and contribute to the growing body of knowledge on optimizing AD processes for cleaner energy generation.

A life cycle assessment of cover crop ensiling and co-digestion with cattle manure

AbstractCover crops offer a potential biogas feedstock, and to enable continuous operation of the biogas plant, ensiling can be used for biomass preservation. The aim of the present study was to assess the environmental impacts of biogas production at an organic dairy farm for two modelled scenarios: (1) harvesting and ensiling of cover crops and cereal straw and co-digestion with cattle manure, or (2) mono-digestion of cattle manure and direct cover crop soil incorporation. The biogas scenarios were modelled in a consequential LCA in relation to a common baseline without anaerobic digestion, with cover crop soil incorporation and field application of raw cattle manure. Biogas scenarios resulted in decreased global warming impacts of (1) 250 and (2) 120 Mg CO2eq for a 1000-hectare example dairy farm due to substitution of natural gas. However, emissions from ensiling, biogas plant operation, and agronomic effects increased other environmental impacts. Agronomic modelling with the Daisy model showed a crop yield increase of 0.11 Mg DM ha−1 year−1 on a sandy loam soil with cover crop digestion, but also an increase in N leaching of 38% and a decrease in soil C stocks of 8.1 Mg C ha−1 over 100 years relative to the reference. Emissions of VOCs and NOx during ensiling increased ozone formation and negative impacts on human health and ecosystems, although further research is needed to better understand these emissions. In conclusion, this modelling study shows that greenhouse gas emissions can be reduced by using ensiled cover crops for co-digestion with manure when biogas is used to substitute fossil gas, although trade-offs with other environmental categories must be considered.

Adaptation of Chlorella vulgaris immobilization on rice straw with liquid manure to create a sustainable feedstock for biogas production and potential feed applications

Rice straw (RS) is a widely available agricultural residue with significant potential for biogas production and feed applications; however, its poor digestibility and nutritional value limit its utilization. This study explores an innovative approach to enhance the digestibility and nutritional value of RS by cultivating Chlorella vulgaris through immobilization technology on RS, using liquid manure (LM) as an alternative to the traditional BG11 medium. The results showed an increase in chlorophyll a (Chl a) after 12 days for both the BG11 medium and LM-based treatments, from 0.13 to 0.34 and 0.24 mg Chl a/g product (DM), respectively. Additionally, the immobilized microalgal biomass increased to 284.18 and 170.14 mg algal biomass/g product (DM), respectively. Soaking under microaerobic conditions during cultivation led to the partial degradation of RS. This, combined with the formed microalgal biofilm, contributed to an improved digestibility of the dry matter, reaching 69.1% and 65.9% for the final products based on the BG11 medium and LM mediums, respectively, compared to 52.1% for the raw RS. Furthermore, the crude protein and lipids contents were significantly improved with the potential for applications in feed, reaching 21.4% and 4.1% for the BG11 medium-based product, while they were observed to be 12.8% and 3.0%, respectively, for the LM-based product. Additionally, carbon-to-nitrogen ratio was significantly reduced compared to the raw RS. The higher digestibility and improved nutritional value contributed to increased biogas production, reaching 129.3 and 118.7 mL/g (TS) for the products based on the traditional medium and LM medium, respectively, compared to 86.7 mL/g (TS) for the raw RS. The immobilization mechanism and biofilm development could be attributed to the roughness of the RS and extracellular polymer substances. This study demonstrates that integrating C. vulgaris cultivation on RS with LM as a nutrient source not only enhances the digestibility and nutritional value of RS but also offers a sustainable waste management solution with potential applications in biogas production and animal feed.

Cobalt-modified digestate-derived biochar enhances kitchen waste anaerobic dry digestion: Performance, microbial mechanisms, and metabolic pathways

To achieve simultaneous in-situ high-value utilization of digestate and efficient resource recovery of kitchen waste (KW). In this work, Co-modified digestate-derived biochar (DDB-Co) was prepared for the first time, the effects of DDB-Co on KW mesophilic dry anaerobic digestion were investigated, and the underlying mechanisms were elucidated. The results showed that the specific surface area of DDB-Co increased to 98.7 m2/g, which was 37.4 % higher than that of the unmodified group (DDB). DDB-Co exhibited a dose-dependent effect on biogas production from the KW dry digestion, with the optimal dose of 4.0 g/L (calculated on a solid content) DDB-Co yielding 205.3 mL/(g·VS) of biogas, representing an 80.9 % increase compared to the CK group. However, higher doses, such as 8.0 g/L DDB-Co, reduced the cumulative biogas production. Mechanistic analysis indicated that 4.0 g/L DDB-Co facilitated the dissolution of particulate organic matter and accelerates the conversion process of volatile fatty acids (VFA) in KW, thereby preventing excessive acidification. Microbial community structure analysis revealed that DDB-Co reduced microbial richness and diversity but selectively enriched microorganisms such as Lactobacillus and Methanothrix, accelerating the direct interspecific electron transfer (DIET) reaction rate and increasing biogas production. Metagenomic analysis demonstrated that DDB-Co primarily upregulated the relative abundances of key enzymes in the acetate decarboxylation methanogenesis pathway, such as acetate kinase (ackA), phosphate acetyltransferase (pta), and acetyl-CoA synthetase (acs), enhancing biogas yield and maintaining system stability. The findings of this work expand the high-value utilization pathways for digestate and provide an alternative solution for the efficient resource recovery of KW.

Mono e codigestão anaeróbia de resíduos de frutas e vegetais: Efeitos no rendimento de biogás e no biofertilizante

ABSTRACT The proper disposal of fruit and vegetable waste is essential to promote environmental sustainability, reduce the carbon footprint, improve soil quality, and contribute to the transition to a circular economy. This study examined the impact of incorporating dairy cattle wastewater (DCWW) into anaerobic co-digestion with fruit and vegetable residues and utilization of the resulting biofertilizer as a diluent in the anaerobic mono-digestion of fruit and vegetable residues (recycle). The specific biogas and methane production and the agronomic quality of the biofertilizer were evaluated in a semi-continuous trial. Two startup strategies were employed: initially, the reactors were entirely fed with inoculum (biofertilizer derived from DCWW), and fruit and vegetable residue feedstock was gradually introduced. Anaerobic co-digestion of fruit and vegetable residues with DCWW yielded the highest specific production of biogas and methane at 720 and 436 L kg-1 of volatile solids (VS), respectively. The addition of DCWW increases fruit and vegetable residue alkalinity by 249% and reduces the volatile acidity by 83.4%. Anaerobic mono-digestion of fruit and vegetable residues enhances macronutrient recovery in the biofertilizer through recycle. Logistically, directing fruit and vegetable residues to rural areas for anaerobic co-digestion with DCWW promotes agricultural biofertilizer use.

Solid-state anaerobic digestion of sweet corn waste: The effect of mixing and recirculation interval

The mixing and sludge recirculation interval is one of the key successes of the solid-state anaerobic digestion process, a promising technology for converting high-solid agro-industrial wastes to renewable energy. This study employed a pilot-scale completely stirred tank reactor to examine biogas production from sweet corn waste, including corn cobs, husks, and seeds. The reactor was operated as solid-state anaerobic digestion at an ambient temperature. The mixing and recirculating intervals were set to non-mixing and mixing for 10 minutes every 3, 6, and 12 hours. The initial total solid of the feedstock was 25%, while the hydraulic retention time was 30 days. The results showed that during the mixing and recirculation every three hours, the highest chemical oxygen demand, total solid, and volatile solid (VS) removal efficiencies were 85.42%, 62.92%, and 64.59%, respectively. The ratio between volatile fatty acid and alkalinity ranged between 0.20 and 0.30 without any sign of system failure. The highest specific methane yield of 766 L/kg VSadded was obtained in the experiment with mixing and recirculating intervals every 3 hours. It was found that the modified Gompertz model could effectively fit the methane yields with an R2 of 0.9667. The modeled methane production potential and the maximum methane production rate were 867.40 NL/kg VSadded and 132.01 NL/kg VSadded-d, respectively. Additionally, the levelized cost of the biogas produced from the solid-state anaerobic digestion of the sweet corn waste was calculated to be 0.61 USD/kg. The findings of this study can serve as a guide for the design and operation of the SS-AD system, which aims to transform various types of lignocellulosic waste into environmentally friendly energy.

The effect of Fenton sludge on anaerobic digestion of papermaking wastewater in an upflow anaerobic sludge blanket reactor

An upflow anaerobic sludge blanket (UASB) reactor was used to investigate the effect of adding Fenton sludge (FS) on the anaerobic digestion of actual papermaking wastewater. The results showed that a one-time addition of 10 g/L FS could sustainably promote the performance of UASB for more than 40 days. The organic matter removal efficiency increased by 15.56%, and the biogas production increased by 24.52%. The proportion of methane in biogas increased by 12.87%. Adding FS increased the capacitance values of sludge extracellular polymeric substances and the electron transfer system activity in reactor increased by 1.76 times. The dehydrogenase activity and coenzyme F420 of the sludge increased by 1.54 and 2.11 times, respectively. Adding FS enriched the iron-reducing bacteria (Thermodesulfobacteriota) and hydrolytic acid-producing bacteria (Chloroflexota and Synergistota), thereby promoting the hydrolysis and acidification process. Adding FS was beneficial to the enrichment of methanogen, especially Methanosaeta, significantly increasing the methane production.

Performance Monitoring of Greenhouse Biogas Digester

The country of South Africa is facing an energy crisis due to heavy reliance on fossil fuels, resulting in continuous load shedding. The use of renewable energy technologies can help resolve the current electricity crisis in the country. Moreover, waste-to-energy conversion has the potential to greatly contribute to economic development and improve public health. One such technology is biomass, which exploits waste-to-energy conversion. Additionally, solar energy can be utilized to maintain appropriate digester temperatures for optimal biogas yield. The study aims to assemble a portable balloon biogas digester in an enclosed greenhouse cavity and feed it with cow dung. Daily monitoring of pH and temperature (ambient, greenhouse, and slurry) was conducted, while biogas yield was monitored using a serial residential diaphragm flow meter. Furthermore, the composition of methane was monitored using the SAZQ biogas analyzer. The study investigated the impact of temperature on biogas production. The results revealed that the gas production rate of biogas fermentation increased within a certain temperature range. Therefore, maximum biogas production was achieved at a pH of 6.84 to 7.03, and the composition of methane exceeded 50%. Consequently, the study concluded by indicating that the digester housed within a greenhouse envelope, as demonstrated in this novel study, maintains the temperature within the optimal mesophilic range necessary for anaerobic digestion.

In vitro gas production, in situ digestibility, intake, weight gain and ruminal characteristics of calves fed a diet containing 60% waste papaya silage.

Our aim was to evaluate a whole-grain diet containing 0 (T1) and 60% (T2) waste papaya silage in vitro, in situ and in vivo. In vitro, biogas, methane and dry matter degradation (DMDiv), neutral detergent fiber (NDFDiv) and crude protein (CPDiv) were determined at 72h; in situ, DM (DMDis), NDF (NDFis) and CP (CPDis) digestibility was determined at 72h; in vivo, consumption and apparent digestibility of DM (DMI and DMD) and NDF (NDFI and NDFD), daily weight gain (DWG), rumen characteristics (pH, bacterial and protozoan counts) were determined. In addition, we performed coproparasitoscopic analysis and interviews with producers. Biogas production, methane, DMDiv, CDPiv, DMDis, DMD, NDFD, pH, bacterial and protozoan counts, and parasite load of nematodes and coccidia were not different between treatments (p > 0.05). T2 showed more NDFDiv, CPDis, DMI, NDFI, DWG than T1, while T1 was higher than T2 in NDFDis (p < 0.05). The results obtained from in vitro, in situ and in vivo techniques indicate that the diet with 60% waste papaya silage (T2) showed a similar response to the control diet (T1). Therefore, waste papaya silage is a non-conventional feeding alternative for weaned calves in the Costa Chica region of the state of Guerrero, Mexico.

Integration of bioflocculation with anaerobic digestion guided by physicochemical profiling enhances valorization potential of domestic wastewater.

Domestic wastewater is a dilute, variable, and complex carbon source for bioprocessing. Despite various treatment technologies, tailored bioprocessing and profiling studies are needed to fully explore its potential. Efficient integration of bioflocculation with anaerobic digestion (AD) is evaluated as a potential platform for small molecules and biogas recovery. Bioflocculation of low strength domestic wastewater (COD ∼ 0.1 g/L) using a bioflocculant resulted in clear water and flocculated sludge, having 30-90-fold increase in Chemical Oxygen Demand (COD). Alkali pretreatment of flocculated sludge (COD ∼ 10 g/L) significantly enhanced biogas production, resulting in a methane yield of 49 %. 1H NMR and GC-MS based profiling demonstrated the desirable impact of bioflocculation and alkali treatment on small molecule abundance. This study establishes an integrated approach that combines bioflocculation, alkali pretreatment, and AD, guided by small molecule profiling, as an effective process for valorizing domestic wastewater into biogas and recoverable organic molecules.

UNLOCKING THE POTENTIAL OF BIOENERGY: A SUSTAINABLE SOLUTION FOR ENERGY SECURITY, WASTE MANAGEMENT, AND ENVIRONMENTAL CONSERVATION

The study was carried out to generate biogas from fresh cowdung. Proximate analysis on the cow-dung sample revealed moisture content to be 60.53%, Ash content 11.01%, total solids 39.47%, volatile matter 10.78%, protein content 12%, nitrogen content 1.6%, carbohydrate 5.68% and fixed carbon 17.68%. The pH and Temperature were measured daily at 2:00pm, the temperature ranged from 30OC-38OC and the pH range was 6.7 - 7.2. The gas produced was measured daily by calculating the volume with the height increased daily up to 36 days. The results showed a typical biogas production curve, consisting of lag, acceleration, maturation, and decline phases. The optimal retention time for biogas production is identified as 20-30 days, during which biogas yields are highest. The findings indicate that microorganisms require an initial adaptation period (Days 1-3) before biogas production commences, followed by a significant increase in production (Days 11-20) and a stable production rate (Days 21-30). A decline in production is observed after 30 days. This study highlights the importance of retention time in biogas production and demonstrates the need for monitoring production kinetics to optimize retention time for specific substrates and microbial communities. The results have implications for the design and operation of biogas production systems.

Enhancing Biogas Production Through the Co-Digestion of Fish Waste (FW) and Water Hyacinth (WH) Using Cow Dung as an Inoculum: Effect of FW/WH Ratio

The current investigation explores biogas production from water hyacinth (WH) and fish waste (FW) with cow dung (CD) as an inoculum source in two scenarios. In the first scenario, the optimization of mono-digestion was performed where the effect of WH/FW (substrates) with CD (inoculum) in varied ratios of 1:1, 1:2, 2:1, and 3:1 was observed to enhance the biogas production. In the second scenario, the optimization of co-digestion using both FW and WH as substrates in different ratios (1:1, 1:2, and 2:1) with a fixed amount of inoculum was studied. The experiments were conducted in 500 mL digesters in duplicate under mesophilic conditions. Under mono-digestion conditions for FW, the digester operating with FW/CD in a 1:2 ratio demonstrated the highest biogas yield of 970 ± 14.1 mL/g VS, containing 610 CH4 mL/g VS, while in WH, the WH/CD ratio of 1:1 exhibited the highest biogas yield of 925 ± 49.4 mL/g VS, with a methane content of 440 CH4 mL/g VS. The co-digestion of the WH/FW ratio (1:1) showcased the highest biogas production of 1655 ± 91.92 mL/g VS, accompanied by 890 ± 70.7 CH4 mL/g VS. This was followed by the 1:2 and 2:1 ratio, yielding 1400 ± 56.5 and 1140 ± 169.7 mL/g VS. of biogas and 775 and 585 CH4 mL/g VS, respectively. The CD and WH mixture at a 1:1 ratio demonstrated the most significant decrease in chemical oxygen demand (COD), reaching 91.68%. COD reductions over 80% in all combinations were observed in all instances. Anaerobic digestion (AD) simulations were validated using the Gompertz model, with high correlation coefficient values (R-squared) above 0.99 for all of the studied ratios, depicting a significant correlation between experimental data and model predictions. The propionic to acetic acid ratio did not cross the threshold level, indicating no inhibition of methane production. ANOVA analysis of biogas production between the co-digestion and mono-digestion of substrates showed non-significant results (p &gt; 0.310 and p &gt; 0.824, respectively), while overall digestion was significant (p &lt; 0.024), indicating efficiency variations among substrates. Paired sample t-tests revealed substantial differences between co-digestion ratios, which were also significant.

Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study

Abstract Anaerobic digestion (AD) of feedstocks yields biogas, a potentially useful new energy source. This study looked into the anaerobic co-digestion of cow dung and organic garbage to produce biogas. An anaerobic biodigester, with a volume of 20 L, was used to digest organic waste (OW) and to trace the changes that occur during the AD process. It was equipped with tools that ensure complete control of the conditions affecting anaerobic biological reactions such as temperature, pH function, and mixing speed. Therefore, an anaerobic biodigester was designed to contain such biological transformations and to improve the biogas production process from OW. Based on the present investigation, the AD of OW was improved by integrating the substrate with sewage sludge or cow manure (CM) during the digestion process to provide the basic microorganisms to complete the digestion process. Feeding into the digester was a blend of 100 kg of cow dung (CM) and OW per day, diluted 1:1 with water. A gasbag was used to capture the methane that resulted. Biogas production began on the seventh day after the substrate was fed into the digester. A performance test was carried out on the produced biogas to determine its composition. For OW–CM, the generated biogas’s methane (CH4) concentration was determined to be 60%, but the rates of decline for TS and VS were 57 and 50.6%, respectively. Anaerobic biodegradation of OW–CM experiments was observed at 37°C, a mesophilic temperature. For OW–CM, the pH value was 6.7. After being adjusted to standard circumstances, the cumulative volume of methane produced which had been recorded as 4,914 mL became 3964.5 mL.

Evaluation of Biochemical Methane Potential and Kinetics of Organic Waste Streams for Enhanced Biogas Production

Organic waste has the potential to produce methane gas as a substitute for petrol-based fuels, while reducing landfilling and possible environmental pollution. Generally, anaerobic digestion (AD) is used only in wastewater treatment plants as a tertiary stage of sewage sludge treatment, generating a fraction of the energy that such process plants require. In this study, four different wastes—food waste (FW), dairy industry waste (DIW), brewery waste (BW), and cardboard waste (CBW)—were tested for biogas production. The biochemical methane potential (BMP) of each sample was evaluated using an automatic methane potential system (AMPTS). Operating parameters such as pH, temperature, total solids, and volatile solids were measured. Experiments on the anaerobic digestion of the samples were monitored under mesophilic conditions (temperature 37 °C, retention time 30 days). Specific methane yields (SMYs), as well as the theoretical methane potential (BMPth), were used to calculate the biodegradability of the substrates, obtaining the highest biodegradability for BW at 95.1% and producing 462.3 ± 1.25 NmL CH4/g volatile solids (VS), followed by FW at an inoculum-to-substrate ratio (ISR) of 2 at 84% generating 391.3 NmLCH4/g VS. The BMP test of the dairy industry waste at an inoculum-to-substrate ratio of 1 was heavily inhibited by bacteria overloading of the easily degradable organic matter, obtaining a total methane production of 106.3 NmL CH4/g VS and a biodegradability index of 24.8%. The kinetic modeling study demonstrated that the best-fitting model was the modified Gompertz model, presenting the highest coefficient of determination (R2) values, the lowest root means square error (RMSE) values for five of the substrates, and the best specific biogas yield estimation with a percentage difference ranging from 0.3 to 3.6%.

Cheese whey generation, management and potential for biogas production in Mexico and the State of Jalisco

ABSTRACT Pollution of water bodies and process upset in treatment plants in Mexico by cheese whey discharges is a matter of concern where scant inspection and law enforcement may aggravate the situation. This study analyzes the current state of environmental regulatory compliance and the impacts of whey discharges with particular emphasis on the country’s leading dairy-producing state, Jalisco. Subsequently, cheese whey characteristics and current valorisation volume and uses are discussed in detail. From there, anaerobic digestion is presented as a key technology for cheese whey treatment mainly to comply with wastewater regulations, with recovery of biogas as bonus. From there, the volume of cheese whey discharged to the environment and potential equivalence in biogas and electricity production is calculated considering both the technologies commonly used in industrial applications and for farms and small producers. Also, the potential electricity generation and prevented atmospheric impact are calculated and framed against the current Mexican energy and emissions inventory. Finally, a review of past efforts to disseminate the use of anaerobic digesters to produce biogas from organic waste in Mexico is undertaken, followed by a discussion of the basic requirements for a strategy to sustainably manage and treat whey discharges.