Biogas Feedstock Research Articles

SUSTAINABLE DEVELOPMENT OF BIOGAS MARKET IN THE EUROPEAN UNION

Biogas is an alternative renewable energy source in Europe. The feedstock (biomass) for biogas can be waste from various industries. There are two methods of biogas generation that allow processing of organic waste into an accessible energy resource: thermal and chemical. This article also discusses the environmental aspects of using biogas as a safe source for the environment. From an economic point of view, the large-scale implementation of the biogas industry was achieved by highly developed countries, such as Germany and the United Kingdom. Unfortunately, this technology is not available in all countries. The direction of biogas production is considered very promising and over time a significant increase in biogas plants is expected.

Impact of Harvest Date and Cutting Length of Grass Ley and Whole-Crop Cereals on Methane Yield and Economic Viability as Feedstock for Biogas Vehicle Fuel Production

Grass ley and whole-crop cereals used for biogas production are often finely chopped for subsequent ensiling and anaerobic digestion. Chopping can impact not only ensiling stability, digestibility and risk of process hick-ups in the digester but also harvesting capacity and fuel consumption. Based on field experiment data, the aim of this study was to investigate how three different nominal cutting lengths in the range of 3.5 mm to 12.5 mm impact methane yield and economic viability of grass ley and whole-crop cereals used as biogas substrate. A shorter cutting length affected the specific methane potential differently for the different crops, + 14 to − 25%. In biogas vehicle fuel production, balancing the additional energy and economic costs for shorter cutting length required an increased methane potential of less than 1% and 3%, respectively. As long as a decrease in cutting length increased the methane potential, the energy balance and economic result improved, despite higher energy inputs. However, mechanisms behind the impact on methane potential deserve further attention. In conclusion, we have shown that it is economically viable to produce methane gas, as a vehicle fuel, from several agricultural crops grown in the south of Sweden, i.e. grass ley and whole-crop rye and wheat, when they are harvested/chopped with a forager, ensiled as biogas feedstocks and processed to methane gas in a large-scale biogas plant.

Comprehensive characterization of microalgal isolates and lipid-extracted biomass as zero-waste bioenergy feedstock: An integrated bioremediation and biorefinery approach

The present study investigated the feasibility of domestic sewage wastewater (DSW) as an alternate to fresh-water microalgae growth media towards high-value bioenergy feedstock production. Eight native microalgal strains were screened from DSW and the effect of raw DSW (RDSW), and autoclaved DSW (ADSW) on growth and bioremediation potential were evaluated and compared with control BG11 medium. The study confirmed RDSW as a potential growth medium while Monoraphidium sp. KMC4 showed superior biomass (1.47 ± 0.08 g L−1) and lipid yield (436.01 ± 0.06 mg L−1). The corresponding values for bioremediation of ammonia, nitrate, phosphate, as well as COD remained within 88–100%. CHNS, biochemical, TGA, FTIR, FAME analysis of KMC4 confirmed it’s potential as bioenergy feedstock. Additionally, a comprehensive characterization of lipid-extracted microalgae biomass (LEMB) was carried out which suggested that LEMB can be used as a growth promoter as well as feedstock for biogas, bioethanol, and bio-oil production.

Biochemical methane potential (BMP) of six perennial energy crops cultivated at three different locations in W-Germany

To mitigate the effects of climate change, the emission of greenhouse gases (GHG) should be reduced. In the near future, an increased use of biomass for energy production will be prescribed by law in the European Union (EU) to achieve the target of emission reduction. One possibility to use biomass energetically is its transformation into biogas. The most widely grown crop for this purpose is maize. Although, the increased use of maize as biogas feedstock, due to generous subsidies, is linked to several ecological and (socio)economic problems. The most important are soil erosion, depletion and compaction, high demand and subsequent leaching of fertilizers/biocides, heavy workload, and competition for land between food and energy production. In contrast, the use of second-generation perennial energy crops (PECs) as biogas feedstock can be an auspicious approach to improve the environmental footprint of biomass production. Therefore, we evaluated and compared the biochemical methane potential (BMP) of five different perennial species (cup plant, virginia mallow, tall wheatgrass, giant knotweed, reed canary grass) and a wild plant mix (composite of 25 in parts perennial plants) on three different sites in West-Germany. In terms of methane production per area, tall wheatgrass and reed canary grass exceeded the productivity of maize under favorable conditions. Hence, we recommend both species as biogas feedstock for Central Europe or comparable climates. Additionally, other species might be suitable for biomethanation from an overall perspective, to enhance (agro)biodiversity in rural areas.

Comparing the Biomass Yield and Biogas Potential of Phragmites australis with Miscanthus x giganteus and Panicum virgatum Grown in Canada

The production of bioenergy from plant biomass has the potential to reduce fossil fuel use. The number of biogas facilities around the world has risen dramatically, increasing demand for feedstocks. In this study the invasive perennial grass Phragmites australis was evaluated as a biogas feedstock in comparison with Miscanthus x giganteus and Panicum virgatum. Results from three field sites for each species demonstrated that biomass yields for P. australis averaged approximately 1.82 ± 0.9 kg dry matter (DM) m−2, comparable to that of M. x giganteus. Yield of P. australis was greater than P. virgatum, which ranged from 0.49 ± 0.06 to 0.69 ± 0.07 kg DM m−2 in July and October, respectively. In mesophilic bench-top digester experiments, methane yields were greater for July-harvested material than for October, ranging from 172.4 ± 15.3 to 229.8 ± 15.2 L CH4 kg−1 volatile solids (VS) for all perennial grasses. Methane yields per hectare were highest for October-harvested M. x giganteus, followed by July-harvested M. x giganteus and P. australis, whereas methane yield from P. virgatum at both harvest times was lower than the other two species. These results suggest that P. australis is not an economically viable biogas feedstock without pre-treatment to improve methane yield.

Effect of chemical pretreatment using sulfuric acid on biogas production from water hyacinth and kinetics

Abstract The effect of chemical pretreatment on biogas production from water hyacinth (WH) was investigated. In pretreatment process, H2SO4 concentration was varied to be 0, 1, 2, 3, 4, 5 %v/v and residence time was varied to be 0, 30, 45, 60, 75, 90 min. Effluents of pretreatment were used as biogas feedstock. The results showed that pretreatment changed not only the cellulose content but also the glucose, COD (Chemical Oxygen Demand) and COD/N (COD/Nitrogen) ratio. Cellulose degradation occurred to follow first-order reaction based on the power law model. The best pretreatment condition was H2SO4 concentration of 5%v/v with residence time of 60 min because the slurry pretreated at that condition contained COD/N of 388.2. Anaerobic digestion of the slurry produced the biggest total biogas (424.30 mL) with the highest methane content (64.38%). The pretreatment increased total biogas 131.45% compared to without pretreatment. The measured total biogas for 90 days was fitted by using modified Gompertz, Cone, First Order model in which they resulted fitting error of 0.271–9.789%, 0.032–8.743%, 3.491–5.681% respectively. In prediction using Ratkowsky and Phenomenogical model, the slurry containing optimum COD/N of 393 (total biogas 434.64 mL) was obtained with pretreatment of H2SO4 5%v/v for 65 min.

Application of Biogas Production Technology from Various Feedstocks on Small-Medium-Micro Enterprises: A Case Study

<p>Biogas production process is an alternative method to reduce dependency on non-renewable fossil-based energy consumption and also can reduce greenhouse gases production both domestically and industrially. The existing biogas technology is suitable to be adapted in small-micro-medium enterprises and domestics, specifically for those who raise cattle. The case study was performed by observation of biogas production with various wastes as feed, namely cow dung, quail manure, and wastewater of tofu production. The study conducted via direct interviews with stake holders and visitations to the instalations. Based on our observation, biogas production from cow dung exhibits the shortest retention time compared to the others, aside from the value of C/N ratio of the biogas feedstocks. The presence of biogas production installations are significantly reducing the energy supplies among the users. Beside as biogas product, the instalations also produce solid and liquid fertilizers as by-products and have relatively high economic value. Socio – engineering problems based on the application of biodigester are also studied.</p>

Biogas production from food waste via anaerobic digestion with wood chips

In many countries, the uncontrolled generation of large amounts of food waste has resulted in severe environmental issues. Among various treatment methods that have been proposed, anaerobic digestion to produce biogas from food waste is a proven and environmentally friendly route for simultaneous food waste treatment and energy recovery. In this study, we suggest an effective methane fermentation of food waste by mixing wood chips with feedstock to minimize the sludge generation in the process. The food waste generated in an apartment complex in the Republic of Korea was used as biogas feedstock. The use of wood chips in the process increased the production of methane and hydrogen. At the food waste to wood chip ratio of 0.5, 20 ml g−1 of methane and 13.9 ml g−1 of hydrogen were produced for 15 days at 35°C. The results of this study suggest the successful application of wood chips to the anaerobic digestion of food waste for producing biogas.

Methanol Synthesis: a Distributed Production Concept Based on Biogas Plants

Today biogas produced from anaerobic digestion is used mainly for thermic and electric energy production. Its use as raw material for syngas production and further upgrading to chemical products like methanol (MeOH), dimethyl ether (DME) or acetic acid could be an interesting option as process intensification. In this work the sustainability of a Biogas-to-MeOH (BtoMeOH) or Biogas-to-DME (BtoDME) process was studied. The biogas feedstock of the Combined Heat, Power and Chemicals (CHPC) is equivalent to the production of 1 MWe in a Combined Heat and Power Plant (CHP). Biogas is converted using a reformer into syngas to produce methanol. The plant was designed considering mild conditions for chemical production and the energy necessary to reactors was generated using a fraction of the inlet biogas. This process was studied using the Simulation Suite PRO/II® by Schneider-Electric Simulation Science. The reformer and the methanol reactorproductivity were evaluated with the experimental data obtained through bench scale plants. An economicanalysis was performed to assess the sustainability of these new processes, capital and operative costs of the plants were evaluated using the Guthrie’s method. The Biogas-to-MeOH process can produce up to 297 kg h-1 of methanol with recycle. The biogas necessary to supply the energy demand of the plant is 192 kg h-1, a third of the inlet feedstock. For the Biogas-to-DME process the energy demand is similar while the DME production is 173 kg h-1. The preliminary economic evaluation shows that the main item for the capital costs are reactors and compressors and the breakeven point of both processes is 3 years. Despite the lower productivity, DME process is more convenient due to a higher market value.

Intercropping forage sorghum with maize is a promising alternative to maize silage for biogas production

Abstract Maize (Zea mays L.) silage is the preferred feedstock choice for biogas production. However, other feedstocks or mixed feedstocks might have lower environmental impact than silage maize. The objectives of this study included: 1) to determine if forage sorghum [Sorghum bicolor (L.) Moench] and forage sorghum-maize intercropping can be a viable option to replace maize in forage and biogas production, and 2) to assess the environmental impact of systems involving maize and forage sorghum intercropping and comparing the impact of those, with conventional monocrop rotations. Replicated experiments were conducted in Carrington, Fargo, and Prosper, ND, in 2013 and in Fargo, ND in 2014. Maize for silage and grain and two forage sorghum cultivars (Brown Mid Rib (BMR) and non-BMR) were grown in monoculture and in intercropping. Treatments were a total of twelve; four monocultures, four inter-row intercropped maize-sorghum, and four within-row intercropped maize-sorghum. Results across environments indicated non-BMR forage sorghum monocultures produced similar or higher biomass yield compared with maize monocultures and maize-forage sorghum mixed cultures (inter-row and within-row). Biogas yield and forage quality produced by forage sorghum monocultures, and mixtures containing forage sorghum were similar to that of maize. Thus, forage sorghum can replace, at least in part, silage maize as feedstock for feed or biogas. Forage sorghum and forage sorghum-maize intercropping had lower environmental impact compared with maize in all categories evaluated. In conclusion, intercropping of forage sorghum with maize is a promising alternative to maize silage for forage or as feedstock for biogas production.

Biogas production and changes in soil carbon input - A regional analysis

The inclusion of biogas production into the agricultural system has modified crop management and as a result the soil organic carbon (SOC) cycle of the agricultural landscape. To evaluate the effects for the German federal state of Saxony this study determines: (1) the share of agricultural land required for biogas production, (2) the change in regional carbon input fluxes to soil during the time of the establishment of the biogas production considering also the quality of sources of different fresh organic matter (FOM) for the formation of SOC and (3) the differences in carbon input to SOC between the area influenced by biogas production (here “biogas fingerprint area” (BFA)) and the surrounding arable land.Based on the location of biogas plants the region was subdivided into biomass providing units (BPUs) where a part of the arable land was considered as affected by biogas production (BFA). We hypothesized that each biogas plant uses a specific substrate mix according to its capacity. The carbon fluxes for each BPU were estimated for the years 2000 (without biogas plants) and 2011 (with biogas plants). For the year 2011, the analysis included the area demand for production of biogas feedstock and digestate recycling.On average 17.6% of the BPU agricultural land was required to supply the biogas plants and dispose of their digestate. Per kilowatt installed electrical capacity this equates to 2.0 ha, including inter alia 0.4 ha for energy crops. Highest area requirements have been observed for biogas plants with <500 kW installed capacity. Between 2000 and 2011 the total carbon flux into soil increased by 2.1%. When considering the quality of different FOM sources the gain in carbon input was 2.8%. The BFAs showed higher carbon input to soil than the surrounding agricultural land due to high contributions from digestate and crop residues (esp. agricultural grass). This compensated the low carbon input from crop by-products (e.g. straw).

Characterisation of Arabica Coffee Pulp - Hay from Kintamani - Bali as Prospective Biogas Feedstocks

The huge amount of coffee pulp waste is an environmental problem. Anaerobic fermentation is one of the alternative solutions. However, availability of coffee pulp does not appear for year-round, whereas biogas needs continuous feedstocks for digester stability. This research uses coffee pulp from Arabica Coffee Factory at Mengani, Kintamani, Bali–Indonesia. The coffee pulp was transformed into coffee pulp-hay product by sun drying for preservations to extend the raw materials through the year. Characterization of coffee pulp-hay was conducted after to keep for 15 mo for review the prospect as biogas feedstocks. Several parameters were analyzed such as C/N ratio, volatile solids, carbohydrate, protein, fat, lignocellulose content, macro-micro nutrients, and density. The review results indicated that coffee pulp-hay is prospective raw material for biogas feedstock. This well-proven preservation technology was able to fulfill the continuous supply. Furthermore, some problems were found in the recent preliminary experiment related to the density and fungi growth in the conventional laboratory digester. Further investigation was needed to implement the coffee pulp – hay as biogas feedstocks.

Simultaneous biogas purification and CO2 capture by vacuum swing adsorption using zeolite NaUSY

In this study we report on a vacuum swing adsorption process and adsorbent which allows simultaneous production of high purity methane and high purity carbon dioxide from a biogas feedstock. This is a departure from conventional biogas purification processes which focus on production of high purity methane while venting the lower purity methane/carbon dioxide stream. Using NaUSY as the adsorbent, and based on experimental and simulation data, we are able to produce product purities of 98% CH4 and 95% CO2 in the two product streams, respectively, for an energy consumption of 0.23 GJ/tCO2 from a feed containing 50/50% CH4/CO2.

Effect of biogas digestate, animal manure and mineral fertilizer application on nitrogen flows in biogas feedstock production

Abstract The expansion of biogas feedstock cultivation may affect a number of ecosystem processes and ecosystem services, and temporal and spatial dimensions of its environmental impact are subject to a critical debate. However, there are hardly any comprehensive studies available on the impact of biogas feedstock production on the different components of nitrogen (N) balance. The objectives of the current study were (i) to investigate the short-term effects of crop substrate cultivation on the N flows in terms of a N balance and its components (N fertilization, N deposition, N leaching, NH3 emission, N2O emission, N recovery in harvested product) for different cropping systems, N fertilizer types and a wide range of N rate, and (ii) to quantify the N footprint of feedstock production in terms of potential N loss per unit of methane produced. In 2007/08 and 2008/09, two field experiments were conducted at two sites in Northern Germany differing in soil quality, where continuous maize (R1), maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), and maize–grain wheat followed by mustard as a catch crop (R3) were grown on Site 1 (sandy loam), and R1 and a perennial ryegrass ley (R4) at Site 2 (sandy soil rich in organic matter). Crops were supplied with varying amounts of N (0–360 kg N ha−1, ryegrass: 0–480 kg N ha−1) supplied as biogas digestate, cattle slurry, pig slurry or calcium-ammonium nitrate (CAN). Mineral-N fertilization of maize-based rotations resulted in negative N balances at N input for maximum yield (Nopt), with R2 having slightly less negative balances than R1 and R3. In contrast, N balances were close to zero for cattle slurry or digestate treatments. Thus, trade-offs between substrate feedstock production and changes of soil organic matter stocks have to be taken into consideration when evaluating biogas production systems. Nitrogen losses were generally dominated by N leaching, whereas for the organically fertilized perennial ryegrass ley the ammonia emission accounted for the largest proportion. Nitrogen balance of the ryegrass ley at Nopt was close to zero (CAN) or highly positive (cattle slurry, digestate). Nitrogen footprint (NFP) was applied as an eco-efficiency measure of N-loss potential (difference of N input and N recovery) related to the unit methane produced. NFP ranged between −11 and +6 kg N per 1000 m3 methane at Nopt for maize-based rotations, without a significant impact of cropping system or N fertilizer type. However, for perennial ryegrass ley, NFP increased up to 65 kg N per 1000 m3. The loose relation between NFP and observed N losses suggests only limited suitability for NFP.

Cultivating Ciona intestinalis to counteract marine eutrophication: Environmental assessment of a marine biomass based bioenergy and biofertilizer production system

Abstract Eutrophication in the North and Baltic Seas is a major problem to the marine environment and the communities depending on it. To counteract this, the Swedish Marine and Water Authority suggested financial support for measures that increase the uptake of nutrients from the water by e.g. marine organisms and support for the utilisation of these organisms as value added products. In Sweden the use of biogas to replace fossil transportation fuels is widely adopted. The domestic biogas production corresponded to approx. 1.95 TWh (approx. 7010 TJ) in 2015 of which approx. 63% were upgraded for use as e.g. transportation fuel. Other uses are heat and electricity generation as well as industrial applications. To expand production, the biogas industry is searching for new substrates. In this paper the utilisation of the marine evertebrate organism Ciona intestinalis (tunicata), cultivated in the North Sea and used as feedstock for biogas and biofertilizer production is suggested and assessed. The greenhouse gas (GHG) emissions performance of the concept and it's consequences on marine eutrophication are investigated applying life cycle assessment. Results show that at full scale biogas production from C. intestinalis reduces GHG emissions by more than 65% compared to fossil transportation fuels. In addition, the results show that accounting for the system consequences of other products and services such as biofertilizer replacing mineral fertilizers and decreased marine eutrophication largely increase the environmental benefits provided by the concept. Approx. 3.7 g-Neq/MJbiogas of nitrogen are removed from the marine environment during the cultivation of C. intestinalis.

Miscanthus as biogas feedstock: influence of harvest time and stand age on the biochemical methane potential (BMP) of two different growing seasons

The use of perennial crops instead of maize as feedstock in biogas plants can be associated with multiple environmental and economic benefits. One promising species in this domain is the C4-grass Miscanthus × giganteus. The use of its biomass can mitigate carbon dioxide emissions by substitution of fossil fuels, sequestration of carbon in soils and reduced fertilizing. We compared Miscanthus from two different old fields (established 1995 and 2008) at three different harvest dates over 2 years. While the harvest in spring, like usual for combustion purposes, led to relatively low methane yields per hectare, the harvest in autumn, when the biomass is still green, exceeded the average methane yields per hectare of maize. The comparison of different old Miscanthus fields showed that there is no significant difference in terms of biomass yield, specific BMP and BMP per hectare. Only the influence of repeated autumn harvest showed differences in the methane production per hectare between both stand ages. The methane yield of the younger stand did not change considerable, while in the older stand, the productivity decreased about 15% after 1 year.

Assessment of grassland as biogas feedstock in terms of production costs and greenhouse gas emissions in exemplary federal states of Germany

Grassland production systems offer feedstock for power production based on biogas in Germany. In the future, additional potential grassland will be made available due to further concentration of cattle production in areas that possess comparative advantages for milk and meat production. This study assesses grassland as a feedstock for biogas production in Germany from both an economic and ecological point of view by considering regional production conditions and plant-specific factors. Regional production costs and greenhouse gas emissions for grasslands are calculated within the federal states of Bavaria, Lower Saxony and Schleswig-Holstein, which represent hotspots for German biogas production. A linear model approach is used to optimize the feedstock mix of each biogas plant located in one of these exemplary regions. In a scenario-based analysis, the opportunity costs for energy crops cultivated on arable land are considered to depict a shortage of arable land as an economic advantage of grasslands. Similar to EU biofuel production, the linear model considers the greenhouse gas mitigation potential for power production based on biogas and differing costs of CO2 emission rights. Greenhouse gas emissions are calculated both with and without iLUC factors to highlight the differences between arable land and grasslands with respect to limited availabilities and the consequences of greenhouse gas emissions. The results show that grasslands could be a reasonable feedstock for biogas production, especially in the northern part of Germany, if iLUC factors are considered and if a greenhouse gas mitigation potential is required that includes high prices for CO2 emission rights.

Assessment of feedstocks for biogas production, part II—Results for strategic decision making

Biogas is a biofuel that can contribute to more renewable and local energy systems. From a feedstock perspective there is a great biogas potential in Sweden, but many biogas producers face challenges and are struggling with profitability. Among the many influencing factors, the choice of feedstocks (biomass) for producing biogas and biofertilizer is of strategic importance. Within the Biogas Research Center (BRC) research project has been ongoing for four years, involving researchers, biogas and biofertilizer producers, agricultural organizations and others. The main aim has been to develop a method to assess the suitability of feedstock for biogas and biofertilizer production, and to apply this method on a few selected feedstocks of different character. This project is presented in two companion articles, of which this is the second. While the first article is focused on the developed multi-criteria method, this article present assessment results for ley crops, straw, farmed blue mussels and food waste. These results clarify how the method can be applied and highlight barriers, drivers and opportunities for each feedstock. Comparisons are also made. The results indicate that biogas production from food waste and ley crops is the most straightforward, and for straw and farmed blue mussels there are more obstacles to overcome. For all of them, the dynamic and very uncertain policy landscape is a barrier. In the final section, some conclusions about the method and its application are drawn, combining the information form both articles (part I & II).

Assessment of feedstocks for biogas production, part I—A multi-criteria approach

Expansion of biogas production is dependent on the availability of suitable feedstocks (biomass). What feedstock is suitable is a question that can be tackled from many different perspectives—it is a multi-dimensional problem. Therefore, a multi-criteria method has been developed that can be used to assess the suitability of feedstock for biogas and biofertilizer production. The method covers aspects of resource efficiency and feasibility, and the potential to supply renewable energy and recycle nutrients, operationalized via 16 indicators directed towards cost efficiency, technological feasibility, energy and environmental performance, accessibility, competition, policy and other issues. Thus it is relatively comprehensive method, yet simple enough to be used by practitioners. The main ambition, applying the method, has been to collect and structure relevant information to facilitate strategic overviews, communication and informed decision making. This is relevant for development within the biogas and biofertilizer industry, to define and prioritize among essential research projects, regarding policy, etc. This article, the first of two associated articles, is focused on the method itself. For illustration, the method is applied to assess the suitability of producing biogas from “stickleback”, which is a non-edible fish in the Baltic Sea region. In the companion article (Part II), four other feedstocks are assessed in detail, namely ley crops, straw, farmed blue mussels, and source-sorted food waste.

An economic comparison of dedicated crops vs agricultural residues as feedstock for biogas of vehicle fuel quality

The vast majority of the biofuels presently used in the EU are so called first generation biofuels produced from crops. Concerns of food security, displacement of food crop production and indirect land use change (iLUC) has led to the introduction of measures to reduce the use of first generations biofuels and promote so called advanced biofuels based on feedstock that does not compete with food/feed crops, such as waste and agricultural residues. In Sweden, 60% of the biofuel consumption is already based on waste/residual feedstock, and a unique feature of the Swedish biofuel supply is the relatively large use of biogas for transport, representing 9% of the current use of biofuels. The use of waste/residues dominates the biogas production, but agricultural residues, representing a large domestic feedstock potential, are barely used at present. This could indicate that biofuels from such feedstock is non-competitive compared both to fossil fuels and to biofuels produced from crops and waste under existing policy framework. This study show that without subsidies, the production cost of biogas as biofuel from all non-food feedstocks investigated (grass, crop residues and manure) is higher than from food crops. A shift from food crops to residues, as desired according to EU directives, would thus require additional policy instruments favoring advanced biofuel feedstock. Investment or production subsidies must however be substantial in order for biogas from residues to be competitive with biogas from crops.