The effect of manure-screening on the biogas yield of dairy manure was evaluated in batch digesters under mesophilic conditions (35
°C). Moreover, the study determined the biogas production potential ...of different mixtures of unscreened dairy manure and food waste and compared them with the yield from manure or food waste alone. A first-order kinetics model was developed to calculate the methane yield from different mixtures of food waste and unscreened dairy manure. The methane yields of fine and coarse fractions of screened manure and unscreened manure after 30
days were 302, 228, and 241
L/kgVS, respectively. Approximately 93%, 87%, and 90% of the biogas yields could be obtained, respectively, after 20
days of digestion. Average methane content of the biogas was 69%, 57%, and 66%, respectively. Based on mass balance calculations, separation of the coarse fraction of manure would sacrifice about 32% of the energy potential. The methane yield of the food waste was 353
L/kgVS after 30
days of digestion. Two mixtures of unscreened manure and food waste, 68/32% and 52/48%, produced methane yields of 282 and 311
L/kgVS, respectively after 30
days of digestion. After 20
days, approximately 90% and 95% of the final biogas yield could be obtained, respectively. Therefore, a hydraulic retention time (HRT) of 20
days could be recommended for a continuous digester. The average methane content was 62% and 59% for the first and second mixtures, respectively. The predicted results from the model showed that adding the food waste into a manure digester at levels up to 60% of the initial volatile solids significantly increased the methane yield for 20
days of digestion.
Assembly line balancing problems (ALBP) have plagued scholars and practitioners for decades. This paper investigates a new assembly system called flexible assembly line (FAL) derived from empirical ...observations in an air-conditioner assembly workshop. FAL can avoid the ALBP itself thanks to its structural flexibility and reconfigurability. However, field investigation highlights new challenges in the FAL - the mismatch between production (assembly) and intralogistics (material supply) leads to long waiting/idle time and workflow chaos, consequently lowers productivity and increases backorders. The production-intralogistics (PiL) processes are spatiotemporally coupled and interactional. Its complexity is much higher than considering the production or intralogistics optimization solely. And the PiL processes are further complicated by uncertain events such as new job arrivals, stochastic operational time, and equipment failures. The advent of Industry 4.0 technologies shows the tremendous potentials to revolutionize the contemporary notions of production management. Massive production data can be collected and analyzed in real-time. Nevertheless, there is little methodological research regarding utilizing real-time data to support production decisions under uncertainties. Thus, how to leverage real-time data collected in Industry 4.0 environments to support the decision-making of PiL processes for achieving a matched, coordinated, and synchronous operations management under various uncertainties, is a novel research problem. This paper develops a five-phase Graduation intelligent Manufacturing System (GiMS) to achieve PiL synchronization with flexibility and resilience. The underlying principles and rationale of GiMS are formulated as a synchronization mechanism, which includes a graph-theory based clustering for planning/scheduling and real-time decentralized ticketing for execution/control. Comprehensive numerical results validate the superiority of GiMS and the benefits of visibility and traceability in various scenarios. Moreover, the effects of uncertainties and trolley capacity are investigated in the sensitivity analysis.
•A novel production-intralogistics synchronization problem in flexible assembly lines is studied.•A 5-phase implementation framework of GiMS is developed for PiL Synchronization in FAL.•A flexible and resilient real-time decision-making mechanism under GiMS is proposed.•Numerical study has validated the superiority of the proposed GiMS and real-time data.•The effects of uncertainty level and trolley capacity are studied in the sensitivity analysis.
Timely and accurate monitoring of crops is essential for food security. Here, we examine how well solar‐induced chlorophyll fluorescence (SIF) can inform crop productivity across the United States. ...Based on tower‐level observations and process‐based modeling, we find highly linear gross primary production (GPP):SIF relationships for C4 crops, while C3 crops show some saturation of GPP at high light when SIF continues to increase. C4 crops yield higher GPP:SIF ratios (30–50%) primarily because SIF is most sensitive to the light reactions (does not account for photorespiration). Scaling to the satellite, we compare SIF from the TROPOspheric Monitoring Instrument (TROPOMI) against tower‐derived GPP and county‐level crop statistics. Temporally, TROPOMI SIF strongly agrees with GPP observations upscaled across a corn and soybean dominated cropland (R2 = 0.89). Spatially, county‐level TROPOMI SIF correlates with crop productivity (R2 = 0.72; 0.86 when accounting for planted area and C3/C4 contributions), highlighting the potential of SIF for reliable crop monitoring.
Plain Language Summary
Crop monitoring is essential for ensuring food security, but reliable, instantaneous production estimates at the global scale are lacking. The monitoring of crop production in a changing climate is of paramount importance to sustainable food security. Accurate estimates of crop production are dependent on adequately quantifying crop photosynthesis. Our paper demonstrates that solar‐induced chlorophyll fluorescence (SIF), an emission of red to far‐red light from chlorophyll is highly correlated with crop photosynthesis. We show that a new high spatial resolution satellite SIF data set is highly correlated with crop productivity in the United States, which is benchmarked by the United States Department of Agriculture county‐level crop statistics. These results will improve the understanding of crop production and carbon flux over agricultural lands, as well as provide an accurate, large‐scale, and timely monitoring method for global crop production estimates.
Key Points
The photosynthetic pathway (C3, C4) impacts the relationship between CO2 uptake and SIF, which helps to interpret satellite signals
TROPOMI SIF agrees well with the seasonality of crop gross primary production (GPP) when accounting for C3/C4 fractionation
TROPOMI SIF is highly correlated with USDA reported crop productivity at the county scale
PRICES, MARKUPS, AND TRADE REFORM De Loecker, Jan; Goldberg, Pinelopi K.; Khandelwal, Amit K. ...
Econometrica,
March 2016, Letnik:
84, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This paper examines how prices, markups, and marginal costs respond to trade liberalization. We develop a framework to estimate markups from production data with multi-product firms. This approach ...does not require assumptions on the market structure or demand curves faced by firms, nor assumptions on how firms allocate their inputs across products. We exploit quantity and price information to disentangle markups from quantity-based productivity, and then compute marginal costs by dividing observed prices by the estimated markups. We use India's trade liberalization episode to examine how firms adjust these performance measures. Not surprisingly, we find that trade liberalization lowers factory-gate prices and that output tariff declines have the expected pro-competitive effects. However, the price declines are small relative to the declines in marginal costs, which fall predominantly because of the input tariff liberalization. The reason for this incomplete cost pass-through to prices is that firms offset their reductions in marginal costs by raising markups. Our results demonstrate substantial heterogeneity and variability in markups across firms and time and suggest that producers benefited relative to consumers, at least immediately after the reforms.
To comply with the United Nations Framework Convention on Climate Change (UNFCCC) greenhouse gas (GHG) emissions reporting requirements, the Intergovernmental Panel on Climate Change (IPCC) developed ...guidelines for calculating national GHG inventories in a consistent and standard framework. Although appropriate for national level accounting purposes, IPCC methodologies lack the farm level resolution and holistic approach required for whole farm systems analysis. Thus, whole farm systems modelling is widely used for farm level analysis. A review of 31 published whole farm modelling studies of GHG emissions from beef and dairy cattle production systems indicated a number of important outcomes. For example, improvements in animal productivity (i.e., liveweight gain milk production) and fertility (i.e., lower culling, lower replacement rates) can reduce GHG emissions/kg product. Additionally, intensification of production as output/ha can reduce emissions/kg product provided input requirements of feed and/or fertilizer are not excessive. Carbon sequestration into agricultural soils has the potential to offset emissions from pastoral based production systems. A product based metric is widely used and allows a wide range of objectives, including farm profitability and food security to be met. Variation in farm system parameters, and the inherent uncertainties associated with emission factors, can have substantial implications for reported agricultural emissions and thus, uncertainty or sensitivity analysis in any modelling approach is needed. Although there is considerable variation among studies in relation to quality of farm data, boundaries assumed, emission factors applied and co-product allocation approach, we suggest that whole farm systems models are an appropriate tool to develop and measure GHG mitigation strategies for livestock farms.
This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
Various nano-enabled strategies are proposed to improve crop production and meet the growing global demands for food, feed and fuel while practising sustainable agriculture. After providing a brief ...overview of the challenges faced in the sector of crop nutrition and protection, this Review presents the possible applications of nanotechnology in this area. We also consider performance data from patents and unpublished sources so as to define the scope of what can be realistically achieved. In addition to being an industry with a narrow profit margin, agricultural businesses have inherent constraints that must be carefully considered and that include existing (or future) regulations, as well as public perception and acceptance. Directions are also identified to guide future research and establish objectives that promote the responsible and sustainable development of nanotechnology in the agri-business sector.
Crop yields are projected to decrease under future climate conditions, and recent research suggests that yields have already been impacted. However, current impacts on a diversity of crops ...subnationally and implications for food security remains unclear. Here, we constructed linear regression relationships using weather and reported crop data to assess the potential impact of observed climate change on the yields of the top ten global crops-barley, cassava, maize, oil palm, rapeseed, rice, sorghum, soybean, sugarcane and wheat at ~20,000 political units. We find that the impact of global climate change on yields of different crops from climate trends ranged from -13.4% (oil palm) to 3.5% (soybean). Our results show that impacts are mostly negative in Europe, Southern Africa and Australia but generally positive in Latin America. Impacts in Asia and Northern and Central America are mixed. This has likely led to ~1% average reduction (-3.5 X 1013 kcal/year) in consumable food calories in these ten crops. In nearly half of food insecure countries, estimated caloric availability decreased. Our results suggest that climate change has already affected global food production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Electrolysis feels the heat
Electricity infrastructure powered by sunlight and wind requires flexible storage capacity to compensate for the intermittency of these sources. In this context, Hauch
et ...al.
review progress in solid oxide electrolyzer technology to split water and/or carbon dioxide into chemical fuels. These devices, which rely on oxide conduction between cathode and anode, use nonprecious metals as catalysts and operate above 600°C, thereby benefiting from thermodynamic and kinetic efficiencies. The authors highlight recent optimizations of cell components as well as systems-level architecture.
Science
, this issue p.
eaba6118
BACKGROUND
Alleviating the worst effects of climate change requires drastic modification of our energy system: moving from fossil fuels to low-carbon energy sources. The challenge is not the amount of renewable energy available—energy potential from solar and wind exceeds global energy consumption many times over. Rather, the key to a 100% renewable energy supply lies in the integration of the growing share of intermittent sources into a power infrastructure that can meet continuous demand. The higher the share of renewables, the more flexible and interconnected the energy system (the electric grid, the gas and heat networks, etc.) needs to be. Critically, a future energy system where the supply of electricity, heat, and fuels is based solely on renewables relies heavily on technologies capable of converting electricity into chemicals and fuels suitable for heavy transport at high efficiencies. In addition, higher electrolysis efficiency and integrated fuel production can decrease the reliance on bioenergy further than conventional electrolysis can.
ADVANCES
Electrolysis is the core technology of power-to-X (PtX) solutions, where X can be hydrogen, syngas, or synthetic fuels. When electrolysis is combined with renewable electricity, the production of fuels and chemicals can be decoupled from fossil resources, paving the way for an energy system based on 100% renewable energy. Solid oxide electrolysis cell (SOEC) technology is attractive because of unrivaled conversion efficiencies—a result of favorable thermodynamics and kinetics at higher operating temperatures. SOECs can be used for direct electrochemical conversion of steam (H
2
O), carbon dioxide (CO
2
), or both into hydrogen (H
2
), carbon monoxide (CO), or syngas (H
2
+CO), respectively. SOECs can be thermally integrated with a range of chemical syntheses, enabling recycling of captured CO
2
and H
2
O into synthetic natural gas or gasoline, methanol, or ammonia, resulting in further efficiency improvements compared with low-temperature electrolysis technologies. SOEC technology has undergone tremendous development and improvements over the past 10 to 15 years. The initial electrochemical performance of state-of-the-art SOEC single cells has more than doubled, while long-term durability has been improved by a factor of ∼100. Similar improvements in performance and durability have been achieved on the stack level. Furthermore, SOEC technology is based on scalable production methods and abundant raw materials such as nickel, zirconia, and steel, not precious metals. Performance and durability improvements as well as increased scale-up efforts have led to a hundredfold gas production capacity increase within the past decade and to commissioning of the first industrially relevant SOEC plants. Over the next 2 to 3 years, plant size is expected to further increase by a factor of almost 20. In recent years, SOEC systems have been integrated with downstream synthesis processes: examples include a demonstration plant for upgrading of biogas to pipeline quality methane and the use of syngas from an SOEC plant to produce fuels for transport via the Fischer-Tropsch process.
OUTLOOK
Improved understanding of the nanoscale processes occurring in SOECs will continue to result in performance and lifetime gains on the cell, stack, and system levels, which in turn will enable even larger and more efficient SOEC plants. In Germany, the share of intermittent renewables in the electricity supply has passed 30%, while in Denmark, intermittent sources account for almost 50% of the electricity supply. As this happens for a growing number of countries, demand for efficient energy conversion technologies such as SOECs is poised to increase. The increasing scale will help bring down production costs, thereby making SOECs cost-competitive with other electrolysis technologies and, given sufficiently high CO
2
emissions taxation, cost-competitive with fossil-based methods for producing H
2
and CO. SOECs offer an opportunity to decrease the costs of future renewable energy systems through more efficient conversion and enable further integration of renewables into the energy mix.
Solid oxide electrolyzers: From nanoscale to macroscale.
The splitting of H
2
O or CO
2
occurs at solid oxide electrolysis cell (SOEC) electrodes. Multiple cells are combined into SOEC stacks, which are in turn combined into SOEC plants. When renewable electricity is used, the production of transport fuels and chemicals can be decoupled from fossil resources. SOECs operate at elevated temperatures, resulting in electrolysis efficiencies unattainable by other electrolysis technologies.
In a world powered by intermittent renewable energy, electrolyzers will play a central role in converting electrical energy into chemical energy, thereby decoupling the production of transport fuels and chemicals from today’s fossil resources and decreasing the reliance on bioenergy. Solid oxide electrolysis cells (SOECs) offer two major advantages over alternative electrolysis technologies. First, their high operating temperatures result in favorable thermodynamics and reaction kinetics, enabling unrivaled conversion efficiencies. Second, SOECs can be thermally integrated with downstream chemical syntheses, such as the production of methanol, dimethyl ether, synthetic fuels, or ammonia. SOEC technology has witnessed tremendous improvements during the past 10 to 15 years and is approaching maturity, driven by advances at the cell, stack, and system levels.
This paper contains an analysis of the hard coal production process in Poland with selected indicators such as productivity, marginal productivity and the substitution of production factors. Current ...organization of the hard coal mining process is mainly characterized by the decreasing economies of scale, the loss of the average and marginal productivity. Static model of the production function indicates a 50% decrease in the average productivity in the years 2005–2013. This indicates the incorrect use of available production factors and poses a threat to further existence of mining companies. The reduction of production costs will be inevitable in this situation. The obtained results of the analysis led to creation of two innovative strategies of: flexible and stable coal mining production.
Display omitted
•Efficiency analysis of the hard coal mining in Poland.•Analysis of production function, that allows immediate reaction to emerging changes.•Simulation involving the determination of most efficient production factor.•Creation of innovative strategies of: flexible and stable coal mining production.
•Globally, 271Mha, or 2.06% of ice-free land surface, can be characterized as urban in 2000.•In 2040, these numbers increase to 621 Mha, or 4.71% of global ice-free land.•Urban land is predominantly ...located in areas that are suitable afor crop production.•65 Mton of crop production will be displaced by urbanization between 2000 and 2040.•Impacts of urbanization on cropland differ widely between world regions.
Urban growth has received little attention in large-scale land change assessments, because the area of built-up land is relatively small on a global scale. However, this area is increasing rapidly, due to population growth, rural-to-urban migration, and wealth increases in many parts of the world. Moreover, the impacts of urban growth on other land uses further amplified by associated land uses, such as recreation and urban green. In this study we analyze urban land take in cropland areas for the years 2000 and 2040, using a land systems approach. As of the year 2000, 213Mha can be classified as urban land, which is 2.06% of the earth’s surface. However, this urban land is more than proportionally located on land that is suitable and available for crop production. In the year 2040, these figures increase to 621Mha, or 4.72% of all the earth’s surface. The increase in urban land between 2000 and 2040 is also more than proportionally located on land that is suitable and available for crop production, thus further limiting our food production capacity. The share of urban land take in cropland areas is highest in Europe, the Middle-East and Northern Africa, and China, while it is relatively low in Oceania and Sub-Saharan Africa. Between 2000 and 2040, urban growth caused the displacement of almost 65Mton of crop production, which could yield an expansion of up to 35Mha of new cropland. Land-use planning can influence both the location and the form of urbanization, and thus appears as an important measure to minimize further losses in crop production.
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