• Authors:
    • Pereira,E. I. P.
    • Suddick,E. C.
    • Mansour,I.
    • Mukome,F. N. D.
    • Parikh,S. J.
    • Scow,K.
    • Six,J.
  • Source: Biology and Fertility of Soils
  • Volume: 51
  • Issue: 5
  • Year: 2015
  • Summary: We investigated the effect of biochar type on plant performance and soil nitrogen (N) transformations in mesocosms representing an organic lettuce ( Lactuca sativa) production system. Five biochar materials were added to a silt loam soil: Douglas fir wood pyrolyzed at 410°C (W410), Douglas fir wood pyrolyzed at 510°C (W510), pine chip pyrolyzed at 550°C (PC), hogwaste wood pyrolyzed between 600 and 700°C (SWC), and walnut shell gasified at 900°C (WS). Soil pH and cation exchange capacity were significantly increased by WS biochar only. Gross mineralization increased in response to biochar materials with high H/C ratio (i.e., W410, W510, and SWC), which can be favorable for organic farming systems challenged by insufficient N mineralization during plant growth. Net nitrification was increased by W510, PC, and WS without correlating with the abundance of ammonia oxidizing gene ( amoA). Increases in N transformation rates did not translate into increases in plant productivity or leaf N content. WS biochar increased the abundance of amoA and nitrite reductase gene ( nirK), while SWC biochar decreased the abundance of amoA and nitrous oxide gene ( nosZ). Decreases in N 2O emissions were only observed in soil amended with W510 for 3 days out of the 42-day growing season without affecting total cumulative N 2O fluxes. This suggests that effects of biochar on decreasing N 2O emissions may be transient, which compromise biochar's potential to be used as a N 2O mitigation strategy in organic systems. Overall, our results confirm that different biochar materials can distinctively affect soil properties and N turnover.
  • Authors:
    • Cichorowski,G.
    • Joa,B.
    • Hottenroth,H.
    • Schmidt,M.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 20
  • Issue: 4
  • Year: 2015
  • Summary: Purpose: Following water, tea is the second most consumed drink worldwide and has the peculiarity that not only its production but especially its preparation can be associated with considerable greenhouse gas (GHG) emissions. The aims of this study were to calculate the cradle-to-gate and cradle-to-grave product carbon footprint (PCF) of Darjeeling tea and to identify potentials to reduce GHG emissions along its life cycle. Therefore, various options for action and their impact on the PCF were modeled by using a scenario analysis. Methods: To assess the PCF of Darjeeling tea, the method based on ISO/TS 14067 was used with some limitations. Besides one base scenario, alternative cradle-to-gate scenarios and different use profiles were modeled. The results were split in a cradle-to-gate and a cradle-to-grave perspective. For the cradle-to-gate phase a functional unit of one kilogram loose black Darjeeling tea was chosen, whereas for the cradle-to-grave phase one liter black Darjeeling tea that is prepared and ready to drink in Germany was seen as appropriate functional unit. Primary data for the present study has been collected from local farmers, manufacturers, and agents in Darjeeling, Kolkata, and Rotterdam. For secondary data, the database ecoinvent 2.2 was mainly used. Results and discussion: The cradle-to-gate PCF of 1 kg Darjeeling tea is between 7.1 and 25.3 kg CO 2e depending on the cultivation method, energy sources used, or mode of transportation. The cradle-to-grave PCF for 1 l organic Darjeeling tea is about 0.15 kg CO 2e. The largest share, 51%, makes up the use phase, which is clearly dominated by the boiling of water. The variety of possible use profiles yields results of great breadth. It shows that the life cycle of organic Darjeeling tea transported by ship, depending on the preparation variants can cause emissions from 0.12 to 0.51 kg CO 2e/l tea. Conclusions: The main reduction potentials for GHG emissions were identified in the process of water boiling, the intercontinental transport mode, and the cultivation method. Since the climate impact of tea strongly depends on the way in which it is prepared, the consumer has a decisive influence on the PCF. Therefore, in order to make a reliable statement about the climate performance of consumer goods such as tea, the whole life cycle must be considered.
  • Authors:
    • Creutzig,Felix
    • Ravindranath,N. H.
    • Berndes,Goran
    • Bolwig,Simon
    • Bright,Ryan
    • Cherubini,Francesco
    • Chum,Helena
    • Corbera,Esteve
    • Delucchi,Mark
    • Faaij,Andre
    • Fargione,Joseph
    • Haberl,Helmut
    • Heath,Garvin
    • Lucon,Oswaldo
    • Plevin,Richard
    • Popp,Alexander
    • Robledo-Abad,Carmenza
    • Rose,Steven
    • Smith,Pete
    • Stromman,Anders
    • Suh,Sangwon
    • Masera,Omar
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 5
  • Year: 2015
  • Summary: Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land-use and energy experts, land-use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life-cycle assessment experts. We summarize technological options, outline the state-of-the-art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end-use efficiency, improved land carbon-stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small-scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100EJ: high agreement; 100-300EJ: medium agreement; above 300EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245EJyr(-1) to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large-scale deployment (>200EJ), together with BECCS, could help to keep global warming below 2 degrees degrees of preindustrial levels; but such high deployment of land-intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.
  • Authors:
    • Openshaw,K.
  • Source: Advances in Building Energy Research
  • Volume: 4
  • Issue: 1
  • Year: 2015
  • Summary: The energy value of biomass depends on its carbon and hydrogen contents, its non-combustibles and the water content. For unprocessed biomass, namely wood, residues and dung, the C and H contents are more or less constant for each group of fuels on an ash-free and moisture-free basis. Using this information, a method is given to calculate the low heat values of unprocessed biomass at different moisture and ash contents. While most wood species have an ash content of about 1%, the ash content of crop residues vary according to species from about 1 to 20%. Similarly dung varies from about 20 to 30% ash. However, moisture is the most important factor when determining the available energy. Tables and graphs are given of unprocessed biomass energy at different ash and moisture contents. Charcoal is the most important processed biomass. A method to calculate the energy value of charcoal from biomass is given. The energy values of other forms of biomass are also given. Finally, the role of biomass as a renewable energy (RE) source as well as it being an important tool to capture and reduce greenhouses gases (GHG) is discussed.
  • Authors:
    • He, X.
    • Guan, Q.
    • Lu, X.
    • Lu, M.
    • Wu, H.
  • Source: Biology Article
  • Volume: 88
  • Year: 2015
  • Summary: Soil fauna can significantly affect soil CO2 and N2O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO2 and N2O emissions under two faunal densities. Earthworms significantly enhanced soil CO2 and N2O emissions, while mesofauna only increased N2O emissions. Soil CO2 and N2O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO2 and N2O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO2 and N2O emissions where they coexist with soil mesofauna. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Blanco-Canqui,H.
    • Shaver,T. M.
    • Lindquist,J. L.
    • Shapiro,C. A.
    • Elmore,R. W.
    • Francis,C. A.
    • Hergert,G. W.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops (CCs) can provide multiple soil, agricultural production, and environmental benefits. However, a better understanding of such potential ecosystem services is needed. We summarized the current state of knowledge of CC effects on soil C stocks, soil erosion, physical properties, soil water, nutrients, microbial properties, weed control, crop yields, expanded uses, and economics and highlighted research needs. Our review indicates that CCs are multifunctional. Cover crops increase soil organic C stocks (0.1-1 Mg ha -1 yr -1) with the magnitude depending on biomass amount, years in CCs, and initial soil C level. Runoff loss can decrease by up to 80% and sediment loss from 40 to 96% with CCs. Wind erosion potential also decreases with CCs, but studies are few. Cover crops alleviate soil compaction, improve soil structural and hydraulic properties, moderate soil temperature, improve microbial properties, recycle nutrients, and suppress weeds. Cover crops increase or have no effect on crop yields but reduce yields in water-limited regions by reducing available water for the subsequent crops. The few available studies indicate that grazing and haying of CCs do not adversely affect soil and crop production, which suggests that CC biomass removal for livestock or biofuel production can be another benefit from CCs. Overall, CCs provide numerous ecosystem services (i.e., soil, crop-livestock systems, and environment), although the magnitude of benefits is highly site specific. More research data are needed on the (i) multi-functionality of CCs for different climates and management scenarios and (ii) short- and long-term economic return from CCs.
  • Authors:
    • Tanaka, D.
    • Nichols, K.
    • Schmer, M.
    • Archer, D.
    • Hendrickson, J.
    • Liebig, M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops can expand ecosystem services, though sound management recommendations for their use within semiarid cropping systems is currently constrained by a lack of information. This study was conducted to determine agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil attributes. Short-term effects of late-summer seeded cover crops on soil water, available N, near-surface soil quality, and residue cover were investigated during three consecutive years on the Area IV Soil Conservation Districts Research Farm near Mandan, ND. Mean aboveground cover crop biomass was highly variable across years (1430, 96, and 937 kg ha -1 in 2008, 2009, and 2010, respectively), and was strongly affected by precipitation received within 14 d following cover crop seeding. During years with appreciable biomass production (2008 and 2010), cover crops significantly reduced available N in the 0.9-m depth the following spring ( P=0.0291 and 0.0464, respectively). Cover crop effects on soil water were subtle, and no differences in soil water were found between cover crop treatments and a no cover crop control before seeding cash crops the following spring. Late-summer seeded cover crops did not affect near-surface soil properties or soil coverage by residue. Soil responses to late-summer seeded cover crops did not differ between cover crop mixtures and monocultures. Late-summer seeded cover crops may enhance ecosystem services provided by semiarid cropping systems through biomass production and N conservation, though achieving these benefits in a consistent manner appears dependent on timely precipitation following cover crop seeding.
  • Authors:
    • Stinner, P.
  • Source: Energy, Sustainability and Society
  • Volume: 5
  • Issue: 4
  • Year: 2015
  • Summary: Background: Energy crops are of considerable importance for biogas production, especially in Germany. The main energy crops for that purpose are corn silage, grass silage, whole crop grain silage and other non-legume crops. The reason for preferring these crops is their high yield, which not only results in high yields of biogas per hectare but also in a high mitigation of greenhouse gases in the course of replacing fossil energy. This article aims to show an additional effect exerted on energy yield and mitigation of greenhouse gases by the use of legume energy crops. The symbiotic nitrogen fixation (SNF) of legumes compensates inorganic N fertilizer in conventional farms, if the digestate is applied as a fertilizer to the non-legume cash crops. The production of chemical N fertilizer is very energy intensive and leads to emissions of greenhouse gases from fossil energy consumption and from nitrous oxide generation. So, the creation of an effective organic fertilizer with nitrogen from biological N 2 fixation is a further energy add-on effect to the reduction of greenhouse gas emissions. Methods: For this article, data with regard to the SNF of legumes obtained in field experiments at the research station at Gladbacherhof (University of Giessen) from 2002 to 2005 were re-calculated and compared with data concerning energy need and greenhouse gas emissions in the process of producing mineral nitrogen fertilizer. In addition to the possible methane yield of these substrates, the saving in energy and greenhouse gas emissions by substituting mineral fertilizers is shown. Results: As a result, the possible replacement of primary energy by SNF of clover grass leys is calculated to be approximately less than 6.4 MWh ha -1 a -1. This is a yield that is reached in addition to the methane production, i.e. a possible reduction of greenhouse gas emissions through SNF per hectare of clover grass leys of more than 2 t CO 2 equivalents ha -1 a -1 can be achieved. Conclusions: Based on these results, it can be recommended to evaluate energy crops in a more holistic way. For legumes, the effect of SNF needs to be included into the energy and greenhouse balance.
  • Authors:
    • Colnenne-David,Caroline
    • Dore,Thierry
  • Source: Renewable Agriculture and Food Systems
  • Volume: 30
  • Issue: 6
  • Year: 2015
  • Summary: Agriculture must face a number of very pressing environmental issues. We used the prototyping method to design three innovative cropping systems, each satisfying three ambitious goals simultaneously: (1) overcoming a major environmental constraint, which represents a major break regarding objectives to be reached in current cropping systems (differing between systems: a ban on all pesticides but with chemical nitrogen (N) fertilizer permitted; reducing fossil energy consumption by 50%; or decreasing greenhouse gas (GHG) emissions by 50%), (2) meeting a wide range of environmental criteria and (3) maximizing yields, given the major constraint and environmental targets. A fourth cropping system was designed, in which the environmental and yield targets were achieved with no major constraint (the productive high environmental performance cropping system (PHEP) system). The performances of these innovative cropping systems were compared to a conventional system in the Ile-de-France region. We used a three-step prototyping method: (1) new cropping systems were designed on the basis of scientific and expert knowledge, (2) these system prototypes were assessed with tools and a model (ex ante assessment) adjusted to the set of constraints and targets, with optimization by an iterative process until the criteria were satisfied and (3) evaluation in a long-term field experiment (ex post assessment), which is currently underway. We describe only the first two steps here, together with the results of the prototypes assessment with tools and a model. The pesticide, energy and GHG constraints were fulfilled. All these innovative systems satisfied environmental criteria in terms of nitrogen and phosphorus management, pesticide use, energy consumption and crop diversity. For the pesticide-free system, the soil organic matter indicator was lower than expected due to frequent plowing (every 2 years) and yields were 20-50% lower than for the PHEP system, depending on the crop considered. We focus our discussions on the design methodology and the availability of scientific knowledge and tools for projects of this type.
  • Authors:
    • Crittenden,S. J.
    • Poot,N.
    • Heinen,M.
    • van Balen,D. J. M.
    • Pulleman,M. M.
  • Source: Soil and Tillage Research
  • Volume: 154
  • Year: 2015
  • Summary: Reduced tillage can improve soil physical quality relative to mouldboard ploughing by lessening soil disturbance, leaving organic matter at the soil surface, and stimulating soil biological activity. In organic farming, continuous ploughing may negate benefits to soil structure and function from increased use of manures and more diverse crop rotations, which are particularly important components of organic farming. The current study examined soil physical quality (i.e., properties and functioning) of a 4-year old reduced tillage system under organic and conventional farming with crop rotations that included root crops. Reduced tillage was compared to conventional mouldboard ploughing (MP) in 2 organic fields at different points of the same crop rotation (Org A and Org B) and 1 conventional field (Conv A). Reduced tillage consisted of non-inversion tillage (NIT) to 18-23. cm depth whereas MP was characterised by annual mouldboard ploughing to 23-25. cm depth. NIT improved soil water retention in Org B but had no effect in Org A. NIT increased soil aggregate stability at 10-20. cm depth compared to MP in all fields, and additionally at 0-10. cm in Conv A. Penetration resistance was higher in NIT in all fields. Furthermore, soil organic matter content was higher in NIT than MP at 0-10. cm depth in all fields and at 10-20. cm in Org B and Conv A. NIT increased carbon stocks in Org B but not in Org A. NIT statistically increased crop yields in spring wheat/faba bean mixture in Org A, and there was no yield penalty from NIT in Org B spring wheat nor Conv A sugar beet. In contrast, field-saturated hydraulic conductivity in all fields in autumn was lower in NIT. Differences in crop (i.e., phase of rotation) and associated organic inputs between Org A and B likely accounted for the differences in effects of tillage system. Overall, the NIT system improved or imposed no penalty on soil physical quality (except field-saturated hydraulic conductivity) and improved or imposed no penalty on crop yields and could therefore be considered as a viable alternative for farmers. © 2015 Elsevier B.V..