Large-scale Biogas Plants Research Articles

Carbon reduction trade-off between pretreatment and anaerobic digestion: A field study of an industrial-scale biogas plant

With the implementation of municipal solid waste source segregation, the enormous sorted biogenic waste has become an issue that needs to be seriously considered. Anaerobic digestion, which can produce biogas and extract floating oil for biodiesel production, is the most prevalent treatment in China for waste management and greenhouse gas (GHG) emissions reduction, in accordance with Sustainable Development Goal 13 of the United Nations. Herein, a large-scale biogas plant with a capacity of 1000 tonnes of biogenic waste (400 tonnes of restaurant biogenic waste and 600 tonnes of kitchen biogenic waste) per day was investigated onsite using material flow analysis, and the parts of the biogas plant were thoroughly analyzed, especially the pretreatment system for biogenic waste impurity removal and homogenization. The results indicated that the loss of the total biodegradable organic matter was 41.8% (w/w) of daily feedstock and the loss of biogas potential was 18.8% (v/v) of daily feedstock. Life cycle assessment revealed that the 100-year GHG emissions were −61.2 kgCO2-eq per tonne biogenic waste. According to the sensitivity analysis, pretreatment efficiency, including biodegradable organic matter recovery and floating oil extraction, considerably affected carbon reduction potential. However, when the pretreatment efficiency deteriorated, GHG benefits of waste source segregation and the subsequent biogenic waste anaerobic digestion would be reduced.

Sustainability of large-scale commercial biogas plants in Nepal

Interest in large-scale compressed biogas (CBG) and biogas for electricity generation is increasing due to these technologies’ potential for addressing dual energy and waste management challenges. However, sustainable operation of large-scale commercial biogas plants requires attention to numerous factors, including technical aspects (feedstock types, plant size, operational parameters, and biogas and fertilizer utilization strategies), costs (capital investment and operational), and affordability, as affected also by subsidies. This study conducts a case study of the sustainability of an existing operational large-scale biogas plant in Nepal, considering its operational condition, financial status, and environmental benefits under designed capacity and actual operating conditions. Design parameters related to biogas and digestate production, financial viability, and greenhouse gas (GHG) emission reduction potential were compared with the realized outcomes of the plant. Operational and financial data for the plant were obtained through visits to the plant supplemented by interviews of the plant manager. The analysis reveals that both the feedstock and digester efficiencies are much lower than the design expectations, by 55% and 62%, respectively. This has led to reductions in the production of biogas and biofertilizers by 72% and 90%, respectively. Moreover, while the internal rate of return (IRR) of the plant at design capacity was 23%, it is indeterminate for the actual operating condition, as the net present value is negative for all discount rates. The biogas plant does generate environmental benefits; the GHG emissions avoided are estimated to be around 274 tons of CO2 equivalent per year under the actual operating conditions. Given these results, it is clear that improving the operational performance of large-scale biogas plants in contexts such as this one should be a priority. Moreover, the findings can help policymakers, investors, and other stakeholders make better plans for future development of biogas facilities, insisting on more realistic and careful assessments of technical and financial viability.

Pathways for the thermally optimal design and practice of anaerobic digestion in large-scale biogas plants: Heat transfer modeling and energy analysis

A flexible and configuration-dependent heat model framework is developed, validated, and used to perform in-depth energy analyses and to identify the optimal design and operating conditions in wet anaerobic digesters in stirred reactors with multi-membrane gasholders in modern biogas plants. This framework enables a detailed geometrical representation of the gasholder and digester at different scales, such that different gasholder designs from single- to multi-membrane systems with varying configurations can be studied and compared to increase thermal efficiency. The model operates in the dynamic regime and includes longwave infrared surface-to-surface heat exchanges. This includes the impact of dynamic environmental conditions (e.g., ambient air temperature, wind, rain, and solar radiation) on the thermal behavior of the unit. Throughout the parametric analyses, the influences of key operating and design parameters, as well as synergistic features such as the feasibility and efficiency of various waste heat recovery strategies, are investigated on the basis of the thermal performance of the digester. The analysis shows that, based on a 3,000-m3 double-membrane biogas plant with a raw biogas self-consumption of 7.4%, thermal autarky can be achieved using (i) a three-membrane gasholder (−2.1%), (ii) outgoing digestate heat recovery (−3.7%), and (iii) recovery of heat from biogas purification (−1.6%).

Comprehensive Analysis and Greenhouse Gas Reduction Assessment of the First Large-Scale Biogas Generation Plant in West Africa

More than 500 million people will be added to Africa’s cities by 2040, marking the largest urbanization in history. However, nonrenewable fossil energy sources are inadequate to meet Africa’s energy needs, and their overexploitation leads to intensified global warming. Fortunately, Africa has a huge potential for biomass energy, which will be an important option for combating climate change and energy shortage. In this study, we present a typical large-scale biogas plant in Burkina Faso, West Africa (Ouagadougou Biogas Plant, OUA), which is the first large-scale biogas generation plant in West Africa. The primary objective of OUA is to treat human feces, and it serves as a demonstration plant for generating electricity for feed-in tariffs. The objectives of this study are to assess the greenhouse gas reduction capacity and economic, environmental, and social benefits of OUA and to analyze the opportunities and challenges of developing biogas projects in Africa. As a result, the net economic profit of the OUA biogas plant is approximately USD 305,000 per year, with an anticipated static payback period of 14.5 years. The OUA plant has the capacity to treat 140,000 tons of human feces and 3000 tons of seasonal mixed organic waste annually, effectively reducing greenhouse gas emissions by 5232.61 tCO2eq, improving the habitat, and providing over 30 local jobs. Finally, the development of biogas projects in Africa includes advantages such as suitable natural conditions, the need for social development, and domestic and international support, as well as challenges in terms of national policies, insufficient funding, technical maintenance, and social culture.

Economic and Technological Feasibility Analysis of Biogas Production from Biomass Wastes by Adding Hydro char and Hydrothermal Pre-treatment

Anaerobic digestion is an effective method of treating animal wastes and biomass wastes, reducing pollution by them and producing regenerative energy in the form of methane (methane gas). As renewable bioenergy resources, fish processing wastes, tofu residue and lignocellulose biomass (bamboo residue and rice straw) are identified as cheap and have a wide range of sources, so they can be used as an effective substrate for biogas production. When fish processing waste with additive Hydro char (200°C and 220°C), hydrothermal pretreated tofu residue (140°C) and lignocellulose biomass (rice straw: 160°C) are subjected to anaerobic co-digestion, biogas production can be increased. In addition, when liquid fraction from hydrothermal carbonization (200°C-280°C) and fish processing wastes are mixed in a certain ratio and used as raw materials for anaerobic digestion to carry out anaerobic co-digestion, optimal output of biogas can be produced. This paper aims at the technology of producing biogas and maximizing the production by anaerobic digestion of fish processing wastes and tofu residue with Hydro char obtained from bamboo residue at a certain temperature (200°C) according to hydrothermal carbonization, and making an economic and technological analysis of production process. Through a Break-even point analysis, producing biogas using hydrothermal Pre-treatment and adding Hydro char has more advantages than the without Pre-treatment method in both production volume and investment recovery duration. It was demonstrated that the comparison and evaluation of without Pre-treatment and adding Hydro char, hydrothermal Pre-treatment approach, the investment recovery duration could be reduced from 419 days to 256 days with the large-scale biogas plants of 1 000 m3 as a criterion.

Bi-level Energy Trading Model Incorporating Large-scale Biogas Plant and Demand Response Aggregator

Increasing intermittent renewable energy sources (RESs) intensifies the imbalance between demand and generation, entailing the diversification of the deployment of electrical energy storage systems (ESSs). A large-scale biogas plant (LBP) installed with heating devices and biogas energy storage (BES) usually exhibits a storage-like characteristic of accommodating an increasing penetration level of RES in rural areas, which is addressed in this paper. By utilizing the temperature-sensitive characteristic of anaerobic digestion that enables the LBP to exhibit a storage-like characteristic, this paper proposes a bi-level energy trading model incorporating LBP and demand response aggregator (DRA) simultaneously. In this model, social welfare is maximized at the upper level while the profit of DRA is maximized at the lower level. Compared with cases only with DRA, the results show that the proposed model with the LBP improves the on-site accommodation capacity of photovoltaic (PV) generation up to 6.3%, 18.1%, and 18.9% at 30%, 40%, and 50% PV penetration levels, respectively, with a better economic performance. This nonlinear bi-level problem is finally recast by a single-level mathematical program with equilibrium constraints (MPEC) using Karush-Kuhn-Tucker (KKT) conditions and solved by the Cplex solver. The effectiveness of the proposed model is validated using a 33-bus test system and a sensitivity analysis is provided for analyzing what parameter influences the accommodation capacity most.

Toward thermal autarky for large-scale biogas plants: Dynamic energy modeling for energy efficiency in anaerobic digesters with enhanced multimembrane gasholders

Biogas production via anaerobic digestion could approach thermal autarky (less biogas self-consumption and better energy efficiency) using enhanced solutions for thermal insulation based on new multimembrane gasholder configurations, loss avoidance, and heat recovery strategies. In this study, a predictive and configuration-dependent dynamics energy model is developed to daily and seasonally assess the thermal efficiency and heating requirements of industrial biogas plants involving wet digesters with upper multimembrane gasholders. The model is validated using experimental data from a full-scale biogas plant in operation over a one-year period.The energy model involves a set of dynamic energy balances defined for each compartment of the digester and gasholder. All possible heat sources and sinks (ambient air temperature, wind, rain, and solar radiation) and heat exchanges or losses via advection, convection, and conduction, as well as a complete representation of the infrared radiative networks between the surfaces of the digester, are included for each compartment depending on the operating and design parameters. These heat exchanges are subject to fluctuating environmental conditions (e.g., ambient air temperature, wind, rain, and solar radiation).The results indicate that triple-membrane gasholders with a third insulation membrane made of a suitable material and thickness, together with the involvement of heat recovery from the digestate advective heat, are capable of reducing the overall thermal losses by more than 95 % (e.g., −51 % of the gasholder cover loss and − 81 % of the advective digestate loss) and when the waste heat from biogas purification is also valorized, the biogas plant can become thermally self-sufficient.

Importance of Feedstock in a Small-Scale Agricultural Biogas Plant

Although no legal sustainability criteria have been formulated for electricity and heat production from biogas, the sustainability and profitability of large-scale biogas plants which use mainly energy crops is now questioned. Small (farm-size) biogas plants characterized by CHP electrical output in the range between 15 kWel and 99 kWel, operating on agricultural wastes and by-products, seem more suitable; however, the variety of feedstock may be crucial in the proper design and operation of such family biogas plants. This paper aims to present the problems that occurred in small agricultural biogas plants fed with sheep manure (SM), horse manure (HM), and grass-clover silage (GCS). This paper also focuses on analyzing the energy balance and carbon dioxide (CO2) emissions related to four technological solutions (Scenarios 1–4) based on various feedstocks, grinding and feeding systems, and wet/dry fermentation. The biogas plant was originally based on dry fermentation with an organic loading rate ~10.4 kgVS·m−3·d−1, a hydraulic retention time of 16 days, and temperature of 45 °C in the fermentation chamber. The material was shredded and mixed in a mixing device, then the mixture of manures and silage was introduced to the horizontal fermentation chamber through a system of screw feeders. The biogas and the digestate were collected in a reinforced concrete tank. The biogas was sent to the CHP unit of an installed electrical power of 37 kWel, used to produce electricity and recover the heat generated in this process. Scenario 1 is based on the design assumptions used for the biogas plant construction and start-up phase. Scenario 2 includes a new feeding and grinding system, in Scenario 3 the feedstock is limited to SM and HM and wet fermentation is introduced. In Scenario 4, a dry fermentation of SM, HM, and maize silage (MS) is assumed. Avoided CO2 emissions through electricity and heat production from biogas were the highest in the case of Scenarios 1 and 4 (262,764 kg CO2·y−1 and 240,992 kg CO2·y−1) due to high biogas production, and were the lowest in Scenario 3 (7,481,977 kg CO2·y−1) because of the low specific methane yield (SMY) of SM and HM. Nevertheless, in all scenarios, except Scenario 3, CO2 emissions from feedstock preparation and biogas plant operation are much lower than that which can be avoided by replacing the fossil fuel energy for the electricity and heat produced from biogas. Our observations show that a small agricultural biogas plant can be an effective energy source, and can contribute to reducing CO2 emissions only if the appropriate technological assumptions are adopted, and the entire installation is designed correctly.

Feasibility Analysis of Biogas Production by Using GIS and Multicriteria Decision Aid Methods in the Central African Republic

Organic waste-derived biogas production is an effective way to transform biowaste into renewable energy for the electricity supply in developed and developing countries. This study analyzes the feasibility of biogas production as a solution to waste management and electricity supply in Bangui, the capital city of the Central African Republic. The selection of the biogas plant site in an urban area is a complex process due to the area availability and different factors. The GIS, combined with the MCDA, could analyze the environmental, social, and economic factors and criteria such as slope, settlement, rivers, land, urban growth, and local and major roads. Applying the ELECTRE TRI as the MCDA method enhanced the techniques to determine the suitable biogas plant site. The biowaste amount and distance from the suitable site were determined using the ArcGIS distance toolset. The biogas plant’s economic and environmental benefits, such as the electricity production capacity and CO2 reduction, were analyzed based on the population growth and the biogas production per year. The analyzed results obtain an area of 3.5 km2 for a large-scale biogas plant construction, with a potential production of 2,126,799.68 kW per year using combined heat and power and 2,303,100.23 kW by converting the thermal energy to electricity. This large-scale biogas plant could treat 20% of the organic waste per year, cover 60% of the city’s electricity demand, and reduce 946,200 kg of CO2 equivalent per year.

Small-scale biogas plants in Vietnam: How are affected by policy issues?

Both developed and developing countries are working towards creating an emission free planet. Vietnam, as one of the highest contributors to greenhouse gas emissions, has implemented several policies to curtail this phenomenon. Most of these policies are geared towards the development of renewable energy technologies such as biogas. The country’s policy on environmental protection, clean energy, climate change, and rural development has been based on small-scale biogas programs and projects. However, how are these small-scale biogas plants affected by arising policy issues? To answer this question, an intensive literature review was conducted and accompanied by a consultation with biogas experts with a focus on Vietnam. The data collected were analysed using the policy cycle analytical approach. The results showed that several policy instruments, such as the price of other conventional fuels and feed-in-tariffs, affect small-scale biogas plants. Furthermore, thousands of small-scale biogas plants have been installed due to good policies such as the Vietnam National Biogas Program. Finally, funding remains the biggest barrier to biogas policy amendments and implementation; the several biogas programs implemented over the decade could have yielded more positive impact if financial barriers like co-financing by the beneficiaries were set up more appropriately. In addition, new policies in the future will favour mid- to large-scale biogas plants rather than small-scale biogas plants. This policy implication threatens the sustainability of small-scale biogas plants; therefore, policy makers must be adroit in addressing policy issues that affect biogas production in Vietnam.

Systems analysis of digestate primary processing techniques

In this paper, we performed technology assessment and systems analysis of primary digestate processing techniques to provide a comprehensive analysis of their environmental and cost performance. We compiled more than 100 observations from large-scale biogas plants and considered digestate based on manure, crops and agro-wastes, and food waste under the geographical contexts of Sweden and Belgium. Centrifuge, screw press, and rotary drum were identified as suitable primary processing techniques. We analyzed the climate impact, energy use, and operational cost of digestate management under these scenarios: no processing, partial processing (solid–liquid separation) and full processing (solid–liquid separation followed by ammonia stripping). As expected, the suitable digestate processing varied with the context, transport was often the most critical cost factor, and emissions from storage reduced the climate savings from the use of biofertilizers. However, treating liquid fraction became a main contributor to cost and climate impact under the Belgian conditions. Consequently, the possibility for local application of liquid fraction as biofertilizer could prevent costs and impacts associated with its further treatment. The main novelty of this work is in its integrative and comprehensive approach toward the choices and impacts of primary processing of digestate. We tried to bridge many individual case studies, drew from experiences of biogas plants in different geographical contexts, assessed suitable processing techniques for different digestate types, and analyzed the environmental impacts and cost of digestate management from a life cycle perspective. We believe that such integrated approaches would help decision-making for increased sustainability of the biogas sector.

Techno-economic Analysis of Biogas Conversion to Liquid Hydrocarbon Fuels through Production of Lean-Hydrogen Syngas

Large-scale biogas plants are a viable source of CH4 and CO2 to be converted efficiently into high-value products. Specifically, production of liquid hydrocarbons can enhance the availability of green fuels while achieving significant CO2 reductions on site. In this study, the production of liquid hydrocarbons is simulated by dry reforming of biogas into lean-hydrogen syngas, further converted in CO hydrogenation and oligomerization reactors. The process was modeled by using CHEMCAD based on published experimental results with the projected feed composition. A high molar feed ratio of CO2/CH4 (>1.7) was set for the reformer to minimize steam requirement while avoiding carbon formation and reaching an optimal H2 to CO molar ratio (0.7). Two options were techno-economically evaluated based on a biogas plant with a capacity of 5000 N m3/h that produces between 13.8 and 15.7 million liters per year of blending stock for transportation fuels. The economics of the process depends mainly on the cost and availability of the biogas. The minimum selling price of the liquid fuels is $1.47/L and $1.37/L for options 1 (once-through conversion of syngas to liquid fuels) and 2 (recycle of tail gas from oligomerization reactor), respectively, and can be significantly reduced in case the biogas throughput is increased to >20 000 N m3/h. Recycling of the tail gas (option 2) yielded higher productivity, resulting in higher carbon yield (77.9% on the basis of methane) and energy efficiency (67.1%). The economic viability of the process can be improved by implementing CO2 tax or other incentives to reduce capital investment. It provides a potential route for efficient conversion of biogas into liquid hydrocarbons to meet the increased demand for renewable fuels as blending stock in the transportation sector while improving the sustainability of the plant.

Biomethane plants based on municipal solid waste and wastewater and its impact on vehicle sector in India — An Environmental-economic-resource assessment

Advantages of biomethane production from large-scale biogas plants include savings of fossil fuels, better waste handling, job creation, odor, and greenhouse gas reduction. For these reasons, the government has launched and promoted various waste-to-energy schemes to install large-scale biogas plants in India. However, methane leaks from various plant sources are problematic as they contribute to global warming and compromise the environmental benefits. This paper assessed the significance of bio-compressed natural gas (bio-CNG) from large-scale biogas plants as a transportation fuel from an environmental and economic perspective. The results show that GHGs emissions of bio-CNG along its value chain (i.e., generation to utilization) are lower than other fuel options. If harnessed correctly, municipal solid waste and wastewater energy can replace 4053.47 tonnes of India’s diesel consumption per day. However, less than 2.5% of net bio-CNG potential is utilized in the current scenario. Uncertainty and sensitivity analysis shows a 0.32 and 0.08 probability that emissions from bio-CNG are greater than diesel and petrol, respectively. Furthermore, there is an 83.15% chance that the bio-CNG business will make a profit. Also, a 0.83 correlation coefficient was found between compressed biogas (CBG) price and net present value (NPV). This study indicates the massive scope of biogas in the transportation sector. Thus, to achieve the goal, setting up large-scale biogas plants is much needed.

Performance evaluation of a solar evaporation system for liquid digestate concentration

The safe and efficient treatment and resource recovery of the large amount of liquid digestate (LD) produced by biogas plants has become an important factor limiting the development of the biogas industry. In this study, a solar evaporation system was developed based on low cost, high efficiency, and high nutrient recovery of LD concentration. The effects of different parameters, including solar radiation, LD flowrate, and daily treatment capacity, on the concentration efficiency, nutrient recovery, and thermal efficiency were investigated. Economic and enviroeconomic analyses were conducted to comprehensively assess the feasibility and environmental benefits of the system for large-scale biogas plants. The results showed that the higher the solar radiation, the higher the air temperature and its saturation vapor pressure, which led to an increase in the concentration efficiency of LD. The LD concentration efficiency can reach up to 43.33% when the average daily solar radiation was 773.08 W/m2. High solar radiation also contributed to high LD temperature, leading to an increase in the percentage of free ammonia (NH3) in the LD, which was not conducive to the recovery of ammonia nitrogen (NH3N). By increasing the LD flow rate, the heat and mass exchange between air and LD in the spray chamber was enhanced, resulting in higher concentration efficiency. The variation of LD flow rate and daily treatment capacity had little effect on nutrient recovery. The recovery of NH3N and soluble salts in the concentrated phase could be as high as 78.39% and 84.19%, respectively, when the initial pH of LD was 5, the air flow rate was 0.03 m3/s, and the LD flow rate was 6 L/min. In addition, the economic analysis indicated that the concentration cost of the system in treating a daily LD production of 100 tons was 1.08 USD/ton. The solar evaporation system can reduce CO2 emissions by 2.40 × 105 tons and earn carbon credits of 3.48 × 106 USD over its lifetime. This study provides a new direction and reference for LD concentration.

Operating Performance of Full-Scale Agricultural Biogas Plants in Germany and China: Results of a Year-Round Monitoring Program

Germany (DE) and China (CN) have different political approaches in supporting the biogas sector. Three German and three Chinese large-scale biogas plants (BGPs) were evaluated as part of a year-round monitoring program. Laboratory methods were utilized to analyze the chemical indicators. Results showed a stable anaerobic digestion process without system failures in all BGPs. The methane yield had a range of 0.23–0.35 m3CH4/kgODM for DE BGPs and 0.11–0.22 m3CH4/kgODM for CN BGPs, due to different substrates and working temperatures. Financial analyses indicated that DE BGPs are viable under their current feed-in tariffs contracts. Their financial internal rate of return (IRR) ranged between 8 and 22%. However, all CN BGPs had negative IRRs, indicating that they are financially unfeasible. Risk analyses illustrated that DE BGPs will face financial nonviability if benefits decrease by 9–33% or costs increase by 10–49%, or if a combined worse case (benefit decrease and cost increase) of 5–20% occurs. Incentives to BGP operations are particularly important in China, where the government should consider switching the construction-based subsidy to a performance-based subsidy system to motivate the operators. BGP monitoring is necessary to understand the performance, in addition to briefing policymakers in case a policy reform is needed.

Possibilities of Biogas in Urban Context

Increasing population and rapid development in the planet earth have resulted in increasing demand of energy sources. Developed countries have adopted renewable sources in their policy for a sustainable future but, developing countries like Nepal are still lagging behind. Petroleum gas is used by all the city dwellers which is imported from neighboring countries and is not sustainable for a long term. Rapid urban growth has brought solid waste management and energy demand as a great challenge. Production of energy through biogas can help in management of bio-degradable waste as well as fulfill energy demands. This paper highlights study of large-scale biogas plant in and outside Nepal and explains how they have helped in managing waste, fulfilling energy demands and made positive impact in the community. This paper also suggests on possibilities of biogas as an alternative energy in developing scenario of Nepal.

A high efficient heat exchanger with twisted geometries for biogas process with manure slurry

Heat-transfer enhancement in manure slurry is crucial for increasing the efficiency and production of biogas during anaerobic digestion in biogas plants. In this study, a novel heat exchanger with an optimal twisted geometry was developed based on the numerical screening of the twisted tubes with equilateral polygons, and experiments were conducted to validate the numerical results. It was observed that the SST k–ω model is more efficient than other turbulence models in representing the heat transfer performance of the twisted tubes, and the numerical model with a thermostatic wall can be used to reliably screen the twisted geometries. The twisted hexagonal tube has the optimal geometry, with enhancement capability of up to 1.4 times compared to that of the circular tube. The formation of high continuity regions with relatively strong heat-transfer rates along the heat-exchange wall is the main reason for the high performance during heat transfer. The external heating process was integrated in a full-scale biogas plant, and the model and algorithm were developed and validated with additional experiments to describe the overall performance of both conventional and screened optimal geometries under different conditions. It was observed that a profit equivalent to 39% of total production for a large-scale biogas plant can be achieved owing to energy conservation in external heating with the twisted hexagonal tubes.

Decentralized biomass for biogas production. Evaluation and potential assessment in Punjab (India)

Punjab state has huge potential of conversion of biomass to energy that can produce estimated 3172 MW power which is the highest among all the states in India. All the developing countries are struggling with increasing energy demand and the environmental pollution. The renewable and sustainable energy resources are the best substitute to the conventional fuels and the energy sources. India is the third largest energy consumer and the third largest greenhouse gas emitting country. In the case of the state of Punjab, which is one of the top producers of biomass in the country, the share of renewable energies is still dwarfish in spite of significant opportunities. Conversion of biogas to electricity is the standard technology and power generation is the main purpose of biogas plants in the developed countries but in India it is still used as bio-CNG. Here we aim at analyzing the development and the scope of conversion of biogas to electricity in the state of Punjab in India. Massive amount of decentralized biomass resources is available in the state and there is huge potential to use this technology due to availability of biomass from the animal waste, the agriculture and the households. This study also focuses on the economic evaluation of a large-scale biogas plant in context of Indian government framework for development to the projects along with the current scenario of renewable energy resources and the power production by the large-scale Biogas power plants. Our findings show that the biogas production provides an attractive investment opportunity in the state, especially for the large-scale farms and the decentralized animal waste. Power generation to cope up the needs of Punjab can be more practicable and an environment friendly by biogas power plants as there is abundance of an organic waste material, an appropriate infrastructure and the suitable climate.

Mechanical pretreatment of lignocellulosic biomass to improve biogas production: Comparison of results for giant reed and wheat straw

The effects of a mechanical pretreatment were determined on the methane yield of giant reed stems (Arundo Donax) and wheat straw. The feedstocks were pretreated using a two stages dry milling device, whose working capacity - up to 1,2 t h−1- can meet the requirements of medium and large-scale biogas plants. Untreated and pretreated materials were anaerobically digested in batch reactors under mesophilic conditions for 28 days. The cumulative biogas production from the pretreated giant reed stems exceeded 212 Nm3 t−1 of volatile solids, showing a 137% gain as compared to the raw material; furthermore, a significant decrease in the acid detergent fiber content was observed in the processed material. Pretreated straw reached a cumulative methane yield of 250.3 Nm3 t−1 of volatile solids, gaining a 49.1% as compared to the feedstock; no statistically significant differences were observed in physicochemical composition following pretreatment. The aforementioned gains resulted far above the known range for mechanical pretreatments. The specific electric energy requirement for pretreatment decreased from 76.5 kWh t−1 of processed giant reed stems to 66.0 kWh t−1 for straw. With reference to the use of biogas in CHP plants, the net electric energy output from pretreated materials was enhanced by about 111.7% and 38.3% as compared to the feedstocks for reed and straw, respectively. The cost for the extra electric energy produced by pretreatment was estimated at 0.034 and 0.048 € kWh−1 for giant reed and straw, respectively, resulting fully compatible with the selling price for the electric energy produced from biogas in force in Italy.

Life-cycle assessment of sewage sludge-based large-scale biogas plant

The aim of this work was to study the life-cycle assessment (LCA) and impact of a biogas plant based on the municipal sewage sludge (6000 m3 capacity biogas plant at Wastewater Treatment Plant (WWTP), Delawas, Jaipur – Rajasthan, India), analyzing the environmental effects instigated due to basic systems of biogas production and also to examine the impact of using biogas as an alternate fuel using ReCiPe and midpoint methods. The results indicatedthat the construction of plant was insignificant to the whole life cycle impacts. Biogas plant showed negative GHG emissions (−0.2385 kg CO2 eq/m3) compared to coal-based electricity plants and digestate produced could be a good option to replace chemical fertilizer. Biogas production and agricultural spreading contributed −3.059E-08 kg CFC-11 eq/m3 towards beneficial effects which may be attributed to the avoidance of electricity and artificial fertilizers. The results indicated that sewage sludge-based biogas plant showed beneficial impact on the environment.