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- ItemMicrowave plasma discharges for biomass pretreatment: Degradation of a sodium carboxymethyl cellulose model(New York, NY : American Inst. of Physics, 2020) Honnorat, B.; Brüser, V.; Kolb, J.F.Biogas production is an important component of an environmentally benign renewable energy strategy. However, the cost-effectiveness of biogas production from biomass is limited by the presence of polymeric structures, which are recalcitrant to digestion by bacteria. Therefore, pretreatments must often be applied prior to anaerobic fermentation to increase yields of biogas. Many physico-chemical pretreatments have a high energy demand and are generally costly. An alternative could be the ignition of a plasma directly in the biomass substrate. The reactive species that are generated by plasma-liquid interactions, such as hydroxyl radicals and hydrogen peroxides, could contribute significantly to the disintegration of cell walls and the breakage of poorly digestible polymers. With respect to economic, processing, and other potential benefits, a microwave instigated and sustained plasma was investigated. A microwave circuit transmitted 2-kW pulses into a recirculated sodium carboxymethyl cellulose solution, which mimicked the rheological properties of biomass. Each microwave pulse had a duration of 12.5 ms and caused the ignition of a discharge after a vapor bubble had formed. Microwaves were absorbed in the process with an efficiency of ∼97%. Slow-motion imaging showed the development of the discharge. The plasma discharges provoked a decrease in the viscosity, probably caused by the shortening of polymer chains of the cellulose derivative. The decrease in viscosity by itself could reduce processing costs and promotes bacterial activity in actual biomass. The results demonstrate the potential of microwave in-liquid plasma discharges for the pretreatment of biomass. © 2020 Author(s).
- ItemDevelopment and Application of Efficient Ag‐based Hydrogenation Catalysts Prepared from Rice Husk Waste(Weinheim : Wiley-VCH, 2021) Unglaube, Felix; Kreyenschulte, Carsten Robert; Mejía, EstebanThe development of strategies for the sustainable management and valorization of agricultural waste is of outmost importance. With this in mind, we report the use of rice husk (RH) as feedstock for the preparation of heterogeneous catalysts for hydrogenation reactions. The catalysts were prepared by impregnating the milled RH with a silver nitrate solution followed by carbothermal reduction. The composition and morphology of the prepared catalysts were fully assessed by IR, AAS, ICP-MS, XPS, XRD and STEM techniques. This novel bio-genic silver-based catalysts showed excellent activity and remarkable selectivity in the hydrogenation of nitro groups in both aromatic and aliphatic substrates, even in the presence of reactive functionalities like halogens, carbonyls, borate esters or nitriles. Recycling experiments showed that the catalysts can be easily recovered and reused multiple times without significant drop in performance and without requiring re-activation. © 2021 The Authors. ChemCatChem published by Wiley-VCH GmbH
- ItemThe future agricultural biogas plant in Germany: A vision(Basel : MDPI AG, 2019) Theuerl, S.; Herrmann, C.; Heiermann, M.; Grundmann, P.; Landwehr, N.; Kreidenweis, U.; Prochnow, A.After nearly two decades of subsidized and energy crop-oriented development, agricultural biogas production in Germany is standing at a crossroads. Fundamental challenges need to be met. In this article we sketch a vision of a future agricultural biogas plant that is an integral part of the circular bioeconomy and works mainly on the base of residues. It is flexible with regard to feedstocks, digester operation, microbial communities and biogas output. It is modular in design and its operation is knowledge-based, information-driven and largely automated. It will be competitive with fossil energies and other renewable energies, profitable for farmers and plant operators and favorable for the national economy. In this paper we discuss the required contribution of research to achieve these aims.
- ItemThe global economic long-term potential of modern biomass in a climate-constrained world(Bristol : IOP Publishing, 2014) Klein, David; Humpenöder, Florian; Bauer, Nico; Dietrich, Jan Philipp; Popp, Alexander; Bodirsky, Benjamin Leon; Bonsch, Markus; Lotze-Campen, HermannLow-stabilization scenarios consistent with the 2 °C target project large-scale deployment of purpose-grown lignocellulosic biomass. In case a GHG price regime integrates emissions from energy conversion and from land-use/land-use change, the strong demand for bioenergy and the pricing of terrestrial emissions are likely to coincide. We explore the global potential of purpose-grown lignocellulosic biomass and ask the question how the supply prices of biomass depend on prices for greenhouse gas (GHG) emissions from the land-use sector. Using the spatially explicit global land-use optimization model MAgPIE, we construct bioenergy supply curves for ten world regions and a global aggregate in two scenarios, with and without a GHG tax. We find that the implementation of GHG taxes is crucial for the slope of the supply function and the GHG emissions from the land-use sector. Global supply prices start at $5 GJ−1 and increase almost linearly, doubling at 150 EJ (in 2055 and 2095). The GHG tax increases bioenergy prices by $5 GJ−1 in 2055 and by $10 GJ−1 in 2095, since it effectively stops deforestation and thus excludes large amounts of high-productivity land. Prices additionally increase due to costs for N2O emissions from fertilizer use. The GHG tax decreases global land-use change emissions by one-third. However, the carbon emissions due to bioenergy production increase by more than 50% from conversion of land that is not under emission control. Average yields required to produce 240 EJ in 2095 are roughly 600 GJ ha−1 yr−1 with and without tax.
- ItemCorrecting a fundamental error in greenhouse gas accounting related to bioenergy(Amsterdam [u.a.] : Elsevier, 2012) Haberl, H.; Sprinz, D.; Bonazountas, M.; Cocco, P.; Desaubies, Y.; Henze, M.; Hertel, O.; Johnson, R.K.; Kastrup, U.; Laconte, P.; Lange, E.; Novak, P.; Paavola, J.; Reenberg, A.; van den Hove, S.; Vermeire, T.; Wadhams, P.; Searchinger, T.Many international policies encourage a switch from fossil fuels to bioenergy based on the premise that its use would not result in carbon accumulation in the atmosphere. Frequently cited bioenergy goals would at least double the present global human use of plant material, the production of which already requires the dedication of roughly 75% of vegetated lands and more than 70% of water withdrawals. However, burning biomass for energy provision increases the amount of carbon in the air just like burning coal, oil or gas if harvesting the biomass decreases the amount of carbon stored in plants and soils, or reduces carbon sequestration. Neglecting this fact results in an accounting error that could be corrected by considering that only the use of 'additional biomass' - biomass from additional plant growth or biomass that would decompose rapidly if not used for bioenergy - can reduce carbon emissions. Failure to correct this accounting flaw will likely have substantial adverse consequences. The article presents recommendations for correcting greenhouse gas accounts related to bioenergy.
- ItemBio-IGCC with CCS as a long-term mitigation option in a coupled energy-system and land-use model(Amsterdam [u.a.] : Elsevier, 2011) Klein, D.; Bauer, N.; Bodirsky, B.; Dietrich, J.P.; Popp, A.This study analyses the impact of techno-economic performance of the BIGCC process and the effect of different biomass feedstocks on the technology's long term deployment in climate change mitigation scenarios. As the BIGCC technology demands high amounts of biomass raw material it also affects the land-use sector and is dependent on conditions and constraints on the land-use side. To represent the interaction of biomass demand and supply side the global energy-economy-climate model ReMIND is linked to the global land-use model MAgPIE. The link integrates biomass demand and price as well as emission prices and land-use emissions. Results indicate that BIGCC with CCS could serve as an important mitigation option and that it could even be the main bioenergy conversion technology sharing 33% of overall mitigation in 2100. The contribution of BIGCC technology to long-term climate change mitigation is much higher if grass is used as fuel instead of wood, provided that the grass-based process is highly efficient. The capture rate has to significantly exceed 60 % otherwise the technology is not applied. The overall primary energy consumption of biomass reacts much more sensitive to price changes of the biomass than to technoeconomic performance of the BIGCC process. As biomass is mainly used with CCS technologies high amounts of carbon are captured ranging from 130 GtC to 240 GtC (cumulated from 2005-2100) in different scenarios.
- ItemGlobal scenarios of irrigation water abstractions for bioenergy production: a systematic review(Munich : EGU, 2021) Stenzel, Fabian; Gerten, Dieter; Hanasaki, NaotaMany scenarios of future climate evolution and its anthropogenic drivers include considerable amounts of bioenergy as a fuel source, as a negative emission technology, and for providing electricity. The associated freshwater abstractions for irrigation of dedicated biomass plantations might be substantial and therefore potentially increase water limitation and stress in affected regions; however, assumptions and quantities of water use provided in the literature vary strongly. This paper reviews existing global assessments of freshwater abstractions for bioenergy production and puts these estimates into the context of scenarios of other water-use sectors. We scanned the available literature and (out of 430 initial hits) found 16 publications (some of which include several bioenergy-water-use scenarios) with reported values on global irrigation water abstractions for biomass plantations, suggesting water withdrawals in the range of 128.4 to 9000 km3 yr−1, which would come on top of (or compete with) agricultural, industrial, and domestic water withdrawals. To provide an understanding of the origins of this large range, we present the diverse underlying assumptions, discuss major study differences, and calculate an inverse water-use efficiency (iwue), which facilitates comparison of the required freshwater amounts per produced biomass harvest. We conclude that due to the potentially high water demands and the tradeoffs that might go along with them, bioenergy should be an integral part of global assessments of freshwater demand and use. For interpreting and comparing reported estimates of possible future bioenergy water abstractions, full disclosure of parameters and assumptions is crucial. A minimum set should include the complete water balances of bioenergy production systems (including partitioning of blue and green water), bioenergy crop species and associated water-use efficiencies, rainfed and irrigated bioenergy plantation locations (including total area and meteorological conditions), and total biomass harvest amounts. In the future, a model intercomparison project with standardized parameters and scenarios would be helpful.
- ItemBioenergy technologies in long-run climate change mitigation: results from the EMF-33 study(Dordrecht [u.a.] : Springer Science + Business Media B.V, 2020) Daioglou, Vassilis; Rose, Steven K.; Bauer, Nico; Kitous, Alban; Muratori, Matteo; Sano, Fuminori; Fujimori, Shinichiro; Gidden, Matthew J.; Kato, Etsushi; Keramidas, Kimon; Klein, David; Leblanc, Florian; Tsutsui, Junichi; Wise, Marshal; van Vuuren, Detlef P.Bioenergy is expected to play an important role in long-run climate change mitigation strategies as highlighted by many integrated assessment model (IAM) scenarios. These scenarios, however, also show a very wide range of results, with uncertainty about bioenergy conversion technology deployment and biomass feedstock supply. To date, the underlying differences in model assumptions and parameters for the range of results have not been conveyed. Here we explore the models and results of the 33rd study of the Stanford Energy Modeling Forum to elucidate and explore bioenergy technology specifications and constraints that underlie projected bioenergy outcomes. We first develop and report consistent bioenergy technology characterizations and modeling details. We evaluate the bioenergy technology specifications through a series of analyses—comparison with the literature, model intercomparison, and an assessment of bioenergy technology projected deployments. We find that bioenergy technology coverage and characterization varies substantially across models, spanning different conversion routes, carbon capture and storage opportunities, and technology deployment constraints. Still, the range of technology specification assumptions is largely in line with bottom-up engineering estimates. We then find that variation in bioenergy deployment across models cannot be understood from technology costs alone. Important additional determinants include biomass feedstock costs, the availability and costs of alternative mitigation options in and across end-uses, the availability of carbon dioxide removal possibilities, the speed with which large scale changes in the makeup of energy conversion facilities and integration can take place, and the relative demand for different energy services. © 2020, The Author(s).
- ItemBiomass residues as twenty-first century bioenergy feedstock—a comparison of eight integrated assessment models(Dordrecht [u.a.] : Springer Science + Business Media B.V, 2019) Hanssen, Steef V.; Daioglou, Vassilis; Steinmann, Zoran J.N.; Frank, Stefan; Popp, Alexander; Brunelle, Thierry; Lauri, Pekka; Hasegawa, Tomoko; Huijbregts, Mark A.J.; Van Vuuren, Detlef P.In the twenty-first century, modern bioenergy could become one of the largest sources of energy, partially replacing fossil fuels and contributing to climate change mitigation. Agricultural and forestry biomass residues form an inexpensive bioenergy feedstock with low greenhouse gas (GHG) emissions, if harvested sustainably. We analysed quantities of biomass residues supplied for energy and their sensitivities in harmonised bioenergy demand scenarios across eight integrated assessment models (IAMs) and compared them with literature-estimated residue availability. IAM results vary substantially, at both global and regional scales, but suggest that residues could meet 7–50% of bioenergy demand towards 2050, and 2–30% towards 2100, in a scenario with 300 EJ/year of exogenous bioenergy demand towards 2100. When considering mean literature-estimated availability, residues could provide around 55 EJ/year by 2050. Inter-model differences primarily arise from model structure, assumptions, and the representation of agriculture and forestry. Despite these differences, drivers of residues supplied and underlying cost dynamics are largely similar across models. Higher bioenergy demand or biomass prices increase the quantity of residues supplied for energy, though their effects level off as residues become depleted. GHG emission pricing and land protection can increase the costs of using land for lignocellulosic bioenergy crop cultivation, which increases residue use at the expense of lignocellulosic bioenergy crops. In most IAMs and scenarios, supplied residues in 2050 are within literature-estimated residue availability, but outliers and sustainability concerns warrant further exploration. We conclude that residues can cost-competitively play an important role in the twenty-first century bioenergy supply, though uncertainties remain concerning (regional) forestry and agricultural production and resulting residue supply potentials. © 2019, The Author(s).
- ItemN2O emissions from the global agricultural nitrogen cycle – current state and future scenarios(München : European Geopyhsical Union, 2012) Bodirsky, B.L.; Popp, A.; Weindl, I.; Dietrich, J.P.; Rolinski, S.; Scheiffele, L.; Schmitz, C.; Lotze-Campen, H.Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atmospheric pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle. For our analysis, we combine a material flow model with a land-use optimization model. In a first step we estimate the state of the Nr cycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines. Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7–9 in 2045 and 5–12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required.