• Authors:
    • Schauer, R. L.
    • Griffing, E. M.
    • Rice, C. W.
  • Source: Journal of Environmental Quality
  • Volume: 43
  • Issue: 2
  • Year: 2014
  • Summary: Life cycle assessment is the predominant method to compare energy and environmental impacts of agricultural production systems. In this life cycle study, we focused on the comparison of swine manure to synthetic fertilizer as nutrients for corn production in Iowa. Deep pit (DP) and anaerobic lagoon (AL) treatment systems were compared separately, and urea ammonium nitrate (UAN) was chosen as the representative synthetic fertilizer. The two functional units used were fertilization of 1000 kg of corn in a continuous corn system and fertilization of a crop yielding 1000 kg of corn and a crop yielding 298 kg of soybean in a 2-yr corn-soybean rotation. Iowa-specific versions of emission factors and energy use were used when available and compared with Intergovernmental Panel on Climate Change values. Manure was lower than synthetic fertilizer for abiotic depletion and about equal with respect to eutrophication. Synthetic fertilizer was lower than manure for global warming potential (GWP) and acidification. The choice of allocation method and life cycle boundary were important in understanding the context of these results. In the DP system, methane (CH 4) from housing was the largest contributor to the GWP, accounting for 60% of the total impact. When storage systems were compared, the DP system had 50% less GWP than the AL system. This comparison was due to reduction in CH 4 emissions from the storage system and conservation of nitrogen. Nitrous oxide emissions were the biggest contributor to the GWP of UAN fertilization and the second biggest contributor to the GWP of manure. Monte Carlo and scenario analyses were used to test the robustness of the results and sensitivity to methodology and important impact factors. The available crop-land and associated plant nutrient needs in Iowa was compared with manure production for the current hog population. On a state- or county-wide level, there was generally an excess of available land. On a farm level, there is often an excess of manure, which necessitates long-distance transport.
  • Authors:
    • Zhu, H. T.
    • Fang, X. X.
    • Pelton, M. P.
    • Blanco-Canqui, H.
    • Goddard, S.
    • Milner, M.
    • Yang, H. S.
    • Liska, A. J.
    • Suyker, A. E.
  • Source: Nature Climate Change
  • Volume: 4
  • Issue: 5
  • Year: 2014
  • Summary: Removal of corn residue for biofuels can decrease soil organic carbon (SOC; refs 1, 2) and increase CO 2 emissions because residue C in biofuels is oxidized to CO 2 at a faster rate than when added to soil. Net CO 2 emissions from residue removal are not adequately characterized in biofuel life cycle assessment (LCA; refs 6, 7, 8). Here we used a model to estimate CO 2 emissions from corn residue removal across the US Corn Belt at 580 million geospatial cells. To test the SOC model, we compared estimated daily CO 2 emissions from corn residue and soil with CO 2 emissions measured using eddy covariance, with 12% average error over nine years. The model estimated residue removal of 6 Mg per ha -1 yr -1 over five to ten years could decrease regional net SOC by an average of 0.47-0.66 Mg C ha -1 yr -1. These emissions add an average of 50-70 g CO 2 per megajoule of biofuel (range 30-90) and are insensitive to the fraction of residue removed. Unless lost C is replaced, life cycle emissions will probably exceed the US legislative mandate of 60% reduction in greenhouse gas (GHG) emissions compared with gasoline.
  • Authors:
    • Don, A.
    • Poeplau, C.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: Bioenergy has to meet increasing sustainability criteria in the EU putting conventional bioenergy crops under pressure. Alternatively, perennial bioenergy crops, such as Miscanthus, show higher greenhouse gas savings with similarly high energy yields. In addition, Miscanthus plantations may sequester additional soil organic carbon (SOC) to mitigate climate change. As the land-use change in cropland to Miscanthus involves a C-3-C-4 vegetation change (VC), it is possible to determine the dynamic of Miscanthus-derived SOC (C-4 carbon) and of the old SOC (C-3 carbon) by the isotopic ratio of C-13 to C-12. We sampled six croplands and adjacent Miscanthus plantations exceeding the age of 10 years across Europe. We found a mean C-4 carbon sequestration rate of 0.78 +/- 0.19 Mg ha(-1) yr(-1), which increased with mean annual temperature. At three of six sites, we found a significant increase in C-3 carbon due to the application of organic fertilizers or difference in baseline SOC, which we define as non-VC-induced SOC changes. The Rothamsted Carbon Model was used to disentangle the decomposition of old C-3 carbon and the non-VC-induced C3 carbon changes. Subsequently, this method was applied to eight more sites from the literature, resulting in a climate-dependent VC-induced SOC sequestration rate (0.40 +/- 0.20 Mg ha(-1) yr(-1)), as a step toward a default SOC change function for Miscanthus plantations on former croplands in Europe. Furthermore, we conducted a SOC fractionation to assess qualitative SOC changes and the incorporation of C-4 carbon into the soil. Sixteen years after Miscanthus establishment, 68% of the particulate organic matter (POM) was Miscanthus-derived in 0-10 cm depth. POM was thus the fastest cycling SOC fraction with a C-4 carbon accumulation rate of 0.33 +/- 0.05 Mg ha(-1) yr(-1). Miscanthus-derived SOC also entered the NaOCl-resistant fraction, comprising 12% in 0-10 cm, which indicates that this fraction was not an inert SOC pool.
  • Authors:
    • Asam, Z.-u.-Z.
    • Zhang, W.
    • Li, D.
    • Xu, X.
    • Luo, Y.
    • Kumar, S.
    • Rafique, R.
  • Source: Global and Planetary Change
  • Volume: 118
  • Issue: July
  • Year: 2014
  • Summary: Greenhouse gas (GHG) emissions play an important role in regulating the Earth surface temperature. GHG emissions from soils are sensitive to climate change and land management practices. According to general circulation model (GCM) predictions, the Earth will experience a combination of increased temperature and altered precipitation regimes which may result in an increase or a decrease of GHG exchange. The effect of climate change on GHG emissions can be examined through both experiments and by applying process-based models, which have become more popular. The performance of those models can be improved significantly by appropriate calibration procedures. The objectives of this study are to: (i) calibrate the DAYCENT model using advance parameter estimation (PEST) software and to (ii) examine simulated GHG dynamics at daily and seasonal time-scales under a climate change scenario of increased temperature (2 degrees C) and a precipitation regime change where 40% of precipitation during the dry season was redistributed to the wet season. The algorithmic calibration improved the model performance by reducing the sum of weighted squared residual differences by up to 223% (decreased from 1635 to 505 g N2O-N ha(-1) d(-1)) for N2O and 22% (decreased from 623 to 507% WFPS) for water filled pore space (WFPS) simulation results. In the altered climate scenario, total N2O and CO2 fluxes decreased by 9% (from 231 to 2.10 kg N2O-N ha(-1) yr(-1)) and 38% (from 1134.08 to 699.56 kg CO2 ha-1 yr-1) respectively, whereas CH4 fluxes increased by 10% (from 1.62 to 1.80 kg CH4 ha-1 yr-1). Our results show a larger impact of altered climate on CO2 as compared to N2O and CH4 emissions. The main difference in all GHG emissions was observed in summer period due to drought conditions created by reduced precipitation and increased temperatures. However, the GHG dynamics can also be attributed to no-till practices which play an important role in changing the soil moisture conditions for aerobic and anaerobic microsites. These results are based on a process-based model, therefore, we suggest performing experimental studies to examine the GHG emissions under increased temperature and especially under altered precipitation regimes. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Kludze, H.
    • McDonald,I.
    • Dadfar, H.
    • MacLean, H. L.
    • Dias, G.
    • Deen, B.
    • Sanscartier, D.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: Replacement of fossil fuels with sustainably produced biomass crops for energy purposes has the potential to make progress in addressing climate change concerns, nonrenewable resource use, and energy security. The perennial grass Miscanthus is a dedicated energy crop candidate being field tested in Ontario, Canada, and elsewhere. Miscanthus could potentially be grown in areas of the province that differ substantially in terms of agricultural land class, environmental factors and current land use. These differences could significantly affect Miscanthus yields, input requirements, production practices, and the types of crops being displaced by Miscanthus establishment. This study assesses implications on life cycle greenhouse gas (GHG) emissions of these differences through evaluating five Miscanthus production scenarios within the Ontario context. Emissions associated with electricity generation with Miscanthus pellets in a hypothetically retrofitted coal generating station are examined. Indirect land use change impacts are not quantified but are discussed. The net life cycle emissions for Miscanthus production varied greatly among scenarios (-90-170 kg CO(2)eq per oven dry tonne of Miscanthus bales at the farm gate). In some cases, the carbon stock dynamics of the agricultural system offset the combined emissions of all other life cycle stages (i.e., production, harvest, transport, and processing of biomass). Yield and soil C of the displaced agricultural systems are key parameters affecting emissions. The systems with the highest potential to provide reductions in GHG emissions are those with high yields, or systems established on land with low soil carbon. All scenarios have substantially lower life cycle emissions (-20-190 g CO(2)eq kWh(-1)) compared with coal-generated electricity (1130 g CO(2)eq kWh(-1)). Policy development should consider the implication of land class, environmental factors, and current land use on Miscanthus production.
  • Authors:
    • Phillips, R.
    • Savage, K.
    • Davidson, E.
  • Source: Biogeosciences
  • Volume: 11
  • Issue: 10
  • Year: 2014
  • Summary: Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases (GHGs). Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three GHGs. Although technologies for high-frequency, precise measurements of CO2 have been available for years, methods for measuring soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. A previously developed automated chamber system for measuring CO2 flux from soils was configured to run in line with a new quantum cascade laser (QCLAS) instrument that measures N2O and CH4. Here we present data from a forested wetland in Maine and an agricultural field in North Dakota, which provided examples of both net uptake and production for N2O and CH4. The objective was to provide a range of conditions in which to run the new system and to compare results to a traditional manual static-chamber method. The high-precision and more-than-10-times-lower minimum detectable flux of the QCLAS system, compared to the manual system, provided confidence in measurements of small N2O uptake in the forested wetland. At the agricultural field, the greatest difference between the automated and manual sampling systems came from the effect of the relatively infrequent manual sampling of the high spatial variation, or "hot spots", in GHG fluxes. Hot spots greatly influenced the seasonal estimates, particularly for N2O, over one 74-day alfalfa crop cycle. The high temporal frequency of the automated system clearly characterized the transient response of all three GHGs to precipitation and demonstrated a clear diel pattern related to temperature for GHGs. A combination of high-frequency automated and spatially distributed chambers would be ideal for characterizing hot spots and "hot moments" of GHG fluxes.
  • Authors:
    • Malins, C. J.
    • Searle, S. Y.
  • Source: Biomass and Bioenergy
  • Volume: 65
  • Issue: June
  • Year: 2014
  • Summary: Expectations are high for energy crops. Government policies in the United States and Europe are increasingly supporting biofuel and heat and power from cellulose, and biomass is touted as a partial solution to energy security and greenhouse gas mitigation. Here, we review the literature for yields of 5 major potential energy crops: Miscanthus spp., Panicum virgatum (switch grass), Populus spp. (poplar), Salix spp. (willow), and Eucalyptus spp. Very high yields have been achieved for each of these types of energy crops, up to 40 t ha(-1) y(-1) in small, intensively managed trials. But yields are significantly lower in semi-commercial scale trials, due to biomass losses with drying, harvesting inefficiency under real world conditions, and edge effects in small plots. To avoid competition with food, energy crops should be grown on non-agricultural land, which also lowers yields. While there is potential for yield improvement for each of these crops through further research and breeding programs, for several reasons the rate of yield increase is likely to be slower than historically has been achieved for cereals; these include relatively low investment, long breeding periods, low yield response of perennial grasses to fertilizer, and inapplicability of manipulating the harvest index. Miscanthus x giganteus faces particular challenges as it is a sterile hybrid. Moderate and realistic expectations for the current and future performance of energy crops are vital to understanding the likely cost and the potential of large-scale production. (c) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Mihalache, M.
    • Fintineru, G.
    • Stan, V.
  • Source: Notulae Botanicae Horti Agrobotanici Cluj-Napoca
  • Volume: 42
  • Issue: 1
  • Year: 2014
  • Summary: Burning crop residues is frequently used by Romanian land users to clean agricultural fields after crop harvest for ease in postharvest soil tillage. Huge amounts of crop residues biomass, on very large areas, were burned in Romania in the last twenty years, as compared to other countries. There are several reasons (e.g. the lack of equipment to gather the crop residues and to transport and store them, the diminishing of the livestock after 1990, the absence of other alternatives, especially in the 1990s, but also the lack of information regarding the good practices) that are evocated to support the use of this method. However, this method is not a sustainable one since it can cause many environmental damages, especially related to soil properties (physical, chemical and biological), greenhouse gas emission and crop yields. Contrary to the above stated, crop residues' addition to the soil may restore damaged soil structure, improve aggregate stability, soil water retention, soil fertility, increase total organic carbon (TOC) and total nitrogen (TN) etc. The purpose of this paper is to make a multicriteria analyze of the effects of crop residue management on the soil, agricultural productivity and environment. At the same time, the use of crop residues biomass as a source of energy is presented as an alternative, given its potential ability to offset fossil fuels and reduce CO 2 emissions.
  • Authors:
    • Sakalauskas, A.
    • Avizienyte, D.
    • Romaneckas, K.
    • Masilionyte, L.
    • Buragiene, S.
    • Sarauskis, E.
  • Source: Energy
  • Volume: 69
  • Issue: SI
  • Year: 2014
  • Summary: To achieve energy independence, Lithuania and other Baltic countries are searching for new ways to produce energy. Maize is a crop that is suitable for both food and forage, as well as for the production of bioenergy. The objective of this work was to assess the energy efficiency of maize cultivation technologies in different systems of reduced tillage. The experimental research and energy assessment was carried out for five different tillage systems: DP (deep ploughing), SP (), DC (deep cultivation), SC (shallow cultivation) and NT (no tillage). The assessment of the fuel inputs for these systems revealed that the greatest amount of diesel fuel (67.2 l ha -1) was used in the traditional DP system. The reduced tillage systems required 12-58% less fuel. Lower fuel consumption reduces the costs of technological operations and reduces CO 2 emissions, which are associated with the greenhouse effect. The agricultural machinery used in reduced tillage technologies emits 107-223 kg ha -1 of CO 2 gas into the environment, whereas DP emits 253 kg ha -1 of CO 2. The energy analysis conducted in this study showed that the greatest total energy input (approximately 18.1 GJ ha -1) was associated with the conventional deep-ploughing tillage technology. The energy inputs associated with the reduced-tillage technologies, namely SP, DC and SC, ranged from 17.1 to 17.6 GJ ha -1. The lowest energy input (16.2 GJ ha -1) was associated with the NT technology. Energy efficiency ratios for the various technologies were calculated as a function of the yield of maize grain and biomass. The best energy balance and the highest energy efficiency ratio (14.0) in maize cultivation was achieved with the NT technology. The energy efficiency ratios for DP, SP, DC and SC were 12.4, 13.4, 11.3 and 12.0, respectively.
  • Authors:
    • Davidson, E.
    • Phillips, R.
    • Savage, K.
  • Source: Biosciences
  • Volume: 11
  • Issue: 10
  • Year: 2014
  • Summary: Carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O) are the most important anthropogenic greenhouse gases (GHGs). Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three GHGs. Although technologies for high-frequency, precise measurements of CO 2 have been available for years, methods for measuring soil fluxes of CH 4 and N 2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. A previously developed automated chamber system for measuring CO 2 flux from soils was configured to run in line with a new quantum cascade laser (QCLAS) instrument that measures N 2O and CH 4. Here we present data from a forested wetland in Maine and an agricultural field in North Dakota, which provided examples of both net uptake and production for N 2O and CH 4. The objective was to provide a range of conditions in which to run the new system and to compare results to a traditional manual static-chamber method. The high-precision and more-than-10-times-lower minimum detectable flux of the QCLAS system, compared to the manual system, provided confidence in measurements of small N 2O uptake in the forested wetland. At the agricultural field, the greatest difference between the automated and manual sampling systems came from the effect of the relatively infrequent manual sampling of the high spatial variation, or "hot spots", in GHG fluxes. Hot spots greatly influenced the seasonal estimates, particularly for N 2O, over one 74-day alfalfa crop cycle. The high temporal frequency of the automated system clearly characterized the transient response of all three GHGs to precipitation and demonstrated a clear diel pattern related to temperature for GHGs. A combination of high-frequency automated and spatially distributed chambers would be ideal for characterizing hot spots and "hot moments" of GHG fluxes.